Today's Message Index:
----------------------
1. 03:56 AM - Re: M-IIIC Drivers in Iowa (PATRICK LADD)
2. 04:13 AM - Re: M-IIIC Drivers in Iowa (Chuck Stonex)
3. 04:14 AM - Re: Fw: Quiet Landings (PATRICK LADD)
4. 04:59 AM - Re: Old thread- Trips (N27SB@aol.com)
5. 05:22 AM - tom (Jimmy)
6. 05:33 AM - Re: tom o's recommended tbo for 447 (John Hauck)
7. 06:55 AM - Re: Fw: Quiet Landings (JIM HEFNER)
8. 07:24 AM - Re: Quiet Landings/Practice Dead Stick (Steve Kroll)
9. 07:34 AM - Re: tom o's recommended tbo for 447 (Jeremy Casey)
10. 07:41 AM - Re: Quiet Landings/Practice Dead Stick (robert bean)
11. 08:02 AM - Re: Quiet Landings/Practice Dead Stick (John Hauck)
12. 08:29 AM - Re: Quiet Landings/Practice Dead Stick (Rusty)
13. 08:29 AM - Re: Quiet Landings/Practice Dead Stick (N27SB@aol.com)
14. 08:49 AM - Re: Quiet Landings/Practice Dead Stick (JIM HEFNER)
15. 09:13 AM - Re: Quiet Landings/Practice Dead Stick (Ed Chmielewski)
16. 09:14 AM - Re: Quiet Landings/Practice Dead Stick (Steve Garvelink)
17. 09:28 AM - Re: Quiet Landings/Practice Dead Stick (John Hauck)
18. 09:38 AM - Re: Quiet Landings/Practice Dead Stick (John Hauck)
19. 09:51 AM - Re: Quiet Landings/Practice Dead Stick (Rusty)
20. 10:11 AM - Re: Quiet Landings/Practice Dead Stick (John Hauck)
21. 10:46 AM - Re: Re: Two Stroke Oil - personal ruin (Denny Rowe)
22. 10:52 AM - Re: tom (Denny Rowe)
23. 10:54 AM - Re: Quiet Landings/Practice Dead Stick (Chuck Stonex)
24. 11:07 AM - Re: Quiet Landings/Practice Dead Stick (Richard & Martha Neilsen)
25. 11:18 AM - 912S Rpm question (Denny Rowe)
26. 11:27 AM - Re: Quiet Landings/Practice Dead Stick (Christopher Armstrong)
27. 11:43 AM - Re: 912S Rpm question (John Hauck)
28. 12:04 PM - Re: Quiet Landings/Practice Dead Stick (Rusty)
29. 01:11 PM - Re: Quiet Landings/Practice Dead Stick (Steve Garvelink)
30. 01:21 PM - Re: Quiet Landings/Practice Dead Stick (Richard Pike)
31. 01:38 PM - Re: Quiet Landings/Practice Dead Stick (John Hauck)
32. 02:11 PM - Re: Old thread- Trips (DCulver701@AOL.com)
33. 02:29 PM - Quiet landings (flykolb)
34. 04:58 PM - Re: M-IIIC Drivers in Iowa (woody)
35. 06:30 PM - Re: M-IIIC Drivers in Iowa (Billie Futrell)
36. 06:31 PM - Re: M-IIIC Drivers in Iowa (Chuck Stonex)
37. 08:52 PM - Re: Torsional Resonance & Drive Trains (Richard Swiderski)
38. 09:01 PM - Long Sitting Rotax 582 (Kolbdriver)
39. 09:10 PM - Re: M-IIIC Drivers in Iowa (Chuck Stonex)
40. 09:10 PM - Re: VW reduction drive (Richard Swiderski)
41. 09:20 PM - Re: Long Sitting Rotax 582 (Larry Bourne)
Message 1
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| Subject: | Re: M-IIIC Drivers in Iowa |
--> Kolb-List message posted by: "PATRICK LADD" <pj.ladd@btinternet.com>
He didn't panic just remembered what I had told him>>
Chuck,
What did you tell him?. I am about to change from Challenger to Kolb and
have not flown a tail dragger since I sold the Thruster many years ago.
NB. The Challenger is not half as bad as this lot make out :-)
Pat
--
Message 2
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| Subject: | Re: M-IIIC Drivers in Iowa |
--> Kolb-List message posted by: "Chuck Stonex" <cstonex@msn.com>
Pat
I think you might of direct this to the wrong guy but your right about one
thing, Challenger is a good plane. Golden Circle Air (T Bird) was 20 miles
away until they sold it last week and it moved to Liberty Iowa and everyone
flys T Bird here. It was a great plane for training but I do not want one in
my hanger. I'm just hoping I can find someone to help me get some time in
this M-III I am hoping to buy next week.
Chuck S
--> Kolb-List message posted by: "PATRICK LADD" <pj.ladd@btinternet.com>
He didn't panic just remembered what I had told him>>
Chuck,
What did you tell him?. I am about to change from Challenger to Kolb and
have not flown a tail dragger since I sold the Thruster many years ago.
NB. The Challenger is not half as bad as this lot make out :-)
Pat
--
Message 3
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| Subject: | Re: Fw: Quiet Landings |
--> Kolb-List message posted by: "PATRICK LADD" <pj.ladd@btinternet.com>
Don't come up short!! >>
Hope I am not teaching granny to suck eggs here but if you line up your
expected landing point with something on your plane, top of instrument
panel, end of nose cone, whatever, and the expected landing point climbs
above your mark, YOU WILL UNDERSHOOT .
Do not try to keep the points in line as you will slowly raise your
nose, lose speed and stall. Trying to stretch your glide can kill you.
Conversely, if the landing point slides DOWN you will overshoot and should
drop on more flap, sideslip, fishtail or whatever to lose height.
Congratulations. I have never had the nerve to turn off the engine in flight
unless something had already gone wrong.
Cheers
Pat
--
Message 4
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| Subject: | Re: Old thread- Trips |
--> Kolb-List message posted by: N27SB@aol.com
In a message dated 7/20/2005 11:43:45 AM Eastern Standard Time,
DCulver701@aol.com writes:
> Our place is in Lake County, on lake Yale in Grand Island, Fl. Yes i
> would love to see your plane with the whole trailering process. I'll be
> sure to
> give you a shout on the list when we get back down to Fl. Probably be in
> Nov.
>
Dave, I finally got my DeLorme Atlas out and found Lake Yale. It is the
northern most large lake on the Mount Dora Chain of lakes. It is less than 5 miles
from my Dad's house. I just explored Lake Dora and Eustis last Week. I
noticed that Lake Yale has a boat ramp on the SE shore. That is really good in
Fla
for summer flying because it gives you a headwind taxi to the ramp. If the ramp
is wide enough you will have a perfect, free "Airport".
I think I will go check it out in the morning and do some flying.
Steve Boetto
FF #007/floats
do not archive
Message 5
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--> Kolb-List message posted by: "Jimmy" <jhankin@planters.net>
Either Wednesday or Thursday there was a post about engine overall and
maintenance seemly from Tom, listing the TBO of a 447 to be 600 hours and a
503 at a lower time.
Was this a past quote someone put on the site???????
Jimmy Hankinson
912-863-7384
Firefly 035
JYL (Sylvania)
Pegasus Field (Home)
2000 Feet X 100 Feet- Grass
Rocky Ford, Georgia
Do Not Archive
Message 6
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| Subject: | Re: tom o's recommended tbo for 447 |
--> Kolb-List message posted by: "John Hauck" <jhauck@elmore.rr.com>
and
| maintenance seemly from Tom, listing the TBO of a 447 to be 600
hours and a
| 503 at a lower time.
|
| Was this a past quote someone put on the site???????
|
| Jimmy Hankinson
Morning Jimmy H/All:
Yes. Possum pulled it out of his or Kolb's archives.
I understand these TBO times are numbers Tom Olenik would recommend
based on his experience repairing them, if he were the Rotax engineers
in charge.
Tom's numbers are similar to mine, reference the 912 series. Rotax
recommends 1,500 hour TBO. I believe my 912ULS will see much more
time than that before it is torn down. Don Huff has well over 2,000
hours on his 912UL and still going strong.
john h
Message 7
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| Subject: | Re: Fw: Quiet Landings |
--> Kolb-List message posted by: "JIM HEFNER" <hefner_jim@msn.com>
--> Kolb-List message posted by: "PATRICK LADD" <pj.ladd@btinternet.com<mailto:pj.ladd@btinternet.com?subjectRe: Fw: Quiet Landings&replyto200507221114.j6MBEYLx002064@mail.matronics.com>>
Don't come up short!! >>
Hope I am not teaching granny to suck eggs here....
Pat, not at all. Good points. I learned that early on by doing spot landings
at idle and as I mentioned here, my next step will be to do spot landing practice
with dead stick. You really get a much better feel for the plane when you
practice these things. Emergencies can be turned into non events with practice
and some luck that there is a good place to aim for when it does quit. My
BRS is there for that case. Hope never to try it out though.
Go ahead and shut it off sometime... it's the first step to practicing something
really useful and turns out to be quite a bit of fun, once you get past that
first mental hurdle. Like Roger mentioned in his post, going up higher will
be even more fun.
Saw John H's post that someone said they would never practice this... glad you
agree this is important to practice. Each to his own, but I sure want to be
well practiced at this one for when the real thing happens.
I'm not suggesting this for brand new fliers though. Get 100 hrs under your belt,
know your plane well, practice lots of idle landings and spot landings first,
then turning the engine off is not that much different. You already know
how your plane handles well by then and it only performs better when you shut
it off, so there are no big surprises. To me this is a key part of learning to
fly safely and I was starting to feel guilty because I had put it off for so
long.
Hope more people will give it a try.
Take care,
Jim Hefner
Tucson, AZ
FF#022 215 hrs
Do Not Archive
Message 8
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| Subject: | Re: Quiet Landings/Practice Dead Stick |
--> Kolb-List message posted by: Steve Kroll <muso2080@yahoo.com>
<<<<<I forget who wrote this on the Kolb List, but it was to the effect
that they would not take a chance practicing a dead stick landing,
possibly breaking the airplane. >>>>>>
It was me that said that John but you misunderstood. I had already had an unannounced
engine out and subsequent forced landing and it seemed to me at the time
it happened that the glide was steeper with the engine off.
I still don't like the idea of practicing engine outs with the ignition off. If
you misjudge the distance, you can thump the airplane..... or worse, and I believe
(if I survived) I would feel really stupid if I wrecked my bird while practicing
dead stick with an engine that would still run. There have been many
times that I have adjusted throttle during a glide to landing because I misjudged
the distance. What's the old saying in flying circles...."there are old
pilots and there are bold pilots but, there are no old, bold pilots".
Steve
Mk2 503
do not archive
---------------------------------
Message 9
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| Subject: | tom o's recommended tbo for 447 |
--> Kolb-List message posted by: "Jeremy Casey" <n79rt@kilocharlie.us>
Don Huff has well over 2,000
hours on his 912UL and still going strong.
john h
<snip>
Last time I ask him, he was over 2300 hours...and his is certainly the
hardest run 912 on the planet...full throttle, climb to 9-10K...leave
the throttle right where it was and cruise 2-2.5 hours, idle power push
the nose over decent (or spin it to get down quick) shut off for more
gas...I always shake my head...
Jeremy
Message 10
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| Subject: | Re: Quiet Landings/Practice Dead Stick |
--> Kolb-List message posted by: robert bean <slyck@frontiernet.net>
I've had a couple flameouts in my life (airplane that is) both
induction icing
during brutal weather. Both times no dents. -Still have never
deliberately
shut it down in the pattern. Guess I would want a nice BIG runway
beneath.
If you get a little slow 20 ft off the ground you might have a problem
that
the throttle would ordinarily solve. My garbage can panel has ONE
switch
so I won't get confused. Start/stop.
BB do not archive
On 22, Jul 2005, at 10:23 AM, Steve Kroll wrote:
> --> Kolb-List message posted by: Steve Kroll <muso2080@yahoo.com>
>
> <<<<<I forget who wrote this on the Kolb List, but it was to the effect
> that they would not take a chance practicing a dead stick
> landing,
> possibly breaking the airplane. >>>>>>
>
> It was me that said that John but you misunderstood. I had already
> had an unannounced engine out and subsequent forced landing and it
> seemed to me at the time it happened that the glide was steeper with
> the engine off.
>
> I still don't like the idea of practicing engine outs with the
> ignition off. If you misjudge the distance, you can thump the
> airplane..... or worse, and I believe (if I survived) I would feel
> really stupid if I wrecked my bird while practicing dead stick with an
> engine that would still run. There have been many times that I have
> adjusted throttle during a glide to landing because I misjudged the
> distance. What's the old saying in flying circles...."there are old
> pilots and there are bold pilots but, there are no old, bold pilots".
>
> Steve
> Mk2 503
>
> do not archive
>
>
> ---------------------------------
>
>
Message 11
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| Subject: | Re: Quiet Landings/Practice Dead Stick |
--> Kolb-List message posted by: "John Hauck" <jhauck@elmore.rr.com>
ignition off. If you misjudge the distance, you can thump the
airplane..... or worse, and I believe (if I survived) I would feel
really stupid if I wrecked my bird while practicing dead stick with an
engine that would still run.
There have been many times that I have adjusted throttle during a
glide to landing because I misjudged the distance. What's the old
saying in flying circles...."there are old pilots and there are bold
pilots but, there are no old, bold pilots".
|
| Steve
Hi Steve K/Gang:
I don't agree with your philosophy, but that does not matter.
Personally, I would rather take a chance of missing a 3,000 ft strip
and learn how to fly my MKIII engine out than do it your way.
I don't have any old sayings for you, but the example you used, above,
doesn't fit pilots that do realistic training in the eventuality that
the engine stops unannounced.
Again, to each his own.
john h
MKIII
Message 12
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| Subject: | Quiet Landings/Practice Dead Stick |
--> Kolb-List message posted by: "Rusty" <13brv3c@bellsouth.net>
Personally, I would rather take a chance of missing a 3,000 ft strip
and learn how to fly my MKIII engine out than do it your way.
I don't have any old sayings for you, but the example you used, above,
doesn't fit pilots that do realistic training in the eventuality that
the engine stops unannounced.
-------------------
Hi John,
If you have exactly the right circumstances to practice this, it would be
fun, and you'd gain valuable experience. No doubt about it. However, miss
that runway and end up in someone's yard, and you'll be hung out to dry for
being reckless. Imagine having to convince an average jury that turning off
the engine in your plane was a reasonable thing to do. Might as well just
plead guilty. You could still make a case that this slight risk is worth
taking, considering the knowledge that could be gained.
I would never have considered shutting off the engine of a plane before I
actually had an emergency situation. Now that I've logged a few minutes of
(flaming) glider time, I'm actually more open to doing some real glide
testing. Deep down, I think we don't really believe the plane will fly
without power until we see it first hand, then it's not as scary as it used
to be.
Cheers,
Rusty (starting to think SS-022 is a hurricane magnet)
Message 13
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| Subject: | Re: Quiet Landings/Practice Dead Stick |
--> Kolb-List message posted by: N27SB@aol.com
In a message dated 7/22/05 10:03:16 AM Central Daylight Time,
jhauck@elmore.rr.com writes:
> ignition off. If you misjudge the distance, you can thump the
> airplane..... or worse, and I believe (if I survived) I would feel
> really stupid if I wrecked my bird while practicing dead stick with an
> engine that would still run.
>
John, I have to agree with you on this one. I am probably the lowest time
pilot in a Kolb on the list but I put this whole thing in the same category as
practicing Stalls. I would not practice stalls at 500 ft and I would not
practice engine outs over a 500 ft long strip. Most Kolbs seem to act differently
with the engine off rather than at Idle. It only makes sense to understand how
yours will act. Remember that in Experimental your are the Test Pilot and have
an obligation to understand all aspects of your own Unique Aircraft. Just my
opinion.
do not archive
Message 14
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| Subject: | Re: Quiet Landings/Practice Dead Stick |
--> Kolb-List message posted by: "JIM HEFNER" <hefner_jim@msn.com>
--> Kolb-List message posted by: robert bean <slyck@frontiernet.net<mailto:slyck@frontiernet.net?subjectRe: Quiet Landings/Practice Dead Stick&replyto200507221441.j6MEfTJp018673@mail.matronics.com>>
I've had a couple flameouts in my life (airplane that is) both
induction icing
during brutal weather. Both times no dents. -Still have never
deliberately
shut it down in the pattern. Guess I would want a nice BIG runway
beneath.
If you get a little slow 20 ft off the ground you might have a problem
that
the throttle would ordinarily solve. My garbage can panel has ONE
switch
so I won't get confused. Start/stop.
BB do not archive
----------------------------------
Bob, if you practice landings at idle, you have already figured out how to set
your glide angle, when to apply flaps, etc to land, so it is really no different
with the engine off. I had practiced many many times pulling back the power
to idle in the downwind leg of the pattern and gliding across base and turning
final, adjusting attitude to keep the airspeed around 50, applying full flaperons
and again adjusting attitude slightly as needed to flare and touch down...
as I mentioned I land this way every time... not with power. If you never
practice this, then dead stick landings are not advised... if you do, they are
a piece of cake.
I've got a 4200' paved strip to work with, so if I were nervous about making the
runway I would have turned base before the end of the runway. When I touch
down I can be stopped in 100' if I want with brakes, so there is little to be
concerned with when you know how far the plane will glide from previous practice
at idle.
You mentioned your panel has one switch... that's great that you can reach your
panel.... can't reach the panel in a FF, so the ignition switch is along side
the seat... nice to have the redundancy to ensure you really mean to turn it
off... it's like when you go to delete an email and it asked you if you're sure...
I always complained when the fire alarm went off at IBM and we all had to leave
the building in an orderly manner and go out to the parking lot and assemble
there to make sure everyone was accounted for... wonder why they kept making
us practice all those false alarms??
Like I said, each to his own and their own decisions about this. I was only sharing
my experience, since I think it is something that can help us be prepared
better when things don't go as planned.
Cheers,
Jim Hefner
Tucson, AZ
FF#022 215 hrs
Do Not Archive
Message 15
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| Subject: | Re: Quiet Landings/Practice Dead Stick |
--> Kolb-List message posted by: "Ed Chmielewski" <edchmiel@mindspring.com>
Steve/John/Kolbers all,
This dead-stick thread is great, as it brings up a lot of valid
points. As a former CFI I'll agree there's no 'right' or 'wrong' way for
all circumstances, but for all but the unwilling I would demonstrate true
dead-stick landings with plenty of altitude and to a runway of excess
length. The students always remarked about the increase in glide without
the windmilling prop, and the slip practice which resulted (to lose the
excess altitude) was another side benefit. This is something that I feel
should be practiced in advance, and not left to luck should the engine quit
for whatever reason.
As someone once told me, "An airplane should never surprise you, but
it might disappoint you occasionally".
Ed in JXN (MI)
MkII/503
----- Original Message -----
From: "Steve Kroll" <muso2080@yahoo.com>
Subject: Re: Kolb-List: Quiet Landings/Practice Dead Stick
> --> Kolb-List message posted by: Steve Kroll <muso2080@yahoo.com>
>
> <<<<<I forget who wrote this on the Kolb List, but it was to the effect
> that they would not take a chance practicing a dead stick landing,
> possibly breaking the airplane. >>>>>>
>
> It was me that said that John but you misunderstood. I had already had an
> unannounced engine out and subsequent forced landing and it seemed to me
> at the time it happened that the glide was steeper with the engine off.
>
> I still don't like the idea of practicing engine outs with the ignition
> off.
Message 16
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| Subject: | Quiet Landings/Practice Dead Stick |
--> Kolb-List message posted by: "Steve Garvelink" <link@cdc.net>
Aw come on guys I used to know a flight examiner that used to randomly
shut the engine down take the keys out of the ignition and throw them
out the window. I think he had a spare in his pocket but that was a
random part of his flight test. Best to practice engine out over a
large flat airfield or salt flats.
Imho
srglink
-----Original Message-----
From: owner-kolb-list-server@matronics.com
[mailto:owner-kolb-list-server@matronics.com] On Behalf Of Rusty
Subject: RE: Kolb-List: Quiet Landings/Practice Dead Stick
--> Kolb-List message posted by: "Rusty" <13brv3c@bellsouth.net>
Personally, I would rather take a chance of missing a 3,000 ft strip
and learn how to fly my MKIII engine out than do it your way.
I don't have any old sayings for you, but the example you used, above,
doesn't fit pilots that do realistic training in the eventuality that
the engine stops unannounced.
-------------------
Hi John,
If you have exactly the right circumstances to practice this, it would
be
fun, and you'd gain valuable experience. No doubt about it. However,
miss
that runway and end up in someone's yard, and you'll be hung out to dry
for
being reckless. Imagine having to convince an average jury that turning
off
the engine in your plane was a reasonable thing to do. Might as well
just
plead guilty. You could still make a case that this slight risk is
worth
taking, considering the knowledge that could be gained.
I would never have considered shutting off the engine of a plane before
I
actually had an emergency situation. Now that I've logged a few minutes
of
(flaming) glider time, I'm actually more open to doing some real glide
testing. Deep down, I think we don't really believe the plane will fly
without power until we see it first hand, then it's not as scary as it
used
to be.
Cheers,
Rusty (starting to think SS-022 is a hurricane magnet)
Message 17
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| Subject: | Re: Quiet Landings/Practice Dead Stick |
--> Kolb-List message posted by: "John Hauck" <jhauck@elmore.rr.com>
would be
| fun, and you'd gain valuable experience. | Rusty
Rusty/Gang:
You guys are making a big deal out of shooting practice dead stick
landings.
Next time you have an engine out I hope you "have exactly the right
circumstances to practice this."
If you have doubts you can not make a 3,000 ft runway from 1,000 feet
AGL, engine off, you need all the help you can muster to survive as a
pilot of any kind of powered aircraft. The FAA Daily Accident Briefs
are full of engine outs, most of which are GA. Of course, we don't
hear of all the experimental and UL engine outs.
Couple weeks ago was the first dead stick I had shot in a longggggg
time. I must admit, that moment of apprehension/hesitation when I
reached for the kill switch. However, as soon as the 912 was shut
down and things got quiet, I was relaxed and certainly enjoyed the
flight and the landing. Was a good exercise which pointed out to me
how rusty I was shooting dead stick landings. With 3,000 ft to land
on, although way out of shape for it, I had plenty options of where on
that 3,000 feet of sod I wanted to touch down. I must make it a point
to get over to Wetumpka Airport more often and get and maintain
proficiency shooting dead stick landings.
I think proficiency is the word I have been looking for.
john h
MKIII
Message 18
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| Subject: | Re: Quiet Landings/Practice Dead Stick |
--> Kolb-List message posted by: "John Hauck" <jhauck@elmore.rr.com>
|Best to practice engine out over a
| large flat airfield or salt flats.
|
| Imho
|
| srglink
srglink/All:
Absolutely, cause that is where we are going to have our engine
failures, every time. ;-)
john h
MKIII
DO NOT ARCHIVE
Message 19
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| Subject: | Quiet Landings/Practice Dead Stick |
--> Kolb-List message posted by: "Rusty" <13brv3c@bellsouth.net>
|Best to practice engine out over a
| large flat airfield or salt flats.
|
Absolutely, cause that is where we are going to have our engine
failures, every time. ;-)
john h
MKIII
DO NOT ARCHIVE
-----------------------
John,
To continue this "logic", you should practice your next dead stick landings
over some of those mountains in Alaska :-)
Seriously, I thought my post was more for than against. I'm just pointing
out the sad facts of what will happen if something goes wrong. Despite your
ability to hit the runway, the circumstances still have to be right. What
about the Bonanza that does a straight in approach right in your way? What
about the pair of RV's that decided to line up on the runway for a formation
takeoff (gotta hate those guys <g>). Now those aren't your fault right, so
that makes it OK :-)
Say I turn my engine off near the airport, and someone calls 911 (which they
probably would). Do you think they will be amused?
I don't see how you could possibly take exception to my statement about
having the circumstances exactly right.
Cheers,
Rusty (practicing engine outs in my van later)
Message 20
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| Subject: | Re: Quiet Landings/Practice Dead Stick |
--> Kolb-List message posted by: "John Hauck" <jhauck@elmore.rr.com>
Rust/Gang:
Good idea to practice normal, expected pilot procedure, announce one's
intentions prior to executing.
Nothing is absolute, especially aviation. Problem with aviation is
gravity. Most folks are susceptible to it. Can't stop in the middle
of the exercise and try to figure out what our next action is going to
be.
As far as Alaska, I believe I readily admitted that should the engine
have shut down, I was prepared to buy the farm, as soon as I tried
every other option available, and kept flying the airplane until it
stopped crashing. Don't believe there is much comparison between dead
stick landing practice and the type of flying I was doing in Alaska.
I wouldn't ask anyone to do that, nor am I asking anyone to practice
dead stick landings. Simply sharing my own personal views of what I
consider important to me to be able to better survive the exciting
sport we have selected.
There are not many airports, GA type, that I have experienced over the
years that I could not take evasive action, should the need arise
during a dead stick landing, and still make a successful landing on
the taxiway, sod on the side or in between the taxiway and runway.
Helps to use one's head when flying. Practice helps me learn to use
my head a little better.
As far as someone calling 911 because they saw me shooting practice
dead stick landings at the local airport, I am not too concerned with
what others might do in that case. Long as I am not doing something
illegal or causing a safety hazard.
Pays to think ahead of the airplane and situation. Most of the time,
when we lose the engine or something else causes a forced landing, we
don't have time to sit up there and think. We have to react
immediately without the luxury of brain storming our way out of the
situation. Immediate action. Especially in those circumstances where
a parachute and altitude is a major player.
john h
MKIII
DO NOT ARCHIVE
Message 21
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| Subject: | Re: Two Stroke Oil - personal ruin |
--> Kolb-List message posted by: "Denny Rowe" <rowedl@highstream.net>
Dale,
That reply someone posted from Tom Olenick the other day was an old response
from Tom, the poster must have kept it in his computer and reposted it to
the list the other day.
Denny Rowe
----- Original Message -----
From: "Dale Sellers" <dsel1@bellsouth.net>
Subject: Re: Kolb-List: Re: Two Stroke Oil - personal ruin
> --> Kolb-List message posted by: "Dale Sellers" <dsel1@bellsouth.net>
>
> he was yesterday.
> ----- Original Message -----
> From: "possums" <possums@mindspring.com>
> To: <kolb-list@matronics.com>
> Subject: Re: Kolb-List: Re: Two Stroke Oil - personal ruin
>
>
>> --> Kolb-List message posted by: possums <possums@mindspring.com>
>>
>> At 11:10 AM 7/21/2005, you wrote:
>>>--> Kolb-List message posted by: "Dale Sellers" <dsel1@bellsouth.net>
>>>
>>>Tom,
>>>
>>>Elaborate, if you will, on preventive as well as periodic proceedures and
>>>short falls of the Cuyuna II-02. I am particularly interested in
>>>weaknesses
>>>and pressure testing the crankcase.
>>>Any other things that I should look out for. The factory reccomendation
>>>on
>>>mixture is 40:to 1. I've noticed that most who run them have changed to
>>>50:1. What is your feeling on this?
>>>
>>>Dale Sellers
>>>Georgia UltraStar
>>
>>
>> I don't know if Tom is still on the list.
>>
>>
>>
>
>
>
Message 22
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--> Kolb-List message posted by: "Denny Rowe" <rowedl@highstream.net>
YES!
----- Original Message -----
From: "Jimmy" <jhankin@planters.net>
Subject: Kolb-List: tom
> --> Kolb-List message posted by: "Jimmy" <jhankin@planters.net>
>
> Either Wednesday or Thursday there was a post about engine overall and
> maintenance seemly from Tom, listing the TBO of a 447 to be 600 hours and
> a
> 503 at a lower time.
>
> Was this a past quote someone put on the site???????
>
> Jimmy Hankinson
> 912-863-7384
> Firefly 035
> JYL (Sylvania)
> Pegasus Field (Home)
> 2000 Feet X 100 Feet- Grass
> Rocky Ford, Georgia
> Do Not Archive
>
>
>
Message 23
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| Subject: | Re: Quiet Landings/Practice Dead Stick |
--> Kolb-List message posted by: "Chuck Stonex" <cstonex@msn.com>
I wonder how many pilots have died because they had a real engine out and no
dead stick experiance? It does not matter if was over a salt flat or a
mountain range, the emergency was the same and the results varied according
to the pilots personal experiances. I'm a rookie pilot, I pray I know the
correct procedures if my engine should fail. How many knew Jim Lee?? He died
when the 912 on a Kolb he was flying failed because he did the wrong thing.
As I understand it, he was preoccupied with restarting the engine and forgot
to fly the plane. I know this because I am in the process of buying one of
the planes (M-IIIC) he built and was told this by his co-builder yesterday.
You cannot know too much about anything your doing. Just too little. If you
asked a musician in New York how to get to Carnagy Hall, he would probably
tell you "Practice, practice, practice".
Chuck S
--> Kolb-List message posted by: "John Hauck" <jhauck@elmore.rr.com>
|Best to practice engine out over a
| large flat airfield or salt flats.
|
| Imho
|
| srglink
srglink/All:
Absolutely, cause that is where we are going to have our engine
failures, every time. ;-)
john h
MKIII
DO NOT ARCHIVE
Message 24
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| Subject: | Re: Quiet Landings/Practice Dead Stick |
--> Kolb-List message posted by: "Richard & Martha Neilsen" <NeilsenRM05@comcast.net>
I have one observation that I would like to share with you on this tread.
When you shout down that engine you aren't locked in to a specific glide
ratio. In our Kolbs we have a very powerful tool that will allow you to
adjust your glide to get you to the exact landing spot you want, it is your
flaps. They will not extend your glide but they WILL shorten it. As for
slips they aren't real effective in our Kolbs. The first thing I did when I
had a engine out was establish what I figured was my best glide speed and
tried to figure were it would take me. From there I knew the maximum
distance I could go and used my flaps to get me to the exact spot short of
that maximum where I landed.
Rick Neilsen
Redrive VW Powered MKIIIc
----- Original Message -----
From: "John Hauck" <jhauck@elmore.rr.com>
Subject: Re: Kolb-List: Quiet Landings/Practice Dead Stick
> --> Kolb-List message posted by: "John Hauck" <jhauck@elmore.rr.com>
>
Message 25
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| Subject: | 912S Rpm question |
--> Kolb-List message posted by: "Denny Rowe" <rowedl@highstream.net>
John H and other 912S users,
A non lister with a 912S powered Extra and a Warp drive prop needs to know what
RPM to prop his 912S to at WOT level flight. He expects to see 90mph at 5300
rpm cruise, and does not get it.
Can all Mk-3 drivers (Both types) who run the 912S and Warp blades (Also both types
wide and tapered tips) let me know what performance they are getting so I
can forward the info to him.
Denny Rowe, Mk-3 PA, still working on hanger and not flying. :-(
Message 26
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| Subject: | Quiet Landings/Practice Dead Stick |
--> Kolb-List message posted by: "Christopher Armstrong" <tophera@centurytel.net>
My actual dead stick experience was zero back in 1983 when I had to shut
down the engine due to my BRS chute (one of the first out there) falling out
of it's Velcro closed soft pack and trailing behind the airplane,
threatening to hit the pusher prop or wrap itself around the tail in as it
spun in the propwash. I was able to land on the runway that I took off from
and even able to stop without dragging the chute more then about 20 feet.
In 2002 I had my second engine out, this time due to a fuel pump failure in
an Aircoupe. This time I was just able to clear some powerlines and land in
a fairly decent field and due to shear luck missed the numerous big rocks
bumps and holes. Neither were fun and neither required anything of me but
to fly the plane near perfectly and touchdown soft and slow.
Over trees or other nasty terrain the same is going to be required, pick the
best looking spot, fly the plane near perfectly, and land as soft and as
slow as you can, aiming the ends of the wings at the big stuff and you at
the little stuff. If you are lucky the wing will bear the brunt of it and
you will survive the crash. If you are not lucky you will be really
smashed, or dead.
Practicing simulated or actual dead stick landings simply improves your
ability to judge how far you can glide, and to manage the energy you have so
that you do land at that best looking spot flying as slowly as you can. I
had practiced throttle closed "dead" stick landings fairly recently before
each of my real emergency landings. I am very glad I did.
I am not sure that having practiced real engine out landings would have
improved my results significantly. It would have given me a bit better
understanding of the airplanes performance, and I would have been able to
judge my landings a bit better. I certainly don't think that there should
be any danger to practicing real engine out landings for a competent pilot.
Pilots should only do this under good conditions, a fairly calm day, a nice
big runway, and no traffic around. Learning to make all your approaches
such that you don't use the throttle to bail you out in the end is probably
as useful, and I feel should be standard practice for Two-stroke,
auto-conversion and other "experimental" engine flyers. Long flat
approaches under significant power should be reserved for people flying
extremely reliable engines.
Christopher Armstrong
Message 27
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| Subject: | Re: 912S Rpm question |
--> Kolb-List message posted by: "John Hauck" <jhauck@elmore.rr.com>
to know what RPM to prop his 912S to at WOT level flight. He expects
to see 90mph at 5300 rpm cruise, and does not get it.
Denny R/Gang:
With any non-inflight adjustable prop:
5,500 rpm WOT (wide open throttle) straight and level flight.
That works out to about 5,200 to 5,300 rpm static WOT.
He may see 90 mph at 5,300 rpm as above. Barnaby Waffrain redesigned
the MKIIIC and came up with a streamlined Extra.
For my purposes, I can fly between 80 and 85 mph at 5,000 rpm. 5,000
rpm seems to be a comfortable cruise rpm for me and the airplane. The
MKIII flies well at 80 to 85 mph cruise.
john h
(Prejudiced to the MKIIIc I have been building and flying since 1991.)
PS: Those same numbers apply to the 912UL engine also.
Message 28
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| Subject: | Quiet Landings/Practice Dead Stick |
--> Kolb-List message posted by: "Rusty" <13brv3c@bellsouth.net>
There are not many airports, GA type, that I have experienced over the
years that I could not take evasive action, should the need arise
during a dead stick landing, and still make a successful landing on
the taxiway, sod on the side or in between the taxiway and runway.
Helps to use one's head when flying. Practice helps me learn to use
my head a little better.
-------------------------
John,
So rather than admit that the conditions need to be right, you will maintain
that having something go wrong, and become a real emergency is good, because
you get to use your head better? Your logic escapes me.
Rusty (my last reply to this thread)
Do not archive
Message 29
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| Subject: | Quiet Landings/Practice Dead Stick |
--> Kolb-List message posted by: "Steve Garvelink" <link@cdc.net>
What was meant by that is don't put yourself at un necessary risk while
practicing. Doesn't mean you cant put an imaginary target on the area to
see how proficient you are becoming. I used to do engine off with my
eiper all the time and became quite proficient at landing on the point
every time.
srglink
-----Original Message-----
From: owner-kolb-list-server@matronics.com
[mailto:owner-kolb-list-server@matronics.com] On Behalf Of John Hauck
Subject: Re: Kolb-List: Quiet Landings/Practice Dead Stick
--> Kolb-List message posted by: "John Hauck" <jhauck@elmore.rr.com>
|Best to practice engine out over a
| large flat airfield or salt flats.
|
| Imho
|
| srglink
srglink/All:
Absolutely, cause that is where we are going to have our engine
failures, every time. ;-)
john h
MKIII
DO NOT ARCHIVE
Message 30
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| Subject: | Quiet Landings/Practice Dead Stick |
--> Kolb-List message posted by: Richard Pike <richard@bcchapel.org>
I have followed this thread with a lot of interest, and a lot of amazement.
There are a half dozen grass strips within an hour of here that are at
least 2,000 feet long, and several of them are surrounded by pasture fields
where an off-airport landing would be nothing worse than a nuisance. No
excuse not to go practice dead stick landings. Back in 1984, when all I had
was a Maxair Hummer - an ultralight that had maybe half a Kolb's agility -
I used to fly over a 2,000' grass strip at various altitudes and headings
and turn the engine off and practice making spot landings at a
predetermined place on the strip, figured it was cheap insurance.
Have not practiced as many on the MKIII, but have done enough to know how
it behaves. So far I have had two unplanned engine outs on the MKIII and
each was nothing more than a great nuisance, with no damage. (Unless you
count the green stains from the cow manure slung on the wings)
Something that has not been mentioned so far is the mental and emotional
spike that happens when the engine quits and you are totally unprepared
psychologically for it. In my younger days, I did a bit of boxing, and the
first time somebody really busts you in the nose with a good stiff jab, and
Tweetie Bird starts flying around your head, your brain wants to draw a
blank. You are mentally and psychologically unprepared for such a barbaric
event to happen. But after you get used to it, then it's just something you
deal with.
Having an engine out is a bit like that. Suddenly everything gets quiet,
and the brain wants to draw a blank. But if you have previously gotten used
to it, then it's just something you deal with.
I expect that there are many pilots on the list who are much more competent
than I, but IMO, competence also consists of being able to stick your
airplane into a 500' strip, dead stick, ten times out of ten, and still be
able to use it afterward. Can I do that? Probably not right now, but I plan
to be able to do it by this time next year.
Richard Pike
MKIII N420P (420ldPoops)
do not archive
Message 31
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| Subject: | Re: Quiet Landings/Practice Dead Stick |
--> Kolb-List message posted by: "John Hauck" <jhauck@elmore.rr.com>
maintain
| that having something go wrong, and become a real emergency is good,
because
| you get to use your head better? Your logic escapes me.
|
| Rusty (my last reply to this thread)
Rusty/All:
You're worse than a TV reporter. Your changing my stuff and trying to
put words in my mouth. ;-)
Reread my post. First paragraph first!!!
I'm not maintaining do diddly squat.
Want to do a dead stick landing, announce your intentions, make sure
it is safe, then execute it. If the situation changes, try to make a
good decision....................
Before you grade me on logic, try reading and understanding what I
wrote correctly.
john h
DO NOT ARCHIVE
Message 32
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| Subject: | Re: Old thread- Trips |
--> Kolb-List message posted by: DCulver701@aol.com
Hi Steve, read your post on locating Lake Yale on your map. Our place is on
the N.W. corner of the lake, just above a big Baptist retreat, off of Hy. 452.
Its called Sunlake Estates, a retirement community with approximately 250
homes. There is a marina with about 40 boat slips, with the boat ramp being a
short distance away. There,s also a public dirt ramp directly adjascent to our
community. Should be easy to spot. Best regards, Dave Culver
Message 33
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--> Kolb-List message posted by: "flykolb" <flykolb@carolina.rr.com>
Kolbers:
I have had three dead stick landings.
1 - In the pattern on downwind, unexpected engine out, landing no problem
2 - just took off from short grass strip, unexpected engine out, landing no problem.
3 - just took off from my grass strip, "kind of" expected engine out, turned back
but was high. Dove for strip. Flaps would not do it so did away with flaps
and just dove. Landed on the last 1/3 of runway (2000' grass strip), no problem.
It is amazing how that big fan keeps the pilot cool. When it stopped it got very
warm!
Jim
Mark III
Message 34
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| Subject: | Re: M-IIIC Drivers in Iowa |
--> Kolb-List message posted by: "woody" <duesouth@govital.net>
I told him that if something happened like getting unexpectedly airborn
don't panic just fly the plane. He was a pilot but it still took him 3
passes to figure out the right approach to land. No panic to get it back
down just kept flying untill he got things figured out.
Perhaps I am to used to Kolbs. Flying a Challenger was the most
frighteneing experience I had had in years. I was not prepared for the extra
rudder needed to stop a turn. These planes need rudder or it won't get out
of a turn, The extra stiff rudder pedals and lack of concern about rudders
in the Kolb had me circling for 10 minutes (felt like hours) trying to
figure out what to do next. Finally a hard kick to the rudders got some
movement and I straightened up. Quite frightening. I tried another
Challenger that day with the same result and need for rudder. Still could
not keep the nose from wandering around. I do understand the aircraft
exported to the UK have bigger rudders and may be less needy of rudder
input.
You're going to love the Kolb
----- Original Message -----
From: "PATRICK LADD" <pj.ladd@btinternet.com>
Subject: Re: Kolb-List: M-IIIC Drivers in Iowa
> --> Kolb-List message posted by: "PATRICK LADD" <pj.ladd@btinternet.com>
>
> He didn't panic just remembered what I had told him>>
>
> Chuck,
> What did you tell him?. I am about to change from Challenger to Kolb and
> have not flown a tail dragger since I sold the Thruster many years ago.
> NB. The Challenger is not half as bad as this lot make out :-)
>
> Pat
>
>
> --
>
>
> --
>
>
Message 35
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| Subject: | Re: M-IIIC Drivers in Iowa |
--> Kolb-List message posted by: "Billie Futrell" <bill_joe@bellsouth.net>
I would just like to add a little to what Woody has just said about a
Challenger. I was going to buy a Challenger before I bought my Kolb. A
friend of mine had a Challenger with the long wing so I flew with him for 3
hrs.I won't to tell you that was all I wanted. The first hr I was chasing
the thing all over the sky. You want to make a correction to the left, so
you give it aileron and it goes more to the right and then to the left. The
second hr I figured out that you had to fly with rudder, and a lot of that
and follow up with aileron. The only problem was before the hr was up I had
cramps it the calves of my legs so bad I could hardly use my the rudder
peddles. The third hr was not any better and when I left the field that day
I knew I did not want a Challenger.
I'm glad I go a kolb.
Bill Futrell MK111Xtra912
Do not archive
----- Original Message -----
From: "woody" <duesouth@govital.net>
Subject: Re: Kolb-List: M-IIIC Drivers in Iowa
> --> Kolb-List message posted by: "woody" <duesouth@govital.net>
>
> I told him that if something happened like getting unexpectedly airborn
> don't panic just fly the plane. He was a pilot but it still took him 3
> passes to figure out the right approach to land. No panic to get it back
> down just kept flying untill he got things figured out.
> Perhaps I am to used to Kolbs. Flying a Challenger was the most
> frighteneing experience I had had in years. I was not prepared for the
extra
> rudder needed to stop a turn. These planes need rudder or it won't get out
> of a turn, The extra stiff rudder pedals and lack of concern about rudders
> in the Kolb had me circling for 10 minutes (felt like hours) trying to
> figure out what to do next. Finally a hard kick to the rudders got some
> movement and I straightened up. Quite frightening. I tried another
> Challenger that day with the same result and need for rudder. Still could
> not keep the nose from wandering around. I do understand the aircraft
> exported to the UK have bigger rudders and may be less needy of rudder
> input.
> You're going to love the Kolb
>
>
> ----- Original Message -----
> From: "PATRICK LADD" <pj.ladd@btinternet.com>
> To: <kolb-list@matronics.com>
> Subject: Re: Kolb-List: M-IIIC Drivers in Iowa
>
>
> > --> Kolb-List message posted by: "PATRICK LADD" <pj.ladd@btinternet.com>
> >
> > He didn't panic just remembered what I had told him>>
> >
> > Chuck,
> > What did you tell him?. I am about to change from Challenger to Kolb and
> > have not flown a tail dragger since I sold the Thruster many years ago.
> > NB. The Challenger is not half as bad as this lot make out :-)
> >
> > Pat
> >
> >
> > --
> >
> >
> > --
> >
> >
>
>
Message 36
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| Subject: | Re: M-IIIC Drivers in Iowa |
--> Kolb-List message posted by: "Chuck Stonex" <cstonex@msn.com>
I am actually very excited about flying this M-III. I talked to one of the
orginal builders and got a very positive history. He actually told me what
the plane was like. the only thing different was that according to him it
had aluminum diamond plate on the floor. Now it has smooth aluminum for some
reason. There are no indications of damage so maybe someone need the diamond
plate for something else. I do want to get rid of the 618 on it though. See
if I can get a 582 or equivilent.
Chuck
--> Kolb-List message posted by: "woody" <duesouth@govital.net>
I told him that if something happened like getting unexpectedly airborn
don't panic just fly the plane. He was a pilot but it still took him 3
passes to figure out the right approach to land. No panic to get it back
down just kept flying untill he got things figured out.
Perhaps I am to used to Kolbs. Flying a Challenger was the most
frighteneing experience I had had in years. I was not prepared for the extra
rudder needed to stop a turn. These planes need rudder or it won't get out
of a turn, The extra stiff rudder pedals and lack of concern about rudders
in the Kolb had me circling for 10 minutes (felt like hours) trying to
figure out what to do next. Finally a hard kick to the rudders got some
movement and I straightened up. Quite frightening. I tried another
Challenger that day with the same result and need for rudder. Still could
not keep the nose from wandering around. I do understand the aircraft
exported to the UK have bigger rudders and may be less needy of rudder
input.
You're going to love the Kolb
----- Original Message -----
From: "PATRICK LADD" <pj.ladd@btinternet.com>
Subject: Re: Kolb-List: M-IIIC Drivers in Iowa
> --> Kolb-List message posted by: "PATRICK LADD" <pj.ladd@btinternet.com>
>
> He didn't panic just remembered what I had told him>>
>
> Chuck,
> What did you tell him?. I am about to change from Challenger to Kolb and
> have not flown a tail dragger since I sold the Thruster many years ago.
> NB. The Challenger is not half as bad as this lot make out :-)
>
> Pat
>
>
> --
>
>
> --
>
>
Message 37
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| Subject: | Torsional Resonance & Drive Trains |
--> Kolb-List message posted by: "Richard Swiderski" <rswiderski@earthlink.net>
Kolb Gear Heads:
Below is an article I found on torsional resonance which is an
incredible insight into what is lurking in all our engines. It's a
fascinating story. If you are building or modifying a reduction drive this
will be a sobering read. All others, it will give you an appreciation of
the engineering that makes our fun possible. I don't know where I
originally acquired this, so I can't give due credit to the author.
PS: In this article, there is an illuminating insight into spag clutches
that we were wondering about a while back.
Richard Swiderski
SlingShot Turbo Suzuki still in the oven.
PROPELLER DRIVE SYSTEMS AND TORSIONAL VIBRATION
Don brings his unique experience in testing of aircraft to these pages. A
graduate of Northrup University and life long interest in new aeronautical
concepts, his concerns for safety and progress of auto engine conversions
prompted this article. Hopefully, his information will create a better
awareness of the engineering challenge facing experimenters in modern
aircraft power plant development. We welcome additional articles on the
subject. MCM
By Donald P. Hessenaur
As aircraft engine prices continue to rise beyond the reach of most who
would like to build and fly their own aircraft, many are turning to
alternate power sources. This is not a new phenomena. From the Wright
brothers on, many have designed, built or converted engines to aircraft use.
At one time or another engines have been used from automobiles, motorcycles,
outboard motors and even snowmobiles, with varying degrees of success or
failure.
AUTO ENGINE CONVERSIONS
Today many automotive engine conversions are appearing on the aviation
scene. They are definitely a viable alternative. The automotive engine today
is veny advanced technically and relatively low in cost when compared to
Lycomings and/or Continentals. Unfortunately, automotive engines are
designed and optimized for the automobile and not for aircraft. Generally
auto engines operate at a much higher RPM. The torsional vibration
characteristics of a given engine, connected to a transmission, drive train
and wheels, are quite different from that of the same engine, connected to
an aircraft propeller. The damping action of the tires on the road and the
inertia effects of the mass of the automobile are not even close to the
damping/inertia effects of a propeller turning in air.
TORSIONAL RESONANCE
In recent years, I have developed a concern that many of the individuals
and/or companies involved in the development of auto conversions do not seem
to have an understanding of the problem of torsional vibration. I'm
notsaying that this is true in every case. Some appear to have a profound
knowledge of torsional vibration but others seem to dismiss it as a minor
problem. They feel all they need to do is just stick in a rubber damper,
freewheel clutch or some other quick fix and maybe the problem will go away.
My experience has been that torsional vibration just doesn't go away. It can
be the life or death of an entire project, not only technically, but it can
also lead to a financial black hole for the individuals or company involved!
The potential for success in such a project would be much higher if the
individuals involved knew what they were dealing with and would use valid
aircraft engineering procedures during the design and development of an
engine. Creativity and experimentation should be encouraged but one must
also realize that 9 times out of 10, what was thought to be a new and
original solution to a problem has probably been tried by a number of people
in the past. The same laws of physics, dealing with torsional vibration, are
still in effect today, as they were 20 to 50 years ago. I would be the first
to admit. I do not have all the knowledge on vibration in rotating systems.
Nevertheless, I have had some unique experiences with tonsionals and other
associated vibration problems. It is my hope that by relating them, someone
will be saved from some grief.
FIRSTHAND EXPERIENCE
in the past I have had the opportunity to have worked on three interesting
projects each of which involved torsional vibration problems to one degree
or another The first was the Avian 2-t80 gyroplane which was developed in
Georgetown, Ontario, Canada in the early 60's. The performanoe and handling
of this gyroplane has not been surpassed by any other in its class to this
day. The second was the BD-5 'Micro" kit aircraft developed in Newton,
Kansas by Jim Bede in the early 70's. The third was the RotorWay RW-133
helicopter engine developed by B.J Schramm in the mid-70's.
AVIAN VIBRATION ENCOUNTERS
The Avian gyrocopter was a pusher design with a ducted Hartzell propeller.
The rotor was an articulated 3 bladed semi-rigid, high inertia design. For
this reason, a substantial drive system was required for rotor spin-up. On
the original prototypes there was a 3 inch wide, heavy duty,square toothed
belt that transmitted engine power from a smaller driver sprocket to a large
driven sprocket at the base of the rotor hub. Occasionally, during a
spin-up, this belt was stretched by some horrendous load so that the belt
teeth would no longer engage the teeth on the driven sprocket causing the
belt to ride up on top of the sprocket teeth. The resulting high load on the
sprockets caused the structure that supported the bearings to collapse (A
round toothed HTD type belt would have eliminated the riding up problem of
the square tooth belt but it had not as yet been developed in the early
60's.)
About this time, Avian started to develop and build their last prototype. It
was totally redesigned and much improved in every way over the previous
prototypes. One area of improvement was the rotor spin-up system The upper
belt width was increased to 4 inches and the structure that supported the
sprocket bearings was made more substantial. A new hydraulic multi-plate
clutch was designed with more torque capacity and mounted over the engine
near the propeller end. This improved drive gave the new prototype
absolutely phenomenal jump take-off performance. The gyroplane was capable
of jump take-off to 50 ft. The problem of the upper bed drive had been
solved by the brute strength approach, using a stiffer support structure
along with a wider belt and sprockets. Nevertheless, as time went on other
problems started to show up. The lower belt drive, that took power off the
engine seemed to flop a lot at various times. After a few spin ups the
clutch would become very hot and eventually turn blue in color. If the
cowling was removed, immediately after a spin-up the clutch would appear to
have been red hot. The torsional loads going through the drive system
appeared to be much higher than the original analytical numbers indicated. I
had heard about torsional vibration during my college years but at the time
it never hit me that the problem with the drive system involved torsional
vibration. As far as I know, the clutch problem was never solved.
FLUTTER & VIBRATION TESTING
While at Avian I was assigned to work with a consultant who was hired to do
ground vibration testing and a flutter analysis on our new prototype. This
was a relatively new technology and he was the only person who did this kind
of work at the time. Although he was from Tononto, Canada, he worked
throughout the American aerospace industry. His equipment included a number
of vibration shakers that were attached to the airframe, making it vibrate
at various input frequencies. The shakers were controlled from a control
panel. A number of magnetic vibration sensors were attached to the airframe,
along with one that was hand held, so it could be moved around. These
pickups were used to sense the resulting amplitudes of vibration at various
points on the airframe. This information was then displayed on an
oscilloscope. He was able to adjust the input frequency, so that various
parts of the airframe would vibrate at their respective resonance frequency.
The needles on the instruments, the door handle, the plexiglass in the side
window, a duct support struct or the rudder could all be made to vibrate at
their individual resonance frequencies. It was really weird. In fact, it
appeared downright mysterious to see this engineer adjust the input
frequency and shake any part he wished on the airframe.. He made a frequency
survey of everything that resonated on the gyroplane. This was used to
determine if anything resonated within the operating frequency range of the
engine, drive system or rotor, that might cause a failure in the future.
With this analysis, we found a number of parts that needed to be stiffened
or redesigned so they would not vibrate or flutter in flight.
During the 3 days I worked with this engineer as his assistant, I received a
wealth of knowledge about vibration and resonance in aircraft.
BEDE AIRCRAFT
I was interviewed and offered an engineering position with Bede AincraH by
Burt Rulan. My employment started on July 6, 1972. After the Avian years, my
interest in the entire subject of vibration expanded and I became fully
aware of torsional problems in rotating systems. Many spare hours were spent
hitting engineering texts and reading numerous articles on the subject,
including many by Molt Taylor. I was really curious as to how they had
solved the torsional vibration problem in the BD-5.
During the finst week at Bede, Les Berven was flying the BD-5 every day.
When it would come down aher a flight, the mechanics would open up the
engine compartment to take a look to see what was going on It wasn't long
before I realized there were a number of problems they were laying to deal
with. The engine was having cooling and mixture problems while trying to
maintain the EGTs and CHTs below redline. The problem that really caught my
attention was the overheating of the belt and sheaves.
At that time they were running a snowmobile belt on variable ratio sheaves.
The overheating clutch at Avian came to mind when I noticed these sheaves
were quite discolored from the high temperatures involved.
TORSIONALS AT BEDE
During the following weeks they seemed to be doing a lot of ground testing.
I had been assigned the responsibility for the weight and balance control
for the BD-5 program, as I had done at Avian. Like the Avian 2-180, the BD-5
had a severe aft CG problem. One day they had been running the BD-5's engine
on the ground for a period of time and all of a sudden there was a big
explosion. The belt had disintegrated, with pieces all over the tarmac.
These pieces of belt were as hard and bridle as bakelite plastic. As soon as
I saw what happened, I knew the problem was torsional resonance. I mentioned
this to the other engineers and they looked at me sort of strange. They
thought I was joking and did not pay too much attention to my comment, since
I was just the new engineer.
HTD UNIROYAL BELT
Soon after the belt incident some belt people were invited to come and look
at our situation The representatives brought a number of belts such as
standard V, poly V and various toothed belts. One belt that I had never seen
before, caught my eye. It was a unique round toothed belt, an 6mm HTD belt.
Aher all the problems associated with square toothed belts at Avian, when I
saw that round toothed belt, I knew this was an exceptional design. It could
be used on an aircraft and give much more reliability than one with square
teeth. Best of all, the power loss was exdremely low, since it ran at low
friction levels, resulting in considerably less heat buildup
About this bme I was asked to start investigating various belt systems and
get involved in the drive system and engine installation problems. Along
with this assignment, I continued to head up a weight reduction program,
particulafiy in the aft part of the ship. It was my intent to not only solve
the drive system and engine installation problems but to save weight in
those areas as well. Anything that could be done to remove weight, aft of
the CG, would permit lead to be removed from the nose. So started working on
a new drive system, using the 8mmHTD belt. Once it was put together and
running, it seemed at first to perform quite well, but I soon noticed there
was a lot of flapping of the belt at certain RPMs. We tightened the belt as
much as we could but the flapping just seemed to persist. Nevertheless, it
seemed to solve the problem for the moment and Les Berven put in a lot of
flight time. Eveny once in a while we would have a failure but we would
replace or repair the part and keep going. During this time we actually had
more of a problem with the snowmobile engine. Various magazines were coming
out with articles on the BD-S. It was becoming very popular and kit sales
were climbing.
ENGINE MOUNT FAILURE
One significant event that occurred was the failure of the engine mount due
to fatigue. The mount was welded upchrome-moly tubing and had a strange
crystallized break. When I saw it, I knew it had something to do with the
torsional vibration that was still in the system. A new heavier piece of
tubing was welded in to make it stronger and beefier but during the next few
flights it proceeded to break again. At this point a new heavier engine
mount was fabricated and installed but soon after another failure occurred.
This time the engine mount survived but the sheet metal channels that
transferred the engine load into the fuselage, along with portions of the
fuselage itself,were severely cracked. Also, numerous rivets were starting
to work loose in the airframe. All that we had accomplished was to transfer
and chase the problem from one area to another. The torsional problem was
still with us. The biggest problem I had was that no one would believe me.
At least the belt was holding up and no longer a problem.
MYSTERIOUS SHAFT FAILURE
The drive system difficulties were totally overwhelmed by the problems with
the two stroke engine. To keep the planes flying for demonstrations and air
shows, we were forced to place the highest priority on keeping the engines
running. (If only the Rotex 562 had been available, we might have eliminated
a major problem with the BD-5!) Cooling was a real difficult problem and one
evening I and many of the engineering personnel stayed almost all night to
find a solution. Burt was really frustrated with this cooling problem. In a
last ditch effort, he got one of the giant portable electric shop fans,
hooked it up to a large duct and then attached the duct to the open BD-S
engine compahment. He felt if we couldn't get the engine to cool properly
with this fan, there was no way we were going to get it to cool in the air.
We ran the engine at full power and cycled the engine off and on a number of
times. All of a sudden during one of the runs, something broke loose and the
engine immediately went up to a very high RPM and seized. We found the
propeller could turn freely without turning the drive belt or the engine. We
looked all around and through everywhere and couldn't see where any break
had occurred. No shaft had broken, nothing had failed that we could see. It
was a real mystery.
BD-S HTD belt drive components Tests were run on various belt widths to
establish useful life recommendations.
The drive system we had at that time used the HTD belt with the original
upper main shaft. If I remember correctly, the O.D. of this shaft was about
3 inches and approximately 4 feet long. I am not sure of the wall thickness
but it may have been .125 inches. This shaft had a machined bearing support
fitting on each end, with the propeller mounted on the rear hub fitting and
the HTD sprocket mounted on the front sprocket fitting. These end fittings
were mounted to the inside diameter of the shaft, with three AN-4 bolts on
each end, screwed radially into the shaft. The bolts were quite short so the
threads went right up to the head, placing threads right in the shearing
intersection between the fittings and the shaft itself. It was these 3 bolts
at each end that transferred the torque from the HTD sprocket to the
propeller hub at the rear. This was the configuration of the upper shaft
when I arrived at Bede. Having bolts transfer torque in shear through the
threaded area is not exactly a textbook design procedure but it had held for
a year or more.
TORSIONALS STRIKE AGAIN
So we got the mechanic and started taking everything apart. When we pulled
out the upper shaft, we found that all 6 bolts, 3 on each end, had failed
precisely at the same time Now this was weird or like black magic. You would
think that if something was going to fail, maybe the rear end would be ready
to go but the front end might break loose first, relieving the load, then
the back end would not fail. But no both ends of the 4 foot shaft failed
precisely at the same bme, with all 6 bolts failing the same way. They were
all crystallized and appeared to have been working in there for some time.
By this time, Burt and the others had become believers in torsional
resonance. Immediately we got on the phone, woke Jim Bede up and clued him
in on what had happened. Within a week or so Jim brought in Al Beaufrere, a
vibration expert from Long Island. I was assigned to work with him to solve
the torsional problem. He came up with two different test drive systems.
They were quite heavy and complicated but they did give us a direction in
which to go. While Al was at Bede, I tried to learn all I could from him.
This knowledge: combined with what I had picked up previously, gave us the
insight that eventually led to a solution to our dilemma.
THE MOLT TAYLOR DYNAFLEX SYSTEM
After Al left, I started to design a new drive system, using the principles
learned. It was about this time that many of the engineering staff were
moved into the new Bede Product Development building. I was given an office
withan other engineer named Larry Heuburger, who belive helped design the
Derringer twin engine airplane. Larry knew Molt Taylor quite well and was
able to persuade Jim Bede to let him design and build a small dynaflex
coupling out of aluminum. I must say he did a beautiful job and came up with
a real neat small dynaflex, which mounted right onto the engine. They used
it with the HTD belt system and large upper shaf that I had running at the
time. Ot appeared to successfully dampen out the torsional vibration. At the
same time they were testing the dynaflex system I was coming right along
with the design and fabrication of my new drive system.
I forget just how long they flew the Molt Taylor system but one day an in
flight failure occurred and Les had to deadstick the plane in. With all the
engine problems this was quite a common occurrence so it was no big deal. It
was found that the dynaflex had broken loose from the engine. A closer
examination revealed that the crankshaft had broken clean off. The break was
completely crystallized and it was difficult to discern whether it was a
torsional break or a lateral break. We were not able to determine why this
failure occurred. It may have been due to the rocking couple of the engine.
Unfortunately, this failure ended funkier work on the dynaflex system.
THE BROOMSTICK SHAFT
I had come to the conclusion, based on the information from Al Beaufrere,
that we needed to drastically lower the torsional frequency of the drive
system by lowering its torsional spring constant. Stan Welles, our stress
analyst, came up with a 6061-T6 aluminum shaft, with an outside diameter of
1 inch and a .095 inch wall thickness. This shaft came to be known as our
"broomstick shaft". The same tubing size was used for both the upper main
shaft and the lower jackshaft. Very soft rubber, donut type flexible joints
were mounted on each end of the jackshaft. This lower shaft assembly
transferred the power from the engine to the lower HTD sprocket while
allowing for engine motion. The sprockets were made of a rag-filled bakelite
type plastic by the Budd Corporation and are no longer available. They had
wear characteristics, designed to be compatible with the HTD belt and had
considerably less wear than anodized aluminum sprockets. Also they were
lighter in weight. The lower sprocket was mounted on an adjustable casting
that was mounted on the rear bulkhead of the engine compartment. The belt
went up to the upper sprocket, which was attached to the forward end of the
upper shaft.
The drive ratio was 1.6 to 1.0. Bearings within the sprockets took the belt
loads, which were relatively low since the belt was not preloaded. There was
no need to have a tight belt with a torsionally soft system. Since the upper
main shaft was only 1 inch OD, two bearings were mounted along its length to
tune out lateral vibrations. Another bearing was mounted off the rear hub to
take out the propeller loads. (Later, after I left Bede, Dan Cooney added
another bearing towards the rear, to more effectively take out gyroscopic
propeller loads )
FRlCTlON JOINTS
The shaft end fittings on the lower jackshaft and the propeller hub on the
upper shaft were attached with press-shrink friction fits. The fitting for
the upper sprocket on the forward end of the upper shaft was a removable
collet type friction fit. These friction fits were more than sufficient to
carry the torque of the engine and were one of the design guidelines given
to me by Al Beaufrere for joints subject to torsional vibration. This was a
very, very lightweight system. The weight of the entire drive system was
reduced by over 40 percent and this went a long way towards solving the aft
CG problem in the BD-5. For test purposes, the prototype drive systems were
designed and fabricated with zero safety factors. The first version of the
"broomstick' drive did not have a freewheel clutch and when we first ran the
system, we found out there was still much to be learned before the torsional
problem was solved.
LOW FREQUENCY TORSIONALS
The vibration characteristics of the new prototype system was quite
different from the previous systems. One could tell something radical had
changed. The resonant point had been lowered below 600 RPM, the starting RPM
of the engine. With such a low frequency and high amplitude of vibration, it
was possible to visually hear and see the resonance occurring. One could see
torque reversals occurring at the prop. The aircraft would violently shudder
and shake itself apart, if allowed to continue. As the throttle was
advanced, the RPM would get hung-up at the torsional point. Les could give
it full throttle and it would just soak up all the energy from the engine,
preventing the RPM from going through the torsional barrier. Occasionally,
more by chance than anything, the RPM would pass through the resonance and
then become super, super smooth. Likewise, when the engine was shutdown, the
RPM would momentarily hang-up at the resonance point. All of a sudden, the
plane would shudder and shake until all the energy of momentum was used up.
Then the propeller would stop rather abruptly. It was the weirdest thing.
Although we were successful in moving the torsional resonance point to a
lower energy level, we had not eliminated the problem. Numerous experiments
and tests were tried. At times, we were able to go into resonance with the
ignition and fuel off using only the electric starter. About the same amount
of shudder and vibration was produced through the aircraft when excited by
the engine compression alone, as it did when the engine was running under
its own power in resonance. At this point, we started to realize we had
something here that was really mysterious. This led to an experiment where
we replaced the two spark plugs with compression release valves, hooked up
to a common control handle. With the engine and system turning over using
the starter alone, the vibration and shudder in the plane instantly
disappeared and became as smooth as silk, as soon as we opened the
compression release valves. As soon as we would close the valves, the
vibration and shudder would return. We could start and stop the resonance at
will. Clearly, it could be seen that the resonance could be excited by
compression strokes alone. The thing that blew our minds was that even when
the input energy was low, the output loads were still as destructive to the
airframe as when the input energy was high
INFINITE LOADS?
When we started to look into torsional resonance theory we found an
explanation. Without any damping in the system, theoretically the peak load
at resonance reaches infinity. That's why the input load had very little
effect on the output load. Now many have said that it was just theoretical
and there isno situation where any material would have zero damping
qualities. Well, how much was the damping effect? We do not really know at
this point. If the damping were to bring the load down to one tenth of
infinity, that would still be a big load. What I am getting at is this: The
loads are very high during resonance and are not entirely dependent on the
input load.
THE FREEWHEEL CLUTCH
The idea for the freewheel clutch came from our machinist, Ray Johnson, and
I must give him the credit.
He came in one day and told me that when he was a kid, his dad had a
thrashing machine on the farm They would run the belt from the tractor to
the thrashing machine and it had a freewheel device on it so that any
vibration coming from the old two cylinder John Deere would be somehow taken
care of. The minute he said "freewheel clutch", it rang a bell. After
previously seeing the oscillating torque reversals of the prop I knew we
needed some way to allow a torque reverse to occur without the bounce back.
I had been looking at centrifugal clutches, manual clutches, etc. that could
be used to disengage and allow some slip. We even tried a test with a super
loose belt with idler pulleys but the slop still wasn't enough. The
torsional amplitude was just too great at the low system frequency we were
dealing with.
Immediately after Ray mentioned the freewheel clutch, I started
investigating and found a Borg Warner clutch that was used in automatic
transmissions It was a double cage, full phasing sprag clutch. The double
cage caused all the little cams inside to engage precisely at the same time.
I had previously had experience with freewheel roller type clutches at Avian
but we had problems with the brinelling of the clutch races when one roller
would engage before the others and momentarily take the full torque, causing
eventual clutch failure. The doublecage full phasing, sprag clutch solved
this problem.
It took a month or two to design and have the clutch parts made. The clutch
itself was mounted on the front of the upper plastic sprocket. It had its
own bearing to maintain the clutch concentricity. The inner clutch race was
integrated with the collar that transferred the torque to the upper 1"
shaft. The heat treat for the clutch races and collet was somewhat
complicated and expensive but at that point we weren't looking at the cost,
as much as just trying to find something that was lightweight and workable.
At that time I was under tremendous pressure at Bede to try to get this
system working. After a lot of hard work the parts were made, Everything
went together beautifully and the clutch was mounted in the airplane. About
that time, our engine company had some problems and we could not get any
engines. I had the drive system in the ship shortly after New Years but it
sat until sometime in March before we were able to get an engine to test it.
So, I was sitting that whole time wondering if it would work. Finally the
engine arrived. The mechanics installed it and started it up. It was super
smooth. There was no sign of any shudder or vibration in the aircraft due to
orsionals. The first tests were so successful that Les took the plane up. He
came back with a big smile on his face and told us it was the smoothest
drive system he had ever flown. Jim was relieved and happy, like, real
happy! We had solved the torsional problem.
Dyno test stand used for RotorWay engine development, air show
demonstrations,
and producting engine run-ins.
DUAL FREQUENCY SYSTEM
According to theory when the stiffness of a given system goes to zero, the
resonance point also goes to zero RPM. With the freewheel clutch, the
torsional frequency would go to zero whenever a torque reversal occurred For
that moment in time, the RPM would then be above the resonance point and the
engine would have no problem powering up into the operating RPM range. In
this regard,the BD-5 soft system with the freewheel clutch was a passive
dual frequency system, that functioned much like the active dual frequency
system used in the Continenta Tiara family of geared aircraft engines
FREEWHEEL CLUTCH - PARTIAL SOLUTION!
It must be understood that the freewheel clutch is only part of the solution
to the torsional resonance problem. Lowering the resonant point below the
starting RPM of the engine is the other essential part of the solution.
Simply installing a freewheel clutch in a system, where the torsional
resonance point is still in the operating range, may give the appearance of
success for the short term but not for the long term. In a low frequency,
torsionally soft system like that developed at Bede, the clutch chatter
frequency is low and the amplitude of rotational vibration is high, as the
RPM passes through the resonance point. Also, this occurs at the point when
the engine is just about to start and the energy level in the system is
quite low.
Exerpt from professional Rotorway operation and maintenance manual which
contains detailed step by step instructions. This photo shows a setup for
checking drive pulley run-out. A model publication for auto conversions
It is true, the loads can be very high at the resonance point, but this
occurs during a torque reversal which disengages the clutch and causes these
loads to go to zero. These characteristics are good for long clutch life,
which means a smaller clutch with a lower capacity is all that's required.
This saves both weight and cost. On the other hand, in a higher frequency,
torsionally hard system, the clutch chatter frequency is high and the
amplitude of rotational vibration is low. With this type of system, the
energy level is high. These characteristics tend to shorten clutch life. A
system of this type will require a clutch with a much higher capacity, since
torsional resonance is still a problem. The clutch and all other drive
system components will then be subject to limited life considerations. I
know of many who have tried using a freewheel clutch in a hard system as the
solution to the torsional resonance problem, but I do not know any who have
succeeded in the long term. For these reasons, I can not recommend the use
of a freewheel clutch with a torsionally hard system
161 photos and 10 drawings throughout the manual fully illustrate the
operation and maintenance of the RW133 engine. This picture suggests an
acceptable method for installing the engine in the airframe.
LATERAL VlBRATlON PROBLEMS
Although we had solved the torsional vibration problem at Bede, lateral
vibration problems still needed to be addressed. They had set up a test
stand in an old gutted mobile home beside the Bede shop and the engine
mechanic who was an expert in two-cycle engines was doing a lot of
experimenting to improve the engine One day he and his assistant were
working right beside the engine, in front of everything. The lower jackshaft
was turning about 6000 RPM and he was adjusting the carburetors when he
stepped aside slightly to get a wrench. All of a sudden there was a big
explosion and a hole appeared in the wall of the test stand building. The
lower jackshaft had broken loose from its rubber couplings and was hurled
like a missile through the wall It travailed almost to the next building,
nearly going through the wing of a Beech 18 and then burying itself in the
Kansas gumbo mud. The energy involved was just unbelievable. If the mechanic
had been standing where he had been just seconds before, he would have been
killed. Once the system was put back together, we ran it with a strobe light
on the jackstand. Immediately we saw that the lower jackshaft was not
maintaining its concentricity with the engine crank on the forward end nor
the sprocket on the aft end. The rubber couplings were too soft. The system
was modified to use spherical bearings on each end to locate the lower
jackshaft so it would not start this lateral vibration due to the
centrifugal force acting on the shaft. This change solved this problem.
There was also a lateral vibration problem with the lower sprocket. After
hooking up the strobe light, we found the lower sprocket support was putting
an undulating wave of vibration into the rear bulkhead of the engine
compartment. This explained why all the rivets on the outside skin at that
bulkhead were always coming loose. One day this vibration was particularly
bad and we had Burt come by to take at look it. When he saw it, he just
looked sort of shocked, turned whiteand went off mumbling something about
not letting Les see this because we'll never get him to fly it again. I
think it was at that point that he sort of gave up. This, along with the
many other problems with the engine seemed to be the last straw as far as
Burt was concerned. It was about a week or two later that both Burt and I
left Bede Aircraft. Before my last day, I turned the design responsibility
for the drive system over to our landing gear man, Al Thompson. I gave him
instructions on how to redesign the lower sprocket mount. He did a superb
job and the new mount solved the lateral resonance problem in the lower
sprocket.
ROTORWAY
While at RotorWay, B.J. Schramm assigned me the job of designing and
building a water dynamometer test stand for the RW 133 helicopter engine.
The engine was mounted vertically, just like it was in the helicopter The
dynamometer had a fairly heavy, high inertia rotor and was connected to the
engine by a drive shaft with two universal joints. This test stand was used
not only to develop the engine but to later fully test and run each
customer's engine before delivery. The test stand was designed and built
with a good appearance so that it could be used at Oshkosh and other
airshows to demonstrate the engine, showing the actual torque and horsepower
output to potential customers.
One day, while testing the engine, all hell broke loose. The jackshaft with
the two universals had broken off the engine and was flailing around,
shaking the test stand quite violently. If I had been anywhere close, I
would not be among the living today. We found that the upper part of the
crankshaft had broken off. The break was all crystalline and it had the
characteristics of a torsional fatigue failure. I mentioned to B.J. that the
crank material sure looked strange. That was when I found out the crank was
cast iron. The RotorWay engine was based on the Volkswagon engine but was
highly modified to produce the power required for the helicopter. Although
the volks engine had a forged crank, the RotorWay engine required a special
crank with a long stroke. Since the engine was only in the development
phase, B.J. used a cast iron crank. Soon aher this failure, B.J. had a new
forged crank developed to replace the cast iron crank. One thing for sure, a
cast iron crankshaft is not the best way to go, when trying to deal with
torsional vibration.
CLUTCH SPRING SOLUTION
B.J. got in touch with the people who manufactured the dynamometer and found
out that hooking a 4-cylinder engine to one of these dynos can be a problem.
Any engine that produces 2 power strokes per revolution is bad news when it
comes to torsional vibration, we were told. They suggested installing clutch
springs, from an automobile clutch assembly, between the engine and the
water dynamometer to solve this torsional problem. (This is the same idea
Lou Ross uses on his gear boxes.) We also put a guard around the jackshaft
so that if another failure occurred it would be contained I saw the test
stand a few years ago and it appeared to be in good shape and still in use.
The spring idea seemed to have worked out.
DRIVE SYSTEM CONFIGURATIONS
Any time a propeller is connected to an engine in any way other than
directly to the crank it would be wise to realize that torsional vibration
can be a problem. Basically, there are three propeller drive system
configurations:
1. Propeller speed-reduction unit alone
2. Propeller speed-reduction unit with a shaft drive
3. Propeller shaft drive alone
TORSIONAL RESONANCE FREQUENCY
* Where k is the torsional spring constant, i.e. the torque (T) required to
produce an angle of twist (a) of 1 radian in the shaft to which the
propeller is attached.
* Where d is the diameter of the propeller shaft.
* Where G is the shearing modulus of elasticity of the shaft material
* Where L is the length of the shaft in inches.
* Where f is the frequency of the torsional vibration.
* Where I is the mass moment of intertia at the propeller
From the above formula it can be seen that:
The torsional frequency can be lowered by:
1. Decreasing the diameter of the shaft(s) (d)
2. Decreasing the shearing modulus of elasticity of the shaft material (G)
3. Increasing the mass moment of intertia of the prop (l)
4. Increasing the length of the shaft (L)
The torsional frequency can be raised by:
1. Increasing the diameter of the shaft(s) (d).
2. Increasing the shearing modulus of elasticity of the shaft material (G).
3. Decreasing the mass moment of interia of the prop (l).
4. Decreasing the length of the shaft (L).
Torsional resonance frequency is affected, more or less, by the propeller,
engine crankshaft, connecting rods, pistons, and every part in between such
as a flywheel, gears, belts, and, to a lesser extent, the valve train and
accessories.
TYPES OF DRIVE SYSTEMS
1. A dampened system is one that uses a vibration damper to lower the
resonant loads to more acceptable levels, while leaving the torsional
resonance frequency within the operating RPM range of the engine. A dampened
system can be used with a propeller speed-reduction unit and/or a drive
shaft (i.e. Molt Taylor).
2. A hard drive is one that has a high torsional spring constant (k) and no
slop from the propeller through to the engine crankshaft (maximum rigidity).
The torsional problem is overcome strength and maximum stiffness. If a belt
is used it should be tensioned as per manufacturer's recommendations. (i.e.
Dave Blanton type bed drive system). A hard system becomes prohibitively
heavy when used with a shaft drive because of the high torsional loads
involved.
3. A soft system is one that has a low torsional spring constant (k) from
the propeller through to the engine crankshaft so as to move the torsional
resonance frequency below the operating RPM range and preferably below the
starting RPM of the engine. A soft system, using a propeller speed-reduction
unit alone (no driveshaft) with a sufficiently low torsional spring
constant, would be difficult to design because of space, weight, and
engineering limitations. A soft system with a drive shaft, if properly
designed and tested, has the potential of being the lightest and most
reliable of all the systems discussed (i.e. BD-5 belt/shaft drive system).
DESIGN CRITERIA RECOMMENDATIONS
1. The more cylinders the better!
2. Engine Crankshaft:
-1 st choice > forged
- 2nd choice> machined billet
- Not the best choice > cast iron
3. Joints in Rotating Parts:
- Use joints that transfer torque by faction where possible (i.e. shrink,
press &/or tapered fits)
- Splines are not the best choice in hard systems.
- If bolted joints (i e. flanged) are used, do not use the allowable bolt
shear strength to carry the engine torque through the joint. Instead, size
the bolts so that they can be tightened to produce sufficient bolt tension
so the engine torque can be transferred through the joint by the resulting
frictionbetween the flanges (Note: It would not be a ooodidea to have any
bolt threads in the vicinity on thejoint.)
4. System Slop:
- In a "hard system" (i.e. Dave Blanton hypesystem) avoid any slop in the
system Use a beltwith proper tension as per manufacturersrecommendations.
- In a 'soft system" (i.e. the BD-5 system) some slop can be tolerated. If a
toothed belt (i.e. HTD) is used, it can be run loose. Also, gears and
splines
are less critical (i.e. the Continental Tiara aircraft engine). If a silent
link type chain is used, chaint ension would be less cntical.
5. Torsional Spnng Constant of the System
- In a "hard system" (i.e. Dave Blanton type system) the main design
criteria should be to achieve a high torsional spring constant without
adding excessive weight. The torsional problem is overcome by brute
strength and maximum stiffness
- In a "soft system" (i e. the BD-5 system) the main design criteria should
be to achieve a low torsional spring constant while meeting the torque
requirements of the engine with a moderate safety factor. The torsional
spring constant should be low enough to move the torsional resonance
frequency below the starting RPM of the engine.
- The torsional spring constant can be lowered by decreasing the diameter of
the shaft(s), decreasing the shearing modulus of elasticity of the shaft
material, increasing the mass moment of inertia of the propeller and by
increasing the length of the shaft(s).
6. Freewheel Clutch:
- Use only a double cage, full phasing, sprag typec lutch. This type of
clutch works well with a "soft system".
- Roller and uncaged spring-loaded type freewheel clutches are not
recommended.
- It is not recommended to use a freewheel type clutch with a "hard system."
The higher energy level of resonance, in this type of system, will
eventually destroy the clutch, even though the engine RPM only passes
through the resonance when going up to or down from the normal operating
speed.
7. Cantilever Shafts:
- Mounting overhung belt sprockets or gears on cantilevered shafts should be
avoided, particularly on a "hard system".
- If a design requires an overhung sprocket, keep the offset and the belt
width to a minimum.
SUMMARY
BECOME FULLY INFORMED BEFORE TACKLING TORSIONALS! It would be advisable to
develop a good base of knowledge before becoming too involved in torsional
problems. Most intuitive solutions are the opposite of what should actually
be done when torsional resonance is involved. It is my hope that this
article will bring a degree of caution to experimenters and will encourage
them to seek out more knowledge on the subject before they jump in and waste
a lot of their time and money.
Demonstration of torsional resonance effects. A 2x4 representing the
inertia of a propeller is powered by a cordless drill motor through a 3/32
inch piano wire ("soft" system). One end of the rod is bent 90 degrees and
stapled securely to the wood. Energy is applied by short, rapid trigger
squeezes to simulate engine power pulses. Torsional effects are visual and
are heard from the slippage of the shaft in the chuck and torque reversal
clicking of the gears.
Message 38
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| Subject: | Long Sitting Rotax 582 |
--> Kolb-List message posted by: "Kolbdriver" <kolbdriver@mlsharp.com>
Folks,
It looks like I'm going to stay put for a while, I've landed in North
Central Oklahoma and need to get back to building. Big Lar and I started
about the same time, and I need to get busy so I can beat him in the air.
I have a 582 that has been sitting for approx 4 yrs. I've religiously kept
an equal mixture of seafoam, marvel mystery oil, opti 2, amsoil and penzoil
for 2cycle in the cyl and pulled the prop thru several times a week to keep
things lubed up. There seems to be good compression and no feeling of any
kind of binding.
Other than the obvious, replacing fuel pump and thoroughly cleaning the
carbs what should I be changing, cleaning etc. prior to start up.??
It does have an oil injection system.
Thanks,
Mike (MK III C, she's still with me, lost 2 wives and 3 jobs in the
process.)
Message 39
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|
| Subject: | Re: M-IIIC Drivers in Iowa |
--> Kolb-List message posted by: "Chuck Stonex" <cstonex@msn.com>
All of these stories from you former Challenger drivers are nice ..... I
just wish one of you would come help me get into this M-III I'm lookin' at.
Then I can be greatful that I bought a Kolb too!
--> Kolb-List message posted by: "Billie Futrell" <bill_joe@bellsouth.net>
I would just like to add a little to what Woody has just said about
a
Challenger. I was going to buy a Challenger before I bought my Kolb. A
friend of mine had a Challenger with the long wing so I flew with him for 3
hrs.I won't to tell you that was all I wanted. The first hr I was chasing
the thing all over the sky. You want to make a correction to the left, so
you give it aileron and it goes more to the right and then to the left. The
second hr I figured out that you had to fly with rudder, and a lot of that
and follow up with aileron. The only problem was before the hr was up I had
cramps it the calves of my legs so bad I could hardly use my the rudder
peddles. The third hr was not any better and when I left the field that day
I knew I did not want a Challenger.
I'm glad I go a kolb.
Bill Futrell MK111Xtra912
Do not archive
----- Original Message -----
From: "woody" <duesouth@govital.net>
Subject: Re: Kolb-List: M-IIIC Drivers in Iowa
> --> Kolb-List message posted by: "woody" <duesouth@govital.net>
>
> I told him that if something happened like getting unexpectedly airborn
> don't panic just fly the plane. He was a pilot but it still took him 3
> passes to figure out the right approach to land. No panic to get it back
> down just kept flying untill he got things figured out.
> Perhaps I am to used to Kolbs. Flying a Challenger was the most
> frighteneing experience I had had in years. I was not prepared for the
extra
> rudder needed to stop a turn. These planes need rudder or it won't get
out
> of a turn, The extra stiff rudder pedals and lack of concern about
rudders
> in the Kolb had me circling for 10 minutes (felt like hours) trying to
> figure out what to do next. Finally a hard kick to the rudders got some
> movement and I straightened up. Quite frightening. I tried another
> Challenger that day with the same result and need for rudder. Still could
> not keep the nose from wandering around. I do understand the aircraft
> exported to the UK have bigger rudders and may be less needy of rudder
> input.
> You're going to love the Kolb
>
>
> ----- Original Message -----
> From: "PATRICK LADD" <pj.ladd@btinternet.com>
> To: <kolb-list@matronics.com>
> Subject: Re: Kolb-List: M-IIIC Drivers in Iowa
>
>
> > --> Kolb-List message posted by: "PATRICK LADD"
<pj.ladd@btinternet.com>
> >
> > He didn't panic just remembered what I had told him>>
> >
> > Chuck,
> > What did you tell him?. I am about to change from Challenger to Kolb
and
> > have not flown a tail dragger since I sold the Thruster many years ago.
> > NB. The Challenger is not half as bad as this lot make out :-)
> >
> > Pat
> >
> >
> > --
> >
> >
> > --
> >
> >
>
>
Message 40
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| Subject: | VW reduction drive |
--> Kolb-List message posted by: "Richard Swiderski" <rswiderski@earthlink.net>
VW Kolbers:
I am installing a SPG-2 redrive on my 100hp 3 cyl chevy sprint turbo
engine. I was talking with the North American distributor today & he
commented that a guy in California put one on a VW using a simple aluminum
adapter plate. This gearbox is commonly used on 3 & 4 cylinder Suzuki
engines & Suburu engines up to 135 hp. They are imported out of Russia.
Below is contact info if you are interested. -Richard Swiderski
Regarding the SPG gearbox redrive the web site and contact is:
Vassili Tarakanov,
Aerospace Engineer
Canadian UL Instructor
Air Trikes Enterprises Manager
www.airtrikes.net
Phone/fax (514) 685-2856
Message 41
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| Subject: | Re: Long Sitting Rotax 582 |
--> Kolb-List message posted by: "Larry Bourne" <biglar@gogittum.com>
What ?? You mean there's another record un-setter in the crowd ?? I
just got in from a 3 1/2 week vacation to the *cool* wilds of British
Columbia, Canada tonight, and had been having great delusions of jumping
back into the Vamoose fray and getting it finished off. Hah ! ! ! At 7:30
PM it was still 108 outside. Digital thermometer in the house only goes to
99, and it took an hour and 5 minutes for it to drop to 98. This with an
oversized A/C unit. Now, at 9:15, it's down to 90 and feels positively
cool. :-( I now hae me doots about working on anything, but we'll see.
Slow Cookin' Lar. Do not Archive.
Larry Bourne
Palm Springs, CA
Building Kolb Mk III
N78LB Vamoose
www.gogittum.com
----- Original Message -----
From: "Kolbdriver" <kolbdriver@mlsharp.com>
Subject: Kolb-List: Long Sitting Rotax 582
> --> Kolb-List message posted by: "Kolbdriver" <kolbdriver@mlsharp.com>
>
> Folks,
>
>
> It looks like I'm going to stay put for a while, I've landed in North
> Central Oklahoma and need to get back to building. Big Lar and I started
> about the same time, and I need to get busy so I can beat him in the air.
>
>
> I have a 582 that has been sitting for approx 4 yrs. I've religiously
> kept
> an equal mixture of seafoam, marvel mystery oil, opti 2, amsoil and
> penzoil
> for 2cycle in the cyl and pulled the prop thru several times a week to
> keep
> things lubed up. There seems to be good compression and no feeling of any
> kind of binding.
>
>
> Other than the obvious, replacing fuel pump and thoroughly cleaning the
> carbs what should I be changing, cleaning etc. prior to start up.??
>
> It does have an oil injection system.
>
>
> Thanks,
>
> Mike (MK III C, she's still with me, lost 2 wives and 3 jobs in the
> process.)
>
>
>
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