Today's Message Index:
----------------------
1. 02:50 AM - Re: > Re: would a full feathering propeller help? (netmaster15@juno.com)
2. 06:51 AM - Re: > Re: would a full feathering propeller help? (cjpilot710@aol.com)
3. 07:04 AM - Re: Samold, reminiscing (Roger Kemp M.D.)
4. 07:18 AM - West Bend rooms (Craig Payne)
5. 07:35 AM - Re: > Re: would a full feathering propeller help? (Elmar Hegenauer)
6. 07:43 AM - Re: Hard starting CJ (CZ)
7. 09:53 AM - Re: > Re: would a full feathering propeller help? (Brian Lloyd)
8. 09:53 AM - Re: would a full feathering propeller help? (Brian Lloyd)
9. 01:04 PM - Re: Prop's (Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E)
10. 01:44 PM - Re: L/D again (Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E)
11. 02:05 PM - Re: "Over Square, back loading, detuning, underboost-etc. (Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E)
12. 02:23 PM - Re: Fw: L/D redux (Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E)
13. 05:25 PM - Re: West Bend rooms (Forrest Johnson)
14. 08:02 PM - Re: would a full feathering propeller help? (Craig Winkelmann, CFI)
15. 09:14 PM - Replacement batteries` (Mark Davis)
16. 09:21 PM - Re: Fw: L/D redux (Walter Lannon)
Message 1
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| Subject: | Re: > Re: would a full feathering propeller help? |
Elmar, Of course it would cut the drag of the windmilling prop; the pro
blem is that a full feathering prop would be so heavy that it would sign
ificantly alter the CG by its forward moment. Remember , with a "dead"en
gine there has to be an electrical motor to drive the blades into the fe
athering range. This adds to the weight of the full feathering prop. If
it were so simple it would have been done already. Full feathering props
are both heavy and more expensive
Cheers,
Cliff Umscheid--
"Elmar Hege
nauer" <elmar.hegenauer@telus.net> wrote:itsforward moment
.net>
Thanks Brian, I've meant
in a case of emergency
with a dead engine and
a windmilling propeller.
cheers
Elmar
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Message 2
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| Subject: | Re: > Re: would a full feathering propeller help? |
In a message dated 5/5/2008 5:51:57 A.M. Eastern Daylight Time,
netmaster15@juno.com writes:
The drag of a wind milling prop is enormous. A B-17 with just one wind
milling prop can just barely maintain altitude at gross weight. With the prop
feathered, its almost a "non issue". On the B-24 it is a serious situation at
any weight. The old Piper Apache was the same (in actuality you really got a
decent glide out of it with one engine feathered).
In reality yes, a full feathering prop would be heavier but not that much.
One only need to look at the feathering systems on the light twins. The
difference in the prop hub would not be so much as to mass but to the gearing
inside. A feathering pump might add 10 lbs. I am willing to bet that there is
already a full feathering prop for the M-14p out there somewhere. I believe
Yak built a high wing twin that used M-14p engines. You are correct - full
feathering prop can be more expensive.
There are some hangar stories of how some who have lost an engine, had the
presents of mind, to pull up to near a stall and be able to get the prop
stopped and "soar" their airplane home. Well maybe, but I have seen it done at
airshows and it is surprising the vast difference in gliding ability of the
airplane. You might want to conceder doing that if you are already high and
want more time and distance before the inevitable.
The full feathering prop was designed because of the advent of the multi
engine airplane. Multi engines were first put on aircraft to increase payload.
It was recognized early that engines quit and besides the asymmetrical trust
the drag of the wind milling engine was enormous. Hence the full feathering
prop. Can you imagine try to coats a Goliath bomber of WW1 to fly with an
engine wind milling?
So the question is - if the out come is no different - why put expensive and
complicated system on the airplane?
Jim "Pappy" Goolsby
Elmar, Of course it would cut the drag of the windmilling prop; the problem
is that a full feathering prop would be so heavy that it would significantly
alter the CG by its forward moment. Remember , with a "dead"engine there has
to be an electrical motor to drive the blades into the feathering range.
This adds to the weight of the full feathering prop. If it were so simple it
would have been done already. Full feathering props are both heavy and more
expensive
Cheers,
Cliff Umscheid--
"Elmar Hegenauer"
<elmar.hegenauer@telus.net> wrote:itsforward moment
Thanks Brian, I've meant
in a case of emergency
with a dead engine and
a windmilling propeller.
cheers
Elmar
**************Wondering what's for Dinner Tonight? Get new twists on family
favorites at AOL Food.
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Message 3
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| Subject: | Samold, reminiscing |
. Low compression ratios and supercharging mean you can run at low RPM and
high MAP and maintain high MAP at altitude without stressing the engines,
thereby
"driving the prop" and relieving inertial loads. The only way the prop can
drive the engine is "high" speed, high RPM (low pitch)/low MAP settings,
i.e, speed-brake operations. Eh?
Jerry Painter
CFI, Chief (and only) Pilot, A&P, Permanent Latrine Orderly & c.
Wild Blue Aviation
425-876-0865
wild.blue@verizon.net
www.FlyWBA.com
Great dissertation. So it all boils down to the last 6 sentences of the
email you sent out on Sat. correct?
We are loading up our engines when push the prop lever to 100% (or 80%) and
pull the MAP lever to 0 mmHG (idle) in an effort to slow the aircraft down.
So my initial statement that low pitch and low manifold pressure using the
prop as a speed brake was/is correct.
Not smash the dead horse to pulverized dust here but I think I have done so.
Doc
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Osh-50 Attendees
Gathering from stats so far, plenty of folks are coming to Oshkosh but I only have
8 rooms booked at the Americinn in West Bend. Does this mean y'all ain't coming
or just haven't made the reservation yet?
Inquiring minds want to know. I need a head count please, to MY email and not
the 'list.
West Bend Americinn: 262-334-0307 book under "RedStars". RPA events/Pre-Oshkosh
for event registration.
Craig Payne
cpayne@joimail.com
Message 5
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| Subject: | Re: > Re: would a full feathering propeller help? |
Please go on following website
Page No. 6
http://www.mt-propeller.de/pdf/mt_eur_i.pdf
cheers
Elmar
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Message 6
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| Subject: | Re: Hard starting CJ |
Hello,
What turned out to be the problem with your starter?
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=181232#181232
Message 7
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| Subject: | Re: > Re: would a full feathering propeller help? |
On May 5, 2008, at 2:46 AM, netmaster15@juno.com wrote:
> Elmar, Of course it would cut the drag of the windmilling prop; the
> problem is that a full feathering prop would be so heavy that it
> would significantly alter the CG by its forward moment. Remember ,
> with a "dead"engine there has to be an electrical motor to drive the
> blades into the feathering range. This adds to the weight of the
> full feathering prop. If it were so simple it would have been done
> already. Full feathering props are both heavy and more expensive
>
Electric motor? Not since the 40's. Try one with a simple hydraulic
accumulator. There just isn't that much difference in weight.
Brian Lloyd 3191 Western Drive
brianl AT lloyd DOT com Cameron Park, CA 95682
+1.916.367.2131 (voice) +1.270.912.0788 (fax)
PGP key ID: 12095C52A32A1B6C
PGP key fingerprint: 3B1D BA11 4913 3254 B6E0 CC09 1209 5C52 A32A 1B6C
Message 8
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| Subject: | Re: would a full feathering propeller help? |
On May 4, 2008, at 9:48 PM, Elmar Hegenauer wrote:
> >
>
>
> I've read all the postings regarding
> the GLIDING RANGE, thank you very much
> everybody.
> Now here comes my question: Would a
> full feathering propeller improve the
> engine off landings characteristics of
> a Nanchang or a YAK?
Many of the Harmon Rocket aircraft flying out there have full
feathering props. The reason is that someone just pulled the engine
and prop off of an Aztec and used it.
Brian Lloyd 3191 Western Drive
brianl AT lloyd DOT com Cameron Park, CA 95682
+1.916.367.2131 (voice) +1.270.912.0788 (fax)
PGP key ID: 12095C52A32A1B6C
PGP key fingerprint: 3B1D BA11 4913 3254 B6E0 CC09 1209 5C52 A32A 1B6C
Message 9
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Thanks for explaining that both props are the same in this regard Walt.
If you will re-read your post you will see that it mentioned the
transfer tube as a possible source but did not give any details on the
crush washer and where it was and the fact that it can not be reused
without the strong chance of it leaking again. If you will re-read my
post you will see that I just was trying to add more detail to your
already excellent comments.
By the way, Doug Sapp has the seals on hand for anyone who needs them.
Bon Chance,
Mark
-----Original Message-----
From: owner-yak-list-server@matronics.com
[mailto:owner-yak-list-server@matronics.com] On Behalf Of Walter Lannon
Sent: Friday, May 02, 2008 22:18
Subject: Re: Yak-List: Prop's
Mark;
The J9 G1 and the V530 are absolutely identical in this respect. If you
would re-read my post you will find that I did refer to the transfer as
a third potential leak source.
Cheers;
Walt
----- Original Message -----
From: "Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E"
<mark.bitterlich@navy.mil>
Sent: Friday, May 02, 2008 11:33 AM
Subject: RE: Yak-List: Prop's
Point,
> MALS-14 64E" <mark.bitterlich@navy.mil>
>
> Not sure whether the CJ is identical to the M-14 in this regard, but
on
> the latter, there is a third source for the problem that you detail
(oil
> getting into the hub and diluting the grease to the point where it
makes
> it out past the prop shaft seals) and that is the transfer tube seal
> itself. This is a crush washer type deal that is installed
"underneath"
> the threaded portion of the transfer tube that screws into the motor
and
> then sticks out and provides the oil path to get into the hub itself.
A
> lot of people like to try and use these seals over again after pulling
> them out for inspection. That doesn't work real well.
>
> Good luck,
>
> Mark Bitterlich
>
>
> -----Original Message-----
> From: owner-yak-list-server@matronics.com
> [mailto:owner-yak-list-server@matronics.com] On Behalf Of Walter
Lannon
> Sent: Friday, May 02, 2008 12:29
> To: yak-list@matronics.com
> Subject: Re: Yak-List: Prop's
>
>
> That could be a normal condition after overhaul if excess grease was
> left outside of the blade seal area. Clean it and recheck. Is it both
> blades?
> If it continues you need to know whether it is grease or oil. Oil can
> only come from the pitch change unit or transfer tube and will
initially
> show up leaking from the front of the hub at the "spinner" cap.
> Eventually it will fill the hub, dilute the grease and leak past the
> grease seals. The usual source is the two pitch change seals which
would
> be replaced at overhaul.
> Who did your overhaul?
>
> Walt
> ----- Original Message -----
> From: "CJcanuck" <m_kirk69@hotmail.com>
> To: <yak-list@matronics.com>
> Sent: Friday, May 02, 2008 7:51 AM
> Subject: Yak-List: Prop's
>
>
>>
>> Hey All!
>>
>> I've just reinstalled my prop after having it overhauled and
> repainted.
>> After shutting down from the first run we had a small amount of
grease
>
>> running down each prop blade from the hub The flow is symmetrical as
> far
>> as I can tell. Having brand new seals and all I'm wondering if this
is
>
>> 'normal' or if there are other issues at work here.
>>
>> On a related issue, I'm keen to contact the company in Australia that
> is
>> selling the prop spinners and some of the speed mods. Anyone have
> contact
>> info?
>>
>> Thanks!
>>
>> Mike Kirk
>>
>>
>>
>>
>> Read this topic online here:
>>
>> http://forums.matronics.com/viewtopic.php?p=180682#180682
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>
>
>
Message 10
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Brian, you can't even hold a feather.....
Mark Bitterlich
-----Original Message-----
From: owner-yak-list-server@matronics.com [mailto:owner-yak-list-server@matronics.com] On Behalf Of Brian Lloyd
Sent: Saturday, May 03, 2008 20:14
Subject: Re: Yak-List: L/D again
On May 3, 2008, at 11:42 AM, Jerry Painter wrote:
> <wild.blue@verizon.net>
>
> Budd--
You think like me. You just don't piss other people off as much as I do doing it.
;-)
Amen to everything you said.
--
Brian Lloyd 3191 Western Drive
brian HYPHEN 1927 AT lloyd DOT com Cameron Park, CA 95682
+1.916.367.2131 (voice) +1.270.912.0788 (fax)
I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupry
PGP key ID: 12095C52A32A1B6C
PGP key fingerprint: 3B1D BA11 4913 3254 B6E0 CC09 1209 5C52 A32A 1B6C
Message 11
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| Subject: | "Over Square, back loading, detuning, underboost-etc. |
Jim, just a comment. I am not disagreeing with anything you have said
or the quotes from others with far more round engine time than my own.
That said, the M-14 has been flying in Unlimited Aerobatic Competition
for years. I happen to have the privilege of working with (and on) the
M-14 engines mounted in a few of the most heavily and most outrageously
flown aircraft in this country. In most every M-14 engine I have had
experience with, the failure items usually consist of front engine seals
(gone bad from extreme loading in gyroscopic maneuvers... Looks like a
prop seal, but isn't!) some cracked piston rings, a lot of #2 cylinder
low compression gripes, many mag gripes, bent rods from oil in the
cylinders, but not one ... Not one single occasion of bad internal
bearings or any kind of silver in the screens. These engines are
usually flown with two power settings. WFO, and yanked to zero. The
only "normal" engine use is flying to and from the locations of the
competitions or air shows. Possibly we are not into the range of total
operating hours to see this kind of wear and failure yet? Most of the
aerobatic guys I know change engines at around 1000 hours even if they
are running OK.
Point is, I understand and concur with every word you have said, and
like yourself, I am wondering if there is anything different or special
about the M-14, because it sure is not failing like the American made
round engines would if treated the same way. Further, I believe that
the M-14 weighs less than any other American made engine for the
horsepower it produces. It is also 'geared' and turns higher RPM than
most made American Radials too.
I believe someone ought to contact Russian Master Mechanic Vladimir
Yastremski and ask him about this issue. I honestly believe he would
know even more than Jill or George about the matter.
Just a thought.
Mark Bitterlich
-----Original Message-----
From: owner-yak-list-server@matronics.com
[mailto:owner-yak-list-server@matronics.com] On Behalf Of
cjpilot710@aol.com
Sent: Saturday, May 03, 2008 22:14
Subject: Yak-List: "Over Square, back loading, detuning, underboost-etc.
There has been several things mentioned here about the necessity or not
of staying "over square". Some are not quite sure at what is happening.
I have "lived" with this a good many years and I know that big radials
will not last long if you treat them poorly. In fact one of the reasons
the bombers I fly stay "in business" is because of the way we fly the
engines. Averaging around 300 plus hours a year per airplane - that's
equates to about 600 takeoff and landings a year per airplane. If we
flew them the way the USAAF did, we'd be changing engines every couple
of months. Usually we change one engine per year per airplane. Here is
how the problem was written up in Warbird Notes #3 in March 1994, by
R.L. Sohn. It is probably the best explanation I've ever seen written.
"Now the cause which we want discuss in this bulletin. This happens
when the pilot pulls the throttle back to a very low MP. --------- Under
normal conditions the master rod thrust bearing is loaded against the
crankshaft from multiplicity of direction as all the pistons progress
through their assigned firing order. Remember that all the other
connecting rods are linked to this one master rod and the pressures on
this master rod journal are the constantly changing resultant of all the
pressures exerted by these pistons. The crankshaft is drilled on the
thrust side allowing oil access to this area when under power. The heat
is carried away with the oil flow. No oil hole is drilled on the
anti-thrust side, it's not considered necessary since the hole the
thrust side provides constant lubrication from pressurized oil flowing
around the bearing. If this series of alternating forces is severely
disturbed by a large reduction in MP then the propeller in effect is
turning the engine. It might be helpful here to visualize the unloaded
pistons trying to throw themselves out the top of the cylinders. In
this case the load is continuously applied to this one (anti-thrust
side) area of the master rod journal where no oil hole is located. In
short order this "squeeze play" situation causes oil (lubrication and
cooling ) starvation resulting in failure to dissipate the frictional
heat. This rapidly progresses from overheating to self destruction. In
some cases during tear down the bleed holes have been found wiped full
of silver metal from the multi-layered plating of the master rod
bearing"
The Wright can stand up a little better the Pratts because the they have
more master rod bearing area. The journal diameter of the 1820 is about
3 1/4" as compared to the 1830's 2 5/8". Both have virtually the same
displacement.
Comparing the M-14? There no doubt that the forces and situation is the
same. However I do not know the oiling of the M-14. Jill could
elucidate better than I on that. I think if you compare engine size to
horsepower (I don't how to arthritically do that) I believe you'd find
the M-14 is "beefier" for its HP. I know that I fly my M14 the same way
I do the Pratts and Wrights.
Jim "Pappy" Goolsby
________________________________
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Message 12
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Walt would you please explain what you mean by "centrifugal piston loading" ??
I am not a radial engine expert, but I would think the term would be the same,
and for the same reasons, as regular V-8 racing engines, which I do have a lot
of expereince with. In the world I come from, we call it "piston speed", and
of course it is related to the stroke and the RPM of the engine. If we are
on the same page of music here, the worry with the race engine I work with comes
from the exact failure areas you speak of, which is why the emphasis on light
weight pistons, and is also why you can easily build a 327 Chevy to turn 9000
RPM, but why there is much more load on a 454 doing the same thing... Longer
stroke (and thus higher piston speed) and heavier pistons in the 454. That
said, whether the engine is loaded or unloaded in my training does not make any
difference. When the piston reaches the end of it's travel and has to reverse
direction, there is tremendous forces applied all over the place, but piston
pin, piston, and rod itself are the biggest areas of concern.
To repeat and simplify, the "big force" involved is simply when the piston reaches
the top and reverses direction. The more it weighs and the faster it is going
when this happens means "more force".
What I fail to understand is why this force would be larger or smaller when the
engine is producing power, or not producing power?
Could you please explain what you mean by: "if you run significantly reduced power
at the max. RPM for any length of time there is the possibility of damage
due to the increased centrifugal loading of the piston and pin."
What increased loading are you talking about assuming the engine is still running
under maximum RPM limits? Why is there more loading with power off, than power
on?
Mark Bitterlich
-----Original Message-----
From: owner-yak-list-server@matronics.com [mailto:owner-yak-list-server@matronics.com] On Behalf Of Walter Lannon
Sent: Saturday, May 03, 2008 22:55
Subject: Re: Yak-List: Fw: L/D redux
You all are getting me confused! High RPM, low MP, overspeed??, contact points
for the master rod bearing??, direct drive, geared drive. Where to
begin---------
At some point on approach you will reduce the power and, if you follow standard
practice, will move the prop control to High RPM. If you have reduced power enough
you will not see any RPM increase because the governor has sensed an underspeed
condition and has already moved the blades to full fine.
The only reason for moving the prop control is to set up for a possible emergency
go-around.
Therefore the prop is always in the highest drag condition on a normal landing.
There can be no "overspeed" since with increasing power the governor will limit
RPM to the max. setting. However, if you run significantly reduced power at
the max. RPM for any length of time there is the possibility of damage due to
the increased centrifugal loading of the piston and pin. That is the primary reason
for avoiding that scenario.
There is no such thing as a "contact point" on the master rod bearing, unless it
is totally worn out and nearing failure. That is the function of oil. It's
main purpose is to ensure there is NO contact.
The master rod bearing (and the inner bearing end of each link rod) is pressure
lubricated from the crank journal cavity on ALL radial engines.
Whether geared or direct drive makes zero difference in this area.
It is possible that the M14 is more tolerant of centrifugal piston loading than
P&W or Curtis Wright engines simply due to the small piston size.
Cheers;
Walt
----- Original Message -----
From: "Roger Kemp M.D." <viperdoc@mindspring.com>
Sent: Saturday, May 03, 2008 2:42 PM
Subject: RE: Yak-List: Fw: L/D redux
> <viperdoc@mindspring.com>
>
> Brian,
> Thanks for enlightening me. I was not thinking about the direct drive of
> the
> P&Ws verses the geared drive of the M-14. Don't quote me but I believe the
> M-14 master crank rod bearing has its own oil journal. I ran across that
> as
> I was researching the oil supply of the prop governor for an engine
> vibration occurring right at Vref.
> It can be found in the diagrams of the M-14 engine manual.
> Doc
>
> -----Original Message-----
> From: owner-yak-list-server@matronics.com
> [mailto:owner-yak-list-server@matronics.com] On Behalf Of Brian Lloyd
> Sent: Saturday, May 03, 2008 11:32 AM
> To: yak-list@matronics.com
> Subject: Re: Yak-List: Fw: L/D redux
>
>
>
> On May 3, 2008, at 5:32 AM, Roger Kemp M.D. wrote:
>
>> <viperdoc@mindspring.com
>
>> >
>>
>> Jerry,
>> I thought that by pushing the pitch to full forward on the prop at
>> cruise
>> manifold setting ( 600-750-800) and then pulling the MAP back to use
>> the
>> prop as a speed brake would put you at risk for over speeding the
>> engine?
>
> Not if your prop governor is working properly.
>
>> Now you have set up a situation where the prop is driving the engine
>> not the
>> engine driving the prop. Correct me if I'm wrong.
>
> Yes, that is the case. But remember, when the RPM increases above the
> set-point, the governor will drive the prop toward course pitch (lower
> RPM). This reduces the angle-of-attack on the prop blades and they
> will produce less lift (turning force). It is also why you get a
> longer glide with the prop set to low RPM -- the prop is not taking as
> much energy from the airframe to turn the engine.
>
>> The translated 1990 RU manual that I have says for approaches set
>> the pitch
>> at 80% and 400 mmHG on the advance (MAP lever)for the 52. I
>> generally fly
>> 70% and 400 mmHg or less (MAP) in the 50 as needed. I know at times
>> being at
>> say 70-80% and 750-800 mmHG chasing down someone (lead or an
>> adversary) then
>> pulling the MAP lever to idle to avoid overshoot is like having a
>> big speed
>> brake out there! The but is in the huge change in pitch of the
>> engine. I
>> always wondered if I was overstressing the reduction gears or the
>> shaft
>> itself. Honestly I would rather go idle boards (deploy the speed
>> brakes)
>> than use my engine as the speed brake.
>
> Well, think about it Roger. Do you think that the prop can generate
> more torque turning the engine or the engine generate more torque
> turning the prop? I think you will find that the torque is at its peak
> when the engine is producing maximum power. That means that the
> overall stresses on the gearbox will be less when the power is pulled
> back.
>
>> I know a couple of old 17 drivers along with a 47 driver and T-28
>> driver/maintenance officer at the airport. I will ask then their
>> take today
>> at our fly-in. If the weather permits!
>
> Now here is something you need to be careful about. You cannot assume
> that the M14 or Huosai should be operated the same way that the big
> Pratts and Wrights should be operated. As I understand it, the crank
> on the Pratts and Wrights have just one oil journal and it feeds oil
> to the contact point for the master rod bearing when the rod is
> turning the crank. When the prop is turning the crank then the crank
> is turning the master rod which changes the contact point. This can
> lead to under-lubrication of the master rod bearing. That is why they
> admonish you to never let the prop drive the engine in the Wrights and
> Pratts.
>
> So that brings up the question of how the M14 and Huosai engines get
> oil to the master rod bearing. If there are oil journals to ensure
> proper lubrication of the master rod bearing when the prop is turning
> the engine then there is no reason to worry about doing damage to the
> engine when you pull the throttle back to idle. Given that the M14 is
> intended for aerobatic use, I suspect it *does* have proper
> lubrication when the prop is driving the engine, hence the lack of an
> warnings about the prop driving the engine in the manuals.
>
> But this is only supposition on my part. Only someone who really knows
> the engine can tell for sure.
>
>
> --
> Brian Lloyd 3191 Western Drive
> brian HYPHEN 1927 AT lloyd DOT com Cameron Park, CA 95682
> +1.916.367.2131 (voice) +1.270.912.0788 (fax)
>
> I fly because it releases my mind from the tyranny of petty things . . .
> - Antoine de Saint-Exupry
>
> PGP key ID: 12095C52A32A1B6C
> PGP key fingerprint: 3B1D BA11 4913 3254 B6E0 CC09 1209 5C52 A32A 1B6C
>
>
>
Message 13
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| Subject: | Re: West Bend rooms |
I am staying at the hotel. I dont think they know who is Red Star!
----- Original Message -----
From: Craig Payne
To: yak-list
Sent: Monday, May 05, 2008 9:16 AM
Subject: Yak-List: West Bend rooms
Osh-50 Attendees
Gathering from stats so far, plenty of folks are coming to Oshkosh but
I only have 8 rooms booked at the Americinn in West Bend. Does this mean
y'all ain't coming or just haven't made the reservation yet?
Inquiring minds want to know. I need a head count please, to MY email
and not the 'list.
West Bend Americinn: 262-334-0307 book under "RedStars". RPA
events/Pre-Oshkosh for event registration.
Craig Payne
cpayne@joimail.com
Message 14
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| Subject: | Re: would a full feathering propeller help? |
IF the prop will feather, it will produce less drag and should increase glide.
However, depending on the failure, the prop may not feather or the prop may not
be windmilling.
In addition, I teach students to pitch up when I simulate an engine failure. You
can translate the forward speed above best glide into altitude. An with no
engine, altitude is your friend. Most students will start looking for a place
to land and just maintain their altitude and bleed off the speed. You may only
get 100 feet or so, but it is more than you had before and is a good use of
the energy.
For what it is worth,
Craig
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=181404#181404
Message 15
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| Subject: | Replacement batteries` |
It's time for new batteries in my YAK. It has the BB EVP20-12 batteries
from when I bought it. I have no idea where a BB Battery dealer is in
my area. Does anyone have a replacement number for an Interstate,
Optima or Yuasa battery or other recommendations?
Thanks,
Mark Davis
N44YK
Message 16
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| Subject: | Re: Fw: L/D redux |
Mark; See comments below
> MALS-14 64E" <mark.bitterlich@navy.mil>
>
> Walt would you please explain what you mean by "centrifugal piston
> loading" ?? I am not a radial engine expert, but I would think the term
> would be the same, and for the same reasons, as regular V-8 racing
> engines, which I do have a lot of expereince with. In the world I come
> from, we call it "piston speed", and of course it is related to the stroke
> and the RPM of the engine. If we are on the same page of music here, the
> worry with the race engine I work with comes from the exact failure areas
> you speak of, which is why the emphasis on light weight pistons, and is
> also why you can easily build a 327 Chevy to turn 9000 RPM, but why there
> is much more load on a 454 doing the same thing... Longer stroke (and thus
> higher piston speed) and heavier pistons in the 454. That said, whether
> the engine is loaded or unloaded in my training does not make any
> difference. When the piston reaches the end of it's travel and has to
> reverse direction, there is tremendous forces applied al!
> l over the place, but piston pin, piston, and rod itself are the biggest
> areas of concern.
>
> To repeat and simplify, the "big force" involved is simply when the piston
> reaches the top and reverses direction. The more it weighs and the faster
> it is going when this happens means "more force".
To be honest I was desperately scratching for a descriptive word here for
the forces you have just described. Maybe sudden deceleration would have
been better.
I learned about this teaching myself aerobatics in a PT26 with a Ranger
engine and of course a fixed pitch prop. (In the early 1950's there were no
aerobatic instructers around, in fact aerobatic seemed to be a dirty word).
To get enough speed for an immellman or hammerhead it was necessary to keep
reducing power in the dive in order to stay just under red line RPM. ( this
was not the worlds best aerobatic mount).
Started pulling cylinders due to low compression and found all six pistons
cracked from the pin bore. Turned out to be an early model engine that did
not incorporate piston pin plugs. The pins were being deformed by the force
reversal causing the pistons to fail.
> What I fail to understand is why this force would be larger or smaller
> when the engine is producing power, or not producing power?
I think the reason is manifold pressure or maybe more accurately brake mean
effective pressure (BMEP). The piston is "cushioned" on the
compression/power cycle by combustion forces and on the exhaust/intake cycle
by exhaust expulsion and, just before the piston reaches TDC, the input of
pressurized air/fuel mixture from the manifold.
With the larger radial engines an excess of manifold pressure (over square)
is necessary to provide this cushion. As an example the P&W R1340 numbers
are - T.O. (600 HP) 2250RPM & 36"MP, 5 min limit - Rated Power (550HP) 2200
RPM & 32.5" MP, no limit - Typical cruise setting - (55%- 300HP) 1800 RPM &
26"MP.
Jim Goolsby sent a very informative post on this subject with an insert from
Mr. R Sohn describing the effect of these forces on the master rod bearing
if the "cushion" is not maintained.
I believe he is absolutely correct.
> Could you please explain what you mean by: "if you run significantly
> reduced power at the max. RPM for any length of time there is the
> possibility of damage due to the increased centrifugal loading of the
> piston and pin."
>
> What increased loading are you talking about assuming the engine is still
> running under maximum RPM limits? Why is there more loading with power
> off, than power on?
Covered above, I think.
The M14P is impressive. Even with the very small piston the load reversal at
2900 RPM must be awesome. That it would stand up to handling the throttle
like an ON- Off switch is mind boggling.
Aside for Pappy from a P&W devotee;
The reason the R1830 has a smaller master rod bearing is because it has TWO
of them and much smaller pistons flailing around.
Cheers,
Walt
> Mark Bitterlich
>
>
> -----Original Message-----
> From: owner-yak-list-server@matronics.com
> [mailto:owner-yak-list-server@matronics.com] On Behalf Of Walter Lannon
> Sent: Saturday, May 03, 2008 22:55
> To: yak-list@matronics.com
> Subject: Re: Yak-List: Fw: L/D redux
>
>
> You all are getting me confused! High RPM, low MP, overspeed??, contact
> points for the master rod bearing??, direct drive, geared drive. Where to
> begin---------
>
> At some point on approach you will reduce the power and, if you follow
> standard practice, will move the prop control to High RPM. If you have
> reduced power enough you will not see any RPM increase because the
> governor has sensed an underspeed condition and has already moved the
> blades to full fine.
> The only reason for moving the prop control is to set up for a possible
> emergency go-around.
> Therefore the prop is always in the highest drag condition on a normal
> landing.
>
> There can be no "overspeed" since with increasing power the governor will
> limit RPM to the max. setting. However, if you run significantly reduced
> power at the max. RPM for any length of time there is the possibility of
> damage due to the increased centrifugal loading of the piston and pin.
> That is the primary reason for avoiding that scenario.
>
> There is no such thing as a "contact point" on the master rod bearing,
> unless it is totally worn out and nearing failure. That is the function
> of oil. It's main purpose is to ensure there is NO contact.
>
> The master rod bearing (and the inner bearing end of each link rod) is
> pressure lubricated from the crank journal cavity on ALL radial engines.
> Whether geared or direct drive makes zero difference in this area.
>
> It is possible that the M14 is more tolerant of centrifugal piston loading
> than P&W or Curtis Wright engines simply due to the small piston size.
>
> Cheers;
> Walt
>
>
> ----- Original Message -----
> From: "Roger Kemp M.D." <viperdoc@mindspring.com>
> To: <yak-list@matronics.com>
> Sent: Saturday, May 03, 2008 2:42 PM
> Subject: RE: Yak-List: Fw: L/D redux
>
>
>> <viperdoc@mindspring.com>
>>
>> Brian,
>> Thanks for enlightening me. I was not thinking about the direct drive of
>> the
>> P&Ws verses the geared drive of the M-14. Don't quote me but I believe
>> the
>> M-14 master crank rod bearing has its own oil journal. I ran across that
>> as
>> I was researching the oil supply of the prop governor for an engine
>> vibration occurring right at Vref.
>> It can be found in the diagrams of the M-14 engine manual.
>> Doc
>>
>> -----Original Message-----
>> From: owner-yak-list-server@matronics.com
>> [mailto:owner-yak-list-server@matronics.com] On Behalf Of Brian Lloyd
>> Sent: Saturday, May 03, 2008 11:32 AM
>> To: yak-list@matronics.com
>> Subject: Re: Yak-List: Fw: L/D redux
>>
>>
>>
>> On May 3, 2008, at 5:32 AM, Roger Kemp M.D. wrote:
>>
>>> <viperdoc@mindspring.com
>>
>>> >
>>>
>>> Jerry,
>>> I thought that by pushing the pitch to full forward on the prop at
>>> cruise
>>> manifold setting ( 600-750-800) and then pulling the MAP back to use
>>> the
>>> prop as a speed brake would put you at risk for over speeding the
>>> engine?
>>
>> Not if your prop governor is working properly.
>>
>>> Now you have set up a situation where the prop is driving the engine
>>> not the
>>> engine driving the prop. Correct me if I'm wrong.
>>
>> Yes, that is the case. But remember, when the RPM increases above the
>> set-point, the governor will drive the prop toward course pitch (lower
>> RPM). This reduces the angle-of-attack on the prop blades and they
>> will produce less lift (turning force). It is also why you get a
>> longer glide with the prop set to low RPM -- the prop is not taking as
>> much energy from the airframe to turn the engine.
>>
>>> The translated 1990 RU manual that I have says for approaches set
>>> the pitch
>>> at 80% and 400 mmHG on the advance (MAP lever)for the 52. I
>>> generally fly
>>> 70% and 400 mmHg or less (MAP) in the 50 as needed. I know at times
>>> being at
>>> say 70-80% and 750-800 mmHG chasing down someone (lead or an
>>> adversary) then
>>> pulling the MAP lever to idle to avoid overshoot is like having a
>>> big speed
>>> brake out there! The but is in the huge change in pitch of the
>>> engine. I
>>> always wondered if I was overstressing the reduction gears or the
>>> shaft
>>> itself. Honestly I would rather go idle boards (deploy the speed
>>> brakes)
>>> than use my engine as the speed brake.
>>
>> Well, think about it Roger. Do you think that the prop can generate
>> more torque turning the engine or the engine generate more torque
>> turning the prop? I think you will find that the torque is at its peak
>> when the engine is producing maximum power. That means that the
>> overall stresses on the gearbox will be less when the power is pulled
>> back.
>>
>>> I know a couple of old 17 drivers along with a 47 driver and T-28
>>> driver/maintenance officer at the airport. I will ask then their
>>> take today
>>> at our fly-in. If the weather permits!
>>
>> Now here is something you need to be careful about. You cannot assume
>> that the M14 or Huosai should be operated the same way that the big
>> Pratts and Wrights should be operated. As I understand it, the crank
>> on the Pratts and Wrights have just one oil journal and it feeds oil
>> to the contact point for the master rod bearing when the rod is
>> turning the crank. When the prop is turning the crank then the crank
>> is turning the master rod which changes the contact point. This can
>> lead to under-lubrication of the master rod bearing. That is why they
>> admonish you to never let the prop drive the engine in the Wrights and
>> Pratts.
>>
>> So that brings up the question of how the M14 and Huosai engines get
>> oil to the master rod bearing. If there are oil journals to ensure
>> proper lubrication of the master rod bearing when the prop is turning
>> the engine then there is no reason to worry about doing damage to the
>> engine when you pull the throttle back to idle. Given that the M14 is
>> intended for aerobatic use, I suspect it *does* have proper
>> lubrication when the prop is driving the engine, hence the lack of an
>> warnings about the prop driving the engine in the manuals.
>>
>> But this is only supposition on my part. Only someone who really knows
>> the engine can tell for sure.
>>
>>
>> --
>> Brian Lloyd 3191 Western Drive
>> brian HYPHEN 1927 AT lloyd DOT com Cameron Park, CA 95682
>> +1.916.367.2131 (voice) +1.270.912.0788 (fax)
>>
>> I fly because it releases my mind from the tyranny of petty things . . .
>> - Antoine de Saint-Exupry
>>
>> PGP key ID: 12095C52A32A1B6C
>> PGP key fingerprint: 3B1D BA11 4913 3254 B6E0 CC09 1209 5C52 A32A 1B6C
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>
>
>
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