Today's Message Index:
----------------------
1. 01:28 PM - fixed pitch prop question (Ron Carroll)
2. 01:46 PM - Re: fixed pitch prop question (Robbie Attaway)
3. 02:23 PM - Re: fixed pitch prop question (Ron Carroll)
4. 02:41 PM - Re: fixed pitch prop question (Tedd McHenry)
5. 02:57 PM - Re: fixed pitch prop question (Greg Young)
6. 03:41 PM - Re: fixed pitch prop question (rv6fly)
7. 05:15 PM - Re: fixed pitch prop question (David Leonard)
8. 05:15 PM - Re: fixed pitch prop question (Jim Wright)
9. 05:30 PM - Re: brake leak? (WPAerial@aol.com)
10. 06:24 PM - Re: fixed pitch prop question (Robbie Attaway)
11. 07:19 PM - Re: fixed pitch prop question (Ron Carroll)
12. 09:09 PM - Re: Re: brake leak? (Dick DeCramer)
13. 09:17 PM - Re: Re: brake leak? (WPAerial@aol.com)
14. 11:20 PM - Re: fixed pitch prop question (Tedd McHenry)
15. 11:48 PM - Re: fixed pitch prop question (David Leonard)
Message 1
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| Subject: | fixed pitch prop question |
My 6A has a history of low climb & low cruise RPM and high oil temps. My
mechanic, neighbors and friends have exhausted every means we can think of,
to no avail. I have a Lycoming O320-H2AD ( I really don't need negative
feedback regarding the choice of engines ), and had it overhauled 43 hours
ago. I hoped the overhaul would solve some of the problems, as it was in
pretty poor condition. The overhaul made absolutely no difference in either
RPM or high oil temp.
I changed to a larger oil cooler, no change. I then made a nice plenum for
the oil cooler, no change. I replaced the engine baffle seals, which made a
slight change in oil temp. These things, along with many other minor
things which were tried to satisfy various suggestions made by interested
onlookers.
The final thing my mechanic suggested was to have the Sensenich metal prop
re-pitched, and recommended the prop shop in Troutdale, Oregon. I flew the
plane, recorded some data I thought the shop would need in order to make the
proper change. I was disappointed to find that the prop shop didn't want
the data, they just need to know if I want better climb or cruise, I can't
have both. They can add or remove pitch, whatever I say I need or want.
They said that 1" pitch change would make about 25 to 35 RPM difference, so
how much more or less RPM do I want under what condition? What I need is
better climb (lower oil temp), and better cruise (?) at a higher RPM. The
engine may go faster, but the plane may not. This means poor fuel economy.
Broadly speaking, here are the performance figures I get:
RPM MP Throttle IAS Altitude Oil
2200 22.8 WOT climb 100 kts sea level 77C
2240 22.8 WOT climb 110 kts contin. climb 98C
2390 25.8 WOT 138 kts 3000' 100C
2410 25.7 WOT 142 kts 3000' 100C
2040 19.4 econ cruise 124 kts 3000' 100C
2000 18.9 " " 115 kts 3000' 99C
I know this is not very well arranged, nor is it very scientific, but its
what I have for now. My friends with RVs claim that I should get better
performance than this, both in air speed and RPM. My mechanic believes the
high oil temps are due to too much pitch. The engine can never get into the
160 HP range. "It is working too hard and creating heat, like driving your
car up hill in overdrive all the time.", he said.
My question is this: Has anyone re-pitched their prop to gain RPM? If so,
did it negatively affect your WOT cruise speed? Did it affect your oil
temp? Do I have any other options (again, don't mention the engine, I've
heard them all) ?
This thing should fly better than this!!!
Ron Carroll
Message 2
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| Subject: | Re: fixed pitch prop question |
Hi Ron, Where did you get the engine? Was it on a flying a flying plane before
you got it? Who overhauled it for you? The reason I ask is because I have seen
new cams that had the timing marked incorrectly. One of those engines would not
turn full RPMs but still ran and was flown about 3 hours.
Robbie
----- Original Message -----
From: Ron Carroll
To: rv6-list@matronics.com
Sent: Sunday, October 30, 2005 2:27 PM
Subject: RV6-List: fixed pitch prop question
My 6A has a history of low climb & low cruise RPM and high oil temps. My mechanic,
neighbors and friends have exhausted every means we can think of, to no
avail. I have a Lycoming O320-H2AD ( I really don't need negative feedback
regarding the choice of engines ), and had it overhauled 43 hours ago. I hoped
the overhaul would solve some of the problems, as it was in pretty poor condition.
The overhaul made absolutely no difference in either RPM or high oil
temp.
I changed to a larger oil cooler, no change. I then made a nice plenum for the
oil cooler, no change. I replaced the engine baffle seals, which made a slight
change in oil temp. These things, along with many other minor things which
were tried to satisfy various suggestions made by interested onlookers.
The final thing my mechanic suggested was to have the Sensenich metal prop re-pitched,
and recommended the prop shop in Troutdale, Oregon. I flew the plane,
recorded some data I thought the shop would need in order to make the proper
change. I was disappointed to find that the prop shop didn't want the data,
they just need to know if I want better climb or cruise, I can't have both.
They can add or remove pitch, whatever I say I need or want. They said that 1"
pitch change would make about 25 to 35 RPM difference, so how much more or less
RPM do I want under what condition? What I need is better climb (lower oil
temp), and better cruise (?) at a higher RPM. The engine may go faster, but
the plane may not. This means poor fuel economy.
Broadly speaking, here are the performance figures I get:
RPM MP Throttle IAS Altitude Oil
2200 22.8 WOT climb 100 kts sea level 77C
2240 22.8 WOT climb 110 kts contin. climb 98C
2390 25.8 WOT 138 kts 3000' 100C
2410 25.7 WOT 142 kts 3000' 100C
2040 19.4 econ cruise 124 kts 3000' 100C
2000 18.9 " " 115 kts 3000' 99C
I know this is not very well arranged, nor is it very scientific, but its what
I have for now. My friends with RVs claim that I should get better performance
than this, both in air speed and RPM. My mechanic believes the high oil temps
are due to too much pitch. The engine can never get into the 160 HP range.
"It is working too hard and creating heat, like driving your car up hill in
overdrive all the time.", he said.
My question is this: Has anyone re-pitched their prop to gain RPM? If so, did
it negatively affect your WOT cruise speed? Did it affect your oil temp?
Do I have any other options (again, don't mention the engine, I've heard them
all) ?
This thing should fly better than this!!!
Ron Carroll
Message 3
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| Subject: | Re: fixed pitch prop question |
Robbie, I am not the builder of this plane, but he is a neighbor. He bought
the engine from a company in British Columbia. They sold it to the builder
as a fresh overhaul. I won't go into a lot of explanation here on the
list, but I will say that at only 100 hours SMOH I had to have it overhauled
by a local IA, as the whole engine was 'worn out' with inside measurements
far out of specified overhaul limits. The cam was yellow tagged by a
rebuilder here in Oregon at the time of the local OH.
Because of the less than satisfactory performance the ignition timing, as
well as the valve timing has been checked several times by my OH-IA. This
would lead me to believe that the cam is properly timed.
Thanks for your thoughts, and I hope everyone on the list appreciates my
dilemma.
Ron Carroll
----- Original Message -----
From: Robbie Attaway
To: rv6-list@matronics.com
Sent: Sunday, October 30, 2005 1:46 PM
Subject: Re: RV6-List: fixed pitch prop question
Hi Ron, Where did you get the engine? Was it on a flying a flying plane
before you got it? Who overhauled it for you? The reason I ask is because I
have seen new cams that had the timing marked incorrectly. One of those
engines would not turn full RPMs but still ran and was flown about 3 hours.
Robbie
----- Original Message -----
From: Ron Carroll
To: rv6-list@matronics.com
Sent: Sunday, October 30, 2005 2:27 PM
Subject: RV6-List: fixed pitch prop question
My 6A has a history of low climb & low cruise RPM and high oil temps.
My mechanic, neighbors and friends have exhausted every means we can think
of, to no avail. I have a Lycoming O320-H2AD ( I really don't need
negative feedback regarding the choice of engines ), and had it overhauled
43 hours ago. I hoped the overhaul would solve some of the problems, as it
was in pretty poor condition. The overhaul made absolutely no difference in
either RPM or high oil temp.
I changed to a larger oil cooler, no change. I then made a nice plenum
for the oil cooler, no change. I replaced the engine baffle seals, which
made a slight change in oil temp. These things, along with many other
minor things which were tried to satisfy various suggestions made by
interested onlookers.
The final thing my mechanic suggested was to have the Sensenich metal
prop re-pitched, and recommended the prop shop in Troutdale, Oregon. I flew
the plane, recorded some data I thought the shop would need in order to make
the proper change. I was disappointed to find that the prop shop didn't
want the data, they just need to know if I want better climb or cruise, I
can't have both. They can add or remove pitch, whatever I say I need or
want. They said that 1" pitch change would make about 25 to 35 RPM
difference, so how much more or less RPM do I want under what condition?
What I need is better climb (lower oil temp), and better cruise (?) at a
higher RPM. The engine may go faster, but the plane may not. This means
poor fuel economy.
Broadly speaking, here are the performance figures I get:
RPM MP Throttle IAS Altitude Oil
2200 22.8 WOT climb 100 kts sea level 77C
2240 22.8 WOT climb 110 kts contin. climb 98C
2390 25.8 WOT 138 kts 3000' 100C
2410 25.7 WOT 142 kts 3000' 100C
2040 19.4 econ cruise 124 kts 3000' 100C
2000 18.9 " " 115 kts 3000' 99C
I know this is not very well arranged, nor is it very scientific, but
its what I have for now. My friends with RVs claim that I should get better
performance than this, both in air speed and RPM. My mechanic believes the
high oil temps are due to too much pitch. The engine can never get into the
160 HP range. "It is working too hard and creating heat, like driving your
car up hill in overdrive all the time.", he said.
My question is this: Has anyone re-pitched their prop to gain RPM? If
so, did it negatively affect your WOT cruise speed? Did it affect your oil
temp? Do I have any other options (again, don't mention the engine, I've
heard them all) ?
This thing should fly better than this!!!
Ron Carroll
Message 4
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| Subject: | Re: fixed pitch prop question |
--> RV6-List message posted by: Tedd McHenry <tedd@vansairforce.org>
Ron:
You should certainly be able to get more than 2410 RPM at WOT and 3000 feet. I
think your mechanic's hypothesis is quite reasonable (i.e. that the prop has
too much pitch and is not allowing the engine to get to full power).
What pitch is the prop now? At 2410 RPM and 140 knots your theoretical,
no-slip pitch is 70.6 inches. So if that's about what your pitch is then the
problem isn't pitch, it's that the engine isn't making full power. On the
other hand, if your pitch is much higher, say 80 inches, then you're getting
huge slip and the problem probably is the prop.
I like Robbie Attaway's hypothesis about the cam timing. I've seen that
mistake made with car engines (in fact, I've done it). Having the ignition
advance way off could do it, too. Neither of those would explain the high oil
temperature, but that could be unrelated.
You can estimate the pitch change by calculating,
1200 x knots / (oldpitch x newpitch)
where pitch is in inches. But if the pitch change results in a speed increase
then the RPM increase will be slightly more than what you calculate.
Tedd McHenry
Surrey, BC, Canada
Message 5
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| Subject: | fixed pitch prop question |
If you haven't done so, I'd check all the obvious engine specs again -
use the manual, trust nothing. Like Robbie, we had a local RV with the
cam off by one tooth. Another chasing similar poor performance
ultimately found the tach off by 200 rpm. I'd also check carb model, jet
#'s and actual measurements, throttle plate position, fuel flow, etc.
Any chance of swapping props with someone else? It does sound over
pitched. Are you certain it's the O-320 prop and not the O-360 model? Do
you know what the pitch is currently so you can compare it to other
O-320 RV-6's? Before you repitch, keep in mind there is a limit to the
total inches of pitch change (8 IIRC) allowed. Good hunting.
Greg Young
________________________________
From: owner-rv6-list-server@matronics.com
[mailto:owner-rv6-list-server@matronics.com] On Behalf Of Ron Carroll
Sent: Sunday, October 30, 2005 4:24 PM
To: rv6-list@matronics.com
Subject: Re: RV6-List: fixed pitch prop question
=09
=09
Robbie, I am not the builder of this plane, but he is a
neighbor. He bought the engine from a company in British Columbia.
They sold it to the builder as a fresh overhaul. I won't go into a lot
of explanation here on the list, but I will say that at only 100 hours
SMOH I had to have it overhauled by a local IA, as the whole engine was
'worn out' with inside measurements far out of specified overhaul
limits. The cam was yellow tagged by a rebuilder here in Oregon at the
time of the local OH.
Because of the less than satisfactory performance the ignition
timing, as well as the valve timing has been checked several times by my
OH-IA. This would lead me to believe that the cam is properly timed.
Thanks for your thoughts, and I hope everyone on the list
appreciates my dilemma.
Ron Carroll
----- Original Message -----
From: Robbie Attaway <mailto:robbie@attawayair.com>
To: rv6-list@matronics.com
Sent: Sunday, October 30, 2005 1:46 PM
Subject: Re: RV6-List: fixed pitch prop question
Hi Ron, Where did you get the engine? Was it on a flying
a flying plane before you got it? Who overhauled it for you? The reason
I ask is because I have seen new cams that had the timing marked
incorrectly. One of those engines would not turn full RPMs but still ran
and was flown about 3 hours.
Robbie
Message 6
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| Subject: | Re: fixed pitch prop question |
--> RV6-List message posted by: rv6fly <rv6fly@bresnan.net>
Ron Carroll wrote:
> <snip.
> My question is this: Has anyone re-pitched their prop to gain RPM?
> If so, did it negatively affect your WOT cruise speed? Did it affect
> your oil temp? Do I have any other options (again, don't mention the
> engine, I've heard them all) ?
>
>
> Ron Carroll
Ron,
I found the following in the archive and hope it might shed a bit of
light on your problem. I didn't have a oil temp problem. My cooler was
mounted in the floor right behind the left inlet and worked very well.
I had to put an adjustable door that I could close for winter flying. I
had a spreadsheet somehwhere of the performance tests on my wood and
then the before and after re-pitch on the Sensenich but have no idea
where it is. On some old computer in the basement I'd reckon. "In the
old days" it seems like everyone tried to pitch the prop so you would be
a max rpms at wide open throttle at 7,500 feet. This would give you 75%
power. This is how I finally set up my prop and it worked well on my RV6.
Bob Skinner
* I am building an RV-6a with an O320-E2D 150hp engine and plan on using a
>Sensenich prop. It seems to be available in 4 pitch increments (75, 76, 77
>and 79). Has anyone evaluated a -6A with these props and 150hp and, if so,
>can you share your experiences/results? We want to get the most out of the
>150hp and I reckon that either the 76 or the 77 inch pitch will be the best
>compomise for climb/cruise but I am curious to know how much one loses in
>climb/gains in cruise with the 79 inch prop. I also expect that the 75 inch
>pitch will reach the 2600 rpm limit quickly and sufer in cruise because of
>it.
>
>Dave Irwin
Dave,
I'm using the Sensenich prop on my 150 hp RV-6. I started with the
recommeded 77 pitch and ended up reducing the pitch to just tad under 75.
My idea was to pitch the prop so that at 7,500-8,000 feet, I can operate at
full throttle for best fuel/air distribution (because the carb butterfly is
parallel to the fuel/air mixture) and not exceed the 2,600 rpm redline. The
reduction in pitch did improve takeoff and climb a bit. Why would you
suffer in cruise when running at 2,600 rpms? Doesn't rpms = h.p. and h.p. speed?
You could improve take off and climb by reducing pitch further but
would have to throttle back quite a bit in cruise.
BTW, I had a wood prop on for a few hundred yours and then went to the
Sensenich. My next six will have a constant speed. I hate like the dickens
to spend the bucks but it's also frustrating to mess around with different
props trying to fine tune performance. With a constant speed, you get
maximum h.p. on take off which means you can climb to a safe altitude in
case the engine quits and can clear obstructions. Besides, I'm getting
tired of watching those show off constant speed guys blast off while I do my
fixed pitched, shallow climb out:)*
>
Message 7
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| Subject: | Re: fixed pitch prop question |
Ron,
You have gotten some great input so far on this thread. Someone asked you
to compare the existing pitch to your performance and that is great advice
to see if the problem is your prop. You also need to compare your fuel burn
to you apparent power output (based on speed - keeping in mind that your
speed is relatively slow). Poor BSFC would indicate an internal engine
problem, despite the recent re-built (mistakes to happen during a rebuild).
This could also explain increased oil temps.
But looking at the numbers you posted the problem seems clear to me that
you are not getting the manifold pressure you should be getting. In at 100kt
climb at SL your MP should be greater than the altimeter setting. There is
something wrong with the way air is getting into your engine. Assuming you
would have found any obvious blockage, the problem could also be a strange
boundary layer problem. Airflow problems could also cause the oil temp
problem...
Good luck.
--
Dave Leonard
Turbo Rotary RV-6 N4VY (fixed pitch and happy with it)
http://members.aol.com/_ht_a/rotaryroster/index.html
http://members.aol.com/_ht_a/vp4skydoc/index.html
On 10/30/05, Ron Carroll <RonCarr@qwest.net> wrote:
>
> My 6A has a history of low climb & low cruise RPM and high oil temps. My
> mechanic, Roneighbors and friends have exhausted every means we can think
> of, to no avail. I have a Lycoming O320-H2AD ( I really don't need negative
> feedback regarding the choice of engines ), and had it overhauled 43 hours
> ago. I hoped the overhaul would solve some of the problems, as it was in
> pretty poor condition. The overhaul made absolutely no difference in
> either RPM or high oil temp.
> I changed to a larger oil cooler, no change. I then made a nice plenum
> for the oil cooler, no change. I replaced the engine baffle seals, which
> made a slight change in oil temp. These things, along with many other minor
> things which were tried to satisfy various suggestions made by interested
> onlookers.
> The final thing my mechanic suggested was to have the Sensenich metal
> prop re-pitched, and recommended the prop shop in Troutdale, Oregon. I flew
> the plane, recorded some data I thought the shop would need in order to make
> the proper change. I was disappointed to find that the prop shop didn't want
> the data, they just need to know if I want better climb or cruise, I can't
> have both. They can add or remove pitch, whatever I say I need or want. They
> said that 1" pitch change would make about 25 to 35 RPM difference, so how
> much more or less RPM do I want under what condition? What I need is better
> climb (lower oil temp), and better cruise (?) at a higher RPM. The engine
> may go faster, but the plane may not. This means poor fuel economy.
> Broadly speaking, here are the performance figures I get:
> *RPM* *MP* *Throttle* *IAS* *Altitude* *Oil*
> **
> 2200 22.8 WOT climb 100 kts sea level 77C
> 2240 22.8 WOT climb 110 kts contin. climb 98C
> 2390 25.8 WOT 138 kts 3000' 100C
> 2410 25.7 WOT 142 kts 3000' 100C
> 2040 19.4 econ cruise 124 kts 3000' 100C
> 2000 18.9 " " 115 kts 3000' 99C
> I know this is not very well arranged, nor is it very scientific, but its
> what I have for now. My friends with RVs claim that I should get better
> performance than this, both in air speed and RPM. My mechanic believes the
> high oil temps are due to too much pitch. The engine can never get into the
> 160 HP range. "It is working too hard and creating heat, like driving your
> car up hill in overdrive all the time.", he said.
> My question is this: Has anyone re-pitched their prop to gain RPM? If so,
> did it negatively affect your WOT cruise speed? Did it affect your oil temp?
> Do I have any other options (again, don't mention the engine, I've heard
> them all) ?
> This thing should fly better than this!!!
> Ron Carroll
>
Message 8
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| Subject: | fixed pitch prop question |
--> RV6-List message posted by: "Jim Wright" <jlwright@cox-internet.com>
This is not totally unrelated so I thought I'd share. I had a 172 with a
climb prop that cruised at 115 mph at 2350 RPM. I had another one the
same year model and the same engine with a cruise prop. That one cruised
at 125 mph at 2350 rpm's. The plane with the cruise prop burned at least
1 gallon per hour more than the climb prop at the same rpm. Overall I
liked the climb prop much better.
Jim Wright RV-9A 90919 Arkansas
Message 9
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does anyone else have the brake caliber leak when the pads wares out?
as soon as the pad gets almost to the rivets the piston (hockey puck thing)
is close enough to full throw, the o-ring begins to leak. one good thing about
this is it tells me the brakes need replaced, but is it supposed to happen?
jerry wilken
rv6a n699wp
370 hours
albany oregon
Message 10
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| Subject: | Re: fixed pitch prop question |
Ron, Call me at 602-538-6087 and I can tell you how to check the cam timing without
pulling the engine apart.
Robbie
----- Original Message -----
From: Ron Carroll
To: rv6-list@matronics.com
Sent: Sunday, October 30, 2005 3:23 PM
Subject: Re: RV6-List: fixed pitch prop question
Robbie, I am not the builder of this plane, but he is a neighbor. He bought
the engine from a company in British Columbia. They sold it to the builder as
a fresh overhaul. I won't go into a lot of explanation here on the list, but
I will say that at only 100 hours SMOH I had to have it overhauled by a local
IA, as the whole engine was 'worn out' with inside measurements far out of specified
overhaul limits. The cam was yellow tagged by a rebuilder here in Oregon
at the time of the local OH.
Because of the less than satisfactory performance the ignition timing, as well
as the valve timing has been checked several times by my OH-IA. This would
lead me to believe that the cam is properly timed.
Thanks for your thoughts, and I hope everyone on the list appreciates my dilemma.
Ron Carroll
----- Original Message -----
From: Robbie Attaway
To: rv6-list@matronics.com
Sent: Sunday, October 30, 2005 1:46 PM
Subject: Re: RV6-List: fixed pitch prop question
Hi Ron, Where did you get the engine? Was it on a flying a flying plane before
you got it? Who overhauled it for you? The reason I ask is because I have
seen new cams that had the timing marked incorrectly. One of those engines would
not turn full RPMs but still ran and was flown about 3 hours.
Robbie
----- Original Message -----
From: Ron Carroll
To: rv6-list@matronics.com
Sent: Sunday, October 30, 2005 2:27 PM
Subject: RV6-List: fixed pitch prop question
My 6A has a history of low climb & low cruise RPM and high oil temps. My
mechanic, neighbors and friends have exhausted every means we can think of, to
no avail. I have a Lycoming O320-H2AD ( I really don't need negative feedback
regarding the choice of engines ), and had it overhauled 43 hours ago.
I hoped the overhaul would solve some of the problems, as it was in pretty poor
condition. The overhaul made absolutely no difference in either RPM or high
oil temp.
I changed to a larger oil cooler, no change. I then made a nice plenum for
the oil cooler, no change. I replaced the engine baffle seals, which made
a slight change in oil temp. These things, along with many other minor things
which were tried to satisfy various suggestions made by interested onlookers.
The final thing my mechanic suggested was to have the Sensenich metal prop
re-pitched, and recommended the prop shop in Troutdale, Oregon. I flew the
plane, recorded some data I thought the shop would need in order to make the proper
change. I was disappointed to find that the prop shop didn't want the data,
they just need to know if I want better climb or cruise, I can't have both.
They can add or remove pitch, whatever I say I need or want. They said that
1" pitch change would make about 25 to 35 RPM difference, so how much more
or less RPM do I want under what condition? What I need is better climb (lower
oil temp), and better cruise (?) at a higher RPM. The engine may go faster,
but the plane may not. This means poor fuel economy.
Broadly speaking, here are the performance figures I get:
RPM MP Throttle IAS Altitude Oil
2200 22.8 WOT climb 100 kts sea level 77C
2240 22.8 WOT climb 110 kts contin. climb 98C
2390 25.8 WOT 138 kts 3000' 100C
2410 25.7 WOT 142 kts 3000' 100C
2040 19.4 econ cruise 124 kts 3000' 100C
2000 18.9 " " 115 kts 3000' 99C
I know this is not very well arranged, nor is it very scientific, but its
what I have for now. My friends with RVs claim that I should get better performance
than this, both in air speed and RPM. My mechanic believes the high oil
temps are due to too much pitch. The engine can never get into the 160 HP range.
"It is working too hard and creating heat, like driving your car up hill
in overdrive all the time.", he said.
My question is this: Has anyone re-pitched their prop to gain RPM? If so,
did it negatively affect your WOT cruise speed? Did it affect your oil temp?
Do I have any other options (again, don't mention the engine, I've heard them
all) ?
This thing should fly better than this!!!
Ron Carroll
Message 11
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| Subject: | Re: fixed pitch prop question |
This is in response to the latest message, which is from David Leonard, but
I'd also like to make comments to others that are generous enough to offer
some suggestions on my problem(s).
Tedd McHenry -
The pitch on my prop is 79". I had changed from 80" to 79" thinking it
would make a difference, but the difference was not noticeable to me. I
like the idea of calculating by using an equation, as you suggest, but I
just want to make sure I understand your formula. You say '1200 times
knots,divided by old pitch x newpitch' equal estimated pitch change. I
tried this: 1200 X 160 kts divided by 79"X75" , and the answer is "32.40".
What is this? I'll have to ask a couple of dumb questions: What is the
significance of the '1200'? Next, what 'knots'? cruise? I should be able
to figure this out, but its easier to ask. So, by using this, I should get
a good ballpark pitch by plugging in different 'newpitch' numbers. BTW, my
fuel burn at WOT was right at 8.5 gph.
Greg Young -
This problem has plagued me for over a year. EVERYTHING has been checked
and rechecked, according to the book. My IA checked to be sure I have the
correct carb & jets, the cam was checked, as was the ignition timing & valve
timing. I wish there was someone with a Sensenich prop in the pitch range
that I think I may wind up, but alas I don't. I can get the prop re-pitched
for $200, and it can be re-pitched again if necessary for another $200, so I
hope to get it close in the first try or two.
Bob Skinner -
You refer to a fellow that has a similar situation. One passage mentioned,
"Why would you suffer in cruise when running at 2,600 rpms? Doesn't rpms h.p.
and h.p. = speed? You could improve take off and climb by reducing
pitch further but would have to throttle back quite a bit in cruise." This
was my question; If I were to reduce the pitch so that the engine could
reach 2600 in cruise, will I suffer in speed because the prop isn't taking
as big a bite?
I like your preference of a constant speed prop, but the cost is more than I
care to spend. There are a LOT of happy campers flying fixed pitch props,
only sacrificing a little in climb.
Jim Wright -
You mention that your 172 actually got a higher cruise with less pitch, and
burned less fuel??? That's what I want!! Can I expect to fly faster and
burn less fuel with less pitch? The variables are too many for a guy like
me to be able to figure it out. I'm hoping that Tedd's formula will give me
a better idea.
David Leonard -
David, yours has me the most puzzled. You say that I should compare
existing pitch with performance. I don't understand this one at all. Also,
I can't understand how I can get higher manifold pressure that the altimeter
setting without using a blower. Could it be because of the ram effect of
the intake air scoop? If so, wouldn't it always be higher at WOT? Another
thing I don't know is 'BSFC'. I just Googled it, and find that it is 'Brake
Specific Fuel Consumption', the ratio of fuel consumed (in lbs. per hour) to
horsepower produced. I'm lost!
I want to thank all of you who have so promptly responded to my questions.
I'm not sure I have THE answer yet, but I'll hope that the pieces will start
to fit. I'd like to know what pitch everyone else with the same
plane/engine/prop (RV-6A, O320-H2AD-160, Sensenich metal prop (68x79))
combination are using successfully. I just want to re-pitch if necessary,
and get it close to right the first time. I would also like to know if a
flatter pitch will cost me in cruise (it can't go much slower).
Ron Carroll -
----- Original Message -----
From: David Leonard
To: rv6-list@matronics.com
Sent: Sunday, October 30, 2005 5:15 PM
Subject: Re: RV6-List: fixed pitch prop question
Ron,
You have gotten some great input so far on this thread. Someone asked you
to compare the existing pitch to your performance and that is great advice
to see if the problem is your prop. You also need to compare your fuel burn
to you apparent power output (based on speed - keeping in mind that your
speed is relatively slow). Poor BSFC would indicate an internal engine
problem, despite the recent re-built (mistakes to happen during a rebuild).
This could also explain increased oil temps.
But looking at the numbers you posted the problem seems clear to me that
you are not getting the manifold pressure you should be getting. In at
100kt climb at SL your MP should be greater than the altimeter setting.
There is something wrong with the way air is getting into your engine.
Assuming you would have found any obvious blockage, the problem could also
be a strange boundary layer problem. Airflow problems could also cause the
oil temp problem...
Good luck.
--
Dave Leonard
Turbo Rotary RV-6 N4VY (fixed pitch and happy with it)
http://members.aol.com/_ht_a/rotaryroster/index.html
http://members.aol.com/_ht_a/vp4skydoc/index.html
On 10/30/05, Ron Carroll <RonCarr@qwest.net> wrote:
My 6A has a history of low climb & low cruise RPM and high oil temps.
My mechanic, Roneighbors and friends have exhausted every means we can think
of, to no avail. I have a Lycoming O320-H2AD ( I really don't need
negative feedback regarding the choice of engines ), and had it overhauled
43 hours ago. I hoped the overhaul would solve some of the problems, as it
was in pretty poor condition. The overhaul made absolutely no difference in
either RPM or high oil temp.
I changed to a larger oil cooler, no change. I then made a nice plenum
for the oil cooler, no change. I replaced the engine baffle seals, which
made a slight change in oil temp. These things, along with many other
minor things which were tried to satisfy various suggestions made by
interested onlookers.
The final thing my mechanic suggested was to have the Sensenich metal
prop re-pitched, and recommended the prop shop in Troutdale, Oregon. I flew
the plane, recorded some data I thought the shop would need in order to make
the proper change. I was disappointed to find that the prop shop didn't
want the data, they just need to know if I want better climb or cruise, I
can't have both. They can add or remove pitch, whatever I say I need or
want. They said that 1" pitch change would make about 25 to 35 RPM
difference, so how much more or less RPM do I want under what condition?
What I need is better climb (lower oil temp), and better cruise (?) at a
higher RPM. The engine may go faster, but the plane may not. This means
poor fuel economy.
Broadly speaking, here are the performance figures I get:
RPM MP Throttle IAS Altitude Oil
2200 22.8 WOT climb 100 kts sea level 77C
2240 22.8 WOT climb 110 kts contin. climb 98C
2390 25.8 WOT 138 kts 3000' 100C
2410 25.7 WOT 142 kts 3000' 100C
2040 19.4 econ cruise 124 kts 3000' 100C
2000 18.9 " " 115 kts 3000' 99C
I know this is not very well arranged, nor is it very scientific, but
its what I have for now. My friends with RVs claim that I should get better
performance than this, both in air speed and RPM. My mechanic believes the
high oil temps are due to too much pitch. The engine can never get into the
160 HP range. "It is working too hard and creating heat, like driving your
car up hill in overdrive all the time.", he said.
My question is this: Has anyone re-pitched their prop to gain RPM? If
so, did it negatively affect your WOT cruise speed? Did it affect your oil
temp? Do I have any other options (again, don't mention the engine, I've
heard them all) ?
This thing should fly better than this!!!
Ron Carroll
Message 12
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Jerry,
I remember a few years ago that I had to pull the pistons on my brakes to determine
if the o-ring groove was machined properly to prevent o-ring blowout. The
problem is I can't remember where I got the information alerting me to the problem.
I did check vansaircraft.com but nothing is there but it might be a manufacturers
bulletin or an AD. I think some of the pistons had an groove machined
off center which could be what you have. Some of you other listers remember
anything about this? You may want to call the manufacturer for more info.
Dick DeCramer
RV6 N500DD
95 hours
Minnesota
----- Original Message -----
From:
Subject: RV6-List: Re: brake leak?
does anyone else have the brake caliber leak when the pads wares out?
as soon as the pad gets almost to the rivets the piston (hockey puck thing) is
close enough to full throw, the o-ring begins to leak. one good thing about this
is it tells me the brakes need replaced, but is it supposed to happen?
jerry wilken
rv6a n699wp
370 hours
albany oregon
Message 13
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afew years ago thay had some pistons put in backwards. that is not the case
with mine.
jerry wilken
Message 14
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| Subject: | Re: fixed pitch prop question |
--> RV6-List message posted by: Tedd McHenry <tedd@vansairforce.org>
Ron:
Sorry, looking back on my post I see that what I said was very unclear. The
formula estimates RPM change per inch of pitch change. In other words, the
value you calculated (32.4) is how much the RPM would change for each inch of
pitch change. The 1200 is a constant that factors in the odd mix of units
(revolutions per minute, nautical miles per hour, and inches of pitch). It's
actually 1216, but 1200 is close enough.
But that formula only works for pitch changes of 1 inch at a time. It might be
better to calculate the "no slip" speed for your prop and compare it to what
you're actually getting.
speed = RPM x pitch / 1216
By that calculation, your 79" pitch prop would give you 157 knots at 2410 RPM,
with no slip at all. Your measured speed was 142, so that's about 10 percent
slip. I think that's on the high side for cruise conditions, lending support
to the theory that you have too much pitch. But it's hard to get good
information on how much slip is typical.
The no-slip pitch that gives 142 knots at 2410 RPM is 71.6 inches. I'm
guessing the ideal pitch for your airplane is somewhere between where you are
(79") and 71.6".
But I think you should assure yourself that the engine isn't the problem,
before you re-pitch the prop. I agree with what Dave Leonard said about your
manifold pressure sounding low. Could you have an intake restriction of some
kind? Does the throttle actually open all the way? (Dumb question, I know,
but it happens.)
Tedd
Message 15
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| Subject: | Re: fixed pitch prop question |
Ron,
David Leonard -
> David, yours has me the most puzzled. You say that I should compare
> existing pitch with performance. I don't understand this one at all.
>
I was just agreeing with Tedd McHenry. There is a formula (and some
spreadsheets you can use) to calculate approximate performance based on prop
pitch and RPM. If you are finding that you are significantly off from this
performance, then the problem is either a significant increase in drag, or a
poorly designed propeller (not just the pitch)
Also, I can't understand how I can get higher manifold pressure that the
> altimeter setting without using a blower. Could it be because of the ram
> effect of the intake air scoop? If so, wouldn't it always be higher at WOT?
>
Correct. At a minimum, running static at sea level you should be seeing a
manifold pressure of 27 or 28 (slightly less than the altimeter setting).
Most RV's have a dynamic plenum to recover aerodynamic pressure that gives
an additional 1-2 inches. Even if your engine is run out and the propeller
is poorly pitched you should be seeing the appropriate manifold pressure.
IMHO, if those numbers you sent are correct, the problem is an air
restriction somewhere - no doubt about it.
Another thing I don't know is 'BSFC'. I just Googled it, and find that it
> is 'Brake Specific Fuel Consumption', the ratio of fuel consumed (in lbs.
> per hour) to horsepower produced. I'm lost!
>
Correct. What I mean is that if the problem is the pitch of your prop(or an
air restriction for that matter), then it shouldn't change your BSFC (i.e.
you should be burning an amount of fuel appropriate for the horse power you
are producing). There will be a natural variation in BSFC between engines
airplanes and propellers, but that variation is usually not a huge amount.
If you are burning more fuel than you should be for the speed you are
getting, then there is still a serious problem with you engine or carb.
How do you tell? The best way is to do a head to head comparison with a
similarly configured RV flying the same route at the same speed at the same
time. Carefully measure fuel burned in both aircraft and it should be
roughly the same.
If you don't have another RV to use you can compare your performance to
Vans published numbers.... or numbers published in the archives... you get
the idea.
But I still think your problem is some sort of air restriction.
>
> --
> Dave Leonard
> Turbo Rotary RV-6 N4VY
> http://members.aol.com/_ht_a/rotaryroster/index.html
> http://members.aol.com/_ht_a/vp4skydoc/index.html
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