Seneca II says to set props to 2250rpm during the prelanding check (which should be done on the downwind leg). Then it says to advance props to full forward position during "close final approach". Seneca I says 2500rpm downwind, and it says the prop controls "may be advanced" on short final. Twin comanche just says 2400rpm during pre-landing check, then do a GUMPS check on short finals.
In general I think it's best to always follow the POH unless there is a good reason not to. A good starting point is to actually read the damn POH, which as HPC pointed out a lot of people don't bother their asses doing. (That's probably why every flight school these days insists on giving you a test from the POH these days when you check out a plane).
Getting back to the original question: did this person use 2400rpm in the PA-30, or something higher?
Multi engine training.
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Colonel
- Posts: 3450
- Joined: Wed Apr 29, 2015 10:31 am
Airframe POH is a good place to start, but remember
it's a comprimise between what the engineers, salesmen
and the FAA want you to do, and there's often a tug
of war between them.
Reading the Engine Manufacturer's Operating Manual
(for the exact model of engine - they differ) is a really
excellent idea, too. Often there is far more in there
than the airframe manufacturer will pass on.
it's a comprimise between what the engineers, salesmen
and the FAA want you to do, and there's often a tug
of war between them.
Reading the Engine Manufacturer's Operating Manual
(for the exact model of engine - they differ) is a really
excellent idea, too. Often there is far more in there
than the airframe manufacturer will pass on.
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Colonel
- Posts: 3450
- Joined: Wed Apr 29, 2015 10:31 am
One really important thing to note about piston
engines and constant speed props:
Is it ok to drive the engine with the props?
On the Pitts (direct drive), sure.
On the C421, hell no.
It's important to know what works for your
engine/prop combination. We cannot dumb
everything down to the TC/FTU level, unfortunately
(oversquare nonsense comes to mind).
When the prop lever/knobs go forward,
the drag goes up. This is certainly true
in descent from cruise, too.
If you are in cruise at say 20 inches and
2400 RPM, I might recommend descending
at 2200 RPM and leaving the throttle where
it is. You will save time.
As pilots we think of constant speed props
as providing lots of thrust but they also can
provide enormous drag - that's why you have
to feather the dead engine if you want to
climb, in a piston twin.
engines and constant speed props:
Is it ok to drive the engine with the props?
On the Pitts (direct drive), sure.
On the C421, hell no.
It's important to know what works for your
engine/prop combination. We cannot dumb
everything down to the TC/FTU level, unfortunately
(oversquare nonsense comes to mind).
When the prop lever/knobs go forward,
the drag goes up. This is certainly true
in descent from cruise, too.
If you are in cruise at say 20 inches and
2400 RPM, I might recommend descending
at 2200 RPM and leaving the throttle where
it is. You will save time.
As pilots we think of constant speed props
as providing lots of thrust but they also can
provide enormous drag - that's why you have
to feather the dead engine if you want to
climb, in a piston twin.
-
Colonel
- Posts: 3450
- Joined: Wed Apr 29, 2015 10:31 am
One last comment, on RPM redline:
If you read what the engine manufacturers
say in their SB's, etc ... momentarily exceeding
redline RPM is no big deal, generally. They
will define percentage ranges.
http://www.lycoming.com/Portals/0/techpublications/servicebulletins/SB%20369C%20(04-18-2012)/Engine%20Inspection%20after%20Overspeed.pdf
levers in, the governor may not be able to react fast enough
to avoid exceeding redline. If you don't believe me, perhaps
you will believe Lycoming.
However, with a 2700 RPM redline (eg) 10% is 270 RPM so
as long as you don't bounce over 2970 RPM, Lycoming is ok.
I worry more about the prop when you overspeed an engine,
frankly. Check the prop manufacturer literature for your
exact model, to see what they say. Those are very highly
stressed blades and hubs.
A friend of mine with a Lyc 360 in an RV-8 managed to
unport his oil pickup in a high speed dive. He did NOT
have a counterweighted prop (as found on twin and acro)
so his prop went full fine pitch with the loss of oil pressure
and his RPM his 4,000.
Ouch. His prop was trash - he bought a counterweighted
one - and his engine was overhauled and NDT'd. I am sure
they changed all the connecting rod bolts, etc which were
stretched.
Food for thought: the acro guys in the single seat Pitts
with the 4-cyl Lycs frequently see 3300-3400 RPM. Engine
is fine. It's the prop you have to worry about.
If you read what the engine manufacturers
say in their SB's, etc ... momentarily exceeding
redline RPM is no big deal, generally. They
will define percentage ranges.
http://www.lycoming.com/Portals/0/techpublications/servicebulletins/SB%20369C%20(04-18-2012)/Engine%20Inspection%20after%20Overspeed.pdf
Lesson for Crunch here: Yes, if you shove the knobs andMomentary overspeed can occur during a landing attempt, when the propeller governor lags as the throttle
is suddenly opened for a goÂaround.
In fixed wing aircraft, momentary overspeed is defined as an increase of no more than 10% of rated engine RPM for a period not exceeding 3 seconds. If the duration and amount of overspeed is calculated to fall within the limitations defined as momentary, no further maintenance actions are necessary
levers in, the governor may not be able to react fast enough
to avoid exceeding redline. If you don't believe me, perhaps
you will believe Lycoming.
However, with a 2700 RPM redline (eg) 10% is 270 RPM so
as long as you don't bounce over 2970 RPM, Lycoming is ok.
I worry more about the prop when you overspeed an engine,
frankly. Check the prop manufacturer literature for your
exact model, to see what they say. Those are very highly
stressed blades and hubs.
A friend of mine with a Lyc 360 in an RV-8 managed to
unport his oil pickup in a high speed dive. He did NOT
have a counterweighted prop (as found on twin and acro)
so his prop went full fine pitch with the loss of oil pressure
and his RPM his 4,000.
Ouch. His prop was trash - he bought a counterweighted
one - and his engine was overhauled and NDT'd. I am sure
they changed all the connecting rod bolts, etc which were
stretched.
Food for thought: the acro guys in the single seat Pitts
with the 4-cyl Lycs frequently see 3300-3400 RPM. Engine
is fine. It's the prop you have to worry about.
-
Chuck Ellsworth
There is something wrong with the way I have this forum set because I cant highlight , copy and paste here.
Jesus I get tired of people not being able to understand what they are reading and going off on a tangent about something I did not say.
Soo...
To CpnCrunch.
In my original post about this subject I did not say we were flying a Twin Comanche. Try understanding what I write.
The airplane we were flying was mine and I had a good reason for not wanting high RPM being selected over and over and over on every training flight.
The instructor refused to operate my airplane the way I wanted it operated so that made it simple, he never got to teach on it.
As to the mantra about using high RPM on the approach for " Safety ", what is unsafe about descending at cruise RPM?
Jesus I get tired of people not being able to understand what they are reading and going off on a tangent about something I did not say.
Soo...
To CpnCrunch.
In my original post about this subject I did not say we were flying a Twin Comanche. Try understanding what I write.
The airplane we were flying was mine and I had a good reason for not wanting high RPM being selected over and over and over on every training flight.
The instructor refused to operate my airplane the way I wanted it operated so that made it simple, he never got to teach on it.
As to the mantra about using high RPM on the approach for " Safety ", what is unsafe about descending at cruise RPM?
-
CpnCrunch
- Posts: 149
- Joined: Sun Nov 01, 2015 10:46 pm
Chuck Ellsworth wrote: In my original post about this subject I did not say we were flying a Twin Comanche. Try understanding what I write.
I did understand perfectly. However that is the example you used, so that is what I gave figures for.
The airplane we were flying was mine and I had a good reason for not wanting high RPM being selected over and over and over on every training flight.
The instructor refused to operate my airplane the way I wanted it operated so that made it simple, he never got to teach on it.
As to the mantra about using high RPM on the approach for " Safety ", what is unsafe about descending at cruise RPM?
So what precisely did the POH say to use for rpm in downwind, and what rpm did this instructor use?
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Chuck Ellsworth
No he was not.
And once more I do not operate or teach others to operate aircraft in non conformance of POH.
I am really getting fed up with people who keep trying to make it look like I operate outside of the rules and regulations so why don't you find someone else to irritate?
And once more I do not operate or teach others to operate aircraft in non conformance of POH.
I am really getting fed up with people who keep trying to make it look like I operate outside of the rules and regulations so why don't you find someone else to irritate?
-
vanNostrum
- Posts: 338
- Joined: Wed Nov 04, 2015 9:04 pm
An analogy that served me well from the very first time I flew a CS prop was to think of it as driving a car with manual transmission ,fine pitch been the low gear , so in the same way I would not shift a car to low gear at 70 kph I didn't select fine pitch until speed was reduced to final.
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