Can I pose a hypotetical question

We were discussing Engine failures in single engine aircraft with a constant
speed propeller..
Not catastrophic but more like fuel starvation types, where the prop keeps
windmilling..

The question is on getting the maximum gliding distance from the windmilling
prop..

It is assumed that a higher pitch/lower r.p.m. would give reduced drag:
hence maximum gliding distance..

The question is: Would a windmilling prop generate sufficient oil pressure
to maintain control of the propeller
and what r.p.m. would one expect from this scenario?

In article ,
"rojolo" wrote:

We were discussing Engine failures in single engine aircraft with a constant
speed propeller..
Not catastrophic but more like fuel starvation types, where the prop keeps
windmilling..

The question is on getting the maximum gliding distance from the windmilling
prop..

It is assumed that a higher pitch/lower r.p.m. would give reduced drag:
hence maximum gliding distance..

The question is: Would a windmilling prop generate sufficient oil pressure
to maintain control of the propeller
and what r.p.m. would one expect from this scenario?

You have to know how the governor is set up for the engine you are
flying behind. Some engines are set so that when the oil pressure drops,
the prop automatically goes to high RPM. Other engines are set to
automatically go to low RPM.

According to "Aircraft Systems for Pilots," by Dr. Dale DeMer,
constant-speed props for singles go to flat pitch (high drag) when oil
pressure is lost; constant-speed props for twins go toward the feathered
position (low drag). When flying a single, if the engine quits but the prop
is still turning, which is the usual case, pull the prop control back toward
coarse pitch to increase glide distance...you can't feather the prop, but
you can come close to it. Losing an engine in a twin means go to feather, so
in both cases the prop control comes back.

Bob Gardner

"rojolo" wrote in message
...
We were discussing Engine failures in single engine aircraft with a
constant
speed propeller..
Not catastrophic but more like fuel starvation types, where the prop keeps
windmilling..

The question is on getting the maximum gliding distance from the
windmilling
prop..

It is assumed that a higher pitch/lower r.p.m. would give reduced drag:
hence maximum gliding distance..

The question is: Would a windmilling prop generate sufficient oil
pressure
to maintain control of the propeller
and what r.p.m. would one expect from this scenario?

"rojolo" wrote in message
...
[...]
The question is: Would a windmilling prop generate sufficient oil
pressure
to maintain control of the propeller
and what r.p.m. would one expect from this scenario?

I'm sure Bob knows the answer. I'm not sure why he didn't post it (but he
did post a bunch of other useful stuff ).

Anyway, yes...the engine RPM is likely to be high enough to provide oil
pressure to control the prop pitch.

As for what RPM to expect, I don't know. Possibly around 1000 RPM (give or
take 100 or so), less with the prop at full coarse pitch?

Pete

The problem is that single engine piston propellers go immediately to a
high rpm flat pitch when the oil pressure drops too low to operate it,
which is the worst possible case for increasing glide, but gives you
the greatest likelihood of restarting the engine. Having tried it, I
can say that at best glide the prop turns too slowly to give enough oil
pressure to control it. Even if it did and you managed to increase the
pitch, the high pitch would immediately slow the rotation of the prop
and the oil pressure would drop again. Any pitch above best glide and
the prop slows significantly and might even stop. You then have to
lower the nose quite a bit to get it turning again.

Multi-engine planes and turbine singles reverse the oil connections to
the governor. Loss of oil pressure will feather the prop. It is assumed
that you are unlikely to restart a turbine engine in the air if it
fails (nevertheless, you still practice these emergencies in aircraft
such as the King Air), and that you still have one good engine in a
twin.

All of the assumptions are a little bit questionable, of course.

rojolo wrote:
The question is: Would a windmilling prop generate sufficient oil pressure
to maintain control of the propeller
and what r.p.m. would one expect from this scenario?


I've had two engine outs in singles (a Piper Lance and a C-210) and in both
cases was able to extend the glide considerably by pulling the prop all the way
back. I have no idea what rpm I was left with: I was more focused on airspeed
control at that point.

In the case of the Lance, it was a catastrophic engine failure after an oil line
vibrated loose off the oil cooler. In the C-210, it was a fuel starvation
situation. In both cases the props retarded pretty much as if you'd exercised
them during a run up. And both props were still turning at some rpm all the way
to the ground.



--
Mortimer Schnerd, RN

VE

One of the guys in our hangar has a prop on his RV-8 that apparently
goes to coarse pitch when pressure is lost... its a big ugly fat-bladed
Whirl Wind 200C, IIRC.

Bob Martin wrote:
One of the guys in our hangar has a prop on his RV-8 that apparently
goes to coarse pitch when pressure is lost... its a big ugly fat-bladed
Whirl Wind 200C, IIRC.

Perhaps it came out of a twin?

George Patterson
Drink is the curse of the land. It makes you quarrel with your neighbor.
It makes you shoot at your landlord. And it makes you miss him.

Seems like you have a definitive answer having been there twice.. Thanks for
the quick reply
"Mortimer Schnerd, RN" wrote in message
...
rojolo wrote:
The question is: Would a windmilling prop generate sufficient oil
pressure
to maintain control of the propeller
and what r.p.m. would one expect from this scenario?


I've had two engine outs in singles (a Piper Lance and a C-210) and in
both
cases was able to extend the glide considerably by pulling the prop all
the way
back. I have no idea what rpm I was left with: I was more focused on
airspeed
control at that point.

In the case of the Lance, it was a catastrophic engine failure after an
oil line
vibrated loose off the oil cooler. In the C-210, it was a fuel starvation
situation. In both cases the props retarded pretty much as if you'd
exercised
them during a run up. And both props were still turning at some rpm all
the way
to the ground.



--
Mortimer Schnerd, RN

VE

Most POH's will give you a best glide with prop forward and prop back.
When doing engine out practice, I have my students use the prop control
to help adjust their approach. If they feel they a bit low, pulling
back on the prop will stretch the glide.

-Robert, CFI