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Correct me if im wrong, but when a helo's engine dies it's propeller will enter an auto rotation (windmilling effect) causing it to fall to the ground at a much slower rate right?

We can assume this is true by looking at some of mother natures seeds that spin around causing it to glide to the ground rather than falling to its doom.

Now, what if we apply this to a cessna's propellor (its horizontal component of lift // its thrust) would the proppelor act as a source of drag slowing the cessna down incase of an engine failure or will the propelor be to small to act as a source of drag?

In other words, does windmilling induce drag?

Anyways, My real question is, imagine that it does... & you some how managed to stop the propellors from autorotation (windmilling)... Will your cessna glide further as you pitch for 60knots with a higher pitch attitude or will the cessna glide shorter due to the higher pitch attitude & slower Ground speed?

yes, a windmilling propeller is a major drag. essentially it is equivalent drag of having a plate the same radius out in the airflow. This is why almost all twin engine airplanes have full feathering propellers so that if one engine fails the prop can be feathered. This makes the difference between climbing and descending on the good engine, in most cases.

If you are flying an airplane with a controllable pitch propeller, during your engine out practice, pull the prop to low pitch. You can FEEL the acceleration as the drag is reduced. and this is just a reduction, the prop is still windmilling.

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Everyone must believe in something, I believe that I will go flying.

I can second Tony's thoughts on dropping the prop to a high pitch setting...the Cessna 172RG is a great plane to try this in. It really extends your glide distance.

As for stopping the prop on a 152 or '72, you need to get the airspeed down to a value that's below best glide to get it to stop windmilling...but once it stops, it's really smooth and peaceful.

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Inst: "So how far out so we make our initial call-up?"
Student: "10 miles"
Inst: "OK, let's make that call"
Student: "Airport Traffic, Cessna 172, 3 miles east..."

Hey guys,

Can you elaborate on that a bit?

My question is -

In the 172RG when the engine fails the prop defaults to a flat blade angle to help initiate a restart ... right? The opposite of what happens in a twin.

Well ...

If it's oil pressure in the 172RG that causes the prop to move to a coarser blade ange how, when the engine is failed, does moving the prop lever affect anything? Is there enough pressure left in the idling engine that it works ... and if so ... can that be counted on in an engine failure?

jason

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"To Live is To Fly" - Townes VanZandt
www.thefinerpoints.net
jason@thefinerpoints.net

By "low" pitch, I assume you mean "coarse" or "steepest"? I ask because in model airplane terminology, a lower pitch means "fine" or "flattest".

I've discovered in the Diamond Katana that pulling the prop to the lowest rpm setting (i.e. coarse pitch) improves the glide, and conversely pushing it to the high rpm setting (i.e. flat pitch) increases the descent angle.

Stefan Vorkoetter
www.stefanv.com/aviation

jason im pretty sure that if the prop is windmilling, the oil pump will turn and provide enough pressure to change the pitch on the prop. if the engine is seized then you dont have to worry bout it

_________________
Everyone must believe in something, I believe that I will go flying.

Tony's got it. If the prop is stopped, what you see is what you've got. As long as it's windmilling, theres enough pressure in the hub to adjust the pitch. In the RG, you back the prop lever all the way out.

_________________
Inst: "So how far out so we make our initial call-up?"
Student: "10 miles"
Inst: "OK, let's make that call"
Student: "Airport Traffic, Cessna 172, 3 miles east..."

You bet.
And while the prop is turning and the oil pressure is still controlling the pitch, with the prop lever full forward we're asking for an RPM which we won't get (without the engine power). It will try by going to full minimum (flat) pitch.

It's worse than having the flat of the blade against the wind. With the wind pushing the prop around rather than the prop pulling through the air, I figure the spinning prop is actually operating at a negative angle of attack and actively developing reverse thrust (although the prop's non-symmetrical airfoil is operating at a less efficient "upside down" angle of attack at this point).
This is further corroborated by the often heard statement that a stopped prop offers less drag (& flatter glide) than a windmilling one.
Joe