Does a windmilling propeller create more drag than a stopped propeller in an engine out scenarioWhy does flight training usually start with (unsafe?) propeller planes and not with (safer?) jets?About how much drag does a non-operating engine create?Is a fixed wing more efficient in reaching a certain altitude than rotary wing?why are airplane propellers always undersized?Guidelines for using a constant speed/adjustable pitch propellerWould an aircraft with no ailerons, no elevators and no rudders be safely flyable?How did the controls work for variable-pitch props?Is 1 propeller always more efficient than 2?Does RPM refer to the speed of the engine or the speed of the propeller?Difference between constant speed and variable pitch propellers?
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Does a windmilling propeller create more drag than a stopped propeller in an engine out scenario
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Does a windmilling propeller create more drag than a stopped propeller in an engine out scenario
Why does flight training usually start with (unsafe?) propeller planes and not with (safer?) jets?About how much drag does a non-operating engine create?Is a fixed wing more efficient in reaching a certain altitude than rotary wing?why are airplane propellers always undersized?Guidelines for using a constant speed/adjustable pitch propellerWould an aircraft with no ailerons, no elevators and no rudders be safely flyable?How did the controls work for variable-pitch props?Is 1 propeller always more efficient than 2?Does RPM refer to the speed of the engine or the speed of the propeller?Difference between constant speed and variable pitch propellers?
$begingroup$
For this question lets assume that we are talking about a fixed pitch propeller and not a variable pitch propeller. I do understand that variable pitch props should be feathered during an engine failure.
The main rationale for this question is this statement that I found in a pilot forum:
I've been doing some research on something I hard from my old chief CFI a couple years back, but I'm not finding much on it. He is the only person I've heard this from, and any CFI, DPE, ect. I've talked about this to since have not heard of it. That being that when you have an engine failure more than several thousand ft. with a non-full-feathering prop, that you should pitch up and decrease airspeed, sometimes to an intentional stall, to stop the rotation of the prop/engine. (Of course, only after you have attempted to restart.) The reason being that you will see a greater gain in glide distance by reducing the drag created by forcing thee air to turn over the engine. He claimed that while you would most likely be off of Vl/d for a short amount of time, thus not gliding in the most efficient manner, that is outweighed by the decrease in drag. (As I said, do this only with several thousand feet and plenty of time.) He claimed that in the case of something such as a 172, doing this procedure at, say 10,000ft, you would gain several more miles of glide distance.
So what I am asking for is if indeed a windmilling prop has more drag than a stopped prop and if so would it be beneficial to follow the advice in the pilot forum?
aerodynamics propeller engine-failure
asked 3 hours ago
DLHDLH
2,951932
$endgroup$
|
show 1 more comment
$begingroup$
For this question lets assume that we are talking about a fixed pitch propeller and not a variable pitch propeller. I do understand that variable pitch props should be feathered during an engine failure.
The main rationale for this question is this statement that I found in a pilot forum:
I've been doing some research on something I hard from my old chief CFI a couple years back, but I'm not finding much on it. He is the only person I've heard this from, and any CFI, DPE, ect. I've talked about this to since have not heard of it. That being that when you have an engine failure more than several thousand ft. with a non-full-feathering prop, that you should pitch up and decrease airspeed, sometimes to an intentional stall, to stop the rotation of the prop/engine. (Of course, only after you have attempted to restart.) The reason being that you will see a greater gain in glide distance by reducing the drag created by forcing thee air to turn over the engine. He claimed that while you would most likely be off of Vl/d for a short amount of time, thus not gliding in the most efficient manner, that is outweighed by the decrease in drag. (As I said, do this only with several thousand feet and plenty of time.) He claimed that in the case of something such as a 172, doing this procedure at, say 10,000ft, you would gain several more miles of glide distance.
So what I am asking for is if indeed a windmilling prop has more drag than a stopped prop and if so would it be beneficial to follow the advice in the pilot forum?
aerodynamics propeller engine-failure
asked 3 hours ago
DLHDLH
2,951932
$endgroup$
$begingroup$
I would be surprised if something like a 172 would windmill the prop at all, especially where the air is thinner at 10,000 feet. A lot of times engine failure means the engine locks up. Fuel starvation (more common) can let the prop spin, but there is a lot of force needed to spin a prop. I think a spinning prop is a lot more common on aircraft that don't have direct drive, like a turbo prop than it is for direct driven propellers.
$endgroup$
– Ron Beyer
3 hours ago
$begingroup$
Most GA twins can fly with a feathered prop. They will not windmilling prop. Yes...the windmilling prop generates a HUGE amount of drag.
$endgroup$
– acpilot
2 hours ago
$begingroup$
There are some situations such as model airplanes/ sailplanes with brushless electric motors where the answer is not cut-and-dried and depends on many variables.
$endgroup$
– quiet flyer
2 hours ago
1
$begingroup$
Yes a Cessna 172 can definitely keep the prop windmilling. You have to slow to near stall speed to stop it. After that you can speed up and it won't windmill till you get going rather fast. I'm sure the drag is less with the prop stopped in that case.
$endgroup$
– quiet flyer
2 hours ago
$begingroup$
Air density probably doesn't matter, if we are talking about the tendency of the prop to windmill at any given IAS.
$endgroup$
– quiet flyer
2 hours ago
|
show 1 more comment
$begingroup$
For this question lets assume that we are talking about a fixed pitch propeller and not a variable pitch propeller. I do understand that variable pitch props should be feathered during an engine failure.
The main rationale for this question is this statement that I found in a pilot forum:
I've been doing some research on something I hard from my old chief CFI a couple years back, but I'm not finding much on it. He is the only person I've heard this from, and any CFI, DPE, ect. I've talked about this to since have not heard of it. That being that when you have an engine failure more than several thousand ft. with a non-full-feathering prop, that you should pitch up and decrease airspeed, sometimes to an intentional stall, to stop the rotation of the prop/engine. (Of course, only after you have attempted to restart.) The reason being that you will see a greater gain in glide distance by reducing the drag created by forcing thee air to turn over the engine. He claimed that while you would most likely be off of Vl/d for a short amount of time, thus not gliding in the most efficient manner, that is outweighed by the decrease in drag. (As I said, do this only with several thousand feet and plenty of time.) He claimed that in the case of something such as a 172, doing this procedure at, say 10,000ft, you would gain several more miles of glide distance.
So what I am asking for is if indeed a windmilling prop has more drag than a stopped prop and if so would it be beneficial to follow the advice in the pilot forum?
aerodynamics propeller engine-failure
asked 3 hours ago
DLHDLH
2,951932
$endgroup$
For this question lets assume that we are talking about a fixed pitch propeller and not a variable pitch propeller. I do understand that variable pitch props should be feathered during an engine failure.
The main rationale for this question is this statement that I found in a pilot forum:
I've been doing some research on something I hard from my old chief CFI a couple years back, but I'm not finding much on it. He is the only person I've heard this from, and any CFI, DPE, ect. I've talked about this to since have not heard of it. That being that when you have an engine failure more than several thousand ft. with a non-full-feathering prop, that you should pitch up and decrease airspeed, sometimes to an intentional stall, to stop the rotation of the prop/engine. (Of course, only after you have attempted to restart.) The reason being that you will see a greater gain in glide distance by reducing the drag created by forcing thee air to turn over the engine. He claimed that while you would most likely be off of Vl/d for a short amount of time, thus not gliding in the most efficient manner, that is outweighed by the decrease in drag. (As I said, do this only with several thousand feet and plenty of time.) He claimed that in the case of something such as a 172, doing this procedure at, say 10,000ft, you would gain several more miles of glide distance.
So what I am asking for is if indeed a windmilling prop has more drag than a stopped prop and if so would it be beneficial to follow the advice in the pilot forum?
aerodynamics propeller engine-failure
aerodynamics propeller engine-failure
asked 3 hours ago
DLHDLH
2,951932
asked 3 hours ago
DLHDLH
2,951932
asked 3 hours ago
DLHDLH
2,951932
asked 3 hours ago
DLHDLH
2,951932
asked 3 hours ago
DLHDLH
2,951932
2,951932
$begingroup$
I would be surprised if something like a 172 would windmill the prop at all, especially where the air is thinner at 10,000 feet. A lot of times engine failure means the engine locks up. Fuel starvation (more common) can let the prop spin, but there is a lot of force needed to spin a prop. I think a spinning prop is a lot more common on aircraft that don't have direct drive, like a turbo prop than it is for direct driven propellers.
$endgroup$
– Ron Beyer
3 hours ago
$begingroup$
Most GA twins can fly with a feathered prop. They will not windmilling prop. Yes...the windmilling prop generates a HUGE amount of drag.
$endgroup$
– acpilot
2 hours ago
$begingroup$
There are some situations such as model airplanes/ sailplanes with brushless electric motors where the answer is not cut-and-dried and depends on many variables.
$endgroup$
– quiet flyer
2 hours ago
1
$begingroup$
Yes a Cessna 172 can definitely keep the prop windmilling. You have to slow to near stall speed to stop it. After that you can speed up and it won't windmill till you get going rather fast. I'm sure the drag is less with the prop stopped in that case.
$endgroup$
– quiet flyer
2 hours ago
$begingroup$
Air density probably doesn't matter, if we are talking about the tendency of the prop to windmill at any given IAS.
$endgroup$
– quiet flyer
2 hours ago
|
show 1 more comment
$begingroup$
I would be surprised if something like a 172 would windmill the prop at all, especially where the air is thinner at 10,000 feet. A lot of times engine failure means the engine locks up. Fuel starvation (more common) can let the prop spin, but there is a lot of force needed to spin a prop. I think a spinning prop is a lot more common on aircraft that don't have direct drive, like a turbo prop than it is for direct driven propellers.
$endgroup$
– Ron Beyer
3 hours ago
$begingroup$
Most GA twins can fly with a feathered prop. They will not windmilling prop. Yes...the windmilling prop generates a HUGE amount of drag.
$endgroup$
– acpilot
2 hours ago
$begingroup$
There are some situations such as model airplanes/ sailplanes with brushless electric motors where the answer is not cut-and-dried and depends on many variables.
$endgroup$
– quiet flyer
2 hours ago
1
$begingroup$
Yes a Cessna 172 can definitely keep the prop windmilling. You have to slow to near stall speed to stop it. After that you can speed up and it won't windmill till you get going rather fast. I'm sure the drag is less with the prop stopped in that case.
$endgroup$
– quiet flyer
2 hours ago
$begingroup$
Air density probably doesn't matter, if we are talking about the tendency of the prop to windmill at any given IAS.
$endgroup$
– quiet flyer
2 hours ago
$begingroup$
I would be surprised if something like a 172 would windmill the prop at all, especially where the air is thinner at 10,000 feet. A lot of times engine failure means the engine locks up. Fuel starvation (more common) can let the prop spin, but there is a lot of force needed to spin a prop. I think a spinning prop is a lot more common on aircraft that don't have direct drive, like a turbo prop than it is for direct driven propellers.
$endgroup$
– Ron Beyer
3 hours ago
$begingroup$
I would be surprised if something like a 172 would windmill the prop at all, especially where the air is thinner at 10,000 feet. A lot of times engine failure means the engine locks up. Fuel starvation (more common) can let the prop spin, but there is a lot of force needed to spin a prop. I think a spinning prop is a lot more common on aircraft that don't have direct drive, like a turbo prop than it is for direct driven propellers.
$endgroup$
– Ron Beyer
3 hours ago
$begingroup$
Most GA twins can fly with a feathered prop. They will not windmilling prop. Yes...the windmilling prop generates a HUGE amount of drag.
$endgroup$
– acpilot
2 hours ago
$begingroup$
Most GA twins can fly with a feathered prop. They will not windmilling prop. Yes...the windmilling prop generates a HUGE amount of drag.
$endgroup$
– acpilot
2 hours ago
$begingroup$
There are some situations such as model airplanes/ sailplanes with brushless electric motors where the answer is not cut-and-dried and depends on many variables.
$endgroup$
– quiet flyer
2 hours ago
$begingroup$
There are some situations such as model airplanes/ sailplanes with brushless electric motors where the answer is not cut-and-dried and depends on many variables.
$endgroup$
– quiet flyer
2 hours ago
1
1
$begingroup$
Yes a Cessna 172 can definitely keep the prop windmilling. You have to slow to near stall speed to stop it. After that you can speed up and it won't windmill till you get going rather fast. I'm sure the drag is less with the prop stopped in that case.
$endgroup$
– quiet flyer
2 hours ago
$begingroup$
Yes a Cessna 172 can definitely keep the prop windmilling. You have to slow to near stall speed to stop it. After that you can speed up and it won't windmill till you get going rather fast. I'm sure the drag is less with the prop stopped in that case.
$endgroup$
– quiet flyer
2 hours ago
$begingroup$
Air density probably doesn't matter, if we are talking about the tendency of the prop to windmill at any given IAS.
$endgroup$
– quiet flyer
2 hours ago
$begingroup$
Air density probably doesn't matter, if we are talking about the tendency of the prop to windmill at any given IAS.
$endgroup$
– quiet flyer
2 hours ago
|
show 1 more comment
2 Answers
2
active
oldest
votes
$begingroup$
A windmilling propeller creates much more drag, by an order of magnitude at least. The obvious example is an autogyro or helicopter in autorotation, which drops like a stone if the rotor stopped.
Drag is a function of blade area for a stopped rotor and a function of disc area for a windmilling one. The difference is most pronounced for large rotors with few blades and almost nonexistent for turbofans.
answered 3 hours ago
Rainer P.Rainer P.
1,01939
$endgroup$
$begingroup$
Last time I looked at a propeller driven aircraft, the prop wasn't pointing vertically upwards. Also your assertion the windmill makes no difference to the drag of turbofans is plain wrong - a fan that is not freely windmilling has MUCH more drag, as has been demonstrated in real life when engine damage in flight locks up the rotors.
$endgroup$
– alephzero
1 hour ago
$begingroup$
A helicopter in a vertical descent under autorotation is not much different from a propeller aircraft in horizontal flight with one engine inoperative. The rotor faces into the direction of travel and crates 'windmill drag'. The only difference is that the helicopter pilot tries to maximize drag in order to save his life. - @alephzero
$endgroup$
– Rainer P.
59 mins ago
add a comment |
$begingroup$
I would not follow the advice in the forum. I have heard arguments either way and I have yet to see empirical evidence proving either assertion. The only studies I have seen have been inconclusive on the subject. The chances are good that you couldn't change the prop behavior anyway, if your crankshaft has broken the prop's going to spin no matter what you do, if you've thrown a rod it's going to stop and you couldn't get it to windmill if you flew at mach 1.
What I would recommend is following the engine failure procedure in the POH of your particular aircraft. Generally that is to reduce to glide speed, trim, pick a field and maintain positive control of your airplane throughout. Trying to fly slow enough to get your prop to stop is a dangerous distraction that could lead to a stall/spin excursion, which is far more dangerous than a glide landing, spinning prop or no.
answered 3 hours ago
GdDGdD
33.2k389139
$endgroup$
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
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votes
active
oldest
votes
$begingroup$
A windmilling propeller creates much more drag, by an order of magnitude at least. The obvious example is an autogyro or helicopter in autorotation, which drops like a stone if the rotor stopped.
Drag is a function of blade area for a stopped rotor and a function of disc area for a windmilling one. The difference is most pronounced for large rotors with few blades and almost nonexistent for turbofans.
answered 3 hours ago
Rainer P.Rainer P.
1,01939
$endgroup$
$begingroup$
Last time I looked at a propeller driven aircraft, the prop wasn't pointing vertically upwards. Also your assertion the windmill makes no difference to the drag of turbofans is plain wrong - a fan that is not freely windmilling has MUCH more drag, as has been demonstrated in real life when engine damage in flight locks up the rotors.
$endgroup$
– alephzero
1 hour ago
$begingroup$
A helicopter in a vertical descent under autorotation is not much different from a propeller aircraft in horizontal flight with one engine inoperative. The rotor faces into the direction of travel and crates 'windmill drag'. The only difference is that the helicopter pilot tries to maximize drag in order to save his life. - @alephzero
$endgroup$
– Rainer P.
59 mins ago
add a comment |
$begingroup$
A windmilling propeller creates much more drag, by an order of magnitude at least. The obvious example is an autogyro or helicopter in autorotation, which drops like a stone if the rotor stopped.
Drag is a function of blade area for a stopped rotor and a function of disc area for a windmilling one. The difference is most pronounced for large rotors with few blades and almost nonexistent for turbofans.
answered 3 hours ago
Rainer P.Rainer P.
1,01939
$endgroup$
$begingroup$
Last time I looked at a propeller driven aircraft, the prop wasn't pointing vertically upwards. Also your assertion the windmill makes no difference to the drag of turbofans is plain wrong - a fan that is not freely windmilling has MUCH more drag, as has been demonstrated in real life when engine damage in flight locks up the rotors.
$endgroup$
– alephzero
1 hour ago
$begingroup$
A helicopter in a vertical descent under autorotation is not much different from a propeller aircraft in horizontal flight with one engine inoperative. The rotor faces into the direction of travel and crates 'windmill drag'. The only difference is that the helicopter pilot tries to maximize drag in order to save his life. - @alephzero
$endgroup$
– Rainer P.
59 mins ago
add a comment |
$begingroup$
A windmilling propeller creates much more drag, by an order of magnitude at least. The obvious example is an autogyro or helicopter in autorotation, which drops like a stone if the rotor stopped.
Drag is a function of blade area for a stopped rotor and a function of disc area for a windmilling one. The difference is most pronounced for large rotors with few blades and almost nonexistent for turbofans.
answered 3 hours ago
Rainer P.Rainer P.
1,01939
$endgroup$
A windmilling propeller creates much more drag, by an order of magnitude at least. The obvious example is an autogyro or helicopter in autorotation, which drops like a stone if the rotor stopped.
Drag is a function of blade area for a stopped rotor and a function of disc area for a windmilling one. The difference is most pronounced for large rotors with few blades and almost nonexistent for turbofans.
answered 3 hours ago
Rainer P.Rainer P.
1,01939
edited 2 hours ago
answered 3 hours ago
Rainer P.Rainer P.
1,01939
answered 3 hours ago
Rainer P.Rainer P.
1,01939
answered 3 hours ago
Rainer P.Rainer P.
1,01939
1,01939
$begingroup$
Last time I looked at a propeller driven aircraft, the prop wasn't pointing vertically upwards. Also your assertion the windmill makes no difference to the drag of turbofans is plain wrong - a fan that is not freely windmilling has MUCH more drag, as has been demonstrated in real life when engine damage in flight locks up the rotors.
$endgroup$
– alephzero
1 hour ago
$begingroup$
A helicopter in a vertical descent under autorotation is not much different from a propeller aircraft in horizontal flight with one engine inoperative. The rotor faces into the direction of travel and crates 'windmill drag'. The only difference is that the helicopter pilot tries to maximize drag in order to save his life. - @alephzero
$endgroup$
– Rainer P.
59 mins ago
add a comment |
$begingroup$
Last time I looked at a propeller driven aircraft, the prop wasn't pointing vertically upwards. Also your assertion the windmill makes no difference to the drag of turbofans is plain wrong - a fan that is not freely windmilling has MUCH more drag, as has been demonstrated in real life when engine damage in flight locks up the rotors.
$endgroup$
– alephzero
1 hour ago
$begingroup$
A helicopter in a vertical descent under autorotation is not much different from a propeller aircraft in horizontal flight with one engine inoperative. The rotor faces into the direction of travel and crates 'windmill drag'. The only difference is that the helicopter pilot tries to maximize drag in order to save his life. - @alephzero
$endgroup$
– Rainer P.
59 mins ago
$begingroup$
Last time I looked at a propeller driven aircraft, the prop wasn't pointing vertically upwards. Also your assertion the windmill makes no difference to the drag of turbofans is plain wrong - a fan that is not freely windmilling has MUCH more drag, as has been demonstrated in real life when engine damage in flight locks up the rotors.
$endgroup$
– alephzero
1 hour ago
$begingroup$
Last time I looked at a propeller driven aircraft, the prop wasn't pointing vertically upwards. Also your assertion the windmill makes no difference to the drag of turbofans is plain wrong - a fan that is not freely windmilling has MUCH more drag, as has been demonstrated in real life when engine damage in flight locks up the rotors.
$endgroup$
– alephzero
1 hour ago
$begingroup$
A helicopter in a vertical descent under autorotation is not much different from a propeller aircraft in horizontal flight with one engine inoperative. The rotor faces into the direction of travel and crates 'windmill drag'. The only difference is that the helicopter pilot tries to maximize drag in order to save his life. - @alephzero
$endgroup$
– Rainer P.
59 mins ago
$begingroup$
A helicopter in a vertical descent under autorotation is not much different from a propeller aircraft in horizontal flight with one engine inoperative. The rotor faces into the direction of travel and crates 'windmill drag'. The only difference is that the helicopter pilot tries to maximize drag in order to save his life. - @alephzero
$endgroup$
– Rainer P.
59 mins ago
add a comment |
$begingroup$
I would not follow the advice in the forum. I have heard arguments either way and I have yet to see empirical evidence proving either assertion. The only studies I have seen have been inconclusive on the subject. The chances are good that you couldn't change the prop behavior anyway, if your crankshaft has broken the prop's going to spin no matter what you do, if you've thrown a rod it's going to stop and you couldn't get it to windmill if you flew at mach 1.
What I would recommend is following the engine failure procedure in the POH of your particular aircraft. Generally that is to reduce to glide speed, trim, pick a field and maintain positive control of your airplane throughout. Trying to fly slow enough to get your prop to stop is a dangerous distraction that could lead to a stall/spin excursion, which is far more dangerous than a glide landing, spinning prop or no.
answered 3 hours ago
GdDGdD
33.2k389139
$endgroup$
add a comment |
$begingroup$
I would not follow the advice in the forum. I have heard arguments either way and I have yet to see empirical evidence proving either assertion. The only studies I have seen have been inconclusive on the subject. The chances are good that you couldn't change the prop behavior anyway, if your crankshaft has broken the prop's going to spin no matter what you do, if you've thrown a rod it's going to stop and you couldn't get it to windmill if you flew at mach 1.
What I would recommend is following the engine failure procedure in the POH of your particular aircraft. Generally that is to reduce to glide speed, trim, pick a field and maintain positive control of your airplane throughout. Trying to fly slow enough to get your prop to stop is a dangerous distraction that could lead to a stall/spin excursion, which is far more dangerous than a glide landing, spinning prop or no.
answered 3 hours ago
GdDGdD
33.2k389139
$endgroup$
add a comment |
$begingroup$
I would not follow the advice in the forum. I have heard arguments either way and I have yet to see empirical evidence proving either assertion. The only studies I have seen have been inconclusive on the subject. The chances are good that you couldn't change the prop behavior anyway, if your crankshaft has broken the prop's going to spin no matter what you do, if you've thrown a rod it's going to stop and you couldn't get it to windmill if you flew at mach 1.
What I would recommend is following the engine failure procedure in the POH of your particular aircraft. Generally that is to reduce to glide speed, trim, pick a field and maintain positive control of your airplane throughout. Trying to fly slow enough to get your prop to stop is a dangerous distraction that could lead to a stall/spin excursion, which is far more dangerous than a glide landing, spinning prop or no.
answered 3 hours ago
GdDGdD
33.2k389139
$endgroup$
I would not follow the advice in the forum. I have heard arguments either way and I have yet to see empirical evidence proving either assertion. The only studies I have seen have been inconclusive on the subject. The chances are good that you couldn't change the prop behavior anyway, if your crankshaft has broken the prop's going to spin no matter what you do, if you've thrown a rod it's going to stop and you couldn't get it to windmill if you flew at mach 1.
What I would recommend is following the engine failure procedure in the POH of your particular aircraft. Generally that is to reduce to glide speed, trim, pick a field and maintain positive control of your airplane throughout. Trying to fly slow enough to get your prop to stop is a dangerous distraction that could lead to a stall/spin excursion, which is far more dangerous than a glide landing, spinning prop or no.
answered 3 hours ago
GdDGdD
33.2k389139
answered 3 hours ago
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33.2k389139
answered 3 hours ago
GdDGdD
33.2k389139
answered 3 hours ago
GdDGdD
33.2k389139
33.2k389139
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$begingroup$
I would be surprised if something like a 172 would windmill the prop at all, especially where the air is thinner at 10,000 feet. A lot of times engine failure means the engine locks up. Fuel starvation (more common) can let the prop spin, but there is a lot of force needed to spin a prop. I think a spinning prop is a lot more common on aircraft that don't have direct drive, like a turbo prop than it is for direct driven propellers.
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– Ron Beyer
3 hours ago
$begingroup$
Most GA twins can fly with a feathered prop. They will not windmilling prop. Yes...the windmilling prop generates a HUGE amount of drag.
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– acpilot
2 hours ago
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There are some situations such as model airplanes/ sailplanes with brushless electric motors where the answer is not cut-and-dried and depends on many variables.
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– quiet flyer
2 hours ago
1
$begingroup$
Yes a Cessna 172 can definitely keep the prop windmilling. You have to slow to near stall speed to stop it. After that you can speed up and it won't windmill till you get going rather fast. I'm sure the drag is less with the prop stopped in that case.
$endgroup$
– quiet flyer
2 hours ago
$begingroup$
Air density probably doesn't matter, if we are talking about the tendency of the prop to windmill at any given IAS.
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– quiet flyer
2 hours ago