Unfeathered propeller performance

SteveJeff

SteveJeff

Well-Known Member
I would like to talk a little about the engine failure event where you might not be able to feather. I'm a multiengine student and I would like to know some climb/descent rates figures from your experience, what performance can be achieved in case of an engine failure after takeoff where you can't feather the prop? I guess in light piston twins there is no climb at all, but what fpm descent can you expect?

And what about part 25 large turboprop? Is there such a large drag from an unfeather propeller? I'm thinking about a King Air, Dash8, Saab or an ATR or other big turboprops like these, would you get a high rate of descent like that having no engine at all? I mean, if you have a double engine failure, let's say you get a 1500-2000 fpm glide, but if you have one engine failed and unfeathered, and the other doing full power, what are the figures? Let's assume medium values for weight and outside temperatures.

Thanks!
 
I think it matters a lot. If the drag is very large and you get a 2000 fpm descent, you are in deep problem for sure. But if the penalty in climb performance is just about 500 fpm, as it is usually on small twin piston, you have more choices and you have a chance for a good outcome.
 
SteveJeff said:
But if the penalty in climb performance is just about 500 fpm, as it is usually on small twin piston.
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Uh. Dunno what twin you're flying, but the last piston twin I flew was a Baron, and I believe the penalty for a giant manhole cover over one wing was signficantly more than 500fpm. In any case, I can report with a fair degree of assurance that it gets worse as the spinny things get bigger. The checklist for engine failure combined with NTS failure in the MU-2...well, it didn't exist, but if it had it would have been 1) Bend over, 2) Kiss your ass goodbye.
 
There is no requirement to demonstrate this under FAR 23 or 25 (or the old CAR 3), so you probably will not find this information. At that point you are a test pilot.
 
You're in training. Why not test it at altitude? Fail one, fly Vyse with the prop feathered and with it windmilling. Do so for a good minute or two in each configuration and note the altitude lost over a period of time. Not what you see on the VSI. Land and run the numbers.

As I recall in a Seminole it was on the range of 100-200 fpm. But don't quote me.
 
shdw said:
You're in training. Why not test it at altitude? Fail one, fly Vyse with the prop feathered and with it windmilling. Do so for a good minute or two in each configuration and note the altitude lost over a period of time. Not what you see on the VSI. Land and run the numbers.

As I recall in a Seminole it was on the range of 100-200 fpm. But don't quote me.
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Of course I do. But I'm flying just a DA-42 which is more manageable, 200-300 fpm difference. I'm asking because I'm interested also in other airplanes, bigger props, turboprop engines, which may behave very differently.
 
I'd have to look at the multi PTS again since it's been a while, but is a drag demo not in there? I remember doing one in training and on my checkride. Basically we started with a windmilling prop, gear and flaps down, and slowly undid one by one to see which one gave us the biggest gain in performance. Usually feathering the prop was the biggest performance booster, although we weren't actualy feathering, just using "simulated feather", so I don't know if that would skew the results at all.
 
I'm with BlackHawk, I don't believe you will find the information you are looking for in any of the POH or Flight Manuals due to it not being required. I also don't understand what use you could have for the data, I guess what I'm saying is I can't see how it could ever be applied or used, if you have an engine fail and an engine won't feather you get what you get. Don't get me wrong I have no problem trying and seeing what you get for a bit of trivia but just can't see how it could be useful (what if you were in icing when you lost the engine what happens then). BTW will the DA-42 climb with the engine not feathered? What engines are on the one you are flying?
 
The Dash-8 climbed well the ATR-72-202 was the scariest thing I've done v1 cuts on even feathered.
 
Request said:
I'm with BlackHawk, I don't believe you will find the information you are looking for in any of the POH or Flight Manuals due to it not being required. I also don't understand what use you could have for the data, I guess what I'm saying is I can't see how it could ever be applied or used, if you have an engine fail and an engine won't feather you get what you get. Don't get me wrong I have no problem trying and seeing what you get for a bit of trivia but just can't see how it could be useful (what if you were in icing when you lost the engine what happens then). BTW will the DA-42 climb with the engine not feathered? What engines are on the one you are flying?
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I think it is important to know what actions and options you have in case of EFATO and feather failure. For example, having an engine failure at 1500 ft AGL resulting in a 200 fpm rate of descent you might have a chance to turnback and reach the airport or another spot, try the same thing with a 1500 fpm rate and you are screwed up for sure. At the moment, it is more like my personal curiosity cause I'm not yet on big turboprops. I'm asking because it seems that the POHs don't cover this case, maybe because you don't get a positive climb performance, but I still consider that it worths to know howfar you might get it having a failure which s not able to feather.
Icing? I hope no one takeoffs with airframe icing.

On the DA-42, there are turbocharged diesel engines, 168 hp each. And it can barely climb if you can't feather, but in the worst case, you get a very low rate of descent, which gives you some nice time to manage it at least to find the better place to put it down. If you don't depart on a very short rwy, you get a decent height at the rwy end to reach a field with that low rate of descent, of course if you are not in a very high populated area.
 
SteveJeff said:
I think it is important to know what actions and options you have in case of EFATO and feather failure. For example, having an engine failure at 1500 ft AGL resulting in a 200 fpm rate of descent you might have a chance to turnback and reach the airport or another spot, try the same thing with a 1500 fpm rate and you are screwed up for sure. At the moment, it is more like my personal curiosity cause I'm not yet on big turboprops. I'm asking because it seems that the POHs don't cover this case, maybe because you don't get a positive climb performance.
Icing? I hope no one takeoffs with airframe icing.

On the DA-42, there are turbocharged diesel engines, 168 hp each. And it can barely climb if you can't feather.
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The transport tps I've flown all have two systems for feathering if the primary fails. My advice is to learn all you can on your airplane before you worry about other ones.
 
Cessnaflyer said:
The Dash-8 climbed well the ATR-72-202 was the scariest thing I've done v1 cuts on even feathered.
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You just needed to do more squats and strengthen those legs.
When I transitioned to jets it was me and another ATR pilot. First V1 cut we started doing the "flail" routine. Instructor hit the freeze button and asked "What in the %#*^ are you turbo trash pilots doing???? This airplane does not have 15' wing mounted props. It has tail mounted turbofans."
 
JordanD said:
I'd have to look at the multi PTS again since it's been a while, but is a drag demo not in there? I remember doing one in training and on my checkride. Basically we started with a windmilling prop, gear and flaps down, and slowly undid one by one to see which one gave us the biggest gain in performance. Usually feathering the prop was the biggest performance booster, although we weren't actualy feathering, just using "simulated feather", so I don't know if that would skew the results at all.
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Drag Demo is an element of a multi engine instructor checkride, one of the few things one does not need to do on a multi-engine checkride, although it should have been demonstrated by the instructor at some point.
 
Blackhawk said:
You just needed to do more squats and strengthen those legs.
When I transitioned to jets it was me and another ATR pilot. First V1 cut we started doing the "flail" routine. Instructor hit the freeze button and asked "What in the %#*^ are you turbo trash pilots doing???? This airplane does not have 15' wing mounted props. It has tail mounted turbofans."
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Haha the Dash was much better probably because of the huge tail. Then we went to the ATR and that was the most ridiculous thing I've tried to fly. I wish I actually got to fly the aircraft!
 
V1 cut with Negative autocoarsen (similar concept to autofeather) on the SAAB is pretty tough, and at flaps 15 is really tough. You have to manually feather after the gear is up to get the required V2 climb performance.

Enroute is a hugely different scenario. First off you are asking about performance of a dual engine flameout with both props feathered versus single engine failure with an unfeathered prop and the other motor working, apples and oranges. i'll take a motor running over a dual flameout any day for obvious reasons. In the SAAB if it does not feather with the condition levers enroute (autocoarsen not armed above 1000 FT, rapid action not required in the enroute phase) you still have a manual feather pump to bring it to feather. So there are layers of redundancy.

Don't know the exact figures but you can assume a drift down to the single engine service ceiling. Part 121 route planning has to guarantee terrain clearance for this type of event, although i dont think they have to address failure to feather. Anyhow with one running you will be able to hold altitude at some point, not hit anything, and you will be able to fly a controlled descent on an ILS (700 fpm).
 
Blackhawk said:
And altitude (WAT).
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It's not burning fruit, therefore, it doesn't count.

SteveJeff said:
And what about part 25 large turboprop? Is there such a large drag from an unfeather propeller? I'm thinking about a King Air, Dash8, Saab or an ATR or other big turboprops like these, would you get a high rate of descent like that having no engine at all? I mean, if you have a double engine failure, let's say you get a 1500-2000 fpm glide, but if you have one engine failed and unfeathered, and the other doing full power, what are the figures? Let's assume medium values for weight and outside temperatures.
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The drag from a 10.5-foot diameter propeller that is windmilling is like having a 10.5-foot diameter disc affixed to the nacelle, so yes, it is...significant.

The Brasilia doesn't climb so well with an inop engine-propeller not feathered. Like, hardly at all. You'll squeak out a positive rate of climb, and then you MUST get the prop feathered if you want to meet V2 climb requirements. Directional control is a handful as well. We have autofeather for a reason for takeoff and we test it before every. single. leg. Engine failure-propeller not feathered and prop overspeed are the two powerplant-related emergencies that get action (namely, securing the propeller) below 1,500'.

That said, performance is governed by both Part 25 (the airplane must be capable of X) and Part 121 (you must operate the airplane like this, so that it is capable of X). Our onboard performance manual gives us altitudes that we can maintain on one engine with the inoperative engine secured based on temperature and gross weight. Dispatch additionally files us for routes that guarantee we will meet the single engine requirements of Part 121. Basically the procedure is to set max continuous power on the operating engine, once you have the engine secured, and fly at Vfs (think, basically, Vyse) until you stop descending.

Blackhawk said:
You just needed to do more squats and strengthen those legs.
When I transitioned to jets it was me and another ATR pilot. First V1 cut we started doing the "flail" routine. Instructor hit the freeze button and asked "What in the %#*^ are you turbo trash pilots doing???? This airplane does not have 15' wing mounted props. It has tail mounted turbofans."
Click to expand...
The first V1 cut I did in the Brasilia surprised me, coming from a jet.

"HEY WHOA!"
 
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