Primarily for general aviation discussion, but other aviation topics are also welcome.
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By Miscellaneous
#1778433
rf3flyer wrote:@Miscellaneous Down to my piloting skills, I'm sure. :wink:

Exactly, that's what makes it interesting. Given the time you have owned the aeroplane and your experience of it, a halving/doubling of the height lost is very significant.

Take someone much less familiar with the aeroplane, throw in the additional pressures of doing for real, possibly with the distraction of a passenger and it's anyones guess how big the factor between actual and possible will be. Let's be very conservative and say your first effort could be replicated by others for real. For the average 10:1 glide ratio aeroplanes that's 800'.

That's a significant gamble to be taking.

At what point after take off does an EFATO become an engine failure in flight? :D
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By rf3flyer
#1778446
@Miscellaneous
I wryly alluded to my piloting skills, or lack thereof, but although I have flown a little in the last couple of weeks there is no doubt I'm a bit rusty. But in truth I thought it might go better than it did.

I'm not kidding myself that if it happened to me for real I would do any better than my worst example, possibly I'd do worse, but having tried it I at least have some sort of idea where my cutoff might be. I also expect that were I to go and fly some more tests (I probably will) I could improve on my performance but given a real failure it would probably come out worse. The danger with honing the skill is that I might be suckered into thinking my best ever practised performance is what I will achieve come the day.

"At what point after take off does an EFATO become an engine failure in flight?"
I'd opine when I start to pull back from full throttle to something more like cruise climb, which I think for me is generally about 500 to 700ft AGL. I'm not normally looking at the altimeter then.

Perhaps though, one or two others, @Kemble Pitts for example, may be encouraged to try this in their own aircraft, and if they do it would be good to read how they got on. Done at height it's not risky.
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By cotterpot
#1778455
rf3 flyer - I did exactly the same thing this morning in our C172.
First noted rates of decent in a straight line at various throttle settings/flaps at 65 knots and then I went for two 220 deg 'turn back' manoeuvres, from height, one with no flaps and one with 10 deg.

Max 15 deg bank resulted in around 700ft loss each time. Some of that may have been my flying, trying to hold 65 knots.

It didn't change my mind and I have fields/areas at my home base in mind should it all ever go quiet. :thumleft:
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By Miscellaneous
#1778478
@rf3flyer makes perfect sense. I think you have convinced me the chances of it working out is a bit of a lottery. No doubt odds of success being increased with practice.

But then if you consider EFATO 'ends' at 500-700' a turn back from a 'true' EFATO is a no no for 10:1 aeroplanes. I guess another big consideration is runway length and relative position at time of failure. Strange airfield also influences outcome.

Interestingly @cotterpot had similar supporting results.
By profchrisreed
#1778480
One further thing to consider - those tests were with throttle closed, not engine stopped. I believe a stopped prop causes significant extra drag, so real life numbers would probably be appreciably worse.
By Longfinal
#1778500
cotterpot wrote:rf3 flyer - I did exactly the same thing this morning in our C172.
First noted rates of decent in a straight line at various throttle settings/flaps at 65 knots and then I went for two 220 deg 'turn back' manoeuvres, from height, one with no flaps and one with 10 deg.

Max 15 deg bank resulted in around 700ft loss each time. Some of that may have been my flying, trying to hold 65 knots.

It didn't change my mind and I have fields/areas at my home base in mind should it all ever go quiet. :thumleft:


For a turn with minimum height loss, you should be doing a lot less than 65 kts
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By rf3flyer
#1778522
@profchrisreed Of course you are right about the engine still turning in a practice, but I believe you are wrong to say "...a stopped prop causes significant extra drag..." Also, having on many an occasion shut down my engine in flight and deliberately stopped the prop I can say quite definitively that the glide is better prop stopped. Also, my Flight manual lists a throttle setting of 1700RPM for 'propellor invisibility' which I take to mean that the prop is neither pulling nor holding back.

@Longfinal I have been reflecting upon all this since yesterday's flight and I agree with your comment about speed. 60kts is my normal cruise climb BUT my best glide is 56 kts. Once in the 'glide' I should have trimmed for that, pehaps even less to tighten the turn. I didn't. Didn't even think about it either beforehand or in the air.

A further consideration for my initial results is that yesterday was a bit windy and unstable though I did fly the tests across wind above the downwind end of a largeish body of water. So, as I said earlier, I will try this again with a rather more informed approach and see what I get.

This has been one of the more thought provoking and involving threads for while. :thumright:
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By CherokeePete
#1778524
profchrisreed wrote:I believe a stopped prop causes significant extra drag...

This is incorrect.

A stopped prop is less draggy than a windmilling prop, and a feathered prop is less draggy than an unfeathered stopped prop.

:cyclopsani:
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By foxmoth
#1778530
="cotterpot"
Max 15 deg bank resulted in around 700ft loss each time. Some of that may have been my flying, trying to hold 65 knots.:


I am surprised you got away with only 700’ like that, optimum is reckoned to be 45 deg!
Last edited by foxmoth on Tue Jun 23, 2020 8:12 am, edited 2 times in total.
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By Miscellaneous
#1778533
@rf3flyer might it be worth trying to establish the ground distance covered in the turn? Dependent on certain factors it is possible a turn could be made at some of the shorter fields only to overshoot the runway and land off field with a tailwind? :shock:
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By Trent772
#1778540
Not read all the thread, if I missed a reference, sorry.

A great article in the EAA mag a month or so ago. They did calculations of rate of climb v rate of glide on a Cherokee. 4 altitudes out of the airport up to 1,000', none were successful as a return to the runway.
By Rjk983
#1778566
@rf3flyer you said you practiced at 2000’ - don’t underestimate the willpower required to fight the urge to pull the wings off if you are doing this close to the ground in an aircraft with a more usual GA glide ratio.

On a UAS in a previous life I was taught it and practiced it at 3000’ plus in the Bulldog, it all seemed easy enough. Then the QFI demonstrated it on departure - the view went from lovely blue sky to very dark green grass and we were pointing very steeply nose down, about 40 degrees of bank and the ground just kept getting bigger and bigger in the window. If I had been doing this solo I”m pretty sure the urge to pull would have been too great and I’d have spun in. Luckily I only went to one airfield where landing ahead wasn’t an option after that but I’m still not sure if I’d have risked it if it all went quiet.
Last edited by Rjk983 on Sat Jun 27, 2020 11:23 pm, edited 1 time in total.
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By MichaelP
#1778635
Grass looks a bit shaggy: Its surprising the retarding effect of grass over 4inches long...........

Peter

That’s the field the other side of the hedge. If you have an engine failure just after takeoff that’s where you will end up.
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By Miscellaneous
#1778636
MichaelP wrote:
Grass looks a bit shaggy: Its surprising the retarding effect of grass over 4inches long...........

Peter

That’s the field the other side of the hedge. If you have an engine failure just after takeoff that’s where you will end up.

Maybe like me @PeteSpencer thought it looked as though someone had already landed there? :wink:
By CherokeePete
#1778639
CherokeePete wrote:
profchrisreed wrote:I believe a stopped prop causes significant extra drag...

This is incorrect.

A stopped prop is less draggy than a windmilling prop, and a feathered prop is less draggy than an unfeathered stopped prop.

:cyclopsani:

Since I cannot edit my post I shall quote it in full :roll:

The rationale for this is because the coefficient of drag on a windmilling propeller is calculated using the "disc" diameter of the spinning propellor; whereas for a stationary proportion the calculation is against the chord of the propellor facing airflow. Obviously a feathered propellor has a much reduced chord leading to it being optimum for drag reduction.

:cyclopsani:
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