A Surprising Amount of Force May be Needed to get to Best Glide Speed

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pelmet
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A Surprising Amount of Force May be Needed to get to Best Glide Speed

Post by pelmet »

The question is.......

In which direction. I thought this article was interesting......

"If the failure occurs shortly after takeoff, when you are climbing out, it can be surprising just how much you have to push the yoke forward to maintain best glide speed and avoid a stall. It’s an excellent thing to practice, repeatedly, at a safe altitude and perhaps with an instructor on board."

"On the other hand, at cruise, it can be surprising (depending on aircraft type) how much you have to haul back on the yoke to keep from diving when thrust is gone. Maintain altitude while the plane decelerates toward best-glide speed."


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Pilotdaddy
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Re: A Surprising Amount of Force May be Needed to get to Best Glide Speed

Post by Pilotdaddy »

Say you're taking off and trimmed for 70kts. You lose your engine... wouldn't the plane pitch down by itself and fly.... 70kts?

I can see the cruise bit, however. You're trimmed for 100 kts, the engine goes... it dives and flies 100 kts and yes, back pressure has got to be added.
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iflyforpie
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Re: A Surprising Amount of Force May be Needed to get to Best Glide Speed

Post by iflyforpie »

No. The trimmed speed depends on power setting. Generally, more power will reduce the speed, and less power will increase it.

This is why you have to pull back to best glide, and on a go around you have to push very hard to get to best rate.

I cheat. I know where the trim wheel has to be and move it there for specific power settings, configurations, and speeds rather than fighting the controls.
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photofly
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Re: A Surprising Amount of Force May be Needed to get to Best Glide Speed

Post by photofly »

Pilotdaddy wrote: Sun Nov 15, 2020 12:29 pm Say you're taking off and trimmed for 70kts. You lose your engine... wouldn't the plane pitch down by itself and fly.... 70kts?
Some aircraft have significant pitch/power coupling, some have very little. Most aircraft will be trimmed for a faster speed power-off than power on.

A sudden power reduction will cause a phugoid: the plane will pitch down and accelerate past its new trim speed (which may itself be faster than it's old trim speed), before slowing up again. In the event of a low-altitude power loss, simply place the pitch at the correct attitude for the airspeed at which you wish to glide.

There may be some aircraft that need a "surprising amount of force (push) to get to best glide speed" but it's not the case in any common single engine trainer. It's hard to imagine why it would the case in any other aircraft, either.

on a go around you have to push very hard to get to best rate.
Again, this depends on the pitch/power coupling of the aircraft in question.
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Last edited by photofly on Sun Nov 15, 2020 1:35 pm, edited 2 times in total.
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Re: A Surprising Amount of Force May be Needed to get to Best Glide Speed

Post by photofly »

double post
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Re: A Surprising Amount of Force May be Needed to get to Best Glide Speed

Post by PilotDAR »

it can be surprising just how much you have to push the yoke forward
I'm allowing that the "how much" may be more the displacement of the pitch control, rather than the force to get it there. Bear in mind, that there are certification standards for control force, so a certified plane won't exceed that force. Rather, it may be very surprising how far you need to lower the nose, so how much change in pitch attitude from nose up climb, to nose down glide, may be required - very quickly.

So, yes, practice this. I still cringe at the term "best glide speed". Practice in the planes you fly, you will probably find that a comfortable forced landing is flown from a faster than flight manual "best glide speed". Yes, the best glide speed, corrected for actual weight, is just what you want to be flying if it quits, and you want to make it to the coast, but you may find it on the slow side, requiring a very precise flare, if you're actually flying a power off landing. I practice forced landings lots, in different types. Once I have chosen my spot, and committed to land, it is likely that I'll fly faster than the published best glide speed to the entry to the flare, slipping and applying flaps after that to get to where I want to be (crossing the fence) to land.
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