Trim all the way up for best glide

Wade

Wade

Pre-takeoff checklist
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Boise Idaho
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Maxcat
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I heard somebody say you can trim all the way up and a plane will fly at best glide.

So I went out and tried it in a 172 and it worked. Engine at idle and it glided right along at about 70knots.

Neat trick to use for a engine out situation so you can concentrate on emergency checklist.


Next on the list to try is practicing impossible turns at high altitude.
 
Do you think your trim trick will work the same way at gross weight and the CG at the aft limit?
 
Not sure but I'll have to test that also.
 
It will get you close.......certainly not exact. It is a good technique, lets you focus on trouble shooting and finding a good landing spot.
 
My primary flight instructor told me "4 full strokes of up. If you have time later check IAS." This was in C-172N or M models. Newer instructor showed me the full up trick. Again in a lightly loaded, forward CG (two of us in the front) C-172. It's a reasonable start in a C-172. I have no idea how it would work in other airplanes.
 
Only thing I see is that gliding at 70kts in a 172 is 5kts faster than the stated book value of 65kts. In a true emergency, you'll want to hang around Best Glide as closely as possible.
 
Or just trim for best glide. A good practice is learning how much to spin the trim wheel to get you close.
 
Stewartb said:
Do you think your trim trick will work the same way at gross weight and the CG at the aft limit?
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It's pretty hard to get the CG all the way to the aft limit in a 172, but I've verified it works fine at max gross with a hefty guy in the back seat. Actually a little better, as 70 KIAS is a bit on the fast side.

As long as you keep the flaps up (and in a 172RG, the gear up as well), it seems to work nicely.

It also works on 177s and 182s (past 1970 or so). I haven't tried it on the 206 yet, but I'm going to have a hell of a time getting that up to max gross with only four seats and no cargo pod.
 
Ryanb said:
Only thing I see is that gliding at 70kts in a 172 is 5kts faster than the stated book value of 65kts. In a true emergency, you'll want to hang around Best Glide as closely as possible.
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Like when they asked Bob Dole if he wore boxers or briefs, the real answer to whether you want to be exactly on best glide speed or a little fast or something else is, "Depends."
 
Why come up with "ballpark" tricks like this, instead of just flying the airplane? Full nose-up trim, in my experience is far too much to maintain best glide in a Skyhawk R model, or a Cutlass RG. If you're practicing this to a low approach, or a touch and go at an airport, this also puts you in a position where an unsuspecting pilot is at risk for an elevator trim stall.

Maintain altitude, fly the airplane to best glide, and trim to relieve control pressure. 70 knots will seriously degrade your glide ratio. At 65 Knots, a 172 at 2300 pounds will descend at about 500-600 feet per minute. Let's say you're at 2500 feet AGL. You have 5 minutes before you touch down. If you cant spare 10 seconds to slow to 65, and another 5 to properly trim the airplane, then there's a larger issue at hand beyond the engine failure. There's no reason to get lazy and to let good flying techniques fall to the wayside, especially in an emergency.
 
I'd just pitch for best glide and quickly trim the pressure off, or if you have a newer autopilot, pitch for best glide and engage IAS mode
 
That trick is money in the 172...tried it in my Cherokee 140 and it doesn't work :(
 
Another handy trim "trick" on 172 is for steep turns. 2 full turns is almost exactly what you need to hold altitude on a 45deg bank if plane has been trimmed for S&L at normal cruise speeds.
Makes steep turns very very easy (if you're still at the point where they are challenging...)
 
GrahamC said:
If you cant spare 10 seconds to slow to 65, and another 5 to properly trim the airplane, then there's a larger issue at hand beyond the engine failure.
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In the case of the OP, it'd take a little longer to trim the airplane...unbuckling and crawling in the back takes time. ;)
 
mtuomi said:
Another handy trim "trick" on 172 is for steep turns. 2 full turns is almost exactly what you need to hold altitude on a 45deg bank if plane has been trimmed for S&L at normal cruise speeds.
Makes steep turns very very easy (if you're still at the point where they are challenging...)
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Yep I have tried this and it works great.

As for the ahole who basically said I'm stupid, lazy, and have no flight skills because I tried something that gets me in the ballpark in a instant.

If my engine goes out I want to focus on getting it restarted not trimming to within 2 knots of best glide. So I will save 8.7 seconds by grabbing all the trim and then use my limited brain power to start figuring out what my problem is. If you dont like it well you can fly your flight simulator in your mom's basement anyway you like and I'll fly my plane how I like.
 
And it may not work for beans in aircraft other than a 172, although I would expect Cherokee 140/160 to be pretty close because they're benignly mannered training planes. And it will vary by CG location and load.

If you think it might be useful, TRY IT BEFORE YOU NEED IT to see if it works in your airplane.

John
 
MauleSkinner said:
The OP trimmed full nose up and got 70. To trim for 65 would take more nose up trim, but he's already full nose up, so he'd have to change the CG to trim for 65.
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If he's saying that he was UNABLE to trim the airplane to 65 Kts, then something is amiss. In 600 hours of flying 172 models M, R, S and RG, I've never once been unable to trim the airplane to 65 knots in a power off condition.
 
GrahamC said:
If he's saying that he was UNABLE to trim the airplane to 65 Kts, then something is amiss. In 600 hours of flying 172 models M, R, S and RG, I've never once been unable to trim the airplane to 65 knots in a power off condition.
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Nowhere did I say UNABLE to trim to 65 I can trim to whatever speed the aircraft is capable of. I grabbed full up trim in a simulate engine out and got about 70 knots on that day with that wind in 2 Seconds. how someone can disagree that that is not a useful thing to know and use is just being obnoxious.
 
Wade said:
Nowhere did I say UNABLE to trim to 65 I can trim to whatever speed the aircraft is capable of. I grabbed full up trim in a simulate engine out and got about 70 knots on that day with that wind in 2 Seconds. how someone can disagree that that is not a useful thing to know and use is just being obnoxious.
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If it's all the way up at 70, how would you trim it for 65?
 
Wade said:
Nowhere did I say UNABLE to trim to 65 I can trim to whatever speed the aircraft is capable of. I grabbed full up trim in a simulate engine out and got about 70 knots on that day with that wind in 2 Seconds. how someone can disagree that that is not a useful thing to know and use is just being obnoxious.
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It's not useful; It's careless. Skill in flying, especially emergency procedures is not something to find shortcuts around. Practice, and learn to do it right.
 
GrahamC said:
It's not useful; It's careless. Skill in flying, especially emergency procedures is not something to find shortcuts around. Practice, and learn to do it right.
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So... one shouldn't trim for best glide, as it's not useful and even careless?

I disagree...knowing your airplane is what a responsible pilot does.
 
MauleSkinner said:
So... one shouldn't trim for best glide, as it's not useful and even careless?

I disagree...knowing your airplane is what a responsible pilot does.
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Quite the opposite. One should always trim for best glide from altitude. In a 172, your best glide will never be 70kts unless you've severely exceeded the airplanes max gross weight.
 
GrahamC said:
Quite the opposite. One should always trim for best glide from altitude. In a 172, your best glide will never be 70kts unless you've severely exceeded the airplanes max gross weight.
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So why do you say that knowing enough to go straight to that best glide trim setting without wasting time, or knowing that you can't trim for best glide in the case of the OP (although I agree he doesn't seem to understand that) is "not useful" and "careless"?
 
Knowing to trim for best glide is an imperative skill. I'm saying that fill nose up trim in a 172 will not achieve that. Rather, maintaining altitude while slowing to best glide, and then trimming to relieve control pressure it the best practice. Defaulting to full nose up trim is not useful and is careless.

How do you think an examiner or ASI would react to a Private Pilot applicant responding to a simulated engine failure by running the trim wheel to full nose-up and then going straight to a checklist instead of exercising proper piloting skills and using critical thinking to react to an adverse condition?

Edit: That last question is not meant to imply that DPEs or ASIs are the holy grail of good decision making, but I'd be hard-pressed to find someone to disagree that they are both, overall, representative of good judgement and skill evaluation.
 
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GrahamC said:
Knowing to trim for best glide is an imperative skill. I'm saying that fill nose up trim in a 172 will not achieve that. Rather, maintaining altitude while slowing to best glide, and then trimming to relieve control pressure it the best practice. Defaulting to full nose up trim is not useful and is careless.
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Ok...how is the OP going to trim for best glide? And what pitch trim setting will he ultimately end up with in doing that?
How do you think an examiner or ASI would react to a Private Pilot applicant responding to a simulated engine failure by running the trim wheel to full nose-up and then going straight to a checklist instead of exercising proper piloting skills and using critical thinking to react to an adverse condition?
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What critical thinking is missing? Speaking as an examiner, if the applicant doesn't have to waste time establishing best glide and can transition directly to dealing with the problem, I'm all for it. Seems like the critical thinking has been employed by learning to use the airplane's inherent traits to reduce workload on the pilot.

Seems to me what you're suggesting is like saying that an instrument pilot should intentionally establish incorrect pitch and power settings when intercepting the glide slope so that he can use good bracketing procedures.
 
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I think I described pretty well the process one would use to trim for best glide. The OP already established that with full nose up trim he achieved 70 knots, which is not best glide in the C172.

While I'm not an examiner, I have performed dozens of end-of-course stage checks as an Assistant Chief Instructor. I would never have completed a stage check for an applicant who went straight to full nose-up trim. I'll be happy to ask around some local examiners here, and see what they say. I've been wrong before, and I'll be wrong again, but I don't see how the facts here allow for that:

1. OP stated that with full nose up trim, he achieved 70 Knots.
2. C172 Best glide speed is 65 Knots.
3. I posit that It is perfectly possible to trim the airplane to 65 knots, and in doing so, a pilot will not achieve full nose-up trim.
4. Additionally, I state that applying power from a full nose-up trim setting presents a hazard, which, based on a pilot's experience and training, may pose an undue risk of elevator trim stall.

Which of these items do you disagree with?
 
GrahamC said:
I think I described pretty well the process one would use to trim for best glide. The OP already established that with full nose up trim he achieved 70 knots, which is not best glide in the C172.

While I'm not an examiner, I have performed dozens of end-of-course stage checks as an Assistant Chief Instructor. I would never have completed a stage check for an applicant who went straight to full nose-up trim. I'll be happy to ask around some local examiners here, and see what they say. I've been wrong before, and I'll be wrong again, but I don't see how the facts here allow for that:

1. OP stated that with full nose up trim, he achieved 70 Knots.
2. C172 Best glide speed is 65 Knots.
3. I posit that It is perfectly possible to trim the airplane to 65 knots, and in doing so, a pilot will not achieve full nose-up trim.
4. Additionally, I state that applying power from a full nose-up trim setting presents a hazard, which, based on a pilot's experience and training, may pose an undue risk of elevator trim stall.

Which of these items do you disagree with?
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#3. If the OP had full nose up trim at 70 knots, he would not be able to trim for best glide.

#4 is irrelevant. If trimming full nose up for 70 is dangerous, some other trim setting for 65 would be worse.
 
In which region are you an examiner? If you're stating that it is not possible to trim a Cessna 172 for best glide, I'd like to steer clear of your part of town.
 
GrahamC said:
In which region are you an examiner? If you're stating that it is not possible to trim a Cessna 172 for best glide, I'd like to steer clear of your part of town.
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I'm stating that, according to the OP, HIS 172 could not be trimmed for best glide without mechanical rerigging or moving the CG.

For the record, I have been stating this all along, including in direct response to your "I don't follow" post. Maybe you should read more thoroughly the posts to which you're replying.
 
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The utility? Just remembering that full trim gets me close to best glide is enough (I did not know that...maybe I should have, but I never trimmed past hands-free....never looked to see how much nose up trim was left...but NOW I know). So in an actual emergency, I can run it up to or near full trim, then fine tune for best glide.

One less thing to "think" about, and become automatic with. Then simultaneously look for my best field as I'm trimming to hands off, then run my flow and the checklist.
 
This is seriously concerning that this is a thing that people think will work. Next time I'm in a skyhawk, I'll make a video of this to demonstrate how completely and utterly wrong this notion of "full nose-up trim for best glide" is.
 
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