Forget Best Glide Speed- Just Trim Full Nose Up!
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- Опубликовано: 29 сен 2024
- Forget Best Glide Speed- Just Trim Full Nose Up! Testing Trimming for Best Glide
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FlyWire is about exploring flight and the freedom this incredible experience brings us on a personal level. Flying has always captured the imagination and excitement of living life to its fullest. Hi, I'm Scott Perdue. In a former life I flew the F-4 and F-15E, more recently I retired from a major airline. I've written for several aviation magazines over the years, was a consultant for RAND, the USAF, Navy, NASA as well as few others, wrote a military thriller- 'Pale Moon Rising' (still on Kindle). But mostly I like flying, or teaching flying. Some of the most fun I had was with Tom Gresham on a TV show called 'Wings to Adventure". We flew lots of different airplanes all over the country. Now with FlyWire I want to showcase the fun in flying, share the joy and freedom of flight and explore the world with you. Make sure you subscribe if you want to go along for the ride!
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Great vid! I think you are correct. No AP might produce acceptable results for us puddle hopper 172 pilots.
How hard is it to remember best glide speed? How about not hard at all, and it's something every pilot should know about the plane they are flying.
And its normally pretty close to Vy
In what airplane? Not a Bonanza.
Every pilot can benefit from some sailplane time .
Agreed. While I was surprised to see the oscillations in your test aircraft, perhaps just knowing the 'best glide' speed (you began to tell us what that was before another oscillation took your attentions away) and trimming to that might be a lot simpler. Having been in the situation of trying to make it to the runway by slowing too far below 'best glide', I am now a devoted fan of going by the numbers.
Scott was testing a theory held by some that full aft trim will result in best glide speed. Never was it mentioned to disregard memorizing best glide speed . He demonstrated that in the case of a Bonanza full aft trim does not provide best glide . I'd bet the outcome will be similar in most other types as w3ll
Better to trim to best glide (that way you know you've nailed it), while looking for a landing site.
Great job....I don't think that would work on my aircraft either.
When I did my last CFI renewal, they showed a video of a C172 where they did exactly as you’re demonstrating. Seemed to work in the 172, but I’ve never tried it.
It is NOT a blanket technique.
@@FlyWirescottperdue didn’t seem to work in my Mooney either
It’s not a blanket technique… but in both the 172 and 152 best glide is full nose up trim, thereabouts.
@@timransby1774 Full trim results in being 10-15% too slow in the 172m
@@mytech6779 maybe in yours, not in mine
All these Engine out tests and stuff gave me a new Idea for Emergency Landing system (like the cirrus CAPS,)
Tho my idea not related to parachutes or slowing plane in anyway in fact its the opposite.
But thats all im saying, Could be lots of money in this idea :P just need to design and patent it.
HAHA Makes CAPS system seem pointless unless plane is damaged and needs chute.
Could make Various Models of my system with Varying Time of Use Available.
Go for it!
Totally agreed! In my old C172K model, the trick works, one of the CFI's I had in training told me about that...But I'd never assume it would work in any other airplane. I flew a Cherokee-180 for about 100 hrs before I got my Cessna, don't recall ever trying this trick in that plane. Of course, in the Cherokee, you pull the power and you are descending immediately. In the C172 it floats a bit and things about it, before gently descending...🤣
Cherokee 180 is nose heavy, but it can glide allmost the same distance too. At 82, not 65 mph like C172 of that era.
@@emergencylowmaneuvering7350 The one I was in was a 1965, 180-C, yep, 82 sounds about right. It was a heavier plane. It was a unique in-betweener though that Cessna didn't have an answer too. It could go a little faster and carry more weight while still only a 4 cyl. Had to go up to a C182 for that but then you were slurping the gas. Johnson Bar flaps were easy and fast. The window crank elevator trim in the roof always befuddled me! 🤣. I didn't like only the one door, on the wrong side. I'm a lefty and have mild CP so it was always a contorted crash out of the thing 😂.
@@ph5915 182's are priceless. Had a student that bought a 77 model, 25 years ago and stills has it. He learned on my Cherokee.
@@emergencylowmaneuvering7350 No argument about 182s, I just don't want to pay for the gas with a big engine. Before I was laid off several years back I was flipping a coin over either a Vans RV-9A or a little tailwheel. I have a few hours in a tailwheel and it's such a hoot! But insurance would be $$$.
@@ph5915 You can use Flex Temp when cool or cold temp. Dont use full power to take off if not needed. Cruise at lower rpm too.
Will this work on my RC airplane when i fry the 8th brushless bang good motor this month?
I'll try it in a DA40. See if it makes a good parachute. Doubt it. Expect a wing to drop.
The reason aircraft doesn’t (or shouldn’t) stall is because it’s designed with longitudinal stability in mind. But the stability is on a knife’s edge due to the low airspeed. A gust of wind can easily upset the stability and the loss of airspeed would cause a nose down pitch which after many oscillations (I suspect I haven’t done this myself) the aircraft will return to a stable straight and level condition.
The speed that the Trim setting was setting up was WAY below Best Glide speed. It was a total fail in this case.
As they say, just fly the numbers.
Why would Beech design a trim setting that would lead to a stall? It seems excessive.
During my CPL training. I had an instructor demo a rapid spiral descent, by just using full back trim, to keep the airspeed steady. We ended up with a massive rate of descent, in a 182, but the overspeed and stall were never approached. I've never tried it since, so not sure if it would work in any plane.
It's a bad idea. Try full nose up trim in a Pitts Special S1S and see how that goes. We trim for cruise speed and leave it there 100% of the time. You need the feedback pressure on the control stick for landing.
I knew that wouldn’t work! 😂 Just placard the best glide speed on the panel!
My nickel on the grass is to note two things.
(1) Your best glide speed is 105 knots at max gross weight, and it reduces as a function of the square root of the weight difference from max gross weight. Your flight was ballpark about 81% of max gross, so best glide for your weight would have been about 90% of 105, or about 94 knots.
(2) My understanding of max nose-up trim is that it gets the airplane to the slower min sink speed, NOT the best glide speed. Min sink speed is typically 15% slower than best glide, so probably about 80 knots for your flight.
In other words, I think that the full nose-up trim test worked almost exactly the way it should have. A fair test to me is "near" full nose-up trim and that should get any Part 23 airplane to very close to best glide speed for the weight, even though the actual speed will vary from flight to flight depending on loading.
Thanks Dean for your observations. Could you show me in the Bonanza POH where it says to adjust speed for best glide based on weight? In truth these speeds are targets and variation does not significantly impact performance. There is, however, a significant difference between Best Glide and Min-sink. Notably, there is NO value for Min-sink in the POH.
@@FlyWirescottperdue Only a small of airplane POHs publish the difference, even though it is a fundamental aerodynamic principle that is one of those speeds that vary with weight on the square-root rule, just as stall speed and maneuvering speed (VA) do. Cessna for example publishes just one speed for the 172 presumably to keep it simple for beginner pilots and because the weight doesn't vary too much, but does publish different speeds for different weights for the 206 and Caravan, which can have huge weight differences from one flight to another and so it can be a significant difference. Almost no one publishes min sink speed, except Columbia did for the 350 & 400, which Cessna continued when they bought those types.
The published numbers for the Cessna 350 are 106 KIAS and 94 KIAS for best glide at 3400 lbs and 2500 lbs respectively, and 85 KIAS and 80 KIAS for minimum sink for the same weights. That's a difference of about 15 to 20 percent at identical weights for "best glide" and "min sink".
Feel free to cross-check my square-root rule for any airplane whose POH shows different best glide speeds for different weights but be careful to convert properly between INDICATED airspeed and CALIBRATED airspeed, as the real rule is based on CAS, and so the conversions for each kind of airplane between CAS and IAS come into play, and if you don't account for that it might appear that my math is off. (Note: The Cirrus SR22 and SR20 might not abide by the rule because their constant-speed prop is not independently controllable and thus behaves differently due to an abnormally large prop drag affect.)
Assuming for discussion purposes that I am right about this rule, there is an eye-popping implication for pilots who fly at the "the" best glide speed -- which is actually the max-weight best glide speed -- when at significantly lighter weights, such as when flying a plane like a Bonanza relatively light such as you did in this video. In order to achieve the higher speed (say, 105 KIAS) when a lower speed is aerodynamically better (roughly 94 KIAS for your flight do to my rough calculations), the sink rate must be higher and hence you are giving up significant glide performance.
So here's my prediction if you want, but only if you want because it's your airplane. Make two test flights with everything as equal as possible except for the weight. For one flight, try to be as close to max gross weight as possible, and note the sink rate at 105 KIAS as precisely as possible, noting how long it takes to descend about 2,000 feet. For the other flight, and these can be done in any order, fly the airplane about as light as you would ever fly it, so I'm thinking a solo flight, fuel endurance about 1 hour, and no cargo/baggage. Do a weight calculation before the flight, and note the weight as a percentage of max gross. For example, if your max gross is 3400 and your actual weight for the test will be right around 2900, that's 85.3% of max gross, and the square root of 85.3% is 92.3%. Assuming no difference between CAS and IAS, 92.3% of 105 KIAS is 97 KIAS. So do the test at two different speeds, 97 KIAS and 105 KIAS. At the lighter weight, it takes more sink rate to achieve 105 KIAS than it did on the weightier flight, and at 97 KIAS it will be less sink rate. But since glide ratio is a ratio of forward speed to "down" speed or sink rate, the ratios of the different best glide speeds at different weights should be the same though of course real-world tests will always have a small amount of noise in the data. If your lightweight flight can be done at about 2,550 lbs, that's 75% of max gross, implying a best glide speed 86.6% of normal, or about 90 knots KIAS assuming no IAS/CAS error. That will make for a big difference if you're at 2,550 lbs and try to glide at 105 KIAS, as the sink rate will be much higher -- and hence the glide ratio will be much worse -- than the same 105 KIAS at the heavier weight.
If you do go out and test this, it's at your own risk and please do it a few thousand feet AGL while near or over a suitable airport in case the engine doesn't want to come up from idling for a couple of minutes at altitude during the test.
Finally, the simplistic scientific explanation for why best glide speed varies as a function of the square-root of the weight difference for any airplane (unless something else is in play such as for the Cirrus SR20 and SR22) is that best glide speed is achieved at the point where total drag is lowest, which is where the curves for induced drag and parasite drag cross, as explained in several places including pages 5-5 and 5-6 of the current Pilot's Handbook of Aeronautical Knowledge. Induced drag is a function of lift, and lift is a function of weight, with lift varying as a function of the square of the airspeed. If the weight is reduced, so does the induced drag curve, and so the induced/parasite crossover point slides to the left on the x-axis of Figure 5-6 in the PHAK. Hence the adjustment in best glide speed as a function of the square root of the weight difference from max gross weight.
@@zidoocfi Dean, thanks for your comments. You are right, but not for the reasons you think you are. In actuality, best glide is not affected by weight. Best Glide is attained at a specific Coefficient of Lift/ AOA. I'm going to make another video on this and the controversies commented in on this video.
@@FlyWirescottperdue I agree 100% about it being attained at a specific Coefficient of Lift and AOA. That's why it varies with weight. With CL the same, the speed required to lift the weight varies as a function of the square root of the airspeed, per the lift formula. I think we're on the same page here, just putting it slightly differently depending on what we are emphasizing.
I’d recommend changing the title to show your skepticism in the title. Simple add “ - I’m skeptical.”
Nice being so skeptical and really nice calling out Speed as proxy for AOA! Also nice implicit in this noting best glide is an AOA not a speed. Nice also highlighting that we trim for AOA not speed! I’d think even before anyone thinking this nonsense should have been skeptical based on the fact we have concern with trim stall (even if these be with power on) and fear of runaway trim. Were this true, we shouldn’t fear runaway trim, yet we do. But warning, folks may associate you with this stupid idea based on the title and failure to actually fully watch the episode.
I’ve never heard autopilot as part of the recommendation.
The recommendation is stupid on itself though he was saying the autopilot has a safety feature in his plane automatically engaging to recover from stall. So his is toggling this feature on and off. Were it off, he’d stall and the airframe would hold aft stick keeping the stall or possibly “falling leaf” with repetitive full stall to nose drop back to stall.
Bad idea. Very Bad idea. Even in a Cessna where it will might kinda work for center CG---not with someone in the back seat.
When you need Best Glide you need it ASAP.
So quickly that you get "light in the seat" from the push forward.
Trimming takes precious time away from other things you need to do to meet the 7700.
That’s all I needed to see. 105 it is!
I would never recommend this, as you say, this is a huge distraction from flying the aircraft to the point of touchdown. Try this in a Pa38, it would be a very brief experiment.
"If you have an engine failure just stay level, SLOW DOWN, and then trim full nose up."
What?
How is this even a thing?
Good question!
What I LOVE about your channel! There is ALWAYS something new I'm learning! Great demo! Thx!
Looks like a fast way to lose precious altitude that might help you glide to a safe spot. Why not use minimum sink airspeed? Minimum sink can be easily found by experiment
Seems BS to me without even trying it. Just know your speeds and learn to hand-fly is my advice! Too much autopilot out there; not enough PILOT!
"Weir dass fugoid" . Would love to see that plotted on a graph. It would look like the waves that make you puke on a ship.
Works great in a Cessna T206H. Not even close in a Cessna 150.
I would turn off the ESP protection and try again in smooth air. I have the same GFC500 with ESP. It is messing with your experiment.
Yes, I know... I was trying to point that out.
I've got an idea.
The "book" gives us a best glide speed for our aircraft.
Why don't we fly THAT speed and trim to ease control forces?
Then the aircraft WILL fly at the correct speed to maximise our glide!
We can then concentrate on selecting a landing site!
It is SO easy, it can't be that simple.
Can it?
As a retired 70 year old flight instructor with 45 years flying experience, I am gobsmacked that anyone would second guess the engineers who designed the aircraft and attempt to re-invent the basic priciples of flight.
America is averaging 30 fatal accidents a month!
I wonder why?
PS: Scott, I am not having a "Go" at you. I am amazed that others come up with these "Crack Pot" theories that you have to de-bunk!
I’m with you Charles!
I taught FLY the aircraft, try to resolve the problem, find a place to land and MAINTAIN CONTROL OF THE AIRCRAFT until touch down no matter what.
Sounds like a good plan!
Just because your Cessna 172 glide at best glide speed when the trim is full aft, is that any reason why a Beech or a Piper of any model will do the same ? Do you also believe in the tooth fairy ? Are you willing to stake your life on your opinion ?
The only way to be certain that all airplanes meet this "best glide with full aft trim" theory would be if it was a requirememt of the FAA Certification standards. And even then I wouldn't bet my life on it.
As a long time Aero Engineer who has spent his life working with stability and control characteristics, I can assure you that not all airplanes will tolerate this Full Aft Trim treatment.
And as a long time CFI I can assure you that your best bet when faced with an engine out emergency is to control the airplane using your well established normal handling and procedural methods. Nothing beats doing what you usually do.
Excellent comment
Aft CG would be way worse.
Indeed it would!
I was taught a trick in a Socata TB-10. From normal cruise to power-off best glide (86 kts in that model; and under the 'usual' conditions) move the trim two handfuls in the nose-up direction. I was surprised how accurate that is. So, I am tempted to believe in the trim trick, I just don't know why the trim setting would happen to coincide with the trim stop.
Scott, thank you for (again) taking the time to demonstrate these things hands-on; even 'simple' aerodynamics makes for intriguing content.
You bet Robert. I believe it’s all about wing loading and Trim / CG range.
That technique would work great in my 185 if the goal was to dig a big smoking hole in the ground.
Using mostly trim to fly the airplane is "The Lazy Man's Way". And in an emergency, lazy people fail a lot. They are not used to the hard work of "Emergency Maneuvering" , specially the hardest one, The EMERGENCY LOW MANEUVERING (Emergency Maneuvers when under TPA altitude). ELM Its a different kind of flying, (Altogether!).
Is it really that hard to remember a glide speed!
As you said, it depends on the airplane
When I was doing my training flying a 172, you’re exactly right. It would work in that aircraft. Also in steep turns, I could roll to 45 bank, put in 3 down spins of tim and could do a hands off steep turn in smooth air. When I got my first Cirrus I remember trying it, it was more stable than this, but it also didn’t have envelope protection. Regardless it still didn’t work. It does beg the question is there a different trim position that may work for different airplanes. It may a worthy experiment to see if there is a trim value that will get you to power off best glide and find some way to mark it. In the cirrus, the trim indicator is on the side stick so that would be easy. Would be tougher with a wheel. Just a thought.
There is a trim setting that will work and I think the best way to set it is to fly to best glide and trim it off!
That trim should change with load and cg loading . Interesting video as usual Scott .
Thanks for doing this. You have debunked it. I fly a Piper Dakota and I would rather trim for 85 knots and find a place to land!
Hi Scott, I’ve no input about the full trim up idea for best glide. Why is the autopilot involved in the test at all? The little F33/A36 time that I have proved them to be so stable that trimming for an airspeed and it just stayed there. No comment on trimming for a stall of course. Thanks
Ted you need to see my next video ‘What’s Up with. East Glide Anyway?’
@@FlyWirescottperdue will do! Your work is much appreciated!
So we're talking about an engine out scenario. First, we're trying to stay alive and unhurt. There's enough pressure in that situation that flirting with a stall and coincident altitude loss is something that you really don't want to get involved with. Fixing the best glide speed in your mind as an airspeed target to aviod unnecessary attitude loss, and stabilizing flight at the point would seem to to be your best initial course of action: fly the airplane, and avoid turning an engine out situation into a spin/stall accident. There's going to be enough to do finding a suitable forced landing field, and setting up the approach that one doesn't need a constant series of near stall recoveries, along with the loss of focus required to remain in a coordinated flight attitude near stall speed, to interfere with a critical navigation task. Once you're settled on the endgame, extending your glide (if necessary) can be a higher priority.
Vern, very close... the best protocol to me seems to be establish best glide, trim for that, look for a place to land, turn towards that, once you have the field/location made, transition to Min Sink... time is what you want and not distance (which implies you have to practice this beforehand to know what MinSink is). then maneuver to land.
@@FlyWirescottperdue Agreed. Most people are going to be rattled throughout this. Training is key, and then prioritizing critical tasks. Per your recent videos on stall/spin, keeping a comfortable margin on stalling the aircraft is insurance while your attention is elsewhere. Good stuff Scott!
yet another beauty of the C172 and C182, works on those, my instructor told me about that little trick. Informative video though, obviously doesn't work for everyone.
I read about this many years ago, and the idea of it wasnt to necessarily obtain best glide, but to give max distance while a landing solution was being explored, in light of the conditions. If I recall, when a bunch of engine out accidents were examined, distances were far shorter than max glide could provide, which implied the pilots get task saturated and lose a lot of altitude more quickly. This technique was promoted to be simplified, so that the pilot could focus on landing solutions and working problems while not all out squandering his altitude. I'm not sure allowing the auto pilot to manage an engine out scenario retains accuracy, am I missing something here? The technique was described as if engine out, pitch for best glide and slowly dial in trim incrementally until its was full nose high trim. Is it not possible that the method in which you incorporate it could have a significant effect here?
Yeah. The autopilot was NOT on.
🛫📖🛬
Hey Scott,
I can remember having this "Phugoid Oscillation" theory back in the fifties and sixties.
Truth is, when the emergency occurs, and you're fully Dead Stick, the weight along the datum makes it an entirely different scenario.
Hope you enjoyed Merry old England.
I did thanks!
I had about 10k hours in 172, Cutlass and Skylanes before someone showed me the trick of full nose up trim giving +/- 2 kts of Vld. It has worked on every 172/182 I’ve tried it in. None of these were high wing loading or laminar flow wings
@@daysix628 You're going to get someone killed with this horse manure.
@@dcxplant The technique is in several POHs. This works on dynamically stable aircraft. Now if you have an aft CG, and you did not practice this technique, all bets are off.
Hummm…..
I think that would be dangerous in a go-around scenario, glad you demonstrated it, may have saved a life!!!
I was taught this in a DA40 and it did work for that airplane. However, you advice is great - always test in your plane!
Thanks for the video!
We assume you disable the ESP feature during acro flight?!
Indeed, watch the next video "What the Heck is Best Glide Anyway" and I explain more about this.
@@FlyWirescottperdue Thank you for the response. We have a Debonair with the GFC500, We do a lot of air work and currently have the ESP disabled. We like the features of the autopilot, But, there have been times when it would like to control the aircraft in landing. Have you had any of these issues?
Hi Scott, did you develop a flight checklist for the GFC500?
Slowly reduce power, slowly trim nose up to the trim stop, when in smooth air flying a TR-2, Cheetah, Tiger, Archer, C-150/152, C-172, this method produces a stable descent that was close to best glide. I did this with various weight values as well but always within CG limits. Could be a possible solution to getting down through a smooth air overcast or IMC condition. I demonstrated this technic to Private, Commercial, Instrument, and CFI students to demonstrate the stability nature built into the aircraft design. I would never recommend it as an absolute solution to achieving best glide. Thanks for the demo in your bird👍🏼
Top tip.
Get the POH out
Mark the best glide speed with triangle 🔺️ tape marker on ASI
SIMPLES !!!
It must depend on the trim authority. Hands off, the trim always gives a certain speed. With full NU trim the 152 flies too fast, the Bonanza too slow. I suspect that there are aircraft out there where it works but simply by chance, not design. It is certainly not a universal answer.
It makes me wonder why manufacturers give you enough nose up trim to put the airspeed below the stalling speed. What possible value is there in allowing you to trim your aircraft to 40 knots?
This may also be "The Net"? But I'll trust Scott/Juan/Dan- not the rest.
You lost me at Dan.
What I'd be interested to see, is if trimmed correctly to best glide speed, and that trim position marked, how much variance there is with different wing loadings & CoG. In other words, can one trim position serve as a default "best glide" trim setting?
And to extend on that, is there any phase of flight (steep climb etc) that justifies more nose up trim, or could a default "best glide" trim setting also be calibrated as max available up trim?
Insufficient for the Saratoga TC I fly. Full trim up gives about 93 kts IAS but Vg is 83 for max cert weight. Prop full forward in my scenario. Just my tuppence
That seems difficult to believe, so your saying you can't trim your Saratoga to fly at 80 knots or 70 knots? What speed do you trim for on final?
@@utah20gflyer76 80 kts or slightly less for less than max cert weight for short final
Greetings from Cape Town. I certainly wound not want to be “wallowing “ around the stall near the ground in any aircraft. Rather have the aircraft at a decent speed to allow enough energy to configure and flare for the forced landing, so that the rate of descent is under control at touchdown.
Thanks for watching from SA!
G'day Scott,
Yay Team !
The Rumour-mongers who hatched the idea of trying to default to setting the Elevator Trim at Full Nose-Up, and then relying on Decalage to stabilise the Airframe in a "Best Glide"..., in my opinion have perhaps confused the meaning of
"Best Glide Speed" with that of
"Gliding as Slowly As Possible"...;
because while an Aircraft's "Best Glide Speed" is that which minimises the Sink-Rate..., and thus maximises both the possible Duration and the Ground Distance covered - while gliding down from the remaining available Altitude...; there may be times when the "Best" Speed at which to glide would be as close to Stalling as possible while retaining full control in all 3 Axes... (I've read of such advice, in cases of attempting to survive being forced to descend at night, and/or through IMC, when unsure of one's Position and/or the underlying Topography of the Landscape...., the idea being to encounter Planet Earth as slowly as possible while strapped in tight and flying right side up...).
But, yeah, in terms as you defined the Experiment, well done mate ; Myth Busted..., and the Hangar-Flying Breeze-Shooters will just(ifiably ?) have to recalibrate their colourful speculations...(!).
Such is life,
Have a good one...
Stay safe.
;-p
Ciao !
If it doesn't work as a blanket solution then ... it doesn't work. The whole point of the thing was to not have to remember something specific and apply a blanket process that should work "well enough" in almost any situation. This aint that! If you have to check if it works in a particular aircraft then you have to remember that and remember which aircraft you're in and at that point it's just as easy to remember the damn best glide airspeed. Also in an engine out situation I was taught to trim for minimum sink. This maximizes your time to find a suitable landing solution. Once that's done, THEN trim for best glide to arrive over said landing solution. Thank you for the testing!
Flying best glide is pretty easy ime. Pitch manually for best glide, then trim as necessary.
Scott what is the big box in the back where the seats would go? Is it an aux fuel tank if so how much extra fuel? Thanks John Ocala Fl
I don’t fly with the back seats installed. Can’t fly aerobatics with them. The airplane has the small baggage compartment and that box just covers up the back end.
I put the trim on my Cessna 180 nose up all the way and my best glide was 78 MPH. It works on the 180.
Was your autopilot yanking on the yoke for you in that wagon or were you the pic?! Haha!
It’s a lot of ratcheting full nose up huh?
In the Cessnas I’ve flown best glide gives max distance but the trim trick gives the most time. Just be quick on the trim when you advance the power.
Wouldn't you need to try that with the autopilot off?
The autopilot was off. It is a Garmin
@@FlyWirescottperdue I'm having my avionics redone in December. I didn't want to lose summer flying to have it done. I guess I'm going to have to learn about this autopilot because it's going into my plane. So even when it's off it will try to prevent stalling? Wouldn't there be drawbacks to this? I hope there's a way to completely turn it off so it doesn't do anything if that's my choice. Don't want a Boeing MCAS like event in my airplane.
@@frankrosenbloom Yes and Yes. I put a switch in to turn the power off. You can inhibit ESP by press/hold for 3" the AP Disconnect switch.
I did something similar in my experimental Zenith this week. I had read that if you trim it for level flight it will maintain best glide and it worked well for me. My best glide is 70 mph and it was around 72-73 with the engine at idle.
Scott, I have been doing the phugoid demo for decades as an introduction to stalls and glides. Your autopilot is obviously the culprit. Bonanza and other AC afms in the older GA advise to trim up and to keep the ball centered while keeping your hands off the CW during inadvertantly flight into IMC if you do are not IFR rated. . You can stand your Bone almost in it's tail from a trimmed state for whatever speed ( VA in this example) and the bird will recover to it's s trimmed glide if the AC is dynamically stable. We even did this demo in a test card on the BE-350. I still do this stability demo to this day. Works in Barons, 310s, (neeTwin Otters, Shorts 330/360s, F-27s...).
Sam, thanks for commenting. Indeed, in the video I pointed out that ESP was the source of the Phugoid. More importantly, the speed that this was happening was 30 knots below Best Glide Speed. The Trim technique does not work in this airplane.
@@FlyWirescottperdue Sorry to hear that the trim technique won't work in your bird, Scott. The A-36 that I checked pilots out in for the company did nicely, while a customer's A-35 was a wobbly goblin. The fun part in checking out the new kids on the block was during the emergency gear extension. They would struggle with controlling the A-36, and I would bring up the point that they had an autopilot onboard. D'Oh!! Talk about a phugoid demo.
That technique works great in a Cessna 150…practiced it many times…!!!
If I remember correctly my Grumman Tiger I was able to do that and it worked. Thanks for doing the test I fly a V-tail now.
This technique (full nose up trim) defenetly work at 172. I tried it personally with my CFI. However later we continue training with Cherokee and didn't use this technique. May be it works only for 172...
Hi Scott! Been a fan of your channel for a long while now! I recall reading this idea in AOPA Pilot a long time ago, it might have been Barry Schiff. I recall the idea was if you were NOT interested best glide. If you're engine dies when your over an airport, you're not interested in covering the maximum distance anymore. In that case, going slower than best glide will give you a lower descent rate and give you a little more time. It's not a huge difference, but rolling full nose trim up eventually will get you there and above stall speed, since manufacturers generally won't buld a trim system that will stall under typical conditions. There wasn't any talk about autopilots
Thanks Jay. I did not have the autopilot on. It is a GFC500 and ESP was activating. The point is that full up trim was too slow for best glide.
@@FlyWirescottperdue Yeah, I'm not sure how people got the idea that it would get you close to best glide, but I have to imagine that article was the source of that idea. I'll try to see if I can remember where I found it!
@@jaywung7616 I believe the confusión was between immediate actions after engine failure, and subsequent ones . Slowest rate of vertical descent will better enable the pilot to contact ATC straight away with ID , position , and predicament by staying higher longer . After that , field selection, attaining Vbg ( if necessary ) and finally , attempted diagnosis.
The trim wheel deal allows time for the pilot to collect their thoughts before formally setting up for a landing and trying, meanwhile ,for a restart .
Jay, you are correct. Barry Schiff wrote about this many years ago in AOPA Pilot. The full nose up trim was not for best glide, but for remaining aloft for the maximum amount of time. Best use is for when one was already over a field and wanted extra time to deal with the issues.
id like to see it w the gfc500 etc w esp disabled, so it stops taking over, so u can hand fly it...I'm w you, would rather stick w the poh on best glide...good video thanks!
The GFC500, in most installations, is hard to turn off and inhibiting ESP is a temporary thing. I installed a switch to turn it off and it glides just fine under manual control. None of that matters.... the trim technique tested was over 30 knots BELOW Best Glide speed. The technique did not work. There are LOTS of videos in this airplane without the GFC500 on, most actually.
Pretty sure the full trim up was only for Cessna 172's
Where this trim thing comes from is two-fold: thrust causing pitch reaction, and aerodynamic where propwash passes over the wings/tail. With a dead engine, you lose these effects that you had with power, and this changes the trim condition (slightly). Trim for speed with power, then pull power, pitch for speed, and see if your trim moves to maintain a stable flight path. Same thing happens with jet aircraft, especially where the engines are mounted off the centerline (e.g. underslung engines).
Pitch for speed, stabilize it with elevator, THEN trim the aircraft.
With US certified aircraft and if the aircraft is in proper rig, trimming the aircraft at full nose up at idle power is supposed to be as slow as the aircraft can fly in a standard rate turn without stalling. Beware I've found in my travels that many aircraft aren't in proper rig specifications. When I bought my recent aircraft, the idle power was adjusted at 375 RPM. The specification is 600 RPM. The trim was adjusted for strait level flight and not much room for a shallow turn. Comprehending how each aircraft is rigged is a paramount key. Many aircraft aren't certified for intentional spins, so this is very important to know the warning signs of an eminent stall/spin scenario when verifying an aircraft is in proper trim rig. Once I verify the aircraft, I'm aviating with is in proper trim when I make the landing the trim is normally in full nose up position as I cross the inner marker on final approach. This facilitates muscle memory to push on the stick to keep airspeed up in gusty and crosswind landing conditions. Practicing slow flight with the trim in full nose up and being aware of how much power is required to set assent and decent rates or just staying at altitude was flight school 101 back when I was learning in 1966. Remember the word if!
Will, that is a technique for a particular airplane. Not a blanket application.
Would think every aircraft by the manufacture would have directives regarding how 'best glide speed / distance' is achieved in engine out circumstance (sh*t happens principal)? Would seem only logical that low wing aircraft would need a different trim setting than high wing aircraft in un-powered situations.
What is different about aerodynamics for a high wing versus a low wing?
Yes, it works with C172G. Just trim slowly as your speed bleeds down.
The "full-trim-up" hack that was purported to generally work, clearly only works for specific small GA planes, not "in general" as what was suggested by those videos.
The idea behind the hack was to "set and forget" so you could concentrate on finding a place to land without worrying too much about speed management. The truth is, the notion is a complete fallacy because you still end up watching your speed anyway.
In fact, with full-trim-up, your plane is no longer in it's clean configuration, and you lose some maneuverability. And if you end up in a stall (i.e., you encounter a wind gust/shear or turbulence), full-trim-up *will* (not 'may') induce a spin, unless you immediately counter.
To me, the hack is not a viable option. Instead, I have that speed marked on my airspeed gauge (using a colored sticky arrow), and it is committed to memory.
@@hack1n8r Excellent comment Jackal!
very intersting!! thanks..
What a coincidence. "Weird-ass Fugoid" was the name of my band.
Was kind of hard to hear you when you started the practice and stayed hard to hear till about the 7 min mark. So fyi.
In my Mooney trim for best glide is right in the middle of the trim range so no need for me to even try this out. I had actually heard people say trim full back, full flaps and gear down for inadvertent IMC and spatial disorientation, the thought was you have a low probability of over speeding the airframe in that configuration, but I don't know if that's a good idea or not.
With my flight instructor, we tested full trim up in a Taylorcraft. We held it level until on the verge of a stall (33 knots). Cut the power and released the yoke. The oscillations slowed and airspeed stabilized around 41 knots. The aircraft never stalled. I’m wondering if DMMS could be used for best glide speed in a pinch? It may not get the absolute best glide performance but probably will get you close.
Measure with a micrometer and cut it with an Axe.
My POH lists the best glide speed as 80 mph and the glide ratio as 12:1. To test this I took my plane to 1 mile AGL on a calm wind day and idled the throttle, expecting that at 80 mph the plane would travel 12 miles. Instead it travelled less than 6 miles. The take home message is that your POH values may be misleading. I'm going to repeat the test at different glide speeds to see if performance improves.
Excellent plan! And a very good observation.
You must be flying a sailplane to get a 12 to 1 glide ratio. Most airplanes range between 4:1 and 7:1 in real world conditions.
@@pittss2c601 My Operation Manual states "The glide ratio of the Navion is approximately 12 to 1 at an airspeed of 80 mph". In fact my Navion A with the E-185 engine is roughly the same size and weight as a notoriously poor glider of the same vintage, the v-tail Bonanza. The Navion seems to glide a little better than the v-tail, the stall speeds are lower, but the 12:1 claim has got to be a fish story.
@@RaysDad With a gross weight of approximately 2,800 lb, 184 square feet of wing area and approximately 15 lb per square foot, that would place it around 6:1 or maybe 7:1 glide ratio. My ground school instructor always told us the manual lies. Don't trust the manual.
@@pittss2c601 Interesting. I've never learned to calculate glide ratio but certainly the engineers who designed my plane and wrote the POH knew it, and they flight tested the aircraft, and still they decided to claim 12:1.
Hi Scott - been a little while. Hope you're doin ok. Your audio sounded a little funny at some points.
Hang in there. Take care.
Honestly, remembering glide speed or finding it quickly in poh is much easier 😂
Yeah.. um.. not for THIS aircraft! D'oh!
Does the answer not lie in the airworthiness certification requirements of the design? How much trim "authority" needs to be available? I would imagine that by design, you should not be able to trim the aircraft below the stall in stable flight? At what weight and CG would this be true, maximum or minimum, most forward or most aft? At the other end of the scale, how much nose down trim authority is designed into a light aircraft. Again, common sense would dictate that you should not be able to trim it past its maximum speed. But which speed, Red Line, top of the green arc? Look what you've done Scott, it was a perfect morning until you posted this excellent video. I was fat, dumb and happy, now I have a thousand questions floating around in my head. Greetings from Dubai, UAE.
Glad you have questions!!! The weight/ CG and speed capabilities of the airplane dictate the trim range of the design. I suspect that in this particular airplane full nose up trim would result in a speed just above stall. Full nose down on the other hand would likely be above Vne. I'd be happy to test the former and reluctant to test the latter.
Trim to Best glide.....and RIDE Thanks interesting.
Give me that "good ole tried & true" best glide speed always!!!!!!!!!
Wow, one would want to make sure their wing stall vent is clear? That's for sure and also a nickel on the grass.
🌏🛩️
I think flying the airplane in an engine out and feeling what it’s doing is more important than trying to screw with trim and porpoising all over the place while the ground is coming up.
Funny. I’ve never had autopilot when I lost an engine. Just saying.....
The autopilot was not engaged. It is a GFC 500 and the ESP floor was activated.
I like your dual cue FD. My preference over the single cue.
I am thinking nose high with no/low power is too close to a stall/spin. you are saved by your auto-pilot. in a plane without that I think you would be looking at a dangerous stall-spin scenario. Fly the plane, keep your 105 knots best glide, and keep your altitude as best you can in a low/no power emergency. My two cents only.
Good point!
I wonder how the results will vary with the prop at full coarse position?
I’ve done videos on that. In the Bonanza it reduces descent rate by 6-700 fpm.
I think this myth conflates best glide and minimum sink? Full nose up trim in a Tri-Pacer will get you about min-sink, but that is fat wing with lots of drag at high AoA. W&B will impact what speed you get. Going to go try it in my Mooney, though. I also think you have to intervene to stop the pitch phugoid.
It was closer to Min Sink, but below it.
Looks like a way to vomit all over the place.
There was no way this would work.
That’s our SOP for engine out emergency I’m the caravan.
in*
Great video thanks Scott. I'm a bit worried about the technique in that at some point during your glide after engine out, you will have to turn to line up for a landing. Correct me if I'm wrong we wouldn't want to be much lower than DMMS to stay out of trouble. I'd rather do as my instructor taught and set up a constant best glide speed by pushing forward a little and then adjusting the trim for best glide. The DMMS won't be far from this speed.
Not knowing your airplane I would say that might not be true. In fact I would go as far to say that the Dmms speed is probably closer to min-sink than to Best Glide. Best Glide is for distance, min-sink is for time.
@@FlyWirescottperdue Thanks Scott. It had certainly made me think outside the box.
as far as you explaining in video. i could not hear half of it. your volume went way low
Dude the parts where the volume was low were just repeats when it was loud… using a different camera.
How about turning off the autopilot?
I don’t trust these internet fixes in general; maybe it works on the Cessna 152 though.
Good question. In my airplane I installed an on/off switch because I go upside down a fair amount. It is possible to disable it, but that is an addition to work load not a subtraction.
Jeez people....its one number to remember! 🤣