Forget Best Glide Speed- Just Trim Full Nose Up!
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- čas přidán 7. 09. 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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I knew that wouldn’t work! 😂 Just placard the best glide speed on the panel!
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.
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.
That’s all I needed to see. 105 it is!
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 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.
What I LOVE about your channel! There is ALWAYS something new I'm learning! Great demo! Thx!
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
I was taught this in a DA40 and it did work for that airplane. However, you advice is great - always test in your plane!
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 .
Great vid! I think you are correct. No AP might produce acceptable results for us puddle hopper 172 pilots.
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.
I love how you did this at FL 4K .....wicked smart!
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.
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.
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?
🛫📖🛬
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.
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.
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.
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👍🏼
My instructor taught me this option for engine out procedures on a 172. In a Cessna, I agree that it's more useful it will maintain speed at 65. My instructor rationale behind this option is that it frees up your hands in maintaining best glide speed. And focus more on ABC and comms. During my check ride, I used full nose up trim and worked great. One thing you have to remember, it goes without saying, once you initiate the go around procedure (during training or check ride) once on full power settings don't forget to trim nose down immediately. Great video!
Don’t think 65 is Best Glide in a 172.
@@FlyWirescottperdue you’re right. Best is 69 adjusted from MPH to knots on M model.
@@Victordamus98 69 or 68 only for full gross weight, if only 2 passengers it’ll be close to 65
@@hordi1ful makes perfect sense. Thanks!
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.
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!
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’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.
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
"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.
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.
This may also be "The Net"? But I'll trust Scott/Juan/Dan- not the rest.
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!
Better to trim to best glide (that way you know you've nailed it), while looking for a landing site.
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!
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!
It works like a charm on a cessna 172. I used it every time my instructor pulled the power and said your engine just died. I rolled in full nose up trim and it showed the best glide at 65kts. I've told a few people about it with the disclaimer about it works on a 172 but have no experience trying it in any other aircraft.
Exactly. It works on a C172. Don't rely on it in other planes unless you have personally checked it out.
That technique works great in a Cessna 150…practiced it many times…!!!
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
Great job....I don't think that would work on my aircraft either.
As you said, it depends on the airplane
All Cessna single engine aircraft have the Full Trim Up feature built in. It works in 150, 152, 172, 182, 206 and 210. Trust me. Part of Emergency Procedure training is to get the pilot to trust using this procedure with an engine out situation.
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!
I like your dual cue FD. My preference over the single cue.
Thanks for the demonstration. When I read the title, I thought "this is nuts." And it is. The POH is gives you the best L/D for a reference weight. It's going to shift with a change in load - sqrt(ps/ps'). Hard to calculate in the air. A proxy we use in gliders for the best L/D (it's approximate) is 1.3 times the stall speed at a give weight and configuration. Try that one out in you Bonanza maybe. I'd be curious to know, if it also works in powered aircraft.
1.3Vs would NOT be Best Glide in the Bonanza
@@FlyWirescottperdue My mistake... Yeah, you said 56 kts was close to your stall. Earlier I thought you said 105 kts was about your best L/D. Watching your video, I hear the stall warning kicking off at around 80 kts.
Works great in a Cessna T206H. Not even close in a Cessna 150.
Hummm…..
I think that would be dangerous in a go-around scenario, glad you demonstrated it, may have saved a life!!!
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...
Top tip.
Get the POH out
Mark the best glide speed with triangle 🔺️ tape marker on ASI
SIMPLES !!!
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.
That technique would work great in my 185 if the goal was to dig a big smoking hole in the ground.
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.
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!
"If you have an engine failure just stay level, SLOW DOWN, and then trim full nose up."
What?
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!).
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.
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.
very intersting!! thanks..
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?
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.
Flying best glide is pretty easy ime. Pitch manually for best glide, then trim as necessary.
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!
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?
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.
Hi Scott, I did read that article about back trim and haven’t tried it myself yet, but I’m not surprised with the result. It looks like you have the AP engaged in ALT hold mode. In this setting, the AP is doing what it was asked to do, but what was beyond what the airplane can do. The AP is trying to hold altitude, the airplane is losing speed and altitude due to insufficient power, and then it enters phugoid oscillations as a result of ESP and ALT hold mode commanding corrective actions. I think the are two ways to prove or bust this myth:
1) Try it out without the AP and accept the inevitable altitude loss.
2) Engage the AP in PIT mode when holding the pitch for level flight; this way it won’t keep pitching up to hold altitude.
I’m sure you know all this, curious if there was a reason to use ALT hold mode?
PS: Glad to see your Bo flying again with new engine!
Christoph, Thanks for watching. I said in the Vida I started with the autopilot engaged, disconnected it after failing the engine and began trimming manually. The Trim technique failed at finding Best Glide of 105 knots. It required the airplane to fly at a lower speed than the activation speed for the Garmin GFC500 ESP system which always operates in the background. I mentioned that a bunch of times in the video. Eventually, the ESP system activated the autopilot to fly Level. At that point I terminated the exercise. Thanks for you advice, but I suggest you watch the video again.
You’re right. I missed the part when you say you’re disconnecting the AP (plus the display shows that while the FD is in HDG/ALT mode, the AP was indeed disengaged just before the ESP kicked in). One thing I’d be curious about (which doesn’t change the conclusion of the experiment) - how did you manage to keep the trim all the way back throughout the test? I ask because once the ESP engaged, the AP must have lowered the nose using the trim, so the trim was no longer fully aft after that, and presumably kept getting moved to a more neutral position (unless you kept re-trimming).
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!
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
Nose to the sky, you won't die!
Wow, one would want to make sure their wing stall vent is clear? That's for sure and also a nickel on the grass.
🌏🛩️
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.
Jeez people....its one number to remember! 🤣
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.
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.
What a coincidence. "Weird-ass Fugoid" was the name of my band.
I'll try it in a DA40. See if it makes a good parachute. Doubt it. Expect a wing to drop.
How is this even a thing?
Good question!
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.
Give me that "good ole tried & true" best glide speed always!!!!!!!!!
Descending at that rate is a no go.
Very interesting
For the next one why not see if engine to idle, full flaps, full nose up trim and hands / feet off gets to a benign spiral?
Not in the Bonanza. Spiral Divergence is an issue and part of any good checkout program. It will tighten up into a steepening bank and rapidly increasing airspeed.
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?
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!
Honestly, remembering glide speed or finding it quickly in poh is much easier 😂
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.
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 !
You could try it with the autopilot off. The full nose up trim works for my Cherokee. But, as you say, this old advice can not apply to all aircraft. It might be a good idea to find which trim setting achieves minimum maneuvering speed.
Thanks Malcolm. The autopilot WAS off. It is a Garmin GFC500 and it has ESP, I talked about in the video.
I know this applies for the 172N. After an engine out you can slowly wind the trim up while running checks and it will settle on 60ish. Even if you do it too fast, she will pitch up then settle without input. In a high work load situation it's really handy.
But that’s not Best Glide speed.
That's not best glide, a 172 I fly is just over 80 with full nose up trim. That isn't best glide speed either. Adding or removing weight/passengers will change it too.
@@FlyWirescottperdue Not far off it. 60 to 65 spans lowest sink rate and best glide... I'll never forget those numbers in the N models lol.
You are such a treasure man, your incredible knowledge, wonderful moral compass, and inquisitive nature make you such an asset to the flying community.
I’d put the trim at the takeoff position (if I can trust it) or I’d trim for 1.4x the bottom of the green arc. If you stall, you fall..
In my Mooney takeoff trim IS best glide trim. Right in the middle of the trim range.
The best rate of climb speed in a Cherokee Arrow II is 95 mph. The clean stall speed is 70 and 70 x 1.4 is 98 mph. In the owner's handbook, the Glide Distance vs Altitude chart uses 105 mph. Trying to guide near the stall speed is foolish, but apparently, some people think slower is better when the engine quits.
And it most decidedly is not!
Trim in takeoff position in the F33C is neutral.
@@FlyWirescottperdue Does neutral have a stable glide speed/rate of descent?
My guess is that the theory is without an AP turned on trim for full nose up. Obviously, the autopilot is overriding the trim. Try it again with the AP turned off and full up trim. I have no idea if it will work, but I think it will test their theory. Of course it will not work in our model Huskies, because we are not trimming the tail, we are trimming the stick with a bungee. Thank you.
Jim, The Autopilot was NOT ON. I explained that the GFC500 was hitting the ESP floor and eventually with the phugoid it tried to level the airplane and activated itself at which time I terminated the exercise. And indeed you are correct about Huskies!
As they say, just fly the numbers.
Will this work on my RC airplane when i fry the 8th brushless bang good motor this month?
Is it really that hard to remember a glide speed!
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 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.
I think I read a similar article and it said to trim for level flight and that was usually full up trim. Did you try just trimming for 0 degrees of pitch?
0 degrees of pitch is NOT Full Nose up. I advocate setting 105 Knots in the Bonanza and THEN trimming the force off!
I've done it in Cessna 185s and 206s and if I remember it worked just fine. Never tried it with auto pilot on. I'll try it in my comanche. Thx.
My autopilot was not on. It is a GFC500 and that was ESP activating. The point is that full up trim is too slow for best glide.
@@FlyWirescottperdue it works in Cessnas Scott (172, 182, 206 etc..) one might argue that the Cessna engineers did a better job by setting maximum trim up to be best glide.
@@FlyWirescottperdue Got it thanks..good video.
one problem i see is that your autopilot is trying to do what you have asked it to do which is keep the plane level so no wonder you're porpoising... try it with the auto pilot off but obviously with your hands on the controls :D pull the power get to best glide and see how much trim you actually do need.
Daytona, you don’t understand the GFC500. I did disable it before the exercise and it always runs in the background… remember me talking about ESP? Normal installations don’t have kill switches. Regardless, the trim speed was WAY slower than Best Glide.
@@FlyWirescottperdue ahhh ok and you are correct, i don't understand the gfc500 (we have dynons in our planes). so i assume then there's no way to stop it automatically pulling up then i guess? i've not actually had any time using the autopilot in our sting yet as im only just starting the cross country stuff and i need to learn to do it WITHOUT the AP, but it's nice to know it's there and how to use it if i screw up :D or get lost :D
You can temporarily disable ESP from the PFD
Scott. Are you piloting the new Mythbuster series? I learned that you shouldn’t believe everything you hear. Thanks for proving it.
Thanks, Jim. Maybe I need to do a few. I've heard some crazy stuff recently.
@@FlyWirescottperdue talk about pilot integrity. Cutting corners and other shortcuts that could hurt real bad.
I'm not sure that this was a really valid experiment because (a) it was complicated by the autopilot which kept taking over and (b) the engine wasn't really 'out' . But I don't think that it's a technique I'd use in an engine out situation anyway. I'd rather trust my own judgement and control.
So you think the engine out to be shit down? Do that video and I’ll watch
@@FlyWirescottperdue No, and I wouldn't even expect it to be shUt down either 😆. But seriously Scott, I've had an engine out and the last thing I would have done with my time was fiddle about with the aircraft trim. I knew roughly what my best glide speed was so manually controlled the aircraft for that while I searched for a safe place to put it down. After finding a large convenient field it was then just a matter of manually flying it the whole way into the 'crash' which was actually a successful safe landing with me fully controlling altitude and airspeed myself. OK every event is unique and the best tool is good training to judge what is best at that time, not advice found on the internet or, with respect, CZcams.
BTW I'm sure that you're aware that there are vids on CZcams of pilots doing full engine out practices from overhead their airfields so it's not that big a deal.
If it's on the Internet; it must be right
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.
Could you please explain why you had the autopilot engaged? Not to say that the technique would work in a Bonanza, but doesn't the use of an autopilot invalidate the whole test? Isn't the idea that the airplane itself will seek a stable condition on its own? How can it do that if every time it gets to a certain point in its cycle, the autopilot starts putting in control input? Perhaps I'm misunderstanding what you're trying to test.
Indeed, you missed what happened. I specifically disconnected the autopilot. Watch it again. The Garmin GFC500 has ESP and that is what was triggered by the trim technique.
@@FlyWirescottperdue Nope, caught it at 2:54. And then at 3:33, 3:44 and 4:00, I also caught your saying that the autopilot took over. ESP, autopilot proper, or even your own arms, once control input was applied, the test concluded, not by finding that the airspeed the plane settled on was not the best glide speed, but by its reaching a safety limit beyond which you did not want to go. While perfectly valid, this did not seem to be the premise you were trying to prove, nor the conclusion you reached.
What surprises me, then, considering the high degree of respect I have for you, is that I don’t recall your ever stating directly that there is a danger in using this technique, especially in aircraft such as your Bonanza, of the aircraft stalling and/or spinning, and that as such, this technique should be approached with caution more for this reason than that it simply may not trim to best glide speed.
Nevertheless, this video, as yours consistently do, remains informative and well worth watching. Thanks