Do You Pitch Up First For Best Glide?

Discussion in 'Pilot Training' started by Sinistar, Nov 19, 2017.

  1. Sinistar

    Sinistar Cleared for Takeoff

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    So, your cruising along at 145mph 3000agl on a nice SKC day and your engine quits. Your best glide is 80mph. Regarding best glide speed specifically, do you:

    A.) Hold altitude until slowing to best glide speed and then descend/trim?
    B.) Immediately pitch up until slowing to best glide speed and then descend/trim?

    This one is funny in that my wife and one instructor do it one way and a different instructor does it another way.
     
  2. AWACSEng

    AWACSEng Cleared for Takeoff

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    Im in the hold altitude and let the speed bleed off camp. The altitude gained vs speed lost in the pitch up maneuver is nominal, IMO. I'd rather use that energy in a turn towards my chosen landing site.
     
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  3. timwinters

    timwinters Ejection Handle Pulled PoA Supporter

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    In most properly rigged, single engine cessnas, including both that I've owned, if you roll the trim wheel back all the way to the stop, once it settles in, it'll be within a few knots of best glide.

    So that's what I do.

    What exactly does the airplane do while I'm doing this? I don't know.
     
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  4. AWACSEng

    AWACSEng Cleared for Takeoff

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    Tim, I also roll full nose up trim in an engine out scenario, but I counter that with forward pressure to maintain altitude and allow the speed to bleed naturally. I have found that if I don't do that, and allow the aircraft to react to the trim, the nose pitches up and the speed bleeds off faster than desired while I'm running through troubleshooting/checklists.
     
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  5. Ryanb

    Ryanb Final Approach PoA Supporter

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    I don’t really think either one of those make much of a difference, in all honesty. They both get you to Best Glide with minimal altitude lost, which is the main goal.
     
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  6. Sundancer

    Sundancer Pattern Altitude

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    Probably not a groat's worth of difference, and other things are gonna take precedence, I imagine. . .
     
  7. Capt. Geoffrey Thorpe

    Capt. Geoffrey Thorpe Touchdown! Greaser!

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    C) Pull carb heat and switch tanks.
     
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  8. Sinistar

    Sinistar Cleared for Takeoff

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    Yeah, the other steps of the emergency procedure were left out of this question - just trying to figure out with a sample size of (3) before even waking up the interweb, why the difference between pitching up for altitude vs holding level to preserve some speed. Now I could see if you were really, really low and going relatively fast I would thinking pitching up might really start to matter. But at 3000agl you've got over 3 minutes to work the problem (at least what I've figure for the 182).
     
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  9. midlifeflyer

    midlifeflyer Final Approach

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    Just two techniques.

    I prefer going to level (cruise) pitch while looking for a place to land and heading there. I think that gets me to best glide without having to divert my attention from other immediate tasks. I barely need to look at the airspeed indicator.

    I also think there's a downside to pitching up. You end up imprinting it as your first reaction to a power loss, which can kill you if the power loss occurs during climb out. I prefer my automatic reaction be level pitch, whether that means up or down.
     
  10. FastEddieB

    FastEddieB Final Approach

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    As others have said, probably not enough difference to worry about.

    But...

    I think the nod goes to staying level. Pulling up into a climb increases the induced drag as a result of the increased angle of attack. I would think that given identical planes under identical conditions, the one that climbed would come up just a tad shorter than the one that stayed level.

    Though a small difference, it could conceivably mean just making a field or coming up just a bit short.
     
  11. luvflyin

    luvflyin Final Approach

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    I don't put any effort into 'maintaining altitude.' I apply back pressure, trim and get to VG. How much it pitches up while doing that or how much altitude is gained, I haven't paid enough attention to to remember. Just want to get to VG, look for a place to land if I don't already know where that is and try to maybe get the engine running.
     
  12. Mtns2Skies

    Mtns2Skies Super Moderator Management Council Member

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    I'd actually argue the other side of that. Drag is exponentially increased with speed. Therefore the sooner you can bleed off that extra speed(i.e, re-purposing that energy into altitude), the less overall energy you are wasting.

    EDIT: The reality is though that the difference in cruise speed and best glide speed for most GA airplanes is so small that it really won't make much difference either way.
     
    Last edited: Nov 19, 2017
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  13. asicer

    asicer En-Route

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    Do whatever it takes to get the plane trimmed for Vg as quickly as possible so that I can spend maximum brain power on other tasks as soon as possible.
     
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  14. Palmpilot

    Palmpilot Touchdown! Greaser!

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    Because I was taught to establish best glide speed as the first item on my engine-failure procedure, I'm not imprinted to pitch in any particular direction. I'm imprinted to look at the airspeed and adjust in whichever direction is needed, which will depend on whether my airspeed is above or below best glide speed at the time.
     
  15. midlifeflyer

    midlifeflyer Final Approach

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    Whatever works works.

    My "level pitch" comment is based on an experience I had years ago watching someone else do the simulated power loss procedure. He looked out the window, went to level pitch, and, by the time the airplane settled at best glide, was well into his turn to a landing area.

    Since then, I’ve tried it in all of the 30 or so types of singles I’ve flown. Power off, moving to a level cruise pitch attitude results is a very accurate approximation of best glide. The ASI is a post-configuration confirmation for me, not an initial target. Works better for the way my mind works than looking at an ASI and deciding if I need to increase or decrease airspeed.

    I teach it to students and show it as part of flight reviews if I see the pilot spend way too much time "hunting" for best glide and waiting to achieve it before doing anything else (a loooong time in faster singles).
     
  16. pigpenracing

    pigpenracing Pattern Altitude

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    Do whatever works.
    When I lost the engine in my Christen Eagle I didn't think of anything I learned during training....
    I did what I needed to do to make a safe landing and not kill myself. It worked out perfect with a smooth landing on the runway.
    Every situation is different. If your at 10,000 feet and the plane is full of smoke I don't think you want to trim for best glide.
     
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  17. brcase

    brcase Cleared for Takeoff

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    I remember reading about the trim all the way up technique in AOPA Pilot more than 20 years ago. I have watched a few pilots try this technique and generally found that at some point during the approach we got scary slow. My normal landing are usually minimum flap (10 degrees) and near power off and usually hands off on the approach as I have the airplane trimmed for my normal approach speed. My Trim is almost never full back in this configuration. To be fair, usually until short approach I often carry up to an extra 5 kts (70kts in the 172N).

    Sounds like it is time for me to go try this technique again and remind myself about what kind of results I get. But unless you normally land with the trim all the way back I would NOT recommend trying it in a emergency landing. I really like the phrase, "Make your emergency as normal as possible" ie. do as little new or unusual stuff as possible during the emergency, stick with what you know. I usually recommend your restart procedure plus your normal landing checklist, unless the POH recommends something different. (Low Prop RPM for example)

    I teach the ABC (Airspeed, Best Landing Area, Cockpit) procedure, but explain Airspeed is a reminder to not screw it up, because to many pilots do. I also note that most experienced pilot use CBA. When the engine loses power they have the fuel tanks switched, fuel pump on and carb heat on as appropriate within about 2 seconds or less, they then select their landing area and then configure for landing.

    Now maybe someone that practices the trim all the way back procedure can suggest what I should do different to make the trim all the way back technique work better to get the 60-65kt recommended approach speed. if I get a chance to try it again this week I will report what I get.

    For the OP's question, when slowing down I prefer to maintain altitude.

    Brian
    CFIIG/ASEL
     
  18. FastEddieB

    FastEddieB Final Approach

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    Interesting counterpoint.

    Would be problematical to test in flight.

    Does anyone have a really accurate flight simulator? If so, it should not be too hard to try it both ways and note where ground contact occurs, then compare.
     
  19. mscard88

    mscard88 Touchdown! Greaser!

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    I'm with @midlifeflyer. Learn what the airplane attitude is when at best glide visually. Find a landing area, do your checks (fuel, fuel pump, carb etc). Knowing what the plane looks like at best glide gets you close to your speed and allows you more time to be spent maneuvering to the landing area and troubleshooting the cause.
     
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  20. luvflyin

    luvflyin Final Approach

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    I think I've tended to spend a little more time than necessary looking for VG sooner than necessary. I'm liking just pitch for the attitude that looks about right at first and then do next what seems like should be done next. That may be getting to VG right away or not depending on the situation. Good thread.
     
  21. midlifeflyer

    midlifeflyer Final Approach

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    Try it next time you go up for a practice session. Start with a pitch attitude you are already very familiar with - the one you use in cruise. You are likely to be pleasantly surprised.
     
  22. James331

    James331 Touchdown! Greaser!

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    Depends on where you're going to land the plane I guess.
     
  23. Capt. Geoffrey Thorpe

    Capt. Geoffrey Thorpe Touchdown! Greaser!

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    OK - just to be clear, according to the experts, I have an anti-authority attitude or something.

    But, the way I figure it, the most likely things to go wrong that can be fixed without getting out and taking off the cowl are fuel and carb ice. And, in my (admittedly somewhat limited) experience with engines that stop making noise, one or the other has fixed it. So, I grab heat and selector first (contrary to Gospel - Yes, I'm aware that I will go straight to aich eee double hocky sticks for saying this) and when the noise resumes all that best glide stuff is just not that important. And, if it doesn't, well I've lost, like, less than two seconds - which is probably about 10 feet of altitude - at worst. Further, if that 10 feet makes the difference between making a field or not - you dunn oughtta picked a closer spot.
     
  24. timwinters

    timwinters Ejection Handle Pulled PoA Supporter

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    Can't speak for any other birds except the two I've owned and flown. A 172 and 182, both straight tails so completely different (and far more nimble and docile) animals than later models, and I've never experienced this.

    The main thing it does for you is that it allows you to trim for best glide in about 2 seconds so you can immediately start dealing with other required tasks.
     
    Last edited: Nov 21, 2017
  25. dmspilot

    dmspilot En-Route

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    I have seen students do it but it wasn't because of excess trim at all. Manhandling the airplane caused it, regardless of trim position.
     
  26. nauga

    nauga Pattern Altitude

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    TL;DR: Tested with a simplified C172 model. Expected climb and decel to max range glide and descent at max range glide would give max range. I was wrong.o_O:D

    Yes, but they don't let me use it for 'POA research' :D

    I did do some simplified but fairly realistic (unvalidated but not far off at least one OpMan I found) modeling using a simple lift curve and drag polar of a C-172 based on data I found online (for what that's worth) and conservative weight and cruise speed. I won't go into the math here (available if anyone wants to see), but I looked at staying level and decelerating to max range glide speed (not Vbg, it was the speed for L/Dmax at current conditions) then staying at max range glide until 0 AGL. I also looked at 100, 200, and 500 fpm climbs (decelerating, of course) until max range glide speed was reached, then maintaining best glide to 0 AGL. Initial conditions were always 125 KTAS at 5K MSL.

    The results were all within a few 10s of feet of each other, but the level decel to best glide then down at best glide always went the farthest.
    I was expecting the climbs to be longer, but they were consistently shorter. The differences were small enough to indicate that the easiest to fly would probably give the best results rather than monkeying with climbs and pushes and stuff.

    I don't guarantee my results, and they may change with model or conditions (speed, altitude, L/Dmax, etc...), but it was an entertaining exercise.

    EDIT: Found one (possibly of several) error in my model that affected both methods. Updated in Post 43
    Nauga,
    who loves his AOA indicator
     
    Last edited: Nov 22, 2017
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  27. HornetDriver

    HornetDriver Filing Flight Plan

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    FWIW, in the T-6b the first step of the engine failure EP is to zoom climb to best glide.
     
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  28. Sinistar

    Sinistar Cleared for Takeoff

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    Hmm...and interesting. So it looks like (theoretically) and most likely realistically, in this scenario there would be very little difference in pitch up vs level flight to best glide and the final distance. I am guessing the best reason to pitch up is to gain altitude if it is really, really needed. For example, flying very low and enough speed where it would make a difference. That is not a aircraft type or typical flight condition I would be in. I could see this really mattering to airshow / stunt / air racing pilots I guess.
     
  29. Sinistar

    Sinistar Cleared for Takeoff

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    That's the first emergency procedure I have heard of which calls out a climb to best glide. It seems the POH's from GA aircraft use wording to the effect of "Establish best glide speed" but leave it open/generic as to how it should be specifically established.
     
  30. nauga

    nauga Pattern Altitude

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    I'm still suspicious of my results. I'll scrub my work and see if anything turns up. I really did expect a climb to yield better results so I need to understand what's wrong - whether it's my intuition or my math :cool:

    Nauga,
    who misses OTIS
     
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  31. Sinistar

    Sinistar Cleared for Takeoff

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    You would think in a weirdly-perfect scenario with zero drag friction, zero thrust, and a ideal decel to best glide: whether you pitched up and then back over or coast level and then over would be identical trajectories. Just trading more kinetic energy for potential energy in the first case. Or maybe its a preservation of momentum calculation.
     
  32. FastEddieB

    FastEddieB Final Approach

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    I still envision the pitch up, with its increased AOA, angling the lift vector back ever-so-slightly, thereby increasing induced drag during the pull-up. I don’t think you’d ever get that back from starting the glide from a slightly higher altitude.

    But still open to real world test results.
     
  33. Palmpilot

    Palmpilot Touchdown! Greaser!

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    When an aircraft decelerates, the momentum it loses gets transferred to the air it's flying in.
     
  34. Palmpilot

    Palmpilot Touchdown! Greaser!

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    I would think that the momentary increase in induced drag would be compensated for in some degree by the reduction in induced drag when the pitch is subsequently reduced to maintain best glide speed.
     
  35. luvflyin

    luvflyin Final Approach

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    What about where you are going next. For instance. You're moseying along up there enjoying the view. You are always checkin out the terrain below and pretty much know where you are going if the engine quits. Theres crappy terrain ahead and you know behind you is the way to go. Engine quits. Maybe pitching up and slowing down right now while turning to 'arrest' forward progress away from the friendlier terrain behind you would be a good idea.
     
  36. steingar

    steingar Taxi to Parking

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    BTDT. Pitch up for best glide. Once you hit it play with the trim to your heart's content. You should already be pointed at your nearest or the best landing site you can come up with. Then start on your emergency checklists to get the restart. Were it me, unless changing tanks or the carb heat gives you the restart (did in my one engine out) even if I get the restart I'm headed for my nearest. An engine that quits once can quit again.
     
  37. Mooney Fan

    Mooney Fan Pre-takeoff checklist

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    I hold altitude and bleed her off. I'm not a fan of the roll trim to the stop tactic. If I am successful in restarting the engine, I would not want the extreme pitch up to follow once the throttle is fire walled. My number one goal is to find a place to land. Trouble shooting then begins on the decent to the choice of landing site

    -MF
     
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  38. HornetDriver

    HornetDriver Filing Flight Plan

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    If you're faster than max glide then by definition parasitic drag is greater than induced drag. The relationship between induced drag and AOA is proportional; parasitic drag rises exponentially with velocity. You get twice the payoff from trading parasitic drag for the induced drag, plus the extra altitude. The engineers who get paid to come up with the right answer appear to be correct.

    In a GA aircraft practically speaking it probably doesn't matter very much due to the limited airspeed differential. When you add in the human component a level decel may be just as good or better. But the math is the math.
     
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  39. comanchepilot

    comanchepilot En-Route

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    Always know where you are gonna put it down - then it doesn't matter.

    Every time I'm flying over the city its more inhospitable there than the space between Barstow and Buckeye - lots of places to put down there - flying at 5500 over the San Fernando Valley or Orange County? You're screwed.
     
  40. eaglepilot

    eaglepilot Pre-takeoff checklist

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    Have you written about this experience? I'd be interested to hear about how it all went.

    When I practice engine out by pulling power, my Eagle flys like a rock.:yikes: