Hey guys. Has anyone here ever been told not to use max up elevator on takeoff from soft/short fields? I watched a yt video of a twin otter crashing on t/o and one commenter said the up elevator was causing unnecessary drag. Most people on the Internet don’t know what they’re talking about and just wanna sound smart. I use the technique to protect my delicate nose wheel, but it got me thinking… the extra drag argument has never really been discussed during my training. Thanks.
My training (or what I remember from those golden days … ) tells me exactly the same thing. Then again, a more complex and heavy machine like the Twin Otter might require more subtle procedures, more delicate handling. Surely they’ll be in the POH? My own simple ultralight is taxied and taken off with the stick fully back, and held back until the nose wheel lifts off; all the while, flaps and trim are at their extreme positions. But I seem to remember some pilot only extending flaps when reaching lift-off speed, for the same reason as you mentioned: minimal drag during the initial run.
Then again, the Twin Otter could only suffer from excess drag by overrunning the runway, not by crashing… Not having seen the video, I wonder if it lifted off too briskly, then stalled? That’s a danger I have been amply warned against: the moment my nosewheel does lift off, forward goes the stick, to maintain the horizon at a constant point, more or less the same as where it is during initial climb.
…the up elevator was causing unnecessary drag.
If it was the little drag of the elevator which made him crash on takeoff, then he got his calculations wrong in the first place. Of all things that produce drag in an aeroplane, the elevator – whatever position it is in – must be among the least important ones.
When I was taught to do short field take-offs in the Arrow, this was the technique taught. Hold the yoke fully back until take off and the feed it back in as the aircraft climbed away. It worked perfectly fine for years on hard runways. I’d tried once or twice, only applying elevator close to minimum take off speed to see if the reduced drag made any difference, and there was no noticeable difference.
Then one day I tried it on a grass runway (Manchester Barton). The grass was not long. The aircraft reached take off speed attempted to take off (maybe climbed a 2 cm) and settled back. It did this twice. I figured I’d one more shot then I needed to brake, but the aircraft wasn’t accelerating any further. So I removed the up elevator (made it neutral) and the aircraft accelerated further and then I reapplied 95% up elevator and it climbed away normally.
The aircraft was heavy, but most definitely below MTOW (The calculations had been done with a weighing scales).
So in my experience the difference isn’t noticeable on a hard surface, but there is an effect, small as it may be, and can be important if other factors come into play.
Agree. Generally, on a soft field, the potential drag from the wheels on the ground is so much higher than the additional drag of a deflected elevator. As soon as the front wheel is off the ground however, you can and should relax the elevator just so much as to keep it in the air.
It depends whether you perform a soft or a short field takeoff. Those are a lot different and need different procedures. Usually a soft field requires lifting the nose wheel quite fast and a short field requires long low-alpha takeoff rolls with low induced drag. Depends a bit on the circumstances and aircraft used.
Of course, I was talking soft fields. Saw only now that the OP mixed soft and short in one question. Totally different techniques…
I think the OP is talking about the soft field takeoff.
The full elevator does produce a lot of drag, which is why on a hard runway the takeoff roll using the “soft field takeoff” method is longer than with a conventional takeoff.
I guess there must be a crossover point, based on the surface quality, where you get a net gain using the soft field takeoff method.
It is tricky since the numbers are not normally in the POH and in any case you can’t judge the quality until, ahem, after you have landed there.
Some mixed theories here concerning the relative amount of drag being produced by the elevator… hmm. I read in my aa5 poh that using a full yoke back technique increases your TORR because you’re basically doing a wheelie, thus creating a higher alpha on the wing which in turn increases drag. Makes sense right?
Ps: I know soft and short field are different techniques, I was just too lazy to separate them. Apologies.
Drag caused by the elevator down force on the tail forcing the main wheels into the mud, rather than lifting the noewheel and tilting the wing to produce lift? Not the extra aerodynamic drag of the elevators at low speed.
Position of main wheels relative to C of G on different aircraft, and different power of tailplane, may mean different aircraft manuals have different soft field techniques.