It appears to be common practice in the STOL competitions to raise the tail when the plane is stopped before takeoff. It makes sense that this would decrease the wing angle of attack, thereby reducing the drag as the plane rolls out. But usually it falls once the brakes are released. The tail is elevated partially by the lift of the tail, but more significantly the force couple created by the thrust and the resisting brake load. This is why the tail does not stay up once the airplane starts rolling. It takes a fair amount of energy to lift the tail. Is this wasted energy, or is there some benefit to lifting the tail that shortens the ground roll?

OH YEAH! this will be fun! Notice that plane's that don't raise the tail get off just as quick with out banging the tail.

I'm curious as well. I had assumed it was just to allow the engine a moment to develop full thrust before consuming any of the takeoff roll.

I'm giggling like a little girl.
I will bite my lip and just watch though.
No I can't, I got to say something!!!!
Nope, holding my tongue.
Good question though Scolopax.

Not really on topic, but from a practical sense, I'd say the main benefit is to prevent dragging your tiny tailwheel through the puckerbrush and babyheads. I'd imagine that aerodynamic benefits are negligible.

the 2013 experimental class at the Valdez contest (maybe the all around winner too?) was won by a PA-11 that took off and landed both three point.

Any airplane will accelerate much quicker with all wheels off and in low ground effect. The idea is to get tail up and mains off as soon as possible and then stay level and low. Powerful airplanes can drive the tail up with prop blast and the brakes on. Powerful airplanes can get off into low ground effect with the tail down. Little engine airplanes have to work a little harder to get off and into low ground effect. Little engine airplanes are the ones that often need both the level on the mains and the mains off as soon as possible techniques to safely get out of a tight area.

I'm no STOL champion, but just looking at the physics of it, it's hard to imagine that the slight realignment of the thrust vector would be enough to offset the amount of energy expended in keeping the tail up, at least on our 180-class ships.
Maybe on a super-powered light Cub it could make a difference.

On rough terrain though, there's other reasons to keep the tail up.

OK...I am just going to bite my fingers to keep from typing...

patrol guy wrote:the 2013 experimental class at the Valdez contest (maybe the all around winner too?) was won by a PA-11 that took off and landed both three point.

Uh.... Negative....

Yes he was the all around winner, but no he did not land, nor take off in three point. After physically watching thousands of take offs in that airplane, and shooting up close measured video of it, I can say unequivocally that it takes off shorter when started tail up, if you rotate correctly, everytime. This is not speculation, it is measured, taped and recorded. Done improperly it will cost more feet than a three point departure, by a long shot.
But that was a very ' purpose built' airplane. The same may not be true, or even possible in other ships.

Also, Franks J3 ( it is not a pA11) has no tail wheel, which is one reason you'll never see it land 3 point on purpose

Having said all that,

It's my opinion that this technique is really aircraft, mission, and pilot dependent.

It does not fit any plane I fly well, it doesn't compliment my missions, and I can't bring myself to treat a prop or engine like that. Consequently , like the ole 'tail up taxi' I have no use for this exercise.

Frank on the other hand, built an airplane with one mission. Extensive practice (as in all day, every day, all summer) video showed the airplane liked it, and he was well versed it... So it was a success...


Take care, Rob

We bashed this one around more than once in another thread. The energy required to raise the tail has to come from somewhere. That energy, by definition, is subtracted from the energy available to accelerate the airplane.

Whether this tail-raising energy loss is more or less than the energy loss from additional drag (from the airplane plowing through the air at a nose-high attitude versus a level attitude)... will depend on the design and geometry of each individual airplane.

In pondering this, I thought that maybe dropping the tail directly contributes to the forward motion of the mains upon brake release. So, in a competition, you can store some potential energy before the roll begins. The dropping action of the tail works against the center of gravity, which wants to remain stationary. This can be helpful getting some big tires rolling.

cropduster13 wrote:OH YEAH! this will be fun! Notice that plane's that don't raise the tail get off just as quick with out banging the tail.

This is correct. An airplane will not fly until it is ready, no mater what the technique. I noticed a lot of the "in vogue" pilots banging their tails and going no where. I liked it. made me feel not so inept.

At about 9:30 in the video below is something close to the technique that works best for me in the Carbon Cub. Tail up to get a good sight picture (especially flying from the back seat) and then tail held low but with tailwheel off the ground to get the AOA high on the wing but keep the tailwheel out of the rocks or whatever (assuming you were off airport). But I agree with Contact flying that with 180HP I can brute force it into low ground effect with the tail low and continue to accelerate. With our 100 HP sport cub (same exact air frame and wing), it works much better to keep the tail up, get the mains off and accelerate in ground effect before climbing out. Just my observations, your mileage may vary.

https://www.youtube.com/watch?v=fOZfJ7t6rwI

EZ is spot on.... This deal is 100% aircraft dependant... Then if it suits the A/C, it is pilot dependant, because as i pointed out above, if you flub it up, the penalty is worse than if you just fly off 3pt...and then if it suits the A/C and pilot, it is mission dependant....

Weather it works for any of us is really irrelevant to weather it works or not It has been proven to work, and not work, time and time again

Exo....your 'in vogue' pilots were the inept ones in slow moon video of the slat tests we can actually watch the cub wing load itself. This video was shot with markings on the pavement, and markings on the tire, at prescribed DA's. Anytime the tail hits the ground on rotation, the wing is unloaded which is wasted time, energy, and distance, to get it back to where it was ready to fly... This is why franks bird has to tailwheel... To allow for more rotation, without going to even longer gear or heavier tires.
FWIW during practice the morning of the Valdez comp, he sheared a valve stem, not having a spare tube the right size, he had to change out to heavier tires. When you are flying at that level of precision every tiny little thing adds up...

Take care, Rob

I'm w ez and rob on this one.
I have the least experience in the lighter planes such as cubs in comparison to say 180's and heavier.
I toyed w the tail up take off deal years ago because like some, I'd seen it or heard about or wondered about it. Which I think may have a lot to do with people doing it in itself. (I was asked to start using paragraphs in my writing so is that my phenomal writing skills will look so much gooder. So heres my second paragraph. )
In my own observation, especially on the 180 with the "flying tail"; it makes more difference to me to find the sweet spot on the trim setting to get off shorter. I believe it will cost you footage trying to make the tail fly to soon when not necessary as well. Most of the time if I have found myself "forcing" anything in flying, it's not the best way.