PPRuNe Forums - View Single Post - Robin DR400/180 stick back at start of the roll
Old 15th Jul 2016, 08:15
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Capn Bug Smasher
 
Join Date: Oct 2014
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I am a super fan of Budd Davis over at Airbum.com whose article on the subject I found illuminating. Here it is - How Short is it Really?

If you don't want to read it all, here is the most pertinent section:

"The procedure is fairly cut and dried but does entail just a few nuances calling on you to really see what’s happening in the windshield.

We’ll start the takeoff (we’re assuming a tri-gear airplane) as we normally would, but, as soon as the airplane is rolling fast enough that we sense some life in the elevators, we position the yoke aft of neutral and hold it there. What we’ve done is insert a nose-up command in the elevator before the airplane has enough speed to pick the nose up. Then, when the airplane accelerates through the speed required to unstall the tail and pick the nose up, we immediately release some backpressure. At the same time, we look over the nose and visually fixate on where the nose is in relation to the horizon and, from that point on, our entire focus is to hold the nose in that position

Because the airplane is accelerating, if we don’t release back pressure and set a given nose attitude, the nose will continue coming up as the airflow over the tail increases with speed. What we’re trying to do is establish a slightly nose up attitude that positions the nosewheel something like six inches off the ground. Our goal is to hold that attitude firm, which will require us to gradually ease off the backpressure as the airplane accelerates. The first few times you do it, it’ll be a little counter intuitive because we’re actually moving the yoke forward slightly as the airplane takes off. The name of the game, however, is to use the nose like a rifle sight and absolutely nail it on a given position on the horizon and hold it there no matter what.

The net result of this little exercise is that the nose will come up, the airplane will run on the mains for a few seconds and will lift off when, and only when, the lift/speed curves cross and exactly match the environment in which the airplane is operating. It’ll compensate for every single thing having to do with the takeoff and won’t leave the ground until every factor is right. This is an instance where we can’t possibly know as much as the airplane does in terms of what is needed at that precise moment, in that precise location, with that specific airplane to safely leave the ground and be guaranteed of a positive rate of climb."
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