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What is a reasonable (or typical) control surface deflections required for takeoff? I would like to know two ball park values if possible

  1. elevator deflection for conventional transport aircraft
  2. elevon deflection for aircrafts with no horizontal tail
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  • $\begingroup$ what's a "conventional transport aircraft"? a Cessna 172, or a B747? what have you searched? what have you found and why was it not satisfactory? how are two random numbers given by internet strangers going to be helpful? $\endgroup$
    – Federico
    Apr 23 at 9:34

1 Answer 1

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Required for takeoff - essentially none, when an aircraft reaches takeoff speed then it will fly with minimal deflection of the control surfaces provided it’s trimmed correctly for that power and altitude. Aircraft with ample thrust and/or speed can rotate to achieve a high rate of climb and so a pilot might apply a small control input over a period of time or a radical input for a short period. The angle of deflection would depend on the physical (or fly-by-wire firmware) linkage between the stick and the elevators, which would again be designed based on the size of the control surfaces and a number of other factors. To Answer your question directly, the required angle is, or should be, zero.

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  • $\begingroup$ "provided it’s trimmed correctly for that power and altitude." Well, no, trim also determines (indicated) airspeed. If the plane takes off (because of the angle of attack due to landing gear geometry etc.), but is trimmed for a higher airspeed, it will immediately pitch forward again. Trim is achieved by control surface deflection (in various, more or less direct ways), but of course one can argue what the reference position is against which you would measure the required deflection for takeoff. $\endgroup$ Apr 23 at 18:42
  • $\begingroup$ When reaching V<sub>r</sub>, most pilots make a significant pitch control input to rotate the a/c to the desired pitch attitude. $\endgroup$
    – Jim
    Apr 23 at 19:40
  • $\begingroup$ @Jim they do and this is to achieve a desired rate of climb. Unless the undercarriage presents the airframe at an angle where flight isn’t achievable, the aircraft will (eventually) get off the ground without rotation $\endgroup$
    – Frog
    Apr 23 at 21:42
  • $\begingroup$ @Frog - Yes, but that is not typical (as OP asks). $\endgroup$
    – Jim
    Apr 24 at 1:07
  • $\begingroup$ I’m reading the ‘required for takeoff’ part, I may have misinterpreted the OPs intent $\endgroup$
    – Frog
    Apr 24 at 1:46

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