5
$\begingroup$

For this question, please have in mind these excerpts from the 14 CFR 25.107 - Takeoff speeds.

"(d) VMU is the calibrated airspeed at and above which the airplane can safely lift off the ground, and con- tinue the takeoff. VMU speeds must be selected by the applicant throughout the range of thrust-to-weight ratios to be certificated. These speeds may be established from free air data if these data are verified by ground takeoff tests."

and VR must be:

"(iv) A speed that, if the airplane is rotated at its maximum practicable rate, will result in a VLOF of not less than —

(A) 110 percent of VMU in the all-engines-operating condition, and 105 percent of VMU determined at the thrust-to-weight ratio corresponding to the one-engine-inoperative condition; or

(B) If the VMU attitude is limited by the geometry of the airplane (i.e., tail contact with the runway), 108 percent of VMU in the all-engines-operating condition, and 104 percent of VMU determined at the thrust-to-weight ratio corresponding to the one-engine-inoperative condition."

My question is: why does having a geometry-limited aircraft lead to lower VLOFs? Is it because, since the aircraft cannot reach the angle of stall because of its limitation, the VMU for such airplanes is greater than the stall speed, and thus the maximum Lift Coefficient has not been reached and therefore it offers a higher safety margin regarding stall?

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.