Section 29.51 - Takeoff data: general(a) The takeoff data required by §§ 29.53 , 29.55 , 29.59 , 29.60 , 29.61 , 29.62 , 29.63 , and 29.67 must be determined-(1) At each weight, altitude, and temperature selected by the applicant; and(2) With the operating engines within approved operating limitations.(b) Takeoff data must- (1) Be determined on a smooth, dry, hard surface; and(2) Be corrected to assume a level takeoff surface.(c) No takeoff made to determine the data required by this section may require exceptional piloting skill or alertness, or exceptionally favorable conditions.Doc. No. 5084, 29 FR 16150, Dec. 3, 1964, as amended by Amdt. 29-39, 61 FR 21899, May 10, 1996