* * * * *
(c) Maneuvering pitching conditions. The following conditions must be investigated:
* * * * *
(2) Checked maneuver between VA and VD. Nose-up checked pitching maneuvers must be analyzed in which the positive limit load factor prescribed in Sec. 25.337 is achieved. As a separate condition, nose-down checked pitching maneuvers must be analyzed in which a limit load factor of 0g is achieved. In defining the airplane loads, the flight deck pitch control motions described in paragraphs (c)(2)(i) through (iv) of this section must be used:
(i) The airplane is assumed to be flying in steady level flight at any speed between VA and VD and the flight deck pitch control is moved in accordance with the following formula: [delta](t) = [delta]1 sin([omega]t) for 0 <= t <=t max Where-- [delta]1 = the maximum available displacement of the flight
deck pitch control in the initial direction, as limited by the
control system stops, control surface stops, or by pilot
effort in accordance with Sec. 25.397(b);[delta](t) = the displacement of the flight deck pitch control as a
function of time. In the initial direction, [delta](t) is
limited to [delta]1. In the reverse direction,
[delta](t) may be truncated at the maximum available
displacement of the flight deck pitch control as limited by
the control system stops, control surface stops, or by pilot
effort in accordance with 25.397(b);tmax = 3[pi]/2[omega];[omega] = the circular frequency (radians/second) of the control
deflection taken equal to the undamped natural frequency of
the short period rigid mode of the airplane, with active
control system effects included where appropriate; but not
less than:
[GRAPHIC] [TIFF OMITTED] TR11DE14.023
Where V = the speed of the airplane at entry to the maneuver.VA = the design maneuvering speed prescribed in Sec.
25.335(c).
(ii) For nose-up pitching maneuvers, the complete flight deck pitch control displacement history may be scaled down in amplitude to the extent necessary to ensure that the positive limit load factor prescribed in Sec. 25.337 is not exceeded. For nose-down pitching maneuvers, the complete flight deck control displacement history may be scaled down in amplitude to the extent necessary to ensure that the normal acceleration at the center of gravity does not go below 0g.
(iii) In addition, for cases where the airplane response to the specified flight deck pitch control motion does not achieve the prescribed limit load factors, then the following flight deck pitch control motion must be used: [delta](t) = [delta]1 sin([omega]t) for 0 <= t <= t1[delta](t) = [delta]1 for t1 <= t <= t2[delta](t) = [delta]1 sin([omega][t + t1 - t2]) for t2 <= t <= tmax Where-- t1 = [pi]/2[omega]t2 = t1 + [Delta]ttmax = t2 + [pi]/[omega];[Delta]t = the minimum period of time necessary to allow the prescribed
limit load factor to be achieved in the initial direction, but
it need not exceed five seconds (see figure below).
[GRAPHIC] [TIFF OMITTED] TR11DE14.024
(iv) In cases where the flight deck pitch control motion may be affected by inputs from systems (for example, by a stick pusher that can operate at high load factor as well as at 1g), then the effects of those systems shall be taken into account.
(v) Airplane loads that occur beyond the following times need not be considered:
(A) For the nose-up pitching maneuver, the time at which the normal acceleration at the center of gravity goes below 0g;
(B) For the nose-down pitching maneuver, the time at which the normal acceleration at the center of gravity goes above the positive limit load factor prescribed in Sec. 25.337;
(C) tmax..