AC 27-1B, Chg 7 2/4/2016
(7) For any single failure or any combination of failures of the AFCS that is not shown to be extremely improbable, the recovery should not result in a loss of height greater than half of the minimum use height.
(8) For coupled flight below the previously established VMINI, at the maximum demonstrated winds, the helicopter must be able to maintain any required flight condition and make a smooth transition from any flight condition to any other flight condition without requiring exceptional piloting skill, alertness, or strength, and without exceeding the limit load factor.
(9) For coupled flight below the previously established VMINI, the following stability requirements replace the stability requirements of paragraph IV, V, and VI of of Appendix B to part 27:
(i) Static Longitudinal Stability: The requirements of Appendix B to part 27, paragraph IV are not applicable.
(i) Static Lateral-Directional Stability: The requirements of Appendix B to part 27, paragraph V are not applicable.
(iii) Dynamic Stability:
(A) Any oscillation must be damped and any aperiodic response must not double in amplitude in less than 10 seconds. This requirement must also be met with degraded upper mode(s) of the AFCS.
(B) After any upset, such as a wind gust, the AFCS must return the aircraft to the last commanded position within 10 seconds or less.
(10) With any of the upper mode(s) of the AFCS engaged, the pilot must be able to manually recover the aircraft and transition to the normal (Appendix B to part 27) FR flight profile envelope without exceptional skill, alertness, or strength.
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2/4/2016 FIGURE AC 27.APХ B-1 ROTORCRAFT DYNAMIC STABILITY 35 30
ACCEPTABLE
REQUIREMENTS FOR IFR
UNACCEPTABLE Page Apdx B - 21 -0.2 0.05 Ø.15 AC 27-1B, Chg 7
DAMPING RATIO
AC 27 APPENDIX B (AMENDMENT 27-51) AIRWORTHINESS GUIDANCE FOR ROTORCRAFT INSTRUMENT FLIGHT.
a. Explanation.
(3) Amendment 27-51 revised section VIII (b)(5)(i), which requires isolating the pilot instrument system from any other operating systems, to only apply to pneumatic systems. This change allows other types of pilot instrument systems to be connected to other systems on the rotorcraft and allows the use of modern technology to monitor and display highly integrated information. This guidance remains unchanged except paragraphs (b)(9)(v) and (b)(9)(vi) of this AC section do not apply to nonpneumatic systems.
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