PROTECTIONS

Criteria: 22-1022, 22-1038, 22-1052, P3511, P3686, SA
1 Applicable to: MSN 0179-0225, 0257-0386, 0411, 0480-4078
OBJECTIVES
One of the PF's primary tasks is to maintain the aircraft within the limits of the normal flight envelope. However, some circumstances, due to extreme situations or aircraft mishandling, may provoke the violation of these limits.
Despite system protections, the PF must not exceed deliberately the normal flight envelope. In addition, these protections are not designed to be structural limit protections (e.g. opposite rudder
pedal inputs). Rather, they are designed to assist the PF in emergency and stressful situations, where only instinctive and rapid reactions will be effective.
Protections are intended to:
? Provide full authority to the PF to consistently achieve the best possible aircraft performance in extreme conditions
? Reduce the risks of overcontrolling, or overstressing the aircraft
? Provide PF with an instinctive and immediate procedure to ensure that the PF achieves the best possible result.
BANK ANGLE PROTECTION
Bank angle protection prevents that any major upset, or PF mishandling, causes the aircraft to be in a high-bank situation (wherein aircraft recovery is complex, due to the difficulty to properly
assess such a situation and readily react). Bank angle protection provides the PF with full authority to efficiently achieve any required roll maneuver.
The maximum achievable bank angle is plus or minus:
? 67 °, within the Normal Flight envelope (2.5 g level flight)
? 40 °, in high Speed protection (to prevent spiral dive)
? 45 °, in high Angle-Of-Attack protection
HIGH SPEED PROTECTION
When flying beyond maximum design speeds VD/MD (which are greater that VMO/MMO), there is an increased potential for aircraft control difficulties and structural concerns, due to high air loads. Therefore, the margin between VMO/MMO and VD/MD must be such that any possible overshoot of the normal flight envelope should not cause any major difficulty.
High speed protection adds a positive nose-up G demand to a sidestick order, in order to protect the aircraft, in the event of a dive or vertical upset. As a result, this enables a reduction in the margin betwen VMO/MMO and VD/MD.
 

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Therefore, in a dive situation:
? If there is no sidestick input on the sidestick, the aircraft will slightly overshoot VMO/MMO and fly back towards the envelope.
? If the sidestick is maintained full forward, the aircraft will significantly overshoot VMO/MMO without reaching VD/MD. At approximately VMO +16 / MMO +0.04, the pitch nose-down authority smoothly reduces to zero (which does not mean that the aircraft stabilizes at that speed).
　
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