AFGS�87219B APPENDIX A
c. To maintain confidence in the reliability of the emergency power source it should be given an operational check before each flight if possible. If not, other means of verifying operational readiness should be provided.
d. Thirty minutes is the recommended minimum time for the emergency power unit to provide electrical power. This is generally sufficient for the crew to regain control of the aircraft and make an emergency landing.
REQUIREMENT LESSONS LEARNED (A.4.2.3)
a. Many modern multi-generator aircraft have experienced ultimate failure of the main electrical power system.
b. Serious consideration has been given to eliminating the emergency generator from several programs as a cost and weight savings. However, on several occasions during the flight-test program the emergency generator was required to supply power following multiple failures of the main electrical system.
c. The method of returning emergency loads to the normal power source on one aircraft was changed from automatic to manual following an in-flight incident. A flight control transient resulting from main generator failures had just settled out when normal power was again restored. When the flight controls were then automatically transferred back to main power, the crew was surprised with a second disturbance as severe as that caused by the original failure.
d. Another incident illustrates the criticality of emergency power control logic. A partial failure of the hydraulic system powering the emergency generator caused it to be powered up to speed by an overlooked hydraulic "sneak circuit." Then when the emergency generator tried to power the essential bus there was insufficient hydraulic power to support it. As a consequence, the essential bus cycled on and off a malfunctioning emergency power unit thereby adding a critical electrical problem to the original hydraulic failure.
A.4.2.4 Emergency power.
a. The capability to supply all essential loads shall be determined by analyses and tests as follows: ------------.
b. Compliance with the load transfer requirements of 3.2.4.b shall be verified by analyses and tests as follows: ------------.
c. Compliance with the operational readiness requirements of 3.2.4.c shall be verified by analyses and tests as follows: ------------.
d. Compliance with other emergency power requirements shall be verified as follows:
------------.
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