engine 5

  • Mark created a new forum post in ATA 24 Electrical Power
    Falcon 50 with a noticeable relay chatter in cockpit with external power connected, but not being used.

    The sound was emanating from the right sidewall behind the jump-seat. After gaining access to to distribution panel, the sound was isolated to a relay on circuit card 809J. The relay cycles were extremely fast, I would guess about 5 per second.

    We also noted the sound in the hell-hole and we removed the covers to the electrical components there.

    The relay chatter heard in the back was not always present as noted in the front. When it did act up, the repetitions were the same rate.
    We were able to determine that a relay on circuit card 42P was cycling also.

    Falcon electrical prints can be extremely difficult to follow and I'm not "even" going to attempt to draw out what we found, on this post.

    Shotgun troubleshooting was attempted first by removal of the 4 GCU'S and APU control box from the system. Those efforts did not help.

    The problem was discovered to be one of three capacitors in the "Ground Connector Box" which is mounted just forward of the external power receptacle.

    This box has a 5 amp breaker that extends out to the area where the cord plugs into the aircraft.

    28VDC external power is picked off by this breaker and split numerous times to feed the four respective starter generator systems. 3 engines and the APU. I "did not" want to permanently ruin my eyes trying to trace the actual runs on the wiring prints, but I suspect the power inputs feed each GCU.

    The purpose of the capacitors is unknown. Most likely a circuit protection function..... maybe. They are rather large and gold in color. None of the three showed physical signs of failure.

    A quick way to remove the capacitors from the system is to disconnect a ground wire located right inboard of the box itself.

    Falcon 50 WDM 24-30-01
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