During the first engine start, the pilot squawks that the engine will rotate when the START button is depressed, but spools down as soon as they releases the switch.
Questions:
- What is the most likely defective electrical component?
- Can you start the engine by holding the START button?
Answer:
Please refer to the schematic on page 24-33 of the FlightSafety Westwind Maintenance Training Manual. The start relay (SR) is a two-pole switch with two functions. One pole function routes start control power coming from the GCU through auxiliary start relay (ASR) contacts to the generator start contactor (GSC) coil. This power energizes the GSC, and the starter will then rotate. The other pole function provides a start control holding circuit that closes when the SR is energized, allowing the operator to release the START switch. The start circuit will remain latched until terminated by the EEC/DEEC or manually by pressing STOP. In this scenario, the starter rotates as long as the START switch is held in the start position, but stops as soon as the switch is released. The most likely defective component is the holding circuit electrical contacts in the start relay. Because the starter will operate when START is pressed, we have proven the circuit to and through the GCU is functioning. Also, the ASR is functioning normally and energizing the SR. The SR coil is functioning along with the contacts that energize the GSC because the starter is rotating. Replacing the SR should resolve the fault.
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