ATA 80

Starter Sequence
The left starter sequence is the same as the right only change No. 1 and No2. and right and left.
1. Power flows from the No. 2 distribution bus and start circuit breaker to the right start switch.
2. From the right start switch to the left start relay SR1. If the left start circuit is not in use the SR1 will be de-energized and these contacts of SR1 will be closed.
3. From SR1 to GLR2. With no system malfunction GLR2 will energize as soon as battery power is applied, and these contacts will also be closed.
4. From GLR2 to pins K and X of the right generator control unit.
5. the power that comes in pins K and X goes out pin G of the GCU assuming the engines is below 50% N2 and the stop position of the start switch has not been pressed.
6. From pin G of the right generator control unit, power goes to the right DC contactor box and does the following:
(A) Arms the ignition circuit. There is no ignition until the right power lever is moved out of stop cock.
(B) Energizes the Start Relay (SR2) and the Auxiliary Start Relay (ASR2)
7. The Start Relay (SR2) does the following:
(A) Latches in the right start circuit so the start switch can be released.
(B) Disables the right feeder fault circuit during the start.
(C) Energizes and closes the right start contactor (GSC2).
(D) Disables the left start circuit
8. The Auxiliary Start Relay (ASR2) does the following:
(A) Opens the left bus tie contactor.
(B)Opens the left feeder fault circuit during the start.
(C) Closes the left start contactor. This is used for the cross start and will only happen during the second engine start, if the operating generator switch is on and there is no external power connected to the airplane bus system.
9. At corrected 50% N2 the right engine computer will supply a ground to pin N of the right GCU. This will cause a relay in the GCU to energize which will open its contacts and stop the power from coming out of pin G. This will terminate the start.
10. Pushing the right start switch to the STOP position will also supply a ground to pin N of the GCU and terminate the start, at any RPM below approximately 50% N2.

NOTE:
The only thing the engine computer has to do with the engine start , other than the obvious safety features, is to stop the start and provide enrichment. Everything else to do with starting is strictly a function of the DC electrical system.

ATA 80

Starter Sequence Troubleshooting

1. Select voltmeter in cockpit to Generator position

2. Press and hold the ammeter/voltmeter and press the start button to read the start buss volts.

a) If you receive voltage on the meter this tells you if the starter is receiving voltage and the continuity is correct-(starter is getting power but not turning, brushes, bearings worn etc.)

b) If no voltage is present, than starter is probably OK. Starter is not getting power (RCR, SR-1 etc.)

3. Depress and hold the Start Button in.

4. Bring Throttle out of idle cut-off.

a) If ignition light comes on, then the power is good thru the GCU and SR, or the GSC may be bad.

b) If opposite buss-tie opens and buss goes dead then ASR pulled.

c) Release start button.If ignition light stays on when start switch is released, then the SR is good.

ATA 24

Aircraft Grounding Points
Several instances have been reported of failing electrical grounding points. These connections have developed significant arcing, enough so that the cables have eroded a hole completely through the bulkhead frames. Compliance with the Service Bulletins 1124-24-120 will help minimize this. The areas to pay special attention to are the grounding cable GND 87, 88, 89 and 90, these are the attached at frame station 383 on the ceiling. Also the external power connection to the airframe, this is located at frame station 402.810. Holes in the frame may not be visible until the cables are removed.

ATA 80

Engine Start/Fail
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:

1. What is the most likely defective electrical component?
2. 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.