automatic ignition system control. Manual Control
The EEC and the CDS/DEUs monitor the position of these flight compartment components:
1. Ignition selector switch 2. Engine start switches 3. Start levers.
Each CDS/DEU sends a digital data signals to the EEC with switch position information.
The EEC looks at the CDS/DEU digital data signal and the analog signal. The EEC compares the two signals. If the CDS/DEU 1 or CDS/DEU 2 digital data signal to the EEC logic stops, the EEC uses the analog signal as the flight compartment input.
The EEC uses switch position data to control four internal EEC ignition on/off switches. These switches control the 115v ac power to the ignition exciters. Each EEC channel (A and B) controls one ignition on/off switch to each ignition exciter. Only one EEC channel is active at a time. Therefore, only one ignition on/off switch, for an ignition exciter, works at a time. The other EEC channel is in the standby mode. 115v ac power goes to the EEC when you move the start lever to the idle position. The 115v ac power goes through the start lever switches that are in the closed position.
The ignition exciters receive power and supply 15,000 to 20,000v dc of electrical power to the spark igniters. The voltage goes across the electrodes of the spark igniter to make sparks. Flameout Protection
The EEC turns on both ignition systems of an engine automatically if one of these conditions are true:
1. The engine start lever is in the IDLE position, the start switch is in the FLT position
2. The engine start lever is in the IDLE position, start switches in GRD or CONT position, N2 less than idle and the airplane is in flight
3. The engine start lever is in the IDLE position, engine speed decreases uncommanded or N2 is less than 57% and N2 is more than 50%. For this condition only, both ignition systems are energized for 30 seconds GUN 001-099, 101-122, 155-157
The engine start lever is in the IDLE position, the airplane is in flight, start switch is in the OFF position, N2 speed is less than idle, and N2 speed is more than 5%.
GUN 201-999
The engine start lever is in the IDLE position, the airplane is in flight, start switch is in the AUTO position, N2 speed is less than idle, and N2 speed is more than 5%. GUN ALL
The EEC turns ignition off when these conditions are true:
1. Engine start switches are not in a position that command ignition operation 2. Hot start on the ground 3. Wet start on the ground
4. The engine start lever is in the IDLE position, airplane is on the ground, the engine completed a start, N2 speed goes less than 50% and EGT is more than the start limit
5. Ignition system energized because of N2 less than idle or uncommanded decrease in N2 and engine speed goes back to normal. GUN 201-999 Automatic Ignition
The EEC turns on the selected igniter(s) when the flaps are not up or the engine anti-ice is selected on. To keep ignitors off when they are not needed or have no effect, more EEC logic is used to turn ignitors on when all of these conditions are true: 1. Automatic ignition feature is enabled in the CDS software 2. N2 is more than 20% (engine running)
3. Burner pressure is less than the igniter firing limit pressure(175 psia) 4. Thrust lever resolver angle is more than 50 degrees or the airplane is in-flight
5. Engine anti-ice is selected on or wing flaps are not up and airplane altitude is less than 18,000 feet. GUN ALL
IGNITION - FUNCTIONAL DESCRIPTION
IGNITION - OPERATION
General
These are the flight compartment controls you use to operate the engine ignition: 1. Start lever
2. Ignition selector switch 3. Engine start switch. Start Lever
The start lever controls ignition electrical power to the EEC. The EEC receives 115v ac power for ignition when the start lever is in the idle position. Ignition Selector Switch
There are three ignition selector switch positions: 1. IGN L (Left spark igniter) 2. IGN R (right spark igniter)
3. BOTH (both spark igniters). Engine Start Switch
There are four engine start switch selection positions: 1. GRD (ground start) 2. OFF
3. CONT (continuous ignition) 4. FLT (flight).
Engine Start Switch Position (GRD)
The engine starter engages and turns the engine when you put the engine start switch to the GRD position. You supply ignition and fuel to the engine combustor when you move the start lever to the idle position.
You use the GRD position to start the engine on the ground. See the engine starting chapter for more information. Engine Start Switch Position (OFF)
Usually the igniters do not operate when the start switch is in the OFF position. However, the EEC turns on the ignition system automatically if the EEC sees a possible engine flameout condition. See the functional description page in this section for more information about this function.
IGNITION - OPERATION
Engine Start Switch Position (AUTO)
Usually the igniters do not operate when the start switch is in the AUTO position. However, the EEC turns on the ignition system automatically if the engine cowl anti-ice system is turned on or flaps are down. The EEC will turn on igniters if it
sees a possible engine flameout condition. See the functional description page in this section for more information about this function. Engine Start Switch Position (CONT)
The flight crew may turn the engine start switch to the CONT position at these times: 1. Takeoff 2. Approach
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