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Engine Start and Ignition Circuit Description T.O. 1T-38A-2-7 [[crossed out]] ignition generator supplies power to the main and afterburner igniter plugs, causing them to fire simultaneously. [[/crossed out]] 6-6. On Block 20 and later aircraft (see figure 6-1), 28-volt dc power from the L ENG START & AB CONT and R ENG START & AB CONT circuit breakers is fed to the engine start left and right pushbutton switches on each cockpit left vertical panel. The circuit breakers are on the engine start and ignition dc breaker panel on the front cockpit left console. Pressing the start switch in either cockpit momentarily applies dc power to the engine ignition holding relay. The holding relay, when energized, pulls its contacts to the closed position. The contacts remain in the closed position as long as the holding relay is energized. This is governed by the engine ignition time-delay relay. DC power is then applied to the time-delay relay and the ignition control relay thru the closed contacts of the holding relay and ignition time-delay relay. Simultaneously, the holding relay is energized, setting up the holding circuit. The engine ignition control relay connects power to the starting air diverter valve, positioning the valve to direct starting air to the selected engine. When power is applied to the time-delay relay, the electronic timing circuit within the relay becomes energized, starting its timing cycle. The time-delay relay operates in approximately 30 seconds, momentarily pulling its contacts to the open position. This action breaks the circuit, removing power from the holding relay and engine ignition control relay. If at this time the engine has not started, the start switch must again be momentarily closed to activate the circuit and restart the timing cycle. When external ac power is applied to the aircraft, the power is fed thru the ENG IGN & R AUTOSYN INST circuit breaker connected to the phase B bus to energize the ignition power transfer relay. [[left margin]] Enabled. "activated" by throttle [[/left margin]] When the ignition power transfer relay is energized, 115-volt ac is then applied to the engine ignition generator by closed contacts of the ignition power transfer relay, engine ignition control relay, and the left throttle switch. Under emergency starting conditions, if ac power is not available, the engine ignition may be activated with dc power by placing the battery switch at the ON position; battery power is then supplied to the static inverter circuit breaker placarded IGNITION INVERTER on the engine start and ignition dc circuit breaker panel. From the circuit breaker, dc power is applied to the static inverter by closed contacts of the engine ignition control relay and engine ignition power transfer relay. The inverter converts dc power into ac, which is applied to the engine ignition generator by closed contacts of the ignition power transfer relay, engine ignition control relay, and the throttle switch. The throttle switch is closed by manually moving the throttle lever in either cockpit forward out of the OFF position. The ignition generator supplies power to the main and afterburner igniter plugs, causing them to fire simultaneously. [[column break]] [[crossed out]] 6-7. The afterburner circuit on Blocks 10 and 15 aircraft is part of the engine start and ignition circuit and is initiated by advancing the throttle lever in either cockpit beyond the military (MIL) range into afterburner (MAX) range. This action closes the afterburner switch mounted in the front cockpit throttle quadrant. DC power is then applied to start control relay No. 1 thru the normally closed contacts of the afterburner time-delay relay. Simultaneously power is applied to the electronic timing circuit in the time-delay relay. The ignition power transfer relay, start control relay No. 1, and the throttle switch control ac power from the ENGINE IGNITION circuit breaker to the ignition generator and igniter plugs (see figure 6-1). After the time-delay relay and its internal timing circuit have been energized for approximately 30 seconds, its normally closed contacts open and remain open until the throttle lever in either cockpit is removed from the afterburner range. When the contacts are open, power is removed from start control relay No. 1, disconnecting the circuit. The ignition generator supplies power to the two igniter plugs. The main igniter plug is mounted in the engine combustor section, and the afterburner igniter plug is mounted in the engine diffuser section. Both plugs fire simultaneously when power is applied. If the afterburner as not been ignited at this time, the circuit may be reenergized by placing the throttle lever back to the military range and then bringing it forward into the afterburner range. [[/crossed out]] 6-8. The afterburner circuit on Block 20 and later aircraft is part of the engine start and ignition circuit and is initiated by advancing the throttle lever in either cockpit beyond the military (MIL) range into afterburner (MAX) range. This action closes the afterburner switch mounted in the front cockpit throttle quadrant. DC power is then applied thru the normally closed contacts of the engine ignition time-delay relay to the engine ignition control relay. The ignition power transfer relay, engine ignition control relay, and the throttle switch control ac power from the ENG IGN & R AUTOSYN INST circuit breaker to the ignition generator and igniter plugs (see figure 6-1). After the time-delay relay and its internal timing circuit have been energized for approximately 30 seconds, its normally closed contacts open and remain open until the throttle lever in either cockpit is removed from the afterburner range. When the contacts are open, power is removed from the engine ignition control relay, disconnecting the circuit. The ignition generator supplies power to the two igniter plugs. The main igniter plug is mounted in the engine combustor section, and the afterburner igniter plug is mounted in the engine diffuser section. Both plugs fire simultaneously when power is applied. If the afterburner has not been ignited at this time, the circuit may be reenergized by placing the throttle lever back to the military range and then bringing it forward into the afterburner range. 6-4
