Engine Alternator Stator
the engine during armament firing. When firing
aircraft armament, a signal from the armament
The engine alternator stator is an engine-
trigger switch activates the armament-firing logic
driven single-phase, ac electrical-output unit
circuit in the control amplifier. The amplifier logic
circuit causes ignition operation to activate.
mounted on the engine accessory gearbox.
Ignition operation ends after a 1-second time delay
It supplies electrical power to the engine,
in the amplifier logic circuit following release of
independent of the aircraft electrical system. It
contains three sets of windings. Two windings
the armament firing trigger.
supply electrical power to the ignition exciter, and
the third supplies electrical power to the control
amplifier.
REVIEW SUBSET NUMBER 2
Ignition Operation
Q1. Why is timing not a factor in jet engine
ignition systems?
As you read this section, refer to figure 5-6.
With the ignition switch ON, the engine cranking
for starting, and throttle advanced to 10-degree
power lever angle (PLA) position, current flows
from the alternator stator to power the control
Q2. What unit in an ignition system develops
amplifier. At the same time, the PLA ignition
enough voltage to produce a spark?
switch in the fuel control closes. The gas generator
(Ng) speed logic circuit closes the ignition relay
to provide ignition when Ng is within the 10 to
Q 3 . At what engine RPM does ignition
completes a circuit from the alternator stator
normally stop?
ignition windings, through the ignition exciter,
to the igniter plugs. Current flows from the
alternator, through the control amplifier, to the
ignition exciter. At the ignition exciter, current
Q4. In the capacitor-discharge ignition system,
what total number of pulses must occur
is intensified and discharged as a high-voltage
output, and conducts through the igniter cables
before the capacitor discharges?
to the igniters. Current crossing the gaps in the
igniters produces a continuous high-intensity
spark to ignite the fuel mixture in the combustion
chamber. When engine speed reaches 8,500 RPM,
Q5. Engine ignite automatically reactivates
Ng and interturbine temperature (ITT) reaches
when either of what two conditions occurs?
operating range, a signal from the T5 temperature
detectors flows through the T5 circuit to the
control amplifier ignition logic circuit. The control
ENGINE TEMPERATURE
amplifier ignition relay opens and ignition ends.
Combustion then continues as a self-sustaining
CONTROL SYSTEMS
process.
Learning Objective: Recognize operating
Ignition automatically reactivates when either
conditions and characteristics of aircraft
a flameout occurs or when aircraft armament
engine temperature control systems.
fires. When T5 temperature drops more than
800F (427C) from T5 selected by PLA, the T5
detectors signal control amplifier T5 flameout
On most reciprocating engines, the engine
logic to close the amplifier ignition relay. This
cowl flaps control cylinder head temperature
(CHT). In turbine-powered engines, turbine
activates ignition system operation. Ignition
temperature is controlled differently. Engine
continues until engine operating temperature is
temperature is a measure of power, and tempera-
again normal and the 800F temperature error
ture is a product of fuel consumption. In most
signal cancels, causing the control amplifier to end
turbine-powered aircraft, then, the pilot selects
ignition operation.
desired power through a mechanical linkage to the
An armament-firing protection circuit pre-
fuel control. As the power increases, so does the
vents flameout from armament gas ingested by
