a single 5-ampere circuit breaker, placarded CHIP
b. Autoignition Lights. Two green press-protest
lights are positioned below the autoignition switches (fig.
2-31. Engine Ignition System.
2-7). Each light, although not placarded,
only with the switch directly above it and will illuminate
a. The basic ignition system consists of a current
when that switch is placed in the ARM position.
regulator unit, two igniter plugs, two shielded ignition
system is in a "ready condition".
If an ARMED
autoignition system changes from "ready condition" to an
START/STARTER ONLY switches. Activation of an
"operating condition" energizing the two igniter elements
IGNITION & ENG START switch will cause coils in the
in an engine, the green light will extinguish and a
respective igniter plugs to heat, igniting the fuel/air
corresponding yellow annunciator panel light will
mixture sprayed into the combustion chamber by the fuel
illuminate. The annunciator panel light is placarded L or
nozzles. The ignition system is activated for ground and
R IGN ON and indicates that the igniters are energized.
air starts, but is switched off after combustion light up.
The autoignition system is triggered from a "ready
b. One three-position toggle switch for each engine
condition" to an "operating condition" when engine
torque drops below 12 PSI (350 to 450 ft-lb torque).
on the left subpanel, will initiate starter motoring and
Therefore, when an autoignition system is ARMED, the
ignition in the IGNITION & ENG START position, or will
igniters will be energized continuously during the time
motor the engine in the STARTER ONLY position (fig.
when an engine is operating at a level below 12 PSI
2-7). The switches are placarded LEFT AND RIGHT
(350 to 450 ft-lb torque). The autoignition lights are
designate the appropriate engine. The IGNITION &
protected by 7.5-ampere START CONT - LH and RH
ENG START switch position completes the starter circuit
for engine rotation, energizes the igniter plugs for fuel
combustion, and activates the IGN ON light on the
c. Ignition-On Indicators. The ignition on state is
annunciator panel. At center position the switch is OFF.
confirmed by an illuminated yellow function indicator on
Two 20-ampere circuit breakers on the copilot's circuit
the annunciator panel placarded L, or R IGN ON
breaker panel, placarded IGNITER - LH and RH, protect
ignition circuits. Two 7.5-ampere circuit breakers on the
right subpanel, placarded START CONT - LH and RH,
2-33. Engine Starter-Generators.
2-32. Autoignition System.
One starter-generator is mounted on each engine
accessory drive section. Each is able to function either
as a starter or as a generator. In starter function, a
If "armed", the autoignition system automatically
stabilized minimum of 22 volts DC is required to power
provides combustion re-ignition of either engine should
rotation. In generator function, each unit is capable of
accidental flameout occur. The system is not essential
250 amperes DC output. When the starting function is
to normal engine operation, but is used to reduce the
selected, the starter generator receives power through
possibility of power loss due to icing or other conditions.
the respective 7.5-ampere START CONT circuit
Each engine has a separate autoignition control switch,
breakers on the right subpanel from either the aircraft
a green press-to-test light and a yellow indicator on the
battery or an external power source.
annunciator panel. Autoignition is accomplished by
generating function is selected, the starter-generator
energizing the two igniter heating elements in each
provides electrical power to its respective bus. For
additional description of the starter generator system,
a. Autoignition Switches. Two switches placarded
ENG AUTOIGNITION, LEFT and RIGHT, with positions
2-34. Engine Instruments.
ARM and OFF, are located on the left subpanel
(fig. 2-7). ARM position initiates
a readiness mode for
Instruments which display engine conditions or state
the autoignition system of the corresponding engine.
of operation are discussed in the following paragraphs.
OFF position disarms the system. Each switch is
Engine instruments are located horizontally in the
protected by a corresponding START CONT, LH or RH
circuit breaker of 7.5-amperes on the right subpanel
Change 7 2-19