King Air C90GTi, Pilot Training Manual

Page: 155 / 557

IGNITERS
T h e e n g i n e s t a r t sw i t c h e s a r e l o c a t e d o n
the pilot’s left subpanel (Figure 7-11). This
s u b p a n e l c o n t a i n s t h e I G N I T I O N A N D
ENGINE START switches and ENG AUTO
IGNITION switches.
T h e I G N I T I O N A N D E N G I N E S TA RT
switches have three positions: ON, OFF, and
STARTER ONLY. The ON position is lever-
locked and activates both the star ter and ig-
niters. The STARTER ONLY position is a
m o m e n t a r y h o l d - d ow n p o s i t i o n o f t h e
s p r i n g - l o a d e d - t o - c e n t e r O F F p o s i t i o n . I t
provides for motoring only to clear the en-
gine of unbur ned fuel. With the switch in
this position, there is no ignition.
The combustion chamber has two spark-type
igniters to provide positive ignition during
engine start. While the engine is equipped
with two igniters, it will start with only one.
The system is designed so that if one igniter
is open or shorted, the remaining igniter will
c o n t i n u e t o f u n c t i o n . O n c e t h e e n g i n e i s
started, the igniters are de-energized, since
the combustion is self-sustaining.
The ignition system features an automatic
b a c k u p f u n c t i o n f o r e m e r g e n c i e s . T h i s
backup system is called “autoignition.” The
ENG AUTO IGNITION switches should be
m ove d t o t h e A R M p o s i t i o n j u s t p r i o r t o
t a ke o ff . I f e n g i n e t o rq u e f a l l s b e l ow a p -
proximately 400 ft-lb, the igniter will au-
tomatically energize, attempting to restar t
the engine. The IGNITION ON annunciator
will be illuminated.
The spark ignition provides the engine with
an ignition system capable of quick light-ups
over a wide temperature range. The system
consists of an airframe-mounted ignition ex-
citer, two individual high-tension cable as-
s e m b l i e s , a n d t wo s p a r k i g n i t e r s . I t i s
energized from the aircraft nominal 28-VDC
supply and will operate in the 9- to 30-volt
range. The igniter control box produces up to
3,500 volts. The ignition exciter is energized
only during the engine starting sequence and
emergencies to initiate combustion in the
combustion chamber.
ACCESSORY SECTION
Most of the engine-driven accessories, ex-
cept the propeller gover nors and propeller
tach generator, are mounted on the acces-
sor y gearbox located at the rear of the en-
g i n e ( F i g u r e 7 - 1 2 ) . T h e a c c e s s o r i e s a r e
driven from the compressor shaft through a
coupling shaft.
KING AIR C90GTi/C90GTx PILOT TRAINING MANUAL
7-10
FOR TRAINING PURPOSES ONLY
7
POWERPLANT
POWER TURBINE
STATOR HOUSING
COMBUSTION
CHAMBER
COOLING AIR
PASSAGE
GAS GENERATOR
CASE
SPARK IGNITER
Figure 7-11. Engine Start and Ignition
Switches