exhaust plumbing. These valves control the flow of hot
exhaust gasses to the inlet air lip assemblies.
exchanger, located in the engine accessory case,
operates continuously and automatically to heat the fuel
sufficiently to prevent ice from collecting in the fuel
2-21.-ENGINE FUEL CONTROL SYSTEM.
a. Description. The basic fuel system for each
engine consists of an engine driven fuel pump, a fuel
control unit, a fuel flow divider, a dual fuel manifold,
fourteen fuel nozzles, and a purge system. The fuel
purge system forces residual fuel from the manifolds to
the combustion chamber where it is consumed.
b. Fuel Control Unit. The fuel control unit is
mounted on the accessory case of the engine. The unit
is a hydro-pneumatic metering device which determines
the proper fuel flow schedule required for the engine to
produce the amount of power requested by the relative
position of the associated POWER lever. The control of
developed engine power is accomplished by adjusting
the engine gas generator (N1) speed. N,
controlled by varying the amount of fuel injected into the
combustion chamber through the fuel nozzles. Engine
shutdown is accomplished by moving the appropriate
CONDITION lever to the full aft FUEL CUTOFF position,
which shuts off the fuel supply.
2-22. POWER LEVERS.
Moving the POWER lever below the flight idle
gate without the associated engine running
may result in damage to the reverse
The two POWER levers are located on the
control pedestal (fig. 2-14), and are placarded POWER.
These levers regulate power in the reverse, idle, and
forward ranges, operating so that forward movement
increases engine power. Power control is accomplished
through adjustment of the N1 speed governor in the fuel
control unit. Power is increased when N1 RPM is
increased. The POWER levers also control propeller
reverse pitch. Distinct movement (pulling up and then
aft on the POWER lever) by the pilot is required for
operation in the ground fine and reverse ranges.
(increase), supplemented by an arrow pointing forward.
Lever travel range is marked IDLE, LIFT, GROUND
FINE, LIFT, and REVERSE. A placard below the lever
slots reads: CAUTION - REVERSE ONLY WITH
2-23. CONDITION LEVERS.
The two CONDITION levers are located on the
control pedestal (fig. 2-14). Each lever starts and stops
the fuel supply, and controls the idle speed for its
respective engine. The levers have three placarded
positions: FUEL CUTOFF, LOW IDLE, and HIGH IDLE.
In the FUEL CUTOFF position, the CONDITION lever
controls the cutoff function of its engine-mounted fuel
control unit. From LOW IDLE to HIGH IDLE, they
control the governors of the fuel control units to establish
minimum fuel flow levels. LOW IDLE position sets the
fuel flow rate to attain 60 to 62% minimum N1, and HIGH
IDLE position sets the rate to attain 71 to 73% minimum
N1 The POWER lever for the corresponding engine can
select N1 from the respective idle setting, up to maximum
power. An increase in low idle N, will be experienced at
high field elevation.
2-24. FRICTION LOCK KNOBS.
Friction drag of the engine and propeller control
levers is adjusted, as applicable, by four friction lock
knobs. The friction lock knobs, placarded FRICTION
LOCK, are located on the control pedestal (fig. 2-14).
One knob is below the propeller levers, one is below the
CONDITION levers, and two are below the POWER
levers. When a knob is rotated clockwise, friction is
increased, opposing movement of the affected lever as
set by the pilot. Counterclockwise rotation of the knob
will decrease friction, thus permitting free and easy lever
2-25. ENGINE FIRE DETECTION SYSTEM.
a. Description. A fire detection system
(fig. 2-16) is installed to provide an immediate warning in
the event of a fire or overtemperature in each engine
compartment. The main element of the system is a
temperature sensing tube, which is routed continuously
throughout each engine compartment and terminates in
a responder unit. The responder unit is mounted in the
accessory area on the upper left hand engine mount
truss, just forward of the engine firewall. The responder
unit contains two sets of contacts: a set of integrity
switch contacts, for continuity test functions of the fire
detection circuitry; and a set of alarm switch contacts,
which complete the circuit to activate the fire warning
system when the detector (sensor tubing) senses an
overtemperature condition in critical areas around the
engine. The detector is dual functioning and responds to
overall "average" temperature, or a highly localized
"discrete" temperature, caused by flames or hot gases.
Both the average and discrete temperatures are preset,
and cannot be adjusted in the field.
The sensor tubing consists of an outer tube that
is filled with an inert gas, and an inner core that is filled
with an active gas. The gases within the tube form a
pressure barrier that keeps the contacts of the responder