AIRCRAFT AND SYSTEMS DESCRIPTION AND OPERATION
SECTION I. HELICOPTER
The CH-47D (fig. FO-1, 2-1-1 and 2-1-2) is a twin-turbine
engine, tandem rotor helicopter designed for transportation
of cargo, troops, and weapons during day, night, visual, and
instrument conditions. (Unless otherwise noted, numbers
refer to fig. FO-1.) The helicopter is powered by two
T55-L-712 or T55-GA-714A shaft-turbine engines (18) on
the aft fuselage. The engines simultaneously drive two tan-
dem three-bladed counterrotating rotors (13 and 19) through
engine transmissions (25), a combining transmission (16),
drive shafting (14), and reduction transmissions (12 and 23).
The forward transmission is on the forward pylon above the
cockpit (1). The aft transmission, the combining transmis-
sion, and drive shafting are in the aft cabin section and aft
pylon sections (3 and 4). Drive shafting from the combining
transmission to the forward transmission is housed in a
tunnel along top of the fuselage. When rotors are stationary,
a gas-turbine auxiliary power unit (22) drives a generator
and hydraulic pump to furnish hydraulic and electrical power.
Fuel is carried in pods on each side of the fuselage. The
helicopter is equipped with four non-retractable landing gear.
An entrance door (15) is at the forward right side of the cargo
compartment (2). At the rear of the cargo compartment is a
hydraulically powered loading ramp (26). The pilots seat (9)
and controls are at the right side of the cockpit; the copilots
seat (40) and controls are on the left side. See figure 2-1-3
for typical cockpit and controls.
2-1-2. Gross Weight.
The maximum gross weight of the CH-47D is 50,000
pounds. Chapters 5 and 6 provide additional weight informa-
2-1-3. Landing Gear System.
The landing gear system consists of four non-retractable
landing gears mounted on the fuselage pods. The forward
landing gears are a fixed-cantilever type and have twin
wheels. The aft landing gears are of the singlewheel, full-
swivel (360_) type which can be power centered and locked
in trailed position. In addition, the aft right landing gear can
be steered from the cockpit by using the steering control
knob on the console. Each landing gear has an individual
air-oil shock strut and is equipped with tube-type tires.
2-1-4. Landing Gear Proximity Switches.
Two proximity switches are installed, one on each aft
landing gear. Each switch is activated when its associated
shock strut is compressed during touchdown. The switches
improve ground handling by reducing pitch axis gain of the
AFCS, by canceling the longitudinal Control Position Trans-
ducer (CPT), therefore longitudinal stick input, to the Differ-
ential Airspeed Hold (DASH) actuators, and by driving both
longitudinal cyclic trim (LCT) actuators to the ground posi-
tion. In addition to the above functions, the switch on the right
aft landing gear, when activated, disables the flare dispenser
to prevent accidental flare release, and enables the hold
function of mode 4 transponder codes.
On helicopters equipped with GROUND CONTACT
indicating lights, activation of the proximity switches when
the associated shock strut is compressed will cause the
associated GROUND CONTACT indicating light on the
MAINTENANCE PANEL to illuminate.
Should either or both GROUND CONTACT
indicating lights remain illuminated after
lift-off to hover, the illuminated system(s)
DASH will not function properly in forward
flight. If both GROUND CONTACT indicat-
ing lights remain illuminated after lift-off,
the AUTO function of both cyclic trim sys-
tems will be inoperative and both LCT ac-
tuators will remain in the GND position.
Aft landing gear proximity switches are not actuated
in a water landing. As a result, DASH actuators will respond
to longitudinal stick motion, producing an apparent increase
in control sensitivity. Cyclic motion of + 3/4 inch from neutral,
if held, will drive DASH actuators hard over. If longitudi-
nal cyclic movement is required for taxing, set the AFCS
SYSTEM SEL switch to OFF.
2-1-5. Steering and Swivel Lock System.
The steering and swivel lock system consists of the power
steering control box with the STEERING CONTROL panel
on the center console, utility system pressure control
module, power steering actuator, power steering module,
swivel lock actuating cylinder, and the PWR STEER master
caution capsule. The STEERING CONTROL panel consists
of a three position SWIVEL switch and a steering control
knob. The SWIVEL switch controls operation of power
steering and swivel locks.