EQUIPMENT CHARACTERISTICS, CAPABILITIES, AND FEATURES (cont)
(7) Auxiliary Fuel System.
The auxiliary fuel system provides fuel and air lines which are installed in
each wing. Auxiliary fuel tanks can be jettisoned. Disconnect couplings are breakaway and self-sealing.
LOCATION AND DESCRIPTION OF MAJOR COMPONENTS
a. Fuel Storage System.
The fuel storage system (fig. 101) consists of the forward and aft fuel cells,
breakaway valves, a baffle/check valve, and the fuel sump drain assembly. Various fuel subsystems control fuel
flow operation which are described in detail in the following paragraphs.
(1) Forward Fuel Cell.
The forward fuel cell is located under the pilots station and supplies fuel to
engine 1 (left). The outer and inner layers are made of several layers of rubber-impregnated nylon. The
intermediate layer consists of uncured rubber which forms a sealant material. The uncured rubber reacts to fuel
whenever the fuel cell is punctured. This reaction causes the uncured rubber to swell and seal the hole. It is
surrounded on the bottom and sides by the helicopter skin, rigid foam, Kevlar liner, and backing boards. The rigid
foam is used to fill the voids between the bulkheads. The Kevlar liner is between the rigid foam and the backing
boards and gives the fuel cell additional ballistic protection. The backing boards, made of fiberglass, reduce the
possibility of fuel cell chafing. The forward fuel cell is secured in the helicopter fuselage by seven mounting pads
which are molded to the fuel cell. The mounting pads consist of the forward fuel cell access panel pad, gravity
filler port mount pad, pressure fuel inlet mount pad, fuel outlet mount pad, sump plate/drain valve mount pad, air
vent/pressure relief valve mounting pad, and the pilot valve mounting pad.
(2) Aft Fuel Cell.
The aft fuel cell, located aft of the ammunition bay, normally supplies fuel to engine 2
(right), the APU, and both engines during startup. If desired, either cell can supply both engines. The aft fuel cell is
secured in the helicopter fuselage by six mounting pads which are molded to the fuel cell. The mounting pads
consist of the boost pump mount pad, the air vent/pressure relief valve mount pad, the gravity filler port mount
pad, the pilot valve mount pad, the pressure fuel inlet mount pad, and the sump plate/drain valve mount pad.
(3) Breakaway Valves.
The breakaway valves, located in the upper left and right corners of the fuel
cells, reduce fire hazards by sealing the fuel cells and lines in the event of a high impact landing. They are dual
flapper-type breakaway valves that are normally open to permit fuel flow. In the event of valve displacement, the
valve separates allowing spring tension to force the piston out which allows the flapper to seal the valve. If this
happens, a yellow caution band becomes visible between the flange section and the connection assembly. If the
caution band is visible, the valve is no longer serviceable and must be replaced.
(4) Baffle/Check Valve.
The baffle/check valve, located inside the forward fuel cell, ensures that an
uninterrupted supply of fuel is supplied to the engines. During level or nose-up attitude, the double-flapper check
valve opens allowing fuel to flow between the forward and aft section of the forward fuel cell. When the fuel level
is below the baffle and the helicopter is in a nose low attitude, the check valve closes and traps fuel.
(5) Fuel Sump Drain Assembly.
The fuel sump drain assembly, located at the bottom of each fuel cell,
permits fuel sampling checks for contamination, water content and draining of the fuel cells. The fuel sump drain
assembly consists of a spring-loaded closed sump drain valve, a sump drain plunger, which when pushed, opens
the sump drain valve allowing fuel to drain. Releasing the pushbutton on the sump drain plunger allows the
spring-loaded drain valve to close, stopping fuel flow.