1-7. Location and Description of Major Components (cont'd)
9. Compressed air supply
Towing vehicle is equipped with an air compressor,
air reservoir, governor for controlling air pressure,
air gage and safety valve.
Air lines, intervehicular air hoses (1), air couplings
and shutoff valves transmit compressed air to semitrailer
brake system through gladhands (2).
10. Service air line
Service air line extends from gladhand marked SERVICE to top of the relay valves and the ratio
relay valve. It transmits changes in air pressure which cause relay valves to function These
changes result from brake being applied in towing vehicle.
11. Emergency air line
Emergency air line extends from gladhand marked EMERGENCY to top of ratio relay valve. It
transmits compressed air to fill air reservoirs and to maintain proper air pressure under control of
the relay valves.
12. Internal brake mechanism
Each brake mechanism is located within the brake drum.
Each one has two brake shoes fitted with brake linings.
S cam is used to expand brake shoes. Springs aid in retracting
k. Leveling Jacks
Leveling jacks are provided on M129A4 Registration Numbers NX0QV
through NX0RC9 and XM1063 only.
Is provided at each rear corner of dolly.
Consists of housing assembly (1), screw (2), drop leg assembly (3),
braces (4) and crank (5). Is used to level and help stabilize semitrailer.
Leveling jack is heavy. Two persons are required to
remove/install leveling jack.
Is used as aircraft loading jack in aircraft loading procedure.