CENTRAL TIRE INFLATION SYSTEM (CTIS) (M917A1 AND
M917A1 W/MCS) (Cont).
Four terrain settings may be selected: HIGHWAY (HWY); CROSS-
COUNTRY (X-C); SAND; EMERGENCY (EMER); and the RUN FLAT mode. If tire
damage is minimal (e.g., a minor puncture or slow leak), selecting RUN FLAT causes
CTIS to monitor tire pressure every fifteen seconds and re-inflate the tire.
Tire pressure can be manually checked and air added to tires
through a conventional air valve located at each wheel valve.
Major components of the CTIS are:
Electronic Control Unit
Contains microprocessor that controls the system and
operator selector panel.
Pneumatic Control Unit
Directs air pressure through air lines to the wheel valves,
according to ECU commands.
Separates moisture and filters impurities from compressed
air system before air enters the CTIS.
Acts as a brake priority switch by preventing CTIS from
consuming air until the air brake system has a minimum of
85 psi (586 kPa) of air.
Mounted at transfer case. Senses vehicle speed and sig-
nals the ECU to automatically inflate tires when vehicle
speed exceeds by 10 mph (16 kph) the top speed setting
for the selected mode.
Quick Release Valves
Allow air from PCU to inflate or vent air during deflation.
Isolate air pressure in tire during normal operation and for
tire removal. Air valve on wheel valve allows for inflation
and deflation using standard manual inflation equipment.