CENTRAL TIRE INFLATION SYSTEM (CTIS) OPERATION cont'd

TM 9-2320-386-10

1-21. CENTRAL TIRE INFLATION SYSTEM (CTIS) OPERATION

(Contd)

The CTIS is activated and deactivated with an ON/OFF button on the ECU. In

the event the unit is not deactivated prior to engine shutdown, it will automatically

activate when the engine is started again.

Terrain switches on the ECU are pressed by the operator for the terrain condi-

tions, which are identified as emergency, sand/mud/snow, cross-country, and high-

way. Once the terrain switch has been pressed for desired pressure setting, the air

system inflates and maintains all tires to the appropriate tire pressure correspon-

ding to a recommended vehicle speed. Provided operator does not experience over-

speed conditions, no additional operator inputs are required once presets have been

selected.

The air regulating system consists of a controller overspeed signal generator,

power manifold, and wheel valves. If the operator exceeds the recommended vehicle

speed in either emergency, sand/mud/snow, or cross-country modes, an overspeed

warning will activate, (flashing max speed display) alerting the operator of the over-

speed condition and to signal operator to either decrease vehicle speed or select a

higher tire pressure on the ECU. In the event the operator fails to slow down or

select a higher tire pressure in approximately one minute, the system will automati-

cally increase air pressure to the tires to the next higher tire pressure setting.

In the event of one or more small air leaks anywhere in the system, such as from a

tire puncture or leak at a connecting line, pressure can be maintained by pressing a

terrain switch on the control panel. When doing so the initial test pressure sequence

begins. If the air feeder lines cannot hold at least 6 psi (41 kPa) the controller display

will read FLAT in the upper right corner, indicating to the vehicle operator that a

large air leak, such as a damaged/disconnected air line or a flat tire, exists. When

FLAT is indicated, the vehicle operator may elect to call for assistance, or try to drive

to a repair center using the vehicle's run flat mode.

Should a particular tire or connecting line experience catastrophic failure or a

leak which exceeds the capacity of the compressor, the CTIS may be turned off,

allowing the wheel valves to keep each tire individually isolated. Additionally, the

damaged portion will remain isolated, as a safety measure, until it is repaired. A

priority pressure switch in the manifold monitors the pressure in the air reservoirs

and isolates the CTIS if this pressure drops below 75 psi (517 kPa). Minimum

requirement for the operation of priority systems (brakes, power steering assist,

horn) is less than 75 psi (517 kPa), so safe operation is assured. If the CTIS suffers com-

plete failure, the operator accesses a manual wheel valve at each wheel and inflates

each tire from an external air source. If tire pressure falls below 10 psi (69 kPa), CTIS

will not inflate tire. The CTIS should be deactivated during operation in extreme cold,

0 to -65F (-18 to -54C). Extremely cold temperatures can cause air seals located at

each wheel to fail.

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