The potentiometer terminals and cable entry areas shall be sealed off
22.214.171.124.6 Moisture protection.
from moisture. To reduce the effect of any moisture which might get to the potentiometers, the resistance of
the potentiometers shall be 5K OHMS minimum.
Brakes. Stopping of aircraft while towing is totally dependent on the tractor brake system.
Aircraft brakes are used only in emergency situations.
126.96.36.199 Air Brake System.
188.8.131.52.1 Service brakes. The vehicle shall be equipped with full air brakes on all wheels. Brakes shall
be of either drum or disc type. Drums shall have flanges or ribbing to prevent distortion and shall be
demountable without disturbing the wheel bearings. A commercial off-the-shelf air dryer and necessary
associated parts shall be added to the pneumatic system to eliminate excessive moisture and oil, thus
increasing the life of the air brake components. It shall use desiccant for the final absorption process and
shall be installed in the discharge line between the compressor and the first reservoir. A heater and
thermostat assembly shall be provided with the air dryer to preclude freeze up when used in severe winter
conditions. A drain shall be provided on each air reservoir and shall be readily accessible for service.
The service brakes shall be capable of stopping 175,000 pound towed load on a dry level surface (concrete or
asphalt) from 5 MPH in no more than 18 feet and from 5 MPH on a three percent descending slope in no
more than 33 feet. In meeting this requirement, the brakes shall not be allowed to lock up; however, it
should be possible to lock up the brakes with the maximum application of the service brake pedal. The
brakes shall be of the all wheel type with split circuits so that failure of one circuit shall not cause total
service brake failure.
Physical arrangement of the tractor brake pedal and accelerator shall allow for sufficient
clearance for heavy arctic gear.
b. The unloaded tractor shall not exceed 10 feet of stopping distance while traveling at 15
The parking brake shall be capable of holding the unloaded vehicle on a 25
184.108.40.206.2 Parking brake.
percent slope. Physical location of the brake control shall be within easy reach of the operator. The brake
shall be of the spring applied type and shall be located on the rear wheels only.
220.127.116.11.3 Brake system safety devices.
The brake system shall have low air pressure audible and
visual warning devices.
18.104.22.168 Hydraulic Brake System.
When specified (see 6.2) a hydraulic brake system shall be
The brake lines (including the hydraulic lines to the motor in a hydrostatic
22.214.171.124.1 Brake System.
system) shall be securely anchored to the chassis and protected from damage. Brake lines shall not be
copper or aluminum tubing. Brake lines shall be readily detachable at their axle (or motor, in the case of a
hydrostatic drive system) ends. Metal protective looms shall be provided at each point where lines pass
through metal members, except where a through-frame connector is provided. Connections on brake lines
shall be free of 90 fittings and other restrictions that may cause delays in braking response time.
Operation of the service brakes shall not result in evidence of excessive fading as governed by SAE J992B.
The brake system will be functionally compatible with the towed vehicle brake system. The towing
vehicle should not add to yaw, sway, skid, tip, tilt, or jackknife under maximum braking conditions.
126.96.36.199.2 Service and Parking Brakes. The service brakes shall stop the tractor within 10 feet from 15
MPH. The parking brake shall hold the tractor facing up or down a 25 percent grade. The parking brake
shall be fully independent of the service brake.
The service brakes shall be capable of stopping a 175,000 towed load on a dry
188.8.131.52.3 Service Brakes.
level surface at 5 MPH in no more than 18 feet. The stopping distance on a three percent slope at 5 MPH
shall not exceed 33 feet. In meeting this requirement, the brakes shall not be allowed to lock-up; however,