Using Air Brakes: Normal Stops, Emergency Stops, and Braking Technique
Domain 5 tests how to use air brakes: normal stops, emergency stops, and braking technique on grades. The exam wants controlled, progressive braking-not fanning or riding the pedal.
Technique
- Normal stop: plan ahead, brake early, use engine braking and downshifting.
- Apply progressive pressure; avoid slamming unless it is an emergency.
- On downgrades, select a safe gear before descent; use short applications, not continuous drag.
- Brake fade: overheating reduces friction; stop to cool, do not continue.
- Emergency: brake firmly and steer; with ABS, hold pressure; without ABS, controlled or stab braking may be needed.
- Wet brakes: use light applications to dry them.
Worked example
A loaded truck gains speed downhill because the driver stayed in a high gear and rode the brakes. Reasoning: continuous braking overheats drums and causes fade. The correct action is to downshift, use engine braking, and make controlled applications; if fade occurs, stop and cool.
Traps that cost marks
Pumping ABS brakes; fanning air brakes; riding the brake downhill; not downshifting before the grade; thinking engine braking replaces service brakes.