Normal Operating Procedures and Braking Technique
This domain tests how to use air brakes without overheating them, losing control, or wasting air pressure. The exam favors questions about downgrades, brake fade, and proper use of gears and engine braking.
Core rules
- Control speed before the grade. Select a low enough gear at the top; do not coast in neutral.
- Use snub braking. Apply the brakes firmly to reduce speed about 5–6 mph below your safe speed, release, let the drums cool, and repeat when speed returns. Avoid continuous light pressure.
- Do not fan the brakes. Rapid on-off pumping wastes air and does not improve cooling.
- Do not ride the brakes. Continuous application overheats drums and causes fade.
- Use engine braking and gearing to hold speed; service brakes supplement, not replace, engine control.
- Watch the gauge. Keep pressure in the normal range and stop if the low-pressure warning activates.
Worked example
A loaded truck approaches a long 6% downgrade with a 35 mph safe speed. The driver shifts to a lower gear at the top, lets the engine hold speed, and uses snub braking to drop to about 30 mph whenever speed reaches 35 mph. Continuous light braking would overheat the drums and risk fade.
Traps
- Relying on the parking brake to control speed downhill.
- Waiting until the grade begins to choose a gear.
- Pumping the pedal repeatedly and draining air pressure.
- Ignoring a rising speed trend until the brakes are already hot.
Key points
- Select the right gear before the downgrade.
- Use snub braking: firm application, release, repeat.
- Do not fan or ride the brakes.
- Engine braking and gearing control speed; brakes supplement.
- Stop if the low-pressure warning activates.