How do you release DD3 safety actuator brakes?
- (a) Push in the yellow parking brake knob.
- (b) Press the brake pedal for 3–5 seconds.
- (c) Do both (a) and (b). ✓
- (d) Pump the brake pedal for 3–5 seconds.
Answer: C. (c) Do both (a) and (b).
Release them by pushing in the yellow parking brake knob and pressing the brake pedal—the do-both choice.
Why this is the answer
The handbook says pushing the dash control inward exhausts air from the parking diaphragm and releases the locking mechanism, letting the pushrod retract. It also says that if more than 4 p.s.i. has been lost from the parking reservoir, the brakes will not release, and a heavy service brake application must also be made so the pushrod moves slightly ahead and the locking mechanism can disengage. Doing both matches the bank answer. The passage does not give the 3–5 second timing.
Why the other answers are wrong
- A. (a) Push in the yellow parking brake knob. — Pushing in the yellow parking brake knob alone is not enough when pressure has been lost from the parking reservoir; the handbook says a heavy service brake application must also be made.
- B. (b) Press the brake pedal for 3–5 seconds. — A heavy brake pedal application alone does not push in the dash control, which the handbook describes as exhausting air from the parking diaphragm and releasing the locking mechanism.
- D. (d) Pump the brake pedal for 3–5 seconds. — The handbook describes a heavy service brake application, not pumping the brake pedal, and it pairs that application with pushing in the dash control.
Remember it
Two actions, not one: knob in and a firm pedal application together let the safety actuator release.