LEC Brake Systems & Safety 3 — Questions and Answers
Question 1: What does a 'penalty brake application' automatically enforce on a locomotive?
- A minimum service brake application until reset by a supervisor
- A full emergency brake application that cannot be overridden by the engineer (Correct answer)
- Shutdown of the locomotive prime mover only
- Automatic alerting of the dispatcher without applying brakes
Correct answer: A full emergency brake application that cannot be overridden by the engineer
A penalty brake application triggers a full emergency brake application that the engineer cannot override, used by safety systems like PTC and alerters.
Question 2: What is the purpose of retainer valves on freight cars, and when would a locomotive engineer request their use?
- To increase brake pipe pressure above 90 psi on steep grades
- To hold some brake cylinder pressure during brake releases on descending grades (Correct answer)
- To prevent brake pipe overcharge on level territory
- To bypass defective AB valves during emergency situations
Correct answer: To hold some brake cylinder pressure during brake releases on descending grades
Retainer valves hold a portion of brake cylinder pressure during the release cycle, helping control train speed on long descending grades.
Question 3: Which type of brake shoe provides a higher friction coefficient at low speeds but tends to overheat on long downgrades?
- High-friction composition (HFC) shoes
- Cast iron shoes (Correct answer)
- Low-friction synthetic shoes
- Ceramic-composite shoes
Correct answer: Cast iron shoes
Cast iron brake shoes provide excellent friction at low speeds but are prone to overheating on sustained downgrades, which can cause wheel damage.
Question 4: What is 'brake shoe squeeze-out,' and what does it indicate?
- Normal brake application where shoes contact the wheel uniformly
- Uneven brake shoe contact causing the shoe to slide partially off the wheel tread (Correct answer)
- Excessive brake cylinder pressure above 50 psi
- Air escaping from the brake hose coupling
Correct answer: Uneven brake shoe contact causing the shoe to slide partially off the wheel tread
Brake shoe squeeze-out occurs when misaligned or worn brake rigging causes the shoe to partially leave the wheel tread, indicating a rigging defect requiring inspection.
Question 5: A locomotive engineer notices the brake pipe pressure gauge drops steadily at 8 psi per minute with brakes released. What is the correct action?
- Continue operating but monitor the gauge closely
- Report the defect and remove the locomotive from service (Correct answer)
- Increase throttle to compensate for the reduced braking capability
- Apply the independent brake to offset the leakage
Correct answer: Report the defect and remove the locomotive from service
FRA regulations require that brake pipe leakage not exceed 5 psi per minute; a rate of 8 psi per minute indicates a defect requiring the locomotive to be removed from service.
Question 6: What is the effect of an 'overcharge' condition in the brake pipe?
- Brakes apply immediately due to excess pressure
- Brakes may release slowly or incompletely on cars with overcharged auxiliary reservoirs (Correct answer)
- The main reservoir pressure drops below minimum operating pressure
- Emergency brakes automatically apply on all cars in the train
Correct answer: Brakes may release slowly or incompletely on cars with overcharged auxiliary reservoirs
When the brake pipe is overcharged, auxiliary reservoirs may become overcharged too, causing slow or sluggish brake releases and potential control valve malfunction.
Question 7: During a pre-departure brake test, what condition must be verified before a train departs?
- Only the locomotive brakes need to be tested
- At least 85% of the cars must have operative brakes and brakes must apply and release properly (Correct answer)
- Brake pipe must be charged to exactly 100 psi
- All retainer valves must be set to the exhaust position
Correct answer: At least 85% of the cars must have operative brakes and brakes must apply and release properly
FRA regulations require that at least 85% of cars have operative brakes and that brakes properly apply and release before train departure.
LEC Brake Systems & Safety 3
What does a 'penalty brake application' automatically enforce on a locomotive?