FRA Locomotive Engine Systems 2 — Questions and Answers
Question 1: What is the primary function of a locomotive's dynamic braking system?
- Convert kinetic energy into electrical energy dissipated as heat (Correct answer)
- Apply hydraulic pressure to wheel tread surfaces
- Engage spring-loaded brake shoes on the truck assemblies
- Reduce fuel injection to slow engine RPM
Correct answer: Convert kinetic energy into electrical energy dissipated as heat
Dynamic braking uses traction motors as generators, converting the locomotive's kinetic energy into electrical energy that is dissipated through grid resistors as heat.
Question 2: Which cooling system component is responsible for removing heat from engine coolant in a diesel-electric locomotive?
- Intercooler
- Radiator section of the cooling tower (Correct answer)
- Aftercooler
- Oil cooler
Correct answer: Radiator section of the cooling tower
The radiator section of the cooling tower transfers heat from the engine coolant to ambient air via fans, maintaining safe engine operating temperatures.
Question 3: What does a locomotive's load regulator primarily control?
- Fuel tank pressure
- Engine throttle position relative to generator load (Correct answer)
- Air compressor cut-in and cut-out pressure
- Wheel slip detection sensitivity
Correct answer: Engine throttle position relative to generator load
The load regulator maintains a balanced relationship between engine throttle position and generator electrical load to prevent engine lugging or overspeeding.
Question 4: In a two-stroke diesel locomotive engine, when does fuel injection occur?
- During the intake stroke only
- Near the top of the compression stroke (Correct answer)
- During the exhaust stroke
- At bottom dead center of the power stroke
Correct answer: Near the top of the compression stroke
Fuel is injected near top dead center of the compression stroke so combustion pressure forces the piston downward during the power event.
Question 5: What hazard is associated with high crankcase pressure in a locomotive diesel engine?
- Reduced lubrication to main bearings
- Risk of crankcase explosion or fire (Correct answer)
- Excessive coolant consumption
- Turbocharger over-speed
Correct answer: Risk of crankcase explosion or fire
Excessive crankcase pressure can force oil mist past seals, and if ignited, can cause a crankcase explosion, which is why crankcase relief valves are required.
Question 6: A locomotive's engine oil pressure drops suddenly at full throttle. What is the FIRST action the operator should take?
- Increase throttle to raise oil pump speed
- Reduce throttle and prepare to shut down the engine (Correct answer)
- Switch to the auxiliary oil pump and continue at full power
- Apply independent brakes and continue monitoring
Correct answer: Reduce throttle and prepare to shut down the engine
Low oil pressure risks severe engine damage; the operator must reduce power immediately and prepare for engine shutdown per railroad operating rules.
Question 7: What is the purpose of the aftercooler (intercooler) on a turbocharged locomotive diesel engine?
- Cool exhaust gases before they enter the turbocharger
- Reduce the temperature of compressed intake air before it enters the cylinders (Correct answer)
- Regulate fuel temperature for better atomization
- Prevent coolant from boiling in the radiator
Correct answer: Reduce the temperature of compressed intake air before it enters the cylinders
The aftercooler cools the hot compressed air exiting the turbocharger, increasing air density so more oxygen is available for combustion and improving engine efficiency.
FRA Locomotive Engine Systems 2
What is the primary function of a locomotive's dynamic braking system?