Free EVT ARFF A-2 practice test: Chassis & Components

Free EVT ARFF A-2 practice test: 10 questions

Questions from our AR2 bank, written to EVTCC's learning objectives and the 2024 NFPA 1900 and 1910. Tap an answer to see if you're right and why, or switch to Timed for the real test's pace. Every answer is below each question.

1. What is the primary reason ARFF vehicles use a heavy-duty, purpose-built chassis rather than a standard commercial truck chassis?

   ATo support large agent tank loads while meeting rapid off-road acceleration and response requirements BTo hold the vehicle's cost down, since a purpose-built frame is the cheaper option CTo allow standard passenger-car tires and wheels to be fitted in place of large sizes DTo carry the agent load on the frame rails alone so no suspension system is needed
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   Answer: A. To support large agent tank loads while meeting rapid off-road acceleration and response requirements

   ARFF vehicles must carry heavy water and foam loads yet still accelerate rapidly on and off pavement, which requires a specialized high-strength chassis and driveline.

   • B: A low-volume purpose-built chassis costs more than a standard commercial one.
   • C: Passenger-car tires cannot carry the weight or handle the terrain involved.
   • D: Wheel travel is required to keep the tires on rough ground; suspension remains.

2. On a 6x6 ARFF vehicle, the transfer case primarily serves to:

   AIncrease the volume of foam concentrate the tank can hold BTake over the transmission's job of providing the gear ratios CDistribute engine power to both the front and rear driving axles DCool the engine while the pump is running at high output
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   Answer: C. Distribute engine power to both the front and rear driving axles

   The transfer case splits driveline power from the transmission to the front and rear axles to provide all-wheel-drive traction.

   • A: The transfer case is a driveline gearbox with no connection to the agent tanks.
   • B: It takes its input from the transmission, which still provides the gear ratios.
   • D: It is a sealed gearbox with no coolant or airflow path to the engine.

3. Locking differentials are provided on ARFF vehicles primarily to:

   AMaintain traction when one wheel loses grip on soft or uneven terrain BImprove highway fuel economy by cutting driveline losses in the axle CReduce tire wear in turns by evening out the load between the wheels DAllow the drive wheels to freewheel on downgrades to save the brakes
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   Answer: A. Maintain traction when one wheel loses grip on soft or uneven terrain

   A locking differential forces both wheels on an axle to turn together, maintaining traction when one wheel is on a low-grip surface such as mud or grass.

   • B: A lock is engaged at low speed off pavement and adds no highway efficiency.
   • C: Forcing both wheels to the same speed scrubs the tires in a turn.
   • D: Nothing in a differential disconnects drive to let the wheels coast free.

4. Pump-and-roll capability on an ARFF vehicle refers to the ability to:

   ARoll the vehicle without starting the engine BDischarge firefighting agent while the vehicle is moving CPump fuel from one tank to another DInflate the tires while driving
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   Answer: B. Discharge firefighting agent while the vehicle is moving

   Pump-and-roll lets the vehicle apply agent to a fire while still driving, which is essential for advancing on a moving or spreading fuel fire.

   • A: Pump-and-roll concerns agent discharge, not moving the vehicle unpowered.
   • C: It refers to firefighting agent, not fuel transfer.
   • D: Tire inflation systems are separate from pump-and-roll.

5. On many ARFF vehicles, the fire pump is driven by a:

   APower take-off (PTO) or split-shaft arrangement driven by the vehicle engine or transmission BSeparate electric motor run from the vehicle batteries with no engine input CWind-up spring mechanism wound at the station and released to spin the pump DBelt drive taken off the alternator pulley so the pump turns with the charging system
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   Answer: A. Power take-off (PTO) or split-shaft arrangement driven by the vehicle engine or transmission

   ARFF fire pumps are driven off the chassis engine, through either a PTO or a split-shaft (midship) transmission, which is what lets one engine make full pump flow. The two are not interchangeable for pump-and-roll: a hot-shiftable PTO or power divider keeps the drive axle turning while the pump runs, which is how an ARFF rig puts foam down on the move, whereas a split-shaft drive commits the driveline to the pump in pump gear, so the apparatus pumps stationary with the parking brake set.

   • B: The battery bank cannot sustain the continuous output a fire pump demands.
   • C: A stored-spring drive has no continuing source of power for sustained flow.
   • D: The alternator is itself engine-driven and makes current, not pump shaft power.

6. Because of their high gross weight, ARFF vehicles are equipped with:

   AManual hydraulic drum brakes only BLarge-capacity air brake systems CCable-operated parking brakes only DNo service brakes, to save weight
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   Answer: B. Large-capacity air brake systems

   The heavy gross vehicle weight of ARFF vehicles requires robust, high-capacity air brake systems for adequate stopping power.

   • A: Manual hydraulic brakes alone are inadequate for these weights.
   • C: A cable parking brake cannot serve as the primary service brake.
   • D: Service brakes are mandatory, not omitted.

7. ARFF vehicles typically use high-output alternators and multiple batteries because:

   AThey are never left idling long enough for the charging system to fall behind the loads BThey carry almost no electrical loads of their own, so the system only has to crank the engine CThey draw all of their electrical power from solar charging rather than the engine DThey carry heavy electrical loads such as warning lights, pumps, and control systems, often at low road speed
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   Answer: D. They carry heavy electrical loads such as warning lights, pumps, and control systems, often at low road speed

   The large number of electrical loads combined with prolonged low-speed and idle operation demands high-capacity charging and battery capacity to keep the system supplied.

   • A: ARFF vehicles accumulate long idle hours, which is when charging output is lowest.
   • B: High-output alternators and multiple batteries exist to feed a large connected load.
   • C: A high-output alternator is engine-driven charging, not solar.

8. Large flotation or off-road tires are fitted to ARFF vehicles mainly to:

   AReduce the vehicle's overall height and lower its center of gravity BEliminate the need for all-wheel drive by providing grip at every wheel CAllow higher inflation pressures to be run, giving a harsher ride DSpread the vehicle's weight and maintain mobility over soft ground off the runway
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   Answer: D. Spread the vehicle's weight and maintain mobility over soft ground off the runway

   Wide flotation tires distribute the heavy vehicle's weight over a larger area so it can travel across grass, mud, or sand alongside runways without sinking.

   • A: A taller tire raises the axle and body rather than lowering the vehicle.
   • B: A tire footprint cannot deliver torque to a wheel the driveline does not turn.
   • C: Flotation off-road means lower pressures, not higher ones.

9. For a low-mileage ARFF vehicle, engine oil and other fluids should be changed:

   AOn a time or engine-hours basis, because fluids degrade with age and idle hours even at low mileage BOnly after the odometer reaches the mileage interval, since miles measure the wear CNever, because a vehicle that is rarely driven leaves its fluids essentially unused DOnly when the check-engine light appears, using that warning as the interval
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   Answer: A. On a time or engine-hours basis, because fluids degrade with age and idle hours even at low mileage

   ARFF vehicles accrue few miles but many idle hours and calendar time, so fluids must be serviced on a time or engine-hour basis rather than mileage alone.

   • B: The odometer barely moves while standby idle and pump hours accumulate.
   • C: A low-mileage vehicle is still started, idled and pumped, so its fluids age.
   • D: A warning lamp reports a detected fault, not fluid that has aged out.

10. A transmission or driveline retarder is used on ARFF vehicles to:

    AHelp slow the heavy vehicle and reduce service-brake wear and fade BRaise the vehicle's top speed by taking drag out of the driveline CCharge the batteries faster by generating current while slowing DBoost fire-pump discharge pressure by loading the driveline
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    Answer: A. Help slow the heavy vehicle and reduce service-brake wear and fade

    Retarders provide supplemental braking that reduces wear and heat buildup on the service brakes of heavy vehicles during deceleration.

    • B: A retarder absorbs driveline power to slow the vehicle; it cannot add speed.
    • C: A retarder turns motion into heat and is not part of the charging system.
    • D: Pump pressure comes from impeller speed, which the retarder does not drive.