Fire Apparatus Driver & Operator Practice Exam Vocabulary

A collection of key vocabulary terms and definitions derived from the Fire Apparatus Driver & Operator Fifth Edition exam prep transcript, covering maintenance, hydraulics, driving skills, and pump operations.

Maintenance

The process of keeping fire apparatus in a state of usefulness or readiness.

Steering wheel play

The movement of the steering wheel before it begins to turn the wheels, which should be no more than approximately $10\,degrees$ in either direction.

Foam proportioner

A device that injects the correct amount of foam concentrate into the water stream to create a foam solution.

Volute

The spiral chamber of a centrifugal pump in which the velocity given to water by the impeller is converted into pressure.

Net pump discharge pressure

The difference between the pump discharge pressure and the incoming pressure from the hydrant or supply source.

Water hammer

A sudden stoppage of water moving through a hose or pipe that results in a surge of internal pressure.

Gross Vehicle Weight Rating (GVWR)

The maximum weight at which a vehicle can be safely operated on roadways, including the weight of the chassis, body, and load.

Angle of approach

The angle formed by level ground and a line from the point where the front tires touch the ground to the lowest projection at the front of the apparatus.

Reverse lay

A method of hose deployment where the hose is laid from the fire scene to the water source (hydrant).

Forward lay

A method of hose deployment where the hose is laid from the water source (hydrant) to the fire scene.

Cavitation

A condition in a pump where pressure drops below vapor pressure, causing air bubbles to form and collapse; often characterized by a rattling noise described as "pumping gravel."

Pitot tube

A device used with a gauge to determine the flow pressure at a discharge opening, such as a smooth bore nozzle.

Level I staging

A staging procedure used in the initial response to a fire or incident involving more than one responding company.

Level II staging

A staging procedure used when a large number of emergency vehicles, including mutual aid, are responding to the same incident.

Power Take-Off (PTO)

A system that enables a fire apparatus to move and discharge water at the same time.

Serpentine Course

A driving skill exercise designed to simulate maneuvering an apparatus around parked and stopped vehicles.

Residual pressure

The pressure remaining in the water distribution system once water has begun flowing from a hydrant or discharge.

Static pressure

The pressure in the system when no water is flowing, representing the potential energy.

Encrustation

Corrosion or mineral deposits on the interior surface of the piping and components of a water distribution system.

Jacknifing

A condition involving articulated vehicles where the trailer and cab form an angle of less than $90\,degrees$ to one another.

Angle of departure

The angle formed by level ground and a line from where the rear tires touch the ground to the lowest projection at the rear of the apparatus.

Impeller

The major component of a centrifugal pump that provides velocity to the water.

Flow meter

A device that provides a reading of the water flow in gallons per minute ($gpm$).

Compound gauge

A gauge designed to read both positive pressure and negative pressure/vacuum.

Dry hydrant

A non-pressurized pipe system that provides a connection for drafting water from a static source like a lake or river.

Standard Fog Nozzle Pressure

The recommended operating pressure for a standard fog nozzle, which is typically $00\,psi$.

Solid Bore Handline Pressure

The recommended nozzle pressure for $2-1/2\,inch$ handlines with solid bore tips, which is $50\,psi$.