FL CDL Combination cheat sheet

Combination Vehicles (CDL Class A)

• Fifth wheel: the locking jaws must fully close around the kingpin shank with the release handle in the locked position; a gap between the jaws and kingpin means the coupling is not secure.

• Tug test: after coupling, pull forward gently with the trailer brakes set (or hold the trailer with the tractor brake) to confirm the trailer does not move; then check the gap visually and verify the safety latch is over the handle.

• Air lines: connect the emergency (service) line first and the service line second, or color-coded blue-to-blue and red-to-red; after connection, check that the lines are not crossed, kinked, or dragging on the frame.

• Landing gear: fully raised before travel, with the crank secured and the handle stowed; a low gear handle can strike the ground or a railroad crossing and cause a jackknife.

• Trailer air supply (red) knob: push in to charge the trailer system; it pops out automatically when trailer pressure drops below about 45 psi, applying the trailer spring brakes.

• Tractor protection valve: closes automatically on a breakaway or major leak, sealing the tractor's air supply so the tractor brakes remain usable; the trailer emergency line then vents and sets the trailer brakes.

• Pintle hook coupling: the latch must be closed over the drawbar eye and secured with a safety pin or latch; check the eye for wear and confirm the safety chains are crossed and attached.

• Rearward amplification: the last trailer in a multi-trailer combination swings wider than the tractor, so check mirrors and swing wide on turns; the longer the combination, the greater the off-tracking of the rear wheels.

• Brake check: with the engine running and system charged, release the parking brake, apply the foot brake, and hold; watch for air loss greater than 3 psi in one minute (single vehicle) - a leak signals a defect requiring repair before dispatch.