During normal operation, how should the rear air-line shut-off valves be set in a doubles combination?
Correct answer: Lead trailer open; final trailer closed
Air must flow through intermediate units, while unused ends at the last trailer stay closed.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), 7.3 Inspecting Doubles and Triples — Double and Triple Trailers, printed 7-5 (physical PDF page 128) ↗
Which list identifies converter-dolly connections that must be checked?
Correct answer: Pintle connections, chains, air lines, light cords
All dolly connections must be latched, supported, connected, and undamaged.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), 7.3 Inspecting Doubles and Triples — converter-dolly connections, printed 7-5 (physical PDF page 128) ↗
How is emergency-line airflow verified at the back of a doubles rig?
Correct answer: Charge the system and briefly open the last trailer’s emergency shut-off to hear escaping air
Secure the rig with the tractor parking brake and/or wheel chocks, build normal pressure and push in the trailer-air-supply control. Briefly open and close the last emergency-line valve; escaping air shows supply reaches the rear. Test the service line separately with the hand control or service pedal applied, and close its valve afterward.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), 7.4.1 Additional Air Brake Checks — Check That Air Flows to All Trailers, printed 7-5 (physical PDF page 128) ↗
At approximately what pressure range does the trailer-air-supply control usually pop out during its test?
Correct answer: 20 to 45 psi
The exact value follows the manufacturer, but the handbook gives a usual 20-to-45-psi range.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), 7.4.1 Additional Air Brake Checks — Test Tractor Protection Valve, printed 7-5 (physical PDF page 128) ↗
On a combination equipped with a trailer hand control, how should the trailer service brakes be tested?
Correct answer: Move forward slowly and apply the trailer hand control to feel the brakes engage
At normal air pressure with parking brakes released, move forward slowly and apply the hand control, if equipped. Feel the trailer brakes engage. Use the foot pedal for normal braking, not the hand control.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), 7.4.1 Additional Air Brake Checks — Test Trailer Service Brakes, printed 7-5 (physical PDF page 128) ↗
A converter dolly has spring brakes. Which control does the handbook specify for releasing them to position the dolly safely?
Correct answer: The dolly parking-brake control
The procedure distinguishes dollies with spring brakes from those whose brakes are released by opening the tank petcock. Use the method for the actual equipment and secure it against unintended movement.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), 7.2.1 Position Converter Dolly in Front of Second Trailer, printed 7-2 (physical PDF page 125) ↗
Before backing a converter dolly under the rear trailer, how should the dolly be aligned?
Correct answer: In line with the rear trailer's kingpin
Place the dolly in line with the kingpin before coupling. Equipment-specific procedures still apply.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), 7.2.1 Position Converter Dolly in Front of Second Trailer, printed 7-2 (physical PDF page 125) ↗
What location and alignment should be chosen before uncoupling twin trailers?
Correct answer: A straight rig on firm, level ground
The rear trailer and dolly need stable support. Park straight on firm, level ground and apply the parking brakes before the uncoupling steps.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), 7.2.2 Uncoupling Twin Trailers — Uncouple Rear Trailer, printed 7-3 (physical PDF page 126) ↗
Before pulling the dolly out from under the rear semitrailer, what should be done with that trailer's landing gear?
Correct answer: Lower it enough to remove some weight from the dolly
The trailer must be supported before the dolly is pulled away. The procedure calls for lowering its landing gear enough to relieve some weight on the dolly.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), 7.2.2 Uncoupling Twin Trailers — Uncouple Rear Trailer, printed 7-3 (physical PDF page 126) ↗
While separating the rear trailer of doubles, what should happen to the shut-off valves at the rear of the lead trailer before disconnecting dolly lines?
Correct answer: Close them, including dolly shut-offs if equipped
These valves are closed for this uncoupling step. That differs from their open position during normal operation of the connected rig.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), 7.2.2 Uncoupling Twin Trailers — Uncouple Rear Trailer, printed 7-3 (physical PDF page 126) ↗
The dolly is clear of the rear trailer and its support is lowered. Before releasing the front pintle hook, what prevents the dolly from rolling?
Correct answer: Its applied spring brakes or wheel chocks
Apply the converter gear's spring brakes or chock its wheels before releasing the pintle hook. Never release that hook while the dolly remains under the rear trailer.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), 7.2.2 Uncoupling Twin Trailers — Uncouple Converter Dolly, printed 7-3 (physical PDF page 126) ↗
A spare tire is carried on the converter dolly. What specific inspection is needed?
Correct answer: Make sure the spare is secured
A spare carried on converter gear must be secured. It is an additional item beyond checking the running tires.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), 7.3.1 Additional Checks — Double and Triple Trailers, printed 7-5 (physical PDF page 128) ↗
A coupled doubles rig is ready to move. Which landing-gear condition is required?
Correct answer: Fully raised, sound gear with crank handles secured
Inspect the landing gear for damage and complete retraction, secure the crank, and check powered gear for air or hydraulic leaks.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), 7.3.1 Additional Checks — Landing Gear, printed 7-5 (physical PDF page 128) ↗
During a secured rear service-line airflow test, what must supply service pressure before the final valve is briefly opened?
Correct answer: An applied trailer handbrake or service-brake pedal
The service-line test assumes the hand control or service pedal is applied. Close the rear valve after checking; follow a safe, secured test arrangement.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), 7.4.1 Check That Air Flows to All Trailers, printed 7-5 (physical PDF page 128) ↗
A properly set up rear airflow test produces no escaping air. What should be checked before the rig is driven?
Correct answer: Whether intermediate trailer and dolly shut-off valves are open
Air must reach the rear for all trailer brakes to work. Check the intermediate valves and correct the problem rather than drive with an unverified rear brake supply.
Source: Pennsylvania Commercial Driver's License Manual PUB 223 (6-26), 7.4.1 Check That Air Flows to All Trailers, printed 7-5 (physical PDF page 128) ↗
