CDL · Inspection

When inspecting a doubles combination, why must the driver check the converter dolly's landing legs or jacks?

Correct answer

During transport, landing legs must be fully retracted and secured — legs that extend down during travel create a road hazard, can contact the road surface and cause the combination to swerve or become unstable, and can be destroyed along with surrounding vehicle components

  1. A Landing legs only need inspection when the dolly is parked separately
  2. B During transport, landing legs must be fully retracted and secured — legs that extend down during travel create a road hazard, can contact the road surface and cause the combination to swerve or become unstable, and can be destroyed along with surrounding vehicle components
  3. C Landing legs are not part of the pre-trip inspection
  4. D Only check if the road surface is rough

Why this is the answer

CONVERTER DOLLY LANDING LEGS are used to support the dolly when it is parked detached from any trailer. During transport they must be in the FULLY RETRACTED AND SECURED position. PRE-TRIP VERIFICATION: Physically check that the landing legs are cranked fully up — not just nearly up; verify the crank handle is stored or secured (a loose crank can fall and create a road hazard); verify any locking pin or latch that secures the legs in the retracted position is engaged; CONSEQUENCES OF IMPROPER RETRACTION: If a landing leg is partially down or comes loose during transport: at highway speed, the leg contacts the road surface — this creates immediate severe swerving as one side of the dolly is suddenly braked by road contact; the leg will be destroyed, and depending on the force and failure mode, can damage brake lines, air lines, electrical cables, or the dolly frame; the sudden force can cause the connection to fail and the rear trailer to partially separate; SIMILAR PRINCIPLE applies to trailer landing gear on the front of the semitrailers — both must be checked; COLD WEATHER NOTE: In freezing temperatures, landing leg crank mechanisms can freeze in a partially down position after the last parking; always verify they move freely and confirm full retraction before departure.
Source: FMCSA CDL Manual, Chapter 7, Doubles and Triples, Converter Dolly Inspection

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