As the speed of the aircraft was too high for the undercarriage to be lowered while downwind, the pilot
waited until he was turning onto base leg before moving the undercarriage selector from the "UP" detent.
Partial flap was lowered while on the base leg and full flap during an intentional long final approach. This
approach had been chosen to enable the pilot to check on a suspected malfunctioning of the electrical trim
actuator. No final cockpit checks, as required by the Company Operations Manual, were made during the
approach. Some engine power was used throughout the approach and the landing gear warning horn did not
sound before the aircraft contacted the runway with the landing gear retracted. The undercarriage selector
lever was found in the "neutral" position and subsequent electrical tests of the undercarriage system proved
it to be serviceable.