Robinson R22 BETA N2566W

The purpose of the flight was to conduct an introductory flight to a potential student. The 6,271 hour certified flight instructor (CFI) demonstrated the preflight inspection step by step following the checklist for the prospective accident student; the inspection included examination of the swash plate assembly for security of the flight control push/pull tubes. No preflight inspection discrepancies were later reported by the accident student. The engine was started, and the flight departed to the west climbing to 500 feet msl, then descended to 300 feet. The student reported that while flying straight and level at 60 knots while he was looking outside, the helicopter banked left and nose down, "... making it impossible for the instructor to control the aircraft." The CFI commented several times "what happened", and attempted to recover from the left and nose down attitude but was unable. The CFI moved the cyclic control in an attempt to recover, but due to his (student's) confusion, could not recall what position he was moving it to. The student perceived the helicopter impacted the ground first with the left skid. The student did not notice any change in engine sound from the time of takeoff to the moment the helicopter banked left. Postaccident examination of the helicopter revealed the left forward push/pull tube was not connected to the swashplate assembly; the lug was not fractured. The rod-end and securing hardware of the left push/pull tube was not located. The securing hardware which secures the aft push/pull rod to the swashplate assembly was found to be loose; the threads of the bolt did not extend beyond the end of the nut and a palnut was not in position. NTSB examination of the swashplate assembly revealed no elongation of the hole of the left forward lug; linear impressions on the interior surface were consistent with the threads of the bolt. The impressions on the interior surface of the left forward lug were located in the area were the bolt shank is located. Four days before the accident, tracking and balancing of the main rotor was accomplished. The bracket used during the tracking procedure was installed to the left and aft lugs of the swashplate assembly, contrary to the procedure specified in the maintenance manual. The mechanic who performed the work could not recall if he used a new metal self locking nut when reinstalling the push/pull rods. Robinson Helicopter Company personnel reported that "...if either of the forward push/pull tubes were to become disconnected at the lower swashplate, it is assumed that the helicopter would be uncontrollable." Postaccident review of the operator's facility and several helicopters by NTSB and FAA personnel revealed several had the push/pull tubes installed on the incorrect side of the lugs at the swashplate assembly, and the securing hardware was incorrectly installed. Additionally, FAA personnel noted discrepancies with the maintenance records. One of the helicopters which had the push/pull tubes incorrectly installed, had been previously inspected on five separate occasions by one of the mechanics who had performed the last tracking and balancing of the main rotor on the accident helicopter. Installation of the bracket used during the last main rotor tracking and balancing required the removal of the bolts at the left and aft lugs of the swash plate. Proper installation of the bracket requires removal of hardware that secures 2 of 3 flight control push/pull tubes to the swashplate.

Quoted verbatim from the NTSB record.