CHATHAM – The June 2016 crash of a helicopter into Crow's Pond was the result of inadequate maintenance, exacerbated by an error in a maintenance log entry that delayed an overhaul beyond its mandatory timeframe, according to a report by the National Transportation Safety Board.
Had the error not been made, timely maintenance would likely have led to the overhaul of sections of the engine that failed.
Pilot John Ryan, 48, of Scituate, and passenger, Tyra Pacheco, 48, of Acushnet, were seriously injured when the Robinson R44 helicopter plunged into the salt pond June 17. Pacheco, a real estate photographer, had hired Ryan to fly her over homes she was photographing for local real estate companies.
The helicopter was flying at about 300 feet near the pond's western shoreline when Ryan reported feeling a lateral shudder followed by a clutch light illuminating, according to the report, which was issued in September. There was a violent yaw and the low pressure light went on. The engine oversped and then lost power completely. Ryan was able to crash land the chopper in shallow water near the pond's shoreline.
Examination of the wreckage at a recovery facility showed damage to cylinders and other sections of the engine consistent with engine overspeed, according to the report. Separation of the engine cooling fan shaft led to its overspeeding, which resulted in the damage which caused the engine to lose power.
Caked-on grease found on the after face of the fan shaft's lower sheathing was consistent with leaking grease in the lower forward clutch bearing seal; metallurgical examination of the bearing showed that the rollers had seized and no grease was found, indicating a lack of lubrication.
At the time of the accident, the helicopter's total flying time was 2,194 hours, but its hour meter indicated that it had flown an additional 59.5 hours since the previous inspection. That put the total flight time past the 2,200 hours which the manufacturer's maintenance manual sets as the required overhaul time for the entire airframe. The error was tied to an incorrect notation by an employee of the manufacturer during a 2006 repair and inspection, according to the NTSB report. Had the error not been made and the airframe undergone the required maintenance in a timely manner, the engine cooling fan driveshaft lower bearing and seal which failed would have been overhauled, the report states.
The aircraft's manual also requires the lower clutch actuator bearings to be lubricated every 300 hours or three years. The bearings that failed were lubricated about one and two years before the accident, but before that there was a nearly five-year gap, encompassing 685.1 hours of flight time, during which there was no record of the bearings being lubricated. That likely damaged or degraded the bearings and led to the failure, the report states.