ERA18LA161

The commercial pilot was delivering the helicopter to a factory service center for troubleshooting of an engine-idle discrepancy that maintenance personnel could not resolve following a recent engine crankshaft overhaul and reinstallation. The pilot reported that the engine idled smoothly at engine start and that it initially accelerated smoothly and ran continuously without interruption. However, while the helicopter was at 100 knots and in cruise flight at 400 ft above a beach, the pilot felt "violent shaking," which he initially thought was turbulence. He then added aft cyclic, lowered the collective, scanned the instruments, and the shaking stopped. He then noted zero oil pressure, and the oil pressure light illuminated. The rotor rpm began decaying, so he entered an autorotation. Because people were on the beach, he selected an unoccupied area in the water for a forced landing, during which the tailboom separated. Examination of the engine revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded the normal operation. Although the electrically operated auxiliary fuel pump was not functional during a postaccident test, the engine-driven mechanical fuel pump operated normally. Given that the mechanical fuel pump can sustain engine operation if the auxiliary fuel pump is inoperative, it is unlikely that a preaccident failure of the auxiliary fuel pump resulted in the partial loss of engine power. The reason for the loss of engine power could not be determined.

On June 7, 2018, at 1340 central daylight time, a Robinson R44 II helicopter, N755KT, was substantially damaged during a forced landing to salt water after a loss of engine power near Fort Morgan, Alabama. The commercial pilot was not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the flight which departed Gac Waterfront Heliport (FD32), Navarre, Florida and was destined for Baton Rouge Metropolitan Airport (BTR), Baton Rouge, Louisiana. The ferry flight was conducted under the provisions of 14 Code of Federal Regulations Part 91.According to the pilot, he was delivering the helicopter to a Robinson factory service center at BTR. The pilot stated, "We were having trouble with the idle power of the helicopter. It was stumbling at idle power, but we had no trouble at the high-power settings. [A local] mechanic couldn't quite figure out what was going on with it, so we were going to have Robinson look at it." The pilot said he departed FD32 and the engine idled smoothly at engine start. It then accelerated smoothly and ran continuously without interruption until the loss of engine power in cruise flight. While in cruise flight at 400 feet along the beach at 110 knots, the pilot felt "violent shaking" and thought he had flown through turbulence. He added aft cyclic, lowered the collective, scanned the instruments, the shaking stopped, and he noted zero oil pressure, the oil pressure light illuminated, rotor rpm decaying, and he then entered autorotation. The beach was "full of people" and he selected an unoccupied area in the water just off the beach for the forced landing. The pilot held a commercial pilot's certificate and a flight instructor certificate, each with ratings for rotorcraft-helicopter and instrument helicopter. His Federal Aviation Administration (FAA) second-class medical certificate was issued March 27, 2018. He reported 811 total hours of flight experience, of which 747 hours were in the Robinson R44. According to Federal Aviation Administration (FAA) records, the helicopter was manufactured in 2004. Its most recent annual inspection was completed April 25, 2018 at 1,395.1 total airframe hours. At that time, the Lycoming IO-540-AE1A5 engine was reinstalled after an overhauled crankshaft and counterweights were installed and other work was performed. The helicopter had accrued 29 hours since the inspection. At 1335, the weather recorded at Sonny Callahan Airport (CQF), 16 miles north of the accident site included scattered clouds at 6,000 feet and winds from 270°at 3 knots. The temperature was 30°C, and the dew point was 19°C. The altimeter setting was 30.00 inches of mercury. The wreckage was examined at the site by an FAA aviation safety inspector. The tail rotor and its associated gearbox were separated from the helicopter and recovered from the water. An NTSB air safety investigator examined the helicopter's engine about 1 week after its recovery, and he provided a summary of the exam. Asfound, the magnetos had been removed from the engine, opened, and lying by the pilot's seat. Several wire bundles were cut, and electrical system continuity could not be verified. The spark plugs were removed and the interior of the engine was examined with a lighted borescope. All pistons and valves appeared intact, in "good condition," and displayed evidence of salt water corrosion. The engine's crankshaft was rotated by hand utilizing the fan at the engine's front. Thumb compression was obtained on all cylinders. Continuity was confirmed through the powertrain and valvetrain to the accessory section. The mechanical fuel pump was removed and pumped fluid when actuated by hand. The auxiliary pump did not operate when electrical power was applied. The electric motor was disassembled and the brushes, wiring, and some windings were burnt. The pump was dry and did not display evidence of water contamination. According to the helicopter manufacturer, engine operation can be sustained by the engine-driven pump only.