Incident Overview
On January 7, 2016, at approximately 1100 Alaska standard time, a Robinson R44 II helicopter (registration N395CE) sustained a total loss of engine power just prior to departure at Anchorage International Airport in Anchorage, Alaska. The private pilot, who owned the helicopter, and his flight instructor were not injured. The helicopter itself was undamaged. The aircraft was registered to and operated by Airglas, Inc., under 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and no flight plan had been filed.
Flight and Engine Failure
The flight instructor reported that the purpose of the flight was a post-maintenance check flight following servicing and overhaul of the helicopter's fuel injection servo assembly. After an extensive preflight inspection, the helicopter was moved outside the hangar. The engine was started and warmed up for about 10 minutes; all ground run-up checks were satisfactory. While operating at 100 percent rotor rpm and raising the collective to begin takeoff, the engine abruptly lost all power.
Post-Incident Examination
The helicopter was equipped with a fuel-injected Lycoming IO-540 series engine. A post-incident inspection of the fuel servo assembly revealed a white, greasy substance within the venturi of the servo assembly. Maintenance records indicated that the fuel injection servo had been overhauled on December 14, 2015, by Alaskan Aircraft Engines, Inc., of Anchorage, before reinstalled on the accident helicopter.
On January 14, the NTSB investigator-in-charge (IIC), another NTSB investigator, and a representative from Precision Airmotive LLC examined the fuel injection servo at Precision Airmotive's facilities in Marysville, Washington. Due to excessive white grease-like contamination behind the test port plugs, the servo was not flow tested. Disassembly revealed large amounts of white contamination ranging from grease-like to solid consistency. The contamination was found in the manual mixture control valve, idle valve plate, fuel section O-rings, and the fuel diaphragm, with the bleed port almost completely blocked.
Investigation of Assembly Practices
On January 19, the NTSB IIC, another NTSB investigator, and two FAA aviation safety inspectors visited Alaskan Aircraft Engines, Inc., in Anchorage. They disassembled a recently overhauled fuel injection servo, which revealed excessive amounts of a white grease-like substance consistent with that found in the accident helicopter's servo. A representative from Alaskan Aircraft Engines stated that about six months prior, they had switched assembly lubricants to Dupont Krytox, an approved lubricant, but the investigation revealed it was not being used in accordance with the maintenance manual, resulting in excessive and inappropriate application.
Manufacturer's Lubrication Guidance
Dupont describes Krytox 240 series greases as white, buttery greases based on perfluoropolyether (PFPE) oils. They are used in extreme conditions such as continuous high temperatures up to 300°C (572°F) and are chemically inert, nonflammable, and safe for use with hazardous chemicals and oxygen service.
The Precision Airmotive Corporation Aircraft Fuel Injection Maintenance Manual for the RSA-10-AD1 Fuel Injection Servo Assembly lists three specific locations for Krytox application, with instructions to remove excess lubricant using Fluoroclean X-100. A representative from Precision Airmotive stated that Krytox should be applied in a thin, light coat, with all excess removed, only at the locations specified in the manual.
Service Advisory
On January 19, Alaskan Aircraft Engines issued a Service Advisory stating that beginning in June 2015, they began using an approved assembly lube that they had not used previously. The lube was used in excess and in locations not required by the manufacturer's service manual, which they believe has the potential to cause a fuel distribution problem.