Accident Overview
At approximately 1000 central daylight time on July 2, 2020, a Robinson R44 helicopter, registration N7511D, was substantially damaged during an accident near Welsh, Louisiana. The commercial pilot, the sole occupant, sustained minor injuries. The helicopter was operated as a personal flight under Title 14 Code of Federal Regulations Part 91.
Flight Details
The helicopter, equipped with an aerial application spraying system, had been operating at Welsh Airport (6R1) for about 20 minutes, performing a chemical tank flush by spraying water to prepare for an upcoming job. After completing the flush, the pilot landed and then departed to a local farm to wash and clean the helicopter. During the 5-mile flight, the low rotor RPM horn activated, and the helicopter experienced a partial loss of engine power.
Emergency Landing and Impact
The pilot immediately lowered the collective and applied power without success, deciding to land immediately. During the off-field emergency landing, approximately 3 to 5 feet above the ground, the helicopter began spinning to the right. The pilot applied left pedal and rolled off the throttle to stop the spin, but it continued. The helicopter impacted a flat grass field and came to rest on its left side. The pilot egressed without further incident. Substantial damage was noted to the fuselage, tailboom, and empennage.
Postaccident Engine Examination
An airframe and engine examination was conducted. The camshaft and 12 tappet bodies were removed for further inspection. The camshaft was intact, but the lobe associated with the number 1 cylinder exhaust valve was substantially worn. The contact face of the corresponding tappet body (1E) was spalled and worn. Other camshaft lobes and tappet bodies appeared undamaged with normal wear, except the 6E tappet body showed deeper circumferential wear and scuff marks, and the 6I tappet body had heavy contact marks.
Various particles were found in the engine oil filter. Analysis indicated the particles were mostly organic compounds or combustion products, with minor amounts of lead and bromine consistent with avgas tetraethyllead additives. Other particles matched commercial aluminum or copper alloys.
Maintenance and Corrosion Considerations
The pilot reported the helicopter was purchased in mid-May 2020 and had accumulated 8.5 flight hours since its annual examination on June 9, 2020. The collective-activated hour meter read 1,843.3 hours at the time of the accident. Maintenance records showed only 11.3 hours flown in the previous year. The helicopter was based in Louisiana, which the FAA Advisory Circular 43-4B classifies as an area of severe corrosive attack on aircraft structures and engine materials.
Relevant Advisories and Service Bulletins
Australian Civil Aviation Safety Authority Airworthiness Bulletin (AWB) 85-014, issued November 23, 2012, addresses tappet body and camshaft lobe wear in Lycoming and Continental piston engines. It notes that spalling damage has been observed in certain tappet bodies, and that corrosion pitting from infrequent flight activity can lead to such wear. The bulletin emphasizes inspecting oil filters for metallic particles.
Lycoming Engines Service Bulletin (SB) 480F, issued May 25, 2017, provides procedures for oil servicing and inspection of metallic solids from filtered oil. It recommends cleaning and inspecting the oil suction screen every 50 hours or 4 months, and more frequent oil changes if the engine is exposed to corrosive environments.
Compliance and Missing Information
Compliance with AWB 85-014, SB 480F, and FAA AC 43-4B is not required under 14 CFR Part 91 or Part 137 operations. The investigation did not establish a probable cause.