History of Flight
On May 5, 2017, at 1402 Pacific daylight time, a Robinson R44 helicopter, registration N981RR, lost engine power and landed hard following an autorotation near Santa Barbara, California. The helicopter was registered to Spitzer Helicopter LLC and operated by Santa Barbara Helicopter Tours as a revenue sightseeing flight under 14 CFR Part 91. Visual meteorological conditions prevailed, and no flight plan was filed. The local flight departed Santa Barbara Municipal Airport at about 1345.
The flight was planned as a standard 20-minute "City Tour" for two passengers, a roundtrip from the airport to the Santa Barbara Zoo area, about 10 miles east. The outbound leg was uneventful, with the pilot requesting special VFR clearance due to low cloud ceilings. On the return, weather had not improved, and the pilot requested special VFR to land. Controllers directed the pilot to hold outside airport airspace due to landing traffic; the pilot circled for about 10 minutes until clearance was granted. He then proceeded west along Highway 101 toward the airport. Shortly thereafter, the engine began losing partial power, coincident with the clutch actuator light illuminating. The pilot pulled the clutch actuator circuit breaker while evaluating options and maneuvered toward a golf course for landing. Seconds later, the engine lost all power.
The pilot initiated an autorotation, intending to land on the golf course. During the final descent, he realized he could not reach the grass due to a wall and landed just short in a parking lot. During the flare, the main rotor blades struck a building roof, and the helicopter landed hard, spreading both skids. All occupants egressed. The golf course superintendent, hearing the impact, attempted to extinguish a fire that developed at the rear fuselage. Within minutes, the fire spread, engulfing the main cabin as local fire department arrived about 5 minutes later.
Multiple witnesses reported seeing an object fall from the helicopter as it flew over the highway. Post-accident examination revealed the engine's number 3 cylinder head assembly and piston were missing. A search located the assembly the following day in a field about 1/4 mile north of the wreckage.
Engine Examination
The engine was disassembled by Lycoming Engines representatives under NTSB supervision and FAA inspection. The engine remained attached to the aft frame support and forward mounts, with extensive thermal damage. The number 3 cylinder assembly had completely separated; its pushrods were not recovered. The lower crankcase deck adjacent to cylinder 3 and the oil sump were consumed by fire. The crankshaft was intact and visible through the opening; the number 3 connecting rod remained attached, with its piston end missing.
Examination for overspeed signatures per Lycoming Service Bulletin SB369N showed valves, springs, and rocker arms intact and undamaged. Valves slid easily, with no mushrooming or burrs. Valve keys and exhaust caps were undamaged; remaining pushrods straight. Camshaft was intact with shiny lobes and bearing surfaces, free of score marks. The oil filter, thermally damaged, contained bronze-colored non-ferrous metallic debris similar to connecting rod bushing material.
Materials Laboratory Examination
The crankcase, six connecting rod wrist pins, twelve wrist pin plugs, through bolts, main bearings, and cylinders 3 and 4 assemblies were examined. The number 3 cylinder attachment studs and throughbolts showed necking, smearing deformation, and matte gray fracture features consistent with ductile overstress. The number 3 connecting rod fractured just short of the missing bushing. The corresponding piston was mostly intact with wrist pin in place, showing multiple impact marks and skirt deformation trapping the piston in the barrel. A segment of the upper skirt was missing; a lower segment was fractured and flattened, both consistent with contact with the connecting rod.
Attachment holes on the upper cylinder flange were elongated in the direction of shear deformation. The lower flange was bent and cracked through two attachment holes, with ductile overstress fractures. Most of the cylinder attachment flange appeared dark gray; some areas had orange oxidation or light gray smearing. Machining marks were visible.
The crankcase halves had smooth, polished mating surfaces with scattered pits. Similar pits were on saddle surfaces and camshaft journal bore. The connecting rod for cylinder 3 fractured where the wrist pin bore intersected the beam; a curved impact mark matched the cylinder barrel skirt at the 6 o'clock position. Fracture surfaces showed ductile overstress in compressive shear. Connecting rods 2, 4, and 6 outboard ends were bright blue; rods 1 and 5 had slight blue tint. Wrist pins from cylinders 1, 2, 4, 5, and 6 were mostly free of mechanical damage but heat-tinted. The number 3 wrist pin had mechanical damage and was light gray. Bushings in three connecting rods had shifted; two had split lines rotated 45 degrees.
Maintenance History
According to maintenance records, the engine had 1,473 hours since a Lycoming factory rebuild in 2011. The tachometer was destroyed, but the operator reported an additional 36.5 hours. Records showed oil changes per Lycoming Mandatory Service Bulletin SB-480E at 50-hour intervals, with checks for metal particles. The last oil change was April 1, 2017, 39.8 hours before the accident; the logbook noted oil filter and screen examination. Oil was never sent for spectrographic analysis. No evidence indicated connecting rods or bushings were changed since rebuild.
Maintenance Bulletins and Directives
Lycoming Mandatory Service Bulletin SB-630, issued April 10, 2017, required connecting rod bushing inspection after cylinder removal. SB-632 (July 17, 2017) and SB-632B (August 4, 2017) called for replacement of non-conforming bushings in certain engines; the accident engine was not affected. FAA mandated SB-632B via AD 2017-16-11 on August 15, 2017.
CASA Airworthiness Bulletin AWB 85-020 Issue 3 stated that Lycoming engines new, factory rebuilt, or factory overhauled in 2011 were susceptible to premature connecting rod bushing wear, noting that bushings may shift axially, causing wear. The bulletin stated regular oil and filter inspections are effective in detecting this condition. Lycoming representatives stated no evidence corroborated AWB 85-020 findings for 2011 engines; FAA found no need for a similar U.S. directive.
The helicopter was fitted with fuel tank bladders per Robinson Helicopters Service Bulletin SB-78B.