History of Flight
On March 13, 2011, at about 0930 Pacific daylight time, a Sikorsky S-58ET, registration N33602, descended and veered off the side of an office building while lifting an external load from the roof in El Segundo, California. The commercial pilot was seriously injured; the helicopter was substantially damaged and consumed by a post-impact fire. The helicopter was registered to Heli Flight, Inc., and operated by Aris Helicopters under 14 CFR Part 133 for rotorcraft external load operations. Visual meteorological conditions prevailed, and no flight plan was filed. The flight had originated from Riverside, California, at 0829.
The pilot reported arriving at Riverside Municipal Airport early in the morning, performing flight planning and a preflight inspection. During preflight, he turned on battery power and conducted an electrical functional check of the cargo hook, noting 1,200 lbs of fuel (800 lbs forward, 400 lbs aft). In a later statement, he reported 1,450 lbs of fuel. The helicopter departed at 0829, flew direct to Fullerton, then to the Raytheon facility. Witnesses reported the helicopter arrived between 0845 and 0900. The pilot spent about 0.2 hours in the parking lot with the rotor turning at flat pitch before beginning heavy equipment lifts. The flight's purpose was to lift building HVAC equipment from the Raytheon building roof. Total flight time was about 1 hour.
Just prior to the final lift, the pilot told ground crew he had about 400 lbs of fuel (200 lbs forward, 220 lbs aft). While lifting an air scrubber from the roof, the pilot reported an engine “went off line.” Witnesses heard an engine wind down. The helicopter drifted forward, the long line became taut, the nose pitched down, and the helicopter veered off the side of the roof. The pilot pressed the cargo release switch a couple of times before the helicopter went over the side. The entire helicopter impacted the side of the building, trees, and landscaping. The pilot was extracted by ground crew, and a fuel-fed post-impact fire ensued. Ground crew stated that at least one engine remained operating and both T-handles (emergency fuel shutoff) were pulled, successfully shutting down the engine(s). The pilot did not use the manual cargo hook release because it was a foot lever near the antitorque pedals, and he did not want to remove his feet from those pedals.
The air scrubber being lifted had been out of service for 2–4 years, contained no water, and was estimated by the manufacturer to weigh 4,700 lbs. The operator stated the helicopter's maximum lifting capability was 5,000 lbs. Aris Helicopters had submitted a lift plan to the FAA, which was approved on March 8, 2011.
Personnel Information
The pilot, age 52, held a commercial pilot certificate for rotorcraft-helicopter and a certified flight instructor certificate, issued January 10, 2006. He held a second-class medical certificate with a near-vision glasses limitation, issued July 21, 2010. Pilot records from February 4, 2010, showed total flight time of 7,182 hours, all in helicopters, with 2,673 hours in the Sikorsky S58. His most recent FAR Part 135.299 competency check was flown on April 30, 2010, in an SK-58T.
Aircraft Information
The twin-engine helicopter, serial number 58-727, was manufactured in 1974. It was powered by a Pratt & Whitney PT6T-3 Twin-Pac, consisting of two turboshaft power sections attached to a single combining gearbox, capable of producing 1,800 shaft horsepower. Normal fuel consumption was about 952 lbs/hour at maximum continuous power. The helicopter was equipped with a 6,000-pound capacity Onboard Systems cargo hook installed May 13, 2005. Maintenance records showed a Phase 2 inspection completed on March 11, 2011, at a helicopter total time of 8,929 hours.
The pilot reported a preflight inspection at 0730 on March 13. He checked fuel quantity and performed electrical and mechanical functional checks of the cargo hook. The pilot initially told the Safety Board investigator-in-charge (IIC) on March 23 that the fuel load was 1,200 lbs (800 forward, 400 aft). In a written statement on August 22, he reported 1,450 lbs (213.2 gal). Fuel records showed the helicopter was last fueled on March 11 with 97 gal. According to the S-58T Flight Manual, the left engine (#1) and right engine (#2) are identified as such from the pilot's seat.
Wreckage and Impact
The wreckage was located along the southwest face of the east wing of the Raytheon building at 2000 E. El Segundo Blvd, El Segundo, California. Broken tree branches were distributed on the ground and entangled in the wreckage. The wreckage consisted of the helicopter nose section containing the PT6T-3 Twin Pack, and the tail section with the tail rotor. The main fuselage, cockpit, and cabin were consumed by fire, leaving mostly ash and molten metal. Both fuel tanks were consumed by fire. The main rotor transmission case, made of magnesium, was consumed by fire, leaving only the mast, bull gear, bevel gears, and rotor head. All four rotor blades were severed outboard of the blade-to-hub attachment and were accounted for near the wreckage. Each blade showed twisting and longitudinal separation of the trailing edge. One blade exhibited fire damage. All four tail rotor blades were present on the hub and gearbox, with no evidence of rotational damage.
The cargo hook trapeze cables were attached to two steel frames, and the hook remained attached in the closed position. The long line steel eye guide was still on the hook; the rope material was consumed by fire. The mechanical release cable was severed, and electrical release wires were destroyed. The long line, sheathed in a protective sleeve, remained attached to the air scrubber. The end of the long line closest to the helicopter showed expanded, charred, and bubbled nylon-like material, consistent with separation by extreme heat. The left landing gear main mount was found on the roof. The southeast corner of the roof's steel guard rail exhibited impact damage. Rotor blade sections were found on the roof and in third-floor office space below the damaged rail.
Due to fire damage, the cargo hook circuit and the electrical bus that energized the hook could not be positively identified.
Tests and Research
On March 22, 2011, the helicopter wreckage was examined at the Aircraft Recovery Service facility in Pearblossom, California, with assistance from the FAA, Pratt & Whitney Canada, and Aris Helicopters. No pre-existing airframe anomalies or failures were identified. The PT6T-3 twin pack was shipped to Pratt & Whitney Canada for further examination.
From April 26–28, 2011, the engine was disassembled and examined at Pratt & Whitney's facility in Montreal. The #2 engine intake screen had organic dried leaf-like material embedded; the #1 screen was clear. Both engines showed minimal impact damage and moderate fire/heat damage, with light rotational signatures. There were no indications of pre-impact distress or operational dysfunction in any engine components, controls, or accessories. Functional testing of fuel nozzles, surge accumulators, valves, flow dividers, bleed valves, and power turbine governors was satisfactory. Fire and impact damage precluded functional testing of fuel pumps, manual fuel control units, automatic fuel control units, and fuel oil heat exchangers; disassembly showed no conditions that would preclude normal operation.
On June 21, 2011, the cargo hook was examined at Onboard Systems in Vancouver, Washington. The hook, part number 528020-06, SN 494, was discolored soot gray, and its casing halves were warped with a gap. The mechanical release fitting had a modified guide tube and b-nut. Disassembly showed all components accounted for, no foreign debris or unusual wear, and all components in proper position and moving as designed. The solenoid for electrical release was dark and sooty but the actuator moved freely and returned to normal position by hand. No evidence was found that would have precluded normal hook operation. Onboard Systems demonstrated that the hook would open freely when the solenoid was energized or mechanical release activated, with no additional force required.