History of Flight
On September 15, 2012, at 1200 eastern daylight time, an Aerospatiale AS 355F1 helicopter, registration N58020, operated by Analar Corporation, was substantially damaged when it impacted terrain following an in-flight breakup near West Windsor, New Jersey. The commercial pilot was fatally injured. The positioning flight was conducted under 14 CFR Part 91 in visual meteorological conditions; no flight plan was filed. The flight originated from Princeton Airport (39N) at about 1155, destined for Atlantic City International Airport (ACY).
According to the operator's president, the helicopter had flown during the summer with a loaner main transmission while its own was repaired. The repaired transmission was reinstalled on September 13, 2012, followed by a maintenance ground run and a 30-minute test flight with no anomalies. Earlier on the accident day, the pilot completed an uneventful roundtrip flight from 39N to West 30th Street Heliport (JRA) and back with a passenger. After that flight, the helicopter was hot fueled to capacity, then departed on the accident flight. The president estimated the helicopter had flown about 1 hour 10 minutes since the transmission installation.
Federal Aviation Administration (FAA) data indicate that the helicopter was in radio and radar contact with McGuire Approach Control; contact was lost at 1200 with no distress calls. Witnesses near the accident site reported hearing a banging, explosion, or engine rev noise, followed by a piece separating from the helicopter and the helicopter spiraling nose-down toward the ground.
Personnel and Aircraft Information
The pilot, age 65, held a commercial pilot certificate with ratings for airplane single-engine land, rotorcraft helicopter, and instrument airplane and helicopter. His most recent FAA second-class medical certificate was issued on July 21, 2012, as a deferred issuance due to new-onset atrial fibrillation. According to employer records, the pilot had about 11,100 total flight hours, with approximately 2,200 hours in the same make and model. He had flown about 21 hours in the 90 days preceding the accident.
The six-seat helicopter, serial number 5227, was manufactured in 1982. It was powered by two Rolls-Royce (Allison) 250-C20F engines, each rated at 420 shaft horsepower. The helicopter was maintained under a manufacturer-approved inspection program. Its most recent inspection was a 100-hour inspection completed on the morning of the accident, in conjunction with the transmission installation, at 11,431.3 total hours. The most recent 600-hour inspection was on June 5, 2012, at 11,332.7 hours.
Meteorological Information
Weather recorded at Trenton Mercer Airport (TTN), about 7 miles west of the accident site, at 1153: wind 350 degrees at 9 knots gusting to 16 knots; visibility 10 miles; sky clear; temperature 21°C; dew point 9°C; altimeter 30.14 inches of mercury.
Wreckage and Impact
The helicopter came to rest upright in a cornfield on a magnetic heading of 305 degrees. A postcrash fire consumed most of the cockpit and cabin. Flight control continuity could not be confirmed due to fire damage. The tailboom had separated forward of the horizontal stabilizer. The rotorhead, including the top portion of the transmission, main rotor shaft, starflex, and three main rotor blades, was located about 100 yards southwest of the main wreckage. The yellow main rotor blade and sleeve assembly separated from the rotorhead and were found about 270 yards southeast. The right horizontal stabilizer separated near the root and showed evidence of main rotor blade contact.
Metallurgical examination of retained components revealed that the upper rod end of the fore/aft servo (actuator) exhibited a bending overstress fracture near its neck. The lower threaded end of the upper rod end was not recovered. The mating threads of the fore/aft servo upper end fitting showed severe wear, consistent with thread wear over time. New thread impressions below the original worn threads were consistent with vibration of the shank in the actuator hole. No preimpact mechanical malfunctions were found on other components.
Maintenance and Examination Findings
Evidence of Mastinox, a corrosion-inhibiting compound, was found on the threaded shank of the left-roll and right-roll servo upper rod ends, but not on the fore/aft servo remnant. The operator reported using Mastinox with a thin layer of grease for servo connections due to dissimilar metals. The Eurocopter maintenance manual (MM) prescribed only G.355 grease for the servo rod ends, with a torque correction factor of 0.4 for G.355 grease. No factor was specified for Mastinox. The operator did not adjust the torque factor when using Mastinox with grease.
Maintenance procedures for servo-control rod end installation, found in Eurocopter MM Work Card 67.30.15.401, included applying a bead of sealant on the nut and thread. The daily operating check (Work Card 05.21.00.603) called for checking security and absence of leaks. The basic T/600-hour inspection (Work Card 05.23.00) required checking radial play of rod end bearings but did not specify checking torque or thread condition. The Eurocopter Standard Practices Manual contained general guidance for inspecting threaded components when removed, but there was no specific guidance for the security of the rod end connection to the servo end fitting during normal inspections.
The fore/aft servo (Air Equipment F6103 31026-010, serial number 68) was manufactured in 1981 and installed on the accident helicopter in 1994. Its most recent overhaul was in March 2008, and it was repaired in August 2010 and November 2011. During the November 2011 repair, items were replaced due to hydraulic fluid seepage; threads were inspected per the component maintenance manual (CMM) and no discrepancies were noted.
Medical and Pathological Information
An autopsy performed by the Mercer County Medical Examiner determined the cause of death as "Massive multiple traumatic injuries." Toxicological testing by the FAA detected metoprolol in the pilot's blood.