MIA01FA006

The mechanics failure to comply with manufacturers instructions for correction of a illuminated main rotor gearbox oil pressure warning light resulting in the helicopter being dispatched on a ferry flight with a failed main rotor gearbox oil pump, failure of the main rotor gearbox combining gearbox gears due to oil starvation, loss of main rotor RPM, and the helicopter colliding with trees and the ground during an uncontrolled descent.

About 5 minutes before landing at a hospital, the main rotor gearbox (MGB) oil pressure warning light illuminated. The pilot continued to the hospital, landed, and performed an immediate engine shutdown. A mechanic disconnected the wiring to the MGB oil pressure switch and the light went out. The mechanic stated he believed the oil pressure switch had failed and he asked the pilot to run the helicopter, hover the helicopter, and if everything was normal, to fly it back to the base hospital. The pilot did the run and hover, and then departed the hospital. The helicopter crashed about 1 minute later. Witnesses stated they heard the helicopter approach the crash site at a low altitude and making a slow thumping noise. Examination of the MGB showed the oil pump idler gear had seized in the oil pump due to undetermined reasons and the oil pump drive shaft had failed due to overstress. The teeth on the engine input gears, intermediate gears, and MGB drive gear in the MGB combining gearbox had failed due to high-temperature overstress, which was the result of oil starvation. The helicopter was not equipped with a MGB oil pressure indicator. The maintenance procedure for trouble shooting an illuminated MGB oil pressure warning light is to first check the electrical circuit, and if this does not correct the problem, to change the oil pressure switch. The mechanic stated he did not have the maintenance manuals with him while working on the helicopter. The MGB had been installed in the helicopter after overhaul, 3 days and 4 flight hours before the accident.

History of the Flight On October 16, 2000, about 2355 eastern daylight time, a Eurocopter AS-355-F2, N355DU, registered to Duke University, and operated by Corporate Jets, Inc., as a Title 14 CFR Part 91 maintenance ferry flight, crashed shortly after takeoff from Alamance Regional Medical Center, Burlington, North Carolina. Visual meteorological conditions prevailed at the time and no flight plan was filed. The helicopter was destroyed and the commercial-rated pilot was fatally injured. The flight originated about 1 minute before the accident. The helicopter was dispatched, with the pilot and 2 flight nurses, from Duke University Medical Center, Durham, North Carolina, to Alamance Regional Medical Center, at about 2209, to pick up a patient. The flight nurses stated that about 5 minutes before landing at Alamance Regional Medical Center, the main transmission oil pressure warning light illuminated. The pilot observed the light and reported to them that they were about equal distance from the Burlington-Alamance Regional Airport and the Alamance Regional Medical Center. They elected to continue to the Alamance Regional Medical Center and land. After landing the pilot stated he would not do an engine cool down, and immediately shutdown the engines. During the shutdown, one of the flight nurses reported noticing a burning type smell. This was brought to the pilot's attention and he stated it was probably due to the quick shutdown. The flight back to Duke Hospital with the patient was canceled and a mechanic was dispatched to repair the helicopter. One of the flight nurses stated that prior to leaving in an ambulance with the patient, she went back to the helicopter and spoke with the pilot. The pilot told her it was probably a short in a light switch. (See flight nurse statements.) The mechanic stated he arrived at the helicopter about 2330. The pilot reported to him that all was normal except for the transmission oil pressure light being illuminated. The mechanic stated he then inspected the helicopter for excessive oil leaks and none were found. He then disconnected the wire from the transmission oil pressure switch and the light went out. The mechanic stated in interview with the NTSB that he did not reconnect the transmission oil pressure switch wire prior to the helicopter taking off. Due to past years of problems with this switch as known by himself and the pilot, they made a decision to ground run and hover the helicopter and if there were no other indications such as vibration, noise, chip light, or temperature indication, and if the pilot felt comfortable with the helicopter, the pilot would fly it back to Duke Hospital. The mechanic observed from the ground, and after a period of run up and then hovering time, the pilot turned on his landing light and took off. (See mechanic statement). Transcripts of communications between the pilot of N355DU and the Duke University Medical Center, Life Flight Operation Center, showed that pilot reported at 2224 that the main gearbox oil pressure light had illuminated and that they would land at Alamance Regional Medical Center. At 2228, the pilot reported arriving at Alamance Regional Medical Center. At 2347, the pilot reported that N355DU is in service. At 2348, the helicopter is dispatched from Alamance Regional Medical Center. No further transmissions were received from the pilot. (See transcript of communications.) Witnesses located near the crash site, about 1.3 statute miles east-southeast from the takeoff point, reported hearing the helicopter approaching at what appeared to be a low altitude. They stated the helicopter did not sound normal to them and was making a steady drone and a low velocity thumping noise. They then heard the sound of tree limbs breaking and the helicopter crash to the ground. A postcrash fire erupted. (See witness statements). Personnel Information The pilot held a FAA commercial pilot certificate, last issued on January 21, 1994, with airplane multiengine land, rotorcraft helicopter, and instrument airplane and rotorcraft ratings. The pilot held a FAA Class 2 medical with no limitations, issued on June 14, 2000. Corporate Jets, Inc., hired the pilot on September 6, 1994. The pilot was assigned as a pilot on the Eurocopter AS-355 on April 25, 1996. The pilot received the 12-month knowledge, competency, and line check required by 14 CFR Part 135 on December 16, 1999. The pilot received a 6-month instrument flight rules proficiency checkon June 13, 2000. At the time of the accident the pilot had accumulated about 3,700 total flying hours, 3,400 flying hours in rotorcraft helicopters, and 400 flight hours in the Eurocopter AS-355. (See Pilot/Operator Aircraft Accident Report and pilot records.) The mechanic, who worked on the helicopter at the Alamance Regional Medical Center, prior to the accident, holds a FAA mechanic certificate with powerplant and airframe ratings, last issued on August 17, 1970. The mechanic holds a FAA private pilot certificate, with an airplane single engine land rating, issue on September 6, 1968. At the time of the accident the mechanic held a FAA third class medical certificate, issued on October 20, 1999, with the limitation that the holder shall wear correcting lenses while exercising the privileges of the certificate. Corporate Jets, Inc., hired the mechanic, on September 1, 1992. The mechanic received Eurocopter AS-355 Airframe Field Maintenance training on May 27, 1994. (See mechanic records.) Aircraft Information The helicopter was a Eurocopter (formerly Aerospatiale) model AS-355-F2, serial number 5489, manufactured in 1991. The helicopter was equipped with 2 Rolls-Royce (formerly Allison) 250-C20F, 420 shaft horsepower engines. At the time of the accident the helicopter had accumulated about 4,267 total flight hours. The helicopter was inspected on July 12, 2000, 75 flight hours before the accident, when it received a 100 hour and 200 hour airframe inspection in accordance with the operators approved aircraft inspection program. On October 12, 2000, about 4 flight hours before the accident, the helicopter received a 30-hour inspection. On October 12, 2000, about 4 flight hours before the accident, the main rotor gearbox assembly was replaced with main rotor gearbox serial number M5091, which had zero flight hours since overhaul by Eurocopter on October 9, 2000. This main rotor gearbox had accumulated about 6,870 total flight hours since new. This main rotor gearbox had oil pump serial number M5070 installed in it. The oil pump had zero hours since overhaul by Eurocopter on June 14, 1999, and had accumulated about 4,339 total flight hours since new. During overhaul of the oil pump, a new driven gear or idler gear was installed and a used drive gear was installed. The total time in service for the used drive gear could not be determined. Main rotor gearbox installation records showed that preservative oil placed in the gearbox after overhaul was drained and the transmission was serviced with new oil. The pilot who performed the test flight after the transmission installation and the pilot who flew the helicopter prior to the accident pilot stated the main rotor gearbox contained the normal amount of oil when inspected during preflight inspections. Records show that at the time of the accident, the helicopter was on the seventh flight since installation of the main rotor gearbox, and the helicopter had flown about 4 flight hours since the installation. (See maintenance records.) Meteorological Information Visual meteorological conditions prevailed at the time of the accident. The Burlington-Alamance Regional Airport automated surface weather observation taken at 2354, was wind calm, visibility 4 miles in fog, skies clear, temperature 55 degrees F., dewpoint temperature 54 degrees F., altimeter setting 30.10. The airport is located about 2 nm south of the accident site. At the location