FAYETTEVILLE, NC, USA
N34GG
British Aerospace HS 125-700A
Upon entering the traffic pattern at the destination airport, the landing gear was extended using the normal and alternate methods, the left main landing gear did not extend. The flight departed the traffic pattern, orbited the airport an attempts to extend the left main landing gear were unsuccessful. The flight diverted for an airport with Fire Rescue, performed a fly-by, then climbed to altitude where 'G-loading maneuvers were performed to extend the left main landing gear. The gear could not be extended. The airplane was landed with the left main landing gear retracted. Examination of the airplane revealed that the lugs on the cylinder head of the left main landing gear jack were fractured. Metallurgical examination of the fractured lugs of the cylinder head revealed overstress failure; no evidence of progressive (fatigue or stress corrosion) cracking was observed. The cylinder head is a 5,000 cycle life limited component and the failed cylinder head which was installed when the airplane was manufactured, had accumulated 4,751 cycles at the time of failure including the accident landing. The jack attachment and surrounding area required to be inspected every 600 hours, was inspected last 348 hours and 299 cycles earlier; no discrepancies were noted.
On October 19, 1999, about 0101 eastern daylight time, a British Aerospace HS 125-700A, N34GG, registered to and operated by N34GG, Llc, was landed with the left main landing gear retracted at the Fayetteville Regional/Grannis Field Airport, Fayetteville, North Carolina. Visual meteorological conditions prevailed at the time and an IFR flight plan was filed for the 14 CFR Part 91 business flight. The airplane was sustantially damaged and there were no injuries to the airline transport-rated pilot, commercial-rated copilot, and one passenger. The flight originated about 1700 pacific daylight time from the McCarran International Airport, Las Vegas, Nevada. The pilot stated that when the flight entered the traffic pattern at the destination airport and the landing gear was extended, there was no down and locked indication for the left main landing gear via the normal or alternate indication systems. The passenger was briefed what was occurring and what would occur, Air Traffic Control was advised of the situation, and a climb was initiated. The airplane was orbited over the airport and the landing gear was cycled three or four times. There was no down and locked indication from the left main landing gear. At the pilot's request, the flight was vectored to the nearest airport with facilities, which was the Fayetteville Airport. The pilot performed six fly-bys of the air traffic control tower located there for confirmation of the position of the left main landing gear. The pilot then initiated a climb to 8,000 feet where he initiated a series of "G" loading maneuvers and parabolic arcs with simultaneous yaw and gear extension with no success in extending the left main landing gear. The flight returned for landing at the Fayetteville Airport and after touchdown first on the right main landing gear, the left wing began to settle lower than usual. The pilot initiated a go-around, again briefed the passenger, and returned for landing. After touchdown, the airplane remained on the runway with the application of right brake and rudder input. Examination of the airplane revealed that the main gear jack cylinder head, part number AIR 111506, of the left main landing gear, exhibited broken lugs at the jack cylinder head location. The left main gear jack which was determined to be manufactured in April 1974 and was the original cylinder head installed when the airplane was manufactured, was removed from the airplane for further examination by the National Transportation Safety Board (NTSB). Examination of the left main gear jack by the NTSB Materials Laboratory in Washington, DC, revealed that the cylinder head attachment lugs failed due to overstress; no evidence of progressive (fatigue or stress corrosion) cracking was observed. A copy of the NTSB Materials Laboratory Factual Report is an attachment to this report. The airplane had accumulated 4,751 cycles at the time of failure including the accident landing. The maintenance records reflect that the left main gear jack cylinder head is a life limited part and is required to be replaced at 5,000 cycles. British Aerospace Service Bulletin 32-A197, dated August 29, 1983, which required a one-time inspection of the cylinder head lugs for cracking, was complied with on November 4, 1983; no cracks were detected. Service Bulletin 32-199, dated February 10, 1984, was issued citing the reason that "cracking of jack cylinder head attachment lugs has occurred on aircraft in service." The bulletin indicates that the "MAINTENANCE SCHEDULE will be revised to specify repeat inspection." At the time of the accident, there is no mention in any of the inspections covered in the Aircraft Maintenance Schedule (AMS) specifically stating to inspect the cylinder head lugs for cracking. According to Raytheon Aircraft Company personnel, inspection of the main gear side stay and jack attachment brackets and adjacent structure which is listed in the "600 Hour Inspection" document, would cover inspection of the jack cylinder head lugs. According to a facility that had maintained the airplane, the jack attachment brackets and adjacent area were inspected last on June 4, 1998, at an aircraft total time of 7,204 hours and 4,452 landings. The aircraft had accumulated 348 hours and 299 landings since the inspection at the time of the accident. Additionally, on March 25, 1998, the left and right main landing gears and sidestay assemblies were removed and replaced. The airplane total time and cycles at that time were 7,147.10 and 4,395, respectively; the airplane had accumulated 356 landings and approximately 405 hours since then at the time of the accident. The damage to the airplane was initially reported as minor; however, repairs to the airplane included replacing three ribs in the left wing. The incident was reclassified as an accident. The airplane minus the retained left main gear jack was released to Mr. Kim Allain, the Director of Maintenance for Virtual Jet, on January 14, 2000. The retained left main gear jack was released also to Mr. Kim Allain, on January 21, 2000.
The overstress failure of the lugs of the cylinder head of the left main landing gear jack for undetermined reasons. Also, inability of the flight crew to extend the left main landing gear.
Source: NTSB Aviation Accident Database
Aviation Accidents App
In-Depth Access to Aviation Accident Reports
