B4/1999L Landing Gear Malfunction of a HS 125-700B Aircraft and Landing at Helsinki-Vantaa Airport on 3 September 1999

A serious incident occurred at Helsinki-Vantaa airport on 3 September 1999 at 18.40 lo-cal time, when a twin-engined HS 125-700B business jet made an emergency landing with the right main landing gear fully retracted. The aircraft was owned by Wihuri Ltd and operated by Jetflite Ltd. There were seven passengers and three crewmembers on board. The emergency landing was successful, and the aircraft was only slightly dam-aged considering the severity of the incident. After the aircraft came to a stop, the pas-sengers and the crew exited calmly, assisted by firemen, and no one was injured. The landing gear malfunction was caused by a fracture of hydraulic cylinder lugs.

On 6 September 1999, the Accident Investigation Board, Finland (AIB) set up a com-mission to investigate the incident. Trouble-shooting coordinator (ret.) Heikki Tenhovuori was appointed investigator-in-charge. Airline pilot Harro Erofejeff from Finnair Oyj and Chief Air Accident Investigator Tero Lybeck from AIB were appointed members of the commission. In addition, two AIB’s advisors were consulted: divisional fire officer Jari Hiltunen on the rescue operations and air traffic controller Ari Huhtala on ATC opera-tions.

Mr. Lybeck had a preliminary interview with the crew immediately after the incident. The pilots were later interviewed again at the AIB on 16 and 21 September 1999. The rescue personnel was interviewed on 9 September 1999, 11 October 1999 and 16 March 2000 at Helsinki-Vantaa airport and at the premises of Vantaa municipal fire brigade.

The data from the flight data recorder (FDR) and cockpit voice recorder (CVR) was read out by Finnair Oyj technical department at Helsinki-Vantaa airport. The quality of FDR data was good, but the recorder had stopped at the final stage of final approach, as the crew switched the power off in accordance with emergency procedures. The CVR had not been working on the incident flight, since its drive belt had broken on the day before.

A test to determine the effect of runway foaming on friction coefficients was made at Tampere airport on 23 November 1999, on fire officer Hiltunen’s initiative.

The fracture mechanism of the lug was examined by the Manufacturing Technology unit of the Technical Research Center of Finland (VTT). As the investigation commission found, at an early stage of the investigation, that the landing gear maintenance program had been inadequate for detecting the failure, it made a proposal for correcting the issue to the US Federal Aviation Administration (FAA) on 8 October 1999. The proposal was also sent for information to the US accident investigation authority, the National Trans-portation Safety Board (NTSB) and to the aircraft manufacturer, Raytheon Ltd. On 29 February 2000 the FAA reported having accepted the proposal.

The draft investigation report was sent for comments to the Civil Aviation Administration, Finland, on 21 March 2000. CAA Finland had no comments on the report. The investi-gation was closed on 19 April 2000.

B4/1999L Report (pdf, 0.22 Mt)

 
Published 3.9.1999