On August 17, 2007, an Airbus A 330-200 was involved in an aviation accident near Int. Verkehrsflughafen München, DE. No fatalities were reported. Investigators recorded the probable cause as: The right main landing gear bogie beam fractured due to stress corrosion cracking initiated by a corrosion pit where the corrosion protection coating was degraded or missing. This summary draws on records from the German Federal Bureau of Aircraft Accident Investigation (BFU); 8 related events involving the same aircraft type or operator are linked below.
On 17 August 2007, an Airbus A330-200 suffered a severe incident at Munich Airport when its right main landing gear bogie beam fractured during taxiing. No injuries were reported.
Incident Overview and Location Details On 17 August 2007, a commercial Airbus A330-200 experienced a severe incident at Munich International Airport. The aircraft, which was equipped with two Rolls-Royce RR Trent 772B-60 engines, was manufactured in 2000 with serial number 328 and was registered in the United Arab Emirates. At the time of the incident, the aircraft had a maximum takeoff weight of 233,000 kg and an actual takeoff weight of 198,631 kg. The aircraft was carrying 244 passengers and 15 crew members. ## Sequence of Events The aircraft departed from Terminal 1 parking position 113 at 15:50 local time and taxied across the West apron. It used taxiways Oscar 1, Charly 4, and entrance Sierra 6 to reach the area of runway 26L. Around 16:00, as the aircraft left the Sierra 6 entrance area and initiated a left turn onto taxiway Sierra, the right main landing gear bogie beam fractured. The fracture occurred in the area behind the shock absorber attachment. Immediate braking brought the aircraft to a stop behind the curve. All 244 passengers and 15 crew members evacuated the aircraft uninjured using passenger stairs provided on the taxiway. ## Aircraft and Personnel Information The pilot in command held an Airline Transport Pilot License (ATPL) issued by the General Civil Aviation Authority of the UAE in 1994 and possessed a Class 1 medical certificate. The co-pilot held a Commercial Pilot License (CPL(A)) issued by the UAE authority in 2006 and also held a Class 1 medical certificate. The fractured landing gear component was manufactured in November 1999 and had accumulated approximately 32,616 flight hours and 8,682 takeoffs and landings before the incident. ## Meteorological and Airport Conditions The incident occurred during daylight hours with scattered clouds. The wind was from 170° at 4 knots, and ground visibility exceeded 10 kilometers. Munich International Airport features two parallel concrete runways, 08L/26R and 08R/26L, each 4,000 meters long and 60 meters wide. The aprons and taxiways also have concrete surfaces. ## Damage and Investigation Findings At the intersection of entrance Sierra 6 and taxiway Sierra, a hydraulic oil stain and an impact mark were found on the concrete surface. A groove 42.8 meters long and up to 3 centimeters deep extended along the curve radius from the impact point. The aircraft came to rest on taxiway Sierra facing 082°, tilted to the right. The right engine and wing did not contact the ground. The right main landing gear beam was broken into two pieces, with the fracture located approximately 90 mm behind the joint pin connecting the shock absorber leg to the beam. The rear portion of the beam, including the rear axle and wheels, was completely detached, remaining connected only by two brake linkages. The aircraft reached its final position while the lower end of the shock absorber leg's attachment fork was dragging on the taxiway. ## Technical Analysis Initial on-site examination revealed the fracture originated at the 6 o'clock position on the inner circumference of the beam. Paint was missing in several areas on the inside of the beam floor, and damage was visible on both fracture surfaces from movement over the taxiway. The lower edge of the outer circumference was worn on both sides of the fracture. The lower side of the gear leg fork and the brake linkage were also worn. Brake hoses for the rear wheels were torn. Various substances, including lubricants and contaminants, were found inside the beam. The two beam halves were removed, sealed, and sent to the United Kingdom for further investigation with the support of the landing gear manufacturer under the supervision of the UK Air Accidents Investigation Branch. Samples of residues inside the beam were taken, and the beam was cleaned around the fracture. The paint coating was found to be peeling or missing in some areas, with a rough surface or blisters in others. Where paint was missing, a cadmium plating was visible. Immediately around the crack origin, in an area of approximately 50 mm by 50 mm, the material surface was free of paint and cadmium plating and was corroded. Non-destructive testing showed no evidence of other cracks. Material testing indicated no over-stressing during manufacturing and low residual stresses. Tensile tests on material samples met the material specification. Light microscopy at 30x magnification localized the fracture origin at the surface on the inner bottom of the beam. A corrosion scar was visible at the origin. The corrosion hole had a total depth of 0.669 mm and a surface diameter of 1.534 mm. The fracture surface around the pitting corrosion showed signs of intergranular fracture with a typical thumb-nail shape. Shear lip length was 10.506 mm, and fracture bands were found to a depth of 6.4 mm. Crack propagation occurred through stress corrosion cracking. The remaining fracture surface had a ductile appearance. The wall thickness was thinner than the original due to material loss from dragging on the taxiway. Scanning electron microscopy confirmed the light microscopy findings. ## Corrosion Protection Analysis The focus then shifted to the corrosion protection of the landing gear beam. No corrosion protection remained in the fracture origin area. In some areas inside the beam, the paint coating had blistered. Opening some blisters revealed that the paint had detached from the cadmium layer. According to the manufacturing specification, the corrosion protection consisted of multiple layers. Measurements of paint layer thickness at the edge of the missing corrosion protection area around the fracture origin showed that all three layers were thinner than required or absent in some places. This was also confirmed at measurement points in the front part of the beam. Layer thicknesses at the 6 o'clock position were lower than at the 12 o'clock position. The area around the fracture, specifically around the joint pin hole, showed the most severe degradation of the corrosion protection layer. Adhesion tests of the paint inside the beam in the fracture or joint pin hole area showed the paint peeled off easily, while all other areas performed well. Analysis of residue samples from inside the beam identified the lubricant as Type Nyco 22, which constituted the largest portion of the residues. Traces of Skydrol hydraulic fluid were found, attributed to the torn brake hoses. The residues also contained sand, with a water content of less than 1%. The acid content in the lubricant was typical. No fire occurred. ## Testing and Research After determining the fracture mechanism and corrosion as the trigger, the corrosion protection system was further investigated. Three different test procedures were conducted using corrodeable steel test pieces. In the first test, painted, oven-dried test pieces were half-immersed in distilled water or contaminant solutions at an ambient temperature of 70°C for two weeks.
Probable cause
The right main landing gear bogie beam fractured due to stress corrosion cracking initiated by a corrosion pit where the corrosion protection coating was degraded or missing.