FORT LAUDERDALE, FL, USA
XATDU
Dassault F2TH FALCON
The captain stated that the copilot was flying the aircraft, and after rotation, as they were climbing through about 150 to 200 feet, there was the sound of a loud bang, and they felt extreme vibrations. The captain stated that the No. 2 engine gages went to zero, and there was no indication of fire. He further stated that the copilot continued flying the aircraft, and stayed in the pattern, returning for an otherwise uneventful landing. Postincident examination of the airplane revealed that a 2 to 3-foot section of the right engine nacelle, from approximately the 9:00 to the 6:00 o'clock positions, had torn outward, in line with the high-pressure turbine (HPT) area of the engine. Macroscopic examinations, as well as microscopic examinations of the No. 2 engine and recovered portions were conducted, and the examinations revealed a 360-degree circumferential groove on the aft face of the disk, just outboard of the aft 4-tooth knife-edge steel flange. The groove in the disk was consistent with the disk having been in contact with the 1st-stage low-pressure turbine support/nozzle assembly inner casting forward static seal. In addition, rivet holes on the forward static seal, and on the forward flange revealed the presence of fretting marks, which were inconsistent with those of a tightly mated assembly. Instead, the fretting was indicative of an assembly that allowed relative motion between the surfaces. Furthermore, an examination using a scanning electron microscope on the available rivet heads and rivet shanks revealed that one of the rivet shanks showed indications of fatigue, and that the fatigue originated from at least two areas on the outer diameter surface of the shank, and was indicative of high cycle fatigue. There were also heavy fretting underneath the heads of the rivets on the surface that mated with the seal, and the fretting was similar to that found on the front face of the seal, The fretting was consistent with there being insufficient clamping preload on the rivets.
HISTORY OF FLIGHT On June 27, 2000, about 2030 eastern daylight time, a Dassault F2TH Falcon, XA-TDU, registered to Aviacion Comercial de America, in Monterrey, Mexico, and operated as a Title 14 CFR Part 91 positioning flight from Fort Lauderdale, Florida, to Monterrey, Mexico, had a failure of the No. 2 engine shortly after takeoff from Fort Lauderdale. Visual meteorological conditions prevailed, and an instrument flight plan was filed. The Mexican commercial-rated pilot and second pilot were not injured. The flight was originating at the time of the incident. The captain stated that he was in the right seat, and the second pilot was flying the aircraft from the left seat, and after takeoff from runway 09 left, as they were climbing through about 150 to 200 feet, there was the sound of a loud bang, and they felt extreme vibrations. The No. 2 gages went to zero, and there was no indication of fire. The second pilot continued flying and stayed in the pattern, returning to Fort Lauderdale International Airport, where he landed without further incident. PERSONNEL INFORMATION The second pilot held a commercial pilot certificate with airplane multiengine land and instrument ratings, and had accumulated 6,700 total flight hours with about 600 flight hours in the same make and model as the incident aircraft. He also held a class 1 medical certificate issued on March 2, 2000. The captain held a commercial pilot certificate, with airplane multiengine land and instrument ratings. At the time the incident occurred, the captain had accumulated about 6,300 hours total flight time, with about 700 flight hours in the same make and model as the incident aircraft. The captain also held a class 1 medical certificate issued on September 1, 1999. AIRCRAFT INFORMATION The incident aircraft is a Dassault F2TH Falcon Jet, serial number 029. Records show that at the time of the incident, the aircraft had accumulated about 2,092 total flight hours, and had been inspected on May 3, 2000, about 73 flight hours before the incident. The aircraft was equipped with two CFE738-1-1B turbofan engines, mounted on either side of the aft fuselage on horizontal pylons. Both engines, serial numbers 105156 and 105157, had accumulated 1,891.14 hours total time since new, and also had accrued 1,059 cycles at the time of the incident. The engine that incurred the uncontained high-pressure turbine failure was serial number 105156, which was installed on the right side. METEOROLOGICAL INFORMATION The Fort Lauderdale-Hollywood International Airport (KFLL) 1953 surface weather observation was, few cumulonimbus clouds at 2,500 feet, scattered clouds at 8,500 feet, ceiling 15,000 feet broken, 25,000 feet overcast, visibility 10 statute miles, temperature 79 degrees F, dew point temperature 72 degrees F, wind from 070 degrees at 10 knots, altimeter setting 30.08. WRECKAGE AND IMPACT INFORMATION A postincident inspection of the airplane revealed a 2- to 3-foot section of the right engine nacelle, from approximately the 9 o'clock to the 6 o'clock positions, had torn outward, in line with the high-pressure turbine (HPT) area of the engine. As a result of the uncontained failure, the fuselage had received two skin ruptures, about 40 to 80 mm in length, on the right hand vertical stabilizer skin, between ribs N3 and N4, near the front spar. On the right aft fuselage, there were also 10 puncture holes located at FR30, 31, and 32, between stringers 2 through 8. Stringers 3, 4, and 5 had all broken between frames 31 and 32, and the leading edge vertical tail bird shield strut had been damaged, 76.0 mm from front to aft, and 55.0 mm from top to bottom, between the 6th and 15th fasteners from the leading edge of the bird shield strut. In addition, the two fairings, which covered the structural area at the base of the vertical tail, had also received multiple punctures. On the left aft fuselage, there were two holes between frames 30 and 32, between stringers 2 through 6. Stringers 2 and 3 had also been broken just aft of frame 31. Examination of the right engine revealed an approximate 270-degree penetration of the combustion case. From the 9 o'clock to the 6 o'clock positions, with both the 1st and 2nd-stage HPT disks missing. Both HPT disks had exited the engine, and were discovered in a parking lot, about 150 feet from the runway. The 1st-stage HPT disk had all blades fractured transversely across the airfoil root, and the 2nd-stage HPT disk was recovered with about 240 degrees of its web and outer rim missing. TESTS AND RESEARCH Portions of the 2nd stage HPT disk were sent to the Thomson Laboratory at GEAE, Lynn, Massachusetts, and to the Honeywell materials laboratory for examinations of static and rotating parts. The parts were examined for witness marks, failed components, and evidence of rotor shift. The examinations of the recovered pieces showed mostly overload damage. Examination of the HPT disk web/rim revealed a 360-degree circumferential groove on the aft face of the disk, just outboard of the aft 4-tooth knife-edge steel flange, and the groove in the disk was consistent with the disk having been in contact with the 1st-stage low-pressure turbine support/nozzle assembly inner casting forward static seal (forward static seal). There were no indications of fatigue, or other anomalies on the disk, and disk fracture surfaces were indicative of tensile overload failures. In addition, a "drop-check" showed that the forward static seal conformed to the "stack-up" requirements, and the distortion to the forward static seal was inconsistent with that associated with an installation error. There was no evidence of a shift in the HPT rotor system, no indications of a failure of the 1st-stage low-pressure turbine (LPT) support frame thermal spring that would have allowed the inner casting to move, and lastly, there were no indications of a failure within the LPT rotor system, that would allow it to shift, and push the inner casting forward. When examined, rivet holes on the forward static seal, and those on the forward flange revealed the presence of fretting marks, which were inconsistent with those of a tightly mated assembly. Instead the fretting was indicative of an assembly that allowed relative motion between surfaces. Furthermore, an examination using a scanning electron microscope on the available rivet heads and rivet shanks revealed that one of the rivet shanks showed indications of fatigue, and that the fatigue had originated from at least two areas on the outer diameter (OD) surface of the shank, and was indicative of high cycle fatigue. There were also heavy fretting underneath the heads of the rivets on the surface that mated with the seal, and the fretting was similar to that found on the front face of the seal, consistent with there being insufficient clamping preload on the rivets. For details of the engine examination, please refer to the Powerplants Group Chairman's Factual Report, (an attachment to this report). ADDITIONAL INFORMATION After the incident the engine manufacturer issued notifications to operators and technical representatives informing them of the incident involving CFE738 series engines, as well as issued service bulletins that specified additional borescope inspections of the engine for grooving on the aft face of the 2nd-stage HPT disk. The manufacturer also introduced a new forward static seal design and attachment method, specified an incorporation schedule for compliance with the service bulletin, as well as specified additional monitoring checks and break-in periods for the CFE738 engine. XA-TDU, its cockpit voice recorder, its No. 2 engine, and No. 2 engine components were released at various stages of the investigation. A representative of Dassault Falcon Jet Corporation acknowledged their receipt on September 10, 2001.
the fatigue failure of the rivets used to secure the inner casting forward static seal to the 1st-stage low-pressure turbine support/nozzle assembly. The failure of the rivets allowed the forward static seal to machine a groove into the 2nd-stage high-pressure turbine disk to a depth that the disk could not withstand the operating loads, eventually leading to a disk burst and a high pressure turbine failure.
Source: NTSB Aviation Accident Database
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