A third-party-maintenance error came close to disabling a Transavia Airlines Boeing 737-300 in flight with 146 passengers on board, and could have resulted in a crash but for the quick action of the crew, say initial reports from German air-accident investigators. The incident is believed to be a one-off, but other 737 operators have been informed.
On landing, it was discovered that the right horizontal stabiliser was so seriously cracked that it would have broken off within 5min, says an investigator, who praises the crew for acting so quickly to make an emergency diversion.
The accident occurred on an 8 February scheduled flight from Salzburg, Austria, to Amsterdam, the Netherlands. The crew felt serious vibration and elected to divert to nearby Nuremburg, Germany. Having briefed the passengers for a full emergency, the captain carried out a safe 15¹-flap landing in which no-one was hurt. The oscillations in the last 2min of the flight were so severe that the flight-data-recorder tape was displaced, degrading the recording.
The accident investigators found that a "really serious" crack had formed in the stabiliser near the outboard end of the elevator, leaving a large hole visible on its underside. Both front and rear spars were badly cracked. Investigators found that the elevator control tab had detached, and believe that the vibration started with disconnection of the tab control rod where it connects to the stabiliser assembly. The tab rods had then failed.
The maintenance error, which appears to have involved under-torquing of the self-locking nuts at the tab-rod attachment, is believed to have occurred in November 1996 when TAP Air Portugal was carrying out maintenance which included repainting the tail section of the aircraft.
Transavia emphasises that this information is not yet confirmed, and that the Portuguese authorities are carrying out their own investigation into the error.
Source: Flight International
