QANTAS yesterday grounded a 747 aircraft because a crucial piece of equipment needed urgent maintenance, leaving the plane's tail at risk of breaking away.
The airline confirmed that QF31, due to depart Sydney for London via Singapore, had been delayed because of "maintenance requirements associated with a horizontal stabiliser jack screw".
The union representing aircraft maintenance engineers warned last night that if the jack screw was not lubricated regularly it could seize up and lead to a disaster.
Eight years ago an Alaska Airlines MD-80 jetliner crashed off the coast of Los Angeles, killing all 88 people on board, after its horizontal stabiliser jammed.
Steve Purvinas, the secretary of the Australian Licensed Aircraft Engineers Association, told the Herald : "The jack screw is an important component that has been known to seize up in the past. Regular lubrication and checking of the jack screw is vital because corrosion poses a real risk and must be eliminated to prevent this key component from seizing up."
He said the manufacturer, Boeing, had advised airlines that the jack screw needed to be overhauled between June last year and February. "Boeing issued a directive that this component needed to be checked more rigorously and more regularly."
A spokesman for Qantas confirmed that "there was a maintenance issue involving the lubrication of a jack screw on a Boeing 747-400. Qantas found this through a routine check of our maintenance records.
"The jack screw had been inspected and the aircraft will operate tomorrow."
But the spokesman rejected any comparison with the Alaska Airlines crash.
"There is no connection at all with any other aircraft incident. The Alaska incident involved a different aircraft type and design with different safety features," the spokesman said.
In a day of turmoil for Qantas, it was also revealed that a flight experienced an in-flight engine shutdown as it flew to Auckland, while a 767 was grounded in Melbourne because of a problem with the flap indicator in the cockpit.
A Qantas spokeswoman said all passengers aboard QF438 from Melbourne to Sydney were able to take alternative flights within 2½ hours. Qantas also confirmed that on approach into Auckland one of the four engines on its 747-300 was "reduced to idle".
The crew restored power and the jet landed without incident.
The union also claimed that Australia's air safety monitoring body had warned Qantas more than five years ago of potential problems with the forward pressure bulkheads on its 737-400 fleet, which it grounded on Tuesday afternoon.
According to an airworthiness directive from the Civil Aviation Safety Authority, its US counterpart, the Federal Aviation Administration, required that "certain actions [be taken] to prevent fatigue cracking on critical areas of the forward pressure bulkhead, which could result in rapid decompression of the aircraft fuselage". The document was dated May 2, 2003.
Mr Purvinas said the Civil Aviation Safety Authority directive referred to "strengthening clips" not properly attached to the bulkhead, just below the flight deck.
Yesterday Qantas insisted that the grounding of the 737-400 fleet was due to "paperwork" and was not a safety issue.
But Mr Purvinas said: "Not a safety issue, my arse.
"These aircraft [may] have been flying for up to five years with missing parts."
A Qantas spokesman insisted that the union's interpretation of the civil aviation authority's directive was "misleading".
"It fails to take into account that Qantas, as is always the case, received the approval of Boeing and CASA for this work before it was undertaken," he said.
"All modifications Qantas performed on the Boeing 737 aircraft were to a standard specifically approved by Boeing and CASA."
Qantas has not said when it will return its 737-400 fleet to service.