- Investigators in Egypt pore over Sinai wreckage seeking clues
- Metrojet A321 was damaged in 2001 when its tail hit runway
More than a decade before it burst into pieces mid-air, the Russian jetliner that crashed in Egypt on Saturday scraped its tail on a runway during landing and needed to be repaired.
Investigators poring over wreckage of the Metrojet Airbus Group SE A321 in Egypt’s Sinai peninsula will be taking a close look at a 2001 repair to the plane’s tail because it is one of the few things known to cause the type of sudden midair breakup that occurred Saturday, said John Goglia, a former airline mechanic who served on the U.S. National Transportation Safety Board.
“If the engineering is done right, it’s not an issue. If the repair follows the engineering data, it’s not an issue,” said Goglia, who isn’t involved in the Metrojet investigation. “But a breakdown in any one of those can and has resulted in catastrophic failures.”
Impacts between the rear of a plane and the ground during landing and takeoff -- known as “tail strikes” -- occur with some regularity, according to National Transportation Safety Board data. Since 2000, there have been at least 22 tail strikes that caused severe enough damage to warrant an investigation by the safety board, according to its online accident database.
Goglia estimates there were 10 times more tail strikes than listed in the NTSB database but the cases weren’t reported to the accident-investigation agency because they were minor. In a small number of cases, however, such repairs have failed so violently that planes split at the seams and crashed.
If it’s found that the 2001 repair on the Metrojet aircraft played a role in the accident, investigators will want to ensure that there are no repairs on other aircraft at risk of failing, Goglia said. They would typically review the plans for repairs and may even seek inspections of other repairs, he said.
All 224 people aboard the Metrojet, flying from Sharm el-Sheikh to St. Petersburg, died when it went down. Because debris was spread over an area as much as 8 kilometers (5 miles) long, officials believe it had to have broken up in flight, Alexander Neradko, head of the Russian Federal Aviation Authority, said in an interview with Rossiya-24 state television.
Part of the tail section on the Metrojet plane landed apart from other wreckage, indicating it broke off from the rest of the fuselage.
The plane’s tail had been properly repaired, Andrey Averyanov, deputy general director for engineering at Kogalymavia, which operates under the Metrojet brand, said at a briefing in Moscow Monday.
The plane, which was operated by another airline at the time, was repaired by Airbus in Toulouse, France, said Averyanov.
It’s too early to focus on a single possible cause, Steve Wallace, former chief of the U.S. Federal Aviation Administration’s accident investigation division, said in an interview. Investigators will be looking at factors including bombs, missiles, other on-board explosions and structural corrosion, Wallace said.
If the dome-shaped rear pressure bulkhead, which holds in air behind the plane’s cabin, is damaged, it’s typically repaired by adding an additional layer of aluminum sheet metal, Goglia said. Because the pressure within the cabin exerts huge stresses while a plane is at cruising altitude, the new metal is layered over a large area of the existing structure and riveted in place so it will hold, he said.
Damage to the bulkhead can occur because of an impact with the ground or as a result of cracking that occurs over time, he said.
“I’ve been around airplanes in the several hundreds that I’ve personally touched that have had bulkhead repairs done,” Goglia said. “It’s a non-event if it’s done right.”
While it may take years for a repair to eventually crack enough to fail, that can lead to a violent explosion damaging an aircraft, according to accident reports.
Such a failure occurred in 2002 when China Airlines Flight 611 flying from Taiwan to Hong Kong broke apart at the spot where the Boeing Co. 747’s tail was repaired 22 years earlier.
Japan Airlines Flight 123 hit a mountain in 1985 after a similar repair came apart, claiming 520 lives. When the repair let loose, it blew off the vertical fin rising out of the tail. Without that fin, the plane couldn’t be controlled.