Aviation Expert Says Boeing 737 Cracks Weren't Supposed To Happen

When the roof of a Southwest Airlines jet ripped open earlier this month, it could have been a disaster. Instead, the plane landed safely and the airline ordered an inspection of much of its fleet.

What could have been a terrible story ended up with a happy ending. Or did it?

Anthony Ingraffea, Cornell University professor of engineering, is an expert in structural aerospace engineering. He takes a different view of the incident than most of us. While the incident did not result in any loss of life, he says it raised troubling questions.

“When Southwest Airlines found a large crack in a Boeing classic model 737 fuselage in early April, shockwaves moved through the airline industry,” Ingraffea said. “The fuselage cracks weren’t supposed to happen so soon.”

Pressure

When jetliners take off and land, it subjects the cabin to intense pressure. Over time, with repeated takeoffs and landings – or cycles – the metal becomes fatigued and tiny cracks can appear.

In 1988, the fuselage of an Aloha Airlines Boeing 737 ripped open, killing a member of the flight crew and causing several injuries. After that, engineers from NASA, the FAA, industry and academia set about learning the causes.

This led to federal laws on aging aircraft. By 1993, after consulting with these many engineers, Boeing fixed the 737 aircraft and modified design for future models. That was supposed to fix the problem.

"Yet last week the Federal Aviation Administration issued an air-worthiness directive,” Ingraffea said. “The directive said that certain Boeing model 737 planes with more than 30,000 cycles had to be inspected for fuselage cracks every 500 cycles – which is a few months of service. For the airlines, that’s a substantial loss of revenue, due to a plane being grounded for inspection.”

Shocking

"The recent Southwest Boeing 737 plane had only 39,000 cycles and it was close to 15 years old. That’s what makes this problem so shocking,” he said.

The Boeing 737 plane involved in the Aloha tragedy had about 80,000 cycles. Boeing 737 airplanes used in U.S. domestic flights typically leave service after 60,000 cycles. Obviously from now on, they may leave service sooner.

But where will they go?

"Planes of advanced age are sometimes sold to international carriers, where fuselage cracks may not be examined or detected,” Ingraffea said. “For travelers flying on these international carriers: buyer beware."