Tail cone falls, flaps break
A sound like an explosion, a roar of wind—and horrified passengers stare at a circular 5-ft. hole in the rear of their Air Canada DC-9, 25,000 ft above the Atlantic. An American Airlines 707 loses a wing flap, which breaks into five pieces, two weighing more than 300 Ibs., over the Chicago suburb of Palatine. Another American 707 sheds the 11-in. by 13-ft. tip of a wing flap over San Francisco Bay. And federal investigators report that basic pilot errors committed by Yankee Catcher Thurman Munson caused his Cessna Citation I jet to crash at Akron-Canton airport on Aug. 2, killing Munson and injuring two passengers.
Those revelations last week gave the flying public another case of jitters. For the second time in four months, mechanics were searching for tiny fatigue cracks in another McDonnell Douglas aircraft, this time the DC-9. Unlike the Federal Aviation Administration's hunt for engine-pylon-mount fractures that followed the crash of a DC-10 near Chicago's O'Hare field in May, the agency this time saw no need to ground the DC-9 fleet.
The Air Canada incident could easily have turned into a tragedy. Flight 680, with 43 people aboard, was 60 miles out of Boston's Logan Airport on its way to Nova Scotia and had just reached its cruising altitude of 25,000 ft. when, as Passenger Betty Martin recalled, "We heard what sounded like a bomb. You could see the sky. We were all praying."
With the air pressure that had built up in the cabin and cockpit as the plane climbed, the aft bulkhead buckled, apparently because of an almost invisible 12-in. crack. The sudden decompression blew off the entire nonpressurized tail cone—a lO-ft.-long metal shell serving mainly to streamline the fuselage.
No one was killed, only because no one was in the lavatories at the rear of the plane or near the gaping hole. Pilot George Gill skillfully edged the crippled craft to a safe landing at Logan, even though he lacked full power in the right engine, apparently because a buckle securing control cables along the fuselage had broken loose.
The aft bulkhead problem was not a new one for the DC-9. McDonnell Douglas warned airlines three years ago that fatigue cracks had shown up in some early models of the plane. The manufacturers advised airlines to inspect the bulkheads more frequently or reinforce all of these early-model DC-9s with "doubler" pieces.
Air Canada had increased its inspections, but its mechanics overlooked the crack in the Boston plane until they re-examined old X rays of the bulkhead after the accident. Last week the FAA ordered U.S. carriers to make a special inspection of their DC-9s.
Both the FAA and the Boeing Co. reacted more cautiously to the 707 incidents. Reason: no one knew what caused the planes' flaps to rupture. While federal investigators looked for answers, the manufacturer maintained that there was no cause for concern, even though the five chunks of heavy metal that fell on Palatine narrowly missed hitting a school.