Aging Jet Had Troubled Past, Records Show

The Pan American World Airways jumbo jetliner that crashed Wednesday in Scotland was the 15th-oldest 747 model delivered by the Boeing Co. and had a history of trouble that included cracks, corrosion, an on-board fire and smoke in the cabin, federal records show.

Some of these problems are characteristic of aging aircraft.

The troubles are cited in service difficulty reports filed to the Federal Aviation Administration by Pan Am. A computer study of seven years’ worth of these reports by The Times shows that since 1980, the Pan Am plane had experienced at least 24 mechanical difficulties severe enough to warrant official notation.

Extensive Modification

The number of such reports on the aircraft during 1987 appears statistically to be higher than average, but at least some of them may have resulted from the additional scrutiny that the aircraft received during an extensive modification that it underwent that year.

Officials stress that it is still far too early to determine what caused Wednesday’s crash, but aviation sources said the plane’s abrupt disappearance from radar screens and the loss of radio contact at 31,000 feet suggest the possibility of some sort of “catastrophic event” such as a bomb explosion or sudden decompression caused by structural failure.

Boeing spokesman Jack Gamble said the Pan Am 747 was taken out of service between April 11, 1987, and Sept. 27, 1987, when it underwent substantial modifications at Boeing’s Wichita facilities. Gamble said the modification in 1987 “invalidates” the service difficulty reports, because any structural deficiencies would have been repaired at that time.

The aircraft was put into the “civil reserve air fleet” program, an Air Force program that modifies civilian jetliners for future use in war or national emergency. It was substantially disassembled and major structural parts were reinforced, Gamble said. For example, floor beams were reinforced to allow cargo to be carried.

He said that although the aircraft, built in 1970, was the 15th 747 of 710 delivered thus far by Boeing, its usage over the years has not been above average. Gamble said that the aircraft had flown an estimated 72,000 hours and made about 16,500 “cycles”--one cycle being a takeoff and landing.

“When you look at the economic design life of a 747, 60,000 hours would be average, 20,000 cycles would be average and 20 years of age would be average,” he said.

“That is the point where the operator is going to have to expect to do more frequent inspections, more frequent repairs to keep the aircraft at the level of integrity to continue operating safely.”

Corrosion and Cracks Found

In fact, the largest number of service difficulty reports came during 1987, while the aircraft was out of service for modifications. They numbered 11. Six reported corrosion and cracks. The largest crack measured 16.3 inches and was discovered in the upper part of a fuselage bulkhead. It was described as a corrosion stress crack. During the same inspection, a 2.2-inch crack was found in a splice plate, a joint area between metal parts.

Inspectors also found moderate- to-severe corrosion in splice plates--as well as some severe corrosion on a bulkhead.

Just one month before, on Oct. 22, 1987, maintenance personnel, responding to a service bulletin from Boeing that suggested inspecting specific portions of this and all similar 747s, found severe corrosion at the rear bulkhead of the Pan Am aircraft and severe corrosion on a portion of the fuselage.

The other 1987 service difficulty reports cited a sheared nose gear bolt, a missing pylon panel, two instances of smoke in the passenger cabin and fire spewing from the No. 1 engine pylon.

Five reports were filed during 1980. One cited a crack, another a loose bolt and a third reported a fuel odor in the cabin and in the cockpit. A fourth service difficulty report in 1980 cited failure of the plane to turn when it was on autopilot. The autopilot was disengaged and ailerons were discovered to be locked in place.

“Used strong force, broke free,” the report says.

The fifth 1980 service difficulty report cited a flame-out of the aircraft’s No. 2 engine during cruise flight. Inspectors replaced a fuel heater filter.

Other service difficulty reports were filed in 1981, 1983, 1984, 1986 and 1988.

The 1981 and 1983 reports cited a number of cracks in the airplane’s floor beams and a floor beam web. The 1984 reports cited fractures in exhaust casing rails and trailing edge flaps that were locked in place. The 1986 report cited communication problems.

Leading Slat Lost

And on March 25, 1988, a service difficulty report noted that a leading edge slat fell off the aircraft shortly after takeoff from the airport in Karachi, Pakistan.

Two years earlier, the FAA had issued an emergency Airworthiness Directive calling for the inspection of all 747s that had made at least 10,000 takeoffs and landings. The order followed the discovery of severe cracks in the fuselage frames of four other aging 747s.

The directive said three adjacent fuselage frames in the first plane checked had been “found essentially severed,” and it warned that “failure of adjacent frames could lead to rapid decompression of the fuselage and possible loss of the airplane.”

Officially, Boeing attributed the cracks to structural failure. But one Boeing official suggested at the time that they were caused in part by the fact that the 747 fuselage is not round.

“We put the hump on top of it for an Air Force contract we didn’t get, and that gave it flat sides,” the official said in 1986. “They are a ‘hard part’ in the design that were going to get some cracking. Sure as hell, now they have.”

The devastating effects of sudden decompression apparently caused by cracking and metal fatigue in aging planes were graphically illustrated last April when a 19-year-old Aloha Airlines Boeing 737 was ripped open “like a convertible” during a flight between the Hawaiian Islands. That plane, however, was used primarily for short-distance trips and had made 79,000 takeoffs.

The plane managed to land despite losing the upper two-thirds of an 18-foot section of the fuselage and because the passengers were all securely belted in, only one person--a stewardess who had been standing in the aisle--was killed.

Investigators later found cracks in fuselage rivet holes, and subsequent inspections of other aging 737s revealed the same problem.

The investigation of Wednesday’s crash will be headed by the British Civil Aviation Authority, the rough equivalent of the American National Transportation Safety Board.

“Because it happened over England, they’ll be calling the shots,” said Dick Russell, a veteran airline pilot who serves as a safety consultant to the Air Line Pilots Assn. (ALPA).

“They’re very thorough,” Russell said. “They have top-notch technical people.”

NTSB spokesman Mike Benson said his agency will be sending a lead investigator to Scotland today to assist in the probe.

“As we learn more, we’ll send more people with the appropriate specialties,” Benson said.

Some of those specialists will be from other agencies, such as the Federal Aviation Administration, and from “interested parties” such as Pan Am, ALPA and Boeing.

A team of pilots from Pan Am was reported en route to the crash site late Wednesday.

Times staff writer Ralph Vartabedian and Times computer analyst Paul Orwig contributed to this story.