FAA Ordered Inspections of Old 737s in ’87

The federal government ordered the inspection of old Boeing 737s late last year for cracks in the portion of the upper fuselage where a 19-year-old Aloha Airlines jetliner ripped open in the sky southeast of Maui, officials said Friday.

The Federal Aviation Administration also ordered a lower-fuselage inspection of the nation’s entire Boeing 737 fleet in 1982, the officials said. That directive was prompted by the possibility of corrosion, which weakens the fuselage skin.

Built by Boeing

The two government orders were disclosed by spokesmen for the FAA and for the Boeing Corp., which manufactured the Aloha Airlines 737 that lost a major portion of its upper fuselage Thursday on a flight from Hilo to Honolulu. Sixty-one passengers were hurt and a flight attendant was sucked out of the plane and killed.

In Washington, federal officials said that investigators were focusing on a range of possible structural deficiencies that might have caused a sudden drop in cabin pressure. Such deficiencies, including possible cracks and corrosion, could have released the pressure explosively enough to blow off the top of the plane’s fuselage.

During Thursday’s accident, a gaping portion of the fuselage was torn away from the Aloha jet--down to seat level.

In Honolulu, FBI spokesman Robert Heafner said a preliminary investigation turned up no evidence of a bomb aboard the plane.

The Aloha jetliner was an old plane, No. 152 off the Boeing assembly line. The company has manufactured 1,109 aircraft like it. The Aloha jet was delivered in April, 1969, to a leasing firm which turned it over to Aloha immediately, Boeing spokesman Jim Boynton said.

A Los Angeles Times investigation two years ago showed that such old aircraft are subject to ever-increasing structural problems. At the same time, the investigation showed, the level of federal inspection and airline maintenance spending on such planes had declined.

At the time, Jerry J. Presba, one of three aircraft engineering and maintenance experts hired as consultants by The Times, said: “Altogether, it’s a formula for disaster.”

Federal documents show that the fuselage of the Aloha plane cracked and corroded eight times seriously enough to warrant reporting to the FAA during the past five years. Seven of the instances of cracking and corrosion were found in response to the government’s 1982 inspection order, FAA spokeswoman Bobbie Mardis said.

The eighth instance was a crack in the fuselage frame discovered in 1986 during a regular inspection.

Six other times, the plane suffered cracks in its wings. Those cracks included the plane’s most serious instance of structural failure before Thursday’s accident, Mardis said. In that instance, a crack was found in a repaired front upper spar chord 1.2 inches from the original repair.

Inspected Daily

The crack was inspected daily until “Boeing-coordinated repair/replacement” could be completed, according to a Service Difficulty Report filed with the FAA. The report was dated April 24, 1987.

“That was a major item,” Mardis said.

Workers usually fix such cracks by replacing the broken pieces of structure or by installing a splice, or a “doubler,” across the crack to secure both sides.

On still eight additional occasions, the plane encountered mechanical problems serious enough to be reported to the government. Those problems included a hydraulic failure during taxiing, hydraulic leaks, a broken nose wheel door latch and a tire cap separation. Cabin pressure was not affected.

In total, these problems with the plane’s fuselage, wings, flight systems and components caused 22 Service Difficulty Reports over five years, a record that officials said was not out of the ordinary for a plane of that vintage.

The FAA’s directive to inspect the upper fuselages of old Boeing 737s was issued last November. It was prompted by non-mandatory service bulletins issued by Boeing dating back to 1972 that called for inspections of the metal skin in this area of the plane, Boynton said.

The directive and the service bulletins were issued because of concern about cracks found near fasteners that join sheets of metal skin, he said. In addition, Boynton said, inspections found that metal strips on the fuselage were coming loose.

The inspection order required owners and operators of the first 291 Boeing 737s made to inspect their skin from just behind the front entry door to the tail section.

Boeing updated its service bulletins four times, Boynton said. The most recent revision came on April 14--just two weeks ago.

Stephanie Ackerman, spokeswoman for Aloha, said the airline was in compliance.

C. O. Miller, former chief accident investigator for the National Transportation Safety Board, said he was not surprised to hear that the Aloha investigation is focusing on possible structural failure. He cited similarities between what he saw in photographs of the Aloha plane and another Boeing 737 that crashed in Taiwan in 1981.

“In the Taiwan case, the structural failure was below the deck, as well as above it,” Miller said. “In this case, the structural failure--if that’s what occurred--was only in the upper section of the airplane. But in both cases the area in question was the same: from the leading edge of the wing to the cockpit.

“This takes on an added significance when you remember that the plane that crashed in Taiwan was the same year, same model as the one involved in this incident.”

Miller noted that the age of an airplane is not as good an indicator of potential trouble as the number of cycles--that is, takeoffs, landings and pressurizations--that the airplane has been through. But he added: “Since this plane has been in service with a commuter airline like Aloha since 1969, I guarantee it’s been through a lot of cycles.

“I also hope that the investigation will look beyond structures to possible difficulties with the pressurization system,” Miller said. “Pressurization could come into the picture because at 22,000-24,000 feet in altitude, which is where this incident occurred, you get the maximum stress on the airplane as a result of the difference between the growing pressure inside the airplane and the lower pressure outside. It would take multiple failures, but you could overpressurize and get a problem independent of structural failure.

Near Same Altitude

“I bring this up because this problem with the Aloha 737 occurred within a couple thousand feet of the altitude at which the Taiwan plane was flying when its structure failed. That altitude is in the region where the airplane reaches this maximum differential pressure as the result of pressurization.”

The Taiwan 737 crash also was cited two years ago in The Times’ investigation of the structural worthiness of the U.S. commercial air fleet. In that story, The Times reported that the Taiwan accident was one of a half-dozen structural failures that have contributed to major air tragedies during the last decade.

The Taiwan disaster resulted from “ . . . extensive corrosion damage in the lower fuselage structures,” according to an English transcript of the Taiwan accident investigation board. “Rapid fracture occurred . . . resulting in rapid decompression and sudden break of passenger compartment floor beams . . . and eventual loss of power, loss of control and midair disintegration,” the report stated.

Boeing, like all aircraft manufacturers, knows that eventually its planes will crack and corrode.

Thus, for the last 30 years, the FAA has required airframes to be strong enough to carry at least normal flight and ground loads even when one of their members is ruptured.

But long before major structural parts of an aircraft fail, periodic inspections are supposed to find the inevitable cracks in them.

Hence, the key to the structural safety system is inspection. This is especially true since, as an aircraft ages, metal fatigue accumulates and parts begin to crack at an accelerating rate. “Cracks get more serious as time goes on,” said Isaac H. Hoover, the retired manager of the FAA’s airframe safety program.

The trend of this cracking over an airplane’s life follows what is known as the “bathtub” curve, so-called because its shape resembles that of a bathtub.

The line of the curve charts the rise and fall in the number of cracks a typical fleet of aircraft experiences over its lifetime. There is an initial surge in cracks during the first six months to a year that an aircraft enters service. This is a period of “infant mortality” in which manufacturing glitches are worked out of the product, Hoover said.

After 10 years of typical service, most aircraft fleets experience fatigue damage at an accelerating rate. At 20 years--only a year older than the Aloha aircraft--the rate of damage has turned significantly upward, according to Boeing technical reports.

“For all fleets, the general shape of the curve is the same,” Ulf Goranson, manager of structural damage technology at Boeing, said in a 1986 interview.

And, indeed, airplanes in the United States’ commercial fleet are aging.

Fewer Reports

At the same time, The Times’ investigation concluded, the airlines are filing fewer legally required Service Difficulty Reports on structural defects, providing additional strong evidence that they are not finding the cracks. Since the government relies on such reports to evaluate the health of commercial aircraft, the decline has crippled the nation’s already deficient early warning system against air crashes caused by structural failure.

In the face of these developments, the Reagan Administration has let the task of holding the airlines to minimum safety standards outgrow the number of inspectors assigned to do the work--a job of policing that has burgeoned with each new airline and every airline expansion since deregulation.

The Times investigation also found that:

--The average age of each of the six types of aircraft in widest use by U.S. airlines had climbed every year from 1980 through 1984. By the beginning of 1985, all six--including the 737--were approaching or had passed the midpoint of what the Boeing Co. considers their economic lives.

--Despite the increasing likelihood of cracking caused by advancing age and metal fatigue, the amount of money the airlines are spending to find and fix cracks dropped over the five years from 1980 through 1984 for all six types of aircraft, including the Boeing 737. This drop is documented Service Difficulty Reports.

--Fatigue-crack reports filed with the government--again, including those on the 737--also had dropped, decreasing the likelihood of timely warnings about problems.

--The drop in SDRs correlates with an overall decline in the number of orders from the FAA to inspect for specific cracks and repair them.

--Arrayed against these downtrends is an FAA inspector force that has been shrinking in relation to the size of the air fleet. In 1979, the inspectors numbered 2,012. By 1984, because of budget cuts by the Reagan Administration, the number had dwindled to 1,332. During the period, the number of commercial airlines grew from 237 to 407.

Staff writer Richard E. Meyer reported from Los Angeles and Oswald Johnston reported from Washington.

THE BOEING 737 The Boeing 737-200 involved in Thursday’s incident was manufactured in 1969 and was placed into service by Aloha Airlines in April of that year. The Aloha plane was far older than the average 737 in service. Last October, the FAA required that such older 737s be inspected for possible cracks in upper sections of the planes’ outer skin.

Mathematical trendlines show that the 737 fleet has maintained a steady average age of 8.5 years, although reported structural problems have decreased. Annual maintenance spending has also decreased during the study years of 1981-84.

STRUCTURAL FATIGUE ON THE ALOHA 737 Among the important factors in determining the structural integrity of the nation’s commercial aircraft is their age, manufacturers agree. Advancing age makes planes more likely to crack. Boeing says that after a period of initial “shakedown” problems, planes should have few structural problems until they have been in service a number of years. There is an increase--reflected by what the airline industry calls a “bathtub” curve--in the number of structural defects after that point.

Superimposed on this curve is the actual service life of the 737 involved in the Aloha incident.