How Decompression of B-737 of Aloha Airlines by Separation of Upper Fuselage

On April 28th, 1988, a B-737 operated by Aloha Airlines left Hilo, Hawaii Island bound for Honolulu, Oahu. When it approached the cruising height of 7,200 m near Maui Island, a sudden decompression occurred in the cabin just behind the cockpit. A large part of the cabin structure was lost. Although one cabin attendant was sucked out, the aircraft succeeded in making an emergency landing at the airport in Maui, because fortunately one hydraulic system had survived.

A B-737-200 operated by Aloha Airlines left Hilo, Hawaii Island bound for Honolulu, Oahu. When it approached the cruising height of 7,200 m near Maui Island, a sudden decompression occurred at 13:46 local time in the cabin just behind the cockpit. The maximum hoop stress is exerted on the fuselage at the cruising altitude because as the pressure difference between the inside and outside the cabin is largest.
 A part of the cabin structure measuring several meters in length was torn off. One cabin attendant was sucked out of the aircraft and was not found, but the aircraft succeeded in making an emergency landing at the airport in Maui, because fortunately one hydraulic controlling system had survived.
 The B-737-200 was an aging aircraft that had been operating for almost nineteen years and suffered from widespread fatigue damage.
 The existence of a crack more than 120 mm in length had been visually recognized by a passenger at the moment of embarkation. The reason why this crack had been overlooked by Aloha Airlines was that they did not conduct the maintenance inspections specified in the manuals because of economic reasons.

The aircraft was fabricated in 1969 and had been in service for almost nineteen years. It had experienced 89,600 flight cycles before the accident. The single lap joint of the fuselage panel structures was manufactured by cold-bond process using scrim cloth and rivets. It was known that the cold-bonded joints have not enough durability in thermal and humid cycle condition. As a matter of course, fastener joints received heavy corrosion damage during 19-years of operations. Under the thermal and humidity cycle conditions due to operation, the fuselage structure was subjected to Wide-spread Fatigue Damage (WFD), including Multiple-Site Damage (MSD). Moreover, the operator has not conducted the periodical inspection and maintenance of the structure required by Regulations even under such deteriorated condition. As a result, the operator overlooked cracks that were long enough to be found visually by passengers.

(Direct cause)
Unstable propagation of multiple site cracks induced by corrosion fatigue took place at the fuselage panel structure. Because the single lap joint had been manufactured using scrim cloth by the cold bonding process, the scrim cloth and adhesives absorbed water and became brittle over the years of operation.
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Indirect cause.
 Aloha Airlines neglected to conduct the periodical maintenance that was specified by Manuals and Regulations. It was just a matter of time that a crack longer than 100 mm that was easily visible from outside the aircraft would occur that was overlooked by the operator.