Failure Knowledge Database / 100 Selected Cases

Decompression of B-737 of Aloha Airlines by Separationof Upper Fuselage
April 28th, 1988, near Maui Island, Hawaii
KOBAYASHI, Hideo (Yokohama National University)
TERADA, Hiroyuki (Japan Aerospace Technology Foundation)(Summary)
On April 28th, 1988, a B-737 operated by Aloha Airlines left Hilo, Hawaii Island bound for Honolulu,Oahu. W hen it a pproached the cru ising hei ght of 7, 200m near M aui Isl and, a sudden de compression
occurred in the ca bin j ust behind th e c ockpit. A l arge part of t he cabin stru cture was lost . A lthough onecabin at tendant was suc ked out, the aircraft succe eded in m aking an em ergency la nding a t t he a irport i nMaui, because fortunately one hydraulic system had survived.
1. Component
Fuselage panel structure
2. Event
A B-737-200 operated by Aloha Airlines left Hilo, Hawaii Island bound for H onolulu, Oahu. When it
approached t he cru ising he ight of 7, 200m near Ma ui Island, a su dden decompression o ccurred at 1 3:46
local time in the cabin just behind the cockpit. The maximum hoop stress is exerted on the fuselage at thecruising altitude because of the pressure difference between the inside and outside of the cabin is largest.
A part of th e cabin structure measuring several meters in l ength was torn off. One cabin attendant wassucked 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 a lmost ni neteen years and s ufferedfrom wide spread fatigue damage.
The existence of a crack more than 120 mm in length had been visually recognized by a passenger at themoment of e mbarkation. 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.
3. Course
The a ircraft was fabrica ted in 1969 a nd had been in serv ice for alm ost ni neteen y ears. It ha dexperienced 89,600 fl ight cycles before the accident. The single lap joint of the f uselage panel structures
was manufactured by cold-bond process using scrim cloth and rivets. It was known that the cold-bonded
joints have n ot e nough d urability i n t hermal and h umid cy cle condition. As a m atter of c ourse, fastenerjoints received heavy corrosion damage during 19-years operations. Under the thermal and humidity cycle
conditions due to operation, the fuselage structure was subjected to Wide-spread Fatigue Damage (WFD),1

Failure Knowledge Database / 100 Selected Cases

including Multiple-Site D amage (MSD ). Mor eover, the o perator has not c onducted the p eriodical
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.
4. Cause○ Direct cause
Unstable pr opagation of m ultiple s ite cracks i nduced b y corrosio n fa tigue took place at the fuse lage
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.
○ Indirect cause
Aloha A irlines neg lected to co nduct th e perio dical m aintenance t hat w as spe cified by M anuals an dRegulations. I t was just a matter of tim e tha t a cra ck lon ger t han 100 mm that was easily vis ible fro moutside the aircraft would occur that was overlooked by the operator.
5. Countermeasure(1) In ord er t o prevent the wa ter a bsorption of the b onded joints, wh ich is the m ain cause of j ointdegradation, the bonding process was changed from cold bonding to hot bonding.
(2) The Fe deral Aviation A dministration ( FAA) dir ected Aloha Airl ines t o observe the m aintenancemanuals strictly in order to maintain the airworthiness of the aircraft.
6. Knowledge
The accident investigation authority revealed that Aloha Airlines had deliberately neglected to conduct
the maintenance and inspection in order to reduce operation expenditures. The maintenance manuals andrules are essential for safe operation, so operators should not neglect them for any reason.
7. Background
Because of t he company's poor economic condition and high priority given to profits, A loha Airlines
had customarily ignored even the minimum necessary m aintenance at the tim e of the ac cident. Therefore,
they overlooked large cracks that even a passenger could visually recognize at the moment of embarkation.
8. Sequel
Until the time of th is acc ident, the F AA had als o bee n in volved in s upervision of th e ai rcraft
manufacturers in reg ard to various items such as design for dura bility and pro duction management of theaircraft besides the primary role of the supervision of aviation safety issues. However, concern was raised
after th is acc ident t hat th e F AA might not be a ble to pro vide sufficiently strict su pervision t o th emanufacturers w hen cri tical safety pro blems occur re lated t o d esign, m anufacture, m aintenance, andmanagement of aircraft. Therefore, the policy of th e FAA was chan ged to supervise only items related tosafety evaluation and not to commit to items related to design and manufacture.

2Failure Knowledge Database / 100 Selected Cases

If a sim ilar i ncident w ere to occur in J apan, s ome peop le w ould criticize t he r esponsibility of t heregulating government authorities and, opposite to the United States, call for th ose authorities to become
even m ore invol ved i n su pervising s afety desig n a nd manufacturing, for unlike. This case is a h ighlysuggestive e xample of h ow much respons ibility andauthority shou ld be given to g overnment

administration.
9. Social Impact
The problems of the str uctural integrity of aging aircraft became the focus of much interest all over theworld.

The irresponsible attitude of the airline company regard ing the safety management w as strongly

denounced.
10. Information Source(1) Aviation Week and Space Technology, vol. 128 (May 16, 1988).
11. Primary Scenario
01. Organizational Problems
02. Poor Management
03. Poor Work Management
04. Ignorance
05. Insufficient Knowledge
06. Durability of Cold-bonded structure
07. Usage
08. Maintenance/Repair
09. Negligence of Inspection
10. Malicious Act
11. Ethics Violation
12. Profit Oriented Policy
13. Usage
14. Transport/Storage15. Air Transportation
16. Bad Event
17. Chemical Phenomenon
18. Bonded Joint of Composites
19. Material Deterioration
20. Failure
21. Large-Scale Damage
22. Flapping of Fuselage structure
23. Emergency Landing

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Failure Knowledge Database / 100 Selected Cases

24. Loss to Organization
25. Social Loss
26. Loss of Credit

4Failure Knowledge Database / 100 Selected Cases

Fig. 1

B-737 Made an Emergency Landing with Large-scale Peeling of Fuselage.

Upper Plate
Rivet
Tear Strap

Cold Bonded
Scrime ClothLower Plate
Tear Strap

Fig. 2Bonded and Riveted Lap Joint of B-737 Fuselage.

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Failure Knowledge Database / 100 Selected Cases

Bonded Joint of Fuselage

Degradation by Aging

Multi-Site Damage

Inspection Error

Results

Yes

Flapping Failure

NoRepair/Modification

Yes

Yes

NoRepair / Modification

NoIntegrity

Fig. 3 Event Tree.

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Failure Knowledge Database / 100 Selected Cases

Unstable fractureof fuselage

MEDMSD

Changde of loadtransmission mechanism

humidity

Aging

Cold bonding

Hot bonding

Single Damage

No changed of loadtransmission mechanism

FODFig. 4 Fault Tree.

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Delamination