Question

Investigate Aloha Airlines (AA) Flight 243 incident and:

Discuss AA compliance with Service Bulletins and Airworthiness Directives relevant to the incident (as included in the official incident report). Include your assessment of SB 737-53A1039 in light of both the operating environment and the AA flight schedule.

RELEVANT REPORT: Accident Investigation Aloha Airlines AAR89-03

PLEASE PROVIDE ANY REFERENCES USED.

Answer 1

Ans = According to the official report , On April 28, 1988, at 1346, a Boeing 737-200, N73711, operated by Aloha Airlines Inc., as flight 243, experienced an
explosive decompression and structural failure at 24,000 feet, while en route from Hilo, to Honolulu, Hawaii.Approximately 18 feet from the cabin skin and structure aft of the cabin entrance door and above the passenger floorline
separated from the airplane during flight. There were 89 passengers and 6 crewmembers on board. One flight attendant was swept overboard during the decompression and is presumed to have been fatally injured; 7 passengers and 1 flight attendant received serious injuries. The flight crew performed an emergency descent and landing at Kahului Airport on the Island of Maui. The National Transportation Safety Board determines that the probable cause of this accident was the failure of the Aoha Airlines maintenance program to detect the presence of significant disbonding and fatigue damage which ultimately led to failure of the lap joint at S-10L and the separation of the fuselage upper lobe. There was minor impact damage on the leading edges of both wings, although the damage was more extensive on the
right wing. In addition, both horizontal stabilizers and the lower portion of the vertical stabilizer had random dents in the
leading edges.The inlet cowls of both engines were dented, and several first stage fan blades of both engines were damaged. Remnants of fuselage structure were found against the inlet guide vanes and embedded in the acoustic liner of the right engine .to the accident were the failure of Aloha Airlines management to supervise properly its maintenance force; the failure of the FAA to evaluate properly the Aloha Airlines maintenace program and to assess the airline's inspection and quality control deficiencies; the failure of the FAA to require Airworthiness Directive 87-21-08 inspection of all the lap joints proposed by Boeing Alert Service Bulletin SB 737-53A1039; and the lack of a complete terminating action (neither generated by Boeing nor required by the FAA) after the discovery of early production difficulties in the B-737 cold bond lap joint which resulted in low bond durability, corrosion, and premature fatigue cracking.The safety issues raised in this report include:

· The quality of air carrier maintenance programs and the FAA surveillance of those programs.
· The engineering design, certification, and continuing airworthiness of the B-737 with particular emphasis on multiple site fatigue cracking of the fuselage lap joints.
· The human factors aspects of air carrier maintenance and inspection for the continuing airworthiness of transport category airplanes, to include repair procedures and the training, certification and qualification of mechanics and inspectors.

So now let us discuss about the service bulletins which were mentioned in offical report of aloha airlines :

Boeing periodically issued information via SBs to inform operators of reported or anticipated difficulties with various
airplane models. The following communications were relevant to the B-737 fuselage structure, including section 43:
· Structural Item Interim Advisories (SIIA)
· Service Bulletins (SB)
· Service Letters (SL)
· In-Service Activity Reports (ISAR)
· Significant Service Items (SSI)
Nine SBs provided guidance for maintenance or information otherwise applicable to section 43. Of these nine SBs,
entries referring to the following five SBs were found in the Aloha Airlines fleet maintenance records:
SB 737-53-1017 Sealing of Cold Bonded Splices
SB 737-53A1027 Cargo Compartment Body Frames
SB 737-53A1039 Skin Lap Joint Inspection
SB 737-53A1042 Lower Lobe Skins
SB 737-53A1064 Frames Stations 351 and 360
Due to the method of entering the SBs in the Aloha Airlines maintenance records, the recurring nature of inspections
could not be determined. Also, entries for the following four SBs were not located in the records:
SB 737-53-1076 Fuselage-Bonded Skin Panel Inspection and Repair
SB 737-53-1078 Fuselage Window Belt Skin Panel Inspection and Repair
SB 737-53-1085 Fuselage Stringer to Frame Tie Clips Inspection and Replacement
SB 737-53-1089 Fuselage Skin Crack At Stringer 17 Inspection and Preventive Modifications
Aloha Airlines personnel stated that the information contained in these particular SBs had been incorporated into Aloha
Airlines letter check inspection system; however, specific documentation of this fact was not produced.

Lap joint corrosion occurring in service was first reported in 1970. Boeing Service Bulletin 737-53-1017 was released later that year to seal the lap joints to prevent corrosion, but this was only partially effective (sealing was also done in production starting at line number 249).

The cold bond lap joint design was discontinued in production in 1972. A redesigned lap joint that had increased joint thickness, allowing the rivets to transfer the pressurization loads, was introduced at line number 292. The adhesive bond that was used for load transfer was eliminated.

Boeing Service Bulletin 737-53-1039 was released in 1972 to inspect for lap splice corrosion.

Starting in 1974 there were reports of tear strap disbonding. The function of tear straps is to arrest the rupture of a crack, allowing for safe decompression by fuselage skin flapping.

Boeing Service Bulletin 737-53-1039 was revised (R2) in 1974 to also inspect for fatigue cracks in the lap splices. At the time of this revision, fatigue cracking had not yet been observed in service.

Boeing Service Bulletin 737-53A1039 was revised (R3) in 1987. The Service Bulletin was upgraded to alert status at this release (by now fatigue cracks had been observed in service at stringers S-4L, S-4R, S-10R, and S-14R).

In 1987 the FAA issued AD 87-21-08 which mandated some of the inspections in Boeing Service Bulletin 737-53A1039. The AD required that only the lap splices at stringers S-4 left and S-4 right be inspected (the service bulletin also provided information to inspect stringers S-10, S-14, S-19, S-20 and S-24, left and right). The Aloha accident occurred in 1988, following the failure of the lap splice at stringer S-10 left. The accident airplane was line number 152.

So now we can talk about Airworthiness Directives (AD) It became effective on November 2, 1987, was issued "to prevent rapid depressurization as a result of failure of certain fuselage lap splices...." The AD required operators to perform a "close visual inspection"12 of S-4L and R, and if cracks were found, operators were required to perform an eddy current
inspection13 of the skin around the upper row of lap joint rivets for the full length of the panel. Compliance with the AD
was required before the accumulation of 30,000 landings or within 250 landings after the effective date, whichever
occurred later. The AD was based on Boeing Alert Service Bulletin (ASB) 737-53A1039, Revision 3, dated August 20,
1987.An Aloha Airlines inspector testified at the public hearing that it was company practice to perform an eddy current
confirmation inspection whenever a crack was detected visually. Both the Aloha Airlines director of quality control and
the staff vice president for quality assurance and engineering stated that a Nondestructive Testing Report (Form No. M-
86) should be filled out by the inspector when any NDT inspection is performed. The form is then used by management
for tracking purposes. A search of the records for N73711 failed to find a copy of an NDT inspection report of the S-4R
lap joint.
The inspector who performed the initial AD inspection on N73711 stated that he did not believe that documenting the
eddy current inspection was necessary or required. During the investigation, Aloha Airlines did not produce a written
maintenance policy regarding the requirement for the entry of an eddy current inspection in the maintenance log.
However, a broad examination of maintenance records revealed that other inspectors had made such entries during this same time period.Two inspectors working on separate shifts conducted the inspection required by AD 87-21-08 on the accident airplane.They followed guidance in the AD and the related SB (SB-737-53A1039) which were taken to the work site. The first inspector started on November 12, 1987, and visually detected the cracks on S-4L. This inspector stated that after visually detecting the cracks, he performed an eddy current inspection of the lap joint upper rivet holes along the length of the panel (BS 360 to BS 540) and found no additional crack.