Case Study: Aloha Airlines Flight 243
Twenty-nine years ago, on 28th of April 1988 the upper fuselage of Aloha Airlines 243 ripped off the aircraft at 24,000 feet, killing one crew member and injuring many more. Thankfully the pilots did a miraculous job and was able to land the aircraft safely. Metal fatigue at the time wasn’t really on the radar of the Federal Aviation Authority or the airline maintenance programs. Even when the manufacture brought attention to the lap joint corrosion and fatigue the govern authority fail to react. The accident aircraft was also part of the aging fleet program and it was surveyed. Boeing found several issues with the aircraft, but the airline failed to respond to Boeing recommendations because they didn’t want to hold the aircraft down for several month. After this incident aviation maintenance and regulations concerning metal fatigue were changed forever.
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Aloha Airlines flight 243 was an inter-island flight heading to Honolulu International Airport from Hilo International Airport. The morning prior to the flight the first officer performs the external inspection of the aircraft and accepted it for flight. The aircraft then flew from Honolulu to Maui, then from Maui to Hilo. No pre-flight inspection was done on the aircraft because there was no requirement to do so. The flight departed Hilo at 13:25 heading to Honolulu. Soon after the aircraft reached its cruising altitude of 24,000 feet 18 feet of the upper portion of the fuselage above first class section ripped off and later it was discovered the aircraft had an explosive decompression. And if that wasn’t enough during landing the aircraft also suffered a left engine failure which made landing the aircraft more difficult. The pilot and first officer were able to overcome all the failures and land the aircraft safely. In all one of the flight attendants was killed, one flight attendant and 7 passengers were also injured. It’s amazing that any one lived at all. With everything that happened this aircraft should have crashed many more would have been killed if not for the actions of the flight crew.
Since the upper section of the fuselage was never recovered it was difficult for investigators to determine what had caused the upper section of the first-class cabin to rip off. Upon initial interviews the pilots reported the aircraft was in good condition and they saw no defects during the initial walk around on the first flight of the day. But during interviews a female passenger reported seeing a large crack in the fuselage between the cabin door and the edge of the jet bridge. Obviously, she didn’t think it was of no concern, figuring someone else had seen it and she didn’t report it to the flight crew. During the interview she described the crack to investigators extending along a row of rivets. She was taken to another like aircraft by the investigators so she could show them the location of the crack. After pointing out to investigator the area on the other aircraft and it was found to be at the upper row of rivets along the S-10L joint. A lap joint is basically where the pieces of aircraft skin would meet and joint together to form the joint. Rivets are put in place to hold the lap joint together. This is the exact area that the investigators determine the upper skin section started to separate off the aircraft.
Early on Boeing had performed many tests on the effects of external damage resulting in a large crack in the skin of an aircraft. The tests showed that Boeing’s fail-safe design could suffer a 40-inch crack in the skin and not suffer a catastrophic failure to the aircraft fuselage. There were also tear straps added to the skin of the aircraft that would redirect running cracks into different directions. The problem with these tests is they were performed on normal aircraft and Boeing never took into consideration what would happen if a crack had developed on an aging aircraft (Wrigley, 2018). This is where metal fatigue comes into play. According to Encyclogedia.com, Metal fatigue is; “In material science, fatigue is the process by which a material is slowly and progressively (and oftentimes permanently) damaged by stresses and strains that are less than those needed to actually break the material apart” (The Gale Encyclopedia of Science, 2008). There were many reports on the lap joints dealing with metal fatigue and corrosion, but the Federal Aviation Authority failed to react to a Boeing Service Bulletin 737-53A1039 that alerted users that fatigue cracks had been detected on several different lap joints. The Federal Aviation Authority only required inspections on Lap joints S-4 left and right. Another contributing factor to this incident was the way the aircraft was being used hopping from island to island. Because of the number of take-offs, the repeated pressurization and depressurization of the aircraft which caused high stress on the fuselage, the salt water environment and humid climate all cause the aircraft to suffer high than normal metal fatigue on the lap joints. Upon further inspections by investigators of the Aloha Airlines B-737 fleet several other aircraft were showing the same kinds of stress cracking, corrosion, swelling and bulging of the skin, popped rivets and metal fatigue along the lap joints (Wrigley, 2018).
Metal fatigue plays a big role in the safe operation of all aircraft. This case study shows how insufficient testing, lack of good maintenance practices and the carelessness of the govern authority to properly act. Ultimately the National Transportation Safety Board determine the probable cause was the failure of Aloha Airlines maintenance program to detect disbonding and fatigue damage which led to failure of the lap joint at S-10L. The Federal Aviation Authority also failed to ensure Aloha Airlines maintenance program was sound in the areas of inspections. Also, the Federal Aviation Authority failed to react to the Boeing Alert Service Bulletin (Arruble, 2019). This incident could have been prevented but the proper govern authorities failed to act. As mentioned early this incident changed the way metal fatigue was looked.