Aloha Airlines 243

Abstract

On 28 April 1988, Aloha Airlines Flight 243 experienced structural failure and consequent explosive decompression at 24,000 ft. over the Pacific Ocean while en route from Hilo to Honolulu, HI. The flight crew enacted appropriate contingency procedures and was able to safely land the aircraft at Kahului Airport in Maui. During the event, an 18-ft. section of the fuselage skin had separated from the aircraft.

The study of this accident and the safety issues identified as a result are classic examples as to why safety programs are so important in the Aerospace Industry; particularly during the Operational Phase of an aircraftÐ'ÐŽÐ'¦s life cycle.

Some of the key safety issues identified are the execution of Aloha Airlines maintenance programs and their subsequent oversight by the Federal Aviation Administration (FAA), human factor aspects to include the repair procedures, training, management of, and qualifications of mechanics and inspectors, and the critical oversights during the design phase of the B737 by Boeing Aircraft Group (BAC).

Aloha Airlines Flight 243: An Accident Synopsis

On 28 April 1988, at 1346, a Boeing 737-200, tail number N73711, operated by Aloha Airlines identified as flight 243 (NTSB, 1989, Pg. i.) suffered a structural failure and explosive decompression at 24,000 ft. The aircraft was on its fifth flight of the day accomplishing the usual Ð'ÐŽÐ'§short hopsÐ'ÐŽÐ'Ё between the Hawaiian Islands en route form Hilo to Honolulu. There were two pilots, three flight attendants, a FAA observer in the jump seat, and eighty-nine passengers on board. At the moment of the rapid decompression, a flight attendant was literally sucked out of the fuselage and was never found and presumed dead. Seven passengers and one flight attendant suffered serious injuries. The rest of the souls on board were unharmed aside from the shock of the accident.

The flight crew was able to exercise the appropriate contingency procedures and land safely on the island of Maui. Issues during the descent and landing were the nose gear Ð'ÐŽÐ'§down and lockedÐ'ÐŽÐ'Ё light never illuminated, the number two engine failed, and numerous other losses of power. All these were later found to be due to severed and damaged wiring and other components caused by the structural failure.

Aircraft Damage

The National Transportation Safety Board (NTSB) conducted a physical investigation of the aircraft and found the following damage. A section of the upper crown skin and structure had separated causing the explosive decompression. The missing section extended 18 ft. from just aft of the forward hatch to just forward of the wing. The damage to the circumference of the fuselage started on the left side just below the seat line, and extended around the top of the fuselage to the right window area. See figures 1 & 2. Almost all of the floor beams in the area were severed and/ or raised as well. Evidence of preexisting cracks were found in numerous locations surrounding the failed area.

Figure 1. (NTSB, 1988, Pg. 6)

Figure 2. (www.airdisaster.com/photos/aloha243/6.html, 2006)

Facts About the Aircraft

The Boeing 737-200 was number 153 off the production line and was manufactured in 1969. Aloha Airlines was the original owner of the aircraft. The aircraft had an unusually high ratio of flight cycles to flight hours. The flight cycles were 89,680 and flight hours totaled 35,496. This was because AlohaÐ'ÐŽÐ'¦s operations consisted of Ð'ÐŽÐ'§short-hopÐ'ÐŽÐ'Ё flights between the Hawaiian Islands. The cycles to flight hour ratio for this aircraft, and the rest of AlohaÐ'ÐŽÐ'¦s fleet were inverse to aircraft being operated under normal conditions. Although the exact number is not known, it is certain that most of the aircraftÐ'ÐŽÐ'¦s cycles did not include reaching the 7.5 pressure differential that is normal under most operating situations. Simply put, Aloha never used the aircraft under the operating conditions for which its design was intended. This situation may have been identified and addressed had Aloha had a safety program in place.

Safety Matters

This type of failure is not an instantaneous event. Over time, stresses placed on a fuselage due to aerodynamic loads and pressurization cycles begins to wear on the lap joints where the outer skins of the fuselage meet. For an event of this magnitude to take place, it is obvious that many safety factors were either overlooked or not addressed.

The NTSB sites the following as the safety issues in this accident:

Ð'„h Engineering design, certification, and continuing airworthiness of the B737 with particular emphasis on multiple site fatigue cracking of the fuselage lap joints.

Ð'„h The quality of air carrier maintenance programs.

Ð'„h Human factors of the air carrierÐ'ÐŽÐ'¦s maintenance and inspection for continued airworthiness, to include repair procedures and the training, certification, and qualification of its mechanics and inspectors.

Ð'„h FAA surveillance of the air carrierÐ'ÐŽÐ'¦s maintenance programs.

(NTSB, 1988, Pg. v)

Boeing Aircraft Group

The information available regarding the design and subsequent redesign of the B737 fuselage lap joints is so extensive that it alone could be a term paper all its own. Every attempt is made here to summarize this information to show the major fault locations. Some important questions will also be raised about the effectiveness of traditional avenues manufacturers have to communicate instruction for continued airworthiness. We will also see a classic example of the difference between a safety program that operates to meet regulatory requirements and one that is a true system safety effort.

B737 production line numbers 1-291 lap joints were designed with inherent flaws. This was due to the fact that the cleaning and etching process used to prepare the joints for bonding was insufficient, along with a part of the joint piece being milled in sections that created a weakness at the joint. Boeing maintains that this design met certification requirements. The certification requirements are set forth on the Federal Aviation Regulations as minimum requirements for the design of aircraft under FAR 23 or 25 depending on