Aloha Airlines Flight 243
Fuselage of Aloha Airlines Flight 243 after the explosive decompression.
|Date||28 April 1988|
|Summary||Explosive decompression caused by fatigue failure|
|Aircraft type||Boeing 737-297|
|Aircraft name||Queen Liliuokalani|
|Flight origin||Hilo Int'l Airport (ITO)|
|Destination||Honolulu Int'l Airport (HNL)|
Aloha Airlines Flight 243 (AQ 243, AAH 243) was a scheduled Aloha Airlines flight between Hilo and Honolulu in Hawaii. On April 28, 1988, a Boeing 737-297 serving the flight suffered extensive damage after an explosive decompression in flight, but was able to land safely at Kahului Airport on Maui. There was one fatality, flight attendant Clarabelle "C.B." Lansing, who was swept overboard from the airplane. Another 65 passengers and crew were injured.
The safe landing of the aircraft despite the substantial damage inflicted by the decompression established Aloha Airlines Flight 243 as a significant event in the history of aviation, with far-reaching effects on aviation safety policies and procedures.
The airframe, the 152nd Boeing 737 built, named Queen Liliuokalani after Lili'uokalani, with registration N73711, was built in 1969 and delivered to Aloha Airlines in spring of the same year as a brand-new aircraft. While the airframe had only accumulated 35,496 flight hours prior to the accident, those hours were over 89,680 flight cycles (a flight cycle is defined as a takeoff and a landing), owing to its use on short flights.
The flight departed Hilo at 13:25 HST on 28 April 1988 with six crew members and 89 passengers, bound for Honolulu. No unusual occurrences were noticed during the pre-departure inspection of the aircraft. The aircraft had previously completed 3 round-trip flights from Honolulu to Hilo, Maui, and Kauai that day, all uneventful. Meteorological conditions were checked but no advisories for weather phenomenon occurred along the air route, per Airman’s meteorological information (AIRMET) or significant meteorological information (SIGMET). The captain was 44-year-old Robert Schornstheimer. He was an experienced pilot with 8,500 flight hours; 6,700 of those were in Boeing 737s. The first officer was 36-year-old Madeline "Mimi" Tompkins. She also had significant experience flying 737s, having logged 3,500 of her total 8,000 flight hours in them.
No unusual occurrences were reported during the take-off and ascent. Around 13:48, as the aircraft reached its normal flight altitude of 24,000 feet (7,300 m) about 23 nautical miles (43 km) south-southeast of Kahului, Maui, a small section on the left side of the roof ruptured with a "whooshing" sound. The captain felt the aircraft roll left and right, and the controls went loose. The first officer noticed pieces of grey insulation floating over the cabin. The door to the cockpit was gone so the captain could look behind him and see blue sky. The resulting explosive decompression tore off a large section of the roof, consisting of the entire top half of the aircraft skin extending from just behind the cockpit to the fore-wing area.
First officer Madeline "Mimi" Tompkins was flying the plane at the time of the incident. After discovering the damage, the captain took over and steered the plane to the closest airport, on Maui island. Thirteen minutes later, the crew performed an emergency landing on Kahului Airport's Runway 2. Upon landing, the crew deployed the aircraft's emergency evacuation slides and evacuated passengers from the aircraft quickly. Tompkins assisted passengers down the evacuation slide. In all, 65 people were reported injured, eight seriously. At the time, Maui had no plan for a disaster of this type. The injured were taken to the hospital by the tour vans from Akamai Tours (now defunct) driven by office personnel and mechanics, since the island only had a couple of ambulances. Air traffic control radioed Akamai and requested as many of their 15-passenger vans as they could spare to go to the airport (three miles away) to transport the injured. Two of the Akamai drivers were former medics and established a triage on the runway. The aircraft was a write-off.
58 year old Flight Attendant Clarabelle Lansing was the only fatality; she was swept overboard while standing near the fifth row seats. Her body was never found. She was a veteran flight attendant of 37 years at the time of the accident. Eight others suffered serious injuries.
A section from behind the cockpit was separated equal to one-quarter of the fuselage length. All the passengers were in their seats and belted during depressurization. A major portion of the upper crown skin and fuselage structure of section 43 separated in flight causing an explosive decompression of the cabin. Final damage consisted of the total loss of a portion of the upper crown skin, and damage to other fuselage structure and walls in section 43. Damage extended from aft of the main cabin entrance door, rearward about 18.5 feet (5.6 m). As a result of the accident, the airplane was determined to be damaged beyond repairs. It was dismantled on-site. Additional damage to the airplane included damaged and dented horizontal stabilizers, both of which were struck by flying debris. Some of the metal debris also struck the aircraft's tail fin, causing little damage. The leading edges of both wings and both engine cowlings were also damaged and dented. 
Despite an extensive search of the ocean at the estimated location of the incident, neither Lansing's body nor the piece of the fuselage that was blown off the plane were ever found. Investigation by the United States National Transportation Safety Board (NTSB) concluded that the accident was caused by metal fatigue exacerbated by crevice corrosion. The plane was 19 years old and operated in a coastal environment, with exposure to salt and humidity.
According to the official NTSB report of the investigation, Gayle Yamamoto, a passenger, noticed a crack in the fuselage upon boarding the aircraft prior to the ill-fated flight but did not notify anyone.
For the production line number 291 (B-737) and prior (this aircraft was production line number 152), the outer layer was not present. In the case of production line 292 and after, this outer layer was retained, to give an additional thickness of .036 inch at the joint. In airplane line number 291 and before, cold bonding had been utilized, with fasteners used to maintain surface contact in the joint, allowing bonding adhesive to carry/transfer load between skin panels. This cold bonded joint used an epoxy-impregnated woven scrim cloth to join the edges of .036 inch skin panels. These epoxy cloths were reactive at room temperature, so they were stored at dry ice temperatures. The bond cured at room temperature after assembly. The cold bonding process reduced the overall weight and manufacturing cost. Fuselage hoop loads (circumferential pressurization loads) were intended to be transferred through the bonded joint, rather than through the rivets, allowing the use of lighter, thinner fuselage skin panels with no degradation in fatigue life.
The additional outer layer construction improved the known problems with the joint by:
- Eliminating the knife-edge fatigue detail, which resulted from the countersunk rivets in a disbonded upper skin;
- Eliminating the corrosion concern associated with the scrim cloth, which could wick moisture into the lap joint 
Pressure vessel engineer Matt Austin has proposed an alternative hypothesis to explain the disintegration of the fuselage of Flight 243. This explanation postulates that initially the fuselage failed as intended and opened a ten-inch square vent. As the cabin air escaped at over 700 mph, flight attendant C.B. Lansing became wedged in the vent instead of being immediately thrown clear of the aircraft. The blockage would have immediately created a pressure spike in the escaping air, a fluid hammer (or "water hammer"), which tore the jet apart. The NTSB recognizes this hypothesis, but the board does not share the conclusion and maintains its original finding that the fuselage failed at multiple points at once. Former NTSB investigator Brian Richardson, who led the NTSB study of Flight 243, believes the fluid hammer explanation deserves further study.
The investigation determined that weather had no role in this accident. The quality of inspection and maintenance programs were deficient. Also, the fuselage failure initiated in the lap joint along S-10L; the failure mechanism was a result of multiple site fatigue cracking of the skin adjacent to rivet holes along the lap joint upper rivet row and tear strap disbond which negated the fail-safe characteristics of the fuselage. Finally, the fatigue cracking initiated from the knife edge associated with the countersunk lap joint rivet holes; the knife edge concentrated stresses that were transferred through the rivets because of lap joint disbonding.
Under current FAA regulations for the Boeing 737 (line number 291 and prior) established in the 2010s, this airframe would have had to be permanently withdrawn from service after 34,000 flight cycles or 34,000 hours, whichever came first (for production number 292 and higher, it was increased to 75,000 flight cycles and 100,000 hours). The nearly 90,000 flight cycles exceeded the design limit of the 737-100/200 under either construction model.
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- Uncontrolled decompression
- List of notable decompression accidents and incidents
- List of accidents and incidents on commercial airliners
- Air safety
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