Garuda Indonesia Flight 421
|Date||January 16, 2002|
|Summary||Flameout of both engines in heavy rain/hail|
|Site||Bengawan Solo River
|Fatalities||1 (flight attendant)|
|Aircraft type||Boeing 737-3Q8|
|Flight origin||Selaparang Airport, Ampenan, Indonesia|
|Destination||Adisucipto International Airport, Yogyakarta, Indonesia|
Garuda Indonesia Flight 421 was a scheduled domestic flight operated by Indonesian flag carrier Garuda Indonesia travelling about 625 km (388 mi) from Ampenan to Yogyakarta. On January 16, 2002, the flight encountered severe thunderstorm activity during approach to its destination, suffered flameout in both engines, and ditched in a shallow river, resulting in one fatality and several injuries.
The aircraft, a Boeing 737-3Q8, registration PK-GWA, was manufactured in 1988 and delivered in 1989. It was the first 737 flown by Garuda Indonesia.
As the Boeing 737-300 aircraft was on approach to its destination, the pilots were confronted with substantial thunderstorm activity visible ahead and on their onboard weather radar. They attempted to fly between two intense weather cells visible on their radar. They later entered a thunderstorm containing heavy rain and hail. About 90 seconds later, as the aircraft was descending through 19,000 ft (5,800 m), both CFM International CFM56 engines experienced a flameout, which resulted in the loss of all generated electrical power. Both engines were set at their flight-idle power setting before flameout occurred. The crew tried unsuccessfully to restart the engines two or three times. They then tried but failed to start the auxiliary power unit (APU), at which time total electrical power loss occurred. (During the later investigation, the NiCd battery was found to have been in poor condition due to inadequate maintenance procedures.) The co-pilot attempted to transmit a Mayday call, but was unable. As the aircraft descended through the lower layer of clouds at approximately 8,000 ft (2,400 m), the pilots saw the Bengawan Solo River and decided to attempt to ditch in the river with the flaps and gear retracted. The ditch procedure was successful, leaving the aircraft settled down on its belly in the shallow water, with the fuselage, wings and control surfaces largely intact. There was no fire.
Evacuation and rescue
Only two doors were available for evacuation. Residents of nearby villages assisted. Uninjured passengers and their personal belongings were temporarily sheltered in a nearby empty house, while injured passengers were transported by an available vehicle to the nearest clinic. After evacuation, the pilot contacted the Jogia Tower via cellphone and reported the emergency landing and location. The rescue team arrived about two hours later and all remaining passengers and crew were taken safely to a hospital.
Aircraft damage and injuries
There was severe damage to the submerged aircraft belly, especially near the tail, leading to the inference that it landed nose high with tail impacting the shallow river bed, which ripped away the cabin floor together with the two flight attendants seated there. Both were found with severe injuries in the river behind the aircraft, and one did not survive. Twelve passengers suffered injuries, while the flight crew and two other flight attendants were uninjured. The aircraft was written off as a total loss.
NTSC investigation and report
The final report of the Indonesian National Transportation Safety Committee (NTSC) notes that pilot training in the interpretation of weather radar images was not formal, being given only during flight training. It is considered possible that the precipitation was so dense that it attenuated the radar signals, reducing the reflections that usually indicate precipitation and making such high density appear to be a clearer path. Had the crew manipulated the radar tilt to sweep the ground during descent, they would have been aware of the risks associated with the chosen flight path. Intense noise audible in data from the cockpit voice recorder as well as damage to the nose radome and engines indicate the presence of hail with the rain. The report concludes that the hail/water density exceeded the engine tolerance at flight idle, resulting in flameout.
Remarks by U.S. NTSB
A later Safety Recommendation letter from the U.S. NTSB to the FAA notes that analyses of flight recorder data and weather satellite images indicate that the aircraft had already entered a thunderstorm cell at the start of the diversion to avoid the storm. It also notes that the procedure recommended in the Boeing 737 Operations Manual to respond to a dual flameout is to first start the APU (which could then provide much more power to start the main engines). Furthermore, repeating a comment in the NTSC report, the letter notes Boeing's advice that, in moderate to severe rain, starting main engines can take up to three minutes to spool up to idle, whereas the pilots allowed only one minute before initiating another retry. The letter recommends to the FAA that pilots be advised to maintain a higher engine power level in moderate to severe precipitation to avoid flameout.
- Emergency landing
- Southern Airways Flight 242 - Similar incident
- US Airways Flight 1549
- Water landing
- TACA Flight 110 - Similar incident
- Garuda Indonesia PK-GWA (Airfleets). Retrieved: 20 May 2013.
- "Final Indonesia NTSC Report GA421 B737 PK-GWA Solo" (PDF). Indonesia National Transportation Safety Committee. 2002-01-16. Retrieved 2013-03-02.
- "Safety Recommendation, August 31, 2005" (PDF). National Transportation Safety Board. Retrieved 2010-05-13.
- Final report - National Transportation Safety Committee (Archive)
- Safety Recommendation - National Transportation Safety Board
- Aviation Safety Network accident description