Birgenair Flight 301
TC-GEN, the aircraft involved in the accident, seen in 1995
|Date||6 February 1996|
|Summary||Stall caused by autopilot errors and pilot error, due to incorrect airspeed readings from blocked pitot tube|
26 km (14 nmi) NE of Puerto Plata, Dominican Republic |
|Aircraft type||Boeing 757-225|
Gregorio Luperón International Airport|
Puerto Plata, Dominican Republic
Gander International Airport|
Gander, Newfoundland and Labrador, Canada
Berlin Schönefeld Airport|
Birgenair Flight 301 was a flight chartered by Turkish-managed Birgenair partner Alas Nacionales from Puerto Plata in the Dominican Republic to Frankfurt, Germany, via Gander, Canada, and Berlin, Germany. On 6 February 1996, the 757-200 operating the route crashed shortly after take-off from Puerto Plata's Gregorio Luperón International Airport. All 189 people on board died. The cause was pilot error after receiving incorrect airspeed information from one of the pitot tubes, which investigators believe was blocked by a wasp nest built inside it. The aircraft had been sitting unused for two days without the pitot tube covers in place.
With 189 fatalities, Flight 301 is the deadliest aviation accident involving a Boeing 757, as well as the deadliest to occur in the Dominican Republic.
The aircraft was a Boeing 757-225 originally delivered to Eastern Air Lines in February 1985 and registered as N516EA. It was powered by two Rolls-Royce RB211-535E4 engines. After Eastern's bankruptcy and subsequent liquidation in 1991, the aircraft was stored at the Mojave Air and Space Port for more than a year. It was purchased by Aeronautics Leasing in April 1992, and then leased to Canadian airline Nationair in May 1992, and stayed with the airline until its demise the following year. It was leased again by the same lessor in July 1993 to Birgenair and then sub-leased to International Caribbean Airways in December 1994, and Birgenair operated the airframe until it crashed.
Passengers and crew
The crew consisted of 11 Turks and 2 Dominicans. The captain was Ahmet Erdem (62), one of Birgenair's most senior pilots,[not in citation given] with 24,750 flight hours under his belt. The first officer was Aykut Gergin (34). He had 3,500 hours of flying experience. The relief pilot was Muhlis Evrenesoğlu (51). He had 15,000 flight hours to his credit.
The passengers consisted mainly of Germans, along with nine Poles including two Members of the Parliament, Zbigniew Gorzelańczyk of the Democratic Left Alliance, and Marek Wielgus of the Nonpartisan Bloc for Support of Reforms (BBWR). Most of the passengers had booked Caribbean package holidays with Öger Tours; Birgenair held 10% of Öger Tours.
During takeoff roll at 23:42 AST (03:42 UTC), the captain found that his airspeed indicator (ASI) was malfunctioning but he chose not to abort the takeoff. The co-pilot's ASI was functional, though subsequent warning indicators would cause the aircrew to question its veracity as well.
As the plane was climbing through 4,700 feet (1,400 m), the captain's ASI read 350 knots (650 km/h). The autopilot, which was taking its airspeed information from the same equipment that was providing faulty readings to the captain's ASI, increased the pitch-up attitude and reduced power in order to lower the plane's airspeed. The co-pilot's ASI was giving a correct reading of 200 knots (370 km/h) and decreasing, yet the aircraft started to give multiple contradictory visible and audible warnings that it was flying too fast, including rudder ratio, Mach airspeed, and overspeed.
The autopilot reached the limits of its programming and disengaged. After checking the circuit breakers for the source of the warnings, the crew reduced thrust to lower the speed of the plane. This action immediately triggered the 757's stick-shaker stall alert, warning the confused pilots that the aircraft was flying dangerously slow, just seconds after the indicators had warned them that the speed was too high. The co-pilot and the relief pilot both seemed to recognise the approaching stall and tried to tell the captain, but did not intervene directly, possibly out of deference to the captain's age and experience. The captain attempted to recover from the stall by increasing the plane's thrust to full, but as the aircraft was still in a nose up attitude, the engines were prevented from receiving adequate airflow required to match the increase in thrust. The left engine flamed out, causing the right engine, which was still at full power, to throw the aircraft into a spin. Moments later, the plane inverted. At 23:47 AST, the Ground Proximity Warning System sounded an audible warning, and eight seconds later the plane crashed into the Atlantic Ocean. All 176 passengers and thirteen crew members died on impact.
Investigation and final report
The Dominican Republic government's Dirección General de Aeronáutica Civil (DGAC) investigated the accident and determined the probable cause to be:
"The crew's failure to recognize the activation of the stick shaker as a warning of imminent entrance to the stall, and the failure of the crew to execute the procedures for recovery from the onset of loss of control."
Investigations later showed that the plane was actually travelling at 220 knots (410 km/h; 250 mph) at the time of the accident. The investigation concluded that one of the three pitot tubes, used to measure airspeed, was blocked.
None of the pitot tubes were ever recovered so investigators were unable to determine for certain what caused the blockage. Investigators believe that the most likely culprit was the black and yellow mud dauber, a type of solitary sphecid wasp well-known to Dominican pilots, which tends to establish its nest in artificial, cylindrical structures, or make its own cylindrical nest out of mud. According to the final report, section 2.3 - "Aircraft maintenance factors", the aircraft had not flown in 20 days, however, this was not the duration for which pitots remained uncovered, but was evidently enough time to allow the wasps the opportunity to construct nests in the tubes. According to Cetin Birgen, president and CEO of Birgenair, the pitot covers were removed two days before the accident in order to conduct an engine test run.
The investigation noted a number of other factors and suggested changes. They reconfirmed that the pilots should have followed existing procedures and aborted the takeoff when they found that their airspeed indicators were already in significant disagreement as the plane accelerated down the runway. Results from a number of simulations with experienced pilots found that the combination of the overspeed warning horn and underspeed stick shaker while in flight was an overly confusing contradictory set of messages for many pilots; the FAA issued a directive that pilot training would now include a blocked pitot tube scenario. The FAA research had also revealed that the situation also led to multiple other contradictory warning sounds and warning lights that increased the demands on the pilot to fly the plane. The FAA asked Boeing to change some of those warnings, as well as add a new warning to tell both pilots that their instruments disagree, add the ability for the pilots to silence troublesome alarms, and to modify the system so that the pilots can choose which pitot tube the autopilot uses for airspeed readings.
Shortly after the crash of flight 301, the airline's overall image and profits became heavily damaged, and some of its planes were grounded at the same time. Birgenair went bankrupt in October of the same year as there were concerns about safety after the accident, causing a decline in passenger numbers. The crash and ensuing negative publicity both contributed to Birgenair's bankruptcy.
In popular culture
- The events of Flight 301 were featured in "Mixed Signals", a Season 5 (2007) episode of the Canadian TV series Mayday (called Air Emergency and Air Disasters in the U.S. and Air Crash Investigation in the UK and elsewhere around the world). The dramatization was broadcast with the title "The Plane That Wouldn't Talk" in the United Kingdom, Australia and Asia.
- The British television series Survival in the Sky featured the crash in its first episode, titled "Blaming the Pilot" (1996).
- Later the same year (1996), Aeroperú Flight 603, also operated with a Boeing 757, suffered a similar but far more difficult situation (static ports blocked by tape, rendering all airspeed indicators and pressure altimeters unusable) and crashed in the ocean off Peru, killing all 70 people aboard.
- Austral Líneas Aéreas Flight 2553
- Air France Flight 447
- Air India Flight 855
- XL Airways Germany Flight 888T
- Pope, Hugh. "Crash plane may not have been serviced." The Independent. Saturday 10 February 1996. Retrieved on 19 November 2009.
- "Rescuers call off search in plane crash." CNN. 8 February 1996. Retrieved on 19 November 2009.
- Accident description at the Aviation Safety Network. Retrieved on 21 July 2006.
- DGAC final report 1996, pages 4-8, section 1.5.
- Mike Clary (8 February 1996). "Dominican Jet Crashes in Sea; 189 Feared Dead". LA Times. Retrieved 25 February 2018.
- Karacs, Imre. "Bonn grounds 757 as crash mystery grows." The Independent. Friday 9 February 1996. Retrieved on 19 November 2009.
- DGAC final report 1996, page 1.
- "Mixed Signals". Mayday. Season 5. Episode 8. 2007. Discovery Channel Canada / National Geographic Channel.
- DGAC final report 1996, page 16.
- DGAC final report 1996, page 18.
- DGAC final report 1996, page 19.
- Tim van Beveren: Runter kommen sie immer, page 258–271, ISBN 3-593-35688-0 as filed with the US Library of Congress
- Walters, James M. and Robert L. Sumwalt III. "Aircraft Accident Analysis: Final Reports." McGraw-Hill Professional, 2000. p. 98. Retrieved from Google Books on 11 May 2011. ISBN 0-07-135149-3, ISBN 978-0-07-135149-2. "Souffront, Emmanuel T., Presidente, Junta Investigadora de Accidentes Aéreos (JIAA) of the Director General of Civil Aviation (DGAC) of the Dominican Republic. 1996. Aircraft accident information. Dominican Republic Press Release—Factual Information, 1 & 18 March 1996."
- "Erroneous airspeed indications cited in Boeing 757 control loss" (PDF). Flight Safety Foundation. October 1999. p. 2. Retrieved 27 August 2014.
It had not been flown for 20 days before the accident...Investigators believe that the engine [covers] and pitot covers were not installed before or after the engine ground test.
- DGAC final report 1996, page 20 (section 2.3). "Durante el tiempo que duró en tierra, dicho avión no fue volado en veinte (20) dias. Durante este periodo se ejecutó una inspección de motores que requirió una prueba en tierra del motor antes del despegue. Los investigadores creen que las cubiertas de los motores y cubiertas de los pitot no fueron instaladas antes ó después de la prueba en tierra de los motores."
- Birgenair comments 1996, pp. 16-17. "the aircraft was not on the ground for 20 days, but only for 12 days prior to the ill-fated flight. The pitot-tubes were covered prior to an engine test run which took place 2 days prior to the ill-fated flight. It was known by the BIRGENAIR mechanics that the airplane should be returned to Turkey in a ferry flight within the next 3 days. If therefore the pitot-tubes had not been covered after the engine test run for 2 days, according to the BOEING procedures, set forth in the BOEING Maintenance Manual, this might be justified." ... "Despite these irritating and even conflicting procedures set forth in BOEING's 757 Maintenance Manual and the Maintenance Planning Document, a blockage of the pitot-tube might occur even within any period of stay on the ground and [installation of pitot-covers] should therefore be clearly required for all periods of stay on the ground."
- Alfred Roelen: Causal risk models of air transport: comparison of user needs and model capabilities, page 39, ISBN 978-1-58603-933-2, IOS Press
- "Flying Blind." Mayday.
"Reporte Final Accidente Aereo Birgenair, Vuelo ALW-301, Febrero 06,1996" (PDF) (in Spanish). DGAC. 25 October 1996. Archived (PDF) from the original on 4 September 2014. Retrieved 27 August 2014.
|Pre-crash photos of the 757 carrying Flight 301 on Airliners.Net|
- Accident description at the Aviation Safety Network. Retrieved on 21 July 2006.
- (in Spanish) "REPORTE FINAL ACCIDENTE AEREO BIRGENAIR, VUELO ALW-301, FEBRERO 06,1996." (Archive). Dirección General de Aeronáutica Civil (Dominican Republic).
- (in German) "Bericht der Direccion General de Aeronautica Civil der Dominikanischen Republik über die Untersuchung des Unfalles mit dem Flugzeug Boeing B-757 am 06. Februar 1996 bei Puerto Plata." (Draft Final Report) – Dirección General de Aeronáutica Civil – Prof. Peter B. Ladkin, PhD obtained a copy from the Deutsche Luftfahrtbundesamt – His group digitised a copy sent by Karsten Munsky, a EUCARE Member in Berlin – Document prepared for the World Wide Web by Marco Gröning and Ladkin (Archive)
- (in Turkish) TC-GEN – Directorate General of Civil Aviation (Archive)
- CVR Transcript (Archive)
- Wald, Matthew L. ""German tourist plane crashes; 189 feared dead." The New York Times. 8 February 1996.
- Accident synopsis at Airdisaster.com
- Views of the memorial and list of victims' names (in German)