Representation of TC-GEN ascending prior to the crash. |
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| Accident summary | |
|---|---|
| Date | 6 February 1996 |
| Type | Compromised speed sensor (pitot tube) leading to autopilot and pilot errors |
| Site | 26 km (14 nm) NE of Puerto Plata, Dominican Republic |
| Passengers | 176 |
| Crew | 13 |
| Fatalities | 189 (all) |
| Aircraft type | Boeing 757-225 |
| Operator | Birgenair (Alas Nacionales) |
| Tail number | TC-GEN |
| Flight origin | Gregorio Luperón Int'l Airport Puerto Plata, Dominican Republic |
| 1st stopover | Gander International Airport Gander, Newfoundland and Labrador, Canada |
| 2nd stopover | Berlin Schönefeld Airport Berlin, Germany |
| Destination | Frankfurt Airport Frankfurt, Germany |
Birgenair Flight 301 was a flight chartered by Turkish-managed Birgenair partner Alas Nacionales ("National Wings") from Puerto Plata in the Dominican Republic to Frankfurt, Germany via Gander, Canada and Berlin, Germany. On 6 February 1996, the Boeing 757-225 operating the route crashed shortly after take-off from Puerto Plata's Gregorio Luperón International Airport.[1][2]
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The crew consisted of 11 Turks and 2 Dominicans. The passengers consisted mainly of Germans, along with a few Poles.[2] Most passengers had booked Caribbean package holidays with Öger Tours; Birgenair held 10% of Öger Tours.[3] In terms of passenger deaths, Flight 301 has the highest death toll of any aviation accident involving a Boeing 757.[4]
| Nationality | Passengers | Crew | Total |
|---|---|---|---|
| Germany | 167 | 0 | 167 |
| Poland | 9 | 0 | 9 |
| Turkey | 0 | 11 | 11 |
| Dominican Republic | 0 | 2 | 2 |
| Total | 176 | 13 | 189 |
Details of the crash have been revealed in the report of the Dominican Republic government's Dirección General de Aeronáutica Civil report and the Mayday television episode "Mixed Signals (The Plane That Wouldn't Talk)".
During takeoff roll at 11:42 p.m, the captain found that his air speed indicator (ASI) was not working properly, but chose not to abort takeoff[5]. The co-pilot's ASI was functional.
While the plane was climbing to 4,700 feet (1,400 m), the captain's ASI indicated 350 knots, which triggered a reaction from the autopilot, which was taking its air speed information from the same equipment that was providing faulty readings to the captain's ASI. The autopilot increased the pitch-up attitude and reduced power, both moves used to lower the plane's airspeed. The co-pilot's ASI read 200 knots and was decreasing, yet the airplane started to give multiple warnings that it was flying too fast, including rudder ratio, Mach airspeed and overspeed lights and sounds.
The autopilot had reached the limits of its programming, and disengaged. The crew checked the breakers for the warning lights and sounds, then pulled back on the thrust to lower the speed. The airplane instantly provided a stick-shaker warning, telling the pilots that the airplane was flying dangerously slow only seconds after it was warning them that the speed was too high, confusing the pilots, the co-pilot and the relief pilot both seemed to recognise that they were approaching a stall and both subtly tried to tell the Captain, however they did not intervene directly; possibly because they were nervous of overruling a Captain with far greater experience. The captain then tried to recover from the approaching stall by increasing the plane's thrust to full, but the plane was still in a nose up attitude, causing the engines to not receive adequate airflow to match the increase in thrust. The left engine suffered an engine stall, causing the still-operating right engine to throw the airplane into a spin; soon afterwards, the plane inverted.[6] At 11:47 p.m., the Ground Proximity Warning System sounded an audio warning, and eight seconds later the plane crashed into the Atlantic Ocean. All 13 crew members and 176 passengers died.
The Dominican Republic government's Dirección General de Aeronáutica Civil (DGAC) investigated the accident and determined the following probable cause for the accident:[7]
"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 at the time. The investigation concluded that one of three pitot tubes, used to measure airspeed, was blocked.
No tubes were recovered so investigators were unable to determine for certain what caused the blockage. Investigators suspected that some kind of insect could have created a nest inside the pitot tube. The prime suspect is a species called the black and yellow mud dauber wasp, well-known by pilots flying in the Dominican Republic. The aircraft had not flown in 25 days during which time the pitot tubes were not covered, giving the wasps an opportunity to build nests in the tubes.[5]
While the crash was attributed to the failure of the crew to execute the procedures for recovery, there were a number of incidental lessons learned.
The pilot's choice to go against protocol and execute takeoff despite his ASI clearly disagreeing with the co-pilot's ASI has resulted in protocols and training being further reinforced following this incident.
After the flight voice recorder revealed that the co-pilot and a third pilot on the flight deck had made relatively subtle suggestions to the pilot - once the stick-shaker warning commenced - that he must deal with the fact that the plane was still in a speed-draining nose-up attitude, protocols and training were reinforced to establish a greater willingness of junior flight-deck staff to be more forceful in similar situations. (In the Birgenair crash, it had even been revealed that the co-pilot chose not to use his own, active, stick to counter the pilot and try to bring the nose down.)
Later the same year (1996), Aeroperú Flight 603, also involving a 757, suffered from 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.[8]
In 1996 Birgenair went bankrupt.[9]
| External images | |
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| Pre-crash photos of the 757 carrying Flight 301 on Airliners.Net | |
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