Today In History: 6 Feb 1996 The Crash of Birgenair Flight 301
On February 6, 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 20 days, and without pitot tube covers in place for the preceding 2 days before the crash.
Flight 301 shares the title of deadliest aviation crash involving a Boeing 757 alongside American Airlines Flight 77, both having 189 total fatalities. Furthermore, Flight 301 is the deadliest aviation accident ever to have occurred in the Dominican Republic.
During takeoff roll at 23:42 AST (03:42 UTC),[7]: 1 the captain found that his airspeed indicator (ASI) was malfunctioning but he chose not to abort the takeoff. The first officer’s ASI was functional, though subsequent warning indicators would cause the aircrew to question its veracity as well. The aircraft took off normally at 23:42 AST, for the first leg of the flight. At 2,500 feet (760 m), the flight switched to main air traffic control and was instructed to climb to flight level 280 (28,000 ft or 8,500 m). The autopilot was engaged 1 minute and 30 seconds into the flight.
Approximately 10 seconds later, two warnings: rudder ratio and Mach airspeed trim appeared. The crew was at that point becoming increasingly confused, because the captain’s ASI showed over 300 knots (560 km/h; 350 mph) and was increasing and the first officer’s ASI, which was correct, was showing 220 knots (410 km/h; 250 mph) and decreasing.
Then, the captain assumed that both ASI are wrong, and decided to check circuit breakers. When the first circuit breaker was checked, the overspeed warning appeared, as the captain’s ASI, the primary source of the information about airspeed for autopilot, was showing airspeed near 350 knots (650 km/h; 400 mph) and increasing. Then, the second circuit breaker was pulled to silence the warning. As the plane was climbing through 4,700 feet (1,400 m), the captain’s ASI read 350 knots (650 km/h; 400 mph). 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 first officer’s ASI was giving a correct reading of 200 knots (370 km/h; 230 mph) and was still decreasing.: 16 With all contradictory warnings given by the plane, the confused captain decided to reduce thrust of the plane, believing it was flying too fast.: 18
This action immediately triggered the 757’s stick-shaker stall alert, warning the confused pilots that the aircraft was flying dangerously slow. Also, the autopilot disengaged. As the plane was closing to stall, its path became unstable and it started descending. Meanwhile, the controller, still unaware of any problems, called the flight, but, as the crew struggled with problems, the first officer said “Standby”. First officer and relief pilot, aware of the scale of the problem, were suggesting various methods to recover from the stall, but the confused captain ignored all of them. About 20 seconds before crash, the captain finally 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 (GPWS) sounded an audible warning, and eight seconds later the plane crashed into the Atlantic Ocean. All 176 passengers and 13 crew members died on impact.
Source: Wikipedia
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