Birgenair Flight 301

Birgenair Flight 301 was a chartered flight 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 Boeing 757 operating the route crashed shortly after take-off from Puerto Plata's Gregorio Luperón International Airport, killing all 189 people on board. 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 two days preceding the crash.

Flight 301 is tied with American Airlines Flight 77 as the deadliest aviation incident involving a Boeing 757, having a total of 189 fatalities. Furthermore, Flight 301 is the deadliest aviation accident ever to have occurred in the Dominican Republic.

Accident

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 first officer's ASI was functional, though subsequent warning indicators caused 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 2500 ft, the flight switched to main air traffic control and was instructed to climb to flight level 280 (28,000 ft). 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 kn and increasing, and the first officer's ASI, which was correct, was showing 220 kn and decreasing.

Then, the captain assumed that both ASI were wrong and decided to check the 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 kn and increasing. Then the second circuit breaker was pulled to silence the warning. As the plane was climbing through 4700 ft, the captain's ASI read 350 kn. 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 kn and was still decreasing. With all contradictory warnings given by the plane, the confused captain decided to reduce thrust of the plane, believing it was flying too fast.

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 close to a 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, "Stand by". The 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. There were no survivors.