Many crashes in the past could’ve been easily avoided but once it’s done it’s done, and the only thing we could do now is to learn from those mistakes. On February 6th, 1996, a Boeing 757-225 crashed into the open sea. Why did it crash and how could it have been avoided?

It was February 6th, 1996, Boeing 757-225 Birgenair Flight 301 crashed, resulting in the death of 176 passengers and 13 crew members. It crashed almost immediately after takeoff in the Dominican Republic. The problem was with the airspeed indicator, but what made the airspeed indicator malfunction?

The aircraft was not in use for 20 days and 2 days prior to the crash, the pitot tubes were uncovered. Unknown to the pilot, one of the three pitot tubes was blocked. Proceeding with the flight, during takeoff the captain realized his airspeed indicator was malfunctioning but he still chose to continue the flight disregarding it as a major issue.

As the plane was climbing to the cruise altitude, the captain’s ASI read 350 knots. The autopilot, which was taking its airspeed information from the same equipment that was giving wrong readings to the captain’s airspeed indicator, increased the pitch-up attitude and reduced power in order to lower the plane’s airspeed. The co-pilot’s airspeed indicator (ASI) was giving a correct reading of 200 knots and decreasing, yet the aircraft started to give multiple contradictory visible and audible warnings that it was flying too fast.

The Captain understood that something was majorly wrong and assumed that both ASI readings were incorrect whereas the first officer’s airspeed indicator was working perfectly well. At this point, the aircraft was flying at a dangerously low speed, but the Captain believing they were going too fast, he pulled back on the throttle, causing the control to shake and give a warning that the aircraft was about to stall. What he should’ve done was lower the nose to increase the speed, but since he didn’t, the autopilot deactivated giving the captain full control so he could prevent the stall, unfortunately, it was too late, and the plane didn’t have enough airflow over the wings. Then by applying full power from that angle, the left engine quit and with the right engine at full acceleration, the plane went into a full stall. The pilots couldn’t do anything to prevent what had happened. The plane went crashing down into the Caribbean Sea killing everyone on board.

We understood that the pitot tube was blocked, but what caused the blockage? it is believed to be the mud dauber wasp, a type of insect that is known in the Dominican Republic. It turns out a pitot tube is a perfect home for the wasps. Investigators concluded that mud dauber wasps blocked the uncovered Pitot tubes which fed the captain’s airspeed indicator and caused it to malfunction. Ironically though these types of wasps are known as being harmless to people and they rarely sting.

Resources

https://www.computerweekly.com/news/1280096929/Crash-One-Birgenair-Flight-301