Buzz
On April 3rd, a Malaysia Airlines Boeing 737-800 unexpectedly loses altitude 30 minutes after departing from Kuala Lumpur. Despite the pilots managing to regain control and safely land at KLIA, the incident leaves many passengers shaken. Initial investigation results indicate a malfunctioning pitot-static system as the cause of the altitude loss.
The Boeing 737-800 is reported to have descended 7000 ft (over 2100 m) from its cruising altitude of 31000 ft (approximately 9500 m) to 24000 ft (around 7300 m) within 13 minutes. Additionally, the aircraft is said to have encountered severe turbulence. A female passenger recounts floating above her seat as she had not fastened her seatbelt at the time (the seatbelt sign was off).
After analyzing data extracted from the Flight Data Recorder (FDR), Malaysia's Civil Aviation Authority (CAAM) identified a malfunction in the aircraft's pitot-static system. Chester Voo, CEO of CAAM, stated on April 10th: 'The malfunction from this system provided erroneous speed data, causing the aircraft to perceive a stall and automatically disengage the autopilot while pitching the aircraft up. In response to the aircraft's automatic behavior, the pilots immediately made adjustments to regain control.'
The pitot-static system is a set of pressure measuring devices consisting of pitot tubes, static ports, and it helps determine the aircraft's speed, Mach number, altitude, and climb rate. Data from this system is fed into the aircraft's onboard computer, the FDR, altitude decoder, cabin pressure system... and any discrepancy in this system poses a danger as it sends inaccurate information to the computer and pilots, thus affecting the functionality of related systems as well as the pilots' reactions.
Malfunctions in the pitot-static system can lead to disasters. Malaysia Airlines itself faced an incident with pitot tubes in 2018 when an Airbus A330 took off from Brisbane International Airport to Kuala Lumpur with its red protective cover attached, bearing a warning tag that it needed to be removed before flight. However, both the pilots and ground technicians overlooked it (pictured above is Malaysia Airlines' A330 being towed out of the gate with the pitot tube protective cover still intact). Though this incident fortunately didn't turn into a disaster, history has seen horrific air accidents related to pitot tubes.
For instance, in 1996, a Birgenair Boeing 757-225, operating flight 301 from Puerto Plata, Dominican Republic to Frankfurt, Germany, crashed shortly after takeoff, resulting in the loss of 189 lives on board. The cause was determined to be pilot mishandling after receiving erroneous speed information from the pitot tubes. The inaccuracy of the Boeing 757's pitot tube was due to bees nesting inside it while the aircraft was parked at Gregorio Luperón Airport in Puerto Plata for 20 days without the protective cover.
Similarly, also in 1996, an Aeroperu Boeing 757-23A, operating flight 603 from Miami, Florida to Santiago, Chile, crashed near Huarai, Peru, claiming 70 lives. The pitot-static system on the aircraft provided incorrect speed and altitude information, leading the pilots to make errors. Investigators eventually found adhesive tape remaining on the static ports, which are responsible for measuring air pressure (pictured above). During aircraft maintenance, a technician used tape to protect the static ports but later forgot to remove it.
One of the most recent and well-known incidents is the crash of Air France Flight 447. The Airbus A330 disappeared over the Atlantic Ocean with 228 people on board while en route from Rio de Janeiro, Brazil, to Paris, France. It wasn't until 2011 that the black boxes of this aircraft were found, and the French Civil Aviation Safety Authority (BAE) concluded that ice crystals had formed inside the pitot tubes due to external atmospheric conditions, providing inconsistent speed information between the two pitot tubes, causing the autopilot to disengage automatically. The crew also reacted incorrectly by not following proper procedures in the situation of inconsistent speed information, resulting in the aircraft stalling.
Source: SimpleFlying
