How aerodynamic stall occurs

January 7, 2015

Today divers identified the tail of AirAsia flight QZ8501, providing a glimmer of good news as the search and recovery mission for the Airbus A320-200 and the 162 passengers aboard continues. The tail is of particular importance, as it houses the Flight Data Recorder (FDR) and the Cockpit Voice Recorder (CVR)—known as the “black box”—both of which contain data critical to piecing together the plane’s final moments.

Ground crews lost contact with the plane over the Java Sea about 40 minutes into a flight from Surabaya to Singapore. A Boeing study (PDF) noted that of the 72 fatal air disasters to befall the worldwide commercial jet fleet from 2004 to 2013, just under 10 percent occurred while the plane was at cruising altitude, and investigators are studying whether the plane  the plane stalled after taking an “unbelievably” steep climb to avoid bad weather

The theory aligns with both data from the ground and the rules of aerodynamics. As this Reuters graphic shows, smooth airflow diminishes as the angle of attack (the angle of the wing to the airflow) increases, causing eddies of air to form, and ultimately stalling the aircraft as the swirling air above the airfoil takes the place of lift. Essential information from the FDR and the CVR would help investigators confirm this as the cause of the crash of QZ8501.

AerodynamicStall010715-620

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There are nearly always, very strong up and downdrafts near the big storms they were driving into, as well as sometime “clear tornadoes in the saddles between storms”. Those things can move any acft about, stall or whatever and often impossible to “climb above”. Anytime anyone goes into those areas the real risk exists.

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