PPRuNe Forums - View Single Post - BREAKING NEWS: airliner missing within Egyptian FIR
Old 4th Nov 2015, 08:31
  #800 (permalink)  
silverstrata
 
Join Date: Mar 2010
Location: L.A.
Age: 52
Posts: 561
Flightradar data:

Quote:
The altitude value is derived via a pressure sensor, which can be affected by changes in pressure outside the aircraft. In this case, what we’re learning about the state of the airframe calls into question the validity of the altitude readings during this time period.

I think that what they mean here, is that if the aircraft had started tumbling, disturbing the airflow over both pitots and static ports, then both the altitude and airspeed transmitted will be unreliable.

In which case the Flightradar data may suggest that the aircraft lost control in the climb-cruise phase, and not in the descent. So the loss of control was immediate and catastrophic, and was the cause of the sudden descent.

Silver

P.S.
From the data-graph posted by Peekay4 in post 509, we see four data extremes within 12 seconds. If the data excursions were caused by airflow disturbances over the pitot and static ports, this could well indicate that the aircraft was rotating in pitch or yaw (or oscillating in pitch or yaw), every 3 seconds.

There was a video earlier of a Russian transport aircraft crashing, because of a loss of tail surfaces, and that was almost managing a 3 second rotation. Rapid pitch or yaw motion (without changing the altitude significantly) to disturb the pitot-static system could be achieved by a loss of tail surfaces, or by runaway computers/hydraulics. I am thinking of that 747 that had runaway pitch commands to the elevators on take off from Heathrow, many Moons ago. An elevator actuator had a transient oscillating glitch, but the other actuator kept the aircraft more or less stable.

Silver

Last edited by silverstrata; 4th Nov 2015 at 08:45.
silverstrata is offline