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Analyzing the Descending Flight of the Germanwings A320 4U9525 on 2015-03-24

Something (on 2013-03-26, 10:00 still unknown *) caused 4U9525 to descent. All the rest is the automatic reaction of a properly functioning Airbus A320 to these initial conditions: The aircraft is disconnecting the autopilot automatically at a Mach number of 0.82 as a consequence of High Speed Protection and follows a subsequent descending flight in manual mode (with normal Fly-by-Wire flight control laws) and idle thrust. The pilot(s) probably are/is neither touching the side stick nor the thrust levers. At least, it does not need any pilot intervention to explain the cause of the last 9 minutes of the flight and the final tragic effect.

Within a few hours an Engineering Note was written and published Open Access:

Engineering Note:
http://dx.doi.org/10.6084/m9.figshare.1356060 - PDF: Text
http://dx.doi.org/10.6084/m9.figshare.1356061 - XLS: Calculations
http://dx.doi.org/10.6084/m9.figshare.1356062 - All files in Dataset

* New information:
2015-03-26, 12:35: "Between 09:30:52 UTC and 09:30:55 UTC we can see that the autopilot was manually changed from 38,000 feet to 100 feet and 9 seconds later the aircraft started to descend" (http://forum.flightradar24.com).
Remark: This recording provided ends at 09:31:19 UTC with the autopilot still in the same mode at this time. Only later at 09:32 UTC aircraft may have reached M = 0.82 to disconnect the autopilot.

2015-03-26, 15:00 sagt Lufthansa-Chef Carsten Spohr in einer Pressekonferenz, dass "... das Flugzeug offensichtlich willentlich zum Absturz gebracht wurde, mutma▀lich durch den Copiloten ...".

2015-03-28: New flight data awailable from FlightRadar24. Tailwind component is between 15 kt and 30 kt. This changes some results from my calculation: a) MMO may not have been reached, but later in descent VMO may have been reached with the same consequence to disconect the autopilot. b) Measured L/D is now even closer to that calculated from aerodynamics (see link to XLS above). This rules out the speed brakes to be deployed and would rule out a (complete) emergency descent procedure to have been initiated (e.g. due to depressurization).

This sound should be audible on the cockpit voice recorder:


More from what must be (similar) on the cockpit voice recorder:

2015-04-03: "The initial readout shows that the pilot present in the cockpit used the autopilot to put the aeroplane into a descent towards an altitude of 100 ft then, on several occasions during the descent, the pilot modified the autopilot setting to increase the speed of the aeroplane in descent." (BEA Information on 3 April 2015)
Remark: The autopilot commands the CAS. This speed, the CAS, increase by itself as alitude is reduced. The autopilot has no authority to increase speed above VMO. According to Data awailable from FlightRadar24, TAS decreases as VMO is reached.


STAND:  13 April 2015
AUTHOR:  Prof. Dr. Scholz
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