Tuesday, June 19, 2012

Airbus’s Strategy for automation of Pilot functions.


Airbus is the leading manufacturer of commercial airplanes has long been supported for automating cockpit functions which allowed them to cut the fuel costs and also minimize pilot errors. Airbus is currently working on a feature which allows commercial airplanes to automatically change altitude during the cruise phase. Currently, pilots are faced with multiple false warnings from the Traffic Collision Avoidance system. The TCAS is a feature that enables transponders in a plane to detect similar signals from a near-by plane to avoid collision. Generally, the TCAS will ask one of the plane to go up and the other plane to go down. The warning sound will voice “Traffic,Traffic” when the planes are lower than 1000 ft separating each other.
Reviewing the warnings and taking the necessary action is up to the pilot. But a large number of false warnings would mean the pilot’s workload is suddenly increased in case of such events. Further, it causes significant distraction for the pilots and might require unnecessary emergency procedures to be taken.


The new features that Airbus has created will automatically determine if action should be necessary to prevent the collision and change the attitude in response. Further, it requires only one of the two airplanes to have the system to avoid collision. In 2002,a Bashkiran airlines carrying a group of school children collided with a DHL cargo jet in Uberlingen, Germany. This was caused by conflicting commands from the Air Traffic Controller (ATC) and the TCAS. The ATC who was working for multiple aircrafts asked the Russian plane on the collision course to move down while TCAS warned it to move up. The other plane followed the TCAS and moved down. The Russian following the ATC’s order moved down and collided with the other plane which was also moving down killing everyone on-board. The standard procedure in these cases is to follow TCAS RA over ATC’s orders. But the automation computer voice is computerized and pilots reacted to a more human-like voice from the ATC.Again in such cases, The new automation system will automatically change the altitude without waiting for the pilots to take actions.



Similar scenarios have happened with Boeing planes as well.In another incident, at Amsterdam Schipol Airport a Turkish plane Boeing 757 had a altimeter failure which showed an altitude of -8 when it was above 1000 feet during the landing procedure. The pilots failed to realize the consequence of such a failure, and they just silenced the alarm which sounded. They went ahead with the landing checklist while the auto throttle (which automatically changes the engine power) took the information from the faulty altimeter. Coincidentally, the pilots slowed the plane down to reach the glide slope and the throttle moved towards low power mode, and then went further behind to landing mode (zero power) thinking the aeroplane was on ground. The previous occasions when this incident happened, pilots noticed the throttles moving behind when the plane was required to maintain the same speed but this time pilots failed notice as they thought it was going behind to slow the aircraft. Finally, the aircraft slowed down too much and the pilots failed to notice this till the aero plane stalled. Since it was a low altitude stall, recovery (diving to gain airspeed, and lift over wings) was impossible and the plane crashed killing all the pilots.Currenly,the design of Airbus/Boeing aircrafts are being improved to stop automation when one of the connected input sources fail.



Airbus is also working on automatic laterally offset emergency descent in case of cabin depresurization when the pilots do not react within the decision time frame. This will reduce air crashes like the Helios crash over Greece wherein the cabin pressure decreased slowly to incapacitate the pilots (and the passengers) and the plane few in autopilot, until it ran out of fuel and crashed.

Airbus Strategy when there is a failure in any of the components (failure modes):

There is growing concern that the automated systems will fail in unanticipated ways. The airbus automation systems switch the aircraft to alternate mode which allows the pilot to make higher rudder and aileron inputs to control the aircraft.There are two types of alternate mode.

(i)                  In Alternate mode 1, the load factor and bank angle protection are retained while high angle of attack protection is lost.
(ii)                In Alternate mode 2, the lateral mode, pitch altitude and bank protection is lost while the speed and angle of attack protection is retained.

The probability of any instrument failing in an aircraft is very very low. Even when it happens the automation is designed in such a way so that the pilot has control over the aircraft using the alternate mode.

Sources:
Airbus to Make Cockpit Changes:
http://online.wsj.com/article/SB10001424052748703867704576183004041750590.html

Uberlington Mid-Air Collision
http://www.waymarking.com/waymarks/WM1FPM_berlingen_Mid_air_Collision





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