Archives For RPD

TCAS and Tenerife

05/10/2014

Tenerife disaster moments after the impact

TCAS, emergent properties and risk trade-offs

There’s been some comment from various regulator’s regarding the use of Traffic Collision Avoidance System (TCAS) on the ground, experience shows that TCAS is sometimes turned on and off at the same time as the Mode S transponder. Eurocontrol doesn’t like it and is quite explicit about their dislike, ‘do not use it while taxiing’ they say, likewise the FAA also states that you should ‘minimise use on ground’. There are legitimate reasons for this dislike, having too many TCAS transponders operating within a specific area can degrade system performance as well as potentially interfering with airport ground radars. And as the FAA point out operating with the AD-B transponder on will also ensure that the aircraft is visible to ATC and other ADS-B (in) equipped aircraft (1). Which leaves us with the question, why are aircrew using TCAS on the ground? Is it because it’s just easy enough to turn on at the push back? Or is there another reason?

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From the BEA’s second interim report (BEA 2009) we now know that AF 447 was flown into the water in a deep stall. Given the training and experience of the flight crew how did they end up in such a situation?

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Recent incidents involving Airbus aircraft have again focused attention on their approach to cockpit automation and it’s interaction with the crew.

Underlying the current debate is perhaps a general view that the automation should somehow be ‘perfect’, and that failure of automation is also a form of moral failing (1). While this weltanschauung undoubtedly serves certain social and psychological needs the debate it engenders doesn’t really further productive discussion on what could or indeed should be done to improve cockpit automation. So let’s take a closer look at the Airbus protection laws implemented in the flight control automation and compare it with how experienced aircrew actually make decisions in the cockpit.

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