Re: [SystemSafety] Chicago controller halts Delta jet's near-miss....

From: Peter Bernard Ladkin < >
Date: Sat, 27 Jun 2015 09:50:45 +0200

Hash: SHA256


there are a few things wrong with your conception of ATC-aircraft relations. The major one is

On 2015-06-27 08:48 , Les Chambers wrote:
> ATC/pilot take off protocol is a master slave protocol.

Most definitely it is not.

ATC clears airspace for the aircraft, and communicates which airspace is cleared. The aircraft acknowledges the clearance if it intends to fly according to it, and rejects it if not. The captain/commander of the aircraft is the sole authority over the conduct of the flight, and that is enshrined in most countries' law.

That said, decisions on either side may be questioned, as may failure to follow a correctly acknowledged clearance, or to communicate flown deviations from the clearance.

There is 80+ years of development, experience and law behind all this. It is pretty robust. Airproxes are at the 10^6 level or less per movement, and the large majority of those are with aircraft that are not under positive control (that is, are flying in airspace nominally cleared for them by ATC). I believe a significant proportion of those which occur under positive control of both aircraft involve aircraft not flying their clearance. That was the case in the Midway incident.

I understand it's worthwhile to investigate incidents and what they might say about operations, including the protocols. GB, for example, has a Board that does that and reports regularly, and other ANSPs have their equivalents. It's helpful to know the state of the practice!

PBL Prof. Peter Bernard Ladkin, Faculty of Technology, University of Bielefeld, 33594 Bielefeld, Germany Je suis Charlie
Tel+msg +49 (0)521 880 7319

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systemsafety_at_xxxxxx Received on Sat Jun 27 2015 - 09:50:54 CEST

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