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Old 29th Oct 2017, 16:39
  #427 (permalink)  
slast
 
Join Date: Jan 2010
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Canadian DH rules

RAT 5, thanks, your comments are very appropriate.

JJA4, with all respect, the problem with Canadian minima is not the list of visual references, which is pretty common. It is what decision the rules expect the pilot to make.

The concept of Decision Height (ICAO and elsewhere) is that the pilot must answer Yes or No to the question "Has what you have already seen on the ground confirmed that you are in the right place and going in the right direction?", and continue or go around as appropriate. This is also written into for example the Airbus FCTM.

But Canada's rule (CAR 100.01(1) definitions) doesn't ask that. It poses a very different question: "is what you can see on the ground right now going to allow you to find out if you are in the right place and going in the right direction?". So the crucial decision is delayed to some undefined point in the future. ICAO requires the pilots assessment to finish at DH. Canada allows it to START there.

Under CAR, below DH the pilot has ceased to have sufficiently accurate instrument information to avoid obstacles, but as in this case he/she may still be assessing from visual information whether its position and velocity are satisfactory. The pilot eventually concluded that its position and trajectory were NOT safe and that a go-around was required, but by that time the aircraft was only just above the touchdown zone elevation and well below the altitude at which a go-around can safely be carried out. IMHO this difference was a direct cause of the accident.

In this case, when it was reached, well below the DH/MDA, the pilots' subsequent decision was "no our position and rate of position are not satisfactory, we need to go around", by which time it was too late to avoid ground impact.

While the report makes considerable play of Canadian non-compliance with ICAO and EASA rules regarding CVR power supplies, it makes no mention of the (far more serious) fact that CAR 100.01(1) is in direct conflict with both ICAO Annex 6 and EASA wording intended specifically to prevent this situation arising.
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