MDA

[PEI_3721]

Aterpster, - risk assessments, #24.
IIRC such an assessment was undertaken by a European research organisation – NLR ??
With fading memory, a conclusion was that was a slightly increased risk in using MDA as DH, i.e. accepting a small transgression below MDA. The risk was quantified and compared predominantly with the risk / benefit of ‘dive and drive’ NPAs (higher risk) vs a continuous descent/DH (reduced risk). I also recall some reference to the ICAO collision risk model.
I did have a copy of the document / presentation – searching my archives after a house move.

The issue was debated by JAA, including AWOSC, who (failing memory) drafted a change to JAR OPS. One aspect was to delegate approval to local authorities. However, these proposals appear to have been lost / dropped / found to be in error, or just not in accord with ICAO, such that they have not been used subsequently.
At the time, as I understood the argument, based on balancing the risks, it was reasonable to equate MDA/DH as an ALAR initiative
and thus I was surprised that this has not been progressed.

One possible concern was that there are differences between the PANS-OPS and TERPS obstacle allowances, which I think still apply in the current debate.
Lest anyone should think that the above is a case for deviating from current regulation / guidelines, don’t. In retirement I’m out of touch with current thoughts and memory fails me.

TM - #28; there is a difference in approach construction with obstacles on an approach (NPA), and a Cat 3 operation with an obstacle free zone.