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Old 26th Jul 2011, 21:10
  #35 (permalink)  
Lord Spandex Masher
 
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OBN, that document you quote from is over four years old. However, Subpart E has now incorporated some of the proposals.

You seem to have conveniently missed this bit.

Issues related to DA/H and MDA/H
The application of the CDFA technique requires all NPA operations, to be flown with a decision altitude/height (DA/H). When determining the applicable DA/H, the operator must take account of the missed approach point (MAPt) and the minimum descent altitude/height (MDA/H).

While it is quite clear that a missed approach must be initiated not later than at the MAPt, the question of MDA/H is a different matter. Quite a few operators use MDA/H as the DA/H with no height add-on; in fact this is the case with a majority of the largest European operators. This modus operandi has raised concern that the unavoidable height loss below the MDA/H during a go-around might introduce a safety risk, even if the height loss can be minimised by the use of appropriate operational procedures (call-outs, high degree of on-speed/on-path discipline, training). In order to evaluate the safety of the use of MDA/H as DA/H, the AWOSG has compared the obstacle protection for this type of approach with the obstacle protection for ‘traditionally’ flown non-precision approaches as well as with the protection for approaches with vertical guidance (APV) using the criteria contained within ICAO PANS OPS.

The AWOSG is convinced that using the MDA/H as a DA/H offers adequate obstacle protection.

Another comparison between the CDFA technique and the ‘traditionally’ flown non-precision approaches indicates that the latter involve several safety traps,
such as:
• Early descent with a prolonged flight close to obstacles;
• Multiple step-downs possibly inside the FAF;
• An approach which is, by definition, destabilised;
• Temptation to make a late and steep descent from MDA/H towards the threshold;
• Risk of descending early from the MDA/H;

While there are no records of accidents related to the use of the CDFA technique during approach operations, there are several accidents attributable to the risks listed above.
That is what has been implemented and that is how we operate, perfectly safely and legally. In fact they have proved that CDFA using MDA as a DA is safer than the traditional NPA even with the 50' buffer!

The DA(H) figure is derived from the OCA(H) for the associated procedure plus any buffer decided by the operator or the authority. MDA(H) is the lowest altitude (height) for the level portion of an approach flown using the traditional dive-and-drive technique, not the CDFA technique. Use of MDA(H) would undermine the philosophy of the CDFA
Use of the CDFA technique is considered as a significant safety improvement. (Ref to ALARP). It is also important to note that the NPA does not suggest anything that is not already in widespread use by European operators
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