Originally Posted by
fireflybob
Irrespective of company procedures or manufacturer "advice" I am staggered that any professional pilot would not be cross checking/monitoring any charted DME check heights on a non precision instrument approach.
Unfortunately not as simple as it sounds as the chart DME heights also need to be cold-temp corrected.
It appears that Air Canada got the approval of Transport Canada for a chart in the QRH (not shown in the report) that gave low temp corrections for FAF altitude and the MDA, rounded up to the nearest 100ft, and for the FPA itself. The numbers were apparently correctly extracted for these. But there is no mention of DME altitude corrections, which could be different for each approach and not easily amenable to 100 ft rounding since they would actually become less than 100ft as the aircraft descends.
Once the descent was started the aircraft was ALWAYS below the intended flight path. But using the indicated altitudes against the basic chart values would have produced the following indications:
6 DME indicated alt 2080 = 140 ft HIGH when actually 40ft LOW
5 DME indicated alt 1650 = 70 ft HIGH when actually 70ft LOW
4 DME indicated alt 1240 = 10ft LOW - near correct but actually 110ft LOW
3 DME indicated alt 840 = 80 LOW when actually 150 ft LOW.
Which brings to mind the question of what procedures AC used to deal with this situation for older aircraft, without a FPA facility?