Originally Posted by BOAC
1) It appears that although you would be 'watching' the threshold NDB on the HSI you are not really flying an 'NDB' approach. What is the SOP should this ADF needle drift off, say 10 degrees as you approach MDA? Do you follow your FMC, correct to the needle or g/a?
The approach is an NDB approach - nothing else - just using a fancy autopilot. On our fleet, we can only tune one NDB, due to terminal cheapness (most 320s have both ADF receivers fitted). If you go outside limits on the approach aid (5°) then you go around - if you another aid tells you something is wrong then that'll be one of those "airmanship" go arounds I guess.
Originally Posted by BOAC
2) On the basis that you are not actually flying an NDB but something generally more accurate, would you use the NDB MDA or a lower and is this sort of an approach called an 'NDB ' approach?
As above really - this is an NDB approach, with NDB minimums. We add 50' to the MDA to make a DA.
If you are using the GPS as the
primary source of navigation (a GNSS approach), then there are hugely different procedures, checks, qualifications needed and so on. And there has to be a published procedure. We do a few of these at various places - Sharm for example.
Originally Posted by BOAC
3) There seems to be a suggestion that this approach is neither approved or used by Afriqiyah. This would appear to be the case as I cannot see any other reason for the crew to have been flying what appears to be a VOR approach which is offset. What would your airline expect on 09 at TIP?
The only thing I have read is that this is the approved approach for Afriqiyah (see below).
At our airline we have approval and training to do managed/managed approaches (unlike Afriqiyah). I would not use the VOR as it is notammed as crap. So I would do a managed/managed (FM guided lateral and vertical) NDB using company minimums of 670'. If I didn't have good visual of a runway to make a stable landing on, then I'd initiate a go around as soon as we got to minimums.
If the approach was not in the box, then it would be selected/selected.
Originally Posted by Fireflybob
One for 100% on the Airbus - if the approach is in the FMGS database can you not fly the vertical profile in managed mode rather than FPA?
Only if you have the appropriate approvals in place. For the first year or so at our company we didn't have this approval, so we had to fly managed NAV / selected vertical.
Giggy informed us in
this post that
They fly managed laterally and selected vertically Npa's.
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As I mentioned before - for a working aircraft to end up at the ground you need to start at the wrong height (altimetry) or select the wrong FPA (and continue below minimums hoping to find the runway).
There are 2 things concerning me:
1) The aircraft is so good you "expect" to end up at minimums bang on the centreline with 2 white and 2 reds. If you can sort of see the ground then "it should be there somewhere"...
2) There is no published approach angle on the plate. You have to work it out (assuming it's not in the box) and arctans and fatigue do not mix well. Below is a pictorial guess/calculation at where you would hit the ground with various FPAs selected.
Mix 1) and 2) and the result could be dangerous. Remember also that you fly the approach "to get in". With no vertical guidance (height/distance checks) you would set the FPA to be slightly steeper than perfect, because it's best to arrive at MDA
slightly too low for the visual segment than slightly too high.
