Hi Bob et al.

Consider the "Sector A" GNSS arrival below


Now consider that a RAIM warning pop up passing 9nm at 2600' - what do you do?
Well, according to ENR 1.5 p 11.2.2(e), we make a missed approach



But how do we fly a missed approach?
Well, according to ENR 1.5 p 1.10.2, we fly to the MAPT ( the VOR in this case) then follow the procedure



With the above in mind, at what altitude do we fly to the MAPT. The AIP looks to be silent on this question. To my mind we have three options
1) Maintain current altitude - the RAIM warning altitude or
2) Climb to MSA or
3) Climb to LSALT

Now, given that the AIP is silent on the matter of altitude to the MAPT could one argue that we are free to choose from options 1), 2) or 3).

If yes, the etext cited below might not be so peculiar.

If the requirement is to commence a missed approach, the implication is that it is no longer safe to continue with the published procedure. Therefore it would make sense to immediately commence the climb to the height published in the missed approach procedure while maintaining the track to the MAPt by reference to the VOR.

However, there seems to be no logical reason not to maintain the last level that applied before the RAIM warning appeared. For example, if you had passed 5nm before the RAIM warning, why not remain at 1660ft to the VOR in the hope that you may become visual on the way.

It would be interesting to know if CASA has asked such a question and given both of those choices as options.

Thanks Bob

"However, there seems to be no logical reason not to maintain the last level that applied before the RAIM warning appeared. For example, if you had passed 5nm before the RAIM warning, why not remain at 1660ft to the VOR in the hope that you may become visual on the way."

In agree, and more importantly ENR 1.5 1.10.2 supports your logic. This paragraph is saying that there is no requirement to climb on a missed approach until you reach the MAPT.



This is quite different to loosing visual reference in the circling area below MDA - then 1.10.3 kicks in

Several thoughts ..

(a) it is not a good idea to have too many plans on the go, simultaneously. On the the approach for a straight in landing .. wx goes sour ... missed approach and then rebrief for an alternative plan. Quite a different matter if the original plan was to break for the circling approach to another runway. Beware, though, of being suckered into doing the straight in landing on the fly as an alternative to the circling break off.

(b) it has long been SOP that, once the approach has been abandoned and the miss commenced, maintain the procedure track (as best you can .. the loss of azimuthal confidence is, in all likelihood, the reason for giving it away) ... and immediately commence climb to the missed approach level/MSA as more appropriate to the particular circumstances. Be particularly wary of the sucker bait trap of turning onto the missed approach heading prior to the MAP ... CFIT histories abound for this sort of error.

(c) if one reviews the details of procedure design, one will see that there are (obstacle) protected areas around the prescribed tracks. Get a bit too far off track and you are a CFIT waiting to happen in many situations. Remaining low, following a problem, when tracking integrity is suspect .. is a fine way to become a CFIT statistic. Far better to put air between the aircraft and the rocky bits.

(d) why not remain at 1660ft to the VOR in the hope that you may become visual on the way.

It has long been SOP that "dive and drive" vertical planning is very much inferior to conducting a quasi-steady descent. By staying high, in the hope of getting visual, the pilot sets him/herself up for an unstabilised final approach with the raft of problems that can bring .. especially on higher inertia aircraft. Indeed, do that in a disciplined airline-style environment and one can anticipate an uncomfortable meeting with the Chief Pilot .. no tea and biscuits ... and remain at attention for the duration.

As I suggested previously, the AIPs should be viewed as a good starting point. However, the sensible pilot will always for looking for the problem which thwarts the AIP words. Not suggesting that one should operate non-conservatively with respect to the AIP at all ... but blind and unthinking adherence to the words can, on occasion, get one into more strife than Speed Gordon.