Dear All,

May be confused with the following scenario:

1. ETA at YXYZ at 0345 with a TS listed as FM Prob. 30 0204 TS. No other operational requirements.

To avoid nominating an alternate, should I carry 45 minutes holding fuel or just 30?

I was under the impression that the holding must be until the end of the lifting of the From + 30, making 45 minutes.

2. Another query: what does it mean if a VOR is described as the "reference waypoint" (see Cairns ILS RWY 15). (BTW: why do some approaches have x, y or z appended?)

Thank you for any help.

1 Check AIP ENR 58.2.7(b). The FM is for a change from bad [thunderstorms] to good [thunderstorms cleared]. The thunderstorms are expected to clear at 0400 so you must either carry an alternate or carry holding until 0430 i.e. 45 minutes. In the example you have quoted, there is no option of carrying 30 min holding anyway. By the way, the times given in that TAF should include the date so 0204 should be 0702/0704 [assuming the date is the seventh.

If you are doing a GPS arrival you must reference the GPS to the same point from which the DME works [the VOR location]. That means the GPS and DME will give exactly the same distance readings. When you select a destination on the GPS you are given a choice of measuring distance from the aerodrome or from the VOR. You should select the VOR.

The X, Y and Z suffixes indicate differences between the approaches [always slight and sometimes hard to find]. For example one approach may assume a missed approach gradient different from the other or a DME set to the LOC instead of the usual VOR. In any case, for the sake of an examination, the examiner would have to indicate in the question which approach he is referring to.

Thank you very much, Bob. Your help is greatly appreciated!