Car RAMROD
7th Oct 2012, 02:45
Discussion at the local amongst the blokes yesterday posed the question of the shaded alternate minima box (similar in jepps tables "with actual qnh").
AIP 1.5.5.3.1 QHN Sources has this to say:
Where instrument approach charts are identified by a shaded background to either the minima titles for IAL plates or the published minima for DME or GPS arrivals, landing, circling and alternate minima have been calculated by assuming the use of forecast terminal QNH. These minima may be reduced by 100ft whenever an actual QNH is set. Approved sources of actual QNH are ATC, ATIS, AWIS and CASA-approved meteorological observers. An actual aerodrome QNH obtained from an approved source is valid for a period of 15 minutes from the time of receipt.
Let's say that I'm flying from A to B. The alternate min at B is 1500ft in a shaded box. B has AWIS or ATIS/Twr (depends on what time you arrive). Cloud is forecast BKN014 (for simplicity that is all the weather all day).
The debate is whether you can somewhat "plan to have" actual QNH and thus apply a minima of 1400ft; or whether one would still have to plan for the alternate until you can have an actual QNH within 15 mins of ETA and then your minima magically redces by 100ft and thus now do not require an alternate (as forecast cloud will now be more than SCT AT the minima, not BELOW).
Reading it literally I interpret it as you must not take the 100ft off until you have Actual QNH, and thus it will only be within 15 mins of your arrival and still have to launch with an alternate.
Other opinions I have heard are that "there is AWIS/ATIS/Twr there so you will have actual QNH so the 100ft comes off now whilst im planning the flight and I don't need the alternate".
Discuss/debate !
AIP 1.5.5.3.1 QHN Sources has this to say:
Where instrument approach charts are identified by a shaded background to either the minima titles for IAL plates or the published minima for DME or GPS arrivals, landing, circling and alternate minima have been calculated by assuming the use of forecast terminal QNH. These minima may be reduced by 100ft whenever an actual QNH is set. Approved sources of actual QNH are ATC, ATIS, AWIS and CASA-approved meteorological observers. An actual aerodrome QNH obtained from an approved source is valid for a period of 15 minutes from the time of receipt.
Let's say that I'm flying from A to B. The alternate min at B is 1500ft in a shaded box. B has AWIS or ATIS/Twr (depends on what time you arrive). Cloud is forecast BKN014 (for simplicity that is all the weather all day).
The debate is whether you can somewhat "plan to have" actual QNH and thus apply a minima of 1400ft; or whether one would still have to plan for the alternate until you can have an actual QNH within 15 mins of ETA and then your minima magically redces by 100ft and thus now do not require an alternate (as forecast cloud will now be more than SCT AT the minima, not BELOW).
Reading it literally I interpret it as you must not take the 100ft off until you have Actual QNH, and thus it will only be within 15 mins of your arrival and still have to launch with an alternate.
Other opinions I have heard are that "there is AWIS/ATIS/Twr there so you will have actual QNH so the 100ft comes off now whilst im planning the flight and I don't need the alternate".
Discuss/debate !