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Alternates due to TAF

  • troyschultz
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troyschultz created the topic: Alternates due to TAF

Clearly an alternate is required if the TAF indicates conditions below the alternate minima for a particular aerodrome.
What happens if an aerodrome has an instrument approach procedure but no TAF? (example port pirie in sa).
Do we automatically assume that this aerodrome needs an alternate as it has no TAF or do we just use the information in the ARFOR as a valid destination forecast (which is open to much more interpretation than a TAF as it covers a much wider area)?

Anyone have an answer or a reference for this?
#1

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bobtait replied the topic: Re: Alternates due to TAF

AIP ENR 1.10 para 1.2.3 says that if the required forecasts [ARFOR + TAF] cannot be obtained, an alternate is required. So if you don't have a TAF you must have an alternate. However AIP ENR 1.1 para 57.3.2 says that if you are going to an aerodrome with no instrument approach, you don't need an alternate providing the ARFOR indicates that a visual approach will be available - no broken cloud below LSALT over the last route segment + 500 ft and 8 km visibiity. It seems logical to assume that if there is an instrument approach but no TAF, you could still do a visual approach if those conditions apply. The AIP remains silent on this. Interesting.....
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  • troyschultz
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troyschultz replied the topic: Re: Alternates due to TAF

Thanks for the reply, I thought that may have been the case, but that leads to another question...under what situations would the alternate minima listed in the approach charts apply?

If there is no TAF and we are using the lowest safe altitude +500 feet then wouldn't that make the specified alternate minima useless and pointless?
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bobtait replied the topic: Re: Alternates due to TAF

This is a good example of what happens when two different organizations get involved in one project. The surveyors who design the DAP calculate MDA as 300ft above the highest obstacle in the circling area [assuming CAT A or B]. They calculate the alternate ceiling as 500ft above the MDA and they do that with no consideration for the weather, its just a formula.

The Met people simply produce TAFs for their customers. What actually is happening here is that the alternate ceiling has been calculated according to the rules and the availability of the TAF doesn't change that. The alternate ceiling is simply sitting there waiting for the day when a TAF is available for that aerodrome. Until then, an IFR pilot will need an alternate unless he plans that leg VFR.

I'm quite sure that this situation would never be the subject of a theory exam and if it was I'd be very interested in seeing CASA's answer.
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  • troyschultz
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troyschultz replied the topic: Re: Alternates due to TAF

thanks for that, i didnt think it would be examined. i was just curious of the real world implications
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  • troyschultz
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troyschultz replied the topic: Re: Alternates due to TAF

Hello again Bob, I have come across another paragraph in the AIP which complicates things further. You said that in the event that the destination has no TAF, then an alternate would have to be planned based on the lowest safe altitude of the last leg being in VFR conditions.

However, ENR 1.1 57.1.3 states that "when an aerodrome forecast is not available or is "provisional" the pilot in command must make provision for a suitable alternate that has a firm forecast. This suggests that in the case of port pirie an alternate would have to be planned no matter how clear the area forecast indicated the weather to be. Do you agree?

And going one step further, it even suggests that if the flight was a good old simple VFR flight in a C172, an alternate MUST ALWAYS be planned unless the destination has a TAF...(the vast majority of VFR flights would therefore need to plan for an alternate)

What is your opinion on this?

Thanks again
#6

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  • Eddy

Eddy replied the topic: Re: Alternates due to TAF

Hey Troy
I recently raised the same question on this forum not realising you had done it previously. I agree with everything you say. Even about VFR flight needing an alternate. I'm sure that wasn't the intended interpretation but it certainly was written that way.
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