Destination + Alternate

RNAV, GNSS, GPSS. Your place to discuss all aspects pertaining to Instrument Flying.

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FlyGiep
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Destination + Alternate

Unread post by FlyGiep »

So your destination has an RNAV only , closest alternate has RNAV to both runway ends. Legalities?
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Re: Destination + Alternate

Unread post by AOYB »

Depends on what you mean by RNAV. Assuming you mean a RNAV(GNSS) approach, any alternate needs to have a conventional navigation aid available for the landing.

So a GNSS only alternate is not permitted

AIC 25.4 subsection h.
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Re: Destination + Alternate

Unread post by Hop Harrigan »

Really?
Dammit, I was under the impression that an Instrument Approach was an Instrument Approach irrespective of the technology...
So does that mean the law presumes my GPS receiver is more reliable than an ATNS maintained VOR?
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Re: Destination + Alternate

Unread post by AOYB »

The law presumes that any outage of the GPS network will be widespread and most probably affect the alternate too. Hence the need for a conventional approach at the alternate.
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Re: Destination + Alternate

Unread post by tansg »

AOYB wrote:The law presumes that any outage of the GPS network will be widespread and most probably affect the alternate too. Hence the need for a conventional approach at the alternate.
I am impressed some has actually read the AICs I wrote :shock: and not only that seems to understand the the thought processes behind them :shock: :shock: :shock: Definitely as first for me in GA circles :lol: :lol: :lol:
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Re: Destination + Alternate

Unread post by FlyGiep »

So other than the AIC mentioned, theres no other reference to the requirements mentioned
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Re: Destination + Alternate

Unread post by AOYB »

The AIC covers the alternate question. If you require further reading, the UK has published a summary of the ICAO recommendations which goes into more detail.

SACARS wise, the laws cover the use of GPS as the primary (or sole) use of navigation wrt to certification of equipment.
But the AIC is fairly comprehensive.

As I said, you’re welcome to read the original ICAO recommendations (they issue recommendations but member states must implement them or file a difference)
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Re: Destination + Alternate

Unread post by FlyGiep »

Thankyou, wil read up on it
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Re: Destination + Alternate

Unread post by jonocollins_za »

Interesting.

The wording of the AIC 25.4 H;

“Where a take-off and/or en-route alternate is required, at least one non-GPS based approach procedure shall be available at the alternates(s).”

It does not give guidance for a destination alternate.

Thoughts? :?:
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Re: Destination + Alternate

Unread post by AOYB »

https://www.icao.int/WACAF/Documents/Me ... 20APCH.pdf

Check out slide 65 for more clarity.
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Re: Destination + Alternate

Unread post by transducer »

Further reading can be found in AIC 25.9 appendix 4 para 7,8 and 9. This about seals the deal with regard to any alternate, along with AIC 25.4, and should keep ICAO more than happy:
5464D114-C512-4184-950B-6913F483CDDC.jpeg
On another note, with regard to RT please see the below attachment from AIC 25.4 para i:
E9015A97-E27A-4F21-9E59-39B0F5AF9DE2.jpeg
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Re: Destination + Alternate

Unread post by jonocollins_za »

See underlined content providing further clarification:
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