Woke up in the morning to a sms from an ATR 72 pilot asking about the ability of the ATR 72 to fly a GPS approach to minimums.

The question, and my search through my files got me a bit confused. There was no clarity on the viability of the on board HT 1000 to support GPS approach. So I had to head online.

It was a crazy search, but search I did, nevertheless! I found online an Airworthiness Approval document from the UK CAA, which specifies under limitations:

“The GNSS HT1000 must not be used for GPS approaches.”

This question has clearly caught me off-guard, and I’m now trying to understand what makes a non-WAAS GPS approach feasible. And another thing bothering me is whether this approval is only for the specific aicraft: : G-BXTN.

The Airworthiness Approval may be read here:

http://www.caa.co.uk/aandocs/26265/26265000000.pdf

If you can throw some light, it’d be great!

UPDATE: The fact that the unit is certified for RNAV 1 opertions, and approaches equire RNP 0.3 or 0.5 automatically disqualifies the aircraft from shooting GPS approaches with an ATR 72-200/500

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