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PA28 "no IFR" limitation on GNS430, and backup NAV equipment requirement

I was reviewing a PA28 POH/AFM recently and noticed the following for the first time (generic screenshot from CAA website):

Does anyone know the reasoning behind this limitation, and is there any way to remove it?

United Kingdom

I have found that a firm tug away from the rings of the binder reliably rips out the holes along the edge, After that, keep moving it horizontally until it is fully removed.

however, if that is bot satisfying because you don’t get to spend your cash on paperwork, you can get an AFMS approved that allows IFR (including GPS approaches and R-Nav), which may involve some additional tests for radio interference).

Joking aside – probably a good idea to do these tests etc if you want to use it for IFR in anger. For VFR nobody can tell what you use for primary navigation so just leave it alone.

Biggin Hill

Pirho wrote:

Does anyone know the reasoning behind this limitation, and is there any way to remove it?

The reason was a fear of GPS navigation by European authorities who didn’t really understand it. Many early GNS430 installations were restricted in various ways compared to the actual certified capabilities of the box itself. (E.g. not permitting RNP/RNAV 1 or, as in your example, not permitting RNP approaches.)

ESKC (Uppsala/Sundbro), Sweden

FM immunity? or not installed according to STC? or from old days?

We moved an Archer2 to G-reg, CAA added 1.4× factor to it’s landing distance in AFMS, no one in the group notice it or bother with it

Last Edited by Ibra at 24 Nov 07:08
Paris/Essex, France/UK, United Kingdom

This is dated 1999 and is typical CAA BS from that era. They did the same to my KLN94 in 2002. “Not approved for IFR”.

There are 11th and 13th harmonic tests which the installer is supposed to do – see e.g. here.

FM Immunity is a different thing entirely.

“Primary navigation” has always been BS. It’s always been legal (in private ops) to use whatever method.

The DGAC was doing similar stuff e.g. declaring that if a stormscope display rotated with the heading, a pilot may use it to avoid thunderstorms. That’s what Socata told me. They had to deliver TB20s with a certain connector unplugged. The dealer would then plug it in

Administrator
Shoreham EGKA, United Kingdom

Perhaps GNS was installed not iaw STC but something like minor change for VFR only ?

EDLB, Germany

That changed over the years. @wigglyamp posted on this many times. See here. Currently IIRC only SBAS (i.e. LPV capability) needs an STC/ Major Mod and a GNS430 obviously could never do that.

Maybe there was an era where an STC was needed for IFR specifically but I don’t remember anything like that. Especially in the UK where you can do IFR in Class G, non radio, etc

Loads of GNS430 boxes were installed off the books (I knew a guy who did about 100) but then the CAA would not know about it

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

That changed over the years. @wigglyamp posted on this many times. See here. Currently IIRC only SBAS (i.e. LPV capability) needs an STC/ Major Mod and a GNS430 obviously could never do that.

@Peter, there is distinction – wigglyamp mentions 430W, while you talk about the non-W.

EGTR

Sure; I was trying to make the point that it was only the W box which needs an STC; a non-W can just go straight in. But that is current, not in 1999 or some such. Back then it was probably either STC or a TC approval, for any panel mounted GPS (the KMD150 was one curious exception).

Administrator
Shoreham EGKA, United Kingdom

We do have an historic Minor Change with EASA-approved AFMS to allow BRNav and GPS non-precision approach for the non-WAS GNS430/530. It’s not a full AML but does include most popular Part 23 aircraft.

Last Edited by wigglyamp at 24 Nov 08:46
Avionics geek.
Somewhere remote in Devon, UK.
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