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Is IFR with a single GPS legal?

Sure; you can fly an NP GPS IAP with a tablet app.

But you can’t fly LPV with any tablet app.

Nor can you fly any autopilot coupled IAP with a tablet app. Not even in a homebuilt, because no noncertified GPS can provide AP guidance on any GPS IAP.

But I think the Q here is whether legally you need two units. I think everybody agrees two is “nice” but costs €€€€

Administrator
Shoreham EGKA, United Kingdom

I have had certified GPS units fail. Broken antenna. Issues with the antenna cable. LCD backlight failing. etc.
Modern glass panels depend so much on GPS that I consider a 2nd WAAS GPS unit far more important than a 2nd NAV receiver.

I’m fortunate to fly with a shed load of certified GPS on board (normally 5). I once asked our engineers why they didn’t just splice signals from a single unit. Whilst they couldn’t put their finger a specific reason, they just liked the keep-it-simple theory, especially when diagnosing faults. Hence the multitude of Garmin labelled bumps on the outside of the airframe. :(

Fly safely
Various UK. Operate throughout Europe and Middle East, United Kingdom

You can’t share a GPS antenna among multiple receivers, AFAIK.

Maybe the pre-amp inside it has enough drive to drive several loads, but

  • it would not be STC compliant
  • only one GPS could be used to power it so you don’t get more reliability (unless wire-ORd with diodes – again non STC compliant and there would be a voltage drop)
  • a single point of failure, and quite a likely one too (see the GPS antenna issues with defective preamps)

But if you are talking about using an NMEA signal from one GPS to feed multiple loads, that should work, interface permitting.

Administrator
Shoreham EGKA, United Kingdom

There are permitted simultaneous uses of a single GPS antenna – one to a navigator and one to an EGPWS. Honeywell make an approved splitter for this function.

Avionics geek.
Fairoaks. EGTF

How much is it, and where does it get power from?

It would have been rather useful to me, but nobody in the avionics business ever mentioned it.

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

How much is it, and where does it get power from?

We also fabricate these, for our BlueBox flight data recorder for aerobatic aircraft. These units often use either two receivers and one antenna, with on one port a DC blocker, or how we use it a single receiver with dual antenna’s.

JP-Avionics
EHMZ

lenthamen wrote:

I have had certified GPS units fail. Broken antenna. Issues with the antenna cable. LCD backlight failing. etc.
Modern glass panels depend so much on GPS that I consider a 2nd WAAS GPS unit far more important than a 2nd NAV receiver.

You basically give an answer on your own requirements / question. Although not required, it might be a good idea to upgrade from GNC to GTN.

Peter wrote:

There isn’t such a requirement for IFR in CAS, where a BRNAV GPS installation is sufficient. No duplication is required. Not even two radios so not even two 8.33 radios.

It is part of some STC requirements. In some STC’s for IFR use a second COM / NAV is required. So if your using suchs an STC you don’t have much of a choice.

JP-Avionics
EHMZ

OK; I recall this being posted here a while ago. Was it an STC for a second GNS box by any chance which had the dual radio requirement?

The FAA must be falling over backwards laughing at all this.

Administrator
Shoreham EGKA, United Kingdom

@Peter , I’m not sure how much the FAA is laughing about this.

The text below is taken from the GNS430W installation manual.

ESTL
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