Reply from Insight:
That makes sense, though it almost certainly means that if the existing fuel totaliser instrument (which in effect powers the transducer) dies, you will lose the signal.
Funnily enough there is a 3 year old Insight G4 thread here and it has some really interesting comments 
I wonder if @commander is still here and can report?
I have emailed Insight, asking whether the partial functionality is possible to configure.
On a quick read of the IM it looks like the fuel flow sensor can be shared between two units. Well obviously it can be done, like anything else, but the Q is whether they cover the case of one of the units going dead and pulling down the supply to the sensor.
I don’t know which transducers the G models connect with as in my case I have a native Insight fuel flow system due to my TAS1000 ADC.
Interesting… many thanks Placido.
To get the 3.125" size one would need the G4
I would need to check that the fuel flow option and some other stuff can be disabled and not just show as 0.0 for example. Also I can’t find the memory capacity – one of the main EDM700 hassles. If it just fills the SD card, that’s fine.
Peter I put in the G2 from Insight Avionics. It fits into the standard hole and plugs into the existing probes. I had the GEM and just swapped it out with little work in the back. It is certified as primary instrument
That’s a fair set of points. Going feature by feature is definitely sensible.
On your G vs N reg point, i added oil pressure and temperature to my EDM730 recently. Not a big paperwork exercise at all. While it certainly used to be true that N reg saved a lot on paperwork, a lot has changed in EASAland in the last few years. Of course the FAA system is still simpler, but a lot of progress has been made.
What harm is there in duplicating instrumentation?
This will sound like I am trying to make an argument, which I am not, but I wish to point out that duplicating displays is usually not as simple as it may appear, in terms of what installation work needs to be done, and who can do it to the required high standard.
Years ago, with the unreliable Socata oil pressure gauge, I looked at installing a backup one. When I was G-reg this was going to be £ thousands just for the paperwork (I did spend some time on it – it may be easier today). Under N-reg this was a Minor mod (confirmed by various A&P/IAs and a US DER) which is just a logbook entry, and in it went. But still a lot of work was involved, because you need to install a T-piece, and it needs to be done to a very high standard, obviously, because if that breaks, you will be on a downwards trajectory pretty soon…
You need to install a T-piece for fuel flow, which in piston aircraft is taken from the fuel distributor because the fuel pressure at that point is a good proxy for the flow. On a TB20 this tube is a stainless braid protected tube because you don’t want a massive fuel leak into the cockpit. One can’t just put in a plastic splitter like one would use for feeding air to an aquarium, and have it hanging in the air among the wiring, though I have seen it done that way!
So let me list some other items which on a quick and dirty read of the CGR IM are going to be less than trivial to do (correctly):
etc
So IMHO this feature-packed box makes sense for upgrading a simple plane, but much less so for an already well equipped one unless you want to throw out a lot of stuff… presumably working stuff because nobody sensible will be flying a well equipped plane in which a lot of stuff doesn’t work. I can also see it being good for a 30 or 40 year old IFR tourer in which the 1970s avionics is constantly packing up and you want to chuck it out.
One also need to do some due diligence for e.g. the fuel function and data stream compatibility with the latest GPS box (to get the Landing FOB). Everybody tests with Garmin products but much less so with Avidyne products.
What harm is there in duplicating instrumentation? The CGR30P will record them as well, which is useful – but you don’t need to use them as primary for flight.
Saying that a device which cannot be touched except by a Garmin G1000 authorised dealer also has a single point of failure, so I should be happy with another one which is no better, is like arguing that if the UK CAA mandated both your legs to be amputated, but EASA published an AMC saying that one legged flight is permitted, EASA is full of really great people
I think my other main objection to the CGR30P is that I have nothing useful to put into the two large holes on the RHS which would be created. It is obviously a great box to install in a basic plane which had minimal instrumentation to start with.
Peter wrote:
There is however quite a bit of work “behind” it (due to the extra functionality) and it puts all your eggs in one basket in that if it packs up, you lose all the engine instruments.
That’s true, but most aircraft only have single engine instrumentation anyway. Even G1000 systems which have double redundancy in displays and processors have a single interface to the engine sensors.
