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GTN650 and GTN750 into a TB20

Neil wrote:

That’s the philosophy that leads you to PCs running Linux which won’t run any programmes that work properly :)

But those 2 apps that do run are far better than their windows or mac equivalents…..

EGTK Oxford

For some reason we are getting flooded with off topic posts – just as I am on the trip to Menorca.

The Track Up versus North Up stuff is here

How does your current set up with the king GPS work.

The KLN94 feeds the KMD550. It works perfectly. The only thing missing is LPV capability, and for strict paperwork reasons the KLN94 doesn’t have the PRNAV (now called PBN or some such) LoA so cannot legally fly “RNAV” SIDs/STARs.

Other stuff which would be “nice” would be a much faster flight plan entry, and removing the KLN94’s limit of 20 waypoints per flight plan.

Administrator
Shoreham EGKA, United Kingdom

I wonder if anyone has an answer to my post #27? Specifically is there a config on any GPS for selecting one of multiple EHSI course pointer inputs? It would be rather weird and a good way to get into trouble.

There must be some installations out there which have 2×GPS and 2×HSI/EHSI. Maybe not many in piston aircraft but a RHS panel is common in the bigger stuff.

One obvious way would be an “OBS source selector” switch next to each GPS.

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

I wonder if anyone has an answer to my post #27? Specifically is there a config on any GPS for selecting one of multiple EHSI course pointer inputs? It would be rather weird and a good way to get into trouble.

There must be some installations out there which have 2×GPS and 2×HSI/EHSI. Maybe not many in piston aircraft but a RHS panel is common in the bigger stuff.

One obvious way would be an “OBS source selector” switch next to each GPS.

I think your terminology is a bit mixed up. On glass panels I have used you can select which source drives the CDI. It can be GPS1, NAV1, NAV2, FMS1, FMS2 etc. If you multiple CDIs you can select which one drives an autopilot or FD.

Equally you can choose which AHRS and ADC to use.

And it gets clearly annunciated on the PFD.

Last Edited by JasonC at 11 Oct 07:58
EGTK Oxford

On larger aircraft – small jets and upwards, the course controls (OBS function) are separate from the EFIS – typically a control unit with a single HDG knob and two course knobs, one associated with each NAV/FMS system rather than knobs provided for each HSI.

In your situation, I would suggest you use just the OBS output from the left HSI to both GTNs as there is no provision to connect two separate OBS inputs to a GTN where there’s only one ARINC429 input. The right HSI course pointer will be a slave display of the left HSI when operating in GPS OBS mode but otherwise has full functionality. Note that the OBS wiring isn’t used in VOR/ILS as the VHF NAV data is resolved within the SN3500.

Avionics geek.
Fairoaks. EGTF

Peter wrote:

so cannot legally fly “RNAV” SIDs/STARs

and neither RNP LNAV minima approaches…

LFPE

Do it properly Peter. Get rid of the analogue wiring and external switching and it becomes much simpler and removes many potential failure modes. You only require 3 twisted pairs between each GTN and the Sandel. These are for NAV and GPS to the Sandel and OBS back to the GTN. Annunciation and all deviations are on the digital busses.

The diagram below must be what you are referring to…?

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

The diagram below must be what you are referring to…?

Yes – nice and simple with no relay boxes required.

Avionics geek.
Fairoaks. EGTF

OK, that will be the plan.

Since Socata kindly ran a load of cables directly into the centre stack compartment, extracting it is going to be very time-consuming. I think their “grand plan” was that the whole left hand panel would be disconnected and that would free up those cable (it is stuff like the KEA130A gray code wires) but that is another waste of time.

So the plan will be to do it in situ. Upon extracting the KMD550, KLN94, 2xKX radio, one will have a big enough hole for a gorilla to get its arms in. The main issue is how to remove the existing avionics trays. If the nuts for the screws cannot be accessed, they can be drilled out with an angle drill while holding a hoover in there. The new trays can be screwed into rivnuts.

No wonder installers dislike TB aircraft, but it is for the wrong reasons (previous bodges).

Administrator
Shoreham EGKA, United Kingdom
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