Required functions and present coverage
| Function | Why it matters | Present coverage | Next action |
|---|---|---|---|
| Magnetic heading | Part-NCO instrument function | Compass plus probable heading indicator | Confirm compass condition and stabilised-heading serviceability. |
| Barometric altitude, IAS and VSI | Basic instrument flight | Conventional instruments visible | Verify pitot/static condition, tests and pitot heat. |
| Turn/slip, attitude and stabilised heading | Instrument control and failure safeguards | Conventional six-pack visible | Confirm power source, warnings and serviceability. |
| OAT, accurate time and power warnings | Required/supporting indications | Not fully established | Identify and test. |
| Suitable communication | ATS and airspace requirements | Historical TY91 fit; TY96 reported bought separately | Document final 8.33 equipment, installation and release. |
| Suitable surveillance | Airspace requirement | TT31 Mode S | Confirm configuration and altitude source. |
| Conventional VOR/DME/ILS | Route/approach capability and training | Promising historical fit; unidentified Bendix unit may be unserviceable | Identify the unit and prove retained glideslope, indicator and DME serviceability. |
| Approved GNSS/PBN | Modern routes and RNP procedures | Not identified | Install approved navigator and guidance display if justified. |
| Navigation failure outcome | Required planning/resilience principle | Potentially strong if conventional equipment remains serviceable | Document practical contingency for intended routes and approaches. |
Acquired equipment and later direction
Purchase evidence records an FS-450 fuel-flow monitor, Garmin GMA 345 audio panel, Trig TN72 GPS receiver, Trig TA70 WAAS antenna and Comant CI102 marker antenna as bought/ordered. Colin separately reports a bought TY96, an existing TT31, a hoped-for PAI-700 compass, and a back-ordered USB charger.
These status labels matter: the evidence does not establish that the items are installed, approved, configured, serviceable or released. The recorded purchase also excludes all fitting work and installation parts.
Navigation and surveillance
Colin reports a Garmin GTN 750 and Narco 890 DME as later intentions. The exact GTN 750 variant, purchase status, approved guidance display and interfaces remain to be confirmed. A suitable GTN 750 installation can address the approved GNSS/PBN gap and provide model-dependent COM/VOR/ILS functions, but it does not itself provide DME. The Narco 890 therefore matters if the KNS 80 DME is removed or unavailable.
The report also says possibly one or two Garmin units described as “G1275”. That identity is unresolved; it may be a reference to GI 275, but the model, quantity and intended display/attitude/course-guidance roles must be stated rather than guessed.
The TN72/TA70 may provide position data for a compatible approved TT31 ADS-B installation. They are not an IFR navigator. Mode S equipment and compatible components do not by themselves establish an approved ADS-B Out installation.
Audio, fuel flow and installation scope
The GMA 345 can modernise audio selection, intercom and Bluetooth functions, but it requires complete integration with the selected COMs, headset jacks and retained audio sources, including isolation and fail-safe operation. The CI102 is only an antenna; marker reception depends on the complete installed system and should not drive the navigation architecture.
The FS-450 adds fuel-flow information. It does not indicate the quantity remaining in each tank and therefore does not remedy or close the known fuel-gauge defect.
The complete design and installed quotation must cover exact models and part numbers, retained NAV/DME/COM functions, approved guidance and annunciation, antennae, harnesses, breakers, electrical load, cooling, panel work, configuration, tests, weight-and-balance amendment, approved installation data, AFM supplement, PBN documentation, databases and release to service.
Priority order
| Priority | Work | Reason |
|---|---|---|
| 1 | Resolve fuel-indication and any other airworthiness defects | Dispatch baseline precedes optional capability. |
| 2 | Complete and document COM work | Establish reliable 8.33 kHz communication. |
| 3 | Inspect/test instruments, NAV, DME, ADF, indicators and pitot heat | Avoid replacing useful equipment based on assumptions. |
| 4 | Establish AFM/supplement and modification-record basis | Confirms what operations and installations are approved. |
| 5 | Complete an approved GTN 750-centred design with suitable course guidance and retained DME | Fills the main modern navigation gap without silently discarding existing functions. |
| 6 | Improve real-IMC failure resilience if needed | Consider battery-backed attitude and electrical endurance. |
| 7 | Modernise engine indication if independently justified | Useful for engine management, but not an IFR-navigation enabler. |
Shopping-list decisions
| Item | Assessment |
|---|---|
| FS-450 | Purchased/ordered for fuel flow; useful engine-management information but not a fuel-quantity defect remedy. |
| GMA 345 | Purchased/ordered; design and quote the complete audio/intercom installation. |
| TN72 + TA70 | Purchased/ordered; assess approved TT31 ADS-B integration, not IFR navigation. |
| TY96 | Bought separately by report; confirm the unit and include it in the final COM/audio architecture. |
| GTN 750 | Later direction by report; confirm exact variant, acquisition status, approved guidance and complete integration. |
| Narco 890 DME | Later direction by report; establish whether this replaces the KNS 80 DME path. |
| “G1275” unit(s) | Unresolved description; identify exact model, quantity and intended functions before design decisions. |
| PAI-700 and holder | Hoped for by report; optional while the existing compass is serviceable, with mount/applicability to confirm. |
| USB charger | Back-ordered by report; exact approved item and electrical installation remain open. |
Practical end state
The preferred result is a coherent set of independent functions: serviceable conventional attitude and air-data instruments, retained VOR/localiser/DME capability where supportable, approved GTN 750 guidance on a suitable display, reliable 8.33 COM, properly documented surveillance, sensible electrical resilience and a clearly separate SkyDemon/Aero Tracker awareness layer. The acquired hardware is not an installation design; exact variants, “G1275” identity, retained equipment and complete fitting scope remain open.