achimha wrote:
In my view, this makes a GTX 345 illegal in a Malibu.
The Malibu (piston version, the one I have) POH doesn’t give a max cruise speed but even at full authorised power you won’t be anywhere near 250KTAS (sadly). I’m getting 204kts at 29” 2500rpm at FL250, going to 35” might give me 15 to 20kts more.
Now of course if I were to put a PT6 in the nose that may be different, but given that the Jetprop POH simply describes performance as “equal to or better than the piston version”, I’m not sure how that would play out.
Peter wrote:
So I wonder whether the combining does really work, or whether people just accept it and not question it, and it looks “ok” in most situations?
I’ll be the first to admit that my testing is yet very limited. But it’s possibly a moot point, if the merging works well enough but combines targets which are effectively as one for avoidance purposes. Unless we can come up with a theoretical case where a traffic is ignored but dangerous and that we could test somehow – my imagination isn’t up to the task :-)
achimha wrote:
In my view, this makes a GTX 345 illegal in a Malibu.
That might be too strong a characterization. It might not meet a particular ADS-B Out requirement, but that does not make it illegal. I don’t think the piston version falls under the upcoming mandate. The M500 and M600 would, but the M600 comes from the factory with a GTX330 and there is a diversity option for it.
Peter wrote:
So I wonder whether the combining does really work, or whether people just accept it and not question it, and it looks “ok” in most situations?
It does work. FYI, the ADS-B Out data is required to include the squawk code and the transponder must use the identical altitude source.
These are the required elements in the ADS-B Out message:
(d) Minimum Broadcast Message Element Set for ADS-B Out. Each aircraft must broadcast the following information, as defined in TSO-C166b or TSO-C154c. The pilot must enter information for message elements listed in paragraphs (d)(7) through (d)(10) of this section during the appropriate phase of flight.
(1) The length and width of the aircraft;
(2) An indication of the aircraft’s latitude and longitude;
(3) An indication of the aircraft’s barometric pressure altitude;
(4) An indication of the aircraft’s velocity;
(5) An indication if TCAS II or ACAS is installed and operating in a mode that can generate resolution advisory alerts;
(6) If an operable TCAS II or ACAS is installed, an indication if a resolution advisory is in effect;
(7) An indication of the Mode 3/A transponder code specified by ATC;
(8) An indication of the aircraft’s call sign that is submitted on the flight plan, or the aircraft’s registration number, except when the pilot has not filed a flight plan, has not requested ATC services, and is using a TSO-C154c self-assigned temporary 24-bit address;
(9) An indication if the flightcrew has identified an emergency, radio communication failure, or unlawful interference;
(10) An indication of the aircraft’s “IDENT” to ATC;
(11) An indication of the aircraft assigned ICAO 24-bit address, except when the pilot has not filed a flight plan, has not requested ATC services, and is using a TSO-C154c self-assigned temporary 24-bit address;
(12) An indication of the aircraft’s emitter category;
(13) An indication of whether an ADS-B In capability is installed;
(14) An indication of the aircraft’s geometric altitude;
(15) An indication of the Navigation Accuracy Category for Position (NACP);
(16) An indication of the Navigation Accuracy Category for Velocity (NACV);
(17) An indication of the Navigation Integrity Category (NIC);
(18) An indication of the System Design Assurance (SDA); and
(19) An indication of the Source Integrity Level (SIL).
Many thanks NCYankee. So, ADS-B OUT includes the transponder’s 24-bit ID, which makes merging trivial because that is a unique code.
However, doesn’t that mean the transponder on any ADS-B OUT aircraft must be a Mode S (not Mode C) unit?
You could have a portable ADS-B out solution with a mode C xpdr. However if done properly (I only have experience with Powerflarm) when setting up the portable unit you must enter your aircraft’s HEX.
Peter wrote:
However, doesn’t that mean the transponder on any ADS-B OUT aircraft must be a Mode S (not Mode C) unit?
In Europe, if the transponder is Mode S, the transponder and the ADS-B Out are one and the same device. But in the US, Mode S is not mandated, so most GA aircraft have Mode A/C transponder. Those aircraft can either replace their transponder to one that supports 1090ES or they can add a UAT (978 MHz) ADS-B Out system and keep their existing mode A/C transponder. Garmin recently announced a low cost solution for these Mode A/C equipped aircraft, the GDL82. It is a UAT ADS-B Out only device that has a built in position source and is simple to install. You unplug the existing transponder antenna and connect it to the output of the GDL82. You run a jumper cable to between the transponder antenna port and the GDL82. You mount the GPS antenna on the cabin top and run the cable to the GDL82 and connect power.
UaAvionix is also about to be adding a simple install system with this device https://www.uavionix.com/ which is now available for installation for the experimental aircraft with promise of a version for the certified systems.
Both of these solutions are UAT and ADS-B Out only.
