Pocket TCAS -- an idea
 

I've been wondering about TCAS and GA. Unless I misunderstand, TCAS is a fairly complex piece of kit and, presumably, quite expensive to fit relative to the other costs of the smaller Cessnas and the like. Which is why it isn't there, but there are enough incidents and accidents to make one feel that perhaps it should.

I think it would be possible to build a TCAS-like system in a box roughly the size of a handheld GPS, and a few back-of-the-envelope design sketches make me feel it shouldn't cost more than £400-£500 in volume. There are lots of interesting engineering (and other) challenges, but I think the basic building blocks are available and the overall complexity of the system would be comparable to existing systems like GPS and GSM. I'm not sure of my knowledge enough to properly consider the issue of interoperability with existing TCAS, though.

Is anyone doing such a thing? Would it be worth developing? Would it help PPLs avoid accidents, or would it be one more distraction to confound the less confident aviator?

R

PS -- Aargh! As is the way of such things, the moment I posted this I found out the existence of ADS-B, which looks much like what I had in mind. Oh, well... is it?




[This message has been edited by Self Loading Freight (edited 26 August 2000).]

A cheaper TCAS would certainly be a welcome safety net for the General Aviation (especially lower end) aircraft - but no such thing exists, as you know. TCAS, for the display, derives the azimuth of the other aircraft from the multiple receive channels and segmented antennas - making it somewhat expensive - and the azimuth is not very accurate, but sufficient for "looking in the general direction to visually identify" the intruding aircraft. TCAS relies on the rate of closure than the direction of closure.

ADS-B can possibly at some point do what you want it to do - but it will take a few years to work through the issues. Such work IS being done by RTCA Special Committee 186, EUROCAE Working Group 51 and to some extent by ICAO ADS Panel. The FAA and EUROCONTROL are also involved.

ADS-B is in the processes of being operationally evaluated by the Cargo Airline Association in the USA (there is no present TCAS mandate for the Cargo aircraft in the USA) with emphasis on enhanced visual operations and conflict detection at longer ranges than present TCAS. A few European carriers have also done an initial ADS-B implementation for collecting data on its suitability. It is not nearing (i.e., a few years from) interoperating with TCAS yet. One of the issues is the selection of a datalink for ADS-B. There is the 1090MHz link which transponder and TCAS operate in; there is the VDL Mode 4 link (VHF band) that some European countries are interested in; then there is the UAT link in the 960+ MHz band.

There are several places you can look on the web to get more information on the status of the activities.

Do you have any web references for the ADS-B, I see that the Ryan TCAD equipment is upgradable to include it but I dont know what it is ?

Ryan TCAD is designed to be a GA version of TCAD, the ones I have seen are not full TCAS boxes as they lacked the datalink capability for aircraft to communicate and come up with advisories (hence TCADetection not TCAS).

Their web site is http://www.ryan-tcad.com/products/tcad/Main.html the high end boxes can interface with Eventide ARGUS displays, Avidine Flightmax Flight Situation Display, and the Garmin 400/420/430/530 GPS systems to display the aircraft threats.

They claim their systems have been installed in aircraft ranging from kitfoxes, cessnas, commuter turboprops (1900, Merlin, Metro III, Saab 340), corpoate jets (Citation, Lear, Hawker, IAI, Saberliner) to B737's, they have been around for years.

[This message has been edited by Zeke (edited 27 August 2000).]

There are several web references on related work. Note the availability of the hardware and software for ADS-B is only part of the solution (somewhat similar to having a modem and plumbing of the internet). The rest of the solution is the development of applications and operational concepts (roughly similar to having a web browser and web servers & content and e-mail and what not). Initial evaluations need also to be followed by extensive simulation, analysis and improvement, then implementation of the improvements, creation of standards, certification and operational approval. (Is that enough background before the web addresses!)
http://www.caasd.org/cdti has draft operational concepts and other useful information as well as links to other sites (incl. FAA Tech Center).
http://www.ads-b.com is a Cargo Airline Association site, describing what they (and FAA Safe Flight 21) are doing and with many useful links.

Also look at http://www.faa.gov/safeflight21/
for the Ohio Valley and Alaska Capstone efforts as well as some others (Follow Links from there).
http://blinder.lfv.se/ans/card/nean.htm and http://www.aatl.net/projects_frame.htm
are good sites for keeping track of the European trial activities.

NASA, NLR (The Netherlands) and Eurocontrol are involved in the Operational concept development and Human Factors evaluations for some of the upcoming appolications.


As for manufacturers, a UPS subsidiary (UPS AT) has fielded equipment that is being operationally evaulated (some are their own design, some bought from others). The major manufacturers are making provisions in their latest equipment (including Transponder and TCAS) for ADS-B transmit and receive functions and are awaiting the publication of standards for creating a certification basis. The RTCA standards for the 1090MHz ADS-B (transmit/receive) are close to publication. The VDL-Mode 4 draft standard proposal is in review and is expected to be published soon.

[This message has been edited by Narada (edited 27 August 2000).]

Dr Bill Brooks, who is variously Chief Designer on the Farnborough F1, and also at Pegasus Aviation was mooting something like this a year or two ago. It might be worth dropping him a note.

G

There is a finite limit to the number of TCAS 1 installations that can be operative in one area, due to the possibility of overloading of the system. This occurs because each aircraft interrogates others within its range. Each installation therefore has to be licenced and the number of licences is controlled.

I am not sure about the other systems.

Hi!
Here in the land of the free and home of the brave, 'handheld' TCAS is available for 990$ (I know 'cos my buddy just got one!). Know nothing about it, he seems to like it!

Nimbus-
Where's "here" and what does your buddy have? This is a tech forum and more information is welcome, rather than saying someone's got something like a TCAS. What does it do? Who manufactured it? Is it certified?

To add to Narada's excellent list of links, there's a big EuroControl project on ADS-B with lots of supporting documentation:
http://www.eurocontrol.be/projects/e...ds/default.htm

Part of the problem of TCAS for GA is the directional antenna requirement. The BF Goodrich Skywatch system is a TCAS that's aimed at the bottom end -- AFAIK it doesn't meet the relevant standards for air carrier use. And even that is probably too big to put on a sophisticated single, let alone a microlight or glider.

I'm convinced the answer lies in ADS-B and similar.

Thanks to everyone for all the info -- it's gratifying to realise that I'm not completely out to lunch, and rather mortifying to find that not only has someone had the temerity to think of it first but the gall to put in place a large-scale development over many years. Oh well, the SLF retirement fund will have to come from somewhere else...

Getting back to the technical stuff, the most interesting aspect (for me) is the nature of the datalink, which is where TCAS is quite weak. There's an awful lot of stuff to wade through, but it doesn't *quite* look as if the system will do the pocket TCAS I was first thinking of -- although the basic time-slice protocol sync'd to GPS derived UTC would work there. But we're eight years out from deployment: plenty of time.

There are some new developments in radio technology which may simplify things considerably, but looking at the timescales for ADS-B I wouldn't think that they'll be mature enough for consideration for this cut of the standard.

Back to wading through the docs. Perhaps I should become an aviation correspondent and get paid for this stuff :)

R

Narada,
"here" is the US, and sorry about the lack of tech info!
Like I said, I know nothing about it, just that the guy bought one and likes it.
I'll find out all I can about it and post the info!
Give me a few days!

Narada,
Tech info suitable for this forum can be found at http://www.monroyaero.com/