Mode S Transponders

[LowNSlow]

Under current plans all aircraft will have to fitted with a Mode S transponder by 2008.

Apart from the practicality of fitting a transponder to certain vintage aeroplanes, I have a burning question:

As a bod who spends 99% of his time outside controlled airspace under VFR Rules and below 3,000', what benefit will be realised from an ATC point of view, by me, and thousands like me, spending about GBP3-4,000 fitting the little box?

<img src="confused.gif" border="0">

[Iron City]

Maybe very little other than the bigger and faster people being able to see you on TCAS and not running you over.

Maybe there could be a deal that the light GA people don't have to go Mode S if they do put current technology BI transponders in that don't have all the funky little logic glitches that the current system has to spend lots of time and software code to work around and that dumb's down the information provided to controllers?

[ 13 February 2002: Message edited by: Iron City ]</p>

[Spiggit]

Does beg the question why do sky divers and other such peeps have to carry them on their "flights" though...

<img src="confused.gif" border="0">

[LowNSlow]

If there is somebody bigger and faster than me in the bits of sky I usually inhabit, they would only be there cos they are in trouble :) . .On this basis would they be able to avoid me anyway <img src="confused.gif" border="0">

I think it's an extremely worthwhile tool for airways traffic but a completely unneccessary expense for GA non-airways traffic.

It was explained in a previous thread that the Mode S transponder needs heading and airspeed input in a digital format. My aircraft doesn't even have a generator let alone any fancy electronics (apart from a battery and a teeny weeny radio) <img src="eek.gif" border="0">

[Iron City]

Low n Slow. The Mode S transponder does not need inputs from a FMS or air data computer to perform it's basic function of selectively addressable beacon transponder.

The lower end GA crowd has successfully put off equiping with state of the art transponders in this country for 15 or 20 years. For this reason there is a lot of code patches in the ground systems that is used to filter the c&*p that some transponders provide. The result is a plumbers nightmare of spagetti code to maintain and operate in real time all the time.

I sympathize with the obvious stupidity of requiring high tech avionics on light aircraft that are not flying on, across or near airways and will never enter a major airport's traffic area and have no need or desire to be seen by ATC or to be provided radar services. Should be some kind of release form for you to sign so that if you are up s creek without a paddle some dark and stormy night and need a vector or need rescued, well, they'll do their best but.....

Transponders themselves (even mode S ones) are not in and of themselves very expensive. The problem is the certification approvals and then the installation that can cost a huge huge amount, 2 and 3 times the cost of the transponder. Then you have maintenance. Part of the problem seems to be the way they a re bought by individual owners (retail if you will). Possible huge price brak if batches of a thousand or so were sold. Maybe the GA owners organizations could turn to on that issue and get some CAA cooperation, but then again that is too much like hard work and not near as much fun as moaning about the rotten nasty regulations.

[2 six 4]

How many Cherokees and the like have been nearly run down by Tornados who have been receiving a RIs but ATC couldn't see the non transponding aircraft in the way. SSR and mode S in particular will give better data for RAS / RIS and even FIS.

<img src="tongue.gif" border="0">

[LowNSlow]

2 six 4 do Tornados receive an RIS at 500' whizzing down the Welsh valleys? Don't think so.

Iron City, thanks for the offer but I fly for fun and mummy doesn't let me out on dark stormy nights.... <img src="wink.gif" border="0">

Don't get me wrong chaps & chapesses, I think transponders are good things. When I had an aeroplane which I took to concrete & tarmac airports the first avionics upgrade was a Mode C addition to the transponder. However, I have a radio in the current wunderplane which seems to be enough for LTN, what is Mode S going to give me for all the pounds I'll have to spend fitting it?

[niknak]

Do you know what you'll be flying in 2008? I'm sure as hell that I don't. <img src="tongue.gif" border="0"> . .Obviously forewarned is forearmed, but look at the reaction to and the cost of GPS whenit was first introduced and the consequent reduction of price and improvement of quality.. .Don't panic Mr Manoring :)

[Tin Kicker]

It'll keep Eurocontrol off your back, haha.

[LowNSlow]

niknak, whatever it is it'll be old and probably lacking electrics. :)

Tin, I stay well away from them <img src="eek.gif" border="0">

Iron City, if there is no requirement to transmit HDG and airspeed, what is the "advantage" of Mode S over Mode C? <img src="confused.gif" border="0">

[SimJock]

I believe that two Mode S's can communicate with each other and issue both a/c with traffic avoidance advice, and display it, if you wish to fit further equipment.

It will also contain a unique a/c code that identifies your a/c to ATC so big bruv can see where you fly to !

[Mr Simple]

Sorry, but I don't have any faith in the closed shop that is aviation avionics to do anything other than screw GA for as much cash as they can muster.

Our club are currently trying to upgrade 1 (yes one) radio to FM immune status in an ac. To get a secondhand factory refitted one installed entails a mimimum price of ......UKP2500 ($3500).

$3500 for what is no more than consumer electronics, and not even state of the art.

Imagine the outcry if the govt demanded that all cars be fitted with UKP2500 radios before they were allowed out at night ? They wouldn't dare, but it's OK to demand additional costs out of GA, because they're just rich boys having fun .. aren't they ?

As an ATCO, I don't see any advantage in mandating Mode S for ops outside Class A+B.

[LowNSlow]

So, it appears from your comment Mr. Simple, that apart from ATC being able to see my registration (which they would know anyway cos I would have been talking to them) there is no advantage over Mode C. Which is what the rest of GA are saying as well.

I was going to fit a low power consumption Mode C transponder to the trusty Auster. Probable cost around GBP 1,500 ish. I'm certainly not going to do so until the Mode S issue is sorted. I'll remain the anonymous dot on radar screens around the country known only to London Info and the airfields that I always call when nearby. :)

[Capt Pit Bull]

Mode S transponders employ some cunning techniques to reduce the ammount of transmission, and the power of those transmissions. This has the effect of reducing the likelihood of garbling on the secondary radar frequencies which is good news for the ATC system in general, even if its transparent to the operator of a light aircraft.

CPB

[Iron City]

Capt Pit Bull summarizes it right. Mode S ("S" for "select") matters more to the engineers and techs, because the ATCOs and pilots see very little difference. The beauty of Mode S is in areas with lots of traffic you don't have to interrogate everybody with a transponder within 75mi or so, you just interrogate the ones you want to find out about.

The altitude feature for Mode C works just as well on the ATCBI "classic" transponders, but again reduces the amount of radio traffic when you can use Mode S. Mode S also has built into it's standards a data link. this is the thing that transmits more info to the TCAS II boxes and allows them to work their magic. It can also be used for whatever other uplinking/downlinking of data that is desired if someone decides to use it. Problem is the data link specification doesn't have lots of capacity (a limited number of bits and uses a lot of these bits for "overhead" communication management functions)

The economics of GA avionics are mind boggling to me. It seems that there is a certain cost for the up front engineering, certification and associated stuff that is outragous. Then there is the manufacturing cost for a radio (or whatever) which is more than for comprable ground stuff because of certification, reliability, etc. Then you have the installation which in many cases is pretty custom and the airworthiness certificate for the aircraft. If it is the same in the UK as over here the A&P mechanics/certified avionics techs are not getting lots of money (dollars, pounds, euros or whatever) so I would guess that it is because of the number of hours it takes to do it right and the lack of economies of scale that you have putting a radio (or a consumer type GPS for that matter) in an automobile. When the fixed costs of the engineering/certification is spread over 1,000 units (or even 10,000) it comes out to a lot per unit, lots more than for other comprable electronics such a amateur radios 2M FM putting out up to 50watts or so for $300 retail.

Because of economies of scale effects I was not kidding in suggesting that the GA organizations like AOPA get with one or more avionics mfgs and do a big order for a common design that will really get the fixed costs spread over a lot of units and make them more supportable over their life cycle.

[Warped Factor]

Iron City,

ATCO's will see quite a big difference with the intoduction of the Mode S datalink.

In a suitably equiped aircraft with an enhanced Mode S transponder we'll be able to access all sorts of stuff like MCP selected level, actual IAS/TAS/Mach No, actual heading and rates of climb/descent/turn to name a few.

Mode S promises a number of safety and efficiency benefits to ATCO's working in busy IFR environments.

WF.

[ 20 February 2002: Message edited by: Warped Factor ]</p>

[Iron City]

Warped Factor:

That information from enhanced Mode S equipped aircraft should make it possible to use some of the new tools and features being developed to improve capacity and flow. . .That info comes down the DL in parallel with the ATN data link information and is reltively few bits. Believe the ground system has to ask for the data on the uplink and there is some handshaking and error checking protocol.

This info is not available from the low end GA crowd because there is no ADC, FMS or similar to talk to the transponder and provide the information to it. Question still remains on the smaller fellows of the requirements for avionics fit and what avionics the Piper Cub (for example) must have, should have, is best practice to have relative to the airline equipment and military equipment.

In US it is the military equipage (or rather lack thereof) that scares me the most . Looking down from your C-150 into an AH-1 on a low level mission is very upsetting. The only thing worse is then recalling they travel in packs of at least 2 and looking for the other one. Amend that, the more worse thing is not seeing them at all and having a midair.