Mode S Transponder

[Golden Rivet]

Studying for more exams and was interested in Mode S operation and displays, so I contacted the Tower for some info and possibly a visit. Unfortunately my my local airfield does'nt have a Mode S transponder.

Just wondering how many Airports in the UK have an operational Mode S transponder .

Thanks

[Carbide Finger]

Rivet,

Surely you mean a Mode S radar. The aircraft carries the transponder.

Carbide Finger

[Golden Rivet]

Okay Mode S Radar.........:ok:

[300-600]

GR.
Don't know about ATC but at Paris CDG we now have to select mode S on the ground before taxying.

Don't know of anywhere else that does this...probably a reaction to the Shorts accident there.If they really wanted to make it safer they would stop speaking French and increase everyones situational awareness.

[Spitoon]

It's more likely to be to do with surveillance systems for ground movement etc. I think you'll find the same applies at Heathrow.

[Little One]

From what I know about mode S from an intro course that I recently did it uses the normal Mode C reply for airborne radar displays (ie Tx squawk code and altitude readout with the return echo on 1090mHz {I think} alternating between replies) but then can also Tx on a VHF data link which would be ground based and this info can be displayed on the ATC monitor.

Still very new technology as far as I know and not used widely yet although we in SA are apparntly looking in to obtain a system so it is slowly being implemented

[Llamapoo]

My understanding (and I'm happy to be corrected) is that Mode S has been a solution looking for a problem for up to 20 years (!!). Because it's a VHF datalink though, we're increasingly in a position to make better use of it, so its time seems to have come.

I also think it's in NATS' plan to upgrade all radars to include Mode S receivers (among other things). I think all aircraft with TCAS v7 have Mode S (which was a surprise for a KLM crew I flew with, once they got out the owner's manual) so mandatory use of Mode S will not financially inconvenience the largest carriers, or those who fly to the States.

There were also some threads on the procedures surrounding its use at Heathrow - but I can't post the link because I can't seem to search the forums right now. Worth doing later if you're interested though.

Hope this helps, and apologies if any of it is slightly inaccurate:uhoh: .

[Carbide Finger]

From what I have been told the Mode S transponder will reply with a unique transpoder code to that aircraft. Also other useful information like cleared level and current level (as in mode C).

I don't think you could count Mode S as 'datalink'. It purely provides it's information to the radar head when interrogated. I stand by to be corrected.

CF

[Over+Out]

Mode 'S' transponders are already in TCAS equipped aircraft.
Enhanced Mode S will downlink certain parameters to ATC Area radars, from the FMS, such as altitude, selected altitude, IAS, ground speed, heading and I think also altimeter pressure setting. NATS will have its first Mode 'S' Area Radar in about 2005.
I believe the LHR ground radar is a Mode 'S' radar already.
The information downlinked will not be corrupted as each individual aircraft will be addressed by the ground radars. No garbling of labels.

[SpamCanDriver]

Doesn't mode S also co-ordinate TCAS RA's between the 2 aircraft
ie it gets one to climb and the other descend depending on the speed position and performance of the two aircraft:cool:

[RaRadar]

OK heres the list of currently installed Mode S radars:

In the US all airports with an ASR-9 radar are Mode S (around 100+). Their en-route sites are also now being updated.

In the UK - none, but the upgrade to Mode S has started.

In Europe - Frankfurt, Munich, Geneva and Schipol with more following soon.

There are some experimental Mode S radars at Gatwick, Dusseldorf, Toulouse and Orly. Also a few manufactures have test systems.

They will all start with 'Basic Surveillance' which means just getting the Mode A code, Flight Ident and height via the Mode S link. In Europe, they will transition to 'Enhanced Surveillance' which can download various aircraft parameters when the aircraft have been updated.

RR

[Golden Rivet]

Many thanks - have been playing with Mode S transponders for years now on aircraft, always assuming the ground radar was similarly equipped.

I'm astounded :eek:

Cheers

GR

[Lon More]

For more info than anyone could possibly want on this, do a Google search with "Eurocontrol Mode S" as subject

Lon More
More than just an ATCO

[Iron City]

The Mode S transponder will respond to the ATCBI interrogation just like any ATCRABS transponder. The Mode S interrogator on the ground will do discrete address interrogation (Hence the S for select, used to be DABS -Discrete Address Beacon System) and get discrete replies from Mode S equipped aircraft operating in Mode S. There is indeed a data link built into Mode S.

When TCAS was invented the needed to be a way to get aircraft to coordinate for resolution advisories. The TCAS is a separate box in the aircraft and talks to thransponders (all kinds) in other aircraft. When a traffic alert is needed it gives it and if the other aircraft has a TCAS can cooperate on a coordianted resolution advisory for both/each aircraft. The coodrdination is over the data link


Another application of this data link is for automatic dependent surveillance braodcast (ADS-B) This is still another box on the aircraft that gets the aircraft location and some other information from other boxes on the aircraft (GPS, intertial, RNAV, etc) and sends it out to anybody listening. To do that need a data link and the Mode S extended squitter on 1090MHz is one of the data links used in experiments in the U.S. and looks the best option. If a bunch of airplanes are so equipped then they can tell each other where they are and the information can be displayed in the cockpit and everyone can "see and avoid" . You can also take these automatic position reports and send them to ATC facilities who can then use them for ATC.

[ChrisDobison]

Just to add my 2p in on this rather old topic :-)

I'm currently at the College in Bournemouth and in covering CAT II/III ops recently, Mode S came up. As many have already stated, UK does not currently have the equipment to accomodate Mode S transponders...not heard anything either on when they expect to have the gear upgraded.

Consequently, it means the UK has no CAT IIIc ops as the requirements are to complete a fully automated landing, rollout, vacate runway, and automated taxi...still would love to know how this can work - hopefully someone with experience can explain? Is the aircraft taxied using FMC points in co-ordination with transponder Mode S for GMC surveillance?

Would love to see this demonstrated - would bring a whole new meaning to "zero vis procedures"!!!


All the best,


Chris

[Point Seven]

Chris

Not entirely correct. The ASMGCS (or AGCS in Paris) at Heathrow uses Mode S information to provide a retutrn on our advanced SMR. It allows us to provide more accurate taxi and runway utilisation in low vis.

Down at Hurn, NATS are doing big research into Mode S on TMA radar, using it to display subsidiary information such as rate of descent, cleared to level, IAS and the like.

As usual, the college are a mile behind. Mode S can be used, WILL be used by the time you are valid and is almost certainly the future of ATC.

P7