Mode S capability

[skyman01]

Having just acquired the use of mode S at Manchester Centre, I wonder if someone could explain why some A/c with "enhanced" mode S don't display all of the downloadable parameters automatically. Is this a function of the selection on the transponder on the flight deck?
This doesn't appear to be a factor of which fleet the a/c is from - I had two BA A320's on frequency the other day - one displaying all the parameters, the other only showing IAS and GS, no hdg or SFL (selected flight level).

[westinghouse]

hi,

well it depends on the transponder onboard. it might be an older one.
im not really sure abt the answer.
im more curious on what exactly youll can see with the enhanced mode S.

thanx.

[skyman01]

Enhanced Mode S allows us to see Selected Flight Level, Hdg, IAS and Groundspeed - I just want to know if there is a setting on the transponder which doesn't permit the display of all these parameters, even if the a/c has enhanced capability.

[Radarspod]

Not all aircraft are capable of supporting all of the Mode S DAPs, and as such certain information may not be available for downlink. There is no mechanism on the flight deck that I am aware of to inhibit supply of DAP - the transponder only has access to them if the avionics fit allows. This is quite common of some older airframes, which have been exempted from providing certain DAPs if not practical to provide.

From MACC Node-L Mode S info display point of view, an aircraft flagged as being ENHS capable means it is capable of providing at least one DAP, not necessarily all of them.

You should see compliance increasing over time, something like 85% of all mode S aircraft are now supplying at least one DAP.

[zkdli]

hi the reason that you can't see all the DAP on some aircraft is that some of them have not been wired up to downlink all of the parameters. EG BA Gatwick jets are on a maintenance program to have all the parameters downlinked as they go for major maintenance. Eventually they will all show all DAPS it is just the maintenance schedules. if you see some that don't downlink, go to your safety department and get them to talk to the airline - they will need the flt number and date etc so that they can advise the airline that a specific airframe is not yet wired up:)

[WhatUMean]

you often see on the end of the flightplan if a particular a/c doesnt have all the features available.