mode s
 

Need some info - what info does ATC receive with regards Mode S Transponder info from aircraft in flight ie IAS (Selected or actual IAS) etc

Tks

GP

I too would be interested in this, I assume you get something akin to what we see on our MCP (the autopilot windows).

If this is the case, can you also see inputs when we are flying in VNAV/LNAV (or managed for airbus types) i.e. when the actual value selected is by our knees in the box, and not on the mantelpiece.

Horgy

From memory we (Terminal Control) see downlinked your MCP selected flight level, actual IAS, actual heading, ground speed and actual ROC/ROD.

We also get flight ID as well.

Your system may also be sending more data down to us but at the moment it is not displayed to the radar controllers.

Roffa's memory is not wrong :)

The 24 bit airframe address is obviously also there - but I don't think it's enabled for display at many of the positions in the TC ops room.

There may well be other items of data being downlinked from the airframe, but none of them are (currently) extracted from the data stream for display.

CS

I believe that London Control has this feature which enables them to display the selected MCP (Mode Control Panel) speed, altitude and more.

I was told by a fellow pilot working for another airline that his captain mentioned that when ATC give him the speed restrictions such as 210 he dials this into the MCP "too keep the controller happy" and then proceed to descend at a faster speed. Now obviously if the controller wanted to enforce it strictly he could determine the speed difference from the ground speed if not the actual IAS if thats even possible but i digress.

This feature also has the benefit to prevent alt busts, especially the ones where pilots read back the correct cleared level and then dial up an incorrect level on the MCP.

Initially I thought what he said had to be a mistake, but after speaking with some controllers they said that despite this technology not being available in all UK centers that London certainly had it. Impressive to say the least.

On a different note could an controller enlighten me as to why there is not a better way to find out what cruising level is to be used by a particular flight. I often get calls asking whats our final level is, or prompting it in anticipation of being asked over the RT. Surly with the current data link technology and flight processing stripes I would have assumed that this information was available to controllers. Are you just confirming it with us or do you not know to start with?

I know that these levels can often change depending on the FMS optimal cruise level on the day as well as weather, commercial or traffic factors against the flight plan, perhaps this is why it is confirmed by ATC. Anyone?

Not all London Controllers have it. Just the TMA.


The Mose S link provides the actual IAS and not that input to the MCP. So even if your friend has 220Kts dialled into the MCP and is actually doing 240Kts, we will have the actual airspeed, i.e. 240Kts on our display.



The requested level from the repetitive flight plan is displayed on the flight progress strip but as the cruising level can vary from day to day, it is necessary to ask.

AKAF

Absolutely correct - Although occasional miracle workers we're not mind readers:cool::cool::cool:

Cruising Levels:

Your filed cruise level will be used in planning sector throughputs and capacities a long time before you get airborne. Any flow control action will be based upon those levels. Therefore it is important that they are as accurate as possible. Sometimes as little as 2000ft difference can put you into a sector which has not planned to have you there and this may push them over the edge in terms of workload. Therefore, it would be great if you could encourage whoever files the FPLs (if they are not RPLs) to ensure that the cruise level is accurate.

This is especially true of cases where a relatively low level (e.g. FL290) may be filed and ATC or the crew then ask for a higher one (e.g. FL370) when airborne. The controllers may be trying to help but they may unwittingly overload another sector 500nm down the line.

LAC at least has advice running at the moment that ATCOs should not climb traffic above its FPL level unless absolutely necessary (weather, conflicting traffic etc).

Will depend on aircraft fit:

Aircraft covered under ELS (elementary surveillance) equipage mandate will provide Mode S 24 bit address, altitude to 25ft if available, Mode A code, Flight ID and various status indications.

Aircraft equipped for EHS mandate will provide ELS plus all the IAS, Selected Altitude, Turn rate, ROC/ROD, Mach no, etc.

Where fitted, TCAS RAs and TAs are also broadcast to groundstations.

ADS-B squitter equipped aircraft also broadcast positions, Flight ID and Velocity vector.

Lots of stuff, much more useful than Mode A and Mode C!

RS

In the London TMA, aircraft are supposed to be Enhanced Mode S rather than just Elementary Mode S.

The information downliked by the Mode S radar heads is (avionics permitting):

MCP / FCU Selected Altitude
FMS Selected Altitude

The above are the only "intent" parameters. All the rest are "actuals" as follows:

Heading
IAS
TAS
Mach
Vertical Rate
Roll Angle
Track
Track Angle Rate
Ground Speed

Many of these are for "future use" either for display to the controller or to improve the radar tracking and prediction capabilities. However MCP Selected Altitude is currently being provided to controllers and I understand is considered by some to be the best thing since Mode A/C.

Nothing like this is defined in Mode-S, it is MCP only

Sorry, but FMS Selected Altitude is in there, although not currently used. EUROCONTROL are currently analysing how consistently it behaves across aircraft types and thus can it be effective for monitoring RNAV procedures.

Depends upon the aircraft, not the airspace. Lighter (<5700kg) and slower (<250 KTAS) aircraft are only required to have ELS in airspace where Mode S is now mandatory.