UK - MODE S and battling level busts

[ahwhataloadofsugar]

Just a quick question for the guys in manch and london who have the lovely tool of mode s,The scenario... if you gave a cleared flight level to an a/c and they read back the correct flight level to you but dial in the incorrect one on the a/c and you pick it up what is the procedure for this taking into account you pick up the mistake before a level bust do you just re-confirm cleared level? Or is there an sop? and another question once you have given the fl do you check on the scope every time that the a/c had set it correctly?

Thanks in advance guys

:ok:

[landedoutagain]

'Check selected level and confirm climb/descend FL xxx'

The only other thing i do differently is instead of giving a level, then transferring to next sector, if workload allows then i will wait to see if they have the correct level. Saves the pilot taking the first call, leaning across to set new level and get called back with a freq while still setting the level!

LOA

[tczulu]

Not quite the greatest thing since sliced bread though.I can see what the selected level is thanks to "mode s",but if it's low pressure and crews don't select 1013mb when cleared to a flight level,it can lead ATCO's into a false sense of security that the a/c will level at the instructed Flight Level.Been there,done that!No substitute for monitoring rate of climb against traffic 1000' above cleared level.(assuming we have time to do so!):hmm:

[Max Angle]

Out of interest, how fast does the display update?. On a two crew aircraft you can assume that the level is dialled up within a second of the call being received so how long does it take after issuing the clearance before you see the selected level change on the screen.

[landedoutagain]

Can take up to 25 seconds says the book, but in practice i dont think i've ever had to wait more than about 10 -15. Usually about 5 or so. Whats off putting is when it catches you halfway through the change eg, drop from 220 to 130, and SFL promptly changes to (say) 120.... Usually its correct at the next refresh, or you get a call obviously! More often than not, if it does pick it up as you are changing it it'll say something blatantly wrong that doesnt end in a zero.

And if you fly a saab with a dodgy txpdr, we know to ignore the sfl! :)

[Radarspod]

Now for the nerd answer!

Assuming taking from point where has been dialled in on MCP and register has been passed to the aircraft transponder:

Slowest Mode S ENHS radar feeding the TMA is 8 second scan rate. So if pilot changes just after last detection, worst case 8 seconds before radar downlinks the SFL register.

Radar allows for up to 2 seconds between detection and output to allow for the longer time required by the primary radar to process its data and the combined data to be output.

Data to get to centre is measured in milliseconds, so will discount.

Data processing works on 4 second cycles, so worst delay there is 4 seconds.

Maximum time to present to controller should be 8+2+4 = 14 seconds. In practise is much less as multiple radar sources extracting data.

RS

[ahwhataloadofsugar]

thanks for that guys,

[Dont Hang Up]

...if it's low pressure and crews don't select 1013mb when cleared to a flight level,it can lead ATCO's into a false sense of security that the a/c will level at the instructed Flight Level....Been there,done that!


Slightly disturbed by this.

Surely controllers have been trained that Selected Altitude is ONLY used to confirm a vertical clearance has been received and correctly understood.

There is no guarantee whatsover that an aircraft approaching its selected level will level out other than the normal faith in flight crew competence. The aircraft may be being flown by hand for example - the value being entered into the MCP only as a matter of procedure.


No substitute for monitoring rate of climb against traffic 1000' above cleared level.(assuming we have time to do so


Indeed. True before the availability of SA and just as true now.

[skyman01]

Had one yesterday - a/c climbing to SFL180, levelled at FL184 because pilot still had QNH set at 997! Watch out guys!

[Ivasrus]

Is pilot selected QNH transmitted in Mode S returns, perhaps as one of the dozens of measures that isn't displayed to ATC? One for the techies.

[landedoutagain]

Ivasrus - No, its not.

There might be selected frequency in the future though (hopefully!)

[Radarspod]

Sorry, have to disagree.

Pilot selected baro IS DOWNLINKED via Mode S where it is available. Barometric pressure setting is part of BDS 4,0 - the transponder comm-B register that also contains Selected Altitude. Unfortunately, European policy makers in their infinite wisdom decided not to mandate the baro setting as part of Enhanced Surveillance. :ugh: As such it is not displayable to ATC as it could not be counted as being reliable data.

A shame really, as it could be a useful piece of data to provide a controller tool to indicate a pilot operating on wrong QNH when transitioning from 1013mb.

RS

[anotherthing]

As an ATCO working in the LTMA, I would not want the Altimeter subscale setting on my radar - enough clutter as it is. What we have is useful. We don't need anymore! It doesn't happen that often, and spotting these things is one of the many things an ATCO gets highly trained and well paid to do.

Selected frequency, again is not needed and would clutter up the screens too much.

Mode S is a safety enhancement tool, not a replacement for good ATC practices.

Don't Hang Up


Slightly disturbed by this.

Surely controllers have been trained that Selected Altitude is ONLY used to confirm a vertical clearance has been received and correctly understood.
That's not how Mode S is used. The SFL is used to check that a pilot selects the FL you have instructed him/her. It is a confidence check. ATCOs still monitor a/c on radar!!

All Mode S does (and does it very well) is add another safety level, and in the case of SFL, helps prevent some of the level busts we previously had by confirming the SFL correlates with the instructed level.

ATCOs still prevent level busts caused by pilots manually flying the aircraft and going to the wrong level or by busting a level due to incorrecty QNH. With Mode S, we now prevent some level bust from happening before they even get near to it!

[landedoutagain]

Anotherthing spot on there - I should have said about the frequency selected that I believe it wont be in the data block (that would def be too much clutter!), but available in the box where you can look at all available parameters, which isnt used that often anyway but occasionally comes in handy! I presume TC have that box minimised too most of the time?

[anotherthing]

landedoutagain -

That option makes more sense. I think I can categorically state that no one in the LTMA has the Mode S box permanently open.

In fact, the only time I use it nowadays is to show visitors what we can see - i.e. instantaneous ROC/ROD etc.

The NODE interface is such a pain anyways - trying to highlight the a target aircraft can be onerous because of the highlight toggle on/off on the master palette. I find that when I want a solid box i.e. to select an aircraft (say to force it into a stack list) I have the highlight selected so get a blue hatched box... or vice versa if I'm trying to do something else :ugh:

The problem with the next frequency is that it would need to be input manually into the system because depending on adjacent sector configurations at that point in time etc, the frequency could be different.

I suppose working a T&P system would give more scope for that, but to be honest at TC it's (the frequency thingy) not needed.

I think LAC have the ability for a quick look on taget aircraft for the next frequency, but obviously they work on electronic offers and the T&P system.

[PPRuNe Radar]

The problem with the next frequency is that it would need to be input manually into the system because depending on adjacent sector configurations at that point in time etc, the frequency could be different.


I think there is a slight misunderstanding here. The Mode S would send down the frequency which the pilot has selected, not what you want him to dial up next. Useful if you get a Loss of Comms (PLOC) since you know where he might be RT wise, but not much else.

[anotherthing]

Cheers for clearing that up - completely my mistake getting two totally different things mixed up!!


Only problem with knowing the frequency they have gone to/dialled up in the event of PLOC, is

a. Are the numbers they have dialled actually a frequency

and

b. Do you recognise who they belong to, so you can call them!

Possibly not much use IMHO

(Vote NO)

[Minesapint]

We CTC filth will be kicking off a project soon to come up with new and exciting DAP's. Any suggestions (selected pressure setting, SID/STAR etc) ar most welcome.

[anotherthing]

Minesapint

Check your PMs :ok:

[Radarspod]

Can I suggest that whoever is busy inventing weird and wonderful applications with requirements for new DAPS come and talk to those that actually provide the mechanism that gets them off the aircraft.

If you want another more than a couple more new DAPs, you are going to have to start saying goodbye to some others! :ok:

RS

[Minesapint]

Always do!!!

[Radarspod]

Just making sure :}

[Minesapint]

How many DAPS are available then? I know that some of the current DAPS seem to be pretty useless to the controller as they are (roll angle...), if it's a case of just replacing good with bad it will be good to know how many new ones we canhave on top of what is already available.

[Radarspod]

Minesapint,

The current 8 or so DAPs mandated across Europe as Enhanced Surveillance capability are supplied via 3 BDS registers held on the transponder. Each of these registers requires an interrogation to be made to obtain the content.

BDS 4,0 Selected Vertical Intent - Selected Altitude, Baro Pressure setting
BDS 5,0 Track and Turn Report - Roll Angel, True Track Angle, Ground Speed, Track Angle Rate, True Airspeed
BDS 6,0 Heading & Speed Report - Magnetic Heading, IAS, Mach No, Baro Alt Rate, Intertial Vertical Velocity.

Any other DAPs would have to be obtained by downloading further BDS registers, of which many are as yet undefined or not yet stable in agreed content. The problem is that the Mode S interrogator being deployed can only perform fixed period extract of up to 4 BDS registers (outside of those needed for Elementary Surveillance). 3 have been taken up already as above, so only one more register can be downlinked from the interrogator. It may be that to obtain other DAPs from other registers, someone actually builds a Ground Datalink Processor (GDLP) to connect to interrogator as Mode S was intended, or overlapping interrogators will have to interrogate for different DAPs to get them all down to the SDP system that presents the data or uses them in controller tools.

Alternatively, if one of the registers has content that is not much use, then it could be ditched in preference to another one but the airlines would be pretty annoyed if they kitted out for it and the info is not used.

Either way, it's not as straightforward as looking at new DAPs and saying "we want those" :}

RS