Approach speed control in STN

[Telstar]

I had the approach controller snarl at me on the ILS recently. I grew concerned as we were inside 4 DME and hadn't been changed to tower, so asked if we could. Controller "I was just waiting to see if you were going to bother yourselves to slow down but never mind, contact tower now 123.8"

I had been asked to maintain 160 Kts to 4 DME as always in STN, having read the very long debate on R&N about people who don't and the problems it causes I understand this perfectly. On this day we were heavy and bug speed for flaps 10 was 165 Kts which we had set as soon as instructed and achieved quite quickly, less then 10 secs. Now my company airfield briefing says:
The high weight flap 10 speed is
164 knots (-800). This is acceptable to ATC as 160kts speed required.

This is the only thing I can think of that got the approach controller into such a state of agitation.

I am well aware that ATC merely require us to inform them if we can't maintain 160 to 4 instead of slowing early and they will accommodate us, but if our company liaises with ATC and they say 165 to 4 is acceptable, what's the problem? I have no problem putting the Gear down and flaps 15 out at 10 miles and keeping the speed at 160, and the thrust and noise way up but it seems a bit pointless to do CDA approaches and then do that.

It wasn't the time or place to get into a war of words but I was extremely rattled as I was so angry and considered going around, it was a very snotty and aggresive tone of voice. In hindsight I should have made an effort to speak to him by telephone afterwards.

[CloggyUK]

Hi Telstar,

I'm not an approach controller, so i don't know what happened. Some unofficial feedback.

It wasn't the time or place to get into a war of words - I agree with you on that, always bad practice from either end of the radio.

but I was extremely rattled as I was so angry and considered going around - Would a go-around have been the best option? You could possibly have been distracted, and (depending on traffic levels of course) there could have been all sorts of heading and levels to sort you out agains departing traffic. This could have led to dangerous situations.

In hindsight I should have made an effort to speak to him by telephone afterwards. - In future please do. Ask for a phone number when you're speaking to the ground controller. If you don't want to say what you need it for, don't, we'll discuss it on the phone. We are always happy to make an effort to sort these problems out, that way it will be of your mind. If you would have to do more flights, you can fully concentrate on them.

Hope it's any help. Don't hesitate to pm me if you want more info.

cheers, C

[zkdli]

Hi Telstar,
I note that your company procs state "164 knots (-800). This is acceptable to ATC as 160kts speed required."
As far as i understand, this has not been agreed for LTMA airfields, if it was it was in the dim and distant past and needs to be renegotiated:)
I do know that we are setting up a working group with airlines to try to figure out the best compromise of speeds on final so that ATC can land the required number of aircraft per hour and aircraft can have a stable approach by 1,000agl.
BUT until that has been agreed the AIP for all LTMA airfields says that pilots must fly speed instructions accurately (with no leeway). If they are unable to do so they should inform ATC. :)

[DFC]

The international standard is that when required to maintain or where a pilot has informed ATS that they will maintain a specific speed then they are considered to be maintaining that speed when within 5% of that speed.

5% of 160 is 8Kt.

Thus 160 knots is maintained by keeping the speed between 152 and 168.

Yes in many cases we do better than that.

However, those are the allowances and in most cases, ATC would not know the difference between 160 and 165 with the changes in wind etc affecting groundpeed which after all is what ATC are really interested in.

If this ATCO has a problem with the speed being 5 knots high then he should have slowed the flight by 5 knots.

Sounds to me like an ATCO at TC who uses the selected speed readout of mode S and was not impressed by the selection of 165 when 160 had been requested.

Regards,

DFC

[Roffa]

DFC, got an ICAO reference for the 5%? I've just had a quick look at my docs and couldn't see anything, but it was quick. Just that a 20 knot speed difference between two a/c if one is flying at the lower end and one at the upper could prove embarrasing to all at minimum spacing.

FWIW, the UKAIP says this for the main London airports, and I quote...

Speed Control: Pilots should typically expect the following speed restrictions to be enforced: 220 kt from the holding facility during the
initial approach phase; 180 kt on base leg/closing heading to final approach; between 180 kt and 160 kt when established on final approach and thereafter 160 kt to 4 DME. These speeds are applied for ATC separation purposes and are mandatory. In the event of a new (non-speed related) ATC instruction being issued (eg an instruction to descend on ILS) pilots shall continue to maintain the previously allocated speed. All speed restrictions are to be flown as accurately as possible. Aircraft unable to conform to these speeds must inform ATC and state what speeds can be used. In the interests of accurate spacing, pilots are requested to comply with speed adjustments as promptly as is feasible within their own operational constraints. Pilots should advise ATC if circumstances necessitate a change of speed for aircraft performance reasons.

[Telstar]

zkdli The airfield briefing is specifically for STN, not a generic UK airfield briefing.

[Roffa]

Telstar, when we're operating at minimum final approach spacing we have an 880yd buffer between perfection and setting the snitch off with the associated possible suspension whilst it's investigated (think guilty until proven innocent).

That's not a lot in time or distance at the speeds being flown and whilst I in no way excuse the STN bloke for having a go at you on the r/t it is one reason why we can get a little touchy about how accurately final approach speeds are, or are not, being flown.

[Telstar]

Roffa Well since FR is the biggest operator in STN may I suggest you contact their liason officer as we are being instructed, as above, that we can maintain 164Kts when heavy. I just felt a bit hard done by as I was only doing as instructed in Part C of our Ops manual and got a bollocking. Sniff, sniff :{

From now when heavy, it's Gear down, Flaps 15, and maintain the bug speed for those extra 5 knots, and the power to match it. Damn the noise!

[Del Prado]

Telstar, if you mentioned 165kts to 4 miles when you were downwind I'm sure the controller wouldn't mind, in fact, they'll probably catch on after a while.

BTW, having a go at a pilot in the air is never a good idea especially not 2 minutes from touchdown.:eek:

[Roffa]

Telstar, as Del P mentions all it takes is a quick word on the r/t and any speed different from the "norm" will be easily accomodated.

Ideally get the call in before you're on base leg as it's the base to final turn timing that dictates the spacing on final.

There was a time when some 737 operators seemed to prefer 170 to 5. The only problem that caused ATC was that it wasn't applied consistently across airlines or similar types. Perhaps the one thing that is really necessary for tight spacing and high landing rates is everyone doing the same thing for the last 15 miles or so of the approach. Too many variables and capacity is reduced.

[mr.777]

BA still like to do 170 to 5DME in my experience at KK...never a problem as long as we're told on the downwind leg.
What can be annoying is when, during prolonged sequencing, they call established and ,when told to reduce to 160 to 4DME, they then get all uppity at not being able to do 170 to 5DME. Most of the time now I will build in an extra 1/2 mile of spacing in anticpation of the request which keeps everyone happy!
It's really no problem for us but please let us know well in advance!! :ok:

[Telstar]

Thanks for the replies everyone, I have learned something useful.

[loubylou]

While I agree that there was no need to for "tone" from the controller, I think you should have said that you'd be doing 165kts instead.


DFC - can you say where this mythical +/- 5% for speed is written please? I think it's something that is a bit of an urban myth to be honest - especially these days when speed can be more accurately flown and indeed aircraft are being vectored much more closer together than years ago. Just how happy would you be having been vectored to min vortex wake against a heavy - to find that it's doing nearly 20kts slower?:hmm:

Funny how no one thinks that there's +/- 5% on headings or levels!! FL160 = anywhere between FL152-168?:ugh:

louby

[Gonzo]

FL160 = anywhere between FL152-168?

No, but FL158 - FL162! :E

Sorry! I actually agree with you, no point having a 'speed range'. If you can fly it, then fly it; if you can't fly it, tell us.

[PPRuNe Radar]

There is a bit in ICAO Doc4444 which mentions speed tolerances, but then throws it back to the relevant ATS authorities to specify them :)


Use of Radar in Air Traffic Control Service - Functions

7.1.1 g) maintain radar monitoring of air traffic;


Note.— Where tolerances regarding such matters as adherence to track, speed or time have been prescribed by the appropriate ATS authority, deviations are not considered significant until such tolerances are exceeded.

No specific figure for tolerance published = no tolerance or leeway in my book. :ok:


Anyone able to point out that the CAA do in fact publish a tolerance level for the UK ?? All I can find is the stuff in AIC 53/2004, which is a straight lift from text in ICAO Doc 4444 again, namely:


4. Tactical Application Of Speed Control By ATC

4.1 In busy traffic situations it is necessary for ATC to limit aircraft speeds for traffic sequencing purposes and reduce the need for aircraft vectoring. Controllers will consider aircraft performance limitations in issuing speed instructions. Specific speeds should normally be expressed in multiples of 10Kts.


4.2 Only minor speed adjustments of not more than +/- 20Kts should be requested of an aircraft established on intermediate or final approach.Speed control shall not be applied within 4Nm of the threshold on final approach.



4.3 Aircraft unable to conform to the speeds specified by the radar controller should inform the controller immediately and state the speeds which shall be used.

[RadAlt]

I believe the 5% tolerance comes from the cruise-phase. If your TAS differs more than 5% from that filed in your flightplan, you have to let ATC know.
I recall something like this from my days learning airlaw, but that's awhile back now, so I could be wrong.:hmm:

[DFC]

RadAlt you are correct. The 5% applies to cruise. It is 5Kt on approach according to the CAA.

On approach the CAA expect a competent pilot to keep the speed within +/- 5 Kt.

The source is the CAA examminers standards.

Regards,

DFC

[zkdli]

Hi DFC:)
the examiners standards are just that; for when they are examining for a flight test!!! AS the UK AIP states for aerodromes in the london TMA, speed instructions are mandatory:) As PPRUNE RADAR has shown there is no tolerance expressed in the UKAIP therefore if the pilot cannot fly the speed exactly, then ATC should be notified. In the LTMA speed control is used to maintain separation. When ATC are using 2 1/2 nm spacing it can go to a can of worms very quickly if the front aircraft is 10kts slower and the back one is 10kts faster:)

[Del Prado]

if the front aircraft is 10kts slower and the back one is 10kts faster

That's the only way I can manage to get them 2.5 miles apart.:E

[HEATHROW DIRECTOR]

DFC... nobody is talking "CAA Examiners Standards".. just read what it says in the AIP. I don't condone irritability on the R/T but I DO know what it feels like to be doing 2.5nm spacing when some prat decides HE knows best without telling me - it's bl**dy scary.

[jonny B good]

I'm a Tower controller at STN. I am unaware of any agreement re 164kts vs 160kts but will look into it if someone hasn't already done so.
The problem with speed not complied with is when we have a large number of inbounds, we will 'pack' to 3nm on final. Any erosion of this spacing is then a loss of seperation, whether it sets alarms of or not. It can also easily lead to go arounds as there may not be suffiecient time for the preceding to vacate.
Equally, there is NO excuse for the app controllers reaction. If they were monitoring you because they had an issue with your speed, they should have done something about it rather than just let it run until you were inside 4 dme.
Anytime you have any problems, feel free to give us a call in the VCR and we'll do our best to resolve it.
Cheers, JBG :8

[Mister Geezer]

Interesting article in CHIRP from a ATCO highlighting poor speed control and possibly alluding to SS since he noted that he has seen 320KIAS on passing BKY!

To those crews who fly into any of the London airports.... just play the game since with Mode S providing IAS data to the guys and girls who are controlling you it is not possible to bull5hit anymore!

[Roffa]

Interesting article in CHIRP from a ATCO highlighting poor speed control and possibly alluding to SS since he noted that he has seen 320KIAS on passing BKY!

It's not uncommon for traffic in to the LHR holds to call approach a few miles from the beacon saying they're doing high speed, having been approved by the TMA, only for approach to say enter the hold delay is x minutes.

It's not always the pilots at fault, depsite the fact TMA and approach have been sitting in the same room for over 10 years now we're not very well joined up at times.

[I Just Drive]

Jonny, is it only groundspeed you can see? Also do you know what speed the mode S will be reporting? Is it actual speed or selected speed?

And I think you guys do a great job by the way. Sorry for sucking up. And sorry that we don't make enough of an effort listening out on the ground frequency on stand!

[Telstar]

To those crews who fly into any of the London airports.... just play the game since with Mode S providing IAS data to the guys and girls who are controlling you it is not possible to bull5hit anymore!

Is it selected speed or actual speed readout? With Vertical speed selected you can set the speed at 210 in the MCP but still be doing 300 kts with a V/S of 3000 FPM for example. Not saying I would do this , just saying Mode S might not be foolproof.

[AlanM]

Ahh but Telstar. We have selected speed as per the Mode S for equipped aircraft, and groundspeed which we have always had. (comes off the radar returns but is fairly accurate (we often ask aircraft for their GS))

We tend to build in wind/descent rates into the thoughts when muttering to ourselves that you haven't slowed down! :)

[390cruise]

I have been a Stansted based pilot for many years and have a strong
regard for the professionalism of the all the controllers there.
This includes the Delivery,Ground and Tower who are based in
Stansted control tower and also Director and Essex radar who are
for now still at West Drayton.

However within the last few weeks there is ONE of the radar controllers
who (it seems to me) has an attitude problem.He makes comments which
are quite offensive.

The comment 'I was waiting to see if you were going to slow down' fits
that type of comment.

I would suggest that NATS identify him and provide any required re training.

Kind Regards

390Cruise.

[zkdli]

Hello Chaps,
Mode s downlink shows Indicated Airspeed from the ASI, the aircraft heading, the ground speed (if the aircraft is not mode s equipped it will show radar derived ground speed). It will also show the actual rate of climb or descent of the aircarft and the Selected Flight level from the MCP.
Hope this helps.:)