Approach speed control in STN
 

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:
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.

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

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. :)

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

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...

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

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.

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!

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:

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.

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:

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

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

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.

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

Quote:

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4. Tactical Application Of Speed Control By ATC

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5%
 

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:

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

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:)

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

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.