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speed control on final

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speed control on final

Old 7th Oct 2002, 22:58
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speed control on final

I'm getting a bit concerned with aircraft slowing down on final approach without being instructed. this can be in the form of reducing below 160kts before 4 dme, or reducing to 160 from 180 when established on the ILS.

In the last two days I've had three aircraft reduce to 160 before instructed.

First time the vortex gap was eroded and I had to break off the following aircraft and reposition. Thanks to the profesionalism of the lufthansa pilots behind we didn't lose any aircraft movements/ miles on the approach, but still a lot of work for me and therefore all the other aircraft on frequency.

Second time the aircraft increased speed again. This made the spacing difficult for the tower controller to judge so they didn't line up a departure. That means every departure at the holding point was delayed for an additional 2 minutes as the airport lost a movement.

Third time I had to take the following aircraft through the localiser then back for a shorter final than expected. again a huge impact on workload and RTF congestion.

Apart from the vortex erosion these incidents were not really a safety problem, but they could have been.

I've had a dozen of these incidents in the last year and almost half infringed vortex or standard separation. The most serious of which I was suspended from radar until a brief investigation was complete. All because a pilot didn't follow a clear and unambiguous instruction which had been read back.

I try emphasising "maintain 180kts" when clearing someone to descend on the ILS, although I feel the last assigned speed should be flown until instructed. (The extra two seconds to say "maintain 180kts" can mount up for 40 aircraft an hour.)

There doesn't seem to be any pattern in the airlines or fleets that are guilty (or nationality, these last three were british airlines and crew)

So what can I do ? increase the spacing (and therefore delays)?
MOR each aircraft that slows down ?
Shout at the pilot at such a critical phase of flight ? (I don't fancy being on a plane being landed by someone who has just had a bollocking)

This always appears to me a terrible breakdown in CRM, after all you wouldn't dream of changing a heading or level without instruction (or at the very least asking first) so why ignore a speed instruction ?

Sorry about the moan, the professionalism of aircrew flying into London airfields is generally fantastic, I'd just really like to know why tis happens and how to stop it happening again.

Phew, glad I've got that off my chest !
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Old 7th Oct 2002, 23:15
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I'm probably one of the culprits--we generally want the gear down and flaps 15 (737-300)by about 2000amsl and at that point reduce speed to 160 which is still 10 knots above the standard speed for that flap setting. It has become so common to be required at 160 to 4D that it is anticipated. We can't go all the way at 180 or the runways will need to be extended!
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Old 7th Oct 2002, 23:28
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Some airlines' standard operating procedures may be the problem here.
A few airlines are VERY dogmatic about stabilized approaches, expecting these to be established by the OM/FAF.
Many times this is not possible, LHR, AMS, FRA are perfect examples.
A little flexibility would/should be appreciated by "managements"

Oftentimes, this ain't going to happen, sad to say.

Newer modern jets do NOT have the spool-up time required of the older machines...and can recall some of these older machines, you could almost go out to lunch waiting for the required thrust.

Times have changed...but some do not.
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Old 7th Oct 2002, 23:31
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We should aim to have you at least reducing to 160kts at seven dme at the latest. The problems I've had are when pilots reduce to 160 at 9/10 miles or below 160 before 4. Although you should make a request to slow before doing so, even inside 7d.
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Old 7th Oct 2002, 23:36
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This can mostly be resolved by training and communication.

Many airlines (mine included) have an absolute requirement for an aircraft to be stabilised in the landing configuration by no less than 1000ft above the runway. That can be challenging with 160 to 4. Secondly, the "gate" is raised in IMC conditions.

I have taken to training all my guys that their role is to give you the speed you ask for, and manage the altitude themselves. Furthermore, I'm planning some visits for Training Captains to mwwt the guys in Gatwick/Heathrow Director to help them fully understand how you guys build a traffic pattern.

It's also worth encouraging pilots to notify ATC when they can't comply with speed requirements, or when (for example) they anticipate a slower than normal final approach speed (e.g. positioning aircraft)
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Old 8th Oct 2002, 00:05
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The other snag with some of the big busses is that the blighters refuse to slow down at all if there is a tailwind. That leads some crews to target V ref before 4 nms.

I accept that slowing at 9/10 miles to 160kts is too soon but an A-330 won't slow down on the glide if it has a 15kt tail wind. A lot of operators deal with that sitch on a regular basis especially when approaching airfields effected by a sea-breeze which after a few go-arounds tends to make them gun shy.

The crews may well be slowing to prevent themselves going round and obviously they should inform you first. Out of interest, how much of a buffer do you allow for stablisation problems?

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Old 8th Oct 2002, 02:34
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Here in Toronto the controllers always request "170 to the marker" and it doesn't seem to be a problem.
For a decelerated approach on the A-320, Airbus says enter 180 ("S" speed ) into the MCDU at the marker (FAF), so they seem to think the aircraft can cross the marker at 180 and be configured for landing by 1000 agl. It's knowing the capabilities of your aircraft and what you can do with it.
As has been stated above some airlines still want the aircraft dirty by the FAF. Great way to waste fuel.
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Old 8th Oct 2002, 08:20
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Cool Stable by 1000'

Was asked by EWR to maintain 190kts to the marker a couple of weeks ago - used my favourite ATC phrase "unable" and got the reply "OK speed as you like". It's just not possible to fly fast approaches to 4 miles and be configured and stable by 1000' in big jets such as the B777 and A330. Also bear in mind we have to answer to our monitoring department as each and every sector is downloaded and scanned by computer for exceedences such as these. The results are published monthly and we seem to get about 2 or 3 rushed approaches some of which result in go-arounds due to not meeting the rigid company criteria - hence crews eagerness to slow down early and avoid a mandatory G/A.
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Old 8th Oct 2002, 08:27
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and while we are on this subject-- I understand there is a 10knot tolerance on all speed requests?? I have brought this up before but will do again-- does it cause a problem if we 737 drivers use 170 instead of 160 to 4D?? This enables us to keep the gear UP and thus reduce noise and fuel consumption! We will still need to start slowing at about 6.5 miles or 2000 amsl to meet (our) requirement for stabilized flight by 1000amsl.

Last edited by lost soul; 8th Oct 2002 at 09:16.
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Old 8th Oct 2002, 10:11
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lost soul, why not take Flap 10 and fly at 160 kt?

OK it's not technically "standard" but perfectly safe and sensible in the circumstances.
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Old 8th Oct 2002, 10:50
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Ah yes this little chestnut.

I remember being shoehorned into a smelly one on runway 20 at Brussels. Our speed control had us catching a heavy ahead (between 4.5-5 miles on TCAS also backed up by his ATC DME request). The wind strength precluded any other runway for takeoff or landing. With the traffic density at the time we had difficulty getting a word in edgeways so took the safer option of slowing down. We were less likely to cause grief to the following than the possible Wake encounter we could have sustained. And if you do the maths, from the 10 miles we were, our 15 knot reduction would have reduced the seperation (had it started at the min 4 miles) to 3 miles at least at the threshold. Still 1000' and still safer than the other option.
Yes, got a little bollocking for it and yes we should have tried a little harder to let ATC know.
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Old 8th Oct 2002, 10:57
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The Flap 10 speed has been increased to 170kts because of the rudder problem.

On the -700 the speed tape flap speeds are much lower and 160 is normally easily held with Flap 5.
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Old 8th Oct 2002, 11:06
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Thanks for all your replies,

The main reason being offered is stable approaches. If I wanted an aircraft to fly faster than 160 inside seven miles it would be a request, not an instruction. I wouldn't rely on it in my planning and I wouldn't position another aircraft 'tight' behind unless I had the pilot's agreement.

Is 160kts by 7d and until 4d acceptable ? If not I think we should have notice on first contact with final director.

We do appreciate the need for stabilised approaches and I'll always allow a bit more spacing if an aircraft is particulary high or fast. But surely if you are ignoring an instruction you should ask first ?

If it is all down to sesma/other company procedures is it best to handle this with an MOR, so the relevant airline department can get involved ? We might then be able to work towards a solution together.

The last couple of days the headwind component at 3000' has been very small (and generally CAVOK) but would that require an unrequested reduction to 160kts at 9/10 miles by 737,744 and 757 aircraft ? Is a speed reduction that far out done in order to stabilise the approach ?


I'd be very wary about adding a ten knot tolerance on final approach speeds. 210/220 even 230 kts shouldn't make much difference but if you are four miles behind a 757 going ten knots faster from 12 miles out you will catch up and seriously erode vortex spacing.

On the other hand, if you request 170 to four on first contact with final director we can sometimes accomodate. I'd better be careful here as many of my colleagues will not thank me if every 737 starts asking on first call, but I'd rather know that's your preference and try to help out. I should also point out I can't do it if delays are excessive or wind or viz is particulary bad.

Thanks for the replies, keep them coming
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Old 8th Oct 2002, 11:07
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Bottom line - as with all other instructions, if you can't comply, let us know and at least we can plan accordingly. If you need an extra 10 kts or to slow down a few miles early then it doesn't take a great deal of effort to gain/lose a bit with the following. If, however, you just do it and don't say, then it's back to vertigo's original post and someone will have to go around/otherwise take the delay - more work for at least two of us.
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Old 8th Oct 2002, 11:17
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lost soul,

and while we are on this subject-- I understand there is a 10knot tolerance on all speed requests?? I have brought this up before but will do again-- does it cause a problem if we 737 drivers use 170 instead of 160 to 4D?? This enables us to keep the gear UP and thus reduce noise and fuel consumption! We will still need to start slowing at about 6.5 miles or 2000 amsl to meet (our) requirement for stabilized flight by 1000amsl.
There's no 10 knot leeway, at least not in the UK as far as I'm aware.

The reference to speed control at heathrow for example can be found in the UK AIP at EGLL AD 2.22 para 6)b).

It essentially says fly allocated speeds as accurately as possible and please tell ATC (asap) if you want to do something different.

At EGLL we use 2.5nm separation on final regularly and also the bare minimum vortex separation. Not flying the allocated speeds accurately will result in either a loss of radar separation or a loss of vortex separation. One is inconvenient for me, the other could be even more so for you.

But the point is, we can accomodate requests to fly at different speeds (although standardised speed control is required to maximise capacity) to what we'd normally request, we just like to be kept in the loop.

Old 8th Oct 2002, 11:30
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This 160 to 4 seems to have crept in only over the last few years, who came up with the figure of 160?

Granted ATC are under pressure to maximise the number of movements, however most sensible airlines do have a policy of being stabilized by 1000agl, this is obviously pushing it with most modern aircraft.

So, as spacing/timing is indeed important so is the safe operation of the aircraft, why not compromise and reduce this figure to say 150 to 4?

Sorry, but ATC is here for pilots not the other way around as I see it.

It's easy to sit in the ivory tower and "demand" 160 to 4? However it can be difficult to comply and no one wants unstabalized or rushed approaches or indeed un-necessarry go-arounds, and subsequent explanations to the chief pilot!

So how about ATC and airlines getting together and coming up with a safer working speed to 4 DME?

ATC you do a very good job in increasingly difficult times, so are professional pilots.

Lets work safely together!
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Old 8th Oct 2002, 11:40
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Lots of issues here.

We are back to the argument about runway capacity at LHR. Please bear in mind that we are down to minimums on the approach; if you bust your speeds we immediatly lose separation. I have been here several times and it is becoming "policy" that the one who slows down goes around, not the traffic behind.

These days the performance on final varies considerably. Compare for instance a B757 to a B773. There could be as much as 45kts difference in the Vref. At Heathrow it is becoming more common to ask for 170kts down to 4D and provided we are asked early it is not a problem. That doesn't effect capacity: bigger gap yes but higher speed, same result.

Yes, 15kts over 10 miles would be about .75nm catchup IF the lead aircraft didn't slow inside 4D but with some type combinations 4miles separtion at 10D could be less than 2 at touchdown. A Conc. is only 30kts faster down the approach than standard but we allow twice the space, typically 6 miles, and even that can get tight.

Would 160kts to 5D be a better "standard"?

Point 4
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Old 8th Oct 2002, 12:09
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BA is obviously a culprit here.

757 - latest we can start slowing from 160 is 1500aal. So 160 to 4 never is adhered to I'm afraid. From our Flying Manual for "ATC Speed Controlled Approach":

It quotes "Typical LHR ATC app 180 to 6d, 160 to 4d" i.e. what we will be asked to do. It then says to achieve this:

@2000'aal - Gear Down, slow 160K. It says 2000'aal is 6d, but my maths says a bit over 6.5d. [No problem to slow to 160K earlier which is often requested]

It then says:
@1500'aal slow to Final App speed. It alleges this is at 4.5d, but again, my maths reckons nearer 5d.

It then points out that @4d (1300') we will be 150K or less.

We have to aim for (and if we fail to achieve - "consider a GA") App speed (may be as low as 120K), full flap, App power up at 1000'aal. In an E4 757, with Engine Anti Ice (read cloudy / rainy with TAT +10C or less) anything other than a screaming headwind, and a slow Final Speed (more speed to lose) this is all not possible, and the reduction from 160 must be earlier.

Suggest LHR and the BA ATC services man discuss what gives - the 160 to 4 rqmt, or our strict 1000' criteria. Don't blame me for that - it is a little OTT IMHO.

160 to 5 would be better - its what we actually do.

Why do we not tell ATC everytime? We've been doing it like this for a number of years... so can't see anything's changed.

Thanks for pointing it out - will make more of an effort to point out what we can and cannot achieve on the day.

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Old 8th Oct 2002, 12:27
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Tell me airtrafficers, why is it some airfields like LHR seem to be able to use speed control as a method of tactical planning, where as other airfields when queried, say they are not authorised to use speed but must use headings to achieve spacing whilst feeding the ILS? Is this some legal thing or a special rating for ATCO's.

Hacks me off that some airfields make you go around the houses wasting fuel even when you offered to slow down and go more direct and they say bog off! What do we do?
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Old 8th Oct 2002, 13:23
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My company recently posted a notice that said we are to fly the speed we are told to fly. So if we are told 160 to 4d then that is what we are to do (ie not 170 or 150). I imagine there were problems with ATC which resulted in this notice.

The thing that I find confusing is when we are told to maintain a speed like 180 knots (this happened today in fact). Then we are cleared to join the localiser, etc. No further mention of speed, how long we are to maintain 180 etc. This kind of thing happens all the time and quite frankly, if we are given a speed to maintain and then cleared for the ILS and there is no instruction to maintain until a certain point (ie outer marker or 4d), then we usually reduce speed according to SOPs. Saying "maintain 180 knots" 15 miles out is fine but when we are at 6 miles and still flying 180 generally we start getting antsy and will start slowing down unless ATC tell us first.

This does create confusion usually, and a little conversation occurs between the captain and FO about just what ATC want us to do. Usually, at times when ATC require speed control like this it is too difficult to get a word in so this is why pilots take matters into their own hands. If ATC want us to maintain until further notice, then it would really help if they told us for how long. And then try not forget about us. In the UK this is usually not so much of a problem but in Europe (read Spain) it happens all the time and if you follow ATC instructions to the letter then you will be crossing the threshold at 180 knots. We have to reduce at some safe point, and this is probably why people appear to violate the instruction, when in fact they may think they have been forgotten about (again).

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