Min clean. Height constraits LHR arrivals.
 

Had a new scenario on arrival this afternoon into LHR. I was held high, and asked to come back to min clean at FL390. 747-400. I was then given descent and the restriction, FL150 by Tiger. Now here is the box that LATCC put me in. As I was high on the profile, I ... needed to lose height quickly, but had the constraint, "Min Clean". Speedbrake, I hear you say. But that is not option. Not an option because as soon as they are deployed the low speed buffet margin increases above your indicated airspeed. So no way of meeting the constraint, given the constraints presented to me.

I bring this to the attention of your good selves, as the new variable speeds into LHR become more common, and if we are held up, then getting down at "min clean" is not very easy unless we can accelerate, then get the speedbrakes out.

Min clean, and expeditious descent are incompatible.

Hi
I think it was me you were talking to! I was controlling the Lyd sector at the time and Terminal Control ran out of levels at Biggin without giving us much notice and we had quite a few Heathrow inbounds which we needed to slow down as quickly as possible to avoid any en-route holding.
If I remember correctly, I was unable to give you initial descent as there were several other high level aircraft just below you which I needed to vector out of your way first, and yes, this ended up with you being high.
At the time the RT was very busy and while I obviously wanted you to make the level and slow down as best as you could, I didnt have the time to fully explain myself (make the level then reduce speed etc). Having said that I didnt realise that deploying the speed brakes means your minimum speed increases so much.
Thanks for posting, I definitely learnt something today! Feel free to PM me if you have anything else to add!!

bmb7jiw

L337, like my colleague says we had alot of short notice this afternoon for holding out, not the TMA's fault, weather was causing a few problems and holding for LHR was around the 25 min plus mark for nearly all the afternoon which isn't that usual anymore for such long sustained periods. Added to this, bunching from the French was higher than usual and it just made a difficult afternoon. We need min clean as early as possible as holding at TIGER isn't that common and can cause knock on effects and high workloads which we naturally try to avoid. Unfortunately our French colleagues won't agree to transferring LHR traffic at a set lower level all the time so we have to accept you at whatever level you are cruising at unless other traffic dictates a level change is necessary.

In the situation you had, I would always say plan on the level restrictions on the STAR chart. They aren't just to get you down, they ensure separation against other routes and other sectors RELY on you being level by a certain point. If a speed restriction means you cannot make a level restriction then let us know ASAP. We can only guess you MAY make them, only you know the exacts. It is quite surprising at how different a/c can perform on the same route, all get the same instructions but the results can be very varied. We know low speed means low descent rates (we teach with the phrase "you can't slow down and go down" often), but we can issue some instructions that are met without any seen problem so can only try with all a/c types assuming any non-able to comply is told to us. Basically its one of those situations we really need you to work well with us as, even if the RTF doesn't sound it, a lot more hard work and planning is going on making sure all flights are still soundly safe.

Maybe its yet another call to get ATCO's back in the cockpit more so we can broaden our knowledge, I wouldn't mind seeing what Mauritius looks like this time of year when the rain is tumbling down on the centre...... :}

Superb! The system works. PPRuNe at it's best. Many thanks for that feed back.

I was very aware that life for you all on the ground was very buisy, and seemed to me at the time, very fluid. The French addition is very interesting. (As was the AF that decided to leave the hold unannounced). I tried a couple of times to communicate ASAP my conundrum. I think I managed to block a few transmissions on the way. But it all got sorted, and no one seemed to get frightened.

We were handed over to you at FL 400. Above the optimum level, but Reimes pushed us up. Min clean at that level is sporting, but OK for a while. If you then need the speedbrakes, as you know, they are effectively barn doors on the wing. So the stall speed goes up. If you are back at min clean, then the stall speed at that level rushes up to meet you. The 747 has a very swept, old school wing. Absolutely superb at M.86. But get the speed back, get behind the drag curve, and it is not a happy aeroplane. Min clean yesterday, below FL200, with a full load, and "normal" fuel load was 235kts. That is fast.

Here is a picture of what I see in "coffin corner". I show it so you can see the speed tape.
C-Corner

In this picture the onset of low speed buffet is 258kts. (Top of the bottom yellow tape). So if now pull the speedbrakes out, that yellow "hockey stick" moves up. If the speed had been at min clean, then the yellow tape would have covered my indicated speed, telling me that my speed is too low. The top of the red and black barber pole, bottom left, is the stall speed. The top of the yellow tape is the 1.3G buffet margin that the CAA ask of us. Curiously if the aeroplane had been on the USA register, It would have a 1.2G margin, and have more room to maneuver.

Brains immeasurably greater than mine I am sure will correct me if I am wrong, but the above is roughly what happens!

Amen to that. As things get more and more congested, and we are all trying to operate as efficiently as possible, good communications can only help us all. And Mauritius is nice this time of year also. :D

Indeed useful background stuff for ATC to know, but isn't 'min clean' 'min clean'? When min clean goes up with s/b, so will your IAS? ATC have to put up with that and will probably not notice in reality. Just fly faster? Like a 'good chap' you are still complying with the request, are you not? In any case, ATC have NO IDEA what your min clean is. How many knots are you talking about? Would they really be significant? I doubt it would make any real difference.

The only real problem for a pilot would be if given an actual speed to fly, which would be unlikely at that altitude, but if given I would then have to 'unable' it to make the altitude restriction.

As a 'min clean' aside, is the LHR procedure when 747s are now asked to fly off the hold at 'min clean speed' rather than anything specific working well for you?

p.s. I assume you're holding at min clean as well, even if this is above 220kts, as the procedure would be a bit daft otherwise.

So what's the point of having 220kts published as a maximum in the hold?
In strong winds like yesterday who is ensuring the separation between holding traffic at 230Kts+?

Dunno, but it's a bit daft if it involves min clean plus to the hold, flaps out whilst holding and then flaps back in for the first part of the intermediate approach.

220kts to 230kts isn't going to be an issue in the hold anyway and I'd have thought the FMS could be tweaked to adjust turns and timings if required. Anyone that asks if they can hold above 220kts always gets an affirm in my experience anyway.

I thought an OPNOT had come out for KK and LL telling us to reduce 744s to min clean rather than 220kts....although that may not have applied to holding, so i stand to be corrected.

mr.777, you're right the opnot applies to aircraft leaving the holding fix.

Roffa, you're right, if they ask they always get it though hopefully with extra monitoring and sometimes with a request to "remain within the confines of the published holding pattern". However if they all start holding above 220kts (L337's example was 235kts) I don't think it'll be long till we lose separation between one at BIG and one at LAM.
I'd rather the safety case was made to SRG and the published speed limit changed (or it's not safe and 220kts should be reinforced with the operator.) This new procedure feels like we're turning a blind eye to routine rule breaking and hoping for the best.

I suspect whoever wrote the OPNOT hasn't thought this completely through...

If it's really that desperate you can always run the first stage of flap (well it's the slat that does the work really) and that will solve the speed problem and allow use of spoilers and then run them back in when you are done, that said I would just tell the controller we are unable to meet the speed AND the height let him or her decide which they want.

Interesting thread indeed.

Just caught my attention ... with no offence - "remain within the confines of the published holding pattern" - would you really say that? I am quite confident about my English, using it daily, but I haven't heard this word before. Not that you wouldn't figure out but generally I'd say using simple English is essential. It must be hard for you, I know, but it has not been once when I heard my pilot friends complaining about understanding the British ATCOs..

Sorry for OT, guys. Language aside, I only hear acclaim :)

BOAC: I agree absolutely with you, but on the day it was evident that ATC wanted us going as slow as possible. To make the constraint we needed S/B and at least 270 kts to get down. So a good 35kt increase in IAS. If ATC "probably will not notice" then indeed I was worrying unnecessarily. Tiz why I posted here. To get some idea of what was really expected of me, and to explain some of my constraints on the day.

In my experience, the extra speed required to make a level restriction in that situation would be and has been quite acceptable (uncommented anyway) to ATC, as long as you come back asap.

If I was worried about trying to maintain longitudinal separation in a stream, I would issue a speed restriction rather than min clean.

I think most of us issue min clean as a tool to reduce the rate of aircraft entering stacks/holds rather than for separation.

Quite a common problem at MAN, so I usually ask whether the controller wants the height or the speed as a priority, then act accordingly. More a/c than just the B747 suffer from this problem!

I think more f/d visits for ATC are increasingly becoming a must, especially when ATC will get to see the ridiculous constraints that are being placed (FL 310 by EXMOR [5000 blw optimum] FL200 10NM before MONTY [7000 blw optimum]). This is not a critercism just an observation!

We have since 2001 become reliant on forums such as this, where a simple visit, whether it be to Mauritius or Malaga, would benefit all!

The UK flightdeck community via BALPA are fighting hard to get flightdeck restrctions lifted, perhaps some of you controllers could get your union to join the campaign?

MANAGP,

The ATCO Union is fighting hard to get the restrictions lifted! I think I'm right in saying that ATCOs are on the DoT approved list but it is up to each company whether or not they allow flight deck visits. Also I believe there is an issue regarding that the ATCO must have a proper ticket for a seat down the back and who pays the departure tax?

We are also trying to make Fam Flights part of the Unit Training Plan for Ab Initio trainees as they would have never been in a cockpit. Unfortunately at the moment, NATS won't give Time in Lieu for Fam Flights to valid ATCO's as they have to be conducted in our time off. They can't roster them as part of our duty time as we are short staffed and (probably quite rightly) won't take the service delivery hit by putting flow on for ATCO Fam Flights.

As you can see, there are hurdles to over-come from both sides, but I think it is generally agreed by all that Fam Flights are a necessity and it is up to pilots and ATCOs to push their respective companies to set up a proper scheme. Of course, Pilots are always welcome to visit the Towers and Centres as well.

coracle

Thanks for the info, many of my workmates are almost embarressed to go on tower/centre visits because we can't easily reciprocate the open invite!