LHR mixed mode proposal
 

Hello ATC gurus,

In this document:
http://www.dft.gov.uk/consultations/.../mmconcept.pdf
from http://www.dft.gov.uk/consultations/...hnicalreports/

Does the text below mean that all arrivals into 27L&R will pass over central London? (Currently at non-peak times they can join closer to the airport?) Minimum "length of final" looks like 20nm (from section 4.3.5), is that right?

many thanks,
Farjer.

I have to ask any Heathrow controller, will it work anyway? Surely movement rate will decrease due to the need for wider spacing between arrivals to ensure departures can get away, and then only subject to runway occupancy by landing traffic.

Movement rates do increase. Think of having two peak hour Gatwick type operations running for umpteen hours a day. That will, in theory, allow for more movements than in segregated mode.

Farjer, you need to try and attract the attention of 120.4...

He'll regret it if he does...:}

P7

I wrote an article on Heathrow Parallel Landing Trials in a magazine dated December 1965. It wouldn't work then, when the movement rate was half what it is now, so why should it be any different now?

Without wanting to ramp up the angst.

Why can't Heathrow be like other modern airport and land on parallels?

I understand why you have gone the way you have; but with modern surveillance, PRMs etc. why can't you have independent approaches when the WX is good or the technology is available or dependant approaches when the WX isn't good or the technology isn't available?

At least three reasons in the 60s:

1. Noise abatement - the locals like a break from the noise and the noise lobby is unbelievably powerful.
2. Traffic rarely offered equally from/to both north and south, resulting in frequent ground control and radar problems.
3. Heathrow is a very small airport and ground control with both runways being used for landing and take-off proved extremely difficult.

There are probably other reasons too.. Have you seen how quickly weather changes in the UK?? It would be almost impossible to run a sequence based on good weather more than 2-3 days a year!

One problem with the existing layout is the lack of suitable high speed turnoff points from 09R. I presume that would be addressed at some point (although why if wasn't during all the taxiway works surprised me).

Mornin' all... somebody call?

To answer the initial question: The longer turn-on to finals must become the norm for reasons I will try to explain. Please bear with me.

1. In mixed-mode the traffic must turn on vertically separated. (The TWASS concept mentioned in the Consultation document in whcih vertical separation is not maintained is a fail dangerous operation and there is ample evidence to prove that it is only a theoretically possible concept. It is not ICAO and the regulator is unlikely to be happy with it. I would refuse to actually do it.)

2. Understandably, the government wants as much CDA as possible and this means that the joining altitudes have to be as high as possible but for every 1000' up you put them you have to go an extra 3nm out. The current TMA design would only permit joining at 4000' and 5000'. Future changes to use 6000' and 7000' (and thereby provide full CDA are in the pipeline, and they have to happen for Runway 3 anyway.)

3. Problem. Traffic is only deemded separated when BOTH sides are established on the Loc. To be absolutely independent and therefore fully efficient, traffic must be able to descend regardless of the other side. Imagine a case where the high-side is on the Loc, approaching the glide but the low-side is not yet established. The high-side would not be able to descend and may require repositioning. The two Final Directors would spend too much time talking to each other instead of vectoring the traffic.

4. Solution. Have the traffic join at a MINIMUM range that is equal to the high-side glide path plus 3nm. In this case that means 15nm (5000' @3 degrees) plus 3 equals 18nm as an absolute minimum. Then, the low-side will always establish 3nm outside the range of the high-side glide path and therefore the high side will always be able to descend. Simulator trials demonstrated that in fact you need plus 5nm to allow for joining errors. 15 +5 =20nm, minimum.

Does that help?

.4 :)

Thanks 120.4, I understand perfectly and will try to paraphrase in layman speak, just to be sure...

Two planes are only allowed to be within the vertical separation if locked on to the ILS. Joining the ILS is subject to wind/weather/pilot/plane variability. Therefore you need to make sure all maneuvering is done just before joining the ILS, at the same place but at a safe vertical separation.

Wow........
 

Seems awfully complex.

Are you getting/do you have PRM (parallel runway monitoring) positions or equipment?

What is the spacing between the strips?

Can't you descend in VMC regardless of what's on the other runway?

We join ours a vertical levels too. But we join with all 'domestics' independently in VMC; i.e. they get a traffic statement and thus are responsible for not going through the centreline due to traffic on the other side. It's fun watching two domestics pointing at each other; they have traffic of course on/before base.

Directors rarely talk to each other, it's look and go stuff.

Yes, that's correct - and because the joining altitudes are likely to initially be 4000' and 5000' that forces the Loc join out to about 20nm (making the base leg about 22!).

.4

Hi Pirate, just missed your post.

The Heathrow strips are about 1400m apart meaning that as our primary radar update rate is less than 5 seconds we don't need PRM. We would however need monitoring controllers for ICAO standard Independent parallel ops. and at Heathrow that will be a challenge. They are running about 20% understaffed now, adding an extra FIN and two monitoring controllers (3 total) needs 4 ATCOs per watch! That's 20 extra staff or an increase of 50% at a unit where the failure rate is high. May have to get creative - such as "Monitoring Only" validations etc.

We can do VISUALLY separated parallels (not approaches maintaining VMC)now but the nature of the Heathrow operation almost makes it pointless. If we land on the departure runway it is usally at a rate of 6 per hour. We always choose to put the extra aircraft in a vortex gap in the traffic on the landing runway. As that gap must always remain - there is no point in going absolutely parallel, you might as well go 2.5 and 2.5.

.4

So where are the job adds? Will you take experienced people; improve your failure rate, mind you monitoring only sounds like a great gig :} It would suit my lifestyle too I'm sure; i.e. no night shifts for that role huh?

I believe the failure rate amongst experienced ATCOs may be worse than ab initios - but I stand to be corrected on that.

There used to be a permanent internal trawl notice out in NATS for Heathrow approach people. Don't know if it still there.

.4

SM4 Pirate.. I was a Heathrow controller for 31 years and I do not believe the place was ever fully staffed in all that time. It's a way of life here...

.4

What is the difference between a PRM and having a monitoring controller? Is it effectively the same thing from the pilot's point of view, but without requiring the extra radar kit?

G W-H

Sorry - I've been out of the loop for a long time. What's a PRM position if it isn't a controller?

Recently been informed that if I am given an approach to 27L when it is also the departing runway, due the position if the G/S aerial - I now have to do a LLZ Approach.

Will that restriction be inforce for mixed mode? That would not bode well for mixed mode...::hmm:


T'bug :ok:

Morning

Moitoring controllers (not the FINs) are required for all Independent parallel approach operations, i.e. where traffic may become side by side. (As opposed to Dependent Parallel approaches, where they don't).

Where the runway spacing is less than 1310m but not less than 1035m,

"...suitable SSR equiment, with a minimum accuracy of 0.06 degrees (one sigma), an update period of 2.5 seconds or less and a high resolution display providing position prediction and deviation alert..." must be available.

That is PRM.

So, you must always have monitoring controllers, and must also provide a PRM if the spacing between the centrelines is less than 1310m.

.4

Hi Bug

Just missed your post.

No, you're right - that won't work for Mixed-mode. This was an area we gave close attention during the Concept of Operations development. There are a number of solutions including altering taxiways to get around the GP critical area on 27L. It is possible all traffic from the south would have to cross at the old Block 85.

.4

"It is possible all traffic from the south would have to cross at the old Block 85."

That should bring GMC to a complete standstill then!

SM

Probably not as bad as all that ref bock 85. T4 will be a lot quieter. I'm sure Gonzo will have some figures.

34-28-34.









Oh, ok then. 4% of traffic, as opposed to 22% now.

Maybe.:E

OK, 4% of our traffic will be in T4 as of Switch 1 (end March 2008), but once T4 is modified for multiple airline use (and some of the "Open Skies" boys will be starting their services in T4) its usage will start to grow, presumably back near to current levels.
Ground movements at Heathrow only just work at the best of times. Increasing the landing rate (two Gatwicks side by side) and moving inbounds and outbounds to/from two runways will very likely cause gridlock.
IIRC, the largest airport in the world (KKIA, Riyadh) is 50 sq miles, Denver is 35 sq miles. Heathrow, the "Busiest International Airport in the World", is 4.5 sq miles.
A bit before my time, but I am sure HD was correct in 1965, and it will cause big problems on the ground if it is tried in 2008.
SM

It won't be happening in 2008! It will take about 4 years for the technical work, airspace change process, etc.etc. but staffing could take longer than that. My guess is we are unlikely to see full mixed-mode before about 2013.

.4

I heard a rumour of two years depending on the type of mixed mode they go for. So not before 2009/2010?

Can I get a ticket to watch GMC? It should be hysterical! I don't think that those who formulate such schemes spend much time at the sharp end. As has been mentioned, Heathrow is a tiny place and traffic and concrete are infinitely more complex than when I wrote the article in the 60s.

Just to correct ... independent visual approaches do not require a traffic statement. It is pilot responsibility during IVAs not to pass through final. How many appreciate that fine point is a whole other discussion. Pointing two domestics at each other takes a lot of getting used to. And with most operators leaving TCAS on these days, there are RAs on final from time to time. More often that not the RA traffic can resume approach once clear of conflict (ie, established on centreline - just a little above or below the glide). International traffic conducting IVAs don't get traffic statements either ... they are separated by other means (vert/3NM) until established on centreline.

Surely mixed mode ops will provide a higher overall movement rate for Heathrow? What about all the wasted runway occupancy with wake turb on departures?

And a question about non-PRM 'monitoring' controller ... is this in addition to DIR? DIR is the only requirement for IVAs and PRM ... max 52 (?) mile radar range.

Just read the document linked in at the start of this thread which answers my monitor question above. Staffing this position doesn't need to be by director endorsed controllers. It could be by ab initio, tower, area, departures, etc. Quick training, 100% pass rate.

Geffen.

The full original Concept of Operations is in my view the only practical option. I know, I would say that wouldn't I. The fact is I studied the options for 2 years and the quick solution (TWASS) is not practicable on safety grounds.

TWASS is not an option because... The current final director works his but off doing 44 per hour and the slightest distraction can lead to difficulties. There is ample evidence to suggest that, in fact, we need to take work load off him because the incident rate through ATC error is unacceptable. Picture this then, that instead of taking workload away from him, we add 10-15% and introduce more complexity too. That is what TWASS means, and it also means traffic turning in towards each other without a vertical safeguard on a frequency that is saturated and with a high number of foreign aircrew.

I wouldn't like to say it is impossible - that would be tempting fate but I think the only way the full ConOps could be delivered in two years would be if the Government intervened in the normal process of airspace change etc. NATS has quoted 4 years because on average that is the time it takes to complete an Airspace change (involving SIDS etc,) on the scale necessary.

I am also sure that using departure radar would enable some enhancement of departure capacity, which would then enable TEAM (6 arrivals per hour on the departure runway) to be used on a permanent basis without getting the airport out of balance. It is possible that this could be introduced in a relatively short period but that is not full mixed-mode and wouldn't deliver anything like the capacity - maybe 90 an hour with the right mix. Well, we sometimes do more than that now. It would make us a little more robust in strong winds though.

.4

I am very disappointed indeed to read that the use of simultaneous approaches into Heathrow with a monitoring controller is being considered.

I will be perfectly honest and admit that I have never done a PRM approach (effectively the same thing from a flight crew perspective) for real, though I have had the mandatory simulator and CBT training, as the fleet I fly on has diversion aerodromes that use the procedure.

Having read, watched and "flown" various breakout manoeuvres, I find it simply baffling that any regulator could approve such a scheme. For anyone reading this who is not familiar with the technique, it involves aircraft flying parallel (or in the case of SOIA, converging) approaches under IFR, whilst using both radios. One radio is tuned to the normal ATC frequency, the other is used to listen to a "monitoring controller". In the event that an aircraft on one approach "blunders" (FAA word, not mine!) towards towards the aircraft on the parallel approach, the monitoring conroller issues a "breakout manoeuvre" on this special frequency.

In effect a pilot is one minute flying a nice, stable ILS approach when suddenly he is faced with an awful lot of conflicting signals: the ILS beam bar/GP indicator/flight director says fly one way, the monitoring controller says fly another way, the TCAS may be warning "traffic" or providing an RA, the autopilot disconnect wailer will be sounding and the autothrottle disconnect beeper may be sounding.

Even now I can imagine people reaching for their keyboards wanting to type about how "if I really was a professional pilot I would be able to cope" and I "would know how to silence various distracting warnings quickly" and "hasn't the standard of airmanship declined since the introduction of the glass cockpit". However, I believe they would be missing the point. The point is, we should be designing safety in to aviation, not devising procedures which require a backstop as flimsy as the monitoring controller.

I used to regard UK ATC as the best in world, but I have to say that recently I am struggling to defend some of the procedures. Heathrow, once a model for how to operate an airfield from an ATC perspective, is becoming indefensible. The ridiculousness of a DCL system which requires the same information to be transmitted by voice and the use of a LLZ only approach during TEAM when the ILS could be made available are but 2 examples of how the ATC procedures are frankly lacking.

To return to the discussion on approaches using a monitoring controller: SAFE? Not inherently or there would be no need for the monitoring controller. ORDERLY? Not if every operator is required to train every flight crew on another difference from every other airport in Europe and including a breakout which is anything but orderly. EXPEDITIOUS? It had better be. I'd hate to think you were planning to further reduce safety margins for no benefit.

G W-H

GWH, I think we've covered the DCL before, so I won't go there, but are you aware the limitations that protecting the 27L GP has on the departure rate and GMC complexity when 27L TEAMing? We have to protect it out to 15 miles, so really we can't have anyone going past SB1 when an inbound is 20 or more miles from touchdown. With 6 an hour, that doesn't give us a lot of time to get anyone away from the south side.

And believe me, we hate it as much as you!

120.4,
I certainly would rather see mixed mode with all the bells and whistles, opposed to something cobbled together. How much pressure is going to be piled on NATS from the airlines and central government IF it gets approved? Hopefully the most robust system will be the one selected.
Gonzo,
Can't believe you haven't mentioned ground yet! :)
G-W-H,
One statement says it all. Commercial pressure. Money should be spent to shift the G/P and touchdown point so that we can line up, OR, HAL should build a new runway entrance.

Biting my tongue old chap!:}

Gonzo

I know how awkward TEAMing can be for you, but there are better solutions than the LLZ only approach. One solution would be for Radar could clear the inbounds to 27L to 2000' then to follow the glide. You would only have to provide GP protection from 6dme then. Surely the added safety benefits would make this worthwhile?

If that solution doesn't float your boat, how about specifying no autocoupled approaches to 27L? I seem to remeber flying somewhere in Europe recently where this was being promulgated on the ATIS. I'd rather hand fly an ILS approach which is not too different from the one we have briefed for the arrival runway, than have to rebrief as we leave the hold for a npa for a landing on the departure runway.

If there is a bit of spare cash floating around, how aboat a fillet of concrete at S3 to allow traffic to make a right turn here for departure or crossing, and use this as the position for departures from the southside?

Returning to potential problems with the use of a monitoring controller. The system is currently used in the USA, but over there the controllers do not tend to use such tight arrival spacing. In my experience it would be rare to have 3 aircraft on approach within 5/6 miles (unless they are doing visual approaches). So, imagine a day when the inbounds from the north outnumber those from the south. 2.5dme spacing is used and a run of 3 aircraft are packed at 160kts on 27R. Meanwhile on 27L there are few arrivals, and the (about to become) villain of the piece is slowing (slowly) from 210kts to 160kts. If this aircraft blunders towards the north, 2 or perhaps extremely 3 aircraft may need to fly a breakout. I do not believe that when the system was devised multiple breakouts were envisaged. To remove this possiblity, the minimum spacing on final would have to be increased to 5/6 miles, in which case we may as well continue to operate dependant approaches.

Having said all that, the incredibly poor quality of transmissions from all TC sectors at the moment makes the whole system impossible. The levels of distortion are too great to guarantee safety for something as safety critical as the use of a monitoring controller.

All in my humble opinion of course.

G W-H

From a purely tower point of view, to us a LLZ/DME, or a platform height of 2000ft would be great.

Unfortunately, this increases workload for Director, and also means some of the 'deemed separations' below the GS over London wouldn't be available.

Not sure the regulator would go for this at all. There was enough hassle from them with us doing LLZ/DME approaches to a runway where full GP was available. I've also been told by crews that if there is an a/c moving in front of the GP on 27L, it can show up as a full 'fly down' indication.
BAA having spare cash to spend on airport infrastructure?:}

When BA moved into T4, I believe a condition was that all departures would be able to depart from S3. When we have had WIP that precluded a full length departure from SB1, lots and lots said that they needed full length.

I'm sure I don't need to tell you also that with the number of flights out of T4 at the moment, it would completely screw GMC2 (121.7) up if S3 was the departure holding point. One a/c waiting there and the whole south side would very quickly come to a grinding halt.

According to the AIP (chart AD 2-EGLL-8-10) the LLZ/DME procedure starts from 2500'. Since this is the case, you guys in the Tower would only have to guard the glidepath from 7.5dme if we used 2500' as the platform altitude for the 27L ILS when TEAMing. This won't cause a problem with deemed separations as clearly 2500' is OK for the LLZ/DME so it must be OK for the ILS.

As to adding workload to FIN. I wouldn't like to comment on whether it was better to increase the workload of someone who has spent the night in his own bed or taken a long sleep in the bunk room/vacant office, or whether it would be better to give more work to 2 guys who are arriving after spending a night out of bed, coming from a timezone 6 hours away, perhaps snatching an hour of sleep in the seat, then staring at the rising sun for 3 hours. (More seriously, the GS could act as coordinator to keep FIN's workload manageable).

G W-H

There are some issues in that. I have to dash right now but I'll get back to you.

.4

<<whether it would be better to give more work to 2 guys who are arriving after spending a night out of bed, coming from a timezone 6 hours away, perhaps snatching an hour of sleep in the seat, then staring at the rising sun for 3 hours. >>

Dear Lord... I've bitten my tongue on thousands of occasions through loyalty to my pilot friends but I now have to say it - if I hear ONE more thing about pilots' workloads I'm going to be very seriously sick.

<<(More seriously, the GS could act as coordinator to keep FIN's workload manageable).>>

Written by someone with little knoiwledge of how the system works. For one thing, the GS may not have a validation for the sector. How would you like an unqualified person leaning over your shoulder telling you how to fly your aeroplane? And just how could a second person make the Final Director's workload manageable without getting in his way?