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