LHR CAT II/III holding points a question

[Sean Dell]

As a regular LHR operator, I wonder if someone might answer a question form me.

Why is it that on a non LVP day, a/c are instructed to hold short of the active at the CAT II/III holding points (particularly N1, and S3) despite the wig wags being illuminated at the CAT I holding points. This to me has runway occupancy implications and also can lead to some close calls (ie Go Arounds) from slow to cross a/c (or under Tow) who start from further back.

Probably a good answer out there - I just can't think of it though.

Cheers

SD

[Gonzo]

SRG guideline, supposedly to give us more time to spot a runway incursion.

[Sean Dell]

Cheers Gonzo

Never saw this promulgated (probably missed it!)

[Gonzo]

Neither have we, to my knowledge!

I think we consider it 'best pratcie'.

[discountinvestigator]

The definition of a holding point is only to protect the aircraft on approach from obstacles. This is then modified for navigation signal accuracy reasons to give us the CAT II and III locations.

The holding positions do not provide any level of runway incursion protection. Do the maths for a 75 metre visual departure holding position, with a 32.22 metre semi-span on centreline and taxi up to that at 15 knots (say 7 or 8 metres per second) and then you will find that the RIMCAS does not have time to detect and trigger long enough before impact.

The best practice is to ensure that the aircraft on the taxiway system is stopped prior to the clearance to use the runway by a departure or landing. I hear howls of "capacity". In fact, the appropriate procedure is to have a second hold a significant distance from the runway and if the taxiing aircraft busts this hold, then action can be taken for the aircraft on the runway or on approach to it, as well as for the offending aircraft on the ground.

Is it in Annex 11 and 14. No. Is it in CAP 168 and Mats 1? No. But your local runway safety teams doing their risk assessments, putting it through the SMS for the airport operator and ATC service provider will obviously come to this conclusion.

By moving the runway crossing hold to the CAT II/III location, it does provide some more time for RIMCAS et al to spot something. Is it time enough? Well, it depends on the crossing angle and the relative energy point on the runway, but usually no.

If you need to know more, PM me. I am too busy with 3 runway overrun write offs to monitor the forum routinely at the moment.

[HEATHROW DIRECTOR]

Does the SMR not suffice to provide runway protection? When I was there it was usually only switched on in poor weather... but I kept my beady eye on it like watching a rear-view mirror in a car.

[discountinvestigator]

Ah, the old one of when to switch it on. Incursions happen at night, in good visibility for some reasons. They happen at night in the rain for others. They happen in the day in high visibility for other reasons and the same in low visibility.

If you break the hold line and continue onto an active runway, then the probability of recovery from ATC is relatively low in the event of impact geometry being present. No reflection on ATCOs, merely design of the job, allocation of tasks, etc

It would probably not be realistic for most modern airports to argue that basic items such as H24 stopbar use, SMR and RIMCAS were not "reasonably practicable". Therefore, you end up in a problem. There should be standing instructions issued by the airport operator that the SMR is to be switched on H24 at the busier airports. For it not to be installed and switched on would require a risk assessment to show that it was not required.

In the same way, not using "appropriate" locations for holding positions would not be a good legal place to go. This would mean scrapping visual and CAT I holds in most places. If you do the capacity calculations, it is not usually the critical path item on departure only or mixed mode for most runway layouts. For runway crossings, it does add some time, but these are some of the higher risk operations, when recovery time might be what you need in the first place. Alternatively, stop the aircraft operator from moving half its T1 operations to T4 in the first place...

So, I would dare to suggest, in the absence of any published risk optimisation criteria in order to comply with "As Low As Reasonably Practicable" (which is a huge failure of SMS anyway), then you should keep SMR on H24.

Remember, half of the runway incursion alert systems need appropriate ATC procedures and airport infrastructure to work effectively! Milan Linate would have triggered at least three independent warnings on an appropriate RIMCAS. Lexington KY (Comair 5191 CRJ) would have generated a warning for using the runway as a taxiway (area alarm) and also a using the wrong runway warning (acceleration/speed based alarm), so two in that case.

Your SMS integration between ATC and airport should be quite clear as to which organisation is the leader (in the UK, it will be the airport operator) and therefore, you should reflect the operational demands of the Aerodrome Manual. IF there are no rules in the Aerodrome Manual, then it is about time to get some.

[HEATHROW DIRECTOR]

No disrepect intended, discount investigator, but all that is as clear to me as mud! How on earth did we manage for the 50 years up to the time all this gobledegook started? There has to be something more fundamental - are the controllers communicating precise instructions and are pilots obeying them? I don't know what RIMCAS is but assume it's some device for preventing incursions (if so, does it work with vehicles). SMR does a pretty fine job when it's switched on and used properly so what's the benefit? I never had a runway incursion myself during 21 years at Heathrow Tower and the only one or two I saw were caused by pilots or vehicles failing to obey explicit instructions. If a pilot is not going to follow instructions, or if those instructions are ambiguous then nothing short of a mechanical stop-barrier is going to prevent someone entering a runway when they shouldn't.... but ATC should be sufficiently on the ball to stop it when it happens.

[GT3]

One viewpoint here,

If we instruct you to hold at the CATIII holding point and you pass it by mistake there is time to stop (either pilot or ATC initiated). If you are instructed to hold at the CATI bar and you miss that then you instantly have a runway incursion.

[Spitoon]

...........then nothing short of a mechanical stop-barrier is going to prevent someone entering a runway when they shouldn't....Oh, don't go putting ideas into his head!!!

[Gonzo]

One has always thought there should be either the one-way barriers one finds at the exit to car parks at each ruwnay stop bar, so aircraft can vacate easily enough, but aircraft have to wait for the barrier to drop before entering the runway.

Of course, if this doesn't work, then there's always the 'Stinger' approach (and I don't mean SAMs!)

Discount Investigator, sorry, I'm not quite sure what you're trying to say. I'm only an ATCO! :}

Other info:
-ASMGCS is on 24hrs. We have procedures for identification and validation of traffic requiring its use.
-RIMCAS (runway incursion alert) is currently unserviceable.
-When serviceable, it only detects within the actual runway, with the exception of N4E and N4W. It does not detect out to CAT I holds, let alone CAT II/III holds. Therefore, in no way, apart from the aforementioned holding points, does RIMCAS prevent runway incursions. It will alert us when they do happen.

[Point Seven]

Gonzo

When RIMCAS is returned to service, it will have a new functionality to make detections outside of the designated "Runway Area".

It is also worth pointing out that that, as this is a public forum, it is NOT unserviceable but had a false alert rate that was unacceptably high. This leads to ATCOs having no confidence in its alerts (quite rightly) so the system was taken out of service to improve this. It is due to return to service very shortly.

P7

[Gonzo]

Quite correct, P7, and I should have said 'Out of service'.

Good to hear that the new RIMCAS will have more functionality, and I am aware of course there will be procedures for this.

Hopefully this will be another 'Heathrow in decent kit shock!' :ok:

[Point Seven]

Don't you mean "only the second LL in decent kit shocker"?:E

P7

[Yellow Snow]

GT3If you are instructed to hold at the CATI bar and you miss that then you instantly have a runway incursion

Just to play devils advocate here! to literally turn your statement around, we, at LHR ATC routinely give landing/takeoff clearances with landing/crossing aircraft straddling CATI bars, yet this isn't a runway incursion?

We need to ask ourselves would you happily give a 27L inbound a landing clearance with a T4 crosser over the CATI bar, assuming good vis' we've always got the arguement of 'oh, it's a visual runway, so it's OK' :eek: That's until one of us has an incident and the, up until this point, toothless SRG comes down hard, even when they know we do this now but turn a blind eye.:*

Discuss.

[Gonzo]

P7, you are quite correct again! :ok:

Is this a new habit?

[TheOddOne]

Well, down in the Sussex countryside we use the CAT I holds all the time, unless we're in LVPs. These are now placed at 90 metres from the runway centreline, as per CAP 168 (Chapter 3, Aerodrome Physical Characteristics. 7.7.1 and Table 3.3) Our CATIII holds are of course on the Reiffer line, 137 metres from the runway Centreline. Our RIMCAS seems to work pretty good, too. We have to be sharp about where we vacate to during on/off runway inspections, for instance. As far as I know, our RIMCAS alarms whenever 2 targets present a relative closing speed in excess of 40 kt.

A/c are required to hold accurately at the CAT I hold at Mike 1 to ensure proper separation for other a/c manoeuvring to/from the south side of Pier 1. Base pilots are very good at this but I did overhear one visiting crew recently being mildly admonished for holding at the CAT III and being asked to move up to make room behind.

We're proud of our continuous improvement in our runway incursion record; all as a result of a lot of hard work by NATS, Gatwick Airport and the pilot community. Oh yes, and the Gatwick 'can do - positive attitude' magic touch.

Cheers,
TheOddOne

[Yellow Snow]

I honestly think at LL it's either lazyness or a lack of appreciation.

It definately isn't because of what SRG recommend otherwise ops would've published something to that affect! ;) Just like LOC/DME approaches:rolleyes:

When the new taxiway system came in a couple of years ago the CAT 2/3 were named with a simple letter and number eg S3, the CAT1's were labelled with two letters and a number eg SB3. They should've been done the other way around! When you have to say it 45 times an hour the extra word adds up. That or you could ask some LL ATCOs what the CAT1 hold on November taxiway is called and I'd say 30% wouldn't even know there was a NB1.

Shall we get started on the ridiculously named runway holding points, ETTIV and OSTER are a complete joke. If we are on Easterlies most foreign crews don't bother to hold either OSTER or HORKA:ugh:

[GT3]

YS - yes I agree that clearances are given when a/c are straddling holding points. In relation to the "hold short of A" conversation we had the other day it is yet another Heathrow way of doing things.

[discountinvestigator]

Hi,

The unacceptable false alarm rate of the RIMCAS might have something to do with the lack of procedures for using it etc, or it might be because the surveillance systems were giving false returns. I do not know which.

As I remember the debates about OFZs, CAT I holds etc, then a degree of common sense has to be used. I did a risk assessment at LL some years ago which showed that if the controller gave an anticipated landing clearance (in that the tail of the first aircraft was expected to be outside the Obstacle Free Zone and the CAT I hold slope) and it stopped well off the runway but inside the zones, then the risk was reasonable. However, it would take an examination of the NATS and BAA risk criteria to determine if it was acceptable in the new corporate regime. It is actually up to BAA to determine, and for NATS to follow. Alternatively, if BAA say yes, then NATS can always refuse based on different risk criteria.

Are SRG likely to come down hard? Is not the main advisor in the legal section the former SRG head of ATS investigations? Would there be a conflict of interest in his actions....

Please remember that the CAT I hold line is for aircraft coming up to the line, not crossing over it to vacate the runway. The cockpit elevation can be different from the tail!

The controller could be considered to have violated the rules as an individual if they do not adhere to the basics. However, your main defence would be that everybody is doing it, the management know about it, your contracting organisation (BAA) know it is going on, and none of the management have done anything about it.

If an individual ATCO was to be prosecuted, then using an appropriate barrister (well know at getting train drivers off Red Light running) who is aviation law qualified, should see the case thrown out fairly quickly.

It is still much easier to get rid of all the CAT I and visual holds and just go for the CAT III, unless your safety calculations show otherwise!