Low Visibility Procedures under CAT 1

[Ed Set]

An "interesting" situation today at my CAT1 equipped airfield.
Visibility is 7KMS but cloud now drops to OVC at 200 feet therefore Safeguarding and Low Visibility Procedures are technically required, HOWEVER one of our standby generators is U/s so safeguarding cannot be completed.
ILS/Approach Lights?Runway Lights all working normally, but obviously with the possibility of losing one electrical circuit should a failure occur.
Aerodrome Authority ask that all aircraft are advised that they must now use an alternative non precision decision height (490 feet in this case).
Bearing in mind that a CAT 1 airfield doesn't actually need safeguarding what would your action be from the Flight Deck? Do you use the non precision decision height or can Company SOPs override this in certain circumstances?
Probable that the cloud MAy be wrong of course!!
Situation resolved when it suddenly became BKN at 300 and Safeguarding was no longer required. As I understand it, one of the main reasons for introduction of CAT 1 safeguarding would seem to be runway protection from unauthorised vehicles, the good visibility would have precluded this allowing everything to be seen with no problem?

Discuss!!
Ed

[NW1]

My Co procedures state "no effect" for lack of standby power for lack of stby pwr to rwy lights. Another thought is that un-categorised ILS minima are the same as Cat I, but with an accepted reduction in % approach success....

HTH

[Data Dad]

ahhh! Mon -ami!

You mean they STILL haven't fixed that genny??

Been there done that about 2 weeks ago - (and still recovering)

It's not XXX airport authority - it's CAP 168 which says that without the backup then no precision approaches permitted (the ILS effectively becomes non-categorised). I agree with you - stupid when it's only Cat 1 to start with and it's actually the lights other services that will suffer (the ILS has it's own battery back-up) and even more stupid when it's for cloud not vis.

See ya in the mad house soon!!!

DD

[Earthmover]

My Company's procedures are the same as NW1 - and comparing location, it can't be the same Company.

However: I'm inbound to your airfield and you tell me I MUST use a higher minima - well, I ain't going to get the book out and argue the toss with you in the air- I'm going to do as I'm told.

By the way - bet this gets moved to 'Tech Log' .....!

[Sir George Cayley]

All the ground ops vehicles may be able to see 10 kms, but with the ever increasing height of contol towers in this country ( is it a willie wafting thing?) ATC may actually be IMC when it comes to 200' cloud ceiling
Sir George Cayley

[Ed Set]

The muddy situation clears somewhat-and I may now be answering my own question!!
Further investigation reveals that there is a "conflict" between those airlines operating per CAP168 and those who are more realistically now on JAR-OPS.

As Data Dad says, these lucky people must adopt a non precision minima whilst this does not apply to those operating JAR-OPs. These lucky folk can simply adopt the normal ILS minima.

You'll be delighted to know DD that as I write, the Airport Authority are replacing the miscreant generator, though it will mean a total airfield closure whilst they do it.
Hopefully this will solve the problem- at least for those involved at our far end of the universe.



Ed

[411A]

Flight deck crew really do need to remember that it is THEY who decide what minima are required, to complete the approach, and descend to....not the ATC facility.
So-called 'approach bans' excepted, of course...which, IMHO, are a complete waste of time.

Consult your respective ops procedures/ops specs for the appropriate answer, and you might well find that ATC is there to help...not impede, which may well be counter to what a very few in the ATC business might suppose.
ATC advises what equipment might be unserviceable, not what minima the respective operator is authorized to use.

[Data Dad]

From my own experience of this problem...

ATC at this (UK) airport are not telling aircrew what minima to use - The Airport Authority (who are in the UK get their licence by following what it says in CAP 168) are following THEIR rules by declaring and NOTAMing that precision approaches (ILS) are not permitted because the required ground equipment is not all serviceable for that approach (ILS when Low Visibility Procedures in force). It's a weird one I agree! And as usual (snow clearing/slot times/eobt's etc) it's us in ATC that get caught in the middle.

Not being a professional pilot I have to ask - under JAR-Ops do you have a published minima for a (normally) CAT 1 ILS that then becomes (effectively) an uncategorised one - are the approach plates still valid?

Keep on discussing

DD

[blackmail]

ils cat1

hello every one,

airport authorities announces in due time(via atc &/or notam):" ils backup power source unavail, ils uncategorised "& weather does not cooperate, e.g. 7km, 200ft ovc.
what, as pilot, do you do?
1) look up your sops:jar-ops1 manual part A chapter 8: minimas & tables with inop ground equipement. it says: no ils(cat 1/2/3) allowed with back up power source inop.
2)considering fuel options & before deciding a diversion, what can you do to stay legal, make your life more easy & try an appraoch?
question: do i have the wx minimas to start/continue the non precision approach(npa)?
answer: yes, with 7km vis you can suppose you are above min required rvr.
ceiling? ceiling is only a legal consideration at the flight planning stage for a npa(so, if your are in the briefing room, you are below minima & you need a second alternate enroute or at destination with upgraded minimas in order to depart to your destination).
but to continue our case, suppose the notam is promulgated when you are already airborne & you are informed in due time by atc or atis of the situation.
3) so you start your set up & brief + double brief(ryr pilots will understand)+monitored approach(f/o flies the approach with the autopilot/capt lands the aircraft)
technical set up e.g. for b737ng:
autopilot mode lnav & vertical speed( vnav not allowed, only 1 fms)
minimas: mda for npa.
radio aids: the ils of course, but only as an information source. we also suppose the ils front course & npa inbound course are aligned with the landing rwy.


4)conclusions: the wisdom to do all above, is at pilots discretion, because with a solid ovc at 200ft agl & npa mdh's of circa 500ft agl, there is a great possibility of a missed approach. i only tried to explain the legal/technical/practical implications for this example.
a last thing: operators define minimas according to jar ops rules & must at all times be equal or higher than state minima's.

[discountinvestigator]

Firstly, should ATC have even been considering low visibility procedures? I have been banging my head against the wall for years on this matter.

There is difference here between low cloud procedures and low visibility procedures. However, lots of MATS 2, and by default the Aerodrome Manuals do not make a difference.

The pilot operates by visibility only. By all means tell them that the cloud is low and there might be a go-around resulting. However, it means nothing to the flight deck the low cloud thing. The low cloud is meant for the foggy low visibility days as it starts with the cloud ceiling lowering. To get the safeguarding done in time, you can use lowering cloud ceiling as an indicator. There is no indication here of relatively low visibility.

When do you need runway and approach lights? The crew have their various approach light out minima etc. If it was day, then you really need a working PAPI and that is all. It is nice to have the rest working, and they were. It is just that you do not meet the nighttime reversion to standby power.

If you study the nighttime reversion for CAT I, it is a 15 second change over time. This appears to be written on the basis of what diesel generators can do, not what is required for safety. You can survive a loss of lights for about two seconds around flare time, if you have to. Therefore, 15 seconds equals potential prang. Remember Britannia and their 757 excursion?

Was the standby generator the back up power for the ILS? Is there no battery back up for the ILS? Only if there was no battery back up (UPS or whatever), then you would consider making the ILS "uncategorised". However, absolutely nothing has altered the ILS signal characteristics at this point. Nothing has changed the obstacle environment etc.

If you do the risk study, what you have done is to make the system more dangerous. This is not operating in accordance with "as low as reasonably practicable". Therefore, if you are an airport in England and Wales, beware! If you are an airport in Scotland, it is slightly different, but modern interpretation would probably apply from down South. For Norn Iron, no case law...

Overall, I would guess that the airport operator has not done their risk assessments to show that daylight operations with the generator out are acceptable. For night operations, a 15 second change over time does not actually stop the accident anyway

So, at the end of the day, this could all have been solved if you had split low cloud and low visibility procedures. As everywhere else...

[Spitoon]

discount, I don't know whether you've been banging your head against the wall but you sure are giving me a headache.

lots of MATS 2, and by default the Aerodrome Manuals do not make a difference

It is the airport authority that is responsible for developing and maintaining LVPs although ATC play a major role and will normally trigger their implementation.

The low cloud is meant for the foggy low visibility days

This is incorrect. The low cloud thing is meant to control quality of the ILS signal by ensuring that no large chunks of metal etc. sit close to the antenna when an aircraft is going to want to make a cat II/III approach. Cat II/III stopbars etc are located to achieve this. If the cloud is below 200ft and all aircraft angd ground equipment is as it should be, the pilot is going to choose to make a cat II/III approach. The think that tells him/her that all the necessary protection is in place is the phrase "LVPs in force". It is nothing directly related to fog.

The rest of your diatribe mixes safety management processes and international standard compliance and probably doesn't help this debate greatly.

Why the airport authority chose to say that a higher minima should be used is puzzling. Can anyone give the CAP 168 reference? It's an interesting question that obviously needs more investigation than I've given it now but my immediate reaction is that it would have been appropriate simply to tell the pilot that standby power (presumably for AGL) is unserviceable and ask his/her intentions.

[Max Angle]

I think his point, and one that has been made few times on this board is that MEASURED cloudbase (which is all that will ever be reported) is largely irrelevant in the process of flying an ILS whereas RVR is crucial which is why the approach ban is based on it. We have all flown ILS approaches where the cloudbase is reported as 200ft or below and LVPs are in force but you see the lights at 400-500ft. The base of the cloud is not solid and is quite variable in density, as long as the RVR is OK you can easily land from a CAT1 approach on almost all occasions when LVPs are in force which does make you wonder if the criteria for adopting them are wrong. Particularly relevant at places like LHR where the 50% reduction in flow rate causes chaos, costs airlines a small fortune every time it happens and more importantly makes me late home from work.

Interesting thread though, to be honest I had not idea that the ILS would safe guarded unless CAT2 or 3 approaches were in force and it wouldn't occur to me to ask. Despite what "blackmail" says above I can find no reference in our documentation that would prohibit a CAT1 approach without back-up power in fact our table (JAR-OPS) specifically allows it without a standby ILS or backup power for runway or approach lighting.

So, in answer to the original question, I would carry out a CAT1 approach to 200ft and argue about it later.

[Ethics Gradient]

Having been in a similar situation recently with a bust iRVR machine in cat 2 we ended up diverting. Our ops manual said we could make an approach bloke on the ground said his ops manual said we couldn't.
Burning round the hold at 3000' is not the place to get into an argument so we hung on as long as we could to see if they could fix it and then nobbed off to our alternate.
Company were fully supportive which was nice.

Despite some discrete enquires I never did get to the bottom of who's books have primacy and would probably do the same again rather that face a lengthy chat with the CAA.

[TheOddOne]

Generator backup

discount,

I'm puzzled by your assertion that diesel generators are used for backup. We certainly don't use them like that.

Our SOP is to use a ring main as its own backup. Thus, a break in the ring DURING any period of LVPs is covered by the supply coming around the other way, so to speak.

If the ring is interrupted before the onset of LVP, then it can't be used as its own backup. What we do then is to use the Diesel generators as the PRIMARY source and the mains as BACKUP. That way, we get the 1 sec changeover required for CATIII. This doesn't cost any more, just a bit of lateral thinking to give the result.

I'll also repectfully disagree with you about there being a difference between LVPs due low cloud and low horizontal surface visibility. Yes, we often get situations where we are 200' cloud ceiling but several km under it. We still need LVPs in this circumstance, so that when crews cloudbreak at 200', there is a reasonable chance that the a/c is aligned with the runway. I reckon you've got less than 15 secs between a 200' cloudbreak and the flare in a big a/c. That's supposed to be possible to hand-fly for a CATI approach. Thus we protect for this condition.

Cheers,
TheOddOne

[Riverboat]

There you are, carrying out your Cat 1 ILS approach, with the needles nearly crossed, or if you have a FMS, totally crossed, and suddenly the ILS fails. What happens?
You go around. I must admit I can't quite see the argument for only allowing (or promulgating) a non-precision approach if a stand-by generator isn't available. Different if it is Cat II or III, as you could be in a rather awkward spot, but not Cat 1.
Furthermore, I agree with 411A - it's nothing to do with the airport ATC what my MDA is - at least it isn't according to my company Ops Manual, which doesn't mention stand-by generators anywhere. Does anyone elses Ops Manual do so?
RB

[discountinvestigator]

Originally Posted by TheOddOne

discount,

I'm puzzled by your assertion that diesel generators are used for backup. We certainly don't use them like that.

Our SOP is to use a ring main as its own backup. Thus, a break in the ring DURING any period of LVPs is covered by the supply coming around the other way, so to speak.

If the ring is interrupted before the onset of LVP, then it can't be used as its own backup. What we do then is to use the Diesel generators as the PRIMARY source and the mains as BACKUP. That way, we get the 1 sec changeover required for CATIII. This doesn't cost any more, just a bit of lateral thinking to give the result.

I'll also repectfully disagree with you about there being a difference between LVPs due low cloud and low horizontal surface visibility. Yes, we often get situations where we are 200' cloud ceiling but several km under it. We still need LVPs in this circumstance, so that when crews cloudbreak at 200', there is a reasonable chance that the a/c is aligned with the runway. I reckon you've got less than 15 secs between a 200' cloudbreak and the flare in a big a/c. That's supposed to be possible to hand-fly for a CATI approach. Thus we protect for this condition.

Cheers,
TheOddOne

I am aware that the main way to achieve the one second change over time is to use diesels as primary, with mains as secondary, at many airports. Also there is the double ring. However, see the paragraph below as to whether this was required or not.

I wish to continue the debate about the split in low visibility and low cloud procedures further. If you had no CAT III system, and only a CAT I ILS, would you still put in low visibility procedures for low cloud and high visibility operations? I would suggest not. The change in the ILS signal deflection when using CAT I holds for departing aircraft and flying to a 200'DH is still manageable. The main signal deflections are from large tails vacating at the end of the runway or from big wings in overflight. Yes, there are other reflections etc. A 737 old generation I seem to remember gave a return to CAT III signal when vacating most of the way down a runway and its tail was 60 metres from centreline, for example. At the CAT I hold, it does not eat all the dynamic ILS tolerance up.

The main debate should be on the total disconnect between JAR OPS 1 requirements and CAP 168 requirements. If it was high visibility and daylight, why would the crew need all of the other lights apart from PAPI, they can shoot the approach with the lights out anyway! Many operators do not even require a PAPI, but I will not go against Annex 14 in this area. I feel that no PAPI = no approaches. I still feel that the lower risk option was to continue operations with the ILS.

[Data Dad]

Spitoon - the CAP 168 reference is Chapter 6 page 29 & 30 (section 10) and more specifically para 10.4.

The argument about LVP's for Cat 1 at this airport has raged a long time!

Meantime the Aerodrome Manual and our Mats Part 2 state that we have to do it.



DD

[discountinvestigator]

Purpose of a procedure

Perhaps if we split up the ideas, then we can develop procedures and apply them at the right time.

There are procedures to protect the ILS signal. These are required for when the aircraft requires them, and that is RVR less than 550m. Keep on packing them in until then. After the second go-around, maybe it is time to slow it down a bit and go to CAT II or III approach separations and use the CAT III holding positions. As for me, I think you should always use the CAT III holds anyway.

There are procedures to protect the lack of vision from the tower. I would suggest that these may be more appropriate for operations in the dark and also in visibilities significantly higher than RVR 550. If you cannot see a grey truck on the concrete at the other end of the aerodrome, you might want to go "procedural" with ground operations. This requires the locking of gates, lowering of barriers and the rest of it.

When there was only one Trident or Caravelle on approach, it could be a combined procedure and nobody minded. With well over 90% of aircraft at some airports equipped to CAT II or III approaches and low visibility take-offs, is it not time to take another look at why the rules were written that way in the first place?

[A7700]

Originally Posted by Ed Set

An "interesting" situation today at my CAT1 equipped airfield.
Visibility is 7KMS but cloud now drops to OVC at 200 feet therefore Safeguarding and Low Visibility Procedures are technically required, As I understand it, one of the main reasons for introduction of CAT 1 safeguarding would seem to be runway protection from unauthorised vehicles, the good visibility would have precluded this allowing everything to be seen with no problem?

Discuss!!
Ed

Low Visibility Procedures were initiated by ECAC in 1988 in their DOC 17.The aim was to protect the ILS signal for CATII and CAT III operations. If your ILS is only CAT I , you don't need LVP.
Some airports have implemented "safeguarding measures" before to implement LVP in order to avoid a sudden and hard transition in the available runway capacity. But again the regulation does not request that kind of local procedure if only CAT 1 approaches are available.
The ICAO DOC 4444 do not recognize LVP: The mention in chapter7 is about "Low visibility operations" which are just "procedural control" when the controller does not have visual contact with the traffic outside. Then there is a list of "additional requirements" when there is a need to perform CAT I and II approaches.
There is an ICAO draft manual on LVP (It is just a manual, not a PANS) which still need to be upgraded to reflect the reality.
And finally there is a pending proposition to implement an LVP definition in ICAO DOC 7030 EUR by the ICAO Air Navigation Planning Group end of november 2007 :
Low visibility procedures (LVP). Specific procedures applied at an aerodrome for the purpose of ensuring safe operations during category II and III precision approaches and/or departure operations in RVR conditions less than a value of 550 m.
Still far away from Airport that are only CAT I equipped.

[Data Dad]

On further reflection I am coming to the opinion that LVP's for CAT 1 ILS approaches is a little bit of a red herring!

I believe (now) that we have Safeguarding/LVP's (at our airport with CAT 1 ILS) not to protect CAT 1 approaches but in order to protect departures which of course can continue at IRVR values much lower than arrivals.

From the UK AIP AD 1-1-7 para 2.12:


"Low Visibility Procedure (LVP).

Procedures applied at an aerodrome for the purpose of ensuring safe operation during Category 2 and 3 approaches and Low Visibility Take-off. (LVPs are initiated when the cloudbase lowers to 300 ft and is expected to lower further or the RVR falls to 1200 m and is expected to deteriorate further. They should be fully in place by the time the cloudbase reaches 200 ft or the RVR falls to 600 m.)"

Thoughts please! (V Interesting discussion BTW)

DD