Using another ILS for cloudbreak

[Baikonour]

In another thread, there was reference to "you can use the [airport 20 nm away]'s ILS for cloud break".

Can anyone explain how this actually works and whether it really is a good idea?

As I understand it, if you get down to minima (on an approach you do not actually want to complete), you continue with the published go-around procedure and you will be in the same position you had been in if this was really the airport you wanted to land at - potentially eventually needing to divert to your alternate.

However, if you do get under the cloud cover, you will (presumably) be relatively close to an airport you don't actually want to land at and, in practice, probably in controlled airspace?
At that point, you break off the approach and 'resume your own navigation', scud running towards another airfield in the vicinity.

Which sounds a bit borderline to me.

Would ATC at the 'unwanted' airport not be slightly surprised by this (ignoring the fact that they'd probably send you the bill for an instrument landing?) and/or will you not be in breach of your contract with the controller?
Or do you inform them from the outset that this is just a 'cloudbreak' approach?

I guess my real question is what you gain by this. If there is a decent ceiling (1500 feet agl, say) , you should not need an ILS to break through the cover. And if the ceiling is low (towards minima), I would be uneasy about the 'false' ILS approach for the reasons above - and then still have the scud running under a low ceiling to do as well...

What have I misunderstood?

Thoughts appreciated.

B.

[chevvron]

Perfectly normal procedure although '20 miles away' is pushing it a bit!

[Shaggy Sheep Driver]

I've heard of the Manchester ILS being used by traffic inbound to Woodford when the Woodford ILS was out of service.

We once did an instrument approach to Benbecula with the intention of going around and continuing VFR to Barra. But when we became visual, all we could see in the murk was the Benbecula lights! So we landed there.

[ASRAAM]

I have flown an ILS into Cardiff to overshoot followed by a landing at St Athan. The short transit was within the military low flying rules and either the radar was out at St Athan or the SRA limits were quite high, can't remember which now.

[Bob Viking]

When you bear in mind that a 750' cloud base is legal for LL FJ ops the ILS is perfectly feasible as a means of entering low level. You should choose your airport and words wisely though. Shooting an approach into a busy airport with the intention of pootling off to low level afterwards might be a touch inconsiderate.
BV

[ShyTorque]

Sounds like some need to get out a bit more! As Chevvron said, it's a perfectly normal procedure, obviously done with ATC approval where necessary and it needs to be carefully thought out in advance. Obviously, the 1,000 foot rule needs to be adhered to where necessary.

I've had to do this a number of times to get to a landing site in poor weather, perhaps two or three times a year. Some pilots do it quite routinely. Sometimes you get a bill for the approach, sometimes not. If you do get billed you pay up, so no-one objects (some PPRuNe armchair experts excepted, of course, who have obviously never had to do it in the real world). :rolleyes:

As I understand it, if you get down to minima (on an approach you do not actually want to complete), you continue with the published go-around procedure and you will be in the same position you had been in if this was really the airport you wanted to land at - potentially eventually needing to divert to your alternate.

Why would you plan to go around on the MAP? If the weather is that marginal, you should plan on landing at the airfield you're doing the ILS to, not trying to continue VFR.

Normally you would break off at a sensible height as soon as you obtain visual references then continue to your destination under VFR.

[piperboy84]

Do part time towers turn off the ILS when they knock off for the evening ?

[glendalegoon]

HI

first off, I speak of the USA only. NO , nav aids are not turned off at night to save power. We utilize our airports 24 hours a day (noise restrictions aside...but the ILS is still on).


Second off, utilizing an instrument approach (of any kind) at one airport and then proceeding visually to another airport is just fine as long as you coordinate it. It is not marginal as long as you are in compliance with existing regulations. And that you are competent.



Now, what to do ? IS the airport you intend to go to without an instrument approach? IS the wx reported / forecast to be at or above basic VFR (VMC)?

YOU can ask for radar vectors at the minimum vectoring altitude OVER the airport you intend to land at, and if YOU can proceed VFR, advise ATC of cancellation, or request a visual approach and go to the airport and land.

But lets say the ceiling is solid (undercast complete) and you cannot see the airport, but it is reporting 1500 OVERCAST and 3 miles visibility. And so is the airport 20 miles away and it has an ILS. Fly the ILS and ONCE YOU ARE VMC/VFR , cancel the IFR and proceed (with other clearance depending on airspace) to your intended airport.

Even more and niftier things can be done if you properly coordinate and receive clearance for an ILS, and then get a SPECIAL VFR clearance and then proceed in basic vfr out of one airport to the other.


NOW, I don't want to tell you what to do, because if you have to ask on PPRUNE, you probably need some more flying lessons.

So, be careful and maybe find a really good flight instructor/instrument instructor...you know, someone with a couple of thousand hours and have him teach you. And then pay him well because he has to earn a living too.

[BackPacker]

I agree with Shy. You use such a procedure when you're in IMC, or VMC-on-top, and you know/suspect the cloudbase is below the MVA, MSA or whatever your minimum IFR altitude is at the time. So you can't descend safely below the cloudbase in just any odd random location.

So instead you use the arrival and approach procedure of a convenient airport to safely descend below the cloudbase. Once you are below the cloudbase, you continue VFR to your destination. And if the cloudbase turns out to be too low for (safe, comfortable) VFR, you either fly the missed approach and continue IFR, or you land at the airport that offered you the instrument procedure in the first place - in effect a diversion because your destination cannot be reached VFR.

Obviously if you only break out at minimums (typically 200 feet on an ILS) it would be pretty stupid - not to mention illegal - to continue for another 20 miles under the 200' cloudbase to your destination. But if the cloudbase is at, say, 1000 feet, then this method is very convenient.

[Jonzarno]

FWIW it was me that posted the original comment about using the Glasgow ILS for cloud break to Cumbernauld.

I've done it several times and the original advice to do it came from Cumbernauld airport.

As has been posted already, you just ask the controller you are already talking to and they will arrange it for you quite routinely.

On one occasion, I tried to do it and couldn't break cloud high enough to be safe and ended up actually landing at Glasgow. Both landing fees and handling costs were reduced by 50% under the Strasser scheme but still hurt! Both ATC and the handling agent were very good though.

[Skeeve]

Do part time towers turn off the ILS when they knock off for the evening ?

Even if they do leave the ILS on, it may not be where you expect it.

Some airport have the same frequency of the ILS for both runway directions (e.g. EGGC 23R/05L), so they DO switch off the ILS of the direction opposite of the "active" runway.

[Chilli Monster]

Skeeve - if the airport is closed how can you have an "active" runway. It may not be co-incident with the prevailing wind, that's all. Thats one of the reasons you ident the ILS, to make sure you know which end of the runway the ILS is selected on.

And like others here - as an ATCO I've offered cloudbreak ILS's (nobody's ever received a bill) and as a Pilot I've requested and been given them. Very useful with cloudbases just above circuit height at destination airfields. Just make sure you know the topography for transiting between the two.

[glendalegoon]

airports are rarely if ever technically closed. air traffic control tower might be closed, in which case you use common traffic advisory freq and good luck

air traffic control rarely decides to close an airport, they can act as agents to the managing authority as if they want to plow the runway for snow and close the airport.

atc may have a letter of agreement/MOU that they will declare the airport closed if CRAF has deployed to rescue/handle fire of a crash as the CRAF could then NOT respond to a second crash.

IT is however possible that the runway lights might not be on the step you wish them to be and clicking your mic on CTAF might (if equipped) change the setting.

go find a nice , competent CFII and good luck

[ShyTorque]

Not many UK airfields have RT controlled lighting. In fact I can't think of any, although I know of a few helipads that do.

[Chilli Monster]

airports are rarely if ever technically closed. air traffic control tower might be closed, in which case you use common traffic advisory freq and good luck

In the USA yes, but Europe is totally different - airports have hours of operation, and are closed outside of those.

[charliegolf]

ASRAAM, what aircraft were you flying- purely out of interest? Ta.
CG

[piperboy84]

In the USA yes, but Europe is totally different - airports have hours of operation, and are closed outside of those.

But does that mean you are not allowed to shoot the approach after hours for cloud break then continue on to your home strip

[Chilli Monster]

What you do, in class "G" airspace, is your business.

[dont overfil]

Do part time towers turn off the ILS when they knock off for the evening ?

I know the one that matters to you Piperboy. Yes, Dundee does.

D.O.

[piperboy84]

Thanks DO, so the next question would be the leuchars ILS can that be used if it gets you down to visual prior to entering there immediate ATZ but within the surrounding MATZ ?

[BackPacker]

Correct me if I'm wrong but I would assume that if you're cleared for the ILS, you are implicitly cleared to enter the ATZ, even though you fly the ILS for cloud break purposes and not with the aim of an eventual landing.

There's just too many "what if's" if you get a clearance like "Cleared for the ILS approach, report VMC, do not enter the ATZ". What happens if you do not become visual before entering the ATZ? You are most likely below the MSA now so you can't simply circumnavigate the ATZ. Something that would be tricky with a moving map GPS, and almost impossible without a GPS anyway. Obviously you can try to climb above the ATZ but practically speaking that would mean that the go-around decision needs to be made at 1200' or so (*) - which makes the whole cloud-break procedure pretty pointless.

(*) Assuming a standard 3 degree ILS and a 3-nm, 1500' ATZ. If you want to fly the ILS to the furthest extent possible, you need to go-around at about 4nm/1200' at the latest, in order to be at or above 1500' at 3nm.

[piperboy84]

(*) Assuming a standard 3 degree ILS and a 3-nm, 1500' ATZ. If you want to fly the ILS to the furthest extent possible, you need to go-around at about 4nm/1200' at the latest, in order to be at or above 1500' at 3nm.

Only getting down to a 1200 ft MDA would probably work fine as I would need at least that minimum to navigate terrain between the ILS field and my intended destination strip. So if not visual at 1200 and as the approach is over the sea, just level off , hang a 180 climbing back on top and find somewhere else to land.

[dont overfil]

From time to time aircraft inbound to us use the Dundee ILS and break off at low level when VMC. They need to know the low level route from there as direct will not usually work .

The same is possible at Leuchars but again the low level route would need to be planned in advance. They are also able to offer a cloudbreak over the sea.

Leuchars are no longer 24/7. I don't know if they switch off their navaids.

D.O.

[piperboy84]

They are also able to offer a cloudbreak over the sea

How does that work?

[Chilli Monster]

(*) Assuming a standard 3 degree ILS and a 3-nm, 1500' ATZ.

UK ATZ's are 2000ft and either 2 or 2.5nm radius dependent on runway length (1850 metres being the deciding figure).

Also - you can't be cleared for the ILS if the aerodrome is closed, which is where the thread is at the moment.

[dont overfil]

They are also able to offer a cloudbreak over the sea
How does that work?

They will vector you offshore, remind you that you are responsible for your own terrain clearance and let you get on with it.

Reliable GPS has made this almost almost redundant.

D.O.

[glendalegoon]

JUST a piece of advice...if you are doing a cloud break via ILS, I would think doing the LOCALIZER only apch would get you down faster if you like and then you will have more time to look at the wx conditions.

[dont overfil]

JUST a piece of advice...if you are doing a cloud break via ILS, I would think doing the LOCALIZER only apch would get you down faster if you like and then you will have more time to look at the wx conditions.
I don't understand that one! Are you suggesting flying below the glideslope???
D.O.

[BackPacker]

Are you suggesting flying below the glideslope?

I think that's actually what he meant.

On an ILS you use the glideslope for vertical guidance. Easy but out of technical necessity the glideslope is a straight (sloped) line leading to a constant descent.

When you do a LOC/DME or VOR/DME approach it is perfectly feasible to have step down altitudes during the approach which let you descend earlier than what's technically possible on an ILS approach. For instance, a normal ILS requires you to be at 2000' AAL at 6 nm out. But a VOR/DME approach may consider it perfectly safe to descend to 1500' at that distance - obviously if terrain allows.

So with a LOC/DME or VOR/DME approach you may well be able to safely descend earlier, indeed below the ILS glidescope, and get into VMC earlier. Whether that really makes a practical difference, I don't know. Plus, ATC will probably assign you the ILS approach out of habit anyway, even if in this particular case a LOC/DME or VOR/DME would be more convenient for you.

[glendalegoon]

thank you backpacker for understanding.

WHAT I DO NOT UNDERSTAND is how someone with a full instrument rating would not understand this.

I STRONGLY ENCOURAGE YOU TO FIND A REALLY GOOD INSTRUCTOR with LOTS OF REAL INSTRUMENT FLYING EXPERIENCE dear OP!!!


the glideslope takes you to the runway (loc too). but you are going to a completely different airport SO GET DOWN AS QUICKLY AS YOU CAN (within published , safe limits)

then you can start looking for your other airport.

really, how don't you understand this?

[dont overfil]

Thanks Backpacker, I do understand there is an opportunity to descend slightly earlier on a LLZ app but I don't think it is a good idea to make a rush for a break as there is little advantage to be had.

Glendalegoon,
Chill. I was origionally replying to Piperboy as I am familiar with the airport he would use. I was emphasising that his local knowledge would be required as the airport in question already has a steeper than normal glideslope and there would be no risk of him seeing his destination at that point anyway.

D.O.

[glendalegoon]

real life flying means finding a break , knowing where you are and then going for it.

if you don't take the first break, there might not be a second.

this is a little like barnstorming, but either you know what you are doing or you become extinct.

a piece of advice to the original poster.

as you seem unsure of this concept, please, only try it in good wx before you do it in bad wx. in this way, you can understand the communications, coordination and study the terrain in good wx. you can also try the concept of using the localizer only approach.

and if ATC clears you for one apch, advise them you plan to do the other apch and get an amended clearance.

good luck, fly safe, support your local flight instructor (professional).