Flying Airways in the UK?

[Contacttower]

Soon I may finally be able to file airways regularly in the UK using my FAA IR and an N-reg aircraft. However after doing my IR in 2008 and coming back to the UK looking over the airways charts has left me slightly bemused; for example, one regular flight that I might want to take would be from the south of England to Scotland, on inspection of the route it seems that from 0700-2000hrs airway N601 has a MEA of FL140, making it impassable without oxygen. In general a lot of the airways seem to have quite hight MEAs compared to the US, I guess because we have mainly class A only airways and only put them where commercial flights need them. Is there any way round this though? Is it possible to file an IFR flight plan that is only partly in the airways with some parts dipping below out of CAS?

[IO540]

I've sent you a PM with some trip writeups, but yes, in short, European IFR flight is difficult without oxygen - not because you cannot generate routes at FL100 or so but because flying that low places you squarely into IMC which (most of the year) means likely icing conditions and almost inevitable turbulence of varying severity.

The name of the game is therefore a climb to VMC on top. In my book, this also means that the flight is scrapped if the cloud tops are too high - unless you have a solidly deiced aircraft.

OTOH there is a significant pilot population who "just fly" but I am not among them. The smarter ones are doing it in deiced planes, and preferably without passengers :) Obviously, the well funded ones are doing it in pressurised planes, at FL200 plus.

Working out routings (there is an automated tool for it so you don't need the SRDs) works at FL070 but you get poor routes. FL100 is better. FL140 is better still and above that there is very little to gain except in the Alpine region where you need FL160. Then next big improvement comes at FL200+.

[Pace]

Contact Tower

The answer is YES. On the flightplan put the airways you can stay in ie NXZ WAL then the bit you cannot stay in but are flying under put DCT instead of the airway to the next intersection/ point where you hit the airway again.

One example is flying from Scotland arriving at DCS you wont pick up CAS at lowish level until 20 North of WAL. For that section you will get a deconfliction service from warton and get handed back into CAS North of WAL

In the remarks column put IFPS Reroute accept so you dont get the flight plan thrown out and accept whatever routing you get. Airbourne its then easier to negotiate your routing you want.

The other way is on the flightplan to put the higher level to keep in the airway to get the plan accepted but then airbourne ask for lower as in reality you have no intention of flying the higher level.

Pace

[bingofuel]

You do not have to be in controlled airspace to fly IFR and you do not have to fly IFR in controlled airspace. The problem you may have, will be if you fly a route where you drop below the base of CAS and then intend to re enter CAS as its base lowers, you MUST obtain a clearance to do so. Do not assume that filing a flight plan automatically gives you clearance to enter controlled airspace. Normally itis not a problem BUt it would be prudent to have an alternative routing in case the controller says those unwelcome words 'remain clear of controlled airspace' and you are IMC at lower levels!

[IO540]

Well, yes, here one just has to assume that the OP is familiar with the difference between "Eurocontrol IFR" and UK's "informal IFR in Class G", and also how the two can sometimes interact in bizzare ways....

Eurocontrol IFR in the UK can be tricky at low levels (anything below about FL140) because if you - inadvertently - file a route which has an OCAS section, you can be dropped out of CAS, London Control's service is terminated, you get handed to London Info, and then you are stuffed because your IFR clearance has been binned and you won't get back in unless LI negotiates a new clearance with LC, which could take some time - or never if they don't feel like doing it. It does catch out foreign pilots, occassionally.

[Contacttower]

That's interesting, it had occurred to me to do what Pace suggests, but I was afraid of what IO540 and bingofuel warns might happen as well.

I take it Pace you know that what you suggest is acceptable to ATC? Also what does "PPSC Reroute accept" actually mean?

[mm_flynn]

I have found that when I drop out then back in (going up North or back from Ireland) that the Information service normally includes in the initial response a request for eta at the joining point and tells me they are arranging my cas entry. If they don't I immediately give them my entry point as in 'nxyz ifr fl100 re rentering CAS at GECKO at 17) and information then sorts it.

This doesn't work when you are dumped as in 'descend to altitude 4500 cleared to leave CAS by descent'

[Midland Transport]

My view is that you would be better off filing non airway IFR in the UK. Dropping in and out of Class A is painful and when you want to join again you will end up going round in circles. Unless you can stay in the low airways en route system it really is not worth it.

[IO540]

My view is that you would be better off filing non airway IFR in the UK.

I tend to agree, and this is what I do (rarely fly Eurocontrol IFR around the UK). Depart VFR and disappear in the nearest cloud, no problem.

But flying around at 2400 / 3400 / 4400 ft / FL054 / FL064 etc ;) is often not a lot of fun. ..

Take a nice summer day with a lot of nice fluffy white stuff and you have a very rough flight. Going airways at FL100-150 is a good way to deal with it - which is precisely why one does it around Europe. One could fly "VFR" (OCAS) around Europe too, down in the muck.

The other example is winter flying, when the 0C level is close to the ground, and there is just a thin cloud layer. If you fly "UK VFR" (perhaps in IMC) then being below CAS base you will end up in icing conditions, possibly for hours. This is OK in an Aztec with boots (which after all has another incentive ;) to fly "VFR") but most GA planes are not de-iced. Whereas an airways flight will transition to VMC in minutes and sit there enroute.

[HEATHROW DIRECTOR]

<<you do not have to fly IFR in controlled airspace>>

You surely do in Class A?? Or have regs changed.

[Contacttower]

OK. Thanks very much for all your replies, it seems to me that this is something that can be done but has the potential to be a bit difficult sometimes, I can only try and see I suppose. Longer term I'll just use oxygen.

[Captain Stable]

If you file your flight plan at a reasonably-equipped airfield (such as, say, Biggin Hill), ask the tower to file it for you. If they get any objections or reroute requests from Brussels the tower will be able to advise you how better to route your flight.

[Pace]

Contact Tower

You specifically mentioned London Scotland :) I have a lot of time in light twins in those areas. 10540 is correct in warning you about icing in anything but the height of summer unless your aircraft has proper deice/anti ice.

having said that there are two elements.

Firstly putting in an acceptable flight plan which wont be thrown out and secondly the actual route and levels you will fly or negotiate with ATC when you are airbourne and in the system.

Putting in a flight plan IFPS Re Route accept means that if there is a mistake you are happy for a correct route to be put in for you. This saves the plan being coughed out, but now their is more resistance to IFPS re route changes and sometimes even with that your plan can be kicked into touch.

In years of flying I have never been refused re entry into the airways further along the line.
ATC know your predicament in a non pressurised aircraft and are more than helpful as they are with levels and more direct routings.

I can even remember flying back from scotland at night through a front. On leaving the front near Glasgow although the aircraft had dealt with the ice there was a lot on the airframe and the cruise speed was low. I asked to be allowed to drop out of the airway down to FL60 so that i could drop off the ice, climb back up and continue. That request was approved and I maintained radio contact with the airways controller.

Without going into details there are tricks we play to work the system to our advantage. This happens in low airways and high airways both in twins I fly and in jets I fly in the high airways and these are known and used across the board by those who live in the airways system.

Take care and other than the summer beware in a non deiced aircraft. It also helps to carry oxygen if you have to comply with the higher levels you may have filed ;)

Pace

[IO540]

<<you do not have to fly IFR in controlled airspace>>

You surely do in Class A?? Or have regs changed.

Of course A is IFR-only (the irrelevant SVFR case excluded). What he was referring to is the ability to get around the UK pretty well in Class G, VMC or IMC, and IMC=IFR :)

If you file your flight plan at a reasonably-equipped airfield (such as, say, Biggin Hill), ask the tower to file it for you. If they get any objections or reroute requests from Brussels the tower will be able to advise you how better to route your flight.

I think things have moved on since ..... when....the 1950s... ??

Putting in a flight plan PPSC Re Route accept means that if there is a mistake you are happy for a correct route to be put in for you. This saves the plan being coughed out, but now their is more resistance to PPSC re route changes and sometimes even with that your plan can be kicked into touch.

I think this is meant to be written as "IFPS reroute accepted". This tells IFPS (Eurocontrol) to not generate an automatic REJ but to pass the failed FP to a human operator who, subject to workload and other human conditions ;) will have a look at it. I've been there, to the very desks where they do this. It's a manual process - dragging routes on PC screens.

There is no guarantee they will do this (the IFPS manual says so plainly) and indeed on one of the times when I was unable to get a route to work (last time was 2007) and was in a real pickle they would not assist, and as I was at an airport with a 5-day PPR for both arrival and departure I had to cancel the next flight and go elsewhere, and this was a really major problem.

They will also not fix up routes which are drastically wrong.

The other thing is that the modified route needs to be somehow communicated to the pilot so he knows what he should be flying. In theory this is the responsibility of the office which files the FP. This introduces certain issues because by the time this happens he will be in/near the plane........ homebriefing.com send you an SMS or email but this will contain the airways-name route and you then need to generate a plog from that so you have the individual (non-airways-name) waypoints to load into the GPS... AFPEx do not have such a facility (yet) so that service is best used only for known-valid routes.

I would therefore not rely on using this remark. Better to use the available tools to get the route right, file it without the reroute option, and go.

I think that the odd UK airways system works because most of the traffic is jets which go up to FL2xx right away. The rest of Europe is much more straightforward for IFR GA, fortunately. Also it appears that Scotland is a lot better than the south :)

[Pace]

I think this is meant to be written as "IFPS reroute accepted".

10540

My apologies typo error and brain fade :hmm: Of Course IFPS. :O (rectified) It does still work 70% of the time and not always in the right place to have all the wizzard tools at hand.... so still useful... and for the small effort to put it in a safeguard against getting the plan chucked out.

Pace

[fisbangwollop]

Pace..Without going into details there are tricks we play to work the system to our advantage.

Shock horror surely not :)....dont admit to that with us Air traffikers listening in!! :cool::cool::cool:

[Contacttower]

You specifically mentioned London Scotland :) I have a lot of time in light twins in those areas. 10540 is correct in warning you about icing in anything but the height of summer unless your aircraft has proper deice/anti ice.

I certainly appreciate you sharing your experience :). On the point of icing yes I'm very aware of it, my original question was quite theoretical in the sense that it was only about airspace and not about the overall subject of actually flying from A to B in reality, which of course requires consideration of many things... with icing being one of the more important ones.

[Midland Transport]

I believe it is worth you joining PPL-IR Europe you will get lots of very useful help on flight planning and operating in Euro airspace. Asking the tower to submit your flightplan is ok but I strongly suggest you verify the route first on cmfu.eurocontrol. The site is a bit non user friendly at first but it will really help you to build confidence by getting the flight plan accepted first time. I use Flitestar and I have never got a plan accepted when just using the programme output but by using the veryfier you will learn the accepted routes as around Europe if you are flying north south from the uk or in the uk there are not that many airways to choose from at low level it is the entry and exit points that can be confusing.

[Pace]

Shock horror surely not ....dont admit to that with us Air traffikers listening in!!

Fisbangwollop

How many free pints have you been offered for a direct destination ? and whats a flight level or two between friends ;)

How many calls have you had claiming severe icing or turbulence for a higher level maybe a 20 degree left or right due severe weather which just happens to be direct destination and the list is endless ;)

Anyway isnt it different in Scotland? spend all your time in airways avoiding microlights and watching the local pastime of "tree landings" :rolleyes: wonder how Mc Biggles is getting on?

Pace

[camel toe]

I've popped out of an airway in the past where there has been a change of base level. I continued on the navaid as if I was still in the airway and then I just requested that ATC co-ordinate my return back into the airway when the base stepped down again.

If I recall correctly they requested an ETA, and I was reminded to "remain clear of controlled airspace". Approx 5-10 minutes before reaching the airway I was given a new SQUAWK code (classic sign that you are about to be passed to another frequency), I was passed to the agency controlling the airway who promptly cleared me in. Easy!

If my memory serves me correctly I was flying north from Exmor in the N864

Other worthy point of note was that the SQUAWK code given to use when I re-entered the airway was the same as was issued on departure from Exeter, this has happened on a number of occasions. I've always had first class service from ATC in terms of airways flying.

I would also re-iterate the icing points, be careful and make regular icing checks, both visually of the airframe, spinners, OAT etc and also watch for a reducing IAS. Always have a plan B whether it be a descent (obviously with terrain in mind) or en route diversion.

If you dont do it already consider making a note of the freezing level on departure as you climb through it. This will change as you travel through a changing airmass but I've often found it more accurate than the forecast levels. You will then know what level to request a descent too if you need to shed some ice.

I've descended before to shift some ice and requested a level based on the zero degree level I had noted down during my departure, and despite it being over an hour later it was still very similar and I flew along at the level that was just above 0 and cleared it up quickly.

Having this information will hopefully reduce your workload at what can already be quite busy by not having to request further descent or descending more than you need to.

Apologise if the icing lesson seems to come across as a lecture I only intend it as friendly advice :ok:

[tom_ace]

I've done midlands to north scotland sometimes airways and sometimes IFR outside controlled airspace (mostly, just negotiated clearance when required), and to be honest it's a lot less painful to do the latter if you carefully choose the route. As the other posters have said, the icing issue does not suit a non pressurised aircraft at all for this route. I found it much better to stay low, below the freezing layer with not too much bitting and bobbing between airspace.


edited becuase I've had a beer

[scooter boy]

I am in agreement that IFR OCAS is usually the most expedient way to do IFR in the UK.
My aircraft is deiced with a service ceiling of FL200. Not worth climbing anything like that high unless you intend to do a long trip.

Flying from Plymouth my usual airways joining point is BHD at FL90 - this is OK for south and North destinations, but there is no real east-west option at a reasonable altitude unless you want a detour over the Brecon Beacons (no fun in the winter).

After figuring the above out another wakeup call for me was being treated like persona non-grata by Solent radar (no surprise there) at night in IMC having filed an IFR flightplan from London back to Plymouth. I had no idea that they were not aware of my flightplan.
Basic message was "stay out of our airspace we are not interested in you. Freecall en route..."
How about a nice warm squawk to make me feel welcome, comfortable and safe guys?

SB

[IO540]

After figuring the above out another wakeup call for me was being treated like persona non-grata by Solent radar (no surprise there) at night in IMC having filed an IFR flightplan from London back to Plymouth. I had no idea that they were not aware of my flightplan.

Yeah; you discovered another UK airspace secret ;) IFR flight plans filed below the magical "enroute airspace" go basically nowhere enroute, and no IFR clearance is maintained. A lot of people have been caught by that. Solent is just a bit of Class D around an airport or two. To get a continuous IFR clearance in the UK one needs to file for something like FL120 or higher, to be sure it will "stick".

[BEagle]

I think the main problem associated with flying in IMC outside CAS in the UK is, as been inferred above, the lack of reliable radar cover.

Perhaps one of the few areas of UK life not under constant surveillance from nuLabor's nanny state goons!

It is not illegal to fly IMC without any radar cover or even without talking to anyone - but it's perhaps rather foolish. Hence the attraction of lower level airways to those appropriately qualified flying suitably equipped aircraft.

[IO540]

It is not illegal to fly IMC without any radar cover or even without talking to anyone - but it's perhaps rather foolish.

It appears foolish but the IMC midair stats (zero, zilch, none, nil, since WW2) do not support such a fear.

Hence the attraction of lower level airways to those appropriately qualified flying suitably equipped aircraft.

Sure, you need an IR etc. But it doesn't work too well in the UK, especially the south. The lowest levels at which one can get LTMA crossings are around FL100 plus. People who succeed in filing a Eurocontrol routing at FL070 or so (and it is possible) end up either vectored all over the place, or get dropped out of CAS at the first convenient (to ATC) opportunity.

Also if you fly at say FL070 you don't have to go very far away from London to find yourself in Class G, and then the service from London Control will most likely be terminated, your IFR clearance is in the bin, and you have to continue OCAS.

As many pilots have discovered, you can fily flight plans via Eurocontrol even lower e.g. FL050. These are meaningless and end up in meaningless flights - forced below CAS, probably from the start.

[mm_flynn]

How does that compare with Victor airways in the US, which as far as I know, start at around 1200ft where you're given separation from other IFR flights by "Center"?
IFR OCAS works just fine in the UK ... BUT, it is based on a different operating assumption than the US.

American's believe airplanes will hit each other or the ground if they don't follow routes (Victor airways) and receive a separation service. In the UK the volume of IFR OCAS traffic is low, the country is flat, and the routes are random. All of this means no aircraft in IMC has hit another (since one incident in WW II) even though separation is only provided on an adhoc basis. The CAA/NATS structure is geared to providing ATC in a limited set of Airways (defined for commercial traffic) and approach areas - and a very basic level of service OCAS. Once you accept Big Sky Separation works just as well as ATC for typical OCAS flights you will find the UK system actually seems to work pretty well.

[Pace]

Once you accept Big Sky Separation works just as well as ATC for typical OCAS flights you will find the UK system actually seems to work pretty well.

MM

I dont know whether you remember the long thread sparked by my near miss with a glider in IMC in a twin? It passed so close I saw it in the clouds :{

The fact is we all think that IMC OCAS is the world of small light GA. That airpace is also inhabited by commercial aircraft right up to A320 s and 737s.

All will be fine until the day the unthinkable happens then all change

I would certainly make it obligatory to have a transponder with altitude reporting to be legally allowed to cloud fly

Pace

[mm_flynn]

Yes I saw the thread. If the rules were being written today, everyone would have 'ADSB' and for most en-route airspace pilots would self separate with ATC coordinating traffic in busy areas.

The core fact for FAA trained pilots to understand is the FAA infrastructure doesn't exist here - you either live with it or don't fly in IMC OCAS (as you can't count on a Radar Deconfliction Service).

In the US an operation of this sort would have your ticket pulled due to reckless endangerment (i.e. the regulatory belief you will hit someone or something if you fly blind with no separation/coordination). The CAA clearly have had a view for years this is a reasonably safe activity (and for what ever reason, the accident rate (of 0) doesn't refute this view). I do recognise this may simply be due to very few people operating IMC OCAS with no service (like the Concord - a very small fleet so 0 fatals until the day there was one, at which point it moved from the safest (0 fatal accidents/1000 flights) to the worst safety stats of any modern airliner).

[IO540]

this sounds impractical for a small Cessna 152 to make a short direct journey from one aerodrome to another whilst in IMC where typical flying altitude is somewhere between 1500-6000ft.

You would fly a C152 in Class G, generally.

What are people's experiences of flying in IFR in IMC in Class G airspace in the UK?

It's done all the time. I did nearly an hour's worth this morning :) No midairs in IMC in the UK, since WW2. In VMC, about 1 a year.

Is the LARS Deconfliction Service reliable/good, and how well do they provide separation?

It's OK when the weather is bad, but then almost nobody is flying. When the wx is good, they often don't provide a radar service; just a Basic Service "due to controller workload" (which is useless; you may as well be flying with a listening watch).

How does that compare with Victor airways in the US, which as far as I know, start at around 1200ft where you're given separation from other IFR flights by "Center"?

Play with the Eurocontrol routing tool (see other airways thread). I think IFR is pretty similar but in Europe one cannot generally go as low as in the USA. I think the US airways have their MEAs based on the higher of a) terrain i.e. MOCA and b) MRA, whereas most European airways have high bases seemingly unrelated to obstacles or navaid reception.

Based on the above, is it worth asking CAA/NATS to provide more direct, lower level Class E airways, which open up in non-icing conditions?

You could ask them but pigs will fly 100 years sooner :) Here, ATC is privatised and nearly all of of GA pays no route charges, so they do the minimum legally required of them.

Yes it would be great to have the US-type (or French-type) Class E system...

But just departing VFR and drilling a long hole in the Class G clouds works fine. The sky is a very big place, and almost nobody in the UK flies in clouds. Also, most UK pilot forum readers think they get a nosebleed above 2000ft :)

[englishal]

American's believe airplanes will hit each other or the ground if they don't follow routes (Victor airways) and receive a separation service.
Victor Airways are just "advisory routes" really. A VFR pilot can bash around them, through them, in them whenever they like too.

If you file a V aw then as long as you are at the MEA then you will guarantee navaid reception and terrain clearance. However there is nothing to stop you filing GPS DCT - I once was flying back to an airport in Socal which had some convoluted routing along airways so I just asked for a DCT routing via GPS at about 12000. As the aircraft equipment was /G meaning IFR approved GPS onboard then I got it. 300mn DCT.

The difference in the USA is that all IFR is controlled and therefore requires a clearance. I actually think this is a good thing.....

[12Watt Tim]

Contacttower

Sorry, but it appears that IO540 is massively exaggerating the difficulty of the issue.

What you want to do is perfectly normal, I have done it many times. Yes you will have to leave controlled airspace, but will then be allowed back into controlled airspace if that is needed. Flying around Europe in an unpressurised aircraft in the airways is not a problem in most cases. Very occasionally there are difficult areas, where the convenient airway is too high and controllers will not clear you to leave controlled airspace, but it is very rare.

As for basic service being useless, IO540 appears to be flying on a completely different planet to the rest of us. I have heard aircraft reports that put me in conflict (estimating same VOR, same time, same altitude) and was able to find further details and spot the aircraft. I have many times been given useful information by the London Info, and I know they keep some sort of eye on the radar. It is kind of a hint when I change heading to avoid a danger area, and they check what I am doing, and let me know it is not active!The lowest levels at which one can get LTMA crossings are around FL100 plusSorry IO540, that's balls. Most of the LTMA is available from FL70 or FL80, avoiding the SIDs with FL60 limits. Never been asked to cross LTMA above FL100, although been offered better routing by going higher.

Cameltoe's experience of N864 is the same as mine, and flying up to Scotland during the week is much the same. Get a service from Warton, as there can be some military activity, and you get good warning to have a good look at the pointy aeroplanes.

If you want any specific advice CT from someone who has flown hundred of hours IFR all across Europe in unpressurised aircraft drop me a PM.

[IO540]

Victor Airways are just "advisory routes" really. A VFR pilot can bash around them, through them, in them whenever they like too.That, presumably, is because the USA has Class E from 1200ft to 17999ft, and Class E is UNcontrolled for VFR :)

The USA balances this great VFR freedom with strict enforcement (to the extent that this is possible using witnesses, i.e. near departure/arrival airports) of illegal VFR in IMC, and a readily accessible IR. This probably means there is less "VFR in IMC" over there than here.

I think it's relevant to see the US system as a whole picture. It all comes together well. But we are never likely to get such a whole package over here.

IMHO the reason why the extensive French Class E (typ. FL065-FL115) which bears a lot of similarity to the US 1200ft-17999ft Class E, works in the relaxed way it does, despite the ability to file Eurocontrol IFR routes through it, is because very few French pilots fly as high as FL065. As far as I can tell, the vast bulk of French GA activity comprises of short local inter-club outings, done mostly at low level.

Sorry, but it appears that IO540 is massively exaggerating the difficulty of the issue.I am always ready to be educated... feel free to contribute in the appropriate detail.

If you want any specific advice CT from someone who has flown hundred of hours IFR all across Europe in unpressurised aircraft drop me a PM.Gosh we must have met but I don't recognise your nickname. Is it by any chance a duplicate of another one? ;)

I don't fly a pressurised plane - couldn't afford one. But I'd like to know how you manage to find clouds which are consistently lower than the ones I find ;) The good thing about IFR (with an IR) is that the only thing one is up against is the weather - not ATC - and altitude capability is the best way to deal with it. Sure one can hack one's way in IMC for hours, with decent de-icing etc and reasonably "robust" passengers.

[12Watt Tim]

Maybe I was just lucky!

Flying at FL90 or FL100 I spent more than 80% of my time in clear air. Most of the rest I was not suffering icing, maybe 5% of the time. This was commercial charter in an aircraft cleared for moderate icing, so I flew almost regardless of en-route weather and did not work excessively hard to avoid ice. If speed dropped much due to accumulation I never had a problem descending to FL60 or FL70, and usually found all icing cleared.

I do agree with you about flying IFR OUTCAS without radar cover. I have done it many times when no radar service was available. Usually cover is available in places and times that have any amount of traffic, so the statistics are not really surprising.

[IO540]

Flying at FL90 or FL100 I spent more than 80% of my time in clear air. No doubt a conservative weather strategy (even more conservative than mine, which most pilots I know think is really conservative) would deliver VMC at FL070-100 every time. But you say you are not doing that.

If you are flying a deiced twin with radar (you don't say but if PT it would be something like that) and paid to fly (i.e. get the sack if you don't fly) then you will go anyway, and often you will find "VMC" at FL070 within a layered cloud whose tops may be FL140, but whereas you will be happy with that, and anyway have to be due to lack of oxygen for passengers, I will be working hard to stay above those tops because I am not de-iced and thus cannot afford to get snookered down below in solid IMC and collecting ice, whereas you can just do that.

I have no idea how often I am flying at say FL150, 2000ft above a solid overcast, while somebody could be flying below me at FL070 and be in VMC either between layers or below the cloud. But to me that is irrelevant because I cannot afford to get stuck down there, whereas you have no choice and I am sure that a lot of the time you will find some VMC down there. To me that is academic because to fly down there would be foolish as it would cut off my escape routes from icing.

When hacking around in Class G one can always try to descend to warmer air but on an airways flight this is an option only up to a point, before ATC gets ratty about it because one is going into some military area. One can declare a mayday or just firmly request a descent as it is obviously an emergency, and I had to do that recently (freezing rain, but in IMC and descending close to destination anyway) but one doesn't want to be hacking 500nm right across a chunk of Europe at 3000ft, with the VFR chart, wondering what obstacles are down there. So the only smart way is to be on top and stay there.

Icing is pretty statistical and I can well believe that one gets it substantially only say 10% of the time. The other day I went up in in about -8C and after some minutes collected about 5mm of mixed clear and rime. How much would I pick up after say 3 hours? I don't really want to be stuck in IMC finding out the answer. I want to be upstairs in sunshine, with 100nm vis, knowing there isn't any ice down there.

Also you don't say anything about what you fly. If you are doing 200kt TAS then you are getting an aerodynamic temp rise of 5-6 degC and that narrows the supercooled water temperature band by 1/3 to 1/2.

I think to argue that icing is rare is missing the point - for a non deiced pilot. Sure it is rare. I know a few pilots who say it is rare so why bother about it? But I could post pictures of heavily iced up wing leading edges taken by people who nearly got killed who banked on it being rare. There are many more who did get killed but there are no pics because the stuff melted before anybody got to it, or melted in the fire. That's the problem with writing a few lines attacking somebody's strategy, without posting any detail.

[Phil Space]

I think the barrier is there to prevent small,ill equipped aircraft with unskilled pilots getting in the way of the more professional well kitted aircraft.

I've just been flying here in Asia today on a 550 miles round trip where we flew at around Fl 22.(Pressurized Malibu Turboprop) Just a 2 hour jolly.

We descended on track/time from 15000 ft to have to hold for several minutes
because of poor track/timing by a C150.

Annoying to say the least when we could have parked and had a coffee while a
poorly managed ppl got his act together:ok:

[IO540]

I think the barrier is there to prevent small,ill equipped aircraft with unskilled pilots getting in the way of the more professional well kitted aircraft.

I've just been flying here in Asia today on a 550 miles round trip where we flew at around Fl 22.(Pressurized Malibu Turboprop) Just a 2 hour jolly.

We descended on track/time from 15000 ft to have to hold for several minutes
because of poor track/timing by a C150.

Annoying to say the least when we could have parked and had a coffee while a
poorly managed ppl got his act together

Could you post some detail, there? It doesn't read right to me. What "act" should he have got together? IFR traffic is normally under ATC control, etc. Also I am not aware of "barriers" "to prevent small,ill equipped aircraft with unskilled pilots getting in the way of the more professional well kitted aircraft." The weather considerations are different, of course. The regs and the pilot skills required to get an IR are just the same.

[englishal]

I think the barrier is there to prevent small,ill equipped aircraft with unskilled pilots getting in the way of the more professional well kitted aircraft.

I've just been flying here in Asia today on a 550 miles round trip where we flew at around Fl 22.(Pressurized Malibu Turboprop) Just a 2 hour jolly.

We descended on track/time from 15000 ft to have to hold for several minutes
because of poor track/timing by a C150.

Annoying to say the least when we could have parked and had a coffee while a
poorly managed ppl got his act together

Oh Skygod, we're not worthy.....:D

That is why I like the USA, everyone is equal in the eyes of the FAA and ATC - from a C150 in the "airways" to a funky Malibu Turboprop to a RJ with his climb restricted so he doesn't hit the C150...

Oh PS: My commander is going to have far better avionics in it that the last Continental 757 that I flew in from Houston to LA, which still had steam driven gauges in....

[12Watt Tim]

EnglishAl

You should see the kit on one of the aircraft I flew commercially in the airways. Best I had was a KNS80. Few self-respecting owners of an airways-equipped aircraft would get airborne that ill-equipped!

IO540

Radar? Radar? Oh, the luxury. OK, one of them had a Stormscope, but no functioning weather radar in any aircraft I flew in the airways. I have never had a problem descending to clear icing conditions, and it was always a commercial decision as ice was affecting speed more than the benefit I was getting from density altitude.

An aircraft with no de-icing kit is more vulnerable, but that just means a decision before departure and more caution after making a marginal decision. It does restrict options but only in terms of timing and having to be flexible. Most of the year it should not be a serious restriction.

[IO540]

I have never had a problem descending to clear icing conditions

You must know some new bit of physics.

Example: OAT on the ground: -2C. How will you descend to clear icing conditions? The only way to get rid of any ice picked up will be for it to sublimate, which takes an awfully long time.

What planes were you flying? Single or twin pilot?

Your routes would also be interesting. Which bit of the world?

Let's say you get a DCT BCN (Barcelona VOR) from 250nm away. How would use use a KNS80 to do that? (I can see ways but not easy). Or a DCT to some French VOR which doesn't have a co-located DME?

[Islander2]

12Watt Tim said:
I have never had a problem descending to clear icing conditionsThen we can only assume that you never flew in European winters or over mountainous terrain!

Sorry to say, but there is the potential here for you to dangerously mislead the inexperienced GA IFR pilot into believing that pre-flight icing decisions are unimportant.

[12Watt Tim]

IO540

Single-crew, various piston twins. Didn't answer about the speed, but generally between 160 and 180 kts TAS.

Try it in an aircraft cleared for known icing. Most of the time ice will clear somewhere below -2 degrees. Most of the time even below zero in cloud you won't pick up ice. I know what the books say, I know plenty about the theory, but as always with science there is nothing to beat a test, and I've been there and seen it.

Remember also that if the surface temperature is that low then the temperature at FL100 will often be so low that icing will not be that bad.Which bit of the world? Europe. Mostly western and northern, but some into southern and central Europe.Let's say you get a DCT BCN (Barcelona VOR) from 250nm away. How would use use a KNS80 to do that? (I can see ways but not easy)You ever actually do a comms exam, and learn the expression "unable"? You never have to accept a clearance. However I was pretty good at it, and would usually be able to accept. Various methods, easiest was to use a nearby navaid to define BCN as a waypoint. Works with Brecon too!

Islander2Then we can only assume that you never flew in European winters or over mountainous terrain! You would assume incorrectly. I found icing to be exceedingly rare at FL60, rare at FL90 and 100 which was my more usual territory.

[Islander2]

You would assume incorrectly. I found icing to be exceedingly rare at FL60, rare at FL90 and 100 which was my more usual territory.Then for inexplicable reasons, our experiences do not coincide!

[12Watt Tim]

If you were flying Islanders I suspect you were flying rather lower than I was. I would only go lower to clear ice I was suffering higher up, but at FL100 I was rarely in cloud.

[IO540]

12Watt Tim should go for the Nobel prize in physics.

But yes one can get away with a lot if flying a substantial deiced plane, especially at 160-180kt.

And one gets away with a lot anyway, due to the statistical nature of weather. Then..... something comes along and bites you :)

You ever actually do a comms exam, and learn the expression "unable"? You never have to accept a clearance.

No, never heard of it :)

Have you heard of BRNAV and FL095? Your flight would have been illegal at

FL100

if unable to do RNAV.

[S-Works]

You would assume incorrectly. I found icing to be exceedingly rare at FL60, rare at FL90 and 100 which was my more usual territory.

Then what exactly were you flying a rocket or MS FS?

I have just flown to Spain and at 18,000ft it was MINUS 35c and I can tell you as we were climbing through all that cloud we were icing and that was at Turboprop climb rates. I have iced this morning flying, started picking it up around 6,000ft and not stopped until clear over the top.

[IO540]

wonder whether it is a cause or consequence or both, of the lack of a Class E system, that fewer smaller planes fly in IMC. I think that is just the way light GA is. The vast majority is VFR-only and I really mean VMC-only; pilots who are s:mad:t scared of entering a cloud (which, as an old hand might point out, is just as well :) ).

There is a small hard core who do fly in IMC; these comprise of pilots who have an IMC Rating, or an IR, or neither (but probably did have one or the other but it has lapsed but they still have what they judge are the skills and an appropriate equipment).

I am pretty convinced the whole European private IR population is of the order of 2k pilots, plus probably a few k IMC-R holders in the UK, and if you work on say 100hrs/year (which itself is about 5x the UK VFR pilot annual average so I am being awfully generous) is a really small chance of one being airborne anywhere near your bit of the cloud.

On top of that, pilots who fly in IMC are for the most part not cowboys and they are going A-B and not for the view (obviously there is no view) so will probably not be flying at 700ft AGL. They will be at a few thousand feet where there is close to zero VFR (VMC) traffic anyway.

The statistics support this, with zero mid-airs in IMC in living memory.

I'm starting to buy-in to the assumption that flying IFR in IMC in Class G will probably be fine for now, due to lower levels of traffic. But until a few mid-airs happen, probably nothing will change.I don't think that the (nonexistent) mid-air data supports any belief that one of them is going to happen anytime soon.

The existence of Class A airways suggests Big Sky Separation doesn't always work for higher density, faster moving, mainly commercial traffic. As the old joke goes, ATC pack them in tight into narrow corridors and then work hard to stop them hitting each other :)

That's just the way the aviation world has developed over the decades. It probably came from navaids, which gave rise to airways (VORs are the perfect "old" solution for flying long legs, but they work only if you are flying between two of them).

The airways in turn gave rise to controlled airspace, and that in turn has been kept tight by all kinds of other interests: the military, GA, the need to provide an expensive radar service in CAS thus creating an incentive to keep it tight.

With separation offered if you have a plane which flies high enough to do it in, and only on a best effort basis to everything else which flies beneath, this setup contrasts greatly to the rather zealous "health and safety" culture which exists on the surface.Sure.

While a risk still remains, I guess the plan for now is to climb to VMC on top and enjoy the viewIndeed :)

The catch is that UK CAS is generally too low to enable one to do that unless they have an IR and are on a full IFR flight...

Emotionally, the risk is hard to accept, because it means a virtually certain death if your number comes up. I can't suggest a way to get one's head around it, other than (again) to consider the stats.

The midair stats tell you very powerfully how to get yourself killed in a mid-air:

- fly below 1000ft (the best way)
- fly in areas where traffic is packed tight (the circuit)

Some traditional ideas, e.g. not flying across VORs but flying a shortcut instead, are not supported by the stats. I guess it may be because so few pilots are radio navigating and those who are are not going to be flying low, because they planned the MSA and are sticking to it.

[Pace]

10540

I really must stress it is not just a few piper warriors bombing around in IMC OCAS.

Fly airways to LondonDerry in Northern Ireland and you will be met with the fact that once away from Belfast you are OCAS and soon after with NO radar coverage.

I can well remember flying in there solid IMC from 12000 feet on down to a 700 foot Cloudbase there were four of us all at different levels in the hold while the first was on finals after flying the pilot interpreted approach.

The rest of us were all talking via the controller to each other checking our revelant positions. Below me was a 737, above me was a passenger carrying turboprop.

I take your point that the big sky principal appears to work. I take your point that the worse the weather the less the traffic and the more experienced the pilots (usually :)

Because it hasnt happened doesnt mean it wont happen and then it will be CAS nearly everywhere after the media have a field day.

Pace

[IO540]

Agreed; there is also the Islander type traffic there which cannot go high because they are unpressurised and have no oxygen. In fact some of these get up to all sorts of things like scud running across the Channel at 400 ft :)

I don't think that an OCAS midair would bring a lot of CAS. I think it would possibly force the CAA to ban OCAS public transport ops though. Whether such a move would be successful I don't know because it would instantly terminate a lot of AOC/PT ops which pay fat (think "737-fat") AOC fees to the CAA..... The CAA has been extremely reluctant to take action against anybody who pays it big fees.

So nothing would probably happen.

I don't think widespread CAS would happen because of objections from the military, and what voice GA has (not a lot), and the cost of providing a radar service all over it, and the service would have to be provided because one could legitimately file IFR routings anywhere within it...

A possible outcome is a huge TMZ but that wouldn't bother anybody flying at the relevant levels.

It might even have another positive outcome, like forcing EASA's hand in relaxing its dead slow certification process for ADS-B which would pave the way to cheap TCAS for everybody.

[IO540]

I also don't know why GA will object to CAS if it means greater safety for everyone else.

Because (a) the safety is 99% illusory and (b) there is no assurance of getting entry and (c) nobody wants to pay for the radar service to the traffic flying over a larger area (any perceived safety gain comes from traffic separation).

As far as GA is concerned, the present operation of most CAS (below Class A) is an abuse of the ICAO airspace classification, especially as quite often there is no obvious reason for the denial (I am talking about Europe, of which parts are "the 3rd world"; not UK specifically)

As far as ATC are concerned, denial of a transit is what CAS is about :) If you did not have that option, there is no point in having it.

The thing is that different systems fit together differently with that country's practice elsewhere. For example, the UK's widespread Class G fits well with the privatised ATC (which doesn't want to provide a service to anybody unless it's mandatory) and with the ability to fly IFR non-radio. The French (and American) extensive Class E airspace works well with their centrally funded radar services.

We are not going to get a US-style Class E and radar services (incl radar controllers covering non-towered airport GPS approaches) here unless ATC is re-nationalised; simple as that.

[Pace]

10540

the trouble with the theory of its never happened before so never will is a dangerous policy to take.

Take what happened with the gun laws.

The policy that it nver happened before does not equal it will not happen.
A lot in our society revolves around liability and duty of care.

To have a lump of airspace where a 737 is descending in cloud with 200 pax OCAS and mixing it with Gliders in cloud, microlights hang gliders etc is really a game of Russian roulette.

When the media hit on the reality of what is allowed to go on the Sh+t really will hit the fan especially when it reported than non instrument trained pilots with non instrument equipt aircraft and no transponders had a collision with a 737 ????

IFR traffic will want CAS from takeoff to touchdown. Look what happened to the airspace around Robin Hood Donaster there are plenty of airfields like that.
I am afraid that light GA does not figure as important when it comes to airspace distribution and will be relegated to airspace that no one wants.

Pace

[Pace]

Fuzzy69

I am not taking a holier than thou attitude as I have and do operate OCAS in anything from a twin up to business jets.

In the past I have used an IMCR in anger and sat there with no radar coverage in solid IMC now its an ATP.

Up until my near miss with a glider in imc I too trusted the big sky theory. Now I am slightly more aware.

I must admit to relaxing the higher you climb OCAS especially in the business jets as you are travelling a lot faster.

I must admit in another thread I was surprised at the lack of support for compulsory use of transponders with altitude in IMC and fear that unless we govern ourselves someone in the future will do it for us.

Pace

[IO540]

Sorry IO540, what do you mean by this?In the context of IMC mid-airs, and CAS, and radar services, etc.

I thought CAS was established to provide separation to traffic. Separation within CAS is done by radar, or occassionally (e.g. over Africa) procedurally. But this is only within CAS. OCAS, traffic can do what it likes, including flying into CAS...

Transit ought be granted where traffic conditions allow.I agree :)

I also agree (obviously) that a widespread radar service OCAS should be provided. The problem is that you have to do this within today's privatised ATC system, so it isn't going to happen - ever.

You can achieve TCAS today. The system costs £10k-£20k depending on details, and usefully shows up Mode C transponding traffic. The plane needs to be dismantled to a large degree to install most of the antennae and to move all existing antennae off elsewhere (seats out, trims off, etc). 2-3 weeks at the avionics shop and that assumes they are competent. I looked into this a while ago; most avionics shops could not be bothered to even quote on it, and I decided that the upheaval was not worth it since many people in aircraft maintenance cannot even refit trims properly.

As regards hitting an airliner, any large PT aircraft has mandatory TCAS already so if you always fly with Mode C on (which you obviously should) they will be able to avoid you using this last-resort means.

Given currently mandatory TCAS on CAT, I think the whole risk of a GA-on-CAT mid-air is with nontransponding (or Mode A transponding) GA, which has a simple technological solution: make Mode C mandatory :) Now, how long a thread do you want on that one?

[TALLOWAY]

If we're paying taxes for the aviation sector, it sounds fair that it should be spent on developing aviation infrastructure, such as a Class-E system, free landing fees, and cheaper CAA fees.

If only that's how it worked in the UK :{ but the Government pays not a penny from it's aviation taxes to anything within aviation. The CAA and NATS, although different types of company (one wholly government, the other part government- part private), are both expected to pay their own way and cost the government nothing. Indeed Nu Labour will probably sell off a good portion of their share in NATS come the end of January. They don't care about the public and the infrastructure we deserve. They care about lining their pockets and trying to patch up their shocking economic policies.

As a further example of their greed, they are even looking to charge frequency useage in the aviation band, regardless of the fact that it is primarily for air safety.

:mad::mad::mad: politicians. I'd shoot every last one of them.

[debiassi]

Remember also that if the surface temperature is that low then the temperature at FL100 will often be so low that icing will not be that bad.

Not quite sure what your saying here? Do you mean if its cold at the surface then ice at fl100 wont accrete on an airframe???
Lets say its plus 2 at the surface and ISA exists so lets round it up from 1.98 to 2 degrees x 10000ft = -18c Lets then add a cluster of cumuliform clouds with vertical development from 3000ft to fl110. At -18 and when considering that the majority of moisture would be towards the top of the clouds, then I would say that icing at fl100 would be a very serious threat.

[CMS]

At -18 and when considering that the majority of moisture would be towards the top of the clouds, then I would say that icing at fl100 would be a very serious threat.I was taught, when I did my US IFR, that airframe icing could only occur between 0°C and -10°C. At -18° icing should not occur.

Was this wrong? Or is it different in the UK?

Cliff.

[A2B Ferry]

I was taught, when I did my US IFR, that airframe icing could only occur between 0°C and -10°C. At -18° icing should not occur.

Was this wrong? Or is it different in the UK?

You were taught wrong but fortunately all is not lost. Ice will usually attach to an airframe in the temperature range of +2 through -20c. Although it is possible for icing outside this temp range, it is unlikely although the only physical limiting factor number is -40c and there must be visible moisture in the air in the form of cloud, freezing rain supercooled liquid etc.

[debiassi]

I was taught, when I did my US IFR, that airframe icing could only occur between 0°C and -10°C. At -18° icing should not occur.

Was this wrong? Or is it different in the UK?

He definately steered you wrong on that one Cliff. The temperature range for icing is the same anywhere on the planet and the numbers for operational terms are positive 2 to negative 20. The study theory always states that icing is possible on the colder side of the scale with negative 40 as a physical limiting factor but outside of the +2-20 temp range, icing is unlikely. I have seen some theory that state zero through -20. May be its something to do with the wind chill factor on the leading edges unless of course your flying at concord speed in which case heat is generated.

[mad_jock]

Well there must be something weird going on over the Cairngorms then. Because I have had ice shedding off the props at -30 and building on the wings.

Why would you want to muck about with icing anyway?

Its not just "look at that" we have picked up a bit of ice.

When it starts building fast it really does lump on. In under a min you can boots banging away ice clattering off the hull off the props airframe vibrating like a bugger. I avoid it if I can and I have over 2000 shp to play with, pneumatic boots and prop heaters. I have still had my arse twitch a couple of times flying around the highlands due to icing and I know I am not alone.

[debiassi]

Well thats relatively easy to explain really. If you have picked up ice on the way up and your flying into colder temperatures then its unlikely the ice you picked up is going to sublimate in a hurry. Simple as that really, not sure of the point you attempt to make?

Well there must be something weird going on over the Cairngorms then. Because I have had ice shedding off the props at -30 and building on the wings.

[mad_jock]

That ice can form on the air frame at -30 when you enter cloud.

The profile of the flight was up the old W3D at FL180 remained high and when started dropping the height off for the direct arrival within about 2 mins we had about 1 cm of ice on the wings and ice shedding off the props. When we landed we managed to get a 1ft high for want of a better word vase off the spinner about 1 cm thick.

When we departed it was CAVOK down south, no ice in the climb.

If the de-iceing gear isn't working the plane gets grounded if there is cloud in the sky and the temp is below 5 degs above MSA. And yet it appears to me that some people are saying its ok to play a numbers game flying in cloud with no de-icing gear? Its utter madness.

[debiassi]

That ice can form on the air frame at -30 when you enter cloud.Then i fail to see your point as it certainly doesnt contradict anything I have put in text. i stated negative 40 as a physically limiting factor. I also stated that to accrete icing outside the temp range of +2-20 is unlikely. Thats the figures NASA give and you would think they would know. Its unlikely that an individual will win the lottery jackpot but of course it happens regularly. There are parameters regarding icing where it will be found on a regular basis. There are parameters where you will find it infrequently and there are parameters where you will never find it. As a pilot who flies IFR, its important to know and understand these parameters. with ice accretions at -30, these accretions will be milky white and uniform and not the more hazzardous formations that you will find closer to the freezing point. If someone is advocating flying in icing conditions for fun, it certainly isnt me so maybe you should revisit what I have written as every part of it holds water.

[mad_jock]

It was the operationally that I was worried about. And I wouldn't say its unlikely unless unlikely means 2-3 times a year for a 400 hour a year regional airline pilot. As I said it could be a regional effect coming from the lift of the Cairngorms producing a none NASA air mass of super cooled water.

The Moray basin and surrounding area have been the subject of several AAIB reports of aircraft turning into ice cubes.

And the treatment of Icing doesn't need to be complicated. If you not equipped for it don't go anywhere near it. And if you are equipped for it and you start picking it up get the hell out of it as quickly as possible.

H'mm maybe the Scottish "don't :mad: with the wx" attitude is the reason why there are remarkably few wx related accidents for locals and its the visitors which seem to get their bums bitten and get into trouble?

[debiassi]

Yeh course, I forgot America is as flat as Holland. Im sure air masses that are forced to cool as they are lifted around the mountain ranges in the western hemisphere act in a similar way as they do around the cairngormes or are you actually suggesting that SLD is more likely to be found there in some unique phenomenon. I always say a little bit of knowledge can be a dangerous thing. you seem to have scrutinized what I have replied and for some strange reason tried to find fault in it. A Pilot's Guide to In-Flight Icing - Web Version (http://aircrafticing.grc.nasa.gov/courses/inflight_icing/main.html)
This is what NASA say verbatim.

Since in flight icing is most likely to occur between +2 and -20, you will generally want to knowat which altitudes you will find air temperatures that are outside this range. You can use this information to plan the flight to limit your exposure to icing conditions and build an exit strategy for every point along your route.
There is a lot of very good information I have quoted concerning icing so maybe its better to leave that information for those who may benefit from it rather than nit picking. I certainly havent posted anything that isnt well intended and with regard to SLD, unless I am very much mistaken and I do stand to be corrected but I am not aware of anything out there that is certified to fly in it and an immediate exit should be made. I do know that aircraft certification to obtain FIKI doesnt go anywhere close to supercooled liquid as part of the testing regime under FAA. I am sure everyone would agree that if encountered you get out of it because flight in supercooled liquid is considered a severe icing encounter.

[mad_jock]

All I know is what I have experienced flying in the area. Which I might add covers nearly 25% of UK airspace I will admit with very little traffic compared to the south.

I have a very very healthy respect for the mountains of Scotland. I walked most most of them, flown through most of them. They have been part of my life both as a child and as an adult

The wx patterns are are notorious for changing very quickly and quite often producing wx which has not been forecast. There are one or 2 old men of the hill who do their own forecasts which get it right most of the time more so than the met office. Some very experienced climbers come to grief every year because of it.

And yes I have to review not only the nasa winter ops material but also the BAe systems winter ops material which in some ways is better presented and more targeted for prop aircraft every year. I have also flown with an ex BAe empire school trained test pilot in fact the one that signed off one of my current types. Shall we say I learn more in those 3 days flying in icing than the previous 6 years of flying.

And after Buffalo shall we say that the winter ops had another revision. My last sim sessions tail stalls featured in various phases of flight and its OK reading about these things but to experience them is a whole different kettle of fish. When the last stage of flap goes in and everything goes suddenly wrong even when its a pre briefed exercise its hard work.

You can call it nit picking if you like my point is that if a light twin decides that its OK to fly up W3D or direct Angus to INV at FL100 IMC because the temps are -20 or below so its unlikely to get ice. They very possibly are going to get a very nasty bum twitcher at the best. I grant you its none airways but its high MSA's poor radar cover and not alot of options if things go wrong.

Every year there are incidents up North so many we don't normally get to hear about them. The most recent that comes to mind was the experienced FAA IR ferry pilot who came unstuck on the west coast and had to get escorted into Prestwick by SAR. Several times a year a fleet of helibuses appears all on fuel maydays because Aberdeen has been haar'd out un-forcast.

If we are lucky the chap from Scottish Info will come along and give some more concrete facts on the number of incidents. I am more than happy if I am being a big girls blouse and the real number of incidents isn't as bad as I make out.

I just hope our debate increases the exposure to pilots of the nature of flying up north.

[CMS]

Thank you for those most informative posts. I was clearly misremembering. I'm rather glad I found out about the 2° to -20° while sitting at the computer rather than at 10,000'.
Having now searched on the subject this PDF (http://redirectingat.com/?id=42X487496&url=http%3A%2F%2Fwww.airweb.faa.gov%2FRegulatory_and_Guidanc e_Library%2FrgAdvisoryCircular.nsf%2F0%2F451296dbdf212c81862 569e70077c8f9%2F%24FILE%2FAC91-51A.pdf) is very useful. Amazingly, I actually found it on PPPRuNe (http://www.pprune.org/tech-log/66205-useful-website-document-references.html) in a whole bunch of resources I didn't know were here.

[A2B Ferry]

Some interesting material. The NASA course offers a really in depth insight to both airframe icing and ground icing in 2 seperate courses and thankfully theyre both free, actually I may just list these under a new post to try and get better exposure as especially in the UK, its a shame that more material like this isnt readilly available. I regularly have to deal with adverse and cold weather operations (nature of the business) and its great to know that icing bands in stratiform clouds are usually no more than 2 to 3000 ft thick and if encountered, either a climb or descent of 3000ft will USUALLY take you out of icing conditions. Icing in cumuliform cloud may span several thousands of feet but cumuliform cloud is USUALLY no more than 5 or 6 miles wide so a lateral change in direction is the preferred exit method. It has been accepted and actually in my belief is widely understood that the more hazardous formations accrete in the warmer temps closer to the freezin point. There are of course other things to consider and it is very good practice for these other factors to be considered on the ground as part of pre flight planning. It amazes me how little is actually taught subject in either the UK syllabus and even the FAA IR syllabus only touched upon it briefly although enough to make you realize you needed to research the subject further. I know a lot of UK IMC holders who get there ticket and go cloud chasing and I am not being judgemental here as I used to be one of them in my younger days. I used to think it was great fun showing off my skills flying in cloud. I know when I used to do so, I had very little real understanding of what lurked within those fluffy white/grey picture postcards. If I knew then what I know now???
A coating of ice similar to medium grain sandpaper can increase drag by 25%!!! increasing stall speed, raising the angle of attack to maintain the same airspeed etc etc. An exposure to severe icing can render your aerodynamic properties redundant in minutes!!! surely this is a topic that needs more exposure, even if you only come into icing conditions very rarely, a greater understanding of what lies within can only serve to prevent incident.
Aircraft Icing Training - Courses (http://aircrafticing.grc.nasa.gov/courses.html)

Check it out, it is a fantastic resource!!!!

[IO540]

One needs to be clearer about the +2C figure mentioned above.

You will absolutely not get icing if the airframe is at +2C. It can't happen. Water will be liquid at +2C...

What can happen, in fast planes, is that parts of the airflow whose static air temperature (SAT) may be say +2C will cool below 0C as they flow over bits of the airframe.

But in GA terms one needs to be moving quite fast. As an example, at FL100, 150kt TAS (130kt IAS), ISA (i.e. -5C) according to my Jepp CR5 there is an aerodynamic temp rise of 3C. Not a lot, but it would take some doing with SAT=+2C to get parts of the airflow to go below zero.

I have an accurate OAT gauge (two in fact) checked against a PT100 thermometer accurate to 0.1C, and I have never seen any ice anywhere above 0C. The place one might expect a temperature drop would be the top of the wing, where there is a pressure drop, and I can see that part.

So I think that, in GA terms, icing at +2C SAT is a myth.

But the OAT probe doesn't read the SAT; not in flight. It actually reads something similar to TAT (total air temperature - the temperature of the airflow heated by compression) because the probe is sticking out into the airflow.

At the above 150kt example, a probe reading +2C means the SAT might be -1C and airframe icing is then possible because any water droplets would be supercooled. But will you get icing? Not likely, since nearly all of the airframe will be heated by the compressed airflow and will be at a temperature not that different to the OAT probe reading. One cannot get ice accretion on an airframe component whose temperature is warmer than 0C.

I have never seen any ice above 0C as indicated on the OAT probe.

The pitot probe is a bit different. For some reason (which I don't understand) one can get "stuff" building up inside it anytime below about +5C.

A coating of ice similar to medium grain sandpaper can increase drag by 25%!!!

I am sure it does but again the effect varies. The other day I drilled a long hole through some stratus at -5C (at FL074; the 0C level was about 3000ft so this was perfectly safe, over the sea). I picked up 3-4mm of mixed clear and rime within seconds - all over the wing and elevator leading edges. I've had a bit more than this in the past ;) but this time I watched the IAS (~140kt) very carefully and if there was a drop it was less than 1-2kt.

May be very different on some laminar-flow "plastic planes" though.

[mm_flynn]

A coating of ice similar to medium grain sandpaper can increase drag by 25%!!! increasing stall speed, raising the angle of attack to maintain the same airspeed etc etc.
This phenomenon is normally associated with 'ground icing'. Ice in flight normally accumulates predominantly at stagnation points (hence why boots cover such a small part of the wing). However, ground ice/frost covers the whole upper surface of the airfoil. This extra 'friction' appears to significantly impair the large volume circulation (and resulting high speed flow across the top of the wing), reducing the lift for any given angle of attack. On departure, this increase the stall speed/reduce the lift such that the aircraft stalls (as demonstrated by several jet departure accidents in the US and UK).

[A2B Ferry]

This phenomenon is normally associated with 'ground icing'. Ice in flight normally accumulates predominantly at stagnation points (hence why boots cover such a small part of the wing)

Have you ever heard of runback icing?? Ever heard of inoperative boots?? Ever heard of non de iced aircraft inadvertently being in icing conditions. Of course there are loads of variables but the quote I used actually came from the NASA in flight icing course and is also mentioned in the ground icing course.

One needs to be clearer about the +2C figure mentioned above.

You will absolutely not get icing if the airframe is at +2C. It can't happen. Water will be liquid at +2C...

I fully agree, maybe I didnt make that point clear enough. Moisture can actually exist as supercooled liquid until approximately -40c which is the physical theoretical limit. Contaminates in the atmoshphere however set the practical limit to approximately -20c. Ice can accrete on an aircraft even when the SAT is above 0c if the aircraft surface is below freezing. This situation can occur when the aircraft descends from subfreezing temperatures. It can also occur where the local temperature is reduced to below freezing due to local flow acceleration.
I think were in agreement.
:ok:

[A2B Ferry]

This phenomenon is normally associated with 'ground icing'Just to quote from the in flight icing syllabus, Aerodynamics of icing. Performance Effects.

Tests conducted at NASA Glenn research center on several modern airofoils demonstrated that in some instances, exposure to clear icing for a period of two minutes could double the drag, reduce maximum lift by 25-30% and reduce the critical angle of attack by 8 degrees (which would correspond to a substantially higher stall speed)

[Captain Stable]

the 0C level was about 3000ft so this was perfectly safe,IO540, this comment may lead to a misunderstanding on the part of others. As I am sure you realise, but others may not, you are only safe if you commence a descent immediately you see any icing. If you permit any ice to build up on any aerodynamic surfaces, there is a significant danger that the stall speed will rise above the level of the power plant(s) to produce enough thrust to produce enough lift to over come it, leading to an uncontrollable stall. If the 0 degC level is at only 3,000', there will not be enough time for enough ice to melt between stalled descent through 3,000' and impacting the ground.

Sorry to be pedantic - but as various people have pointed out, ice is not dangerous provided people understand the dangers and act on all information available.

[IO540]

you are only safe if you commence a descent immediately you see any icing

That is clearly not the best advice either. Why should one descend immediately upon any icing? One could pop into a bit of cloud, whose inside is -3C, during a climb to FL150 for a flight which will be wholly VMC in sunshine, and one will probably collect a little bit of ice - 1-2mm perhaps. Why descend? The stuff will sublimate off before long.

Your advice would make it impossible to fly IFR in the winter, or anytime of the year in N Europe at airway levels, in anything less than "heavy iron". It's just like saying one must not do a flight if there is any IMC forecast below 0C.

An inch or three of ice is something else, or less depending on the aircraft.

[Captain Stable]

I wouldn't say "anything less than heavy iron". I would, however, say "in anything not cleared for known icing".

It is also very important that people are aware of the capabilities of their particular aircraft. Even, of course, different airframes of the same type can have markedly different capability, so it is not enough for someone to say to themselves that "some bloke on PPRuNe has a PAnn and he's flown in these conditions so it's safe for me as well", unaware that that bloke on PPRuNe has rather more anti- or de-ice equipment on his PAnn....

Sorry to be pedantic, but as a former mod here I'm very much aware that there are people viewing these threads who have much less ability or experience than you or I, and I tend to err on the side of caution when posting here on anything safety-related.

[A2B Ferry]

Captain Stable, I think IO540 has you on this one sir. His point is a very valid one. It is possible to pick ice up in a very thin layer of cloud. That layer may be say 500ft thick and you could pick up trace or even light icing climbing through it but you would be in bright blue and sunshine once you reach VMC on top. This certainly wouldnt be considered dangerouse by any stretch of the imagination. I refer back to planning which should of course always be done as part of the pre flight and where there is any risk of an icing encounter, then full and comprehensive exit strategies need to be addressed when determining a go / no go decision. There are lots of aircraft out there that are more than capable of flying through a thin band of cloud to reach known improving weather and these may have anti ice/de ice utilities such as alternate static source, alternate air, hot prop, a turbo charger to help you climb through it quicker?
He is also right that if that was the case there would be very few actual GA flights taking place, especially in the UK. Have a look at the link I posted earlier, I am sure you will get some great info from it.