Flying Airways in the UK?

[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 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
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 is very useful. Amazingly, I actually found it on PPPRuNe 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

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]

Originally Posted by A2B Ferry

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.

[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.