Cold and Icing Conditions Testing

[leonard17F]

Hi All !

If you had to perform Extreme Cold and Icing Conditions Testing for a biz-jet:
- In the Northern hemishpere:
when would be the latest/warmest possible period in winter ? March, April
when would be the earliest possible period in late autumn or winter ? November, December ?
where would you go ? Iqualuit, Resolute, Narsasuaq, etc..or....Siberia, Alaska ?
- Are there suitable locations in the Southern Hemisphere ?

Thanks a lot for your inputs !

[Genghis the Engineer]

The concept of "severe cold weather testing" seems a bit odd. A business jet is presumably certified to part 23 - in all likelihood a parallel EASA CS.23 and FAA FAR-23 certification. This will cover specific cold weather and (depending upon specific clearances required) icing conditions but I wouldn't anticipate any special requirements above that.


Ability to operate in cold conditions tends to fall into three parts:

(1) startups and system operability after cold soak,
(2) ground handling in snow/ice
(3) flight in known icing conditions.

The three are quite separate, and none necessarily need you to mount an expensive detachment to some dreadful spot north of the arctic circle - although the second will probably take you to somewhere like Alaska or northern Canada for some decently contaminated runways to play on.

Part (1) can be done, cold enough for certification purposes at somewhere like Goose Bay in winter, but you'll get a lot more control taking the aircraft to a suitable test chamber - which probably means either Boscombe Down or Edwards, without the variability of waiting for exactly the right cold conditions (Sod's law say's you'll move your test team to the arctic for a month only to hit a heatwave of -15°C otherwise). Typically you're looking for around -46°C for global certification (this is from memory, I'm in the wrong office for the books on that this week.)

Part (2) isn't really about cold, it's about surface friction and surface condition. There's a really good paper on this in the 2008 SETP annual procedings called "Stopping the Raptor on Ice", which is better than anything else I've ever seen in explaining how this type of testing is done.

Part (3) Needs icing conditions, and the atmosphere being what it is, the best direction to look for that is up, rather than north or south. Pilatus have done a lot of severe icing work flying over Switzerland, but equally a business jet with reasonable altitude performance can probably fly into moderate or even severe icing conditions over the tropics - for example out of Darwin (where the Australian Met Bureau have a hugh research weather radar facility called Berrimah - probably the best in the world, conveniently close to regularly convective storms) , or into the ITCZ.

G

[Daniel_11000]

Iceland in may, together with a good on-board system to detect /measure ice accretion ; gives the possibility to test and verify ice shapes and accretion without the need to fly into or close to cb. A good ice certification expert is of paramount importance - then follow his instruction for staying inside the icing area and altitude - lot of ice in smooth weather !

[FlightTester]

The McKinley Climatic Lab facility at Eglin AFB. We use them for hot and cold weather testing, where we don't have a requirement to fly immediately after the soak. Running engines, APU's etc in the chamber is possible up to TOP.

If we need to carry out a cold soak followed immediately by a flight, we generally resort to the Frobisher, Resolute Bay, Iqaluit option.

http://www.aiaa.org/tc/gt/facility_database/Climatic2008.pdf

Edit: The chamber also has the capibility to generate snow and ice for accretion testing.

[MarkMcC]

In Canada you can get excellent support for all the testing that has been mentioned through the Canadian Flight Test Centre in Cold Lake, AB. Jan-Mar temperatures below -30 and excellent support facilities.

I have run certification testing for anti-icing fluid out of Winnipeg Intl in January. Major airport facilities, pretty much guaranteed sub -25 temperatures, and good logistical support. In this case we needed a week or more below the fluid's LOUT of -28.

Iqaluit is also possible, although more $$$ and a bit remote.

[leonard17F]

Hi All,
Firstly thanks a lot to those who replied so far and sorry I have not responsed earlier....
I know it has been year, but the subject came back (of course....)

For example, I know that the the F7X did its ICING campaign in MAY ('06) in ... Europe, i.e. NOT in winter in Canada, which by the way makes lots of sense.... You look for some active CB's at FL200, and you get into them, right?

Any inputs/comments on that ?

Thx a mil,
Leonard

[safetypee]

You probably need to consider two separate locations.
Northern Canada has the ‘cold’ and probably reasonable snow for the ground handling aspects.
However for in-flight icing tests you need water and warmer conditions. The Southern Alps and Switzerland has been suggested, but this may be complicated by civil traffic. Alternatively Iceland / Greenland could be considered, but may lack facilities or offer reasonable continuity of weather conditions.
IIRC Boeing uses the West coast of Canada which may have advantages of a range of airports (Seattle to Alaska) and transit to other parts of N America as conditions change.

You look for some active CB's at FL200, and you get into them, right?
Not necessarily so !
Good conditions for certification icing are often found in stratoform clouds and these would satisfy the ‘continuous’ icing aspects. The ‘high rate’ requirements are related to Cbs, but testing in Cbs is not advisable due to the ‘unknown’ and variability of such clouds.
The rules have changed since I flew icing tests, so the mix of ice shape and real ice flying may be different, but it was possible to complete a full programme in layered clouds given their availability and a range of temperature / water content, together with a range of ice 'shape' flying.

[twochai]

In the lee of one of the Great Lakes works well during fall or winter, when an active low pressure area is moving quickly across the continent. Follow the strong system east from Lake Superior to Montreal and you're certain to find high moisture content. (Read E.K. Gann, et al, about flying the mail routes across the northern border!).

Alternatively, one can always find 'good' ice immediately off the east coast of Newfoundland (Gander, or St Johns are both good bases) in stratus cloud conditions which are very common in the 1,000' to 3,000' range and predictable in the right winter conditions.

Then, go do crosswind landing limit expansion when the system passes over Keflavik. Great winds, long, wide runways with no obstructions and no topographic features to disturb the strong westerly flow across the ocean.

[sycamore]

Leonard, I`d go along with Ghenghis, S-p and Twochai;I spent several winters in Canada doing helicopter icing trials between `69-75`,using the facilities at NRC in Ottawa,and home facilities such as `blower `tunnels,cold chambers ,etc,. As said ,things have moved on with better facilities etc.Before venturing into IMC for real icing we waited for a good stable airmass to give `fairly` uniform moisture content at reasonable `helicopter` altitudes,to build-up confidence in the instrumentation,the aircraft systems, Air Traffic (who thought we were `nuts`),and the crew,particularly if you ended up losing an engine,or the ice would`nt shed off.I know helos are `different`,but such trials are not taken lightly,either F/W or Rotary,so one also needs a good range of diversions as well.
You could also consider the use of an airborne `tanker`,for those early days,blue skies, which can also give you excellent info on water droplet size,flow rates,etc. As stated ,don`t go looking for Cbs,you`ll end up with tears....
Google `aircraft icing tankers..`

[leonard17F]

Gentlemen,

Thanks a lot for your great inputs.
Seems like we will conduct the testing in the US this winter.
Watch this space.
Leo.

[fcuneo]

If you need additional support do not hesitate to contact me. We have a team of DER, Test pilots and icing experts.

[leonard17F]

Dear fcuneo and all,

It seems that my company has already closed a contract with a company based in Colorado.
But let's keep in touch (possibly regarding the DER?)...
Leo.

[john_tullamarine]

Sideline thought (don't think it's been mentioned above) - fuel icing (waxing) in cold soak conditions at cruise.

Recent instances which come to mind -

(a) airline B777 over the pole into the UK with a failure to spin up on short final.

(b) corporate turboprop Aust-NZ with a fuel tank transfer restriction in cruise - a jumpseating pilot with relevant prior experience diagnosed the symptoms correctly and saved the day on that occasion.

.. I'm sure that there have been a variety of others, of which I am not aware, in recent years.

[galaxy flyer]

Genghis the Engineer

Just a small correction, business jets are cert'd to FAR/JAR 25 standards, except for the smallest ones--Mustang, Eclipse, Phenom 100

GF

[goldfish85]

In my experience, I've flown in three main locations for icing: (1) the Lake Erie region where NASA has their icing lab; the North Atlantic; and Punta Arenas in Chile. I haven't done icing work in the Seattle area, but it should be very suitable.

Of the three I've operated at, Punta Arenas is probably the best for icing and certainly the worst for logistics. I'd probably only consider Punta Arenas if you were constrained to July-August. Otherwise, I'd choose Seattle or Cleveland.


Goldfish

[MarkMcC]

I'd choose Seattle just for the coffee :):):) An incredibly important consideration in any transport certification test program!!

[johns7022]

Some of it is done in Oregon, around Medford to Salem, going from 50 degrees through the clouds over the Cascades pretty guarantees upslope icing....if you keep climbing into wet clouds trying to get pushed over some mountains, your gonna get some ice..

The ATR went through flying around with some tanker in front dumping water at them around the freezing level..

Personally If was going to do it, I would find a sub freezing ambient condition with a wind tunnel,cold soak the plane overnight,, blow on it for a half hour to get everything cold and sticky........ get some fire hoses....that should do it....

[sodepdotvn]

Thanks

.

[Genghis the Engineer]

Personally If was going to do it, I would find a sub freezing ambient condition with a wind tunnel,cold soak the plane overnight,, blow on it for a half hour to get everything cold and sticky........ get some fire hoses....that should do it....

I doubt it very much - you won't get anything like representative ice build up from a hose onto a cold surface. Ice shape is critical, and you'll only get the right ice shape by genuinely representative icing conditions.

G

[ICT_SLB]

Have to agree with Genghis - you don't get proper icing results even flying with a Tanker plus, for Part 25 aircraft, you now have to fly the Autopilot in icing. Our last icing trials (CRJ1000) benefited from having a Weatherworx satellite feed and also by the great advice from our weather guy in Colorado

[johns7022]

So that's how it's done...everyone is sitting at the restaurant, waiting around for the bat phone to ring....'Hey we got reports of icing in Colorado...whoopee....we get to go flying today!"

In-flight testing makes sense because you need to see how the plane flies under those conditions, but I think the wind tunnel would give a much better indication of where the build ups occur, and the ability to really load up the plane safely.

But hey, if that's how it's done...waiting around for the phone call...what a great job...you could stretch that gig out for YEARS.

[Genghis the Engineer]

So that's how it's done...everyone is sitting at the restaurant, waiting around for the bat phone to ring....'Hey we got reports of icing in Colorado...whoopee....we get to go flying today!"

In-flight testing makes sense because you need to see how the plane flies under those conditions, but I think the wind tunnel would give a much better indication of where the build ups occur, and the ability to really load up the plane safely.

But hey, if that's how it's done...waiting around for the phone call...what a great job...you could stretch that gig out for YEARS.

I recall some happy days of my youth testing a training aeroplane at Boscombe Down for wind limits - it reached a rather amusing point where the values we wanted co-incided with the "no fly" limits for the fast jets (parachute dragging limits on the seats were their restriction). So, for some entertaining winter days, I and the gent who now runs most of MoD's flight testing used to trundle around the circuit doing crosswind landings in an air cadet training aeroplane whilst the Tornados and Harriers were grounded for the day.


More seriously, there are various tools - the tanker is one, there are various ice build up numerical method tools that allow engineers to predict ice formation, and then either CFD it or make up plastic models and stick them in the wind tunnel. Another, which I was privileged to play with for a while was the Boscombe Down blower tunnel...

http://www.profeng.biz/2007/2010/images/201000531.jpg

... which will make a reasonable stab at putting calibrated icing conditions onto discrete bits of the airframe.


But all of these carry inaccuracies and difficulties, and as ICT says, ultimately you need to get the aircraft into some known icing conditions, probably with a nephelometer or similar combined suite of water phase and particle size distribution instrumentation strapped under the wing to characterise the conditions.

It is a fascinating - if specialist - branch of testing, and not as well understood as it deserves to be.

G

[leonard17F]

We will use the services of the weather guy based in CO. The A/C shall be based in Nashville or Louisville, i.e. not too far but NOT WITHINE the bad icing area itself, so that we will be able to T/O and land safely, and also away from ATC congested areas. I hope to be part of the campaign. I will try to send pics later. Happy New Year everybody !