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nsteense
08-20-2010, 01:49 AM
Last week I flew back myself from RAF Cosford to the mainland, after an excellent visit to the RAF museum. I had a flightplan filed for FL090, which with the weather at the moment, took me into the clouds. At some point, climbing from FL080 to the assigned altitude, the moisture on the wings turned into ice. Knowing that ice and wings usually don't mix very well, and aware that the Mooney I was flying isn't fitted with any anti ice equipment, I tried to climb above the clouds hoping that flying in the sun would clear the ice on the wings. That didn't do the trick, so I finally had to fly into lower altitudes, where the temperatures were at least positive enough to clear the ice.
But it made me wonder. Knowing that the fighters based in England during WW2 sometimes took off in low clouds to escort the bombers towards Germany, how would they have dealt with the icing conditions you can expect when climbing through clouds after passing the freezing level. I know that the bombers had the de icing boots, but what about P51, P47, P38, Spitfires and the likes...? How would they have dealt with these conditions Just keep on going when it happened??

BillSwagger
08-20-2010, 08:13 AM
I know post '42 many planes had a defroster for the pit to keep ice off the windscreens and i'm certain that similar vents used to heat gun/cannon ports probably also served the purpose of keeping the wing ice free. Its actually a good question.
I think if you check a log file for any nation at that time you would also see a considerable amount of aborted missions due to "weather". A bit broad of a description and in some cases probably refers to conditions that were prone to icing the wings.

I find it odd that a plane would take off in bad weather or if it were in the forecast, so it was probably a frequent problem now that you mention it.



Bill

Bremspropeller
08-20-2010, 08:13 AM
They didn't have any de-icing equipment the likes of the bombers and I wouldn't be surprised if a lot of crashes were caused by exactly that.

Then again, they were powerful enough to outclimb icing quickly, keeping the time spent in icing-condidions rather short.

nsteense
08-21-2010, 09:42 AM
Originally posted by Bremspropeller:
They didn't have any de-icing equipment the likes of the bombers and I wouldn't be surprised if a lot of crashes were caused by exactly that.

Then again, they were powerful enough to outclimb icing quickly, keeping the time spent in icing-condidions rather short.

If you enter some stratus clouds during the winter time, you can expect to be in it for a long time, so outclimbing it doesn't seem to be valid...
On the other hand, once in clear sky but below freezing temperature, ice on metal skin doesn't seem to disappearing by sunshine alone.

There must have been quite some accidents related to icing...

p-11.cAce
08-21-2010, 11:18 AM
On the other hand, once in clear sky but below freezing temperature, ice on metal skin doesn't seem to disappearing by sunshine alone.

Actually ice sublimates rapidly once you get into clear air.

jarink
08-21-2010, 05:03 PM
Early P-51s actually had a nozzle at the base of the props for anti-icing, but it was never used. Many fighters (and some bombers) did have some form of heater for the guns to keep the feed mechanism from freezing.

nsteense
08-23-2010, 12:53 AM
Originally posted by p-11.cAce:


Actually ice sublimates rapidly once you get into clear air.

Not when it happened to me two weeks ago when I popped out of the clouds at FL100. Even switching on the taxi and landing lights which, in a Mooney, are located at the leading edge and radiate some considerable heat, didn't help in that area. On the other hand, it was only a thin layer of ice on the wings, but it was affecting the performance...

Maybe the heating of the gun bay, was sufficient enough to clear ice?

Bremspropeller
08-25-2010, 09:23 AM
At FL100, there's usually enough moisture to keep the ice from getting off quickly.

Ice isn't much of a deal above FL250, though - the air is just too dry and too cold to support any form of icing.

There's also a big influence on how your wing is impacted by icing, set by the airfoil.
Some airfoils are almost ice-resistant, while others will pick ice up quickly.
IIRC, sharp leading-edges are more prone to icing than more round ones - they're more handicapped by the effects of ice in any case.
There's an interesting NASA-video about icing on youtube.


The performace-impact depends on the icing-conditions, the aifoil, time spent inside icing-conditions etc.
The additional weight, drag and different pressure-distribution all add up to a net performance-loss.

Some de-icing boots won't help much, because the ice turns into water-droplets, flows back on the wing's surface and re-freezes there.
That might ruin your day when flying turboprops in the wether...
Jets usually have powerful enough anti-ice to completely evaporate any ice-chunks in quite a short time.

Alltogether, the best idea is to avoid icing in the first place, unless you're having high-temperature bleed-air tp blow all through the leading-edges.

nsteense, what kinda Mooney are you flying btw?

Monty_Thrud
08-25-2010, 09:31 AM
No idea about this but there was some form of heating ducted from the engine that stopped the guns from freezing in the wings AFAIK, maybe this would help the icing issue a little...?

nsteense
08-26-2010, 12:44 AM
Originally posted by Bremspropeller:
At FL100, there's usually enough moisture to keep the ice from getting off quickly.

Ice isn't much of a deal above FL250, though - the air is just too dry and too cold to support any form of icing.

There's also a big influence on how your wing is impacted by icing, set by the airfoil.
Some airfoils are almost ice-resistant, while others will pick ice up quickly.
IIRC, sharp leading-edges are more prone to icing than more round ones - they're more handicapped by the effects of ice in any case.
There's an interesting NASA-video about icing on youtube.


The performace-impact depends on the icing-conditions, the aifoil, time spent inside icing-conditions etc.
The additional weight, drag and different pressure-distribution all add up to a net performance-loss.

Some de-icing boots won't help much, because the ice turns into water-droplets, flows back on the wing's surface and re-freezes there.
That might ruin your day when flying turboprops in the wether...
Jets usually have powerful enough anti-ice to completely evaporate any ice-chunks in quite a short time.

Alltogether, the best idea is to avoid icing in the first place, unless you're having high-temperature bleed-air tp blow all through the leading-edges.

nsteense, what kinda Mooney are you flying btw?

Bremspropellor,
the Mooney I sometimes fly is a M20J (enter OO LVT into keywords at Airliners.net, and you will see a nice picture of it). Not exactly suitable material to reach FL250 http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif, where indeed the air is usually too cold to contain any moisture. Even trying to reachFL100 was really at the very limit of the engine...

Anyway with regards to Spitfires and Mustangs I asked the question to Steve Hinton, who has some intimate knowledge of the internals of those era airplanes and this is his answer:

"There was no de or anti icing on most of the fighters from that era. There were a few Russian, Brit and German special equipped to handle icing by directing engine exhaust thru the leading edges or by de-icer boots. A P-51 could fly above the ice in most cases however many times flights were canceled because of icing. As you know the weather was usually bad and it was a hugh problem flying those airplanes in bad weather and many were lost. Your Mooney is held to the same limitis a Spitfire or P-47 is. If the ice is building, it greatly degrades performance.
Steve"

And I managed to get hold of Bud Anderson, asking about icing conditions during WW2 here in Europe and this is his reply:

"All I can say is that in all 116 mission, 480:20 hours combat flying from England I never encountered problem icing conditions. I believe that we must have passed through the icing level so rapidly that we never got iced up. I don't remember seeing any ice the entire time going up or coming down though the clouds. I did fly from Feb 44 through Jan 45 so we had a full winter and a spring of flying. 1944-45 was supposed to be one of those 100 year winters when it came to bad weather for England. I flew a lot in the clouds. We had a fuel ejection type carburetor so icing was no a problem with the engine. That is about all I can remember! Take care (bud anderson)"

So it seems that the Mustang could outclimb ice forming on the wings...

Col_SandersLite
08-26-2010, 06:24 AM
Originally posted by nsteense:
...Bud Anderson...

Just wanted to point out something:

This makes perfect sense from bud anderson's point of view. The 8th AF flew mostly high altitude missions in the ETO.

I wouldn't be surprised to find that the VVS and Luftwaffe had completely different experiences in the eastern front where combat missions where typically flown at much lower altitudes.

I doubt it was much of an issue in the PTO and Africa, but it might have been something to worry about in the MTO as well.

Bremspropeller
08-26-2010, 09:03 AM
Icing occurs inside clouds of mostly stratus and cumulus-type.
Whenever you're climbing through these clouds (same for descending), there's a chance of icing-up when the right (or therefore "wrong") conditions prevail.

Icing could also happen in tropical regions, though it's less likely.


The german-modification mentioned is most likely the /R11 Rüstsatz - not quite sure, if it really did address that issue, though.


OO LVT
Nice one!
My aerodynamics-professor does have an M20J as well, though his is powered by a Porsche PFM http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif

M_Gunz
08-26-2010, 10:33 AM
Does the lower pressure over the top of the wings contribute to icing? Wouldn't the same in dry air contribute to sublimating ice?

Bremspropeller
08-26-2010, 11:58 AM
Ice is only picked up by the leading-edges and thus alters the flow-characteristics at AoA.
Drasticly increased stall-speeds and a lot of additional drag are the poblem here (no so much the additional weight).
That kind of icing will also affect struts and antenna-aerials.

Another type of icing occures when moisture flows over cooled parts of the airframe (fuel-tanks with sub-zero cooled fuel, for example).
This type of icing doesn't form on leading edges and is thus relatively uncritical in terms of aerodynamic-performance.
It adds LOTS of weight, though.

nsteense
08-27-2010, 12:21 AM
Originally posted by Bremspropeller:
Icing occurs inside clouds of mostly stratus and cumulus-type.
Whenever you're climbing through these clouds (same for descending), there's a chance of icing-up when the right (or therefore "wrong") conditions prevail.

Icing could also happen in tropical regions, though it's less likely.



Couldn't have said it better, icing occurs basically when there is moisture in the air and when the temperature is at or below freezing point up until a certain low temperature when it is too cold to contain any form of condensation.


It doesn't matter if you're flying high altitude missions, because if there is an overcast, you still have to fly through that to reach high altitude.