B-24 & B17 de-icing boots.

[old thumper]

The question concerns the pneumatic de-icing boots fitted to B-17 and B-24 wartime bombers. What I would like to know is by how much de-icing boots would have changed the shape of the leading edge, rudder or tail surfaces they were applied to (while uninflated)?

Did the leading edges of these bombers have to be altered to fit de-icing boots or were they simply added over the surface?

If modelling a B17 or B24 should these black areas overlap or be flush with the surface they meet?

[Jamie @ Sovereign Hobbies]

They're just glued on. There's no recess to sit it or anything like that - the boots are literally stuck to the metal leading edges. I've never handled B17 or B24 boots personally, have lent a hand sticking replacement boots to other aircraft and they were quite thin things in real terms. It's going back some but they were less than half an inch thick.

[gingerbob]

In fact there were times that the de-icing boots were removed from aircraft- just plain peeled off (intentionally). EDIT: When I said "just plain peeled off" I didn't mean that to be an accurate description of the removal process, just that if you took them off you found a normal wing underneath.

bob

Edited September 27, 2015 by gingerbob

[dpm1did1]

I believe deicing boots were pretty much universally removed from any daylight operations aircraft once in a warzone, and especially so in Europe, because they were particularly vulnerable to flak damage. Having extra drag from the perforated and flapping rubber certainly would not have helped the performance of the already lumbering US heavies.

Conversely night bombers, patrol aircraft etc were far more likely to retain them due to the increased likelihood of encountering icing at night and at low level over water.

As noted previously although they weren't technically flush fitting they weren't particularly pronounced either as they still had to be aerodynamic. The result is they would appear flat at smaller scales and so representing as mere black painted edge is good enough. (although if planning a 1/24 heavy a small step may definitely be worth including - as well as a stiff drink and a house clearance to allow space)

Edited September 26, 2015 by dpm1did1

[old thumper]

Having just searched I can see from wartime photos of the 8th Air Force that de-icing boots are indeed not visible in the majority of cases. Yet I think also in the majority of cases they are shown in kit painting instructions and very often on completed models.

Thanks all.

[dpm1did1]

Iirc they were fitted at the factory stateside as standard and removed at the units once in theatre. Indeed a quick Google of the differences between black edged wings in some pics and all silver in others does tend to correlate with out-of/in-action respectively. Obviously early planes would been in combat with the boots before the damage/drag issue became a deciding factor on their removal.

New arrivals may not or may not have carried them on early missions, and their priority of removal may even have been different between units. Plus of course kit illustrations and paint instructions aren't always 100% particularly for generic markings abd colours

Post war they may well have been refitted, although the airframes themselves often didn't see much flightime once hostilities ceased as B-17s in particular were very quickly reduced to secondary roles, or unceremoniously scrapped. Certainly I've seen pics of C & VB-17s with them and probably others if checked

Edited September 26, 2015 by dpm1did1

[noelh]

I bet there times when crews wished the boots had been left on. There is nothing quite so disconcerting as seeing ice build up on your wings when you have no way to clear it. It can happen winter or summer too. Been there, done that.

But they do add drag and would be a lot of work to keep serviceable in wartime.

[Graham Boak]

Even operating out of the UK most missions would not have been flown in extreme weather, so the de-icing boots were not as vital as they would on (for example) transport aircraft flying a great circle route over the Atlantic.

I do wonder a little about just how and where they were attached, and what the wing section looked like with/without them. Flow at the leading edge is very sensitive, it's the last place where you want distorted shapes, steps, gaps etc. You can design the wing to accept such a device, for example by recessing them, but what do you get when you take them off?

[noelh]

I dug out my copy of Roger Freeman's book 'The mighty eight in colour'. Lots of nice pictures of B17s and B24s. Some with boots some without. There's even a photo of a formation of B17s showing a mixture within the group. The majority of B24s seemed to retain the boots. While on the B17s it seems the boot on the fin was the most likely to be retained.

There's a couple of photos dated May 1945 which show B17s complete with full boots, so it seems they weren't automatically removed. Check your references seems to be the order of the day.

Graham: You don't need extreme weather to experience icing. I've encountered it well below 10,000 feet on relatively benign summer days. All those typically of summer fluffy cumulus clouds hide a dark secret. But almost any cloud can produce serious icing if the conditions are right. In winter with 0 deg C on the ground, there will be ice in all cloud.

You are right though it would be far less critical to bombers whose natural operating altitude would be above most cloud and icing doesn't form below -40C unless you fly into a thunder cloud in which case it would be merely one of your many problems. Patrol aircraft and transports would naturally be operating low down in the weather. They would definitely need boots.

As for the boots themselves, as dpm1did1 pointed out they are glued on and are really quite flush with the leading edge. They are nothing more than a rubber inner tube. I doubt very much if the boots were ever recessed as quite often they were in fact an option rather than standard.

[rossm]

Note that in RAF Coastal Command the de-icing boots on the grey/white scheme were often dull silver as here http://www.iwm.org.uk/collections/item/object/205210603

[noelh]

Didn't the RAF used a paste of some sort on the leading edge?

[old thumper]

Didn't the RAF used a paste of some sort on the leading edge?

Yes, on most painting instructions this paste is shown as yellow but apparently it was more of an orange colour.

[bzn20]

They dont inflate very much,a small amount of movement is enough to crack off any ice and stops it building to detrimental thickness. The boot doesn't change the L/edge profile very much . Its a fast cycle, inflate deflate inflate deflate etc..

[noelh]

Yes it's very odd to look at. Only seen it on the ground during maintenance. Looks really odd.

[bzn20]

The painted on paste is in with a group of de-icing fluids. I can't remember all the different compounds from training, AL 34 was one. The colour of that paste was so you could tell that it had been applied like all the fluids. Its a type 2 fluid ,yellow,and thick so it stays or is slow to move away from the designed treatment area up to a speed of about 100 mph. It's a long time since I did all the different de-icing fluids in training. I've haven't seen that paste since training and guess it was superceded due to aircraft moving at higher speeds or the 'planes I was involved with more likely. Type 1 fluids are thin liquids,glycol based,Orange.type 3, medium viscosity are used on slower aircraft,Yellow. My brain hurts....

[vppelt68]

Thank you for precious pieces of information, they are timeless! Does anyone know how wide, exactly, was the B-17 leading edge de-icing boot? I don't mean the length, which can be estimated from photographs. I suppose they were of a standard design so didn't differ a lot, but would like to know the dimensions when painting one. Best regards, V-P

[72modeler]

As the others have posted, the rubber boots inflated and deflated rapidly- just enough to break the ice from the leading edge and expose the sheet to the airflow, peeling off large sections of ice. It's very hard to make out in most wartime photos, but if you look at factory photos or high quality closeups, you can see the holes in the leading edge of the wings where the deicer boots have been removed. Especially common in photos of B-17's, B-24's, B-25's, and B-26's that have had the boots removed. I always wondered what those little holes were for when I saw them in photos until I learned their purpose.

 

This is probably off-topic, but while looking for B-17  deicer boot photos, I found a pretty neat website, the link for which I have posted below. If you scroll past the several pages of history and description, you will find numerous factory photos that show interior and exterior details of B-17's from the prototype to the B-17G- many of which I have never seen before. There are two photos that show the deicer boots being applied on the fin and wing leading edge that illustrate the thickness of the rubber sheet. I hope you will find these useful and informative.

Mike

 

https://books.google.com/books?id=YMY9DwAAQBAJ&pg=PT116&lpg=PT116&dq=B-17+Flying+Fortress+deicer+boots&source=bl&ots=-0dbGc0hp8&sig=yVPVydu3mkg4s4nOkcaDjBgMHz0&hl=en&sa=X&ved=2ahUKEwi9yO-_tuDdAhVDeKwKHbklB6cQ6AEwC3oECAQQAQ#v=onepage&q=B-17 Flying Fortress deicer boots&f=false

[Sonoran]

Whether the aircraft is operating during the day or night is utterly irrelevant to the incidence of icing.  Icing requires visible moisture and temperature below freezing (that’s what I learned in ground school almost 50 years ago).  The main reason they were removed from USAAF daylight bombers is that the bombers generally only operated in good weather conditiions, and there was little chance of operating in icing conditions.  Icing doesn’t happen at 24,000’, where there is no moisture (only ice crystals generally, if anything), and that’s where they were operating.  And as noted, they were a maintenance headache, so they were removed.

[Chris Jephcott]

Slightly off topic I suppose but...

 

A lot of modern turboprops still use the boot system. I used to fly the Dash 8-400 and this was the same system - despite 60 odd years between types! And they still are a maintenance nightmare too, with pressure cautions every time they were operated.

 

However, I have managed to gain icing at 24000 feet - the general consensus is that ice doesn’t form below -40C, an incredible temperature if you think about crew operating in such temperatures in an unpressurised environment. 

 

Chris