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Remembered Today:

Carburettor Icing.


pete-c
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And before forum members think I've lost the plot, this isn't something to do with the Great British Bake Off !!

Would anyone have ever come across anything to do with the above mentioned phenomenon? I'm trying to find clues as to when the first recognised occurrence of ice forming in the air intake system of aeroplanes may have been. Pilot's log books - Operational reports?

I've absolutely no idea if this would have been known about before WW1 or not.

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And before forum members think I've lost the plot, this isn't something to do with the Great British Bake Off !!

Would anyone have ever come across anything to do with the above mentioned phenomenon? I'm trying to find clues as to when the first recognised occurrence of ice forming in the air intake system of aeroplanes may have been. Pilot's log books - Operational reports?

I've absolutely no idea if this would have been known about before WW1 or not.

This is still a common problem with piston engines, it is normal to apply carb. heat regularly to melt intake ice. If you don't, the intake gets restricted, the mixture changes and the engine runs rough. Then it stops!

Quite a few accidents are down to carb. ice.

Howard

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Thanks Howard. I did come across a similar up to date website which explained much the same thing in some detail. Bill Gunston's book, Piston Aero Engines also gives a good explanation but unfortunately doesn't give any clues as to when this problem was first recognised.

I was just wondering when early aviators would have first experienced this problem. If an engine had suddenly failed my guess is that the unfortunate pilot would have probably thought either magneto issues or a fuel blockage were to blame.

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According to this link http://thevintageaviator.co.nz/projects/engines/raf4a-engine/raf-4a-engine the Royal Aircraft Factory RAF4a engine which powered the RE8 had "some unusual features such as exhaust preheating of the intake air to prevent carburettor ice and help atomize the fuel /air mixture." The RAF4a was first run in 1914.This is

This is great info - many thanks. I was in fact at the RAF Museum on Friday and whilst studying the RE8 was intrigued by the various tubes exiting from the bottom of the engine cowling. I had a suspicion that these were perhaps something related to carb heating - the larger ones being the actual carb air intakes.

So it would appear that icing was a known phenomenon at the beginning of WW1. The search goes on to discover any earlier instances.

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According to this link http://thevintageaviator.co.nz/projects/engines/raf4a-engine/raf-4a-engine the Royal Aircraft Factory RAF4a engine which powered the RE8 had "some unusual features such as exhaust preheating of the intake air to prevent carburettor ice and help atomize the fuel /air mixture." The RAF4a was first run in 1914.

The much loved RAF Chipmunks had the carb heat wired permanently hot using an exhaust heat exchanger, Ok they did not ice but the trouble is it reduces engine power. When I flew my Grumman AA1, applying carb heat gave a noticeable loss of power; it was routinely applied on final approach but an important check was to ensure it was off before landing in case of a go-around when you need all the power available. This aircraft and those with simple Lycoming engines suffer from many of the problems of Great War aircraft as the engine was designed in the 1930s and the weight and speed are comparable. No turbo so altitude is limited, magneto ignition, fixed pitch prop so take-off and cruise are both a compromise- (you need fine pitch to take off and coarse to cruise- a variable pitch prop does that, rudely called a wobbly prop, but were only available after the war.). When an intake ices, the engine first loses power, then runs rough then cuts out. If you are very lucky, residual heat will melt the ice and allow a restart in the air but only after a lot of height is lost. Oddly, carb ice is worse in warm damp air, so many would not have thought it a problem in the summer, but it is. By the time crash investigators get to the crash site, the ice will have melted so the "cause" may be missed, but as Great War aircraft were slow, it would have been easy to do a dead stick landing so no crash. After a bit it would re-start leaving some to wonder why it had stopped. Crab ice is insidious and still catches people out.

Howard

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Not for a moment do I doubt that crab ice is insidious, and I'm only surprised that there has not been someone of the RN persuasion along earlier to say so.

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. Oddly, carb ice is worse in warm damp air, so many would not have thought it a problem in the summer, but it is. By the time crash investigators get to the crash site, the ice will have melted so the "cause" may be missed, but as Great War aircraft were slow, it would have been easy to do a dead stick landing so no crash. After a bit it would re-start leaving some to wonder why it had stopped. Crab ice is insidious and still catches people out.

Howard

Howard, you have touched on why I started to investigate this phenomenon. RNAS Short seaplanes operating in the Aegean suffered many "engine failures". The cause of these are never fully explained but they are usually attributed to overheating coolant. The pilot would then alight on the water in order to let the radiator temperature stabilise before taking off again.

As you point out carburettor ice can form in the most unlikely conditions; for example, a warm Aegean summers day. (I had already found out this peculiarity from another website) So, could some of these "engine failures" possibly be attributable to ice, just as much as overheating? Again as you point out, by the time the aircraft had spluttered to a halt on the water - the pilot probably thinking it was a magneto or fuel problem - his observer had scrambled out of the cockpit and climbed down on to the float to try and diagnose the problem, there would be no obvious reason for the failure. After poking and prodding various leads and connections the pilot would be given the OK to try and start the engine again and - bingo, all would be back to normal.

The make of engine fitted to these aircraft did indeed feature an exhaust heated induction system, but weather these seaplanes were originally fitted with this equipment, or if it was something that was subsequently fitted I have not yet discovered.

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Not for a moment do I doubt that crab ice is insidious, and I'm only surprised that there has not been someone of the RN persuasion along earlier to say so.

Ian, you should be ashamed of yourself. Go to the back of the class and behave ! Anyone can make a spolling mistake.

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Ian, you should be ashamed of yourself. Go to the back of the class and behave ! Anyone can make spolling mistake.

Indeed, crab ice is insidious, so is fat finger syndrome! Luckily, I only continue to suffer from the latter except for one minor incident of induction ice in 23 years flying. Some aeroplanes are not that prone to it (like the Grumman AA1), some are terrible like anything with a Continental C90 engine, e.g. Piper Cubs.

Howard

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The pilot would then alight on the water in order to let the radiator temperature stabilise before taking off again.

Most pilots I know dislike the idea of water cooled engines- too much to go wrong. Air cooled have their problems, like cylinder head cracking induced by too rapid cooling, but most of the time they just chunder on and on and on......

It is not so much that the engine itself "breaks", but things like the hose between rad and engine start to leak, water pumps, fan belts. Remember that on old cars? I do and would think about it approximately half way across the channel.

If you read AAIB accident reports, carb ice is still a problem, solved by injected engines but these are expensive. Look at your local airfield and see rows of C152s, PA28s etc. all with (twin) magnetos on horizontally opposed engines designed in the 1930s. Nice modern engines are expensive to get approved, so the old gas-guzzling and very noise engines remain, along with the carb heat knob and the BUMMMFITCHH check.

Howard

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Carb heat was very much a part of pilot training even here in Oz. I can still remember the first (and ONLY) time I used partial heat early (VERY EARLY) in my training many moons ago. My right shoulder is still bruised from the thump I received from my instructor.

"What are you trying to do?? Kill us??"

Just about any engine drill involved carb heat. Engine failure practice with engine idling and carb heat ON..every thousand feet open throttle and turn off heat briefly to keep engine "clear" . BUMFF....etc (depending on aircraft) checks on downwind and PUFF check on final.

On the smaller Cessnas the undercarriage was always "down and welded! Ahhh...memories!

A question to those more knowledgeable here....would the La Rhone (and other) rotaries have had icing problems? As I understand it they didn't really have throttles, just a blip switch. Was there a butterfly valve to ice up on those????

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"When an intake ices, the engine first loses power, then runs rough then cuts out. If you are very lucky, residual heat will melt the ice and allow a restart in the air but only after a lot of height is lost."

This valuable comment struck a chord.

A number of Great War books which I have read in a recent aviation book binge refer to engines cutting out and the flyer restarting either without any without any problems or a few attempts after coming down to a lower altitude. I do not recall any of them offering diagnosis, but Howard seems to be offering a strong possibility for the problem and its solution.

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Most pilots I know dislike the idea of water cooled engines- too much to go wrong.

Howard

The Salmson engines I am researching were I believe the only water-cooled radials that were in use during WW1; water-cooling being much more associated with in-line engines.

These seaplanes, as well as being used on the face of it in ideal flying conditions were of course also operating over an ocean. So, a double whammy; warm air, and a large amount of moisture. Conditions that we now know are perfect for ice to form.

wheelsjbl,

I must admit I've no idea if rotaries suffered from the same issues.

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A number of Great War books which I have read in a recent aviation book binge refer to engines cutting out and the flyer restarting either without any without any problems or a few attempts after coming down to a lower altitude. I do not recall any of them offering diagnosis, but Howard seems to be offering a strong possibility for the problem and its solution.

This does indeed sound as though it could be icing. David, could you give me any titles? And has anyone else come across such incidents in other publications?

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Going back to post no 1 the only first hand account l can recollect is by Frank Courtney in FLIGHT PATH .

He was forced down into a field on a hot Summers day and found ICE

inside the engine.Nobody believed him at the time.This was during a 1919 air-race if my memory is accurate,l haven't the book to hand so don't know the aircraft type etc.

Still it is the earliest case on record.Perhaps someone could confirm this?

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It would seem that the build-up of ice within a carburettor inlet was well known in the automobile world. Apparently a book called The Maintenance of Motor Cars by Eric Walford, published in 1916 mentions it.

If I recall correctly it is mentioned in Into the Blue and I chose the Sky, both pilots flew 1i/2 Strutters and Camels

I think these must be Into The Blue, by Norman Macmillan, and, I Chose The Sky, by Leonard Rochford RNAS. Both these are books I haven't read so they would indeed be worth checking out

Going back to post no 1 the only first hand account l can recollect is by Frank Courtney in FLIGHT PATH .

I shall certainly investigate this account as well.

Many thanks chaps.

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If I recall correctly it is mentioned in Into the Blue and I chose the Sky, both pilots flew 1i/2 Strutters and Camels

Both of these were powered by rotaries though and as I understand it rotary engines didn't use the venturi type carburettor which is susceptible to ice formation. Rotaries used a 'Bloc-tube' carburettor apparently (we need an engine expert here!).

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If I recall correctly it is mentioned in Into the Blue and I chose the Sky, both pilots flew 1i/2 Strutters and Camels

l re-read INTO THE BLUE just last month and theres no icing mentioned in it. Perhaps you're thinking of "blueing"? Now that a different subject. :huh:

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I recall watching a Great War LVG CVI crash following carb icing. It was a warm afternoon and I doubt it went above 3,000 ft at any point. And whilst I am old, I feel the need to add the clarification that it was the Shuttleworth collection's restored LVG at a display in the 70's.

Clive

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I recall watching a Great War LVG CVI crash following carb icing. It was a warm afternoon and I doubt it went above 3,000 ft at any point. And whilst I am old, I feel the need to add the clarification that it was the Shuttleworth collection's restored LVG at a display in the 70's.

Clive

Thanks for that info Clive. I must admit upon reading your first sentence I thought crikey - he must be a good age!

Old Warden though would certainly be a good place to enquire about this phenomenon. Would you know if this particular aircraft was re-built?

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It was repaired and flew again for many years. I think it's now a static exhibit at the RAF museum but the Shuttleworth folk will almost certainly have records of the incident. I'm sure I'm not alone in recalling this!

Regards

Clive

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