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Why do Mosquitos have 5 tubes in their exhausts stacks and not 6


David Womby

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Looking at KA114 the wonderful Kiwi flying Mossie, I was reminded that I had wondered about this for years. So: Merlin engined Spitfires, Hurricanes and Lancasters all had/have 6 tube exhausts - why not the Mosquito? Is it because the 6th one would be too close to the wooden wing for safety?

David

Edited by David Womby
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Edgar said:

"On early Marks, they had to keep the exhaust well away from the wooden structure, so 5 & 6 were combined into one."

Aussies musn't be very smart :fool: or must have used more heat resistant wood :banghead:. Their local equivalent of the F.B.VI, the F.B.40 used six stub exhausts on the outboard of the nacelles. Five stub exhausts were used on the inboard side of the nacelles.

I always understood that the sixth exhaust was doubled up with the fifth to make five stub exhausts as the sixth stub would have intruded into the radiator intake on the inboard side of the engine nacelles. There was just no room for a six pack exhaust. Note how close to the radiator intake the last stub is. BTW, the radiator housing is metal, not wood.

Exhaustsinboard.jpg

Five stub exhausts on an F.B.VI.

The Poms, being the smart little cookies they are, obviously standardised and also used five stub exhausts outboard. We Aussies like to do it OUR way :wicked:, so we used a six stub exhaust outboard.

FB40_2.jpg

Six stub exhausts on an F.B.40

A52-unkDH98Mosquitobankinghardfullbottomview.jpg

F.B.40. Six out, five in.

Cheers,

Peter M

Edited by feropete
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Edgar said:

"On early Marks, they had to keep the exhaust well away from the wooden structure, so 5 & 6 were combined into one."

Aussies musn't be very smart :fool: or must have used more heat resistant wood :banghead:. Their local equivalent of the F.B.VI, the F.B.40 used six stub exhausts on the outboard of the nacelles. Five stub exhausts were used on the inboard side of the nacelles.

I always understood that the sixth exhaust was doubled up with the fifth to make five stub exhausts as the sixth stub would have intruded into the radiator intake on the inboard side of the engine nacelles. There was just no room for a six pack exhaust. Note how close to the radiator intake the last stub is. BTW, the radiator housing is metal, not wood.

Peter, you are absolutely correct of course.

The fact is there is physically no room for 6 on the inboard side of the engine because of the radiator housings, so the rearmost 2 stubs were combined. I believe it most likely that British-built aircraft used the same arrangement on the outboard sides of the engines purely for standardisation's sake. As the Aussie aircraft show, there is no reason why 6 couldn't be used if required.

Even with 6 stubs it's not that close to the wing. So I've never given the 'keep heat away from the wood' theory much credibility to be honest, much like the theory that the stiffening member over the rear equipment hatch on the starboard side of the fuse was actually a gutter! I know that one to be 100% wrong!

On the 2-stage Merlin engined aircraft there were 6 on all sides because the longer nacelle meant there was room to accomodate them.

Edited by StephenMG
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I had heard that the reason was to keep the engine exhaust gases from being sucked into the radiator and reducing the engine cooling. Just my 2p from the

(alledgedly) wet coast of Canada. We just broke a 105 yr old record for the least amount of rain. Cheers.

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Edgar said:

"On early Marks, they had to keep the exhaust well away from the wooden structure, so 5 & 6 were combined into one."

Aussies musn't be very smart :fool: or must have used more heat resistant wood :banghead:. Their local equivalent of the F.B.VI, the F.B.40 used six stub exhausts on the outboard of the nacelles. Five stub exhausts were used on the inboard side of the nacelles.

I always understood that the sixth exhaust was doubled up with the fifth to make five stub exhausts as the sixth stub would have intruded into the radiator intake on the inboard side of the engine nacelles. There was just no room for a six pack exhaust. Note how close to the radiator intake the last stub is. BTW, the radiator housing is metal, not wood.

Exhaustsinboard.jpg

Five stub exhausts on an F.B.VI.

The Poms, being the smart little cookies they are, obviously standardised and also used five stub exhausts outboard. We Aussies like to do it OUR way :wicked:, so we used a six stub exhaust outboard.

FB40_2.jpg

Six stub exhausts on an F.B.40

A52-unkDH98Mosquitobankinghardfullbottomview.jpg

F.B.40. Six out, five in.

Cheers,

Peter M

Ah Peter, just think of the weight penalty & excess use of raw materials with that extra stub- they forgot about that one :cheers: Edited by Radpoe Spitfire
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Looking at KA114 the wonderful Kiwi flying Mossie, I was reminded that I had wondered about this for years. So: Merlin engined Spitfires, Hurricanes and Lancasters all had/have 6 tube exhausts - why not the Mosquito? Is it because the 6th one would be too close to the wooden wing for safety?

David

Woah, have i missed something ?

I have been following the Mosquito Restoration page on Facebook for about two years - is KA114 really flying again now ???

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Woah, have i missed something ?

I have been following the Mosquito Restoration page on Facebook for about two years - is KA114 really flying again now ???

You really missed it? She flew last week and did a stint at an NZ airshow this past weekend. There are plenty of videos online but I just discovered this one which is rather cute:

David

PS - there's an Anson flying in NZ now too.

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You really missed it? She flew last week and did a stint at an NZ airshow this past weekend. There are plenty of videos online but I just discovered this one which is rather cute:

David

PS - there's an Anson flying in NZ now too.

Wow, thanks for that. I missed it completely because I have been recuperating from surgery.

The first pass in that vid brought a tear to my eye. Damn, hope I get to see a flying Mossie one day..

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You really missed it? She flew last week and did a stint at an NZ airshow this past weekend. There are plenty of videos online but I just discovered this one which is rather cute:

David

PS - there's an Anson flying in NZ now too.

Blimey!!!!!!! what a lump in the throat moment that was to see a Mossie airborne again- even though I only saw the film clip like time lapse photography( my works pc limitations ) I was awstruck to see it.

Thanks for the link. :thumbsup:

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  • 2 weeks later...

Later Canadian ones had the six outboard too - presumably they had five inboard but i wasn't aware of that. Obvious really, but does lead to extra spares stock required. "Sorry mate, haven't got a 6-by starboard outer. Lots of port inners but they're only 5-by so no good for you?"

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Going off at a slight tangent........

The wartime Soviet Petlyakov Pe-9 heavy bomber, powered by the AM-35 inline engine had 5 exhaust stacks on both sides of all the engines EXCEPT the outside of the inner engines - which had six stacks!!

pe-8_03.jpg

The last two ports (5 & 6) were combined into a single stack on the inside inner engine and both sides of the outer engine.

I have no idea why...... maybe cabin heating ??

Check out the Zvezda kit (the AM-35 one, not the latest one or the Amodel kit - with ASh-82 radials)...

pe-8_06.jpg

pe-8_02.jpg

Ken

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The Russians used exhaust gas in their fuel tanks as a fire-suppressant, so could that be where it came from? Not a reason for the Mosquito. British aircraft used a separate pipe embedded in the exhaust for heating purposes, and this can be seen on certain Spitfires and Halifaxes - perhaps others but I'm not familiar with those.

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Oh now that's one I've never seen before. What mark is it and why two pipes only?

D

Those two pipe exhausts are the type known as "saxophone". there were a whole range developed for the Merlin. The reason you don't see them is they are normally covered by the bulbous night anti glare fairings which have been removed from that a/c. Note the shape of the exhaust stain. Sea Hornets NF21's had a setup with four stacks IIRC. On the short single stage Merlins the exhaust gasses could be sucked into the rads due to the airflow close to the rad lips.

John

Edited by John Aero
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