Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules

Beautiful aircraft, restoration looks pristine. I'm amazed the wood bits survived all the years before restoration.
Well, at least the engines and cockpit bits are genuine items.

Another detail most people miss is that it has only 5 exhaust stacks per side. The one closest to the wing leading edge serves two cylinders.
The one in our hangar has 5 on both sides.

I just looked at some pictures in my Mosquito books and 5 on both sides is correct.

I could not recall earlier.

It does make sense, though, as they only have 2 types of exhausts (left and right) rather than 4.
I agree you don't want different stacks on opposite side of an engine since the scavenging would then not be the same. And you have to consider it was twin with a left and right engine, so maybe there were exhausts for each side since the right bank of the left engine and left bank of the right engine were facing the pilot. Perhaps night exhaust flames were a concern. I can't say.

After that, it's all guesswork why they did what they did, unless you know the people who designed it and have actually asked. It's not something that generally gets written into short description of WWII aircraft in a book unless it was a rather well-known story to start with.
More information Mosquito exhaust - 5 pipes or 6 ?

Some pictures of different Mosquito exhausts.

Note that originally the Mosquito did not have ejector exhausts. Instead they had each bank of the engine exhaust into a single pipe with an outlet slightly lower.

One of my statements from that time was "The reason is that the single stage engine's rear exhaust would interfere with the leading edge radiator, if not physically the exhaust would affect the radiator."
In round numbers, how much does it cost to restore an old Mosquito?
That's like asking "how long is a rope?". The Avspec Mossies are not restorations but essentially newly built airframes with some NOS and salvaged metal bits. Word on the street is that buying one will set you back between 10 and 15 million USD.

Restorations to flying condition are very different from restorations to a static museum exhibit and therefore carry a large cost multiplier. You can also have the in-between case of a ground runner, like the one I'm involved with. Our budget is approx. $1M CDN but relies entirely on volunteer labour hours. Also to be factored in is the extent of desired authenticity and quality of the final product. Many museum pieces are recognizable from the outside but are mere shells on the inside with no instruments, controls, fuel tanks, mechanical systems, etc. Also, are you stripping old paint and repainting? Are you just stabilizing rotten wood or replacing or a combination of both? Are you, like us, using original BS spec plywood at $1000 per 5x10 sheet or are you using the more commony available marine plywood? The list of options is very long.

So basically your budget will drive the extent of restoration and the quality of the end product.
The reason for the paired rear exhausts was because the inner side was very close to the radiator, which is forward of the wing leading edge.

They could have 6 stacks on the outside, but it would mean 4 different exhausts instead of 2.
Some Australian production aircraft with the single stage Merlins did have six stub exhausts on the outer side of the engines, such as this one
I don't know for sure, but I'm guessing that Mosquito has 2-stage Merlins in it since at least some of them were known to have all six exhaust stacks.

Actually, I have an illustration that shows five exhaust stack (the rearmost covers the last two cylinders on each bank) and another one that shows only two exhaust stack outlets with all six exhaust ports flowing into a single exhaust log that feeds the two outlets. These are covered by a metal fairing and the entire thing is called a "flame-dampening exhaust shroud." We KNOW some of the 2-stage units had six individual exhaust stacks.

So, it appears they definitely experimented with Mosquito exhaust outlets in a rather big manner. I can't help but wonder why.

Other than to address night fighters, why play with the exhaust stacks that much? Does anyone know why the exhaust outlets drew so much attention?
Last edited:
I don't know for sure, but I'm guessing that Mosquito has 2-stage Merlins in it since at least some of them were known to have all six exhaust stacks.
No. It had single stage Merlin 33. There is no second intake immediately behind the spinner to indicate a two stage engine installation. Aircraft history from the ADF serials website.

Looking back through photos many, if not all, Australian built Mosquito FB.40, PR.40, T.43 (all with the single stage engines) seem to have been built with 6 separate exhaust stubs. Here is
A52-1 (I have a photo in a book of her dated to July 1943 before her first flight in that configuration)

And a photo of British built T.III A52-1005 with A52-1 around 1944. Note the difference in the exhausts.



Never noticed that before. Every day a schoolday.
Looked it up and it seems the early exhaust manifolds (the ones with an exhaust log feeding multiple cylinder as well as the 5-port unit) gave issues with heat deteriorating the wood. They played with the manifolds to reduce heat effects and to reduce exhaust flame for night fighters. Logical, anyway.

Users who are viewing this thread