Time for my first idiotic question of the year. Can anyone enlighten me as to why some variants of Mosquito had 6 individual exhaust stubs and others had no 5 & 6 cylinders in each bank siamesed into one stub? Also for stupid question No 2 why some had flame damper shrouds and some open exhausts even on the same mark?
Thanks in advance folks.
By: mike currill - 23rd January 2011 at 11:37
I can imaginethey would with the sudden appearance of the light from the exhaust ports.
By: Mark12 - 23rd January 2011 at 11:29
The exhausts in my image above at Luton were fitted as part of the preparation for its Trans Atlantic flight with Duane Egli and Ed Jurist, the owner, bound for the CAF.
With serviceable exhausts being in short supply, they had just fitted ‘three off’ the available bifurcated pair, normally fitted to the rear most cylinders.
That said Ed Jurist told me later they had quite a fright when one of the exhausts facing in board detached in mid flight.
Mark
By: mike currill - 23rd January 2011 at 09:00
I have heard that the shrouds caused quite a lot of drag and were deleted from most early RAF Mossies. Possibly they were only then used on the NF’s, the day bombers and such didn’t use or need them?
We seem to have lost them early on, on UK Mossies. However, the Australian FB.VI’s still had them in 1945.
Anon.
Yes so have I, in fact only recently I read an article stating that ejector exhausts were good for an extra 10-13 mph over shrouded exhausts. Now if I could just remember where I read it I could post a link to the article. That pic above is a new one on me.
Having looked at some of the pictures I have in various publications it would also appear that some variants had longer downward angled ejector exhaust as well.
Thanks for the answers folks, I was thinking perhaps the siamesed exhausts were for a similar purpose to the tap off from the No5 cylinders on hurricanes for gun heating. Thinking along the lines of more guns and futher to travel = more heat required.. Probably stupid on my part but I never claimed to be clever.
By: Mark12 - 22nd January 2011 at 19:59
Bifurcation x3 😉
Mark
By: MerlinPete - 21st January 2011 at 17:11
I don’t think the ‘heat’ theory is strictly true.
As DC says, on the single-stage Merlin aircraft there physically wasn’t room for 6 stubs on the inboard side of each engine due to the proximity of the radiators, hence the use of a bifurcated stub covering the rearmost 2 exahust ports. I believe the same bifurcated stub was also used on the outboard side of the engine (even though there is room for 6 stubs on that side) for commonality reasons, i.e. the same stubs etc. can be used for either engine. Having said that I believe Australian built aircraft did have 6 stubs on the outboard side on single-stage engined aircraft, which negates the idea that the heat needed to be kept away from the wing. Not sure how many aircraft that’s true for though?
As you say Pete the two-stage engines were longer so there was room for 6 stubs on each side and I presume these were also common to port and starboard engines.
Remember. the Mosquito was quite an ‘economic’ aircraft in that several components were designed to not be handed and could be fitted to either side of the aircraft – undercarriage units and tailplanes being the obvious ones – so the use of common stubs would fit with that methodology.
That makes sense, I have since looked at some photos and the leading edge carrying the radiators is much further forward and does not seem to allow for all six stubs on the single-stage types at least.
Also, I didn`t read Mikes post properly, re same marks with / without flame dampers, so that is a true idiot answer in fact!
Pete
By: MarkG - 21st January 2011 at 11:11
Idiotic answer No1:
Apparently (because I`ve not seen it in any actual manuals etc) The siamesed rear stub was used on “short Merlins” ie single-stage, in order to keep the heat away from the wing leading edge. The two stage engines were further forward due to the longer supercharger at the back.
I don’t think the ‘heat’ theory is strictly true.
As DC says, on the single-stage Merlin aircraft there physically wasn’t room for 6 stubs on the inboard side of each engine due to the proximity of the radiators, hence the use of a bifurcated stub covering the rearmost 2 exahust ports. I believe the same bifurcated stub was also used on the outboard side of the engine (even though there is room for 6 stubs on that side) for commonality reasons, i.e. the same stubs etc. can be used for either engine. Having said that I believe Australian built aircraft did have 6 stubs on the outboard side on single-stage engined aircraft, which negates the idea that the heat needed to be kept away from the wing. Not sure how many aircraft that’s true for though?
As you say Pete the two-stage engines were longer so there was room for 6 stubs on each side and I presume these were also common to port and starboard engines.
Remember. the Mosquito was quite an ‘economic’ aircraft in that several components were designed to not be handed and could be fitted to either side of the aircraft – undercarriage units and tailplanes being the obvious ones – so the use of common stubs would fit with that methodology.
By: Arabella-Cox - 20th January 2011 at 21:29
Mossie shrouds
I have heard that the shrouds caused quite a lot of drag and were deleted from most early RAF Mossies. Possibly they were only then used on the NF’s, the day bombers and such didn’t use or need them?
We seem to have lost them early on, on UK Mossies. However, the Australian FB.VI’s still had them in 1945.
Anon.
By: MerlinPete - 20th January 2011 at 21:08
Idiotic answer No1:
Apparently (because I`ve not seen it in any actual manuals etc) The siamesed rear stub was used on “short Merlins” ie single-stage, in order to keep the heat away from the wing leading edge. The two stage engines were further forward due to the longer supercharger at the back.
Idiotic answer No2:
Flame dampers are generally associated with night fighter variants. They are not emplayed on all types because it is possible to get greater ejector thrust with other types, and possibly simplicity, so they cost less to manufacture?
Pete
By: TempestV - 20th January 2011 at 21:07
Well, I can answer for the 6 exhaust ports into 5 question.
On the Mosquito and Hornet the rearmost pair of exhaust ports were bifuricated into a single pipe, as if the last pipe was set at the same angle as the rest, it would have clashed with the radiator intake.
For the mix/match types of exhaust, it may be for several reasons:
– Flame dampers on nightfighters/bombers should have been fitted on both sides, but I have seen post-war Sea Hornet Night fighters with only the inboard flame dampers fitted to preserve the pilots night vision, I’m told!
– only a limited number of a/c sets were available?
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January 20, 2011 at 8:42 pm