A Critical Analysis of the RAF Air Superiority Campaign in India, Burma and Malaya in 1941-45 (3 Viewers)
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With regard to the rear fuselage tanks in the Mk.VIII vs the IX/XVI is there not a much simpler explanation. It is not that it couldn't be done to a Mk.VIII but that it just wasn't worth the hassle as production was coming to an end anyway in Dec 1944 when all the flight testing of the rear fuselage tanks was going on.
Spitfire Mod 1335 is the modification of high backed Spitfires to include the rear fuselage tanks.
Spitfire mod 1414 is the same for low backed Spitfires.
The first LF.IX with the rear fuselage tank was ML186 which flew in April 1944. They were still testing it for CoG issues in Aug 1944, then Nov, Dec and into Jan 1945. Low back Spitfire XVI production seems to have begun around Feb 1945 with low backed Mk.IX a bit more of a mystery.
And as for CoG issues there seems to have been a lot more to consider than just the fuel tanks. This from the resident Spitfire expert (now sadly deceased) on Britmodeller in a discussion about the Mk.XVI posted way back in 2012:-
"The big thing about the XVI was that it was a sort of combination of "For want of a nail, a horseshoe was lost," and Burl Ives's "There was an old lady."
The Air Ministry wanted to fit them (and possibly all Spitfires) with the gyro gunsight, but the black boxes, etc., associated with the GGS, had to be installed before the extra fuel tanks were fitted.
The GGS also needed a completely new (first HOTAS?) throttle lever.
Fitting the fuel tanks displaced the compressed-air tanks, which had to go somewhere else; the tanks also affected the CofG, so the oxygen tanks had to come out of the back end of the fuselage.
The air and oxygen tanks had to go somewhere, so the outer .303" compartments were used for them, which meant that the wings had to be converted to E armament.
The extra flying time meant a need for a third oxygen bottle, with a central filling point fitted on the starboard cockpit wall.
Because the XVI was to be used for ground attack, wings had to wired for carrying bombs.
Bomb-carrying entailed the use of "stronger" (four-spoke) wheels, possibly torque links, as well, but that's uncertain.
Because of the extra strain, wingtips had to removed; this was not, as so often thought, a 10-minute job, but took 8 man-hours.
As well as needing the extra control of the elevators, the larger "Mark XII" rudder was also needed.
The fuel tanks filled the rear fuselage, so a Sutton harness couldn't be used, meaning a new (QL) harness with parachute-style quick-release box, and a strengthened seat to accept the new style of hip strap in a different position.
Originally, all of the work was allocated to a single M.U., but, as time went on, it's possible that it had to be further delegated (paperwork, so far, is not definite on this.) At the very least, the change to the E wing could not be undertaken at Squadron level, since it involved the removal, and blanking off, of heating and compressed air pipework. That, too, needed the "working parties," so it made sense to keep everything in the one unit.
Edgar"
In response to further queries he noted:-
"The metal elevators mod is/was specifically tied in with use of the rear fuel tank, which would have left "normal" aircraft equipped with the original fabric-covered type. The pointed rudder was also a "must" for tank-equpped aircraft, but not for others."
"...Both 1335 and 1414 are marked "S.O.O.," which means Special Order Only, so it's fairly safe to take this as not being 100% of production."
And on the need for the modification to add metal ailerons:-
"It was entirely designed for getting the heavily-laden XVI off the ground; there's evidence that (possibly due to 11 Group's objections) the mod was never incorporated into escort fighters (and that includes IXs & XIVs,) so the elevator mod would have been unnecessary."
And note that the Mk.VIII retained the 'C' wing armament throughout its production run. And it was fitted with shorter span ailerons than the MK.IX/XVI.
Spitfire Mod 1335 is the modification of high backed Spitfires to include the rear fuselage tanks.
Spitfire mod 1414 is the same for low backed Spitfires.
The first LF.IX with the rear fuselage tank was ML186 which flew in April 1944. They were still testing it for CoG issues in Aug 1944, then Nov, Dec and into Jan 1945. Low back Spitfire XVI production seems to have begun around Feb 1945 with low backed Mk.IX a bit more of a mystery.
And as for CoG issues there seems to have been a lot more to consider than just the fuel tanks. This from the resident Spitfire expert (now sadly deceased) on Britmodeller in a discussion about the Mk.XVI posted way back in 2012:-
"The big thing about the XVI was that it was a sort of combination of "For want of a nail, a horseshoe was lost," and Burl Ives's "There was an old lady."
The Air Ministry wanted to fit them (and possibly all Spitfires) with the gyro gunsight, but the black boxes, etc., associated with the GGS, had to be installed before the extra fuel tanks were fitted.
The GGS also needed a completely new (first HOTAS?) throttle lever.
Fitting the fuel tanks displaced the compressed-air tanks, which had to go somewhere else; the tanks also affected the CofG, so the oxygen tanks had to come out of the back end of the fuselage.
The air and oxygen tanks had to go somewhere, so the outer .303" compartments were used for them, which meant that the wings had to be converted to E armament.
The extra flying time meant a need for a third oxygen bottle, with a central filling point fitted on the starboard cockpit wall.
Because the XVI was to be used for ground attack, wings had to wired for carrying bombs.
Bomb-carrying entailed the use of "stronger" (four-spoke) wheels, possibly torque links, as well, but that's uncertain.
Because of the extra strain, wingtips had to removed; this was not, as so often thought, a 10-minute job, but took 8 man-hours.
As well as needing the extra control of the elevators, the larger "Mark XII" rudder was also needed.
The fuel tanks filled the rear fuselage, so a Sutton harness couldn't be used, meaning a new (QL) harness with parachute-style quick-release box, and a strengthened seat to accept the new style of hip strap in a different position.
Originally, all of the work was allocated to a single M.U., but, as time went on, it's possible that it had to be further delegated (paperwork, so far, is not definite on this.) At the very least, the change to the E wing could not be undertaken at Squadron level, since it involved the removal, and blanking off, of heating and compressed air pipework. That, too, needed the "working parties," so it made sense to keep everything in the one unit.
Edgar"
In response to further queries he noted:-
"The metal elevators mod is/was specifically tied in with use of the rear fuel tank, which would have left "normal" aircraft equipped with the original fabric-covered type. The pointed rudder was also a "must" for tank-equpped aircraft, but not for others."
"...Both 1335 and 1414 are marked "S.O.O.," which means Special Order Only, so it's fairly safe to take this as not being 100% of production."
And on the need for the modification to add metal ailerons:-
"It was entirely designed for getting the heavily-laden XVI off the ground; there's evidence that (possibly due to 11 Group's objections) the mod was never incorporated into escort fighters (and that includes IXs & XIVs,) so the elevator mod would have been unnecessary."
And note that the Mk.VIII retained the 'C' wing armament throughout its production run. And it was fitted with shorter span ailerons than the MK.IX/XVI.
Hi
The fitment of a rear tank in the Mk. V also meant a relocation of other equipment (from page 148 of 'Spitfire, The History':
Drawings from the same source show the location of the 29 gallon rear tank (plus the ferry drop tank fitment for the Mk. V):
Mike
No, not the firewall itself. A common aviation term is "firewall forward", meaning everything upfront: cowling, engine mount, engine, accessories, prop, spinner, and any ordnance mounted up there, with its ammunition. The reason I mentioned it was in reference to W&B concerns RE the aft fuel tank in various marks of the Spit. The Mk IX had a more potent supercharger setup than earlier Mks, which might imply more weight FwF, easing the tail heavy situation with the aft tank.
buffnut453
Captain
No. The MkX was taking design hints from the P-39 and had added nose armour.
I'll get my coat….
SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
Meet you outside.
Shortround6
Major General
MK IX used a heavy cabin heater?
buffnut453
Captain
On a more serious note, the MkVIII and onwards were slightly longer to accommodate the larger (in physical size) supercharger. Moving the mass of the engine even just a few inches forward will make a big difference in balance.
Every moment counts!
Shortround6
Major General
buffnut453
Captain
Maybe...but they clearly missed the standard RAF requirement for a second, superfluous, cabin heater. That's why the P-400 was such a success in RAF service....er....oh, wait....I think I've slipped into that alternate universe again.
MiTasol
1st Lieutenant
From the bigger engine
MiTasol
1st Lieutenant
The Mk IX was basically a Mk V with a bigger heavier engine
Shortround6
Major General
and bigger radiators
GregP
Major
I have it, and the speed for dropping tanks is not stated. It DOES say that the aircraft is restricted to straight and level flight when on drop tanks. My take on that is "more or less straight and level, but you can cruise climb and cruise dive with it as required for takeoff and landing." They talk a lot about how to operate the drop tanks and I was surprised to note things like, "when the engine cuts out, switch to main tanks ..." and the like. Seems like there was quite a bit of thinking about operating drop tanks. For instance, if you had the rear main tank and drop tanks on at the same time, you would vent the rear main tank fuel out of the aircraft! So, switching tanks involved turning on a tank and turning off a tank in specific order, and the engine cut out when a main tank ran dry as the sign to change to another tank!
I bet that REALLY got the pilot's attention!
I bet that REALLY got the pilot's attention!
In the flying club we had a Cherokee Six with four tanks and a Doyn Conversion Apache with six. Given the accuracy of old tired Piper fuel gages, if you didn't want to carry around up to 1/3 of your capacity as unusable fuel, you had to use the "stutter-switch tanks" method of fuel management. Maintaining balance required a conscious schedule of tank switching to stay out of "heavy wing syndrome". Fortunately, the Apache had header tanks with a noticeable slosh factor, which led to a decent interval of hiccuping before an engine would quit on you.
buffnut453
Captain
I think that's called a "feature".
The main reason the VIII didn't get the rear tank is that by the time the installation was in the works, the VIII had mutated into the XIV.
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