The Revolution Will Not Be Televised wrote:
On Wed, 20 Aug 2003 08:42:55 GMT, Air Commodore Guy Alcala, Director
of Fighter Operations wrote:
Isn't rapid promotion in wartime wonderful? And to think, I was just a lowly Wing Commander on
Butch's staff a month or so ago, along with then Group Captain Stickney.
snip
Yes, you're right about the aft tanks. OTOH, those a/c with cut down rear fuselages also
had increased forward fuselage fuel and in some cases leading edge tanks (according to
several sources which I take to be credible), and I think larger horizontal tails, so
clearly they wanted to move the Cg back forward again (more fuel forward, less aft) and
improve the stability.
Ah, but the tankage juggling didn't happen quite as sequentially and
in such a comprehensive fashion. These things were much more
piecemeal than an overall summary makes them appear. A comprehensive
history of the modification states at and after delivery of all
Spitfire models would be nice, but frankly it seems like a task better
left to candidates for extensive residence in purgatory.
Reviewing some of the "here they are, now they're gone" tank capacities in the A&AEE test
reports on the 4th FG website, I'm beginning to think you're right.
For instance, here's a post from a couple of years back on this
subject:
Well, this chap seems to talk some sense for once in this
thread....[cough]
In late model Spitfires with
tear-drop canopies (late '44 production), the front tankage was
increased to 95 gallons while the rear fuselage tankage was reduced to
66 gallons (for roughly the same total tankage).
That's not entirely true, although I do enjoy the rueful pleasure of
hoisting myself with my own petard. I don't think it's possible to
definatively state that all RF-tanked Spit IXs had increased forward
tankage. There's no reason this can't be the case in the ATL we're
considering, though.
The Spitfire VII & VIII formed the airframe basis for the later
production Spitfires, and apart from some early Mk XII Spitfire's
converted from Mark V's, all Mark XII and Mark XIV Spitfires had
similar tankage arrangements of 96 gallon forward internal tanks and
26 gallons in wing tanks.
Again, this seems to be out, based on my understanding as it has
evolved over the past couple of years.
Indeed.
--------------------------------------------
AFDU Wittering July 1943 Spitfire XIV JF317
SHORT TACTICAL TRIALS OF EXPERIMENTAL SPITFIRE XIV
INTRODUCTION
On instructions from Headquarters, Fighter Command, an experimental Spitfire XIV JF317 (Griffon
61) was made available by
A&AEE for three days for short tactical trials. The trials took the form of a direct comparison
with a Spitfire VIII (Merlin 63)
JF664, and flying took place from 27 to 29 July 1943.
BRIEF DESCPRIPTION
The aircraft used is a conversion of the Spitfire VIII. The larger engine involves a much longer
engine cowling and the extra
weight forward has been balanced by ballast in the tail. The fin has been increased in area to
help directional stability and a
large rudder is fitted. This aircraft had the normal span wings of the Spitfire VIII with small
span ailerons, but the extended wing
tips had been replaced by the standard wing tips as on the MK IX. The engine is not
representative of production as the FS
gear is higher and the MS lower. A five blade propeller is fitted. The engine had a Bendix
injection carberator and boost for
combat is limited to plus 15 lbs. The Spitfire VIII weighed 7,760 lb, the XIV 8,376.
snip
Range and Endurance- Both aircraft carry the same amount of fuel (96 gallons in the main tank
and 27 gallons in two wing
tanks.) Refueling checks made to compare consumption showed than when the two aircraft stayed
together throughtout the
trials, the Griffon engine was using approximately 10-15 gallons more fuel per hour than the
Merlin.
-----------------------------------------------------
So it appears that the "standard" Mk. VIII as well as the Mk. VIII(G) conversions did indeed
have an internal capacity of 123 gallons, as early as July 1943. But then the weight and
loading data for the second _production_ Mk. XIV, RB. 141, dated 15 Dec. 1943, state that it has
112 gallons, 85 in the fuselage (i.e. the original fuselage tanks) plus the 27 in the wing L.E.
Just to confuse things, there's the later test below:
-------------------------------------------------------
INTRODUCTION
1. In accordance with instructions from Headquarters, A.D.G.B., tactical trials have been
completed on Spitfire XIV. Aircraft
No. RB.141 was delivered to this Unit on 28.1.44 for comparative trials with the Tempest V. It
was discovered that this
aircraft was not representative of production aircraft for Squadrons, and Spitfire XIV No.
RB.179 was made available and
delivered on 25.2.44. The operational weight with full fuel and ammunition is 8,400 lbs. To give
a clear picture to the greatest
number, the Spitfire IX (maximum engine settings +18 lbs boost, 3,000 revs) has been chosen for
full comparison, and not the
Spitfire XII which is a low altitude aircraft built only in small numbers. Tactical comparisons
have been made with the Tempest
V and Mustang III, and combat trials have been carried out against the FW 190 (BMW 801D) and Me
109G.
snip
TACTICAL COMPARISON WITH SPITFIRE IX
13. The tactical differences are caused chiefly by the fact that the Spitfire XIV has an engine
of greater capacity and is the
heavier aircraft (weighing 8,400 lbs. against 7,480 lbs. of Spitfire IX).
Range & Endurance
14. The Spitfire XIV, without a long-range tank, carries 110 gallons of fuel and 9 gallons of
oil. When handled similarily, the
Spitfire XIV uses fuel at about 1 1/4 times the rate of the Spitfire IX. Its endurance is
therefore slightly less. Owing to its higher
speed for corresponding engine settings, its range is about equal. For the same reasons, extra
fuel carried in a long-range tank
keeps its range about equal to that of the Spitfire IX, its endurance being slightly less.
------------------------------------------------------------
Now, was that 110 gallons a misprint, a rough rounding (seems unlikely), representative of the
"standard" production a/c (details of differences not given) as opposed to the "non-standard"
RB. 141, or just Supermarine fitting in whatever tanks they happened to have on the shelf on any
particular day?
Later Mark XIV and Mk XVIII Spitfires had
rear fuselage tanks, either of 62 gallons capacity.
Note that the FR XIVs, with cameras in place of one of the RF tanks,
still had the second 33 gallon tank. I think RF-tanked Mk XIVs can't
be dismissed out of hand. But one maniacal idea at a time.
Brng it up again and it's off to Wandsworth with you, for sabotaging the war effort.
You may recognize the poster's style, although he's since undergone a revolutionary
reincarnation ;-)
Via a publically-acclaimed stint as a German emperor's hairstyle...
Nonetheless, it's a reasonable summary but I think the forward tank
size is probably not representative. The Pilot's Notes for the Mk XII
give a standard 85-gallon forward tankage, the PN's for the F.21 give
it the same tankage and ditto for the Mk XVIII.
Interestingly enough, the tactical test of the Mk. XII EN. 223 in Dec. 1942 includes the
following comment:
-------------------------------------------
Flying Characteristics
5. In the air the handling of both EN.223, and another production Spitfire XII which was made
available by Supermarine for one day, were felt to be far superior to the normal Spitfire IX or
VB, being exceptionally good in the lateral control which is crisper and lighter due to the
clipped wings. The longitudinal stability is much better than that of the Spitfire V, and in the
dive it was particularly noticed that when trimmed for cruising flight, it stays in easily at
400 m.p.h. I.A.S., and does not recover fiercely. In turns the stick load is always positive and
the control very comfortable.
-----------------------------------------------
Also "It is fitted with facilities for beam approach and about the first seven, including the
aircraft on trial, have the oil tank behind the pilot. This is not acceptable operationally and
subsequent aircraft will have the oil tank mounted immediately aft of the fireproof bulkhead.
The fuel capacity is retained at 85 gallons, and jettison tanks can be used if required."
Moving the oil tank forward would of course shift the Cg in the same direction, boosting the
stability even more.
Both of the latter
were definative production versions, with plenty of time to include
larger forward tankage in the production lines if it had been decided
upon as a production version requirement.
The PN's for the VII/VIII/X do refer to an increased 96 gallon forward
tankage, so you're right and it would be valid for the Merlin LR Spit,
but not for the Griffons, I suspect.
So it seems, from the Mk. VIII/conversion Mk. XIV test quoted above, and the various Mk. XIV
prodution tests..
In this case we have a Mk IX with 85 gallons internal forward tanks
and about 40 gallons in the rear tank within apparently tolerable
limits for combat.
With which tail, and did the a/c have leading edge tanks?
Vc tail, no leading edge tanks. I think we can summarise on a LR Spit
VIII having the following:
96 gallons internal forward tanks (47 and 49 gallons)
25 gallons internal wing tanks (two 12.5 gallon tanks; conservative
figures used)
The Spit VIII srs ii a.k.a. Spit LR VIII gets this extra -
75 gallons internal rear fuselage tank.
This gives a potential internal fuel capacity of 196 gallons, with a
further 90 available from external slipper or drop tanks. How this
translates to range might be worth exploring. Much of this is pure
conjecture on my part, I should add, and please correct me if you have
a better idea of the figures involved.
The PN's for the VIII give an allowance of 9 gallons for run-up and
take-off. That should be out of the rear tank.
Depends. For safety reasons it's more likely to be from one of the main tanks, so as to avoid
any fumbling during takeoff if there are feed problems. I'm assuming that all the drops, aft
fuselage and L.E. tanks all feed into one of the main tanks, like the Mustang. I don't know the
details of the Spit's fuel plumbing.
Climbing at 160 IAS (if I'm assuming this correctly from the curves
given) should take perhaps 15 gallons and maybe 15 minutes to 25,000
feet on a low revs weak mixture. The performance curve I'm looking at
only covers a clean aircraft, so an extra 5 gallons or so to cover the
higher weight might be reasonable. I'm assuming wing rendezvous and
assembly could be done on the climb phase, if not let's assume another
5 gallons. This knocks off 34 gallons from the rear tank, and should
mean the aircraft is reasonably stable when they depart the English
coast.
I imagine the rest of the profile would be flown at a low-revs,
high-boost weak mixture cruise. That could go down to 1,800 rpm, but
then there's the tactical need to maintain a high airspeed. I suggest
your wing commanders cruisie at 2,200 rpm and +4 boost, for a
consumption of 61 gallons per hour. That should give about 6.5 air
mpg, or maybe 6 when the drag of the external tank is taken into
consideration.
What kind of air speed does that give you? Zemke says that they normally cruised at maybe
210-220 IAS on Rodeos (doesn't say specifically what the cruise was on Ramrods), giving 320-325
TAS at escort altitudes.
There obviously needs to be a contingency reserve on the internal
forward fuel, maybe 10 gallons as a minimum. This gives us 24 gallons
in the wing tanks, 86 usable in the forward tanks, 41 left in the rear
tanks and 90 in the drop tank. The priority would be to expend fuel
in the tanks which cause performance degredation, so the rear and drop
tanks would have the priority. We'd have to assume a minimum of 10
minutes at full combat settings for the engine, which at +18 lbs and
3,000 rpm (even if it might not attain this in high-altitude combat, I
want to be conservative). At 150 gallons per hour, this means as much
as 25 gallons being used in combat, and this must come from the
internal fuel.
So the internal fuel situation is looking like 34 gallons for climb
and assembly from the rear tank, a 10 gallon reserve from the front
tanks (the last to be emptied and the ones you'd be on when stooging
about East Anglia in the fog desperately seeking somewhere to land)
and 25 gallon allocation for combat from the same tanks.
This leaves 41 gallons in the rear tanks and 76 gallons in the wing
and forward tanks, not including 90 in the drop tank.
The remaining 117 gallons of internal fuel should give a still air
range of about 700 miles, or about 350 miles radius under good
cruising conditions. The 90 gallon tank should give a further
still-air range of 500 miles or so, but none of that can be relied
upon as it will be jettisoned at the first sing of combat. The range
on internal fuel is more impressive than I thought. The drop tank
would be useful getting across the North Sea, and as the USAAF
demonstrated, could be held on until German fighters were spotted long
past the enemy-held coast, and so the internal fuel would really only
be needed for combat and returning from combat.
If these figures (admittedly from a "back of fag packet" provenance)
have any pretence at being representative, it seems the Director of
Fighter Operations (Air Commodore Alcala) and the Air Member for
Research and Development (AVM Stickney) might be on to something here.
The Spit LR VIII might well have been very useful as an
intermediate-range escort.
I think some of your assumptions are a wee bit optimistic for Wing-size ops, but agree with the
general tenor.
Every source I have implies or claims that all Mk. VIIIs had the bigger forward fuselage
tanks, but I'm willing to be convinced otherwise.
I'm not going to push that angle: it seems a reasonable enough
assumption on the basis of the evidence I have.
But the tank size increase, according to
a different poster from a couple of years ago, was something that could be done on any Mk.
VIII or IX -- the space was always there, it just hadn't been used. Oddly enough,
Some IXs did get it, but I can't discover the logic or process
involved at this stage.
I increasingly wonder if it was a matter of "whatever the subcontractors deliver today." Any
idea who made the internal tanks (if not Supermarine), and if there was more than one company
involved?
which contains the tctical trial data for AB 505 from April 1942, (i.e. prior to the
testing of AB 197, which had the usual 85 gal.), states that
"25......... The fuel capacity of the Spitfire IX is 92 gallons, 57 in the top tank and 35
in the bottom tank. This is 10 gallons more
than the Spitfire VC."
That's interesting, as it's not the actual VII or VII forward tank
profile (47 gallons top and 49 gallons bottom). This might be an
unrepresentative example. I think the VIII capacity is plausible
enough, and they began production in November 1942.
Yeah, I have no idea where the 92 gallons comes from, or how it can be considered "10 more than
the Spit Vc."
Yes, but I suggest what Wright Field did was a reliable indicator of
what the USAAF would have done if Spitfire production and procurement
was within their grasp. A&AEE whinges about instability would get
short shrift in this situation.
Oh, I don't know. They found it impossible to increase the tankage of the P-39/P-63 for Cg
reasons, and those a/c certainly could have used it in our service (it didn't matter to the
Russians, but that was due to local theater conditions).
They did apparently stick a 43 gallon tank behind the pilot, which is
interestingly enough when we bear in mind the 75 gallon tankage
becoming tolerable after 34 gallons were used; i.e. taking it down to
41 gallons behind the pilot. I really think there is some valid
mileage there, especially since MK210, the aircraft in question had
normal Vc/IX tail surfaces, and not the Mk VIII extended tail which
would have improved stability further.
If the fuel in the external drop tank(s) is already roughly equal to the internal capacity
needed to return, as it was with the 90 gal. tank, adding extra internal fuel that can't be
used in combat does nothing for the combat radius, which is what we're interested in.
Zemke makes this point with regard to the carriage of 2 x 108 USG tanks on P-47s prior to
the D-25 models. All the earlier versions had 305 USG internal, and the switch from a
single CL 150 (nominal) USG tank to a pair of 108s did little or nothing to extend the
radius, although it did boost the endurance in the same area.
I appreciate the distinction, but pre-combat endurance at the range
limit is still an important advantage, especially in this scenario.
I'm not asserting that an LR Spit could replace the longer ranged
escorts like the P-38 and P-51. It could have moved out to
Thunderbolt-radius, and that would have been a major benefit. While
the early P-47 groups were complaining about range and endurance
difficulties, they still did a lot of good work within their
attainable radius.
Agreed. It seems that the break point in practice for radius extension is reached when the
external capacity is roughly 2/3rd of the (combat usable) internal. Beyond that you're just
boosting the endurance or ferry range.
snip
Certainly what we intended to do, with range extension pushed to priority one. Would you
happen to know what the production of Mk. VIIIs was in say October through Dec. '43, or
maybe Jan. '44, inclusive?
No, but the service acceptances by the RAF seem to be (by a hand and
eye count of the appendices in Shacklady & Morgan, so I can't claim
any real authority for these figures) about 90 in July 1943, 98 in
October, declining to 67 in November, 53 in December and 28 in January
1944. This doesn't reflect production figures per se, as the aircraft
had often been in storage for some time or were shipped to Casablanca
or India, and had actually been produced earlier. But it does give an
indicator of deliveries, which is almost what you want.
We're in fat city, then, and I see no need to mess around with Mk. Vs. The October acceptances
will allow us to form 3 squadrons immediately plus 50% reserves (ideally we'd want at least
100%), more than sufficient force for escorting the first 'Combat wing' of heavies we form in 3
Gp.
Bear in mind there was a minor changeover to Mk XIV production
(starting with 2 aircraft in October 1943, to about 7 per month in
December 1943) at this point. Otherwise the Eastleigh production
group under Supermarine were moving to producing Seafires and fooling
about with XVIII and F.21 development (which would take aeons to
culminate in a production version). The main production resource was
Castle Bromwich, which was churning out Mk IXs at this point.
I don't see why Mk VIII airframe production couldn't be extended and
maintained at about 90 per month. That should be enough to operate 9
squadrons (on 20 a/c i.e. strength, 10 per month per sqn to replace
losses) on a reasonable 50% per month wastage figure without even
touching CBAF. As tanks become available, the CBAF IXs can mutate
into VIIIs and then LR VIIIs.
Seems reasonable, although we'd want to boost Mk. VIII production well above 90/month, to allow
us to re-equip Fighter Command faster and supply the overseas squadrons. In the meantime, they
get the Mk. IXs that we're not replacing with Mk. VIIIs.
I'm thinking that a move like Arnold's (he gave the ETO _all_
P-38 and P-51 production for a three month period in late '43), giving Fighter Command all
the Mk. VIII production in that period, would be enough to get us going. The MTO and
everyone else will just have to accept Mk. VC Trops and/or Mk. IXs for a while longer (they
were already using them in any case).
Well, it looks like the real bottleneck is in fitting enlarged main
tanks, wing tanks and rear fuselage tanks to the IX. I don't have the
information to scale this into consideration, but I can't believe that
tank production couldn't have been expanded.
And Quill mentions that the F.21 a/c which A&AEE finally accepted had its handling much
improved over the original version he was trying to get them to accept.
Yes, they did: by early 1945, after production deliveries began in
August 1944. In my version of this scenario, after appointing myself
as Air Member for Production at the MAP and Air Council, I'm telling
Supermarine to continue Mk VIII production and move the F.21 onto the
back burner, although fighting for an allocation of Mk VIII airframes
for conversion to Mk XIV offset from Castle Bromwich beginning
production of LR Spit IXs with LR Mk VIII tankange to keep ACdr Alcala
and AVM Strickney quiet. This gives us an interim two-stage Griffon
version in service in February 1944 without all the dislocation caused
by the arseing about producing unusable F.21s in the short term.
An excellent plan.
Pete and I certainly hoped that would be the case, although I don't know that the rear
tankage was critical.
Maybe not as much as I thought, but still, let's go for it as a Spit
VIII series ii (Long-Range) standard to come in when possible. With
ACM Kramer in charge that might happen a lot sooner than in OTL.
Not to mention Winston pushing.
I don't agree that was the case by mid '43. Under no conceivable set of circumstances
could Fighter Command lose air superiority over the UK then.
Well, we know that now, and I'm sure some did at the time, but don't
underestimate the retentive power of the 1940-41 institutional and
beurocratic memories, and the impact of the production priorities
which were shaped then.
As it was, Fighter Command
was over-manned and equipped, and as you have yourself stated, under-utilized. What
happened in Burma and in the Italian campaign weren't going to decide the war, and the
Russians could have survived quite well without Spitfires.
I'd say so as well, but the political ramifications were not easily
dismissed. The Aussies, India Command, the DAF, the Americans and
Russians had all asked for and been promised Spitfire allocations
which were still required at the time. These all had to come out of
Mk IX production. I don't think this is as big a problem as I'd
initially assumed if the main bottleneck is building and fitting the
internal tanks: there was no need to stop production meanwhile, even
if there was a shortage of tanks to fit them all.
Ah, but we're doing a direct swap, giving them Mk. IXs instead of Mk. VIIIs, just for a few
months. As it is, 31st FG was flying a mix of Mk. Vs, Mk. IXs and Mk. VIIIs in Italy, so the
U.S. would just have to wait on the Mk. VIIIs for a while.
If nothing else, we could have
produced more P-39s/P-63s, which in any case were etter suited to conditions on that front.
I wouldn't disagree with that, but again, it's a judgement borne of
hindsight. Nobody was going to emerge successfully unscathed from a
Chief of Staffs meeting with Winnie present after voicing the
suggestion that Russian allocation of British fighters be cut
entirely.
Hey, they can have all the Mk. IXs they want.
That would explain the Templars' intimate knowledge of Spitfire fuel tankage, as reposted
well above ;-)
Wait till the German emperor's hairpiece turns up on Google with it's
own unique contribution to make. Have I mentioned Sabre-powered
Lancasters yet?
Yes, you have, oh spawn of the devil;-)
Guy
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