The Revolution Will Not Be Televised wrote:

On Mon, 18 Aug 2003 20:39:22 GMT, Guy Alcala
wrote:

Let's just say my reply has been delayed, but here goes.

[snip more gratuitous and unprovoked logical discourse. NB all
gallons referred to in this post are Imperial, not the inferior Yanqui
oppressor's titchy competitive effort.]

[Quill on longitudinal instability on Mk Vs]

snip

Much like the behaviour of the actual Mk IX/XVIs with rear-fuselage
tanks in 1945.

True, but those Mk.IX/XVIs also had extra fuel in the regular fuselage tanks (ca.
94-96 gallons, depending on the source) forward of the datum.

66 or 75 gallons according to the Pilot's Notes and Shacklady &
Morgan.

I was referring to the increased tankage forward of the firewall.

And correct me if I'm
wrong, but ISTR that only those a/c with cut-down rear fuselages got the aft tanks;

Nope: the standard fuselage versions actually got larger internal
rear fuselage tankage - 75 vs 66 gallons. At least that's what the
Pilot's Notes say. [BTW, the VII/VIII/PR.X Pilot's Notes have some
range/climb/cruise graphs which I think might be relevant to this
discussion]

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. For instance, here's a post from a couple of years back on this
subject:
------------------------------------------------

The Pilot's notes state the following tankage:

The Spitfire 1/II/V had 85 gallons of internal tankage, in two tanks
behind the engine and in front of the pilot. Additional fuel was
carried in 30, 45 or 90 gallon "slipper" tanks under the fuselage.
These were in common use after 1941.

Early Spitfire IX's had the same internal tankage, while at the end of
1944 a further 75 gallons of internal capacity in rear fuselage tanks
was provided. This caused CoG problems as described, but in reality
they seem little worse than those experienced in USAAF Mustangs using
a similar rear-tabkage arrangement. 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). Also, late
production Spitfires had the leading-edge wing tanks used in the Mk
VII/VIII for an additional 26 gallons of internal capacity. From
mid-1944, the existing slipper tanks were augmented with longer
"torpedo"-shaped drop tanks with a 50 or 90 gallon capacity.
Spitfires operating in 1944 seem to have used the latter tanks very
frequently, judging by the photographic evidence.

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. Later Mark XIV and Mk XVIII Spitfires had
rear fuselage tanks, either of 62 gallons capacity.

Early Mark XIV's (examples in the RB-serialled series at least) did
not have rear tanks, and seem to have had Mark VIII-arrangement (with
reduced forward tankage capacity previously mentioned) and I suspect
the rear fuselage tanks only arrived with the later production Mk XIVe
models, again after mid-1944.

Some examples of
the Spit V had a smaller rear tank, though I believe this was used for ferry
only.

That's correct. The CoG issues were regarded as insurmountable until
larger tail surfaces arrived with the Mark VIII and later-production
Mark IX's. This is a bit suprising as the Mark V rear-fuselage ferry
tank carried 29 gallons, while flight testing of a Mark IX with the 75
gallon rear-fuselage tank indicated that the lateral instability
associated with the extra tankage eased considerably after 35 gallons
had been used, taking the remaining capacity close to the earlier 29
gallon tank level. This of course is a comment made in ignorance of
the physical positioning of the tank, which would have the biggest
impact on the CoG and consequent stability of any one factor.
--------------------------------------------------------

You may recognize the poster's style, although he's since undergone a revolutionary
reincarnation ;-)

snip

The Mustang could only
retain a fraction (ca. 25-50%) of that rear tank fuel to use for combat without being
dangerously unstable, with the contemporary Spit possibly (probably?) being unable to
retain any of it;

Actually, the relevant testing in January 1945 revealed that the
acceptable manoevering limit with the 75-gallon rear fuselage tank was
9.9 inches aft of the datum, or after 34 gallons had been used.
Clearly the tank didn't need to be emptied for this to be achieved.

at best, it could retain the same fraction as the Mustang. The
Mustang with rear tank didn't have 269 U.S. gallons to fight and return on; it had
somewhere between 205 and 227, depending on what fraction of the aft tank capacity
allowed acceptable combat handling.

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?


To be an acceptable long-range escort, the Spit still needed the extra forward
fuselage fuel of the later Mk. IXs and the Mk. VIIIs, plus the leading edge tanks of
the latter. The Mk. VIII carried 124 Imperial gallons internally (149 U.S), ALL of
which was usable in combat, plus whatever extra fuel usable in combat (if any) a rear
tank provided.

Ah, here we disagree: as far as I know, most IX/XVIs didn't have
enlarged forward tanks (in the traditional position forward of the
cabin bulkhead, behind the engine), and most MK VIIIs seem to have
been similar. So the best reliable figure for the internal capacity
of the Mk VIII would actually be around 110 Imp galls. I suppose Air
Commodore Alcala, Director of Fighter Operations in this scenario,
will be pressing the Air Member for Research and Development to get
them all with the enlarged forward tanks as well....

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. 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,

http://www.fourthfightergroup.com/ea...9tactical.html

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."


[increased tankage of 2 Spits IXs from Wright Field, July 1944]

In the case of the Spit wing it seems to have been a strength issue, at least
according to Quill

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).

. So I
suggest basic experience of rear-fuselage tankage, and measures to
combat the worst CoG issues resulting were at hand in plenty of time
to have an impact on the postulated fitting of rear-fuselage tanks in
the summer of 1943.

The difference being that the flights to Gibraltar were ferry flights, and no
formation maneuvering or combat flying with the aft tanks full was required.

Sure, but how different is this from Vcs emptying them on the climb
out of East Anglia and the cruise out to Holland? The short-ranged
Spit Vs and IXs could handle combat in those areas, while the LR Spits
would be briefed to pick up their escorts further out over the Zuider
Zee. Giving them an extra 30-45 minutes of flight on internal fuel,
even with the most restricted utility (e.g. only on the way in, no
combat endurance to remain after entering combat) is still of use, and
reflects the utility of giving them drop-tanks to start with. The
final determinant is the distance over enemy territory a Vc could
return on forward tanks alone after exhausting the rear tank, dropping
the 90-gallon drop-tank and spending 10 minutes at high throttle
settings in combat. This is obviously *not* a profile which makes it
contender for deep-penetration escort, but it still means they should
be able to operate out across Holland beyond Amsterdam and up to the
German border. Even a marginal improvement like this would have had a
real and clearly-observable benefit in supressing bomber losses.

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. zemek says that average fuel
burn on escort missions was around 200 gal./hr., giving them at most about 90 minutes on
internal fuel (this is with some combat allowance). Only when the D-25 and subsequent
models entered service with the 65 gallon rear fuselage tank did the extra external fuel
give an increased radius. Presumably most of this 65 gallons was usuable within Cg
limits. Since it took quite a while for them to replace all the earlier models, even in
the 56th, the extra radius couldn't be used for a long time.

In the end, even the RAF cleared the rear-fuselage tanks for
production usage in 1945, and they were happy enough to fit half of
the tankage in the FR XIV and the full thing in the XVIII.

Again, both a/c with cut-down rear fuselages.

Yes, but the cut-down fuselage doesn't seem to be a factor in deciding
whether a Spit got rear-fuselage tanks or not: the IX and XVI with
conventional fuselage got them, the FR XIV got them and I suspect the
XIV would have got them if it hadn't been succeeded on the production
lines by the XVIII in 1945, which only came in a cut-down fuselage
version. As it was, the example of the FR XIV and the IX/XVI
indicates the cut-down fuselage actually had a lower capacity for
rear-fuselage tankage (66 vs 75 gallons).

See the two-year old post above, which indicates measures to move the fuel and Cg forward
on these a/c.

Getting to our respective readings and
conclusions on Quill, I note that he says in the case of the Mk. 21 that he disagreed
with A&AEE on whether the Mk. 21's handling was acceptable at a certain point, and
that he felt that such handling deficiencies could be accepted to get an a/c with
superior performance into the field (he's also man enough to admit that he may have
been overconfident by this point that average squadron pilots wouldn't have had
serious difficulties, based on his own skills).

I suspect A&AEE were right on that point; but it's instructive to see,
yet again, that Quill states a fix for the stability and trimming
issues that plagued the F.21 in 1944 was known about (enlarged tail
surfaces), but production issues ruled it out until 1945. Take the
MAP monkey off Supermarine's back, demanding production at the expense
of development all the time, and this and a lot of other relevant
problems could have been dealt with earlier.

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? 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).

Now, it may just be a question of him
not thinking to mention it, or the way he worded it, but he maentions no such
disagreement between himself and A&AEE regarding the handling of the rear fuselage
tank-equipped a/c; he just says that the handling wasn't acceptable for a long time,
and required a lot of development.

The origin of the "acceptability" comments over the rear-tank tests
appears to be Supermarine's development testing. Aircraft would only
go to A&AEE after they had arrived at what they saw as a production
standard (e.g. Quill testing the 75 gall RF tank in July 1944, but
Boscombe Down not getting it for another six months). Also, note that
the A&AEE testing was not a peacetime acceptance test as such - the
aircraft and fittings involved were often ordered into production
anyway to minimise delays to production totals, and A&AEE testing was
often being performed as representative of current or imminent
production. F.21's were actually being produced before and after
A&AEE first critically reported on them.

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.


I'm certainly not going to claim, based on such flimsy evidence, that this is
definitive proof that the a/c couldn't have been flown in operations with an aft tank
with accceptable handling much earlier given sufficient motivation, especially given
your comments re the prevailing attitude of the A&AEE. But I do think it at least
suggests that the Cg problems were real and agreed to be so by both the A&AEE _and_
Quill. And that's as far as I'm prepared to gaze into my crystal ball. Your reading
may well be different.

And it is, I'm afraid. A&AEE seem to get their first rear-tank Spit
in January 1945, and quantify it as acceptable once 34 gallons out of
the 75 were used. Nobody was going to Boscombe Down and pushing this
idea, the whole issue seems to come from Supermarine. Posit a burning
interest in the Air Ministry in increasing inernal tankage in 1943
(e.g. ACM Kramer getting upset) and I suspect things would have been
remarkably different.

Pete and I certainly hoped that would be the case, although I don't know that the rear
tankage was critical. As long as we could get standard Mk. VIIIs (or LE-tank Mk. IXs) for
the initial day transition period (France/Low countries/Ruhr/German coastal targets), if
the Spit aft tank was taking too long Mustang production would probably cover our needs (as
well as those of the U.S.) by the time we were ready to go deep. And then we'd be on the
continent, and it would become almost a non-issue.

snip

then either expanding Mk.
VIII production at the cost of the Mk. IX

That would have been possible, but only at the point of converting
Castle Bromwich over to the VIII in the summer or autumn of 1943.
This needs a demonstration of the effectiveness and need for it
somewhat earlier: hence my LR Vs in 12 Group in July.

See Pete's post Mk. V Cg range.


or (if possible) transitioning to Mk. IXs
with the extra leading edge tanks of the VIII, with aft fuselage tanks and whatever
airframe mods required to pack usable _combat_ fuel in.

That would have required prducing the VIII wings & airframe, I
believe, rather than stuffing a Merlin 60-series into a Vc airframe as
was done to churn out IXs. So I think there would be production
infrastructure issues.

As it was, the Supermarine production group
around Eastleigh delivered about 90 Mk VIIIs to the RAF in July 1943,
which should be enough to prove the concept if you grab them all.

That's what we want, say 6 squadrons worth of Mk. VIIIs to start with.

Sure, and that with an aft tank was next on the agenda after boosting production of
the standard Mk. VIII/leading-edge tank Mk. IX. Either of the latter should have given
us an escort radius of 250-300 miles.

See my note on the actual forward-tank capacity of most VIIIs.
Although this may have been changeable.

And see my comments.

Unfortunately, a similar chart for a Mk. V doesn't seem to be available on the site,
but I have my doubts that the Mk. V was carrying around any such ballast in 1943, or
if it did, so far aft. Of course, AB197 was a very early Spit IX (the report date
seems to be June 10th, 1942), so that ballast was probably reduced as more operational
equipment was added, but it at least suggests (combined with the Mk. V's further aft
Cg vs.the Mk. IX as reported in various tests on the site) that the Mk. V was pretty
much at the limit, while the Mk. IX had considerably more Cg range available.

I can't find anything to substantiate this with the V myself, and I
understand the validity of your reservations. Nevertheless, the
critical issue as I see it is whether any rear tankage could become
available given improvements in the CoG by means of the enlarged
elevator horn balance and convex Westland elevator. I fully accept
this would, in all probability, have been insufficient to allow a 75
gallon rear-fuselage tank to be carried and cleared for combat. The
critical issue is whether this would have been enough to permit a
rear-fuselage tank to be used in the early stages of flight to extend
the pre-combat range. Given that this was done with a 29 gallon rear
tank, I think there is a useable margin, albeit a smaller one than a
LR-fitted Mk VIII with better weight distrubution and enlarged tail
surfaces would have.

See Pete's post, which seems to confirm my reservations.

I'm focusing on using the V not because it had more or even
comparitive utility with the Alacal/Stickney LR Mk VIII (something
I've argued for in the past myself), but because even with the greater
constraints involved, it was a more likely concept-demonstrator in the
historical timescale. If you want an overnight conversion to LR Spit
IXs at any given point without the example of a LR operational trial
in the RAF to start with, you'd have to posit the removal of most of
the higher command and their staff involved to eliminate their
existing preconceptions and prejudices.

Well, we're already postulating that Winston has tossed most of the CBO out the window and
told Butch to knock off most of the area bombing and switch to days, so existing prejudices
have already been overturned. There'd still likely be a rearguard action, but it would be
difficult to sustain when those 'action this day' prayers start being delivered to Portal
on down.

So this is why I think LR Vs would be an issue worth consideration
even taking into account their inferiority from all aspects of the job
when compared to the VIII. I think it's more credible to posit
changes in the Vs proving the concept, as this would be more
institutionally tolerable. This is important from my point of view,
as I think any counter-factual speculation has to be made within the
known constraints of the industrial, economic and institutional
context to remain credible.

I accept the idea, but retain my caveats over Cg, now strengthened by Pete's comments.

[production pressures]

I don't underestimate the pressures, I just think (as you mentioned a few paragraphs
above) that if the decision had been made to go over to daylight, fighter range
extension would have increased in priority and changes would have to have been
accepted, whatever the disruption elsewhere. Because otherwise, it wasn't going to
work.

Indeed, but when the RAF actually faced this dilemma, at the end of
1939 and then again in spring 1941, they abandoned daylight bombing.
The two concepts had become divorced, for understandable external
reasons, and asserting a sudden and complete reversal of this is
stretching the credibiluity of the institutional appreciation involved
in the speculation.

Now I think the concept is possible, and a valid piece of historical
speculation, but I also think it has to work within the context
involved, and, frankly, anybody demanding a reduction in Spitfire
production in favour of speculative operational development was on a
losing wicket. The British strategical position in this respect can't
be overstressed too much: the USAAF had a doctine and institutional
ambition towards independence which was served by the 8th AF campaign,
secured by other forces doing things like protecting their bases and
dealing with the existing war against Germany. They had room to stop
and rethink tactics and strategy, and change production priorities
accordingly.

The British did not have this space. They had to maintain existing
commitments and fight the war as it existed from a smaller industrial
and economic base closer to the enemy threat. Proving strategic
concepts, even ones which had great war-winning potential, was a
luxury that could not come at the expense of the means for repelling
the enemy in the meantime.

The RAF could not prejudice production of their main fighter when it
was needed for home defence, operations in the MTO and Far East and
supply to the Russians. The difference between these commitments and
facilitating daylight strategic bombing was the difference between
fighting the war and demonstrating an abstract concept. Whatever
happened in the skies over Germany, Fighter Command were conceiveably
in a position to lose a war for national survival. The 8th AF wasn't.
No lack of respect intended. The 8th might prove vital in winning the
war, but high Spitfire production was known to be needed meanwhile to
avoid defeat and stay in the war, which was an essential prerequisite.

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. 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. If nothing else, we could have
produced more P-39s/P-63s, which in any case were etter suited to conditions on that front.

snip areas of agreement or mild disagreement

Please desist from this moderate rationality or I will complain to
your ISP.

Did I mention that I have INCONTROVERTIBLE PROOF that the U.K. government has been
testing UFOs ( and dissecting ALIEN CORPSES) at their base at Machrihanish,

Nah, you're just confusing Alien corpses with the average westie.
Understandable mistake. We only retain them to give the midges a
round-the-year locally-available food supply until the German tourists
appear in the summer.

cleverly
disguising test flights of same as those by Aurora and, in times past, SR-71s? Wait,
I hear the black helicopters coming to get me. I can feel the beams as they try to
alter my brain. Excuse me while I done my tinfoil hat.

Interesting theory, although it lacks credibility, until we
acknowledge the critical role played by the Templars and the
Illuminatii in the Ministry of Aircraft Production in 1942 [censored]

That would explain the Templars' intimate knowledge of Spitfire fuel tankage, as reposted
well above ;-)

Guy