Re: Calling Guy Alcala: The Return of the Spitfire Mk VIII LR escort from Beyond the Grave

My tardiness in replying has saved me a lot of typing, as Geoffrey has made many of
the points I would have.

Admiral Sir Francis Haddock wrote:

> On Sun, 20 Nov 2005 18:32:14 +1100, "Geoffrey Sinclair"
> <gsinclairnb@xxxxxxxxxxxxx> wrote:
>
> >What about fuel reserves?
>
> No planned, literally. I think the margin for reserves, such as it
> is, comes out of the 15 minute combat rating and the assumption that
> the cruise consumption all the way out and all the way back could be
> reduced for a reduction in TAS.
>
> >The 23 gallons allocated to climb, assuming 1.1 gallons per minute,
> >yes I know this is wrong, would leave the Spitfire around 20 to 30
> >miles from the airfield it took off from.
>
> 30 miles, I estimate, but this might be consumed by high-level
> assembly and meeting the bombers.

Since we are talking about high level heavy bomber escort (well, as high as we can get
with single-stage engines), I think we should assume the same conditions that the
USAAF escort radii given in Dean call for, to wit: climb to 25kft with no allowance
for distance; cruise out (and back) at 210 IAS at 25 kft; 5 min.WEP and 15 min. mil.
power combat allowance; 30min reserve at min.cruise speed (presumably a landing
reserve, and also possibly an allowance for adverse winds etc.).

> >In effect a 25 gallon reserve would deduct some 140 or so miles
> >from the range and 70 miles from the radius.
>
> Sure but in a world where some of the Spit IX's escorting the first
> Schweinfurt raid ran themselves out of fuel over the channel and
> glided back to the English coast, I think the lack of reserve is not
> ahistorical. It seems to have been left to individual pilots and
> their formation leaders to monitor their fuel consumption and act
> accordingly, allowing more aggressive leaders to risk running out of
> fuel entirely (e.g. the loss of 133 squadron over Britanny).

See comments above.

> >Hang on,
>
> Looks like my sums were at fault here. I shall chastise my pet
> mathmetician.
>
> >The original design has 63 gallons or 304 miles for cruise, the
> >extra 75 gallons internal fuel adds 362 miles,
>
> 125 minutes total cruise endurance on internal fuel (minus climb and
> combat allocations, no reserve), giving a still air range of 666
> miles.
>
> >an extra 90 gallons
> >external fuel adds 434 miles less the effects of drag on the tank,
> >all up 1,100 miles or 550 miles radius.
>
> My guess was an extra 81 minutes endurance at 300 mph for the same
> fuel consumption, giving 405 miles range.
>
> This gives a total estimated range of 1,071 miles, for a radius of 535
> miles.
>
> >All of the above ignoring the inevitable loss of range thanks to the
> >weight of fuel and especially the drag of the external tanks(s).
>
> The weight isn't going to make a substantive difference as I see it,
> except to initial rate of climb. I've factored in the assumed drag
> for the tank-carrying stage, which can only be on the outbound leg.
>
> >Put it another way, for the Spitfire 23 gallons for take off and climb,
> >36 gallons for combat, 25 gallons for a reserve, 4.8 miles per gallon
> >at 320 mph at 20,000 feet. Maximum internal fuel 199 gallons
>
> To quibble, I prefer 197 (probably down to the precise capacity of the
> two wing leading-edge tanks).

> [Official range figures]
>
> >Yet the figures above give the mark VIII a maximum radius of 150
> >miles at 20,000 feet or less than 25% of the official range.
>
> Yes, I've posted on this issue before, the RAF were just as
> conservative with the Mustang III range.
>
> >Mind you given the weight of fuel involved there would have to
> >be some airframe strengthening, since 310 British gallons of
> >100 octane fuel weighs 1 long ton. The extra 75 gallons internal
> >fuel alone comes to 541 pounds, the external 90 gallons another
> >650 pounds. Then add the weight of the tanks. The maximum
> >permissible weight for a wartime Spitfire VIII was 8,000 pounds,
> >with normal loaded weight around 7,800 pounds. Also we have
> >definition problems, the mark XIV figures are take off 8,475 pounds,
> >maximum permissible 8,500, then10,280 pounds maximum overload.
> >Carrying a 90 gallon tank meant the mark XIV weighed in at 9,278
> >pounds for example. So a Spitfire VIII should have a maximum
> >overload weight of over 9,000 pounds.
>
> The issue here can be resolved by operational necessity - after all,
> the weight of the fuel was a reducing problem as it was burned off.
>
> [Mustang range]
>
> >Vickers apparently had a proposal for 197 gallons of internal fuel
> >something like 47 + 49 in the front fuselage 2 x 18 (1 in each wing)
> >and 66 gallons in the rear fuselage, which I know totals 198 gallons.
> >Then add external tanks. Even with this arrangement the Mustang
> >has more internal fuel.
>
> Sure, but the idea was not to out-Mustang the Mustang, simply to
> optimise a long-range escort Spitfire within a credible historical
> context. The rear fuselage tankage was tried and introduced by 1945,
> and the internal and overload tankage is historical and even
> contemporary with a last-quarter of 1943 initiative.

Having thought on the matter occasionally since we discussed it in detail, I don't
think that adding the rear fuselage tank is worthwhile. Mk.VIII internal tankage of
122 Imp.gal. (I've seen official figures of 122-124, with values for the wing tanks
from 12.75 -14 gal. ea.) plus a 90 gal. drop tank should allow escort to 250 miles,
possibly 300. Dean says that the Mustang had neutral stability with 35 USG left in
the rear tank -- obviously that would vary somewhat between individual airframes as
well as pilots. I've seen pilot quotes for 25-50% remaining (21.25 - 42.5 USG)
providing acceptable stability in combat, so Dean's 35 USG is a reasonable number.

With the Mustang's normal internal fuel load of 184 USG, the USAAF radii chart Dean
provides gives a 150 mile combat radius under the conditions cited above. Adding the
full 85 gallons above boosts the combat radius to 375 miles, with somewhere between
205.25 and 226.5 USG for combat, return and reserve (which proved adequate to fight
and return from east of Berlin, owing to its relatively low power settings for high
cruise speeds). Given the Spit's rep for a more limited Cg range (or at least the
RAF's more conservative standard of acceptable handling), I suspect that a rear
fuselage tank would add no more than 10-20 Imp.gal. capacity for combat, return and
reserve, or 132-142 Imp.gal. (158.4-170.4 USG), less than even the base int. fuel
tankage (153 Imp/184 USG) of the Mustang, never mind the aft fuselage tank. Even if
we assume that the Spit would be okay with 30 Imp.gal. (36US) remaining in a rear
tank, that just gets it up to a Mustang's base int. fuel load, and the Mustang cruises
significantly faster at the same power setting (the Spit will get to altitude faster).

A Mustang with 184 USG int. fuel plus a pair of 75 gal. drops can escort out to 460
miles. A notional Spit VIII with a 75 imp. gal. rear tank and a 90 imp. gal. (108
USG) drop is, at best, going to make 400, and more likely 350 or less. With Portal
having refused Arnold's request in the fall of 1943 to delay the RAF Mustang III
allocation so that the USAAF could have them instead, the RAF is soon going to have a
far superior escort fighter available (65 Sq. got theirs in Dec.'43), so I just don't
think a rear tank Mk.VIII is going to provide a significant advantage, if any, in the
time available. By all means re-allocate a month or so's early production (IIRR, 90
a/c) of the Mk.VIII from the Med/Pacific to form a single escort wing (possibly
including a single squadron of Mk.VII's for the top cover squadron, to allow 100%
Mk.VIII reserves for the other two sq. of the wing), and use them to provide TARCAP
for the initial operations. Indeed, I'd switch the entire Mk.IX production over to
Mk.VIII's if possible, or at least give them the Mk.VIII fuel load. But the RAF isn't
going to go over heavily defended targets in Germany (or the few such targets in
occupied territory) with Stirlings, so there's really no need for an escort radius
beyond 250 miles or so initially.

> >All up I suspect giving the Spitfire a 400 mile combat radius over
> >Europe was quite possible, 500 miles would be the absolute limit
> >and require significant work given the stability problems reported
> >with the rear tank,
>
> I think issues like the elevator horn balance enlargement and change
> of elevator as reported by Quill were all possible to assist. This
> leaves the Mk VIII (LR) unpleasantly longitudinally unstable on
> take-off and until about 30 gallons of fuel in the rear fuselage tank
> have been burned off.

See above; I think considerably more would have to be burned off prior to combat, at
least 45 gallons and probably more.

<snip US/Brit miles>

> [Historical detail on US penetrations and escort ranges]
>
> Thanks. This ties in with my idea of having the Spitfires working
> within (and slightly extending) the P-47 escort range, both as
> additional escorts to the 8th AF and escorting strikes on German air
> fields likely to be used to intercept them.

In the fall of 1943, the P-47s could comfortably escort to about 250 miles with a 108
USG tank; Duren (240 miles from Halesworth) was possible with a 75 gallon tank, but
pushing it if significant combat was involved. As the Luftwaffe pulled back it was
possible to go further into Germany on the same fuel; perhaps 300 miles with 108
gallons ext. by early '44. Zemke says the 150USG gal. (actual cap.165 USG or so) C/L
tank allowed the 56th to reach the Hannover area for the first time during Big Week;
325mi from Halesworth and ca.350 from most USAAF fighter bases. Stock Mk.VIIIs would
have matched P-47 radius in the fall of '43, allowing escort to the targets you
mention.

<snip drop tank availability>

> >>Can I now re-equip 2 Group with Stirlings to be escorted by them?
> >
> >Last quarter of 1943?
>
> Yup.
>
> >Admittedly the peak Stirling bomber production
> >was in May (81), June (82) and August (82) 1943 but the decline in
> >bomber versions set in quite rapidly in 1944 even as the total number
> >of Stirlings built remained roughly constant, in January 1944 around half
> >the Stirlings delivered were transports and the percentage increased
> >roughly mid year as production was cut back.
>
> Yes, but this is a factor of their historical removal from bombing
> operations. This time out, I can dispute reduction and elimination of
> production with Harris, although this might cost him some Lancasters
> in late '44 or '45 as a consequence.
>
> I'm trying to get 2 Group into action with bombers that operate
> roughly at the same heights as their Bostons and Mitchells did, but
> carry more than twice the bombload and have a longer range.

See below.

> >Admittedly if you can show the use of such escorted missions then
> >the line was still going at near maximum capacity to June 1944, then
> >deliveries dropped. So 834 bomber versions delivered in 1943 out
> >of 836 Stirlings built. In 1944 it was 298 bombers out of 675 Stirlings
> >delivered. The first half of 1944 saw the delivery of 234 bombers
> >out of 441 Stirlings produced. There was 1 bomber and 202 transport
> >versions delivered in the first 9 months of 1945.
>
> This is plenty to re-equip the six to eight two-flight squadrons
> involved in 2 Group, and can see me hitting German fighter airfields
> with about 250,000 lbs of HE bombs in one 18-aircraft attack instead
> of about 72,000 lbs using the medium bombers.
>
> All I need now are some .5in MG's to replace their .303's, and I've
> got a viable force for daylight ops in support of the 8th AF.

ISTM our plan per ACM Kramer's instructions was to transition BC, or at least a large
portion of it, over to daylight missions. As such, we'd decided to make 3 Group with
its Stirlings and/or Lanc IIs the test case, re-equipping them with Halifax IIIs
(rather than Merlin Lancs) as soon as possible, and re-directing their Lancs to night
Groups. We chose the Halifax IIIs because they were radial-engined (per the GOC's
requirement), because of their 4 gun mid-upper turret (better than nothing), and
because they could be easily modified to take a flex-mount .50 in the nose vice a
..303. I thought 2 Group had already left BC, with assignment to 2 TAF for
expeditionary use? While initially using Stirlings for Dumpexs on Dutch, Belgian or
French airfields is fine, we're going to want to hit industrial targets eventually
(the Ruhr and coastal U-boat production initially), and that really isn't 2 Group's
metier.

Guy

.

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