More long-range Spitfires and daylight Bomber Command raids, with added nationalistic abuse (was: #1 Jet of World War II)

(Peter Stickney) wrote:
Mike Marron wrote:

Thanks for the explanation. What does "...isn't accountable" mean?

It means that it doesn't get counted as a bomber or strategic missile
launcher when totting up the numbers for (them) SALT and (now) START
compliance. Of course, that business as always a bit dodgy.
For examples, Tu-22Ms (Backfires) with the AAR probe were considered
as Strategic Bombers, but the same T-22M with the probe unbolted &
sitting in the back of the hangar wasn't. Or the Minuteman III ICBM
was considered to cary 5 warheads instead of 3, because somebody'd
made a short range launch of one carrying 5 instrument packages.

It's all very lawyerly.
^^^^^^^^^^^^^^^^^^^^

I rest my case!

-Mike (a bomber by any other name...) Marron

On Mon, 15 Sep 2003 05:35:43 GMT, Guy Alcala
wrote:

Mike Marron wrote:

(Peter Stickney) wrote:

To each their own.

Yer ass sucks bilgewater.

-Mike Marron

and

"Tex Houston" wrote:

Sorry...the correct spelling is "Accidents" on the last entry.

As if. As if anyone gives a ****.

Wonder if my spell checker disregards anything in quotes?

Pompous Texass ****.

-Mike Marron

Ah, well, one more for the killfile. Trolls, loons and (as in this case)
just plain rude and crude all get in.

Guy

And your language in this post would qualify as what?

Al Minyard

The Revolution Will Not Be Televised wrote:

On Sat, 13 Sep 2003 19:58:15 GMT, Guy Alcala
wrote:

Okay, I've got Price's "The Spitfire Story," which is very helpful. Here's
what Wing Commander Tuttle, former head of the PRU, told Price about the
handling of the hand-modified PR.1Ds (normal 84 gallons forward, 114 gallons
in the wing L.E., 29 gallons behind the pilot, plus two cameras further back
(but no radio):

"You could not fly it straight and level for the first half hour or hour after
takeoff. Until you had emptied the rear tank, the aircraft hunted the whole
time. The center of gravity was so far back you couldn't control it. It was
the sort of thing that would never have got in during peacetime, but war is
another matter."

What may be barely acceptable for a PR bird flying solo in VFR conditions by
experienced pilots not making any radical maneuvers, is definitely
unacceptable for formation or combat flying by less experienced pilots.

[I've got that book meself]

But this is precisely the argument against any kind of rearward CoG
movement implied by any rear fuselage tanks.

Not any kind, just the kind that can't be used in combat or in formation.
Remember, we're trying to extend the combat radius, with range being essentially
irrelevant. If you've got to burn the fuel off before you enter combat and the
only advantage is to extend the range/endurance, it's easier to just carry a bigger
drop tank. The extra internal fuel would allow you to go a bit further without
carrying a drop tank, but that's a relatively minor (but real) advantage.

Note that this
configuration included up to two cameras positioned further back in
the fuselage than the fuel tanks, which I assume could only have had
an even more detrimental impact on the CoG than a 29 gallon fuel tank.

But no radio, which appears to have been even further back, and IIRR of equal or
greater weight than the cameras (I saw the camera weight listed somewhere, and have
the radio weights). And no guns, but fuel in the L.E.s, which (unlike the gun
armament) is all forward of the datum, moving the Cg forward compared to the
fighter.

I don't think the PR Spits are a valid indicator of what was tolerable
with a fighter profile - e.g. the V's with 29 gallon rear fuselage
tanks (and 170 gallon drop tanks) used for reinforcement flights from
Gibraltar to Malta in October 1942. Now these were not in operational
fighter trim, but they were to be flown by squadron pilots.

Two at a time, not in squadron/wing formations, and not having to take off in IFR
conditions and climb above clouds on instruments. It was recommended to send them
to Malta singly, but Park preferred two so that if one had problems, the other
would have some idea where the a/c went down, so they might have some chance of
rescuing the pilot.

Equally,
the RAF did regard the instability involved in the 75 gallon rear
fuselage tank in the IX airframe to be tolerable when the operational
need was great enough. Tuttle's comments are identical to Quill's and
Havercroft's on the instabilty problems casued by rear fuselage tanks
in the IXs they tested with them.

Ah, but we agree that the IX's had a more forward Cg to start with, and we don't
know the degree of instability (which is what we're waiting on Pete for). BTW, I
think I now know why the Mk. IX/XVI with cut down fuselage had 66 gal. in the rear
fuselage tanks vice 75: a simple space issue. The photo in "The Spitfire Story"
(pg. 162 in the copy I have) showing a Mk. IX with aft tanks shows that they're
stacked directly behind the pilot's back armor plate, and the upper one extends
almost to the top of the aft cockpit glazing Presumably the bubble-canopy a/c
tanks were lower.

Later, the production PR.1Ds had the aft tank removed, the radio reinstalled,
and the L.E. tanks enlarged from 57 to 66.5 gallons each side, to improve the
handling (L.E. tanks were forward of the datum). They also got somewhat
heavier Merlin 45s.

They also began to get drop tanks underneath the fuselage to extend
range.

I think it's instructive that until alternative fuel tankage
could be provided in the wings and externally, they did adopt a rear
fuselage tank, and that was in an aircraft with an existing CoG travel
worse than the fighter versions.

But was it? After all, with no armament, the Cg moved forward. No radio (mounted
aft of where the cameras would be) moves it forward again. And quite early, they
got external fuel, in 30 gal. blister tanks under the wings.

The CoG problems this caused were
certainly unacceptable for peacetime flight, but then - by the RAF's
standards - so were the rear-fuselage tanks in the later Spit IXs and
XVIs, which were ordered not to be used without direct orders in the
post-war Pilot's Notes.

Unfortunately, we don't know the degree of instability (and Cg travel) of the
various versions, since they apparently found measuring such rather difficult at
the time. It seems to have been a question of phugoids and nothing else, which
would leave a lot up to pilot interpretation.

This is also reflected in the decision to
delete the rear-fuselage tank in the RAF's Mustang IIIs. All of this
stems from an institutional attitude and the extent to which it could
be influenced by operational neccessity.

Certainly a factor.

The fact that late production Spitfires did get rear fuselage tanks
which the RAF considered compromised aircraft stability too much for
normal peacetime operation is instructive. If we were to take
Tuttle's comments about peacetime operations as gospel for credible
wartime developments, none of this development in regard of rear
fuselage tanks would have happened at all.

Sure.

What this counterfactual stems from was the level to which the RAF was
prepared to modify peacetime levels of aircraft stability to meet
operational needs. We know their historic position, but in this case
we are positing a greater operational need for range, in which case we
need to consider what would be a credible reaction. We can all agree
that the Spitfire (and especially the Spit V) had serious constraints
involved in increasing internal tankage, and specifically in the rear
fuselage. I believe it is instructive to observe how far the RAF were
pushed down that route historically, and extrapolate on a reasonable
basis from that.

On that basis, the use of the 29 gallon rear fuselage tank can't be
ruled out on the basis that the RAF preferred not to use it. If we
left it to RAF institutional preference alone there wouldn't have been
any rear fuselage tanks at all, but then nor would there have been PR
Spitfires to start with.

I think the Mk. IX could probably have gotten away with a 29 gallon tank or
something in that range, even with the original tail. I have serious doubts that
the Mk. V could have. Tuttle's comments imply negative longitudinal stability with
ANY fuel in the tank, and that means it is of no help to us for increasing fighter
combat radius. We could put the same fuel in a larger drop tank (at somewhat
higher drag, to be sure), say 120 gallons; the handling will be better than with
the rear tank, and it's a much simpler solution.

Guy

Alan Minyard wrote:

On Mon, 15 Sep 2003 05:35:43 GMT, Guy Alcala

Ah, well, one more for the killfile. Trolls, loons and (as in this case)
just plain rude and crude all get in.

Guy

And your language in this post would qualify as what?

Al Minyard

Let's see, not rude and crude (I suppose my posting it publicly rather than
privately could be considered rude), nor is it a troll, and I presume you
aren't implying that I'm a loon. What did you think it was?

Guy

Guy Alcala wrote:

The Revolution Will Not Be Televised wrote:

snip

I think it's instructive that until alternative fuel tankage
could be provided in the wings and externally, they did adopt a rear
fuselage tank, and that was in an aircraft with an existing CoG travel
worse than the fighter versions.

But was it? After all, with no armament, the Cg moved forward. No radio (mounted
aft of where the cameras would be) moves it forward again. And quite early, they
got external fuel, in 30 gal. blister tanks under the wings.

And before I forget, the (high altitude) PR birds like the PR. 1D also lacked
gunsights, bulletproof glass, the gun camera, and the flare chutes/ditty box (cameras
went in thatspace). So far I've been unable to find whether the (high altitude) PR a/c
also removed the armor (the very early PR a/c probably lacked it from the start), but
it might make sense to do so. The flare chutes/ditty box are no great loss from the
fighter. With the exception of the gun camera, all of these are behind the datum, and
while individually small (except the armor), they do all move the Cg aft.


The CoG problems this caused were

certainly unacceptable for peacetime flight, but then - by the RAF's
standards - so were the rear-fuselage tanks in the later Spit IXs and
XVIs, which were ordered not to be used without direct orders in the
post-war Pilot's Notes.

Unfortunately, we don't know the degree of instability (and Cg travel) of the
various versions, since they apparently found measuring such rather difficult at
the time. It seems to have been a question of phugoids and nothing else, which
would leave a lot up to pilot interpretation.

Correction: We do have the Cg travel of some of the versions, but not in any
systematic fashion.

snip

The fact that late production Spitfires did get rear fuselage tanks
which the RAF considered compromised aircraft stability too much for
normal peacetime operation is instructive. If we were to take
Tuttle's comments about peacetime operations as gospel for credible
wartime developments, none of this development in regard of rear
fuselage tanks would have happened at all.

Sure.

What this counterfactual stems from was the level to which the RAF was
prepared to modify peacetime levels of aircraft stability to meet
operational needs. We know their historic position, but in this case
we are positing a greater operational need for range, in which case we
need to consider what would be a credible reaction. We can all agree
that the Spitfire (and especially the Spit V) had serious constraints
involved in increasing internal tankage, and specifically in the rear
fuselage. I believe it is instructive to observe how far the RAF were
pushed down that route historically, and extrapolate on a reasonable
basis from that.

On that basis, the use of the 29 gallon rear fuselage tank can't be
ruled out on the basis that the RAF preferred not to use it. If we
left it to RAF institutional preference alone there wouldn't have been
any rear fuselage tanks at all, but then nor would there have been PR
Spitfires to start with.

I think the Mk. IX could probably have gotten away with a 29 gallon tank or
something in that range, even with the original tail. I have serious doubts that
the Mk. V could have. Tuttle's comments imply negative longitudinal stability with
ANY fuel in the tank, and that means it is of no help to us for increasing fighter
combat radius. We could put the same fuel in a larger drop tank (at somewhat
higher drag, to be sure), say 120 gallons; the handling will be better than with
the rear tank, and it's a much simpler solution.

Checking the Mk. IX weight and loading chart at

http://www.fourthfightergroup.com/eagles/ab197.html

it's stated that the a/c tare weight includes 87.5 lb. of ballast in the tail.

Guy

I'm back, but an ahem, "flying visit" Trade Show season for us is
coming up, and I've just shaken off a 48 hour attack of the 24 Hour
Ebola...

In article ,
Guy Alcala writes:
The Revolution Will Not Be Televised wrote:

On Sat, 13 Sep 2003 19:58:15 GMT, Guy Alcala
wrote:

Okay, I've got Price's "The Spitfire Story," which is very helpful. Here's
what Wing Commander Tuttle, former head of the PRU, told Price about the
handling of the hand-modified PR.1Ds (normal 84 gallons forward, 114 gallons
in the wing L.E., 29 gallons behind the pilot, plus two cameras further back
(but no radio):

"You could not fly it straight and level for the first half hour or hour after
takeoff. Until you had emptied the rear tank, the aircraft hunted the whole
time. The center of gravity was so far back you couldn't control it. It was
the sort of thing that would never have got in during peacetime, but war is
another matter."

What may be barely acceptable for a PR bird flying solo in VFR conditions by
experienced pilots not making any radical maneuvers, is definitely
unacceptable for formation or combat flying by less experienced pilots.

I've managed to latch onto a few Spitfire Pilot's Notes.
Specifically, the Mk V/Seafire II/III, the Mk XII, the Mk XIV, and the
Seafire Fr. 46. (No Mk IX yet, dangit!) I'll gove more exact quotes
tomorrow, but I'll sum up a bit here, as appropriate.

The Spit FR. XIV is listed as having a 31 imp. gallon tank behind the
cockpit, and 2 13 imp. gallon tanks in the wing leading edges. Note that
this is only for the FR. XIV (Fighter/Recce), not the F. XIV (Pure
Fighter) or the P.R. XIV (Pure Recce). It's also worth noting that
the date of publication is early 1946, and at that time, the rear
fuselage tank is noted as "Blanked off and not to be used unless
specifically ordered by hte Operational Commander, and only for
special operations. In the Handling Section, it is noted that teh use
of the rear fuselage tank reduces stability, and the aircraft should
not be flown above 15,000' until it is empty. (That's not really a
problem with a Griffon Spit) The recommended fuel burn sequence it to
take off on the main tanks, switch to the rear tank at 2,000', and
when that's empty, (signified by the engine quitting) switching back
to the drop tank, if fitted, or the main tanks and transferring the
wing tank fuel as soon as possible.

So, it was there, adn it was a somewhat useful amount of fuel, but it
really wasn't considered a good thing.


[I've got that book meself]

But this is precisely the argument against any kind of rearward CoG
movement implied by any rear fuselage tanks.

Not any kind, just the kind that can't be used in combat or in formation.
Remember, we're trying to extend the combat radius, with range being essentially
irrelevant. If you've got to burn the fuel off before you enter combat and the
only advantage is to extend the range/endurance, it's easier to just carry a bigger
drop tank. The extra internal fuel would allow you to go a bit further without
carrying a drop tank, but that's a relatively minor (but real) advantage.

Note that this
configuration included up to two cameras positioned further back in
the fuselage than the fuel tanks, which I assume could only have had
an even more detrimental impact on the CoG than a 29 gallon fuel tank.

But no radio, which appears to have been even further back, and IIRR of equal or
greater weight than the cameras (I saw the camera weight listed somewhere, and have
the radio weights). And no guns, but fuel in the L.E.s, which (unlike the gun
armament) is all forward of the datum, moving the Cg forward compared to the
fighter.

I don't think the PR Spits are a valid indicator of what was tolerable
with a fighter profile - e.g. the V's with 29 gallon rear fuselage
tanks (and 170 gallon drop tanks) used for reinforcement flights from
Gibraltar to Malta in October 1942. Now these were not in operational
fighter trim, but they were to be flown by squadron pilots.

Two at a time, not in squadron/wing formations, and not having to take off in IFR
conditions and climb above clouds on instruments. It was recommended to send them
to Malta singly, but Park preferred two so that if one had problems, the other
would have some idea where the a/c went down, so they might have some chance of
rescuing the pilot.

Oddly enough, the Spit V notes has an appendix to th handling
instruction for the 29 gallon fuselage tank/170 gallon super drop tank
combination. A few salient points: The aircraft is restricted to
straight and level flight until the drop tank and the rear fuselage
tank are empty. There are a lot of warning about how setting the fuel
cocks wrong will case teh system to siphon fuel overboard. The
sequence of use was to take off on the main tanks, switch to the
drop tank and run it dry (indicated by the engine cutting out - the
Spitfure Fuel gages must have been designed by the same bloke who did
the MG oil gage. Lucas, I think his name was.) The the rear tank is
emptied, (Same fuel gage), then the mains. The drop tank may be
jettisoned at any time, as long as you're straight and level, empty,
full, or in between. Nothing but straght and level until the rear
fuselage tank empties.

So - while it appears that the 29 gallon tank wa only intended to be
used with the 170 gallon tank for the Malta reinforcements, there's
really no reason why it might not have been considered, with the
proviso that you couldn't fly a real formation, or engage in combat
until it was empty, or that it couldn't be used with one of the
smaller "combat" tanks. Note though, that the 90 imp. gallon tank is
also restricted to straight and level flight.

That's a bit more flexible than I thought it would be.



Equally,
the RAF did regard the instability involved in the 75 gallon rear
fuselage tank in the IX airframe to be tolerable when the operational
need was great enough. Tuttle's comments are identical to Quill's and
Havercroft's on the instabilty problems casued by rear fuselage tanks
in the IXs they tested with them.

Ah, but we agree that the IX's had a more forward Cg to start with, and we don't
know the degree of instability (which is what we're waiting on Pete for). BTW, I
think I now know why the Mk. IX/XVI with cut down fuselage had 66 gal. in the rear
fuselage tanks vice 75: a simple space issue. The photo in "The Spitfire Story"
(pg. 162 in the copy I have) showing a Mk. IX with aft tanks shows that they're
stacked directly behind the pilot's back armor plate, and the upper one extends
almost to the top of the aft cockpit glazing Presumably the bubble-canopy a/c
tanks were lower.

Later, the production PR.1Ds had the aft tank removed, the radio reinstalled,
and the L.E. tanks enlarged from 57 to 66.5 gallons each side, to improve the
handling (L.E. tanks were forward of the datum). They also got somewhat
heavier Merlin 45s.

They also began to get drop tanks underneath the fuselage to extend
range.

I think it's instructive that until alternative fuel tankage
could be provided in the wings and externally, they did adopt a rear
fuselage tank, and that was in an aircraft with an existing CoG travel
worse than the fighter versions.

But was it? After all, with no armament, the Cg moved forward. No radio (mounted
aft of where the cameras would be) moves it forward again. And quite early, they
got external fuel, in 30 gal. blister tanks under the wings.

Not only that, but a PR Spit wasn't expected to be maneuvering - It's
job was to be as high as possiblem where nobody had any maneuver
margin. They'd get to height as soon as possible after tankeoff, and
stay there. A good chunk of the aft fuel would get burned off in the
climb. It's also worth noting that the PR Spits had no disposable
load other than fuel. On the fighter Spits, the ammunition was aft of
the CG, (but not too much) and contributed to any stability problems.


The CoG problems this caused were
certainly unacceptable for peacetime flight, but then - by the RAF's
standards - so were the rear-fuselage tanks in the later Spit IXs and
XVIs, which were ordered not to be used without direct orders in the
post-war Pilot's Notes.

Unfortunately, we don't know the degree of instability (and Cg travel) of the
various versions, since they apparently found measuring such rather difficult at
the time. It seems to have been a question of phugoids and nothing else, which
would leave a lot up to pilot interpretation.

This is also reflected in the decision to
delete the rear-fuselage tank in the RAF's Mustang IIIs. All of this
stems from an institutional attitude and the extent to which it could
be influenced by operational neccessity.

Certainly a factor.

The fact that late production Spitfires did get rear fuselage tanks
which the RAF considered compromised aircraft stability too much for
normal peacetime operation is instructive. If we were to take
Tuttle's comments about peacetime operations as gospel for credible
wartime developments, none of this development in regard of rear
fuselage tanks would have happened at all.

Sure.

What this counterfactual stems from was the level to which the RAF was
prepared to modify peacetime levels of aircraft stability to meet
operational needs. We know their historic position, but in this case
we are positing a greater operational need for range, in which case we
need to consider what would be a credible reaction. We can all agree
that the Spitfire (and especially the Spit V) had serious constraints
involved in increasing internal tankage, and specifically in the rear
fuselage. I believe it is instructive to observe how far the RAF were
pushed down that route historically, and extrapolate on a reasonable
basis from that.

On that basis, the use of the 29 gallon rear fuselage tank can't be
ruled out on the basis that the RAF preferred not to use it. If we
left it to RAF institutional preference alone there wouldn't have been
any rear fuselage tanks at all, but then nor would there have been PR
Spitfires to start with.

I think the Mk. IX could probably have gotten away with a 29 gallon tank or
something in that range, even with the original tail. I have serious doubts that
the Mk. V could have. Tuttle's comments imply negative longitudinal stability with
ANY fuel in the tank, and that means it is of no help to us for increasing fighter
combat radius. We could put the same fuel in a larger drop tank (at somewhat
higher drag, to be sure), say 120 gallons; the handling will be better than with
the rear tank, and it's a much simpler solution.

See above. I was rather surprised myself. The 90 gallon tank is
pretty much out as anything but a ferry tank, but an intermediate
choice of a 50 or 60 gallon tank would provide the same fuel capacity
over the 30 gallon combat tank as the aft fuselage tank would, without
much in the way of bad effects. (Didn't the Hurricane use a 50 gallon
teardrop or torpedo shaped tank? It might even be less draggy than
the 30 gallon blister.

--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster

On Tue, 16 Sep 2003 23:01:46 GMT, Guy Alcala
wrote:

[I've got that book meself]

But this is precisely the argument against any kind of rearward CoG
movement implied by any rear fuselage tanks.

Not any kind, just the kind that can't be used in combat or in formation.

The problem is that we don't know the CoG travel involved in any of
these changes of equipment and trim. The only loading charts and CoG
details I have are for later versions of Spitfire. Nonetheless, it is
clear from the diagrams I've seen that the PR IV SLR with the 30
gallon rear fuselage tank had two cameras and their mountings,
occupying the entire fuselage at that point, mounted further to the
rear than the 29-gallon ferry tank. I don't know the weights involved
with the cameras, but in the case of the 29 gallon tank this was
mounted in the fuselage immediately behind the pilot: unless the tank
went under the pilot's seat there was no place with less of an impact
on rearwards CoG travel to put it.

Now, I fully accept that 200lbs of extra weight in the rear fuselage
in any position would make the handling of a Spit Vc deteriorate, but
I find it hard to believe that this was not a creditable proposition
within operationally tolerable limits, especially at a time when tail
ballast was being increased to test heavier Rotol propellers.

Remember, we're trying to extend the combat radius, with range being essentially
irrelevant. If you've got to burn the fuel off before you enter combat and the
only advantage is to extend the range/endurance, it's easier to just carry a bigger
drop tank.

To a point: the critical issue is the handling deterioration involved
in both cases. We know that a stock Mk IX was considered acceptable
for manoevering with 30 gallons or so consumed out of a 75 gallon rear
tank, and although this involves an aircraft with a different CoG
loadout and weight distribution, we know the RAF was prepared to
tolerate 30-40 gallons worth of weight with a detrimental impact on
longitudinal stability to increase operational radius in 1944-45.

I'm advancing the 29-gallon tank scenario because this offers the RAF
precisely this capacity in mid-1942 in plenty of time for further
exploitation in the summer of 1943. R&D workThe 29-gallon rear tank
and 90-gallon drop tank combination had already been done and offered
an "off the peg" solution for increasing the 12 Group Spit V wing's
escort ranges when this first became an issue. I'm not arguing that
this was an optimal solution, but I do think it was a possible and
credible one given the fact that it was an already-existing historical
equipment option.

I'm starting my speculation from the point of "what was actually
available" with Fighter Command escorts for US strategic raids. The
best-placed units for escorting attacks on Willhelmshaven, Bremen and
Hamburg were the 12 Group squadrons at Ludham, Coltishall, etc. These
units were considered second-line to the squadrons in 11 Group which
had priority for the Spitfire IX, and so an initial escorting solution
might have to be found which maximises their potential before major
reallocation of Mk VIIIs or anything else takes place.

Obviously, if you're positing the major change in strategic direction
under ACM Kramer in September 1943 rather than from the ground up in
June, as I am, then the whole issue of increasing the range of the Mk
V is moot.

Having said that, some figures from AVM Stickney might be interesting
to indicate precisely how much ******** I've been talking so far.

The extra internal fuel would allow you to go a bit further without
carrying a drop tank, but that's a relatively minor (but real) advantage.

Whatever we do, the Spit escorts beyond the Zuider Zee/German border
are going to be less effective than the P-38s or P-51s because of the
internal fuel limitations, but even a "drop external tanks, one or two
passes and then home" profile is better than no escort at all.

There's no question that MK VIII-style increased internal tankage is a
better option, as the wing leading-edge tanks and enlarged forward
tanks give greater endurance in combat trim than any external tankage
could provide.

[aftwards CoG in PR IV Spits]

But no radio, which appears to have been even further back, and IIRR of equal or
greater weight than the cameras (I saw the camera weight listed somewhere, and have
the radio weights).

How much were they? In my LR Vc scenario, the radio stays where it
is, the oxygen bottles get displaced downwards and the top half of the
clear perspex frame behind the pilot now has a fuel tank. I'm not
sure what impact this would have on the pilot's armour plate: I'm
pretty convinced it would be impossible to move it aft to protect the
tank without an unacceptable impact on CoG travel.

I don't think the PR Spits are a valid indicator of what was tolerable
with a fighter profile - e.g. the V's with 29 gallon rear fuselage
tanks (and 170 gallon drop tanks) used for reinforcement flights from
Gibraltar to Malta in October 1942. Now these were not in operational
fighter trim, but they were to be flown by squadron pilots.

Two at a time, not in squadron/wing formations, and not having to take off in IFR
conditions and climb above clouds on instruments.

Yeah, but this was also with the 170 gallon overload tank; I don't
think we can take it as a comment on what the 29 galllon tank was like
in isolation.

[instability eliminated in Mk IXs after 30 gallons used from 75 gall
rear tank]

Ah, but we agree that the IX's had a more forward Cg to start with, and we don't
know the degree of instability (which is what we're waiting on Pete for).

Precisely.

BTW, I
think I now know why the Mk. IX/XVI with cut down fuselage had 66 gal. in the rear
fuselage tanks vice 75: a simple space issue.

Yep.

The photo in "The Spitfire Story"
(pg. 162 in the copy I have) showing a Mk. IX with aft tanks shows that they're
stacked directly behind the pilot's back armor plate, and the upper one extends
almost to the top of the aft cockpit glazing Presumably the bubble-canopy a/c
tanks were lower.

Yep.

I think it's instructive that until alternative fuel tankage
could be provided in the wings and externally, they did adopt a rear
fuselage tank, and that was in an aircraft with an existing CoG travel
worse than the fighter versions.

But was it? After all, with no armament, the Cg moved forward.

And moved back with wing tanks....

No radio (mounted
aft of where the cameras would be) moves it forward again.

But the cameras moved it back again....

I agree, we can't really conclude this without some more information
on the CoG travel involved in the V and IX.

Unfortunately, we don't know the degree of instability (and Cg travel) of the
various versions, since they apparently found measuring such rather difficult at
the time. It seems to have been a question of phugoids and nothing else, which
would leave a lot up to pilot interpretation.

Exactly. But from a service which ordered single-engined fighter
pilots up at night in 1940-41 with no radar or landing aids worth the
name, or ordered a Hurricane squadron to fly off a carrier in May 1940
with no prior experience, or ordered the first Typhoon wing into
action when the engines were still blowing up and the tails falling
off, I think we can assume a certain degree of ruthlessness when it
comes to a perceived operational requirement.

[snip evidence of unprovoked agreement]

On that basis, the use of the 29 gallon rear fuselage tank can't be
ruled out on the basis that the RAF preferred not to use it. If we
left it to RAF institutional preference alone there wouldn't have been
any rear fuselage tanks at all, but then nor would there have been PR
Spitfires to start with.

I think the Mk. IX could probably have gotten away with a 29 gallon tank or
something in that range, even with the original tail.

Actually, they were getting the 75 gallon tank even without the
broad-chord tail.

I have serious doubts that
the Mk. V could have.

I can see the rationale, but I'm talking about less than half the
weight.

Tuttle's comments imply negative longitudinal stability with
ANY fuel in the tank, and that means it is of no help to us for increasing fighter
combat radius. We could put the same fuel in a larger drop tank (at somewhat
higher drag, to be sure), say 120 gallons; the handling will be better than with
the rear tank, and it's a much simpler solution.

I see the point but once again I'd urge the constraints of actual
production availability. The 90 gallon tanks were available in
quantity in time for this: I'm sure they could have built other
tanks, but the strategy would have had to be made to work with what
was realistically available first.

Gavin Bailey

--

Another user rings. "I need more space" he says.
"Well, why not move to Texas?", I ask. - The ******* Operator From Hell

The Revolution Will Not Be Televised wrote:

On Tue, 16 Sep 2003 23:01:46 GMT, Guy Alcala
wrote:

[I've got that book meself]

But this is precisely the argument against any kind of rearward CoG
movement implied by any rear fuselage tanks.

Not any kind, just the kind that can't be used in combat or in formation.

The problem is that we don't know the CoG travel involved in any of
these changes of equipment and trim. The only loading charts and CoG
details I have are for later versions of Spitfire.

Same here.

Nonetheless, it is
clear from the diagrams I've seen that the PR IV SLR with the 30
gallon rear fuselage tank had two cameras and their mountings,
occupying the entire fuselage at that point, mounted further to the
rear than the 29-gallon ferry tank.

I think you mean the prototype PR.1Ds, not the PR.IV per se. The latter was the
production version, and deleted the rear fuselage tank while replacing the radio ((they
may have moved it) and boosting the L.E .fuel (which was forward of the Cg) from 114 to
133 gallons, "to improve handling".

I don't know the weights involved
with the cameras, but in the case of the 29 gallon tank this was
mounted in the fuselage immediately behind the pilot: unless the tank
went under the pilot's seat there was no place with less of an impact
on rearwards CoG travel to put it.

Yes, and the cameras were in lieu of the radio.

Now, I fully accept that 200lbs of extra weight in the rear fuselage
in any position would make the handling of a Spit Vc deteriorate, but
I find it hard to believe that this was not a creditable proposition
within operationally tolerable limits, especially at a time when tail
ballast was being increased to test heavier Rotol propellers.

According to Vader, the early Spit Is with armor just had it at the rear of the
firewall, plus the bulletproof glass; he doesn't give the total weight. He lists 73 lb.
total weight of armor for the Mk. II, and mentions that the pilot got seat to head
protection (bad for Cg) and the glycol header tank was protected (good for Cg). He
credits the Mk. V with 152 lb. of armor, the Mk. VIII/IX with 202 lb. Most if not all of
this would likely be behind the datum. The PR.1D that Tuttle was talking about probably
had little or none of this; we know it lacked the bulletproof glass, and at most it
would have had the armor of the Mk. II. I suspect they also lacked dinghies (15 lb. @
the cockpit) at the time as well (aside; anyone know just when the RAF fighters got
them?). I suspect the Vc is starting with a Cg well aft of the PR.1D, before you add
the rear tank to either (I assume the radio balances off the cameras).

Remember, we're trying to extend the combat radius, with range being essentially
irrelevant. If you've got to burn the fuel off before you enter combat and the
only advantage is to extend the range/endurance, it's easier to just carry a bigger
drop tank.

To a point: the critical issue is the handling deterioration involved
in both cases. We know that a stock Mk IX was considered acceptable
for manoevering with 30 gallons or so consumed out of a 75 gallon rear
tank, and although this involves an aircraft with a different CoG
loadout and weight distribution,

Very different. The engine alone weighs ca. 200 lb. more, all well forward of the
datum, then there's the four vice three blade prop way out in front. The Mk. IX's a lot
better place to start than the Mk. V, for performance AND Cg.

we know the RAF was prepared to
tolerate 30-40 gallons worth of weight with a detrimental impact on
longitudinal stability to increase operational radius in 1944-45.

See above.

I'm advancing the 29-gallon tank scenario because this offers the RAF
precisely this capacity in mid-1942 in plenty of time for further
exploitation in the summer of 1943. R&D workThe 29-gallon rear tank
and 90-gallon drop tank combination had already been done and offered
an "off the peg" solution for increasing the 12 Group Spit V wing's
escort ranges when this first became an issue.

I'm not arguing that
this was an optimal solution, but I do think it was a possible and
credible one given the fact that it was an already-existing historical
equipment option.

But the Mk. VII/VIII's enlarged forward tanks and L.E. tanks were also an already
existing (and better) option, as were enlarged tanks for the Mk. IX (the prototype, a
converted Mk. VC, had 92 gallons in the forward fuselage instead of 85). If we posit a
decision to go over to daylight in 1943, then the ability to boost the fighter range
beyond medium-bomber escort radius doesn't need to be demonstrated or even shown to be
necessary on an obsolete a/c; this capability now becomes a strategic requirement. With
that premise, and with all the mods we're going to have to make to the bombers
themselves, the necessary priority would be available to modify Mk. IXs. They'd have
no choice but to boost the radius, and the obvious way to do that is to grab the
already in production mods for the Mk. VIII and put them in the Mk. IX, as well as
grabbing the Mk. VIIIs (and why not, Mk. VIIs) in the meantime.

I'm starting my speculation from the point of "what was actually
available" with Fighter Command escorts for US strategic raids. The
best-placed units for escorting attacks on Willhelmshaven, Bremen and
Hamburg were the 12 Group squadrons at Ludham, Coltishall, etc.

I'm assuming Ludham and Matlask. Of course, both of these bases were supposed to be
turned over to the 8th AF, but owing to the diversion of forces to the 15th AF in Italy,
they were never taken over by us.

These
units were considered second-line to the squadrons in 11 Group which
had priority for the Spitfire IX, and so an initial escorting solution
might have to be found which maximises their potential before major
reallocation of Mk VIIIs or anything else takes place.

But they were only second-line because they didn't have top priority. Now we're talking
about changing almost the whole methodology of Fighter and Bomber Command. If the
necessary priority exists to change the latter, then it certainly will exist for the
former, and the Mk. IXs (or Mk. VIIIs) will be made available, one way or another. And
it's not as if 11 Group won't have any need for longer-ranged Spits themselves; for
targets on or south of a line from London through Essen and on east, the range is the
same or shorter from forward bases in Southeastern England, like Hawkinge, Lympne and
(especially) Manston. Essentially, for any target in or south of Belgium, 11 Group is in
an equal or better position.

Obviously, if you're positing the major change in strategic direction
under ACM Kramer in September 1943 rather than from the ground up in
June, as I am, then the whole issue of increasing the range of the Mk
V is moot.

I think it's moot in June, for the reasons given above. Change the strategic direction
and the priorities change as well; Fighter Command will have no choice but to conform.
Any change you make to the Mk. V can be made just as easily to the Mk. IX, and with
improved handling and performance.

Having said that, some figures from AVM Stickney might be interesting
to indicate precisely how much ******** I've been talking so far.

Sure would help, but since I'm not volunteering to do the number crunching (even if I
was qualified to do so), I guess we'll have to wait;-).

The extra internal fuel would allow you to go a bit further without
carrying a drop tank, but that's a relatively minor (but real) advantage.

Whatever we do, the Spit escorts beyond the Zuider Zee/German border
are going to be less effective than the P-38s or P-51s because of the
internal fuel limitations, but even a "drop external tanks, one or two
passes and then home" profile is better than no escort at all.

There's no question that MK VIII-style increased internal tankage is a
better option, as the wing leading-edge tanks and enlarged forward
tanks give greater endurance in combat trim than any external tankage
could provide.

Just for giggles, it was interesting to note that even a Mk. VIII with its normal 122
gallons internal (or 123 or 4, take your pick) PLUS a 90 gallon drop tank, still has
about 13 U.S. gallons less fuel than a P-51 with internal wing and aft fuselage tanks
full. The USAAF charts for escort radius reprinted in "America's Hundred Thousand"
credit a P-51D with a 375 mile escort radius on _internal_ fuel (with the aft tank) @
25,000 feet, with combat allowances for 5 minutes WE and 15 minutes Mil. power.

[aftwards CoG in PR IV Spits]

But no radio, which appears to have been even further back, and IIRR of equal or
greater weight than the cameras (I saw the camera weight listed somewhere, and have
the radio weights).

How much were they?

See below.

In my LR Vc scenario, the radio stays where it
is, the oxygen bottles get displaced downwards and the top half of the
clear perspex frame behind the pilot now has a fuel tank. I'm not
sure what impact this would have on the pilot's armour plate: I'm
pretty convinced it would be impossible to move it aft to protect the
tank without an unacceptable impact on CoG travel.

I don't think the PR Spits are a valid indicator of what was tolerable
with a fighter profile - e.g. the V's with 29 gallon rear fuselage
tanks (and 170 gallon drop tanks) used for reinforcement flights from
Gibraltar to Malta in October 1942. Now these were not in operational
fighter trim, but they were to be flown by squadron pilots.

Two at a time, not in squadron/wing formations, and not having to take off in IFR
conditions and climb above clouds on instruments.

Yeah, but this was also with the 170 gallon overload tank; I don't
think we can take it as a comment on what the 29 galllon tank was like
in isolation.

Agreed, but it was also with only a pair of .303s installed and 350 rpg, and the slipper
tanks weren't all that far aft of the datum. (of course, there may have been separate
aerodynamic issues with the 170 gal. tank).

[instability eliminated in Mk IXs after 30 gallons used from 75 gall
rear tank]

Ah, but we agree that the IX's had a more forward Cg to start with, and we don't
know the degree of instability (which is what we're waiting on Pete for).

Precisely.

snip agreement on reason for reduction in aft tankage on cutdown Mk. IX/XVI

I think it's instructive that until alternative fuel tankage
could be provided in the wings and externally, they did adopt a rear
fuselage tank, and that was in an aircraft with an existing CoG travel
worse than the fighter versions.

But was it? After all, with no armament, the Cg moved forward.

And moved back with wing tanks....

I think we're talking about different a/c. The ones with the 30 gallon blister tanks
weren't the PR.1Ds or PR.IVs with aft-mounted cameras, but PR.1B/C/E with wing mounted
ones. The PR.1Fs are the only variants I can think of with blister tanks, an aft tank
and rear cameras, but the cameras seem to normally be shorter focal length (lighter)
than the PR.1D normally used, although Price does indicate that longer lenses could be
carried.

No radio (mounted
aft of where the cameras would be) moves it forward again.

But the cameras moved it back again....

I was assuming the cameras were fitted, and the radio was weight compensation.

I agree, we can't really conclude this without some more information
on the CoG travel involved in the V and IX.

Unfortunately, we don't know the degree of instability (and Cg travel) of the
various versions, since they apparently found measuring such rather difficult at
the time. It seems to have been a question of phugoids and nothing else, which
would leave a lot up to pilot interpretation.

Exactly. But from a service which ordered single-engined fighter
pilots up at night in 1940-41 with no radar or landing aids worth the
name, or ordered a Hurricane squadron to fly off a carrier in May 1940
with no prior experience, or ordered the first Typhoon wing into
action when the engines were still blowing up and the tails falling
off, I think we can assume a certain degree of ruthlessness when it
comes to a perceived operational requirement.

[snip evidence of unprovoked agreement]

On that basis, the use of the 29 gallon rear fuselage tank can't be
ruled out on the basis that the RAF preferred not to use it. If we
left it to RAF institutional preference alone there wouldn't have been
any rear fuselage tanks at all, but then nor would there have been PR
Spitfires to start with.

I think the Mk. IX could probably have gotten away with a 29 gallon tank or
something in that range, even with the original tail.

Actually, they were getting the 75 gallon tank even without the
broad-chord tail.

I meant they could get away with it for combat, not endurance.

I have serious doubts that
the Mk. V could have.

I can see the rationale, but I'm talking about less than half the
weight.

Tuttle's comments imply negative longitudinal stability with
ANY fuel in the tank, and that means it is of no help to us for increasing fighter
combat radius. We could put the same fuel in a larger drop tank (at somewhat
higher drag, to be sure), say 120 gallons; the handling will be better than with
the rear tank, and it's a much simpler solution.

I see the point but once again I'd urge the constraints of actual
production availability. The 90 gallon tanks were available in
quantity in time for this: I'm sure they could have built other
tanks, but the strategy would have had to be made to work with what
was realistically available first.

Were the 29 gallon tanks available in quantity at the time? They seem to have been a
limited production item. If they were limited, then it's six of one, half a dozen of
the other as far as making extra tanks, and you don't need to install all the extra
piping for the aft tank. Still, if the Mk. IX can keep it full and still have
acceptable combat handling, by all means install it.

Guy

On Wed, 17 Sep 2003 01:38:38 -0400, (Peter
Stickney) wrote:

I'm back, but an ahem, "flying visit" Trade Show season for us is
coming up, and I've just shaken off a 48 hour attack of the 24 Hour
Ebola...

The excuses an engineer will come up with in order to lock himself
into a darkened room with his slide rule....

I've managed to latch onto a few Spitfire Pilot's Notes.
Specifically, the Mk V/Seafire II/III, the Mk XII, the Mk XIV, and the
Seafire Fr. 46. (No Mk IX yet, dangit!) I'll gove more exact quotes
tomorrow, but I'll sum up a bit here, as appropriate.

Peter, I've scanned the whole Mk IX Pilot's Notes for you and Guy, but
my last attempt to send you extracts bounced due to lack of space on
your mail account. I can't put them up on a website at the moment, so
I can only email them. Contact me at -



if you have another account I could send the scans to you at.

[rear tank in Mk XIV]

So, it was there, adn it was a somewhat useful amount of fuel, but it
really wasn't considered a good thing.

The FR XIV was the only XIV to get rear tanks, the fighter version
with rear tanks mutated into the Mk XVIII when it started to be
produced on the XIV production lines in the summer of 1945.

There's no doubt that that this represents further evidence of
institutional RAF intolerance to longitudinal instability caused by
rear fuselage tanks to my mind, and it reflects the post-war position
as indicated by Pilot's Notes instructions for other versions of Spit
with the rear tanks.

I can certainly accept that this institutional intolerance existed, as
I have been asserting that from the start of my contributions to this
thread, but as I've said to ACdre Alcala, that intolerance needs to be
balanced against operational need: the the case of the Spit IX/XVI
and Mustang IV, the RAF accepted rear fuselage tankage at the price of
instability for pressing operational reasons. As soon as the war ends
and those operational reasons no longer apply, the institutional norm
will obviously reassert itself. Where I think we should be careful is
using post-war, peacetime evidence of this dynamic and reading it back
into operational service requirements where evidence exists that the
RAF was prepared to compromise their attitude.

I'd love to see the Pilot's Notes for the Mustang IV, as I suspect
they will have some interesting comments on handling and use of the
rear-fuselage tank.

[snip Spit V with 170 gal overload tank and 29 gal rear fuselage tank]

Nothing but straght and level until the rear
fuselage tank empties.

Yes, but this is for an aircraft in ferry trim, and I don't think any
larger conclusions can be safely drawn when it's CoG standard was so
different from ordinary aircraft (no cannon, radios repositioned, etc)

So - while it appears that the 29 gallon tank wa only intended to be
used with the 170 gallon tank for the Malta reinforcements, there's
really no reason why it might not have been considered, with the
proviso that you couldn't fly a real formation, or engage in combat
until it was empty, or that it couldn't be used with one of the
smaller "combat" tanks. Note though, that the 90 imp. gallon tank is
also restricted to straight and level flight.

That's a bit more flexible than I thought it would be.

My thinking was for an extra 29 gallons for early formation flight on
the climb for maybe 20 minutes, with any remainder contributing to the
flight reserve fuel load. As Guy has pointed out, rear fuselage
tankage capacity which comes at the expense of stability cannot be
considered optimal or even tolerable for combat conditions. In
response my contention is that the requirement is for endurance
coverage of long oversea flights out over the North Sea to potential
combat areas over Holland and Germany in the summer of 1943, and the
29 gallon tank in addition to the 90 gallon drop tank would increase
the operational radius in this respect, even if the combat endurance
when the aircraft got there was minimal.

But was it? After all, with no armament, the Cg moved forward. No radio (mounted
aft of where the cameras would be) moves it forward again. And quite early, they
got external fuel, in 30 gal. blister tanks under the wings.

Not only that, but a PR Spit wasn't expected to be maneuvering - It's
job was to be as high as possiblem where nobody had any maneuver
margin. They'd get to height as soon as possible after tankeoff, and
stay there.

On the other hand they were required to evade contact with
manoevreability when required. PR pilots were always expected to drop
external tanks on contact.

A good chunk of the aft fuel would get burned off in the
climb. It's also worth noting that the PR Spits had no disposable
load other than fuel. On the fighter Spits, the ammunition was aft of
the CG, (but not too much) and contributed to any stability problems.

There's also the issue of aft ballast, which varied greatly over the
life of the Spitfire, and over the lifespan of individual marks. The
V is a case in point, and where the equipment loading becomes
bewildering.

See above. I was rather surprised myself. The 90 gallon tank is
pretty much out as anything but a ferry tank,

Ah, but it was actually used by Spitfires and Seafires (with even
worse CoG issues than the Spit V) in combat operations. Examples
include Salerno and Normandy. There was a slipper-tank version and a
later torpedo-tank version. I suspect they would have been used
despite the tank shortcomings: the stability problems would lessen as
the fuel was consumed, and the 8th AF fighters demonstrated that
unpressurised, unreliable paper-mache tanks still could give a useful
benefit to escort radius.

but an intermediate
choice of a 50 or 60 gallon tank would provide the same fuel capacity
over the 30 gallon combat tank as the aft fuselage tank would, without
much in the way of bad effects. (Didn't the Hurricane use a 50 gallon
teardrop or torpedo shaped tank? It might even be less draggy than
the 30 gallon blister.

They actually used a 45 gallon slipper tank as well as the 30 and 90
gallon versions. The 44 gallon Hurricane tank was an unpressurised,
unjettisonable ferry tank, with one carried beneath each wing to give
88 gallons ferry capacity. I have actually seen a photo of a Spitfire
on Malta with an improvised 2 x 44 gallon fuselage tank, although I
suspect this was a local modification made possible due to the
presence of old Hurricane ferry tanks from ferry flights from
Cyrenaica and the lack of the newer slipper tanks until later in 1942.

Whatever happened, the tanks were going to be jettisoned before
initiating combat, so I don't think the 90 gallon tanks - which should
be substantially emptied and consequently lighter before the aircraft
got to the prospective combat area anyway - would in those
circumstances impose as much of a performance restriction as we might
suppose.

Remember, I'm not asserting that any of this was an optimal solution
for long-range escorting, or could have competed with aircraft that
were better suited to expanding their internal fuel capacity. I'm
trying to work along the lines that would be dictated by operational
neccessity and addressed with existing equipment and experience in
certain circumstances.

Gavin Bailey


--

Another user rings. "I need more space" he says.
"Well, why not move to Texas?", I ask. - The ******* Operator From Hell

In article , Peter Stickney
writes

I'm back, but an ahem, "flying visit" Trade Show season for us is
coming up, and I've just shaken off a 48 hour attack of the 24 Hour
Ebola...

In article ,
Guy Alcala writes:
The Revolution Will Not Be Televised wrote:

On Sat, 13 Sep 2003 19:58:15 GMT, Guy Alcala
wrote:

Okay, I've got Price's "The Spitfire Story," which is very helpful. Here's
what Wing Commander Tuttle, former head of the PRU, told Price about the
handling of the hand-modified PR.1Ds (normal 84 gallons forward, 114 gallons
in the wing L.E., 29 gallons behind the pilot, plus two cameras further back
(but no radio):

"You could not fly it straight and level for the first half hour or hour
after
takeoff. Until you had emptied the rear tank, the aircraft hunted the whole
time. The center of gravity was so far back you couldn't control it. It
was
the sort of thing that would never have got in during peacetime, but war is
another matter."

What may be barely acceptable for a PR bird flying solo in VFR conditions by
experienced pilots not making any radical maneuvers, is definitely
unacceptable for formation or combat flying by less experienced pilots.

I've managed to latch onto a few Spitfire Pilot's Notes.
Specifically, the Mk V/Seafire II/III, the Mk XII, the Mk XIV, and the
Seafire Fr. 46. (No Mk IX yet, dangit!) I'll gove more exact quotes
tomorrow, but I'll sum up a bit here, as appropriate.

Is it just the MkIX fuel data you need?

From Pilot's Notes 3rd Edition Sept '46

Two tanks, a top and a bottom, forward of the cockpit.

Top tank - 48 galls
Bottom tank - 37 galls (on some aircraft 47 galls, generally those with
a 'rear view' fuselage).

Later MkIX aircraft have additional capacity in the form of two tanks
behind the canopy. These have a combined capacity of 75 gallons (66 in
aircraft with 'rear view' fuselages) but these are only to be used at
the discretion of the appropriate Area Commander for certain operations,
and when not in use the cocks should be wired off. These are never to
be used in aircraft with rear view fuselages.

(Personal comment - when building an aircraft with a rear view fuselage,
why install the tanks that are forbidden to be used? Unless a batch of
rear view aircraft were produced before the use of the aft tanks was
proved to be dangerous...)

An auxiliary blister drop tank of 30, 45, or 90 galls can be fitted
under the fuselage (170 galls on the PRXI variant). These feed the
engine directly and do not replenish the main tanks. Main tanks are
pressurised, so if holed, pressurisation should be turned off.

Hope this is what you were after - I have not been following this thread
closely.

The Spit FR. XIV is listed as having a 31 imp. gallon tank behind the
cockpit, and 2 13 imp. gallon tanks in the wing leading edges. Note that
this is only for the FR. XIV (Fighter/Recce), not the F. XIV (Pure
Fighter) or the P.R. XIV (Pure Recce). It's also worth noting that
the date of publication is early 1946, and at that time, the rear
fuselage tank is noted as "Blanked off and not to be used unless
specifically ordered by hte Operational Commander, and only for
special operations. In the Handling Section, it is noted that teh use
of the rear fuselage tank reduces stability, and the aircraft should
not be flown above 15,000' until it is empty. (That's not really a
problem with a Griffon Spit) The recommended fuel burn sequence it to
take off on the main tanks, switch to the rear tank at 2,000', and
when that's empty, (signified by the engine quitting) switching back
to the drop tank, if fitted, or the main tanks and transferring the
wing tank fuel as soon as possible.

Biiig snip of rest

Cheers,

Dave

--
Dave Eadsforth