P-51 fuselage fuel tank

[drgondog]

Bill,

I know you've posted something like this before but blame closed head injuries and alcohol.
For a typical long range penetration with P-51 using say two 75gal drop tanks, what's the order of tanks that you'd use from start up to mission end? I seem to recall you start with the left wing tank or am I mistaken?

Blame my obsession with minutia for this.

Thanks

Left main because carb overflow return line supplies return to L. Main. After Group formation, switch to 85gal tank and depending on mission - burn 2-40gal depending on tank fill amt, then alternate externals until near dry (no gauges) - then alternate Mains. At some point near end of mission drain fuse tank to 20gal.

 

[EwenS]

It was used for fuel in the PR Spitfires,

That statement is only 25% true!

The 66.5 gal wing tank (in each wing) that was first installed in the PR.IV Type D (Special LR) and used in subsequent PR variants like the PR.X PR.XI and PR.XIX ran from rib 4 (not rib 1) to rib 21, leaving the space between ribs 1 & 4 "empty". So it was not the entire space in the inboard area between the leading edge & the spar that was converted to carry fuel. There is a diagram showing the layout on p243 of M&S (bottom left). The diagram of the main plane construction for the PR.IV & XI on p240 has a dashed line at rib 4 between the leading edge & the spar. There is also a diagram on p 394 showing the fuel system layout on the PR.XI. Note how far outboard the highlighted rib is situated with the Contents Guage Unit mounted on its outboard side.

So again I ask, what is in that inboard space that prevented it being used for fuel?

Also those wing tanks were created by sealing the entire space from ribs 4-21, effectively turning the space into a "wet wing" area. In the fighter types there was a separate fuel tank fitted into the space between ribs 5 & 7. The arrangement is clearly depicted on p277 of M&S.

With regard to the Seafire, the Griffon engined Mk.XV was the first variant to be fitted with the leading edge wing tanks.

 

[MIflyer]

So again I ask, what is in that inboard space that prevented it being used for fuel?

MLG?

 

[MiTasol]

I will try and keep this simple so you can understand, the 29G ferry tank was only used for ferry operations but the MkIX which used the same fuselage was fitted with a 33G permanent tank in the same position, this is my argument, why fit a 29G ferry tank that doesn't create drag only to remove it and fit a 30G slipper tank that does?.

Firstly the Mk IX and its derivatives was fitted with a much heavier engine forward of the CofG so the designers could afford to fit the extra weight behind the pilot without exceeding the CofG limits.

More importantly the Mk IX fuselage is not the same as the Mk V fuselage. Just because externally it looks similar does not mean it is the same. Below are just some of blueprints I hold that cover the design changes that took place to convert the part number 34927 Mk V fuselage to a part number 36127 Mk IX fuselage.

Each one of these drawings is the result of the redesign of an existing part or the new design of a new part.

Except on new production aircraft, each and every one of these drawings requires a modification to an existing Mk V fuselage to convert it to Mk IX configuration.

Note that this drawing list does not include the addition of the fuel filler or plumbing or fuel valve and selector or any of the other changes that go with installing those rear tanks.

Just because they were able to design and fit these changes to create the Mk IX does not mean they could have done them earlier when designing the Mk V. Without the bigger engine to drag the CofG forward and to drag the whole assembly through the sky there was no way these changes could have been used.

 

[MiTasol]

So simply increasing the original MkVIII/Seafire MkIII tank by 9 Gallons is out of the question yet they were able to design it to take not only four Hispano's but another complete cooling system for all the two stage Merlins?.

According to the design staff at Supermarine YES or they would have done it.

Plus it would have required design changes and modifications that had not been created when the Mk I, II & V were designed and manufactured.

The design staff at Supermarine were not imbeciles.

 

[PAT303]

With regard to the Seafire, the Griffon engined Mk.XV was the first variant to be fitted with the leading edge wing tanks.

The MkIII was the first, I even posted a photo of it.

 

[PAT303]

According to the design staff at Supermarine YES or they would have done it.

Plus it would have required design changes and modifications that had not been created when the Mk I, II & V were designed and manufactured.

The design staff at Supermarine were not imbeciles.

Sydney Cotton did it, that's probably the reason why he wasn't popular, instead of making excuses he just made it happen.

 

[PAT303]

So again I ask, what is in that inboard space that prevented it being used for fuel?

Probably the same thing that prevented the rear fuselage space being used for fuel, even after the Americans proved it could be done.

 

[tomo pauk]

The MkIII was the first, I even posted a photo of it.

No, not the Mk.III...

 

[Reluctant Poster]

This video has the best explanation of the Spitfire PR IV fuel system I have seen. One of the interesting points made is that the original examples did had a 29 gallon tank behind the pilot but that it was removed in favor of increasing wing tankage in order to improve handling. Also note that the early version didn't have the radio installed.

View: https://www.youtube.com/watch?v=7E0IVD20Gr4

Here is the history of the other early PR Spitfires

View: https://www.youtube.com/watch?v=2_WgHLUuaa8
Note that Spitfires fitted with the 29 gallon tank did NOT have a radio

 

[Reluctant Poster]

No, not the Mk.III...

An interesting series of posts on the MKIII. I forgot to include the link:

Spitfire mkiii 1/72???

Are there any conversion sets out there for a spitfire mkiii in 1/72?

www.britmodeller.com

 

[Reluctant Poster]

Probably the same thing that prevented the rear fuselage space being used for fuel, even after the Americans proved it could be done.

The Americans didn't prove it could be done until 1944. In the meantime they had to use Spitfires to make up for their slow production of useful fighters.

 

[EwenS]

The MkIII was the first, I even posted a photo of it.

You posted a photo of a diagram purporting to show it. But other evidence suggests it is wrongly labelled as the Mk.III, even though it purports to come from the FAAM and has been published elsewhere. Perhaps the problem lies with the interpretation of the caption in the bottom LH corner which is referring to the wing fold mechanism first seen on the Seafire III and carried forward to the Seafire XV & XVII.

M&S p 540 has a table I top right the Table of weights states "Fuel in the fuselage tanks 84 galls." Table II lists weights for drop tank options. No mention of wing tanks.

M&S specifically note the existence of the wing tanks on the MK.XV. And they publish that diagram you posted (with some additional detail) in the Mk.XV section not the MK.III.

David Brown in "Seafire, the Spitfire that went to Sea" says this about the MK.XV -

"To the Spitfire VB-based fuselage and the L.III folding wings were added the enlarged fin and rudder of the Spitfire VIII, with that Mark's retractable tail-wheel, wing root fuel tanks from the Spitfire IX, the Spitfire XII's engine installationa nd auxiliaries, but with a solely naval Griffon variant."

Appendix I of that book lists the fuel capacity of the Merlin engined Seafires as 85 gal in two fuselage tanks, plus drop tanks. It lists the mk.XV & XVII as 80.5 gal in fuselage tanks, 19.5 gal in wing root tanks for a total of 100 gal, plus drop tanks.

Warpaint No 20 "Supermarine Seafire, Griffon engined variants" by Geoffrey Bussy puts it this way:-
"....The problem of sufficient fuel remained unsolved, with the Mk.XV, although two extra leading edge fuel tanks were introduced, providing 9 1/2 gal each. Internal fuel capacity tose to 101 gal....".

 

[Shortround6]

And we can ignore the history of the P-36/P-40 and it's behind the seat tank.
The tank was always there. Actual capacity changed a bit. What the pilot was supposed to do with it (how he flew the plane) varied considerably over the years depending on which engine was stuck on the nose of the plane.
This varied from the P-36/Hawk 75 where acrobatics were banned unless most of the fuel in that tank was used to the P-40F/L where the pilot was supposed to keep 25 gallon of fuel in the tank at all times except to make it home in an emergency. The Heavier Merlin engine needed the 25 gal of fuel in the rear tank for CG reasons. P-40Ms and Ns with Allisons went back to using up all the fuel in the rear tank and using the either the forward wing tank (if fitted) or the main tank (if forward tanks was not fitted) as the reserve tank.

The two videos show the progression and show problems with the rear tank on the Spitfire. Yes they yanked 40lbs of ballast out of the rear of the fuselage for the 29 gallon tank. Also be aware of prop and engine changes affected CG issues. Also the radio fit and change in oil tankage.

A lot of stuff to consider above "they had room for it! shove it in there!"

 

[MiTasol]

That statement is only 25% true!

The 66.5 gal wing tank (in each wing) that was first installed in the PR.IV Type D (Special LR) .... ran from rib 4 (not rib 1) to rib 21, leaving the space between ribs 1 & 4 "empty".

Which automatically means that all the guns were removed as they normally passed through the area outboard of rib 8.
The weight of fuel and cameras carried would have been around the same weight as the removed guns and ammo.

There is a diagram showing the layout on p243 of M&S (bottom left).

I am not familiar with that document - please expand the title. I cannot think of any RAF Air Publication that could be abbreviated to M&S.

So again I ask, what is in that inboard space that prevented it being used for fuel?

There is a lot of hardware in that area that maintenance staff need to access on a regular basis. The attachment hardware for the main landing gear pintles being the most important and those are inspected regularly and after any heavy landing. The area can be inspected with the cowls off. To inspect it when the area is filled with a tank would require removing the wing and tank for access.

The MkIII was the first, I even posted a photo of it.

You posted a picture of the SEAfire Mk III which is Supermarine type 358 and is a totally different aircraft from the Spitfire III which was the Supermarine type 330 and designed long after the Mk V which was type 349.

 

[MiTasol]

Sydney Cotton did it, that's probably the reason why he wasn't popular, instead of making excuses he just made it happen.

and he stripped out all the guns, gun heating, gun mounts, ammunition, radios and other things that were considered essential in a fighter aircraft.

 

[MIflyer]

Here is some info I found somewhere on 8th Air Force escort ranges.

 

[drgondog]

Here is some info I found somewhere on 8th Air Force escort ranges.

View attachment 788029

That is from the 8th AF Tactical Development doc, pg 97. It is confusing for multiple reasons, namely the dates are incorrect if intent was to cite Escort Range vs Fighter Mission for planning purposes. The accepted FAREP documents cite both with the Fighter Mission straight line single ship examples.

Second the dates are incorrect with respect to actual operational dates for the individually accepted tanks. For example 108gal Bowater tanks were initially delivered in September but 56th FG for example first used them 'Group wide' in late October, the 150gal flat tank was delivered in January but not operational 'Group wide' until Big Week, The twin pylon P-47D conversions were dribbling out of Burtonwood BAD1 in January, but first complete mission with twin pylon (mods and D-16s) weren't until mid March with 2x108gal tanks.

 

[EwenS]

Which automatically means that all the guns were removed as they normally passed through the area outboard of rib 8.
The weight of fuel and cameras carried would have been around the same weight as the removed guns and ammo.

Agreed

I am not familiar with that document - please expand the title. I cannot think of any RAF Air Publication that could be abbreviated to M&S.

It was a reference to the book "Spitfire The History" by Morgan & Shacklady (hence the M&S abbreviation), which was what I immediately had to hand.

There is a lot of hardware in that area that maintenance staff need to access on a regular basis. The attachment hardware for the main landing gear pintles being the most important and those are inspected regularly and after any heavy landing. The area can be inspected with the cowls off. To inspect it when the area is filled with a tank would require removing the wing and tank for access.

Yes, that was the bit I had identified as noted in my earlier post. But I wondered what else.

It regularly comes up in discussions about putting more fuel in the Spitfire about using this area inboard of the wing tanks on later Spitfire / Seafire variants. PAT303, amongst others, seems to be unaware that much of it was not used even on the PR aircraft. Given that the designers were not idiots, there had to be a good reason for not using it.

 

[MIflyer]

For example 108gal Bowater tanks were initially delivered in September but 56th FG for example first used them 'Group wide' in late October,

One thing I have wondered about is just how interchangable the different tanks were. For example, the P-47 had that "flat" 108 gal belly tank that I do not think that was used on any other aircraft. Of course its design was to accommodate that low hanging belly of the P-47.

Also no mention of the 165 gal steel drop tanks Lockheed was building. That Av Week article is dated June 1943, so presumably they were in full production before then. Perhaps they were reserved for the Pacific?

The early drop tanks used on Hurricanes had built-in pumps to get the fuel out. I wonder just when the approach of using the exhaust from the the vacuum pump was adopted? Since we had drop tanks long before the RAF I assume it was a US invention.

I have often thought that I'd like to write a book on The Other Stuff:

1. Drop Tanks
2. Radios
3. Oxygen Systems
4. G-Suit Systems
5. Environmental Control Systems
6. Automated Controls

The collective impact of all that Other Stuff was enormous.