a Spitfire Mk. IX question

[cag_200]

besides the 20 mm canon there seems tobe a stub.

What is it ? Its not a UHF sensor, seen on jets.

Is it some cooling system for the gun?

Edited February 24, 2009 by cag_200

[Jennings]

Are you talking about the second stub for the 20mm? The wing was designed for twin-20's. I'm not a Spit expert, but I believe there was at least one variant that had the dual 20s in ti. That's what that is in any event. Some marks had the 20mm outboard and some had it inboard, but AFAIK all had provision for dual mounts.

J

[cag_200]

"Some marks had the 20mm outboard and some had it inboard"

thanks Mr. Jennings

sounds sufficient enough to me.

Rgds,

Duncan

Edited February 24, 2009 by cag_200

[jrallman]

in that illustration you posted, the inboard cannon is installed, the outboard is not. there are two troughs for ammo, the inboard using the forward trough and the outboard using the aft trough. sometimes they would install just one cannon and use double the ammo load for it.

[cag_200]

thx dewd !

[Chuck1945]

How much data do you want?

The answer to your question is that the gun arrangement you note is dependant upon the wing. Most common for the IX was the 'C' wing as used in both your drawing and photo. The inboard position is a 20mm cannon, and the stub covered the position originally designed to carry a second 20mm. Further outboard of the cannon, there were also 2 x .303 machine guns.

You mention the cannon appearing in the outer position with a stub on the inside. This is the later 'E' wing that had a .50 machine gun in the stub position, a 20mm cannon outboard and did away with the 2 x .303 guns.This was more common on the Spit XVI and Spit XiV then on the Spit IX.

[Edgar]

What everyone calls the "C" wing, on the IX, was, in fact, the "universal" wing. This meant that it could take 4 x .303" (but never did); 1(or 2 - rarely, if ever) x 20mm cannon + 2 x .303" Brownings (known as "C" armament,); 1 x 20mm cannon + 1 x .5" Browning (known as "E" armament.) The two stubs, and the outer m/g panels were always in place, no matter what armament was fitted.

In the "C" wing, the 20mm cannon occupied the inner position of the bay (as you see above,) with the outer compartment empty, and the stub filled by a (usually wooden) bung.

For the "E" armament, the cannon was moved to the outer part of the bay, with the inner compartment occupied by the .5" m/g. As well as moving the cannon out, it was moved back, so that the ammunition fed out of the rear tray, while the .5" took its ammunition from the front tray. The .5" was moved forward because cocking it was difficult (and painful) for the armourers, since they tended to skin their knuckles on the rear of the gunbay, if the gun was in the rear position.

Later Marks (XVIII & some XIV) only had "E" armament, while the 22 & 24 had 4 x 20mm in a totally new wing.

There are a few oddities and anomalies, but that, basically, is it.

Edgar

Edited February 24, 2009 by Edgar

[agboak]

Almost: the universal wing was not originally designed to take the E armament, and when modified to do so it was no longer universal.

It was specifically designed to take the 4x20mm, which the RAF had chosen several years previously as their standard armament. However, this proved too heavy for the delicate Spitfire, badly affecting its handling and (to a lesser extent) its performance, so the service reverted to the 2X20 and 4X0.303. This was a great disappointment to the Admiralty, who were expecting the Seafire to take on the armoured Bv 138 shadowers. Initial deliveries of the Mk.Vc to Malta on the USS Wasp were with all four cannon: the Takali units rapidly removed two of them (often the inboard pair, strangely enough) but the Hal Far units seem to have retained theirs. One of the South African units in Italy adopted the 4x20mm cannon for ground-strafing duties with their Mk.Vcs. In Australia at least one Mk.VIII was fitted with four cannon to intercept Dinahs: a self-defeating modification, as was proven in practice.

[cag_200]

always useful to me.

I also found this site.

http://www.historyofwar.org/articles/weapo...tfire_mkIX.html

[Grant in West Oz]

Almost: the universal wing was not originally designed to take the E armament, and when modified to do so it was no longer universal.

<snip>

In Australia at least one Mk.VIII was fitted with four cannon to intercept Dinahs: a self-defeating modification, as was proven in practice.

The universal wing was designed to be strong for higher speed manoeuvring, carry bombs and a variety of arms. The adaptability of the design is what makes it universal.

I refer you to pps. 283 & 334 of Spitfire the History, Morgan & Shacklady Key Books. In the hand written Table 1 under the diagram, notes 1 & 2. These tables refers to C and E armament options in the Universal wing for Mk.VIII & Mk.IX. As far as I can deduce, the sheeting over of the machine-gun positions (Mk.XVI) did not change the designation of the components.

The Australian method of intercepting Dinahs, learned during the use of Mk.VC's both here and India, was to fly with a half load of ammunition. The 'gunning up' and futzing about with wingtips was out of boredom due to little enemy penetration into Aussie airspace.

Please point me toward a reference I can find in the State Library of WA http://www.liswa.wa.gov.au/ to support your position.

G

Edited February 26, 2009 by Grant in West Oz

[Edgar]

As far as I can deduce, the sheeting over of the machine-gun positions (Mk.XVI) did not change the designation of the components.

The outer gun compartments weren't sheeted over; they remained accessible, just covered in still-removable panels, but without any exit holes, deflection "bumps," etc., for the empties. When the XVI had the fuselage tank installed, the compressed air tanks were moved to the former no.3 gun position, while oxygen tanks occupied the no.4 compartment. This applies only to the XVI (IX production ended very quickly after the war's end); some XIVs (and all XVIIIs) did have the outer panels all in one piece, consequently no m/g compartments.

Edgar

[agboak]

By universal I was referring to the ability to rapidly change the gun armament, as I understood this was the meaning of the name. If the term is taken to include the carriage of bombs, as indeed it is on the Hurricane, then yes this facility was retained on the e wing. The strengthening of the wing was part of a general upgrading of an acknowledged weak part of the airframe. The modifications needed to fit the 0.5 Browning initially came as a kit to frontline units (see " 2TAF Spitfire" and STH). Presumably it would always be possible to remove these modifications for reversion to other armament combinations, but it would hardly be the easy change of the original variant. Nobody seems to have tried it.

On early build (or modified) e wings it would have been possible to to revert ot 2x20+4x0.303, had anyone wanted to, but on later aircraft I understand at least some of the spaces were used to other equipment.

Note that it is said that the e wing was found to be weak when dive-bombing (see Mk.IX Profile), suggesting something specific about the changes that went beyond those previously necessary for an armament change. I don't know what these were, perhaps this is a question for Edgar. (Or indeed what they could be - I wonder if this is a fair comment on the e wing or a false lead on a universal Spitfire problem.)

Edited February 26, 2009 by agboak

[Grant in West Oz]

The outer gun compartments weren't sheeted over; they remained accessible, just covered in still-removable panels, but without any exit holes, deflection "bumps," etc., for the empties. When the XVI had the fuselage tank installed, the compressed air tanks were moved to the former no.3 gun position, while oxygen tanks occupied the no.4 compartment. This applies only to the XVI (IX production ended very quickly after the war's end); some XIVs (and all XVIIIs) did have the outer panels all in one piece, consequently no m/g compartments.

Edgar

Thanks for those corrections.

I've been pondering over the last few days, was the wing used on photo-reconnaissance Spitfires (Bowser-wing?) just a panelled version of the Universal framework, from behind the dural torsion-box?

If that's the case, then in considering all the other structural differences it truly was a 'Universal' wing. The swapping in and out of armament and other services would be the least of the variations possible.

Cheers,

Grant

[agboak]

I'm pretty sure that the modifications required to add the tanking and the solid leading edges made the "d" wing considerably different to the "c", and certainly not convertible back under normal service conditions (as opposed to warbird customising).

The early bowser wings were based on the Mk.I, then on the Mk.V - presumably initially the A/B armament version. I have not seen any comment distinguishing between the early Mk.V wing and the universal wing for the PR aircraft, it's an interesting thought. There'd be little need for the root strengthening mods, but the forward undercarriage rake would be helpful on the later variants. So is it safe to presume that single stage Merlin PR aircraft were based on the early wing, and later ones on the universal? Probably not...... but it should be a good starting point.

[Grant in West Oz]

iirc, the wing itself is the same from the spar back, it was the 'D' box, fuel bladders and pumping equipment which were signals along with the butt jointed plating.

The very early PR Spitties were lash-ups at unit level. They were based on the 4 mg wing, smoothed with spackle and very much an experiment. http://www.airrecce.co.uk/WW2/recce_ac/RAFAR.html Sid Cotton was a likeable rogue who exploited the system as a civilian. :) but the job was essential.

As far as structural mods, there must have been some to handle the constant alterations for cameras and fuel systems. But to be on topic, we should be talking about Mk.IX's and universal wings, etc., though they didn't appear to be markedly different to the weapon carrying wing. It was later when the short aileron PRMk.XI and PRMk.XIX where the fuel tankage was carried in the torsion (D) box.

I must admit my references are coming up short the more in-depth we get into this.

Great discussion.

G

[agboak]

I don't think any PR wing had the short aileron. Possibly the still-born Mk.VIII might have, but the Mk.XIX is basically a PR version of the Mk.XIV, and its wing retained the long ailerons of its Mk.V origins.

[Edgar]

The PR IV had the fuel-filled "D" box, as well; it was in the desert where it was discovered that vent pipes were needed at the wingtip, when one of the tanks split due to heat expansion. The forward portions of the ribs seem to have been different, too, being basically solid, but with holes to allow free flow to the fuel. However, occasional ribs had only a one-way door, which wouldn't allow fuel to return, presumably to stop fuel sloshing back during manouvres.

Edgar

[Grant in West Oz]

I don't think any PR wing had the short aileron. Possibly the still-born Mk.VIII might have, but the Mk.XIX is basically a PR version of the Mk.XIV, and its wing retained the long ailerons of its Mk.V origins.

No agboak, the production Mk.XIV had short ailerons, just like the prototypes. I'm using 'Supermarine Spitfire. Part 2 - Griffon-Powered' -MDF05 pp. 69, 70. as reference here, also well documented in STH.

Edgar, I'm aware of the baffling fitted to the rib assembly, it's interesting that they retained the wing-root tank as well.

The Mk.21 returned to long ailerons but that's on the Type Y laminar flow wing.

G

[agboak]

It was the Mk.XIX I was talking about, with basically a Mk.VD wing on a Mk.XIV fuselage. I agree that the Mk.XIV had short ailerons.

The Mk.21 wing was not "laminar flow". I believe it had the same section as previous Spitfires (certainly very similar), but a modified planform and redesigned internal structure to resist torsion. It was one example used in my aeroelastics course in the late 60s. The Mk.23 had a raised leading edge, which may well have been intended as some kind of "halfway house", but it was the Spiteful that had the so-called "laminar flow" wing.

[Edgar]

Aerofoil seaction, for the 21, was NACA 2200 series, same as the Mk.I, with the same incidence of +2 degrees at the root, but -1/2 degree at 18'5" from the c/l, not at the distance of the old wingtip join.

Edgar

Edited March 4, 2009 by Edgar

[Grant in West Oz]

It was the Mk.XIX I was talking about, with basically a Mk.VD wing on a Mk.XIV fuselage. I agree that the Mk.XIV had short ailerons.

The Mk.21 wing was not "laminar flow". I believe it had the same section as previous Spitfires (certainly very similar), but a modified planform and redesigned internal structure to resist torsion. It was one example used in my aeroelastics course in the late 60s. The Mk.23 had a raised leading edge, which may well have been intended as some kind of "halfway house", but it was the Spiteful that had the so-called "laminar flow" wing.

Busily whiting out lines in my references... or not.

g

[agboak]

If your reference says laminar flow wings on a Mk.21, I'd suspect other things in there as well. The first such wing was attached to a Mk.XIV fuselage, so perhaps this has lead to some confusion.