Spitfire PR IV - thoughts?

[elger]

Hello all,

 

I'm looking into the characteristics of a Spitfire PR IV. Specifically, I'm interested in an early IV, from the AA-serial range. The IV was the first factory built photo-reconnaissance type, and from what I gathered so far by looking at various photos of the type there seems to be some variation.

 

Some points I'd be interested in hearing y'all's thoughts on.

 

• The PR IV was the first factory built PR Spitfire with the "bowser" type D-wing. Since the vent pipes at the upper wing-tip surfaces were added after BP882 blew up, I don't think the aircraft I'm interested in had them, since that was lost in March 1942, before that incident I think. Photos of BP888 from 1943 show strengthening ribs typical of some Mk.Vs, but here again I don't think that my earlier subject had them (one of the IVs tested by the Soviets seen in the Ventura Publications book did not have them). What I'm interested in however is if this early "factory built" D-wing was different from later factory built D-wings as fitted to the PR XI and PR XIX, for instance. Were there differences, other than the vent pipes not fitted to the very earliest examples?
• There's a fair amount of reference material floating around regarding the cockpit layout of the PR XI and PR XIX. Was the cockpit layout of the PR IV similar - the boxes that operated the cameras, gauges for the extra fuel tanks, or was it different? If so, do any photographs or diagrams exist of the PR IV cockpit?

 

These are the two main questions I have - PR IV wing and cockpit details. I'd be curious what you think!

[Dave Swindell]

2 hours ago, elger said:

What I'm interested in however is if this early "factory built" D-wing was different from later factory built D-wings as fitted to the PR XI and PR XIX, for instance. Were there differences, other than the vent pipes not fitted to the very earliest examples?

I'd say definitely different, at least inasmuch as the different radiator and cooler layout meaning changes in the internal construction to accommodate them and the associated pipework. 

From a modelling perspective though, apart from the radiator and cooler changes, I doubt there would be much difference visible beyond the odd panel and rivet line.

[Andy Fletcher]

Hi Elger,

 

Here is what AP1565M says about differences in the fuel systems between the PR.IV and PR.XI:

 

PR.IV - the fuel system has two leading edge tanks, each of 66 gallons capacity, in addition to the normal main fuselage tanks. Each leading edge tank has a contents gauge on the instrument panel. The flow of fuel from these tanks is controlled by means of hand operated cocks on the port and starboard sides of the cockpit.

 

PR.XI - the fuel system has two leading edge tanks, each of 66 gallons capacity, in addition to the normal main fuselage tanks. Each leading edge tank has a contents. The flow of fuel from these tanks is remotely controlled by levers on the port side of the cockpit, the red lever being for the port tank and the green lever for the starboard tank. On later aircraft having the Merlin 70 engine, electric pumps are fitted in the bottom of the main tank and in each leading edge tank, to deliver fuel to the engine. These pumps reduce the capacity of each tank by ½ gallon. A 3-position selector switch, master switch and test buttons for the control of these pumps are mounted on a panel on the starboard side of the cockpit.

 

The main fuel tanks are pressurised by exhaust air from the vacuum pump, but an aneroid valve in the line delays pressurising until approximately 20,000ft is reached. A cock for by-passing air and restoring the system to normal venting when necessary, is mounted under the starboard side of the instrument panel. As pressurising impairs the self sealing of the lower tank, this cock should only be turned on when the fuel pressure warning lamp lights. In very warm weather, at high altitude, a “rich-cut” may occur with the tanks pressurised, and the pressure must be turned off.

 

 

The camera control unit and camera selector unit are in the same place in the PR.IV and PR.XI.

[DOD]

Hi Elger,

These are questions (plus others) I have been looking into as well for a build of AA810 in operation October, 1941.

 

I was wondering about when the wing vents were introduced. Do you have a reference to this BP882 blowing up?

 

Regarding wings my thoughts are that they were based on the wing construction of the mark that was in operation at the time. I don’t know much about the PRXIX but I think they are all a bit different. The PRIV seems to have the bumps over the wheel well and the PR XI does not. Here are my thoughts on the PRXI regarding panel lines.

 

 

Freddie Malcolm, PR IV Mount Farm 1941. This shows wheel well bumps.

 

This diagram appeared in a previous post showing bumps over the wheel wells.

 

It is titled Top Skin Plating. Can this be interpreted to determine the panel lines? I cannot make it out. 

Also there are the small blisters top and bottom on the port wing for the pump of the extra oil tank.

So I am still not sure what the panel line layout for the PRIV is. This other photo indicates that there were at least some panels under the wing. Were they the standard gun panels but with ejector holes covered?

 

I reckon then that the panel lines and bumps and blisters will be different between the three marks.

 

I also have not found anything specific about the PRIV cockpit. The photo of Freddie Malcolm shows the Type 35 camera controller but that is all I have seen.

 

I am a newcomer to this field but hope this might be of some help. At the same time if I have said anything that is noticeably wrong please tell me!

David

[Graham Boak]

The PR Mk.IV entered service before the strengthened wheel well roof, introduced on the universal wing (Mk.Vc).  Hence the bulges would be expected.  The Mk.IX was based on the 2-stage variants so I suspect that examples of the earlier wing were no longer in production for modification to the same standard as the Mk.IV D wing.   They will however have the bulges on the wheel doors, because the wheel sits lower so the doors have to be modified to fit flush.

[elger]

1 hour ago, DOD said:

I was wondering about when the wing vents were introduced. Do you have a reference to this BP882 blowing up?

 

 

In the chapter about the PR IV, Wojtek Matusiak in Classic Warbirds no. 10 discusses the type being sent to the Middle East. No specific date of the incident is mentioned, but BP882 reached Egypt in March 1942 according to the book (p.22) so presumably the incident happened after that.

 

Discussing modifications made at Abukir to the examples sent there, Matusiak writes

 

Quote

After a long period of heat in the sun, fuel could blow the wing tanks (as was the case with BP882). This led to the introduction of the de-aerating valves on top of the wing tips and these modified Spitfires, with full tanks these valves would spray fountains like a whale when taxiing (21).

 

 

 

[elger]

1 hour ago, DOD said:

Hi Elger,

These are questions (plus others) I have been looking into as well for a build of AA810 in operation October, 1941.

 

 

David

 

 

Hi David - Today I actually asked some of the folks who are restoring Spitfire AA810 via Facebook about these issues. They tell me that there are actually quite a number of "unknowns" about the type and they're discovering things as they restore the wreckage. They confirm some of the things above. Interestingly, they mentioned that the lower wing surface of AA810 was the same as a Mk 1 (including gun hatches!), but that the surface was different on top. I asked if they knew where the filler cap for the wing oil tank was located, but they haven't found that out yet.

 

As far as they know, the cockpit layout was very similar to the XI, but there was a lot of variation between individual aircraft.

 

www.spitfireaa810.co.uk

 

https://www.facebook.com/SpitfireAA810/

 

 

[gingerbob]

DOD's right- the PR.IV had the original main gear "stance", and therefore the bumps on the upper surface.  The PR.XI introduced the 'c-style' main gear, as Graham describes.