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Early Spitfire Oxygen Economiser


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While searching for something else I stumbled upon this paper.

 

https://www.aerosociety.com/media/4847/a-brief-history-of-flying-clothing.pdf

 

What I found interesting was the following brief section on breathing systems, and I quote with my bold highlight:

 

2.2.1 Breathing systems

Unlike the Germans who, in 1936, had developed the Auer A-824 demand regulator, British oxygen systems still used the constant-flow approach which was, of course, wasteful with oxygen being supplied during the necessary inhalation phase and, unnecessarily, during exhalation. In essence, aircraft were carrying over twice the amount of oxygen storage (in heavy cylinders) than was needed with the resulting increases in aircraft weight, particularly bombers with their longer duration sorties. All aircraft, at that time, with their limited engine power needed every possible reduction in the weight of ancillary equipment to carry higher bomb loads or, for fighters, for better performance. In 1939 the RAF Physiological Laboratory, formed in August 1939 and then working as an RAE Department (originally named 60 Department, subsequently renamed 17 Department), and the RAE Instrument & Physics Department seized the moment to produce a system that had been long in gestation, but considered unnecessary by the RAF in the bi-plane era, that would eliminate this particular problem. The RAE design and build of the prototype Economiser – nicknamed the ‘Puffing Billy’ – was completed by mid-March 1940 and lab and flight tests had confirmed that the PB Economiser was satisfactory from a physiological view-point (Figure 19) (RAE, 1940). The weight saving on an aircraft of the Wellington type by the reduction in number of oxygen bottles was some 500lbs. By September 1940 it was decided that 1000 Economisers should be retro-fitted, mainly to Spitfires, with all new builds fitted in production. Bombers were fitted with the developed Mk II and were used throughout the war (RAE, 1941). It remained in service in the Avro Shackleton and Jet Provost Mk III well in to the 1970s.

 

This twigged my interest in trying to determine when the economiser was introduced to the Spitfire and whether this also coincided with a change from the rigid bayonet hose connection forward right of the pilot to the flexible corrugated push in type, that became the standard in later Spitfire Marks.

 

The economiser is quite a bulky object and was fitted behind frame 13. As shown below in this Mk V layout.

 

Spitfire Mk V Oxygen System

 

On the non-economiser Spitfire, the oxygen path was high pressure supply from the cylinder mounted behind the pilot on the starboard side through the stop cock to the pressure regulator mounted top port side of the instrument panel. The regulated low-pressure oxygen then went behind the instrument panel to the starboard side to the rigid bayonet fitting forward of the pilot to which he would fix his mask’s hose.

 

In the economiser version, low pressure regulated supply returned from the port side instrument panel to behind the pilot to the economiser fitted between frames 12 and 14 before coming forward using a flexible hose making a push in connection available beside the pilot on the starboard sidewall.

 

Now why is this of interest? Well with Eduard’s new Mk II and late version possibilities, had these converted to an economiser and if so moved away from the original forward oxygen hose bayonet fitting to the more usual corrugated hose type. My thoughts are that if you are modelling a late 1940 to 1941 version YES. A Battle of Britain period probably NO.

 

What’s your thoughts?

 

The above paper references the following. Does anyone have a copy they can share or may be able to direct me to where I can source one?

 

RAE (1940) Oxygen Economiser Apparatus. Test of Economiser Unit Mask Valve RAE Inst. Tech Note 413, Royal Aircraft Establishment, Farnborough

 

Ray

 

 

 

 

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An interesting find Ray. The diagram suggests that the economiser was attached to the flare chute tube; I thought this had been moved to the upper rear starboard side of the fuselage by was removed by the time the Mk V was in production, or was it during (?). I wonder what happened to the economiser location when that happened, if it was attached to the tube.

 

In terms of the references, have you tried a search of the UK National Archives?

 

 

 

 

 

Edited by Peter Roberts
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10 hours ago, Peter Roberts said:

The diagram suggests that the economiser was attached to the flare chute tube

 

Maybe in this drawing's case yes. Planned to be mounted to what ever was convenient be it parachute flare or life raft chute. I have seen images on later marks where it is mounted mid-wall on the starboard sidewall just aft of frame 12. The flexible hose then snaking back through the lower right of the frame 11 bulkhead and up to be clipped onto the sidewall for the pilot's use. 

 

Without better information, and if modelling a 1941 Mk II, I would represent this style of oxygen system rather than the total loss early system.

 

Ray

 

 

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Ah, that triggers one imprecise memory: I've seen some comments in ORBs, I think approximately May '41 (plus or minus two years!) about trying out the new oxygen system.  I guess I'll have to see if I can find any note I took for myself and report back...

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14 minutes ago, gingerbob said:

I guess I'll have to see if I can find any note I took for myself and report back

 

Thanks Bob, greatly appreciated!

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9 minutes ago, spitfire said:

Looking through my notes I did find this

 

Thanks Dennis,

 

Good drawing showing the later install option with the usual front oxygen cylinder moved to the rear. As the drawing notes state: "Re-arrangement  of oxygen system when 29 gal. fuel tank is fitted and 170.gal drop tank". 

 

The little schematic in the bottom right corner is excellent showing the typical install with the high pressure supply going to the pressure regulator (mounted in the instrument panel) and then heading back to the economiser and ultimately to the pilot's mask.

 

Ray

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OK, here's one thing: Mod 302 (Class 2) To introduce Oxygen economiser Mk.II (applicable to I/II, in other words "all") first discussed 19/9/40, then Jan 41, "Cleared" July 41.

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