Spitfire III vs Hurricane II - which was a better place for a Merlin XX?

[wuzak]

Hi guys, I know we touched on this in another thread, which would have been a better long term bet for using the Merlin XX series - the Hurricane or the Spitfire.

In one corner we have the Hurricane II, the aircraft which was actually built. It desparately needed the performance upgrade that came with the XX and its new 2 speed supercharger. But was it enough to keep the Hurricane competitive?

In the other corner is an aircraft that only existed as a prototype - the Spitfire III. This had numerous modifications to the Spitfire, including retracting tailwheel and fully covered undercarriage. The Spitfire III first flew in March 1940 (possibly with a Merlin X, the first 2 speed Merlin).

With so many changes required, the III was put on the backburner, whilst the interim V took centre stage. With the single speed 45 and mostly unchanged airframe, the V could go into production very quickly, whereas the III could possibly take a while.

One of the reasons that the III wasn't persued was the lack of engines, the XX being early in its production run. A year later and the 60-series Merlins were being developed, so any thought of putting a XX into the Spitfire was now gone.

Regarding engine availability, some 4900 Merlin Mk Xs were built between 1938 and 1942 (according to Lumsden). Woul dthe X have proved more useful in Hurricanes and Spitfires than in Whitleys and Wellingtons?

So how good coule the Spitfire III have been? Anyone have any performance data - tested or projected?

How does the III compare with the V and the Hurricane II?

And would it have held its own against the Fw 190s and Bf 109Fs?

 

[drgondog]

Wuzak - I think the last question is yes but reflect that great performance at 20K+ was not the dominant battleground...

History tells us the critical battleground was over Great Britain between July 1940 and September. Whitley's and Wellingtons, in hindsight, were not as important as Hurricanes and Spitfires then.

 

[Shortround6]

I am confused a bit here, Merlin XX or just X ?

Main differences are the XX and the Hooker designed inlet elbow on the supercharger, different carburetor, and different gear ratios.

Main difference between the X and III is more power down low just as the main difference between an XX and 45 is more power down low.

 

[Greyman]

Did this graph up a while ago, Spitfire curves are from (what I believe to be) an RAE document, and the Hurricane curves are from A&AEE flight tests. Climb data was also given and the Merlin 45 climbs were better for both aircraft. Hurricane '45' was a converted Mk.I airframe.

 

[wuzak]

Spitfire III doesn't seem to gain as much as the Hurricane between the two engines at altitude.

 

[wuzak]

I am confused a bit here, Merlin XX or just X ?

Main differences are the XX and the Hooker designed inlet elbow on the supercharger, different carburetor, and different gear ratios.

Main difference between the X and III is more power down low just as the main difference between an XX and 45 is more power down low.

Merlin XX.

But if the Merlin XX was restricted because of production, or because of a need elsewhere, could the X have been a useful substitution?

 

[RCAFson]

Given the Spitfire II's production difficulties (first flight Summer 1939 but only 116 produced by end of Sept 1940), it seems likely that the highly modified III (first flight March 16 1940) would have been even harder to get into production so cancelling the HHII net result would have been no Hurricane IIs (which rapidly formed the bulk of FC by mid 1941) and no Spitfire IIIs until sometime in 1941. The decision to produce the III was put on hold pending Merlin XX production results but then, as usual, RR performed wonders and got the XX into full production. 1000 Spitfire IIIs were ordered in Oct 1940 so there were enough engines for the Hurricane II and the Spitfire III which was then cancelled when the 45 came along, in favour of the V.

The III featured a very short wingspan, and the reduction in wing area would probably have made it less versatile in carrying DTs and bombs.

Here's the Hurricane IIa inserted into Greyman's chart:

 

[Shortround6]

What was different about the Spitfire II that gave such great difficulties in production vs a Spitfire I?

A number of Spitfire Vs were re-engined Spitfire Is and IIs and a few Spitfire IXs were modified Spitfire Vs, A least one Spitfire MK IX may have started life as a Spitfire I?

Or was it a case of the Factory assigned to build the Spitfire II was having troubles producing anything and would have produced NO MORE Spitfire Is in the same time period?

 

[RCAFson]

Did this graph up a while ago, Spitfire curves are from (what I believe to be) an RAE document, and the Hurricane curves are from A&AEE flight tests. Climb data was also given and the Merlin 45 climbs were better for both aircraft. Hurricane '45' was a converted Mk.I airframe.

It is interesting that the Hurricane/45 weighs about the same as with a Merlin III.

 

[RCAFson]

What was different about the Spitfire II that gave such great difficulties in production vs a Spitfire I?

A number of Spitfire Vs were re-engined Spitfire Is and IIs and a few Spitfire IXs were modified Spitfire Vs, A least one Spitfire MK IX may have started life as a Spitfire I?

Or was it a case of the Factory assigned to build the Spitfire II was having troubles producing anything and would have produced NO MORE Spitfire Is in the same time period?

There were problems getting the Nuffield (Castle Bromwich) Spitfire II into production but the Spitfire I was no great shakes for production either. In July (June 22 to July 27)1940 166 Spitfires were produced of which 143 were Mk Is. In the same time frame 322 Hurricanes were produced.

Production for Aug - Oct. Hurricane/Spitfire 1 /SpitII (Spit II aprox due to monthly versus weekly figures)

June 22-Jul 27 322/143/23
Jul 28 - Aug 31: 277/153/37 (Some Hurricane Mk II included)
Sept 1 - Sept 28: 225/92/56 (32 Hurricane Mk II included)
Sept 29 - Nov 1: 239/120/ (All Spitfires listed together Some Hurricane Mk II included)
total during BofB: 1063/500/116
Data from Mason.

An interesting comparison

Hurricane IIa first flight = June 1940 and production = Sept 1940.

Spitfire IIa first flight = summer 1939 and production = June/July 1940.

 

[RCAFson]

Did this graph up a while ago, Spitfire curves are from (what I believe to be) an RAE document, and the Hurricane curves are from A&AEE flight tests. Climb data was also given and the Merlin 45 climbs were better for both aircraft. Hurricane '45' was a converted Mk.I airframe.

The Hurricane/45 data seems to indicate that the engine was being run at 2850rpm, hence the low FTH. Hawker data (via Mason) shows that the initial performance data for the HHIIA was also at 2850rpm as speed was 342 at 17,400ft while the prototype managed 348 at 17,500ft.

 

[Shortround6]

There were problems getting the Nuffield (Castle Bromwich) Spitfire II into production but the Spitfire I was no great shakes for production either. In July (June 22 to July 27)1940 166 Spitfires were produced of which 143 were Mk Is. In the same time frame 322 Hurricanes were produced.

It doesn't really answer the question. Castle Bromwich may have had trouble getting ANY version of Spitfire into production ( or even the Hurricane) until management was changed.

What were the differences between the MK I and MK II Spitfire that make the MK II harder to build?

 

[herman1rg]

This could become a very interesting discussion

 

[wuzak]

The Hurricane/45 data seems to indicate that the engine was being run at 2850rpm, hence the low FTH. Hawker data (via Mason) shows that the initial performance data for the HHIIA was also at 2850rpm as speed was 342 at 17,400ft while the prototype managed 348 at 17,500ft.

So, the Hurricane II was projected to to manage 342 (the Hurricane IIb is on the chart, and it was able to do pnly 330mph, and was much the same aerodynamically). The prototype supposedly did 348mph.

So how does this compare with the Spitfire III prototype? What was it capable of? 350mph. No wait, the Spitfire prototype did that! Maybe 400mph?

 

[wuzak]

What was the difference with the Spitfire III wing? And why were they changing it?

 

[RCAFson]

It doesn't really answer the question. Castle Bromwich may have had trouble getting ANY version of Spitfire into production ( or even the Hurricane) until management was changed.

What were the differences between the MK I and MK II Spitfire that make the MK II harder to build?

The problem seems to have stemmed from the complex nature of the Spitfire airframe and the resulting difficulties in placing it into mass production. What is apparent is that the UK spent far more money on the Spitfire from 1938-42 to ensure volume production, including 4 million pounds on Castle Bromwich alone, than was spent to ensure volume production of the Hurricane. Yet it was not until the 4th qtr of 1942 that Spitfire production exceeded Hurricane production, as even though UK Hurricane production was declining in 1942, Canadian production was climbing as the Packard Merlin came into production (If Henry Ford hadn't been so untrustworthy Cdn production would have been somewhat higher).

Canadian Hurricane production is a good example of how the easier to build Hurricane could be brought into production. Agreement was reached in early 1939, an example aircraft was received in March 1939 and the first prototype was built by Jan 1940.

 

[Greyman]

Here's the Hurricane IIa inserted into Greyman's chart:

The RAE Hurricane IIa/IIb data you referenced is from the A&AEE flight test I have in the chart - but with a new, updated position error correction figure. While the updated RAE figures may be closer to to the aircraft's actual speed in reality and a better indication of its performance compared to other aircraft - it doesn't invite a direct comparison to the Hurricane '45' figures, which still use the old PEC figure.

Since the RAE never calculated the A&AEE Hurricane '45' figures with the updated PEC, I charted both original tests with the old PEC for a direct comparison.

The Hurricane/45 data seems to indicate that the engine was being run at 2850rpm, hence the low FTH.

Whoops, good eye. I accidentally put three plot points 2000 feet too low and it messed with the Hurricane '45' curve. Image updated.

 

[Shortround6]

The problem seems to have stemmed from the complex nature of the Spitfire airframe and the resulting difficulties in placing it into mass production.

The complex nature may not have been so complex. There were a lot of minor changes on what were essentially the same parts. This prevented tooling from being finalized. Lord Nuffield was a stickler for getting the tooling the finalized so Castle Bromwich could operate with the absolute minimum of skilled labor. He is supposed to have told Lord Beaverbrook that he could have Spitfires OR he could have changes but not both.

Sticking with steel tube construction rather than gearing up to produce monocoque would certainly help production in the short term, but there is only so far you can take steel tube construction. Supermarine had been airily told to subcontract what they couldn't make themselves but nobody knew who to subcontract to. There was no aircraft subcontracting industry.

 

[Aozora]

This myth about "complex construction" is just that, a myth: the most complex part of the Spitfire's construction was the wing, and that was mainly the spar, which required precision. Otherwise that elliptical wing and the parts used to build it were not much of a struggle - why?

Automobile manufacturers had been mass producing cars with complex double curved surfaces for years, using controlled presses, or even hand shaping over formers. Take a look at some of the shapes of a relatively common car such as the Austin Ten:

Same with ship builders, who could bend steel or manufacture complex castings of all sorts almost from the start of the industrial era - either way the industry was completely at home with fabricating and mass producing parts incorporating complex shapes. While there were lots of lovely compound curves on the Spitfire there was nothing that couldn't be handled relatively easily.

The difference with aircraft construction was that far greater precision was required fitting all of the parts together because even relatively small variations could lead to anything from loss of performance to catastrophic structural failure because of the aerodynamic loadings the aircraft was subjected to. There's a huge difference between an Austin Ten trundling along a road at its maximum speed of 60 mph and a Spitfire diving at 450 mph IAS or looping at 200 mph.

What also happened is that the entire British aircraft industry found the transition from braced steel tube and fabric construction to all metal monocoque a struggle; as has been mentioned elsewhere Fairey, for example, had great difficulties starting Battle production as did the sub-contractor Austin.

Hawker avoided that problem for a few years by continuing with the tried and true methods, which did make the Hurricane easier to build. What should also be noted is that when Hawker did use an all metal monocoque structure on the Typhoon one prototype suffered from catastrophic rear fuselage failure, while production Typhoons had to have the rear tail join reinforced with fishplates right through its production. Yet, there were still tail failures at that joint so clearly Hawker also found it difficult to adjust.

When RCAF compares production rates of the Spitfire vs the Hurricane what he did not mention is that the Supermarine Southampton factory was bombed out in September 1940, with the loss of several already built Spitfires, nor does he mention that this led to the dispersal scheme where the manufacturing of Spitfires was farmed out to many small sites. As I have said elsewhere, had the Spitfire been as complex as some like to make out the dispersal scheme would have been a failure.

 

[RCAFson]

The RAE Hurricane IIa/IIb data you referenced is from the A&AEE flight test I have in the chart - but with a new, updated position error correction figure. While the updated RAE figures may be closer to to the aircraft's actual speed in reality and a better indication of its performance compared to other aircraft - it doesn't invite a direct comparison to the Hurricane '45' figures, which still use the old PEC figure.

Since the RAE never calculated the A&AEE Hurricane '45' figures with the updated PEC, I charted both original tests with the old PEC for a direct comparison.

Does the Spitfire data use the old or new PEC data, or did it remain unchanged?

Whoops, good eye. I accidentally put three plot points 2000 feet too low and it messed with the Hurricane '45' curve. Image updated.

Are you sure you updated it?