Spitfires. How good/bad at ground attack

[nuuumannn]

The Spitfire III also had clipped wings.

Its wings weren't 'clipped', i.e. reduced in length from a greater span - well, technically they were as the first Mk.III was a Mk.I plucked from the production line and refined. They were built shorter in that they were designed from the outset to be a shorter span than previous ones, so you're partially right...

 

[Mike Williams]

It replaced the F IX in production.[...] As Alfred Price states, it was not known as the LF IX until the HF IX appeared in 1944.

I'm not so sure how accurate that statement attributed to Price is. As noted just above, 611's April 1943 Operations Record Book lists Spitfire IX (LF) as the aircraft type on operations. See also the Spitfire L.F. IX data card dated 28.10.43. Certainly the Merlin 66 engined Spitfire went by a variety of names. A quick browse of Spitfire IX combat reports from 1943 shows mention of Spitfire IX L., Spitfire IX (66) and Spitfire IX B. Incidentally, Spitfire IX H is also listed as an aircraft type in spring 1943 such as seen in this combat report from 17/5/43.

 

[Geoffrey Sinclair]

Merlin 66 and LF Spitfire production both began in February 1943. Engine production stopping in April 1945, LF Spitfire in August 1945.

Looking at the totals there were 6,366 Merlin 66, for 5,127 LF VIII and IX, which gives around a 20% spare engines, similar to the RCAF order for Merlin 29, 480 engines for 400 aircraft and less than the early war USAAF at over 30%. This leaves little room for conversions.

In terms of total Spitfire production the LF made up two thirds of the 1944 total. In percentage terms they went over 80% in October 1943 to March 1944, over 70% April to August 1944, then declined to around a quarter in March 1945. In terms of mark VIII and IX the LF version represented 76.5% of all production.

First HF.IX in March 1944, first HF.VIII in May 1944.

 

[nuuumannn]

The LF IX had nothing to do with Coningham or the LF V.

I really should do more reading before I answer... So going back to this, Yes, it does. Coningham did in fact have something to do with the LF.IX, albeit by proxy via the LF.V. Here's what Morgan and Shacklady has to say,

"The impetus given to large scale production [of the LF.IX, my addition] came from Air Marshal Coningham, C-in-C Air Forces in the Western Desert. He originally asked for 'massive' supplies of LF.VB/VCs as 80% of his operations were at low altitude."

"There was little point in building and shipping additional Mk.Vs to the Middle East as future Spitfire production was devoted to the Mk.IX, and the result was a low altitude variant to meet requirements."

As Alfred Price states, it was not known as the LF IX until the HF IX appeared in 1944.

Not entirely accurate apparently, see above in Mike Williams' post. The HF designation might have come around at a similar time as the LF designation though, but a year earlier, as per a report written at Boscombe Down dated 3 August 1943 titled "Spitfire HF.IX EN524". However, according to Morgan and Shacklady the first "LF.IX" was a converted Mk.VC MA648, which was fitted with a Merlin 66 on 23 May 1943 by Rolls-Royce, which contrasts with the ORB entry above...

 

[Conslaw]

It seems like a lot of fighters, not just the Spitfire, often flew ground support missions with bomb-loads well under what they were rated to carry. P-47s flying with 2x500 lb bombs vst its rated load of 2500 lbs, for example. In WWII, P-51s would carry 2x500lbs, but In Korea, they would carry 2x1000. Was there a particular reason for this?

 

[pbehn]

It seems like a lot of fighters, not just the Spitfire, often flew ground support missions with bomb-loads well under what they were rated to carry. P-47s flying with 2x500 lb bombs vst its rated load of 2500 lbs, for example. In WWII, P-51s would carry 2x500lbs, but In Korea, they would carry 2x1000. Was there a particular reason for this?

Maybe the length and quality of the take off strip?

 

[fastmongrel]

Maybe the length and quality of the take off strip?

Possibly because Bomber Command had first call on 1000lb bombs in Europe.

 

[Ovod]

It seems like a lot of fighters, not just the Spitfire, often flew ground support missions with bomb-loads well under what they were rated to carry. P-47s flying with 2x500 lb bombs vst its rated load of 2500 lbs, for example. In WWII, P-51s would carry 2x500lbs, but In Korea, they would carry 2x1000. Was there a particular reason for this?

Hanging more ordnance from an aircraft would effect combat radius, I would have thought? Both the Spitfire and P-39 had very short endurance at the best of times - a single 500Ib bomb would not be good for combat range - 2, or even 3 such bombs would cripple such aircraft completely. Good for bombing the airfield main gate perhaps...

 

[nuuumannn]

Good for bombing the airfield main gate perhaps...

Good thing they were operating from bases in formerly occupied territory against the retreating Germans, then. It is worth noting that with their bomb loads operating from these bases in places like Belgium and the Netherlands they were reaching far into Germany. How far do you need them to go to be effective against a retreating enemy?

 

[pbehn]

Good thing they were operating from bases in formerly occupied territory against the retreating Germans, then. It is worth noting that with their bomb loads operating from these bases in places like Belgium and the Netherlands they were reaching far into Germany. How far do you need them to go to be effective against a retreating enemy?

Range maybe useful but in close support of ground forces it is always best to close it. The Typhoon and P-47 had enough range to cross the 100 miles of the English Channel but that didnt mean constructing airfields in the beachhead wasnt a good idea.

 

[pbehn]

Possibly because Bomber Command had first call on 1000lb bombs in Europe.

Possibly, but I was thinking specifically about the Typhoon, it could carry a lot more than it did when doing CAS, but there were issues with operating from steel mat airfields and tyres that "shimmied" etc.

 

[Conslaw]

I'm sure the runways were an issue. The P-47 loved long runways. The Runway at Ie Shima was a bit over 5,000 feet long, but taking off with a P-47N with 2,500 bombs and fuel for a long mission was still touchy.

 

[nuuumannn]

The Typhoon and P-47 had enough range to cross the 100 miles of the English Channel but that didn't mean constructing airfields in the beachhead wasnt a good idea.

Yup, both these types operated from the same captured airfields as the Spitfires. Why bother flying them from the UK when you can get better operational flexibility and faster response time over in the continent?

Without being too obvious, the P-47 and Typhoon made far better ground attack aircraft, but that shouldn't overshadow nor diminish the efforts of the Spitfire pilots that flew it in that role.

I was talking about this with a British friend of mine recently and I remarked that when I was in France a couple of years ago we visited a few cemeteries around the Normandy area and almost all of them have Typhoon pilots interred within. Loss rates were high, sadly. It was deadly game these guys played.

 

[pbehn]

Yup, both these types operated from the same captured airfields as the Spitfires. Why bother flying them from the UK when you can get better operational flexibility and faster response time over in the continent?

Without being too obvious, the P-47 and Typhoon made far better ground attack aircraft, but that shouldn't overshadow nor diminish the efforts of the Spitfire pilots that flew it in that role.

I was talking about this with a British friend of mine recently and I remarked that when I was in France a couple of years ago we visited a few cemeteries around the Normandy area and almost all of them have Typhoon pilots interred within. Loss rates were high, sadly. It was deadly game these guys played.

100 miles is a huge distance away from base for a pilot to know what he is supposed to be attacking. Once the Normandy beach head was established why would you need any more distance? It is 200 miles from Caen to Calais which is 21 miles from Dover. By the time you have got the information and briefed the pilots about what is where and what to attack then things have probably changed anyway. This is why the cab rank system was developed and that is to support things in visual range of those on the ground at the front.

 

[nuuumannn]

100 miles is a huge distance away from base for a pilot to know what he is supposed to be attacking. Once the Normandy beach head was established why would you need any more distance? It is 200 miles from Caen to Calais which is 21 miles from Dover. By the time you have got the information and briefed the pilots about what is where and what to attack then things have probably changed anyway. This is why the cab rank system was developed and that is to support things in visual range of those on the ground at the front.

Not sure what point you are making in relation to mine, exactly pbehn. Whatever it is I certainly don't disagree.

 

[Shortround6]

It seems like a lot of fighters, not just the Spitfire, often flew ground support missions with bomb-loads well under what they were rated to carry. P-47s flying with 2x500 lb bombs vst its rated load of 2500 lbs, for example. In WWII, P-51s would carry 2x500lbs, but In Korea, they would carry 2x1000. Was there a particular reason for this?

It could be several reasons, supply being one reason. Getting several hundred 500lb bombs to a forward air field is a lot easier that getting the same number of 1000lbs to the same air field, assuming you have the same number of 1000lbs in the first place.
You may also get faster turn around time with the lighter bombs?

Not all targets require 1000lb bombs and a 1000lb bomb does not have twice the blast radius of a 500lb bomb. Against certain types of targets the 1000lb bomb is better, against other types of targets it is just over kill.

 

[ThomasP]

re size of bombs used

Another factor is danger zone to the dropping aircraft, although I do not have any sources to hand that I can quote. I have read (in both official memos and squadron reports) that the 500 lb was often chosen in order to reduce the chance of damaging the dropping aircraft, while still being able to maintain accuracy by dropping at low(er) altitude. I do not know how often this was done, but I have also read that 500 lb bombs being used by Tac/CAS aircraft were sometimes reduced in HE content, in order to reduce the blast effects on the aircraft.

 

[Geoffrey Sinclair]

I would add bomb loads determined by fuel weight/bomb weight trade off and heavier aircraft have more difficulty evading and manoeuvering
9th Air Force Ordnance On target figures, P-47
Pounds Type Class No.
1000 GP HE 8987
1000 SAP HE 260
600 GP HE 14
500 GP HE 167,981
500 Comp B HE 4712
500 SAP HE 1840
300 GP HE 65
250 GP HE 2268
200 GP HE 73
100 GP HE 75
500 Frag 2624
400 Frag 128
360 Frag 46
280 Frag 20
265 Frag 77
260 Frag 24,467
250 Frag 89
120 Frag 4218
6 x 20 Frag 31
100 Frag 9205
90 Frag 704
80 Frag 8
60 Frag 54
20 Frag 11068
1100 FB Incen 1209
1000 FB Incen 24
750 FB Incen 510
500 FB Incen 4175
500 IC Incen 639
500 IB Incen 3724
500 WP Incen 121
300 WP Incen 62
300 FB Incen 31
280 FB Incen 141
125 WP Incen 20
100 WP Incen 1221
100 SM Incen 35
Rockets 13783
0.50 cal expended 55,487,266

P-38
Pounds Type Class P-38
2000 GP HE 57
1000 GP HE 13660
1000 SAP HE 1239
500 GP HE 10618
260 Frag 242
100 Frag 153
1100 FB Incen 1147
750 FB Incen 6
500 FB Incen 478
500 IB Incen 182
350 FB Incen 20
0.50 cal expended 3,225,426
20mm expended 497,730

 

[Reluctant Poster]

I really should do more reading before I answer... So going back to this, Yes, it does. Coningham did in fact have something to do with the LF.IX, albeit by proxy via the LF.V. Here's what Morgan and Shacklady has to say,

"The impetus given to large scale production [of the LF.IX, my addition] came from Air Marshal Coningham, C-in-C Air Forces in the Western Desert. He originally asked for 'massive' supplies of LF.VB/VCs as 80% of his operations were at low altitude."

"There was little point in building and shipping additional Mk.Vs to the Middle East as future Spitfire production was devoted to the Mk.IX, and the result was a low altitude variant to meet requirements."



Not entirely accurate apparently, see above in Mike Williams' post. The HF designation might have come around at a similar time as the LF designation though, but a year earlier, as per a report written at Boscombe Down dated 3 August 1943 titled "Spitfire HF.IX EN524". However, according to Morgan and Shacklady the first "LF.IX" was a converted Mk.VC MA648, which was fitted with a Merlin 66 on 23 May 1943 by Rolls-Royce, which contrasts with the ORB entry above...

A good idea often has several different origin myths. The one I was raised on is that a test of a captured FW190 vs an early Spitfire IX prompted the desire for improved lower altitude performance. I discount that one, as I don't think the time line fits with the actual Merlin 66 development time line. I also tend to discount the Coningham story for the same reason as I don't see any proper account of when he said it, to whom he said it and how it was conveyed to Rolls Royce. In fact, the following will show he would have had to make the request before he actually used the Spitfire in combat.

The origins of the Merlin 66 and 65 are discussed in "Rolls Royce and the Mustang" by David Birch. These versions of the Merlin were developed at the same time, the 65 for the Mustang and the 66 for the Spitfire. The main difference between them was the propeller reduction ratio (.477 for the 66, .42 for the 65).

Birch quotes a letter of June 24, 1942 from Lovsey to Bulman which discusses the subject of the improved supercharger being developed for the 2 stage Merlin and the plan to lower the supercharger gear ratios concurrently with the introduction of the new supercharger. Since the meeting it references took place on June 10 and since the first FW 190 to be tested by the allies was captured on June 23, the testing story can be discounted. The following quotes are from that letter:

"With reference to your telephone inquiry this morning , in conjunction with the revised supercharger ratios for the improved performance Merlin 61 blower the following points were discussed with DTD during his visit to Derby on June 10th​.

Modifications to the Merlin 61 blower by increasing the diameter of the first stage rotor and changes in the in the rotating guide vane and diffuser have resulted in increasing the full throttle height by approximately 2,000 ft., at the expense of a small reduction of the h. p. at the present all-out boost pressure of 15 lb./sq. in. This blower improvement could, therefore, be used for increasing aircraft performance above the full throttle heights, or by adjustment of the supercharger gear ratios could be used for obtaining a substantial improvement in performance below the full throttle heights, while maintaining the present standard Merlin 61 performance power at full throttle."

This clearly shows that Rolls Royce was thinking about reducing the gear ratios from the beginning. Note that the Spitfire IX with Merlin 61 first went into service around this time

At the time this was going on Rolls Royce was putting Merlins into Mustangs. They proposed using the improved supercharger and the same lower gear ratios for the Mustang.

The following are extracts from a letter to Ellor in Detroit dated, July 1942:

"Proposed Modifications to the Merlin 61 Supercharger and Bendix Carburettor

Since the Merlin 61 was put into production supercharger development has led to several modifications which have resulted in an improved performance.

It seems possible that these modifications might be standardised from the start in America and full details are therefore attached for vour information. Briefly the modifications consist of the adoption of thin vane diffusers in place of the existing wedge vane type, modified circular arc rotating guide vanes and an increase in the first stage rotor diameter from 11.5 ins. to 12.0 ins."

"As a further development of the improved supercharger a set of revised supercharger gears are now being made up (5.78 :1 and 7.06:1 instead of 6.39 and 8.03)."

"The intention is to improve the low altitude performance as much as possible."

The following is a quote from a letter from Lappin to Freeman dated 16th June 1942:

"I hope you were interested in the Mustang performance figures which I sent to your office last week. We have since made a further exploration into this and we think it is not unlikely that we can again improve the performance by improved blowers and reducing the supercharger ratio."

The following is a quote from a letter from Hives to Freeman dated 28th​ June 1942:

"The Spitfire 8 and 9 will make a big improvement and we are also developing another version of the '61', which will give its maximum performance at a lower altitude."

The reality that at high altitude a Spitfire with a Merlin 66 could out perform any aircraft it going to face in combat and by quite a margin.

Coningham didn't receive his first Spitfires until May 7 1942 and they didn't go into action until June 1 1942 (The Spitfire's first victory in the Middle East was June 8, 1942). Since Rolls Royce refers to lower gear ratios in the June 10th meeting, RR must have been working on the problem some time before Mk. Vs saw action in the Middle East, therefore Coningham he must have gotten his demands through to the D.T.D some time before he used a Spitfire in combat.

Incidentally all this occurred before anyone thought of cropping the impeller in a Merlin 45. The Merlin 66 predated the Merlin 45M.

Initially the Americans choose not to follow Rolls Royce's advice on lowering supercharger ratios with the V-1650- 3 which powered early P-51 Bs and Cs but eventually did so with the V-1650-7 which powered later Bs and Cs and all Ds. They did however adopt the improved supercharger which makes the V-1650-3 the equivalent of the Merlin 70, not the 63 as is commonly stated.

The evidence points to crediting Rolls Royce with the idea of improving the performance of the new Merlin at lower altitudes. This was a common theme for both the Spitfire and the Mustang. This should surprise no one as they were the ones who thought of putting 2 stage Merlins into the Spitfire and the Mustang in the first place. They knew more about aircraft performance than most organizations.

 

[SuperAereo]

"Spitfires Rampant" by Bill Tatham is a very good read on the exploits of 4 Sqn SAAF's dive bombing Spitfires in Italy, if you are after first-person impressions...