A Critical Analysis of the RAF Air Superiority Campaign in India, Burma and Malaya in 1941-45

[Schweik]

Commonwealth trials of the P40 variants don't show such optimistic speeds for the P-40E. Most of the really impressive results seem to have come from Curtiss directly.

The Hurricane is lighter than the P-40 and has lower wing loading. Why would you expect the P-40 to be able to climb as well, especially with the early model Allison engines?

First - I wouldn't normally expect the P-40 to outclimb the Hurricane to be honest, since they didn't climb that well, but the boost / WEP numbers look like maybe they could sometimes probably depending on the load. And there is also the overheating problems apparently faced by Hurricanes to consider. I wouldn't put money on it though.

If you noticed, rather similar to your comments about +9 vs +16 boost, it was discovered in the first few months of 1942 that P-40Es could be safely run at 57" vs. 45" Hg, which translates to 1470 hp vs. 1150. Which is a big difference at least at low altitude.

Second, the Hurricane, again relying mainly on anecdotal evidence from a lot of commentary, was much draggier, it had a 40' wingspan vs 37' on the P-40 or 36' on the Sptfire, and it had notoriously thick wings. I think that may have been one of the main issues with it. The fuselage, though streamlined, was also I think high, giving it that humpback appearance. This too induces drag, I know for example the bubble canopy P-51D was slower than the 'tighter' P-51B. The P-40 was draggy too with the big chin radiator scoop, but apparently not the same extent.

I assume this is why the top speed of the P-40 is always listed as higher than the Hurricane, except in that one test you posted.

The P-40 pulling maximum boost via WEP is just about even with a Hurricane II using normal climb power, but what do you think would happen when the Hurricane II pilot pulls the plug and uses WEP as well?

I'm not sure what the power ratings were on the tests posted so far actually, but if you find any of them being tested at WEP please post them. For some reason as noted upthread though most official tests (for any of these aircraft) seem to be done at normal rated or military power, only later in the war does WEP seem to garner much Official attention.

The P-40 supplemented the Hurricane in the ETO/MTO, it didn't replace it.

P-40s were not used in the ETO except for early Tomahawks in the "Army coopration" role similar to the Allison engined Mustangs.

In the MTO P-40s most definitely did replace Hurricanes in the main Air Superiority Fighter squadrons. These were also by far the highest-scoring fighter squadrons in the Med until the Spitfires arrived in later 1942. 112 Sqn RAF, No 3 Sqn RAAF, No 250 Sqn RAF, No 260 Sqn RAF, and No 450 Sqn RAAF had all of their Hurricanes replaced by P-40s in 1941 or early 1942. Later more fighter wings converted throughout 1942, but the units which were still flying Hurricanes were flying almost exclusively bombing / strafing missions. And usually being escorted by P-40s.

112 RAF

• 1939–1941 – Gloster Gladiator I & II
• 1940-1940 – Gloster Gauntlet
• 1941 – Hawker Hurricane I
• 1941 – Curtiss Tomahawk I
• 1941 – Curtiss Tomahawk IIA & IIB
• 1941–1942 Curtiss Kittyhawk 1A
• 1942–1944 Curtiss Kittyhawk III
• 1944 Curtiss Kittyhawk IV
• 1944–1945 North American Mustang III

260 RAF is also fairly typical:

Nov 1940 Feb 1942 Hawker Hurricane I
Feb 1942 Mar 1942 Curtiss P-40 Tomahawk II
Feb 1942 Sep 1942 Curtiss P-40 Kittyhawk I
Jun 1942 May 1943 Curtiss P-40 Kittyhawk IIA
Dec 1942 Mar 1944 Curtiss P-40 Kittyhawk III
Apr 1944 Aug 1945 North American P-51 Mustang III
Jun 1945 Aug 1945 North American P-51 Mustang IV

And etc.

The Spitfire VC Trop was still ~30mph faster than a Hurricane II. But it is good question as to why Australia didn't get Hurricanes; Hurricane development as an air superiority fighter ended in early 1941, which probably was a factor and the RAAF wanted the best available high altitude fighter. However, there's no doubt that the Hurricane II could have done a credible job in lieu of the Spitfire Vc trop/Merlin46 and perhaps done better if it didn't suffer the same issues with the CS prop unit and cannon jams. It would have had a lot more trouble catching high altitude IJ recon aircraft though.

Interesting theory, I wonder if we can find any Australian or RAF documents related to why they made the choices they did.

S

 

[Schweik]

By the way - all this stuff about the Hurricane is interesting. It seems like you are reaching a little but if even half of your claims are true, you should update the Wikipedia page on it.

If the Hurricane can really roll fast and dive fast it certainly changes my impression of the plane. And poses a lot of new questions.

 

[Shortround6]

The British have operated at full throttle at sea level (72" Hg) for as much as 20 min. at a time without hurting the engines. According to them, the Allison is averaging 1500 hours between bearing failures as compared to 500 to 600 hours for the Merlin. And this is presumably the earlier and not as robust V-1710-39.

I think we have a problem here in equating bearing failure to engine life or time between overhauls. I don't believe anybody was operating either the Merlin or the Allison for 1500 hours without a tear down (or 3-5 teardowns). Now during a teardown or overhaul if the bearings were still in spec they went back in the engine (if they even came out?)
And a worn bearing is not a bearing failure.
Near the end of the war the Allison was exceeding 1000 hours between overhauls in P-40s used by training commands in the US (which usually operated on much lower boost limits than standard military power). Which makes the 1500 hour figure a bit dubious when trying to apply it to combat aircraft as actual engine life.
Tear downs/overhauls also covered wear to pistons and piston rings (or damage from detonation, pitting or rough surface of piston top) valve pitting/burning, valve guide wear, valve seats, broken or soft valve springs and a host of other fit/tolerance areas.
RR was recommending in 1939 that Merlins used in fighters should be pulled for overhaul after 240 hours, this rose to 300 hours by 1944.
Bomber engines lasted a bit longer.

Engine life figures also need close scrutiny as RR reported that only 35% of engines going through the repair facilities had reached their recommended service life and of the engines going through the repair facilities the engines averaged 60% of the recommended engine life.
Now please, please note that these figures include engines going through the repair facility for ALL reasons. like combat damage ( a few bullet holes in the cooling jacket?) or a prop strike (aircraft noses over with prop turning or belly lands.) In fact RR worked out a way to weld the aluminium nose gear case and add an external brace to return engines that suffered a cracked nose gear case in a prop strike to service, without requiring new castings/housings.

Also please note that Allison developed both stronger valve springs and different top piston rings for the later 2 stage engines when they expected to be running high intake manifold pressures for long periods of time.

 

[pinsog]

Glad to see you Shortround. Your technical knowledge is always enlightening

 

[pinsog]

Could someone explain how a Hurricane could beat a Hamp 1 on 1 when a Spitfire V "was totally outclassed at all altitudes below 20,000" and Spit V had no outstanding features allowing it to successfully take on a Hamp when starting on equal footing.

A Hurricane is 20 or 30 mph slower than a Spit V, climbs slower, I would think it dives slower. It does turn tighter but that won't work against a Zero or Hap.

So what can it do starting on equal footing against a Zero or Hap?

 

[Greyman]

I disagree with 'totally outclassed at all altitudes below 20,000 feet'. Totally outclassed in a 1-versus-1, slow-speed dogfight, perhaps.

The Hurricane has better roll and dive acceleration than the Zero - ie: the attributes that the Wildcat has over the Zero - the Hurricane is even better (save for resistance to enemy fire).

So if you can believe that the Wildcat was able to best the Zero on occasion, it shouldn't be a stretch that the Hurricane could do the same.

EDIT: reading around a bit it seems that the Wildcat's dive was about the same as the Zero.

 

[RCAFson]

The P-40 seems to do well on some tests but not others. I think most of us agree that the F4F-4 had a poor RoC:

So what happens when the USN tests the same aircraft, above, against a P-40F?:

http://www.wwiiaircraftperformance.org/f4f/f4f-4-02135.pdf

Hmm...

 

[RCAFson]

Could someone explain how a Hurricane could beat a Hamp 1 on 1 when a Spitfire V "was totally outclassed at all altitudes below 20,000" and Spit V had no outstanding features allowing it to successfully take on a Hamp when starting on equal footing.

A Hurricane is 20 or 30 mph slower than a Spit V, climbs slower, I would think it dives slower. It does turn tighter but that won't work against a Zero or Hap.

So what can it do starting on equal footing against a Zero or Hap?

I showed rather conclusively during that the Spitfire V/A6M3 trials that the Spitfire was denied 16lb boost. If both aircraft use their maximum engine ratings the Spitfire will have better climb at all altitudes and be ~20-30mph faster at all altitudes. The RAAF HaP trials showed a rough equivalency to a Hurricane II in performance.
Another viewpoint on Spitfire vs Hap:
http://www.wwiiaircraftperformance.org/japan/spit-v-zero-wawn.jpg

Caldwell on Spitfire vs Zero:
http://www.wwiiaircraftperformance.org/japan/spitfire-v-zero-caldwell.jpg

 

[pinsog]

I agree 100% that the F4F-4 climb rate was awful. It's stats do not explain its 1-1 kill ratio against the Zero.

In another thread in this forum, JoeB stated and provided evidence that the Spitfire kill ratio against the Zero over Darwin was 28 Spitfires shot down (this doesn't include those that ran out of fuel, I believe they had 8 or 10 Spitfires run out of fuel on 1 intercept over Darwin) vs 4 Zero's confirmed destroyed. I can't remember how many bombers were destroyed.

RCAFson Both of those articles you produce are postwar magazine articles from the winners. (Loops aren't used in combat??? One of the Zeros favorite tricks was to simply loop up and over and drop down on the tail of the allied fighter. The Hap flies 500 miles 1 way, shoots down Spits at a 7-1 ratio and runs a bunch more out of fuel but the Spitfire and her pilots were better? Post war BS) Actual tests, during the war, by combat pilots in theater said the Spitfire was no match under 20,000 feet if started on equal terms. Of course they could shoot them down if they bounced them from 5,000 feet above.

The actual test showed the Spit V speed wasn't enough to evade a Hap. Same test said the Spit V could not dive away fast enough to avoid getting shot down, it just slowly pulled away.

Can a Hurricane out dive a Spit V? Can someone answer this? I wouldn't think so but I learn on here every day.

Shortround6 gave a very detailed answer on the 16 lb boost rating. For whatever reason the Darwin Spit V did not have the high boost rating. Maybe if it had it it might have done better, but it didn't have it and was deemed 'completely outclassed below 20,000 feet'.

 

[pinsog]

The Hurricane has better roll and dive acceleration than the Zero - ie: the attributes that the Wildcat has over the Zero - the Hurricane is even better (save for resistance to enemy fire).

Agree 100% the high speed Hurricane roll was better than a Zero, F4F-4 and Spitfire V.

Agree F4F-4 dived at same speed as Zero.

Spitfire dive wasn't fast enough to evade a following Zero, I doubt a Hurricane would dive faster than a SpitV. Maybe a Hurricane would be better at evading than a SpitV if it did a diving roll. But at the end of that roll, your in a slower aircraft with a slower climb and if you drop below 275 mph or so your going to be less maneuverable as well. A P40 could roll, dive and run like mad. An F4F-4 could take a lot of damage (radial engine)

 

[RCAFson]

I agree 100% that the F4F-4 climb rate was awful. It's stats do not explain its 1-1 kill ratio against the Zero.

In another thread in this forum, JoeB stated and provided evidence that the Spitfire kill ratio against the Zero over Darwin was 28 Spitfires shot down (this doesn't include those that ran out of fuel, I believe they had 8 or 10 Spitfires run out of fuel on 1 intercept over Darwin) vs 4 Zero's confirmed destroyed. I can't remember how many bombers were destroyed.

RCAFson Both of those articles you produce are postwar magazine articles from the winners. (Loops aren't used in combat??? One of the Zeros favorite tricks was to simply loop up and over and drop down on the tail of the allied fighter. The Hap flies 500 miles 1 way, shoots down Spits at a 7-1 ratio and runs a bunch more out of fuel but the Spitfire and her pilots were better? Post war BS) Actual tests, during the war, by combat pilots in theater said the Spitfire was no match under 20,000 feet if started on equal terms. Of course they could shoot them down if they bounced them from 5,000 feet above.

The actual test showed the Spit V speed wasn't enough to evade a Hap. Same test said the Spit V could not dive away fast enough to avoid getting shot down, it just slowly pulled away.

Can a Hurricane out dive a Spit V? Can someone answer this? I wouldn't think so but I learn on here every day.

Shortround6 gave a very detailed answer on the 16 lb boost rating. For whatever reason the Darwin Spit V did not have the high boost rating. Maybe if it had it it might have done better, but it didn't have it and was deemed 'completely outclassed below 20,000 feet'.

There are extensive threads devoted to the Darwin Spitfire debacle. However, of the Spitfire air combat losses, how many had actually run of fuel? How many had suffered CS prop failures and how many suffered high altitude cannon jams, resulting in the Zero being able to turn the tables? The other factor is that the Spitfire's mission was to destroy the bombers and IJ recon aircraft. When these are added in the kill ratio is about 1-1.

You keep repeating the "outclassed claim" even when several of us have pointed out that this pertains to close in dog fighting. Anyways here's another view on being outclassed:
"(c)Material (planes): The disastrous loss of our TBD's needs no further comment; it is earnestly hoped that steps will be taken to provide TBF's for all carrier Air Groups immediately. The SBD is now obsolescent due to its slow speed. Our fighters, F4F-4's, are completely outclassed by Japanese "0" fighters in speed, climb, and maneuverability. It is recommended that immediate action be taken to remedy this inferiority."
Action Report: 4-6 June 1942 (Serial 0137)

And the above pertains to all aspects of performance, yet the F4F-4 fought the Zero to a draw.

 

[Greyman]

Spitfire dive wasn't fast enough to evade a following Zero.

When the Spitfire apparently was not using full boost, correct.

 

[pinsog]

When the Spitfire apparently was not using full boost, correct.

Apparently, according to Shortround, it wasn't available (i read his response last night) If it was, wouldn't the report read 'outclassed unless using emergency boost' or something?

 

[Greyman]

Do you have the actual report? There may be important entries/footnotes we're missing.

+16 boost seems to have been available in August 1942.

 

[pinsog]

There are extensive threads devoted to the Darwin Spitfire debacle. However, of the Spitfire air combat losses, how many had actually run of fuel? How many had suffered CS prop failures and how many suffered high altitude cannon jams, resulting in the Zero being able to turn the tables? The other factor is that the Spitfire's mission was to destroy the bombers and IJ recon aircraft. When these are added in the kill ratio is about 1-1.

You keep repeating the "outclassed claim" even when several of us have pointed out that this pertains to close in dog fighting. Anyways here's another view on being outclassed:
"(c)Material (planes): The disastrous loss of our TBD's needs no further comment; it is earnestly hoped that steps will be taken to provide TBF's for all carrier Air Groups immediately. The SBD is now obsolescent due to its slow speed. Our fighters, F4F-4's, are completely outclassed by Japanese "0" fighters in speed, climb, and maneuverability. It is recommended that immediate action be taken to remedy this inferiority."
Action Report: 4-6 June 1942 (Serial 0137)

And the above pertains to all aspects of performance, yet the F4F-4 fought the Zero to a draw.

Agree the Wildcat was outclassed in speed, climb and maneuverability, no question. But the Wildcat still fought 1 to 1 in worse conditions than Darwin (Guadalcanal).

Apparently the Japanese pilots didn't chose to fight the Spitfire on the Spitfires terms. Sounds like "little yum yum" as Caldwell called him, knew a bit more about flying than Caldwell wants to admit.

JoeB said (I'll find that thread) that 28 Spits were shot down. They know who ran out of fuel because when they got back to base they said "I ran out of fuel". Engine failure and prop issues were in another column. Yes, the 20mm guns didn't work either (Caldwell apparently said they should have had 4 50's). Several F4F-4's were lost to prop failure in The First Team.

On the other hand, the Zero's were flying in the same conditions as the Spitfires but their stuff seemed to work. If your engines blow up, your props don't work, your guns won't fire and your run out of fuel over your own airfield by a guy who just flew 500 miles one way isn't exactly a great argument for the Spitfire being the better plane

 

[pinsog]

Do you have the actual report? There may be important entries/footnotes we're missing.

+16 boost seems to have been available in August 1942.

http://www.darwinspitfires.com/index.php?page=spitfire-vc-versus-the-zero

 

[RCAFson]

Agree the Wildcat was outclassed in speed, climb and maneuverability, no question. But the Wildcat still fought 1 to 1 in worse conditions than Darwin (Guadalcanal).

Apparently the Japanese pilots didn't chose to fight the Spitfire on the Spitfires terms. Sounds like "little yum yum" as Caldwell called him, knew a bit more about flying than Caldwell wants to admit.

JoeB said (I'll find that thread) that 28 Spits were shot down. They know who ran out of fuel because when they got back to base they said "I ran out of fuel". Engine failure and prop issues were in another column. Yes, the 20mm guns didn't work either (Caldwell apparently said they should have had 4 50's). Several F4F-4's were lost to prop failure in The First Team.

On the other hand, the Zero's were flying in the same conditions as the Spitfires but their stuff seemed to work. If your engines blow up, your props don't work, your guns won't fire and your run out of fuel over your own airfield by a guy who just flew 500 miles one way isn't exactly a great argument for the Spitfire being the better plane

The IJN/IJA revised their tactics after 1942 and in 1943 and in the main, only used high altitude bombing against Darwin, thus forcing the Spitfires high enough to cause the trilogy of fuel, prop and cannon failure. Many of the high altitude raids over Port Moresby and Guadalcanal were not intercepted due to theP-40/P39/F4F's poor climb rate. Over Darwin in 1942 the P-40s still had problems but typically had enough radar warning to climb above the Medium altitude bombing raids, but they typically couldn't intercept recon flights.

But of the 28 that were stated as shot down, there's no way to know how many had suffered from in-flight failures enumerated above, which in turn, contributed to their loss.

Again, we have to look at all kills not just fighter versus fighter, and then the kill ratio was about 1-1.

The IJN/IJA fighters were based much closer to Darwin than to Guadalcanal. IJN fighters over Guadalcanal were at the extreme end of their range and most had to retain their their DTs, for example [See First Team V2 for details], whereas over Darwin they released them. Additionally the IJN employed A6M3s and Ki-43IIs on some of their raids. The A6M3, as we've discussed has considerably superior performance compared to the A6M2, especially it's roll rate due to the clipped wings and superior HV 20mm cannons. The A6M3 didn't have the range to make it to Guadalcanal and didn't participate there.

 

[Greyman]

Made a quick chart to visualize things.

EDIT: I edited the chart to show the RAAF tropical Merlin 46 data from
http://www.darwinspitfires.com/index.php?page=performance-of-spitfire-vc-tropicalised-version-2

The thin, dotted portion of the +16 boost line is my vague estimate.

 

[RCAFson]

http://www.darwinspitfires.com/index.php?page=spitfire-vc-versus-the-zero

From the above:
"The Zero developed its maximum speed of 291 knots at its rated altitude of 16 000 feet. The Spitfire produced 290 knots at 15 000 feet, confirming that below 20 000 feet the two types were more evenly matched in speed performance..."

Maximum speed of the RAAF Spitfire at 15000ft, using 16lb boost was ~310 knots. The above quote confirms that 16lb boost was not used in the comparative test.

The Merlin 45/46 used a single speed SC. It was imperative to use overboost when fighting below the rated altitude of the engine to gain maximum performance, and the effect of overboost was to create a near constant maximum speed from 10k ft all the way to the rated altitude:
"RAAF Spitfire V/Merlin 46 speed tests:
(1) AT SEA LEVEL (A) 312 (B) 318 (C) 316.

(2) AT10,000 FEET (A) 355.5 (B) 355. 6 (C) 360 MPH.

AT FULL THROTTLE HEIGHT (A) 357 (B) 358.5 (C) 363 MPH.

A = trop cowl, B= modded trop cowl with filter bypass, and C = temperate cowl."

 

[Kevin J]

By the way - all this stuff about the Hurricane is interesting. It seems like you are reaching a little but if even half of your claims are true, you should update the Wikipedia page on it.

If the Hurricane can really roll fast and dive fast it certainly changes my impression of the plane. And poses a lot of new questions.

The roll rate of the Hurricane I was better than the IIb/c because it had less weight in the wings. The IIb especially had a weight distribution which adversely affected roll rate. The Soviets solved these problems by replacing the armament with a pair of 20 mm cannon and another pair of 0.5 in guns.