MOST OVERRATED AIRCRAFT OF WWII

stona · Apr 19, 2016

If you read the contemporary reports from the fighting over NW Australia it becomes evident that the RAAF was well aware of the problems with both its pilots and tactics. The 'Capstan'/Spitfire was not considered the main problem, despite some well known technical problems.

This report summarises the reason for the loss of seven Spitfires quite bluntly.

This is just the end of a report listing a catalogue of errors and failings in the interception of one of the raids. Again, nothing to do with the aircraft apart from that last entry. No service likes to see phrases like 'lack of leadership' in any type of after action report.

And finally what the men who were actually flying the Spitfires, rather than we sitting in our armchairs 70+ years later, thought about the two protagonists.

Thanks to, I think, Aozora for the reports. Apologies if it was someone else.

Cheers

Steve

pinsog · Apr 19, 2016

GrauGeist said:
In the early months of the war, the SBD doubled as top cover for the fleet and proved itself effective for the task

Yes. The SBD was used at low level for anti-torpedo bomber patrol. I was amazed, after reading The First Team, at just how aggressive the SBD pilots were. It seemed like those guy weren't afraid of anything. The seemed to have absolutely no fear whatsoever of Kates and Vals. If they saw a Kate or a Val they would attack immediately. Happened several times during the Guadalcanal campaign when opposing strikes passed each other going home after the attack. There were at least a couple of times where an SBD pilot would see a Zero and if the Zero didn't see him, the SBD pilot would dive on the Zero! I thought that seemed like the mouse going after the cat!

tomo pauk · Apr 19, 2016

Thank you, Steve.

Shortround6 · Apr 19, 2016

The Spitfires over Darwin would only be able to outclimb F4F-4s by 2000fpm if they used JATO rockets.

Granted test results are a bit confusing but the Darwin Spitfires are rated at about 2480fpm at sea level using 2850rpm and 9lbs boost.
using 3000rpm and 9lbs boost may get you a bit more in pinch but is not to be used for climbing to operational height. Climb at 20,000ft was 2250fpm (2850rpm and 7 1/2lbs boost) and at 25,000ft it was 1600fpm at 2850rpm and 3 1/2lbs.

The F4F-4 was good (in clean condition) for a bit over 2000fpm up to around 11-12,000ft after which it dropped off, around 1200fpm at 20,000ft and 750-800fpm at 25,000ft.
Wildcats were not allowed to use "Military" power in high supercharger. While 2700rpm was allowed for take-off and low altitude work once the aux supercharger was in high gear the engine was restricted to 2550rpm although they were permitted to run at that rpm and what ever boost they could get for as long as they wanted subject to fuel and temperature limits. Wither pilots in combat obeyed that limit or not I don't know.
Also be aware when comparing test results that American tests for time to altitude are usually done at Military power for the first 5 minutes and at normal power (max continuous) for the rest of the climb so they are bit below what the plane could do in combat. For the F4F-4 this means at middle altitudes it could do a bit better than the time to altitude would suggest.

Yes the Spits could climb much better but not by 2000fpm and not any better than the Zeros.

There is a Navy test showing the F4F-4 still climbing at 1500fpm at 16,000ft. the difference in speed at rated altitude between 2550rpm and 2700rpm was 2.5 knots which may explain why the Navy didn't allow or bother with it.

stona · Apr 19, 2016

It is too the Australians' credit that they did try to build locally and improved air intake to replace the Vokes filters with which their aircraft were fitted. No.1 A.D. Laverton built a cowl described as 'approximately' like those used on temperate Spitfires in England. Despite initial enthusiasm, these efforts did not result in a significant improvement in performance. Nothing is as easy in practice as in theory when making alterations to carefully designed parts of a high performance fighter.
The Australians noted.
"Air intakes for modern high speed aircraft require careful design and attention to detail. It is apparent that the stub intake that has been used in this case has created very unsteady airflow conditions - upsetting mixtures and boost settings and thus creating engine roughness and loss of power."
This also means that the technicians at 103 MU at Aboukir either understood the issues better or just got lucky when they designed their improvement to the Vokes filter.
Eventually the Australians sent to England for drawings of the standard air intake and cowl.
They also tried to improve performance by polishing their aircraft. In one signal the sender bemoans the fact that no proper polishes or compounds are available locally. I think it easy to forget just how far from help and support the Spitfires were operating. Another signal is an urgent request for fasteners, as again, none were available in Australia. They would either have to be fabricated locally or sent from the UK.
Australia in 1942 was not the same as Australia in 2016. I'm certain such things could be easily and quickly fabricated today.
Cheers
Steve

pinsog · Apr 19, 2016

Shortround6 said:
The Spitfires over Darwin would only be able to outclimb F4F-4s by 2000fpm if they used JATO rockets.

Granted test results are a bit confusing but the Darwin Spitfires are rated at about 2480fpm at sea level using 2850rpm and 9lbs boost.
using 3000rpm and 9lbs boost may get you a bit more in pinch but is not to be used for climbing to operational height. Climb at 20,000ft was 2250fpm (2850rpm and 7 1/2lbs boost) and at 25,000ft it was 1600fpm at 2850rpm and 3 1/2lbs.

The F4F-4 was good (in clean condition) for a bit over 2000fpm up to around 11-12,000ft after which it dropped off, around 1200fpm at 20,000ft and 750-800fpm at 25,000ft.
Wildcats were not allowed to use "Military" power in high supercharger. While 2700rpm was allowed for take-off and low altitude work once the aux supercharger was in high gear the engine was restricted to 2550rpm although they were permitted to run at that rpm and what ever boost they could get for as long as they wanted subject to fuel and temperature limits. Wither pilots in combat obeyed that limit or not I don't know.
Also be aware when comparing test results that American tests for time to altitude are usually done at Military power for the first 5 minutes and at normal power (max continuous) for the rest of the climb so they are bit below what the plane could do in combat. For the F4F-4 this means at middle altitudes it could do a bit better than the time to altitude would suggest.

Yes the Spits could climb much better but not by 2000fpm and not any better than the Zeros.

There is a Navy test showing the F4F-4 still climbing at 1500fpm at 16,000ft. the difference in speed at rated altitude between 2550rpm and 2700rpm was 2.5 knots which may explain why the Navy didn't allow or bother with it.

More like 1,700 - 1,900 for the F4F-4. Spitfire beats it by 1,300-1,500 fpm but the Spitfire test is from June, 1941. Not sure how much effect the tropical filter had on climb, but I'm sure it was substantial

F4F Performance Trials

F4F-4 October 21, 1942 fighter bomber fighter overload

Initial rate of climb at sea level (ft./min.) 1920 1810 1690
Time to climb to 10000 ft. (min.) 5.7 6.0 6.5
Time to climb to 20000 ft. (min.) 12.7 13.1 14.7

Spitfire Mk V Performance Testing

Aeroplane and Armament Experimental Establishment
Boscombe Down
18 June 1941

Spitfire Mk. VB W.3134
(Merlin 45)
Brief Performance Trials

SUMMARY

.......Brief performance trials were required of a Spitfire Mk VB fully operationally equipped for comparison with two other aircraft of the type not operationally equipped and previously tested at this establishment.

top Speed M.P.H Time to Climb mins. Rate of climb

S.L. . 0 .
2,000 . 0.6 3240
5,000 . 1.5 3240
10,000 331 3.1 3250
15,000 351 4.6 3250
20,000 371 6.4 2440
25,000 359 . .
30,000 . 12.2 1170

Shortround6 · Apr 19, 2016

pinsog said:
More like 1,700 - 1,900 for the F4F-4. Spitfire beats it by 1,300-1,500 fpm but the Spitfire test is from June, 1941. Not sure how much effect the tropical filter had on climb, but I'm sure it was substantial

F4F Performance Trials

F4F-4 October 21, 1942 fighter bomber fighter overload

Initial rate of climb at sea level (ft./min.) 1920 1810 1690
Time to climb to 10000 ft. (min.) 5.7 6.0 6.5
Time to climb to 20000 ft. (min.) 12.7 13.1 14.7

Spitfire Mk. VB W.3134
(Merlin 45)
Brief Performance Trials

What you have is the "projected" or estimated performance figures for the F4F-4

a later chart is as follows: http://www.wwiiaircraftperformance.org/f4f/f4f-4.pdf

The Navy sometimes differed from the army (especially early war) in giving performance figures for normal power instead of military power. Please note that Military power is pretty much only available below 14-15,000ft in these charts.

You also have the wrong Spitfire chart as in the wrong engine. The MK Vs in Australia had Merlin 46 engines which used a 10.85 in dia impeller instead of the 10.25in impeller used in the Merlin 45. It allowed more power at higher altitudes (1100hp at 22,000ft at 9lbs boost) but cost 85hp at take-off at 3000rpm and 12lbs boost and cost roughly 85-100hp at the lower altitudes until the high teens or low 20s were reached.

Once again, please see: http://www.darwinspitfires.com/index.php?page=performance-of-spitfire-vc-tropicalised-version-2

stona · Apr 19, 2016

"Not sure how much effect the tropical filter had on climb, but I'm sure it was substantial"

It depends what you call substantial. The Australians asked for the figures when they were assessing their new home built cowlings and received a signal with figures for the Spitfire VC with Merlin 45.
This was because "reliable performance figures for the tropicalised VC with Merlin 46 are not available." The Australian request could "best be satisfied by quoting figures for tropical and non tropical versions of the VC with Merlin 45."
Time to 20.000 feet increased from 7 minutes to 7.4 minutes with the Vokes filter fitted. I'm not sure that 24 seconds is that substantial, it represents about a 6% drop in performance from the standard time. The tropicalised Spitfire also weighed about 150lb more.
Cruise speed at 20,000ft was just 10 mph less (322mph and 312mph).
Maximum speeds were 369 mph at 19,500 feet for temperate and 352 mph at 18,500 feet for tropicalised Spitfires. This is actually remarkably close to the 15 mph often quoted.

This data was sent on 14th January 1943, in the signal covering the Supermarine drawings for the temperate cowl which the Australians had requested.

Not all aircraft are created equal. In other trials the time to 30,000ft measured by the Australians varied considerably for different aircraft tested. The average time was 17 minutes with a Vokes filter, worse by about 1 minute to the average time with a temperate cowl, but some aircraft were faster with the Vokes filter than others without. This is why it is so dangerous to quote test data for service aircraft.

Cheers

Steve

Shortround6 · Apr 19, 2016

The last part is also why operational ceiling for even small formation is 3-5,000 ft below the "service ceiling" and effective combat ceiling is even lower.
Australians started the program to remove the Vokes filter before they had done testing based on rumors that it cost 20mph in speed. Actual tests showed the difference was somewhat less.

stona · Apr 19, 2016

Shortround6 said:
Australians started the program to remove the Vokes filter before they had done testing based on rumors that it cost 20mph in speed. Actual tests showed the difference was somewhat less.

At least 20 mph. On 11th December 1942 a Wing Commander Hey (whose exact role I don't know, he signs as 'TSI') wrote.

"The main reason for the suggested removal of the air cleaner from the Capstan aeroplane is the assumed reduction in speed when compared with the original installation. Therefore, a great deal depends on whether or not the reduction of speed of 20 to 30 mph is correct...."

Capstan was the code name for the Spitfire.

The British had assured the Australians that the reduction in speed caused by the fitting of all items to tropicalise a VC was "to reduce the speed at 370 mph by only 2 per cent., which is 8 mph."

The truth lay between the two figures. Those provided later by the British, which I posted above, would be more accurate, around 15-20 mph. The reduction in performance was less than the Australians feared and, in any case, they struggled to manufacture a better or even workable replacement intake, filter and cowling assembly locally.

Cheers

Steve

stona · Apr 19, 2016

The developments and timeline in the Darwin Spitfire link above tally very well, give or take minor differences in the figures from different sources, with that I have pieced together.

RCAFson · Apr 22, 2016

Shortround6 said:
The Spitfires over Darwin would only be able to outclimb F4F-4s by 2000fpm if they used JATO rockets.

Granted test results are a bit confusing but the Darwin Spitfires are rated at about 2480fpm at sea level using 2850rpm and 9lbs boost.
using 3000rpm and 9lbs boost may get you a bit more in pinch but is not to be used for climbing to operational height. Climb at 20,000ft was 2250fpm (2850rpm and 7 1/2lbs boost) and at 25,000ft it was 1600fpm at 2850rpm and 3 1/2lbs.

The F4F-4 was good (in clean condition) for a bit over 2000fpm up to around 11-12,000ft after which it dropped off, around 1200fpm at 20,000ft and 750-800fpm at 25,000ft.
Wildcats were not allowed to use "Military" power in high supercharger. While 2700rpm was allowed for take-off and low altitude work once the aux supercharger was in high gear the engine was restricted to 2550rpm although they were permitted to run at that rpm and what ever boost they could get for as long as they wanted subject to fuel and temperature limits. Wither pilots in combat obeyed that limit or not I don't know.
Also be aware when comparing test results that American tests for time to altitude are usually done at Military power for the first 5 minutes and at normal power (max continuous) for the rest of the climb so they are bit below what the plane could do in combat. For the F4F-4 this means at middle altitudes it could do a bit better than the time to altitude would suggest.

Yes the Spits could climb much better but not by 2000fpm and not any better than the Zeros.

There is a Navy test showing the F4F-4 still climbing at 1500fpm at 16,000ft. the difference in speed at rated altitude between 2550rpm and 2700rpm was 2.5 knots which may explain why the Navy didn't allow or bother with it.

This test shows the climb rate at full military power (F4F-4 has no combat engine rating):

This test shows a Spitfire Vc climbing using the combat rating and normal ratings:

OTOH, the Capstan Spitfire V used the Merlin 46 which gave less power at low altitude but more at high altitude.

Shortround6 · Apr 22, 2016

RCAFson said:
This test shows the climb rate at full military power (F4F-4 has no combat engine rating):

This test shows a Spitfire Vc climbing using the combat rating and normal ratings:

OTOH, the Capstan Spitfire V used the Merlin 46 which gave less power at low altitude but more at high altitude.

And that last is the problem. The Merlin 46 was being limited to 9lbs boost at the time in Australia (from the tests in Australia?) . Please note that even using the Merlin 45 dropping from 16lbs boost to 9lbs boost in the chart you provided drops the rate of climb from around 3700fpm down to around 26-2700fpm.
There is no question the Spitfire could out climb the Wildcat, just not by 2000fpm for the version of Spitfire in question.

RCAFson · Apr 22, 2016

Shortround6 said:
And that last is the problem. The Merlin 46 was being limited to 9lbs boost at the time in Australia (from the tests in Australia?) . Please note that even using the Merlin 45 dropping from 16lbs boost to 9lbs boost in the chart you provided drops the rate of climb from around 3700fpm down to around 26-2700fpm.
There is no question the Spitfire could out climb the Wildcat, just not by 2000fpm for the version of Spitfire in question.

All versions of the Merlin 45/46 were limited to 9lb/2850rpm boost except when using the (post Jan 1942:
http://www.wwiiaircraftperformance.org/merlin-ratings_3jan42.jpg ) 16lb/3000rpm combat rating of the engine, which could always be used at the pilot's discretion. When the F4F-4 used Military Power and the Spitfire used Combat Power the Spitfire V would have a ~2000fpm advantage up to about 9000ft and a ~1500fpm advantage to about 18k ft.

Shortround6 · Apr 22, 2016

Once again, please see the chart at: http://www.darwinspitfires.com/index.php?page=performance-of-spitfire-vc-tropicalised-version-2

see 3rd chart on page, no mention of boost over 9lbs. I have no idea why.

Part of the problem over Darwin was climbing to the altitude the Japanese were coming in at with the amount of warning time they had.
Thrashing the engine with over 9lbs of boost before you are anywhere near (thousands of feet below and dozen or more miles away) the enemy is only going to make for more breakdowns and overheated engines, There may not have been a strict 5 minute rule but using over 9lbs boost and over 2850rom climbing to operational altitude and then continuing those power levels for the ensuing combat is going to be mighty hard on the engines. Especially considering that Australian temperatures are a lot warmer near ground level than British temperatures.

RCAFson · Apr 22, 2016

Shortround6 said:
Once again, please see the chart at: http://www.darwinspitfires.com/index.php?page=performance-of-spitfire-vc-tropicalised-version-2

see 3rd chart on page, no mention of boost over 9lbs. I have no idea why.

Part of the problem over Darwin was climbing to the altitude the Japanese were coming in at with the amount of warning time they had.
Thrashing the engine with over 9lbs of boost before you are anywhere near (thousands of feet below and dozen or more miles away) the enemy is only going to make for more breakdowns and overheated engines, There may not have been a strict 5 minute rule but using over 9lbs boost and over 2850rom climbing to operational altitude and then continuing those power levels for the ensuing combat is going to be mighty hard on the engines. Especially considering that Australian temperatures are a lot warmer near ground level than British temperatures.

Combat boost is usually listed in a separate entry in the Pilot's notes and it was unusual for the RAF to perform testing at the combat rating but this doesn't mean it couldn't be used. Here's the Merlin 46 static output at 16lb boost:
http://www.wwiiaircraftperformance.org/Merlin_46_47_Power_Chart.jpg

I agree that pilots wouldn't usually "pull the plug" unless there was very compelling reasons to do so but I'm certain that the RAAF Spitfires had access to the full combat rating of the engine if they wished to use it.

HANDLING AND FLYING NOTES FOR PILOT
NOTE: The flying technique outlined in these Notes is based on AP.129,
Flying Training Manual Part 1, Chapter III and AP.2095, Pilot's
Notes General, to which reference should always be made if further
information is required.
1. Engine data: Merlins 45, 45M, 46, 50, 50A, 50M. 55 and 55M.
(i) Fuel: 100 octane only.
(ii) Oil: See AP.1464/C.37.
(iii) Engine limitations:
R.p.m Boost lb/sq.in Clnt.Temp ºC Oil. Temp ºC
Max take-off to 1,000 feet 3,000 +12 - -
Max climing 1 hr, limit 2,850 +9 125 90
Max rich continuous 2,650 +7 105 (115) 90
Max weak continuous 2,650 +4 105 (115) 90
Combat 5 ins limit 3,000 +16 +18 135 105
NOTE:
(a) +18 lb/sq.in. boost is obtained, only on "M" type engines, by
moving the throttle lever through the gate. On other engines +16
lb/sq.in. boost is obtained by operating the boost control cut-out.
(b) Combat boost is permitted only at 2,850 to 3,000 rpm.
(c) The figure in brackets is permitted for short periods if necessary.

tomo pauk · Apr 22, 2016

Kinda shows that a R-2800 powered fighter, from Pearl Harbor on, woud've come in handy for the needs of USA/USMC and the Allies that otherwise received Wildcat

pinsog · Apr 22, 2016

tomo pauk said:
Kinda shows that a R-2800 powered fighter, from Pearl Harbor on, woud've come in handy for the needs of USA/USMC and the Allies that otherwise received Wildcat

Or the F5F Skyrocket

Wow, the tropicalized Spitfire is 10 mph slower than a Wildcat at sea level and only 10 mph faster at 10,000 feet. I wouldn't have believed that if someone had told me.

RCAFson · Apr 23, 2016

pinsog said:
Or the F5F Skyrocket

Wow, the tropicalized Spitfire is 10 mph slower than a Wildcat at sea level and only 10 mph faster at 10,000 feet. I wouldn't have believed that if someone had told me.

Here's proof that that's not true and proof that the RAAF used 16lb boost:

To RAAF HQRS

From OHQ RAAF KWAY

6 Sept 1943

Spitfire Aircraft Engineering.

5 Spitfire Mk 5 aircraft given extensive test fights here successively with each of the following types of of air intake assembly and engine cowling. (A) original tropical (B) New Tropical with bypass valves (C) Temperate.

Average max speeds were

1 sea level) A) 312 B) 312) C) 316

2 10000ft) A) 355.5 B) 355.5 C) 360

3 at FTH ) A) 357 B) 358.5 C) 363

Considered that improvements in speed were too small to warrant departure from original type tropicalization hence new scheme will not be applied retrospectively to Mk5 aircraft. Latest tropical intake with bypass valve will be incorporated Mk 8 aircraft.

from Australian Archives:
Title
DTS [Directorate Technical Services] - Spitfire Aircraft - Performance comparison - tropical and non-tropical types
Contents date range
1942 - 1944
Series number
A705

BWOC here's the RAE chart for Spitfire V speed with 16lb boost pencilled in:

http://www.wwiiaircraftperformance.org/Spitfire_V_Level_Speed_RAE.jpg

stona · Apr 23, 2016

The Australians went from a position where they were seriously worried about the effect on performance of the Vokes filter on their Spitfire Vs, to one where they realised the effect was nowhere near as deleterious as they had feared.

They also discovered that there were much simpler ways of improving performance which did not involve developing new filter systems and cowlings. They could just about compensate for the Vokes filter by treating the leading edge of the wing, something that was introduced into production slightly after this date and cleaning up the surface of the aircraft. It was also important to ensure the fit of all cowlings and access panels to ensure they were a sealed fit and did not allow air to pass inside them. This is just an aspect of good maintenance, something sadly lacking, not just in Australia, much to the dismay of the Air Ministry (UK) and manufacturers.
A Spitfire wing's leading edge has a butt join between the upper and lower skins and two rows of rivets attaching these skins to the internal structure. It is an obvious area for smoothing.

Whether the ejector exhausts were available in Australia I doubt, but other measures could be taken locally.

Cheers

Steve

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