Spitfire V vs. Zero: Test Results

[BuzzLightyear]

I posted these on another site. I found them searching the National Archives of Australia. Hope you find them interesting:

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Regards,

Rowland

[tenmmike]

excellent post thanks for sharing

[ickysdad]

2 questions...
1.What model of P-38 did the "Tony" encounter? Late model J's & L's would leave it in the dust in a dive as would just about any USAAF/USN fighter.
2. Spitfire V? How about a Spitfire IX?

[BuzzLightyear]

quote:Originally posted by ickysdad

2 questions...
1.What model of P-38 did the "Tony" encounter? Late model J's & L's would leave it in the dust in a dive as would just about any USAAF/USN fighter.
2. Spitfire V? How about a Spitfire IX?


Hmmm...

1) Dunno. Given the date of the report, August 1943, I think it was neither a J nor an L. Certainly something earlier, perhaps an F, G, or H.

2) AFAIK, no IXs made it to Australia during the time frame raids on Darwin were taking place. I'm not sure that IXs were even used very extensively in that theater. Certainly the IX would have compared more favorably in speed, climb, etc... But in terms of low speed manueverability, I believe it would have still come in second.

[GregP]

For those of you who can't read the six pages above, my translation goes as follows. If you see mistakes, please post them here.

Section 1: Fighter Tactics
Tactics of Japanese "Tony" Type Fighter
1. The 80th Fighter Squadron has twice encountered "Tony" type fighters in combat, both times in the vicinity of Bogadjin. The first time was on 21 Jul 43 and the second time was on 23 Jul 43.
2. From these experiences with this type fighter not much information has been brought to light. However, pilots have reported speeds up to 400 mph indicated air speed in this type fighter.
3. One pilot reported having followed one of this type fighter from eighteen thousand feet to sic or seven thousand feet. A shallow dive was maintained all the way with the P38 indicating 400 mph, and during this time the P38 was unable to gain on the enemy. At this time another P38, indicating close to 500 mph, dived from above and succeeded in shooting the enemy plane down after a long accurate burst. Another indication of the speed of this type of fighter may be derived from combat on 21 Jul 43 when a P38 found the enemy fighter behind him. The P38 went into a shallow dive and was unable to lose the enemy when indicating 400 mph at low altitude. This "Tony" was finally chased away by another P38 who dived from above firing a burst at long range.
4. In combat in this squadron there has been no indication as to the maneuverability of the enemy fighter. However, the "Tony" has, on one or two occasions, shown no inclination to get into a steep dive when that action would seem to be advantageous to him. In each case where P38s have been on the tail of a "Tony" the only action taken by the enemy has consisted of maintaining a gradual dive with speed building up to 400 mph.
5. There are further indications that the "Tony" is not as apt to catch fire as are the "Zeke" and "Oscar". Although they have been shot down in flames in several cases, a long accurate burst was necessary to accomplish this destruction and they did not show a tendency to explode which has been characteristic of the Japanese fighter airplanes


Tactical Trials Between Japanese S.S.F. Type "0" Mark II "Hap" and Spitfire V.C.
1. Comparative performance trials were not carried out at the time and these performance figures will be supplied at a later date.
2. Both aircraft were flown at normal combat weight minus belly tanks.
3. Brief Particulars of Hap:
a. Take-off run - 900' using 2600 rpm and 30" MP.
b. Approach speed, wheels and flaps fully down - 75 knots.
c. Stalling speed, landing condition - 53 knots.
d. Rated altitude - 16,000'.
e. Combat ceiling - 32,500'.
f. Maximum speed at rated altitude - 335 mph, 2600 rpm, 40" MP.
g. Armament - 2 x 7.7 synchronized machine guns, 600 rounds per gun (Identical with Vickers). British .303 ammunition may be used - 2 x 20 mm cannons, 100 rounds per gun Identical to Oerlikon).
h. Figures shown in b, c, and f are approximate. Air speed indicator had not been calibrated.

4. Flying Characteristics of Hap
a. No tendency to swing in take off or landing. However, a tail wheel locking device was incorporated since the brakes were inoperative.
b. Short take off and landing runs.
c. Good visibility.
d. Stick loadings normally not light and increasing with speed. This is more evident with right stick.
e. Movement of elevator trim extremely stiff.
f. Rudder loading normal but tiring in climb due to absence of rudder trim.
g. Very stable stalling characteristics. No tendency to spin even in high speed stalls.
h. Extremely maneuverable at low speeds, rolling off the top of loops can be executed at 180 knots.
i. Boost gauge calibrated in centimeters.
j. Seating position cramped, rudder position to suit short legged pilots only.


Test No. 1 - Commencing at 17,000 feet:
1. Spitfire and Hap to approach head on and maneuver, without loss of altitude, until one aircraft gets on the other's tail.

Result:
Both aircraft passed at about 50 yards. Spitfire executed steep climbing turn. Hap dteep turned and was on Spitfire's tail within 2½ turns.
2. Hap on Spitfire's Tail. Spitfire to complete 4 steep turns to left. Reform position and carry out 4 steep turns to right.
Result:
Hap was able to turn easily inside Spitfire. However, jinking was necessary to watch Spitfire and check on deflection allowance. Hap did not steep turn as easily to right as to left.
3. Spitfire on Hap's Tail. Steep turns to left and right as in previous test.
Result:
Hap commenced steep turning at 220 mph IAS. Spitfire was unable to turn with Hap., either in left or right hand turns, for more than ¾ turn by which time Spitfire was close to stall.
4. a. Hap on Spitfire's Tail. Spitfire to perform loop.
b. Spitfire on Hap's Tail. Hap to perform loop.
Result:
a. Spitfire commenced looping at 300 mph IAS with speed of 140 mph IAS on top. Hap had no trouble in following Spitfire.
b. Hap commenced lop at 220 knots IAS and completed two loops in succession. Spitfire endeavored to follow Hap and stalled at top of first loop and fell out. Hap finished on Spitfire's tail.
5. Hap on Spitfire's tail. Spitfire to shake Hap off.

Result:
Spitfire commenced evasive action by executing diving aileron rolls to right. Hap had difficulty in following this maneuver and was unable to get into firing position. Spitfire then did a high speed vertical climbing turn which Hap was just able to follow. Hap was able to comfortably follow all other maneuvers which were not carried out above 250 mph.


Conclusion:
1. Hap considerably more maneuverable than Spitfire at low speeds.
2. Hap stalling speeds considerably lower than Spitfire.
3. Hap able to turn and loop in much smaller radius.
4. Hap able to carry out any aerobatic maneuver at a much lower speed than Spitfire, e.g, roll off the top of loop - Hap 205 mph, Spitfire 250 mph.
5. Hap experienced considerable difficulty in following Spitfire in High-G, High-Speed maneuvers, especially to right.
6. At medium and low levels Hap easily able to evade Spitfire abd turn the tables.


Recommendations:

1. Do not attempt to dogfight the Hap, especially at low airspeeds.
2. If you have a height advantage, use excess speed obtained in your diving attack to climb vertically thus retaining your height advantage.
3. High Speed - High G tactics will considerably alter the disparity in maneuverability.
4. Keep your speed high. Don't stagger through the sky.


Test No. 2 - Commenced at 27,000 Feet:

The results obtained in Test No. 1 were confirmed and the following additional conclusions were reached.

1. Spitfire had an approximate advantage of 25 mph at 26,000 feet.
2. Spitfire had a slight advantage in rate of climb at 26,000 feet.
3. Spitfire initially gained speed slightly faster in a vertical dive.
4. The Spitfire's advantage in 2 and 3 are not sufficient to evade the Hap's fire.
5. At altitudes over 20,00 feet with a height advantage of approximately 3,000 - 4,000 feet, the Spitfire can dive and attack the Hap with impunity. The breakaway would be made in a vertical climb, thus maintaining height advantage.


Tests No. 3 and 4 - Commenced at 17,000 and 32,000 Feet Respectively:

1. No appreciable differences were noted at 17,000 and 27,000 feet.
2. A special Spitfire was used for these trials.
3. All maneuvers were carried out at high speed and high "G".

Results:
Hap commenced tests on Spitfire's tail:
1. In high speed flight, Spitfire was able to loop in a smaller radius. Hap pilot blacked out endeavoring to follow.
2. Spitfire carried 3 loops in succession at high speed and finished in firing position on Hap's tail.
3. Spitfire carried out roll off top of loop. Hap was unable to follow in same radius and lost considerable distance.
4. Spitfire executed a series of high speed, tight diving turns to right; Hap pilot unable to follow and was on verge of graying out.

5. Spitfire executed a ½ roll to right from 45° dive at 280 mph IAS and 330 mph IAS and pulled out abruptly into vertical climb. Hap pilot unable to follow this maneuver either at 280 or 320 mph and finished up in both instances approximately 1000 feet below Spitfire and some distance behind.


Conclusions:
1. Spitfire was able to evade and outmaneuver Hap by combining high speed and High "G".
2. Spitfire required a minimum speed of 250 mph to retain maneuverability advantage.
3. Hap was able to evade and outmaneuver Spitfire by maneuvering at low speeds.
4. Stresses placed upon both aircraft during tests were not measured. However, the Hap pilot considers his tolerance in reference to blacking out to be above average.


Spitrfire vs. Zero
Report of Combat - 2/3/43
Duration of engagement was approximately eight (8) minutes from the time of first attack on enemy formation, which was well enough disposed for its purposes. The enemy tactics employed in this first instance were, I consider, unsound and based on false premises, and/or lack of experience.

When first sighted the enemy were flying in 3 sections as follows.
No. 1 E/A section comprised of 3 single engined L.E with a close escort of 3 Zekes at a height of approximately 10,000 feet. No. 2 E?A section comprising 4 Zekes about 400 yards on the port beam of No. 1 E/A section and approximately 2,000 feet above them. No. 3 E/A section comprising 5 Zekes about 800 yards on starboard beam of No. 1 E/A section and approximately 5,000 feet above them.
The positions of my own formations of 6 Spitfires flying in 3 sections of 2 aircraft in line astern, section abreast, was at this time approaching from slight astern of the starboard beam of the enemy formation, height slightly above the No. 2 E/A section , at an IAS of 230 mph.
The enemy made no attempt to alter the disposition of their aircraft though our approach must have been observed, but continued to fly as before at approximately 190 mph IAS (estimation).
From what took place subsequently it was obvious that the enemy considered we would not place ourselves beneath the Zeros, but attempt in the first place either climb away for height in order to engage the top or No. 3 E/S section, which would then no doubt have climber also, or alternatively, if failing to observe the top cover to move across and engage the No. 1 E/A section, thus leaving ourselves open to attack in the rear by No. 3 section E/A above.
My own tactics were governed primarily by our pressing shortage of petrol.
We had been airborne at this stage approximately one hour fifteen minutes mostly at altitudes in excess of 20,000 feet under fighter sector control.
My own tanks showed less than 30 gallons, which as leader would exceed that of any of the other 5 Spitfires. We were now 40 or more miles from our base on a vector and at a height instructed by 5 fighter sector, and a Spitfire at combat revs and boost uses petrol at a rate between 70 and 90 gallons per hour. Therefore it was impractical waste time and petrol in attempting to climb after the top cover or No. 3 section of the E/A section. To attack No. 2 section on our left, in view of the position of No. 3 section, or to attack No. 1 E/A section from astern, in view of the respective positions of No. 2 and No. 3 E/A sections would have been inadvisable in the extreme.
I therefore flew my formation directly under the No. 3 E/A section and some 3,000 feet below, where any attack from them must be preceded by such maneuvers as to give us sufficient warning to meet it. That is the Zekes directly above must either turn on their backs and attack vertically downwards, a difficult shot and easily avoided; loop fully as they are credited with doing so freely, thus going behind us, or losing height to turn onto out tails, in either case giving us sufficient warning. When abreast of No. 1 section E/A, I dived to attack at a steep angle from full beam breaking to the rear in a wide climbing turn to port and was followed into the attack by the rest of my formation. No. 3 section of the enemy, the top cover, appeared slow to appreciate the significance of the move and failed to get position behind us in time to be dangerous.
No. 1 E/A section moved herein to intercept us directly, but were not successful in doing so, and the break to the rear gave us enough clear air momentarily, to sustain the altered position, and at the end of the zoom I found I was well up in height in relation to the Zekes which had lost height after us. A diving head-on attack was refused by a Zeke who broke downward before coming to range. This was repeated in the case of another Zeke a few minutes later. I observed several Zekes firing on me and took momentary action, others not seem may have fired, but the shooting was bad despite liberal use of tracer, and the attempts at correcting aim were poor. Engaging in turns with a Zeke at about 180 mph IAS and pulling my aircraft as tight as possible, the Zeke did not dangerously close, until the speed began to drop, about the completion of the second turn. Breaking severely downward to the inside of the turn I experienced no difficulty in losing the Zeke. My engine cut momentarily in this maneuver. I observed Zekes to loop, to half roll and fire while on their backs, which, though interesting as a spectacle seemed profitless in dogfighting.
During the engagement I saw a Spitfire diving away with a Zeke on its tail. The Spitfire appeared to be gaining distance.
When leaving the combat area, I dived steeply away and was followed down in a dive by a Zeke. At a speed in excess of 400 mph IAS the Zeke did not close the distance and gave up quickly, though supported by several of his kind. The Zekes appeared to be armed with M.G. and 30 mm cannon.
To summarize, in view of the whole circumstances surrounding the brief engagement, and despite the fact that both height and numbers favored the Zekes, I regard the Spitfire as a superior aircraft generally, though less maneuverable at low speeds. In straight and level flight and in dives the Spitfire appears faster.
Though the angle of climb of the Zeke is steeper, the actual gaining of height seems much the same, the Spitifre going up at a lesser angle but at greater forward speed - an advantage. No difficulty was experienced in keeping height with the Zekes during combat. I believe that at altitudes above 20,000 feet the Spitfire, in relation to the Zekes will prove an even more superior aircraft in general performance.
It must be remembered however, that the Japanese pilots had been airborne for a very long period and their efficiency must necessarily be impaired by consideration of fuel conservation and fatigue.

(Signed Clive "Killer" Caldwell) C. K. Caldwell,
Wing Commander,
Wing Commander flying,
No. 1 Fighter Wing,
R.A.A.F Darwin

[Corsarius]

You mean Clive "Killer" Caldwell, Australia's leading ace of WWII.

[simon]

Very nice post Greg!

Going from memory, was the "Hap" another name that was given for the "Tony"?

[GregP]

The "Hap" was the original code name for the Japanese Zero fighter. Since this embarassed "Hap" Arnold, they changed it to "Hamp". Later, it was changed yet again to "Zeke." Still later, the fighter came to be known by its Japanese designation, Type "0", and it was called the "Zero" from then on.

So, Hap, Hamp, Zeke, Zero ... were all the same famlity of fighters at different times. Let's keep in mind the A6M2 Zero was a far different animal than the A6M6 Zero so, in reality, the Hap and Hamp were early versions, the Zeke came in about the time of the A6M6, and the Zero meant any or all of the above.

In any case, it was a superb dogfighter that lascked rudder trim, poilt armor, self-sealing fuel tanks, and a few other "amenities" taht U.S. pilots took for granted. However, it was light and had very high performance for a 1,000 HP aircraft. To get similar performance, the Hellcat used 2000 HP. Late model Zeros had about 1500 HP. but were never given an engine with power similar to the Hellcat in any variant.

It also was never as strong as a Hellcat, and had a lower limiting dive speed as well as controls optomized for 250 MPH or so. Above 380 MPH, they got VERY hard to handle. Above 400 MPH, the Zero was not maneuverable at all.

Still, when flown at its best cornering speed, the Zero was always a superb aircraft, with no bad tendencies and very light and numble handling.

[BuzzLightyear]

Thanks for posting that GrepP. I had to take the images down due to bandwidth restrictions.

[R Leonard]

You need to look into A6M series production a little more.

There were quite a few versions and not at all in the chronology that you posted.

The A6M1 first flew on 1 April 1939. It was powered by a 780 hp Mitsubishi radial engine. Initial testing of this airplane and a second prototype first flown in October 1939, showed the design to meet the requirements of the contract specifications in all respects except speed.

The A6M2 is what was commonly known as the Zero (from “Type 00” which devolves from the production year in the Showa calendar). This plane received the Allied code name of “Zeke”. This airplane was an improvement over the A6M1 incorporating a 925 hp Nakajima NK1C Sakae radial engine. First flown on 18 January 1940 the A6M2 overcame the speed problem and on 31 July 1940 was ordered into production as the Type 00 Model 11. The Model 21 was essentially the same airplane with folding wing tips for carrier-based operations.

Next came the A6M2-N which was the floatplane fighter version, code named “Rufe”. This was a stop gap airplane for posting in and providing fighter coverage in places remote from landing fields. It did not fare well against fighter opposition primarily due to the performance limitations resulting from the addition of floats.

Next came the A6M3, by appearances a clipped wing version of the A6M2, code named, as you noted, originally as “Hap” and later changed, to mollify an incensed “Hap” Arnold, to “Hamp” This airplane was powered by a 1,130 hp Nakajima NK1F Sakae engine with a two-stage supercharger and was designated the Model 31. In practice it was found to less range than the Model 21.

The next variant was an A6M3 with the folding wing tips as were on the Model 21 and internal wing fuel tanks to solve the range problem. This version became the Model 22. This version reverted to the “Zeke” code name for the Allies. Thus, the difference between the Zeke and the Hamp was strictly visual and was related to the shape of the wings. The Hamp was later known as the Zeke 32 as the Allies realized the Zeke and the Hamp were variants of the same aircraft.

The A6M4 line was limited to two prototypes converted from A6M2’s and powered with an experimental turbocharged Sakae engine.

The experimental engine did not work out, so the next version in the A6M series was the A6M5 or Model 52. This airplane retained the 1,130 hp Sakae engine but with the exhaust ports redesigned. And was armed with two 20mm Type 99 cannon and two 7.7mm machine-guns. The wing tips were no longer folding as with the Model 21 and 22, but were slightly clipped. Unlike the Model 31, however these tips were rounded instead of clipped. The A6M5 Combat sub-types of the A6M5 included the A6M5a, with wing cannon installation modified to accept belt-feed instead of magazine-feed ammunition; A6M5b which had one of the 7.7mm machine-guns replaced by a 13.2mm machine-gun and included armored glass in the canopy and and a fuel-tank fire extinguisher system; A6M5c with three 13.2mm machine-guns and two 20mm cannon; and lastly, the A6M5d-S night-fighter version with an obliquely-mounted 20mm cannon in the rear fuselage. From the Allied code name perspective, the A6M5 was still a “Zeke”, albeit a “Zeke 52”.

The A6M6 was an A6M5 airframe with a Nakajima Sakae 31 type engine with water-methanol injection for increased speed. The A6M6 also was the first of the series to have self-sealing fuel tanks. Some A6M6’swere modified further to carry a 551-pound (225-kg) bomb in place of a drop-tank.

The A6M7, the final production version of the airplane service in mid-1945, was specifically designed to carry a centerline mounted bomb. To off set the lack of a centerline drop tank, the wings were strengthened and attachments for two underwing drop-tanks added.

The last version of the A6M series was the A6M8 of which there were two prototypes. Converted from the A6M7, the A6M8 sported a strengthened fuselage, allowing the installation of a 1,560 Mitsubishi engine. The war ended before this airplane could go into production.

Contrary to popular opinion, the whole series had some decidedly bad handling characteristics, especially at high speeds where in the fighter pilot world “speed is life”. The Zero was designed to relatively low speed, acrobatic dog fighting a la the First World War, a concept that rapidly going out of date when the war broke out in the Pacific and was totally out of date by early 1943. Japanese doctrine and tactics were hand-in-hand with this outmoded thinking. The result was, divorced from the structure of divisions and sections (another subject altogether) and tactics in general, was an aircraft that could not perform aileron turns at high speeds; in the A6M2 an engine that cut out in high speed push-overs; and, in all versions, attempting moderate to high deflection shots required the pilot to drop his nose to see his intended target then bring it back up in order to fire, thus enabling an attentive victim to breakaway in another direction when out of the Japanese pilots field of view. In effect, this was an airplane that was only effective if you played by its rules, any departure from the Zero’s optimal performance envelope drastically reduced its effectiveness and, of course, increased one’s chances of, at least, escaping being damaged or shot down and, at best, turning the tables and damaging or shooting down the Zero.

For what it is worth, here’s some quotes from various copies of some USAAC and USN performance comparison reports in my collection on the A6M2 recovered from the Aleutians:

Lieut. Comdr. ER Sanders writes in his A6M2 report of September 29, 1942:

"All controls are very light, free from friction and all are over-balanced statically. High maneuverability at normal speeds is obtained with small control movement. The ailerons are unusually long and lateral control is excellent right down to the stall. Aileron forces increase with speed. They are still fair around 200 KTS to 210 KTS, but at 230 to 250 KTS they practically freeze up and fast rolling cannot be done at 250 KTS. Could detect no buffeting or reversal at maximum displacement obtainable which is very small at high speed. The rudder is light and very effective. The elevator is the only control on which there is much change in trim with speed and power changes and that is not excessive. An adjustment elevator tab is the only tab provided. The others are fixed. Action from movement of any control is immediate.

"The plane handles remarkably like an SNC-1, feels about as light and maneuvers about the same. The main difference is in the ailerons where much less movement is needed for the rolling effect.

"The horizon was not working, but by estimating the angles, obtained 1.35 sec. to the right, and 1.1 sec. to the left for the standard rate of roll test in landing condition. The angle was probably more like 60 degrees. Rate of roll at 200 KTS was 5.4 sec. for 360 degrees. This was with not much more that half aileron displacement, but it was as far over as I could put it because of the high forces. Forces are higher to the right than left."

Some of Sanders' pertinent points in his evaluation were:

"Engine quits on push-overs"

"Ailerons get very stiff at higher speeds making fast rolls at high speeds (above 250 knots) physically impossible. At 200 knots the rate of roll (with ailerons) is slightly slower than an F4F. At lower speeds the Zero probably has an increasing advantage in any rolling maneuvers since it is highly maneuverable."

"Started getting considerable vibration and some flutter at 280 knots indicated. May be peculiar to this plane, but believe the diving speeds are probably considerably restricted."

"Believe F4F would accelerate faster in a dive and could roll or spiral at high speeds in such a way that a Zero could not follow because of aileron forces along [sic], if not speed and acceleration restrictions necessitated by strength limitations."

[note: I believe the word after "forces" above should be "alone" not "along".]

My particular copy of the Sanders report has a cover distribution and memo dated November 29, 1942 from Headquarters, Allied Air Forces, South West Pacific Area, Directorate of Intelligence and signed by Major Frank T. McCoy, USAAC.

From "Technical Aviation Intelligence Briefing #3" dated November 4, 1942 and published by the Navy's Aviation Intelligence Branch, Bureau of Aeronautics:

"Distribution - All ships and Units concerned with aircraft."

[. . . not bothering with background history information in the beginning of the report . . .]

"GENERAL: All metal low-wing monoplane, flush riveted with clean smooth exterior. Great emphasis has been given to saving weight wherever possible. Wing is integral with the fuselage, no leakproof tanks or armor, and wings fold only at tips. Landing gear, flaps and breaks [sic] are hydraulically operated. Visibility is excellent with no difficulty seeing astern. Cockpit is not much more cramped than a Spitfire, except that the longest pedal position is quite short and knees stick up rather high. Arrestor hook retracts into lower part of the fuselage. Flotation bag in rear of fuselage - watertight compartments in wings, outboard of cannons."

(Report continues with statistics on dimensions, weights, engine, propeller, armament, instruments, fuel capacity, and oil capacity. Then some fun stuff:)

"PERFORMANCE
"Maximum speeds and rates of climb are given below.
"Maximum speed.. Sea level.........270 (m.p.h.)
.........."..........."........5,000 feet.…..287......"
.........."...........".......10,000..."........305......"
.........."...........".....*16,000..."........326......"
.........."...........".......20,000..."........321.5..."
.........."...........".......25,000..."........315......"
.........."...........".......30,000..."........306......"

"Rate of Climb... Sea level..........2750 (ft/min)
....."...."......".......15,000 feet........2380......"
....."...."......".......20,000 feet........1810......"
....."...."......".......30,000 feet..........830......"

" * Critical Altitude.
"SERVICE CEILING: 38,500 feet."

The real good stuff in the report talks about the Zero's characteristics and comparison with the F4F-4 and the F4U-1. It echoes the Sanders report:

"CHARACTERISTICS:

"STABILITY: (a) Longitudinal stability is positive throughout. The elevator control is light and effective, and has very desirable control movement characteristics. (b) Directional stability is positive and control is light. There is no rudder trim tab and a moderate pedal force is carried in climb. (c) Lateral stability is positive in cruise condition and close to neutral in landing condition. Ailerons are abnormally large and the rate of roll at low speeds is extremely high. However the ailerons forces increase excessively with airspeed, and above 200 kts. indicated the airplane is very difficult to roll. At speeds above 250 kts. it is almost impossible to maneuver the plane laterally. At moderate to high speeds the rate of roll to the right is definitely lower that to the left, due to relative control forces.

"COMPARISON WITH F4F-4: The Zero is superior to the F4F-4 in speed and climb at all altitudes above 1000 feet, and is superior in service ceiling and range. Close to sea level, with the F4F-4 in neutral blower, the two planes are equal in level speed. In dive the two planes are equal with the exception that the Zero's engine cuts out in pushover. There is no comparison between the turning circles of the two airplanes due to the relative wing loadings and resultant low stalling speed of the Zero. In view of the foregoing, the F4F-4 type in combat with the Zero is basically dependent on mutual support, internal protection, and pull-outs or turns at high speeds where the minimum radius is limited by structural or physiological effects of acceleration (assuming that the allowable acceleration on the F4F is greater that that for the Zero). However advantage should be taken wherever possible, of the superiority of the F4F in pushovers and rolls at high speed, or any combination of the two.

"COMPARISON WITH THE F4U-1: The Zero is far inferior to the F4U-1 in level and diving speeds at all altitudes. It is inferior in climb at sea level. And inferior above 20000 feet. Between 5000 and 19000 feet the situation varies. With slightly more that normal fighter load, which may be distributed to give equal range and gun power, the Zero is slightly superior in average maximum rate of climb. This superiority becomes negligible at altitudes where carburetor air temperatures in the F4U are down to normal; close to the blower shift point it is more marked. However, the Zero cannot stay with the F4U in high speed climbs. The superiority of the F4U at 30000 feet is very marked and will persist at considerably higher loads. Attention is called to the fact that in the foregoing condition of loading all fuel in the F4U-1 is protected. In combat with the Zero, the F4U should take full advantage of its speed, and its ability to pushover and roll at high speed if surprised. Due to its much higher wing loading, the F4U should avoid any attempt to turn with the Zero unless at high speed, and may expect the latter to outclimb him at moderate altitudes and low airspeeds. In this case the F4U should continue to climb at high airspeeds and on headings which will open the distance and prevent the Zero from reaching a favorable position for diving attack. After reaching 19000-20000 feet the F4U will have superior performance in climb and may choose its own position of attack."

The US Army Air Forces "Informational Intelligence Summary No. 85 -Flight Characteristics of the Japanese Zero Fighter" was distributed to all squadrons. It summarizes the Sanders and Navy Comparison reports and provides comparisons with the P-38F, P-39D-1, and P-51.

Particularly though, the report draws the following general conclusions and recommendations:

"Conclusions:

"The Zero fighter, because of its low wing loading, has superior maneuverability to all our present service type aircraft.

"It is necessary to maintain a speed of over three hundred (300) miles per hour indicated to successfully combat this airplane.

"In developing tactics against the Zero, cognizance should be taken of two facts:

1. Slow rate of roll of the Zero at high speeds.

2. Inability of the Zero engine to continue operating under negative acceleration.

"The engine performance of the Zero is superior to the present service type engine without turbo superchargers. This superiority is recognizable in the fact that the maximum manifold pressure can be maintained from sea level to sixteen thousand (16,000) feet.

"Recommendations:

"That the pilots entering the theater of action where the Zero can be expected be instructed in the following:

1. Never attempt to dog fight the Zero.

2. Never maneuver with the Zero at speeds below three-hundred (300) miles per hour indicated unless directly behind it.

3. Never follow a Zero in a climb at slow speeds. (Service type ships will stall out at the steep angle where the Zero has just reached its most maneuverable speed.) At this point is possible for the Zero to complete a loop putting it in a position for a rear quarter attack."

And lastly here’s the comments made by an experienced USN fighter pilot, an ace with 2 A6M2’s to his credit:

“I first saw the captured Zero as a pile of salvage shortly after it arrived from Alaska. Soon after I was sent to the Southwest Pacific and didn’t see the plane again until August 1943 when I was assigned as fighter training officer at San Diego.

“The Zero had gone to Tactical Air Intelligence Center and was based at Anacostia Naval Air Station, near Washington, D.C. After Sanders, Hoffman, and others tested, compared, and evaluated the airplane, the Army put it though similar paces.

“While fighter training officer at San Diego, I learned that Koga’s Zero was still at Anacostia, airworthy, but unused. I arranged for it to be flown to San Diego. The Zero 21 was a mighty sweet machine, even in its superannuated state. The refined aerodynamic design was not compromised by mass production. Fit and finish of all plates, rivets, the close and accurate fit of fairings, engine cowl, access plates, canopy, and wheel doors were most faithfully executed.

“The propeller spinner faired into a cowling that smoothed the contours of the reduction gear housing of the engine. The interior aerodynamics of the engine cowling permitted the adequate cooling of the two-row 14-cylinder engine with a remarkably small intake. Contrast that with the inlet on the F4F-3 and -4 which originally came with a spinner but had to sacrifice it to cure engine overheat problems. The Sakae engine looked and sounded much like our R-1830. It ran smoothly and cool. Displacement was somewhat less that the Pratt and Whitney 1839, but its 1130 hp was smoother and adequate. It was not supercharged as extremely as the R-1830-76/86 and at very high altitude (over 30,000 feet) compared very poorly with the Pratt and Whitney. But we hardly ever encountered Zeros above 10,000 feet with our F4F-3s and -4s, so we were carrying supercharger hardware as extra baggage. The F4F, which became the FM-2, was re-engined with the Wright R-1820 with about the same power as the R-1830, but much less supercharger. This was a better machine to fight Zeros with, but we didn’t get in squadrons until 1944, and by that time the Zero was not the problem it had been in the beginning.

“By the time I was flying the Zero 21 it may have had some of its automatic systems disabled. An example is the automatic altitude compensation of carburetor mixture. The first time I went for altitude the engine began to cut up disgracefully above 5000 feet. Worried that the engine was giving up, mixture came to mind. On this machine full rich is a rearward position of the mixture control. Manual leaning comes by easing this control forward. On doing this gingerly the engine smoothed up beautifully and the airplane jumped ahead with about 500 more horses - no less.

“The propeller was auto hydraulic cum Hamilton – no mysteries. We ran the engine as though it was an R-1830, but did not let the RPM go over 2600.

“The case of the manifold pressure gauge had been cracked n the crash at Akutan and it leaked. It was left in the instrument panel, but we used a standard AN type attached to a bracket nearby.

“The throttle sat in a quadrant outboard of the mixture control. It was shaped like the handle of a knife – complete with wood side plates for contour. It was about five inches long and on the top had a switch to be operated by the left thumb. This switch was for cutting in or out the 20mm cannon.

“The Zero carried many rounds of 7.7mm for the two fuselage guns and only 80 to 100 for each of the 20mm wing guns. Ergo, sight in with the 7.7 then cut in the two 20s for telling shots. I dimly remember there was a trigger lever you could pull up and squeeze on the front edge of the throttle. If you were not in combat, this lever would drop down where inadvertent firing was precluded (we had sad events because the trigger on the stick of U.S. fighters was easily squeezed in excitement).

“Cockpit was not so tidy as the F4F, but easily as tidy as the F4U and earlier Vought birds. Instruments were much like ours, but metric for pressures, temperatures, [and] altitude. Airspeed was in knots. It had an inner and outer scale as the needle needed to go around about 1½ circles to get to the high end of the scale.

“In the Zero 52 there was an exhaust temperature gauge as well as the usual cylinder head temperature gauge. My guess is that it was a refinement to fine tune the mixture to get the remarkable endurance and range the Zero was famous for.

“Gyro horizon had a sky blue upper half like some of the German WWII instruments I have seen. To the envy of every F4F pilot, the landing gear was hydraulically actuated!

“Tail wheel was fully retracted behind tight doors. Tail hook was faired into a recess along the keel. The hook was hinged on the end of its strut, latched in the snatch position to catch the wire then dumped, so the Zero could taxi forward over other wired unimpeded. I understand we toyed with this idea but gave it up because of worries it might misbehave and cause an unarrested landing.

“Brakes were hydraulic – weak. The wide tread and relatively low landing speed favored weak brakes so you might say they were adequate. Rudder bar was center-pivoted with stirrups for each foot. Brakes were actuated by a hand lever; rudder angle determined which wheel received braking action.

“The canopy gave a beautiful view of the outside world, noticeably good to the rear in contrast to our VF’s. The enclosure was made up of many panes of plexi, some contoured. Wind noise was moderate. Some of the enclosure had been destroyed and was remade by A and R.

“The windscreen section was original, for it bore deep craters from the corrosion that took place during its dip into the marsh of Akutan. These cavities had a way of coming into focus when air speeds built up. I often wondered why they had not been replaced by A and R. In VF-42 we had some nasty experiences with the original F4F windscreens blowing out on use when flying at more that 300 knots. Grumman corrected it with a beef-up that robbed us of valuable forward vision, but it ended the problem. The Zero had no such heavy structure in the first place, so it was a source of uneasiness.

“The Zero 21 had no primer for engine starting. The carburetor had a large capacity acceleration pump you feel when you moved the throttle. To start, you had the mechanic wind up the inertia starter as you wobbled up fuel pressure and work the throttle two or three times to spray in the discharge of the accelerator pump. On contact the engine rolled over readily, caught, and picked up to run without complaint.

“The carburetor barrel has an oil jacket through which circulated lube oil to combat any tendency to form ice. I’m not sure whether it was always in action of selectable from the cockpit. We never touched it as I remember. Seems a tidy way to handle ice.

“In February-March 1945 I had a dandy low-time fresh-caught Zero 52 to fly. It was much like Koga’s Model 21, but heavier because of two more guns. It had a hundred or so more horses, and ejection type exhaust stakes, but flew essentially like the Model 21 – very sweet.”

Regards,

Rich

[Corsarius]

Please note that there is comparability between this report, and Caldwell's combat report versus Zero fighters in the spitfire.

Caldwell had the Zeros at altitude above him, that suddenly flew inverted to attack him below, something he regarded as foolish tactics.

When comparing that with this previous note, you can see that if the Zero's engine had a tendency to cut out if 'pushed over' into the dive, then this tactic would make more sense.

Thinking also of this, the Spitfire had a similar negative-g problem, which required the pilots to do a half-roll before following a Bf-109 into a dive, with it's superior fuel injection system allowing it to do negative-g without difficulty.

[BuzzLightyear]

Here is a few more pages from that report:

http://members.cox.net/rowlandparks/21.jpg
http://members.cox.net/rowlandparks/22.jpg
http://members.cox.net/rowlandparks/30.jpg
http://members.cox.net/rowlandparks/31.jpg

[GregP]

Hello R Lenoard,

Welcome to the forum.

I think your post about the zero is very good, but I had not attempted to give a chronological or historical order of nicknames. Only that the family of fighters was variously known as the Zero, Hap, Hamp,and Zeke at different times in the war.

We used our aircraft to their best advantage in combat, and I'm sure the Japanese attempted to do the same. So saying that the Zero was inferior to, say, the Spitifre is a relaitve thing.

The reports all say the Spitfire was better at higher speeds and the Zero was better at lower speeds. So, I assume the Zero pilots attempted to get the Spitfire pilots to slow down and fight while the Spit pilots REALLY didn't want to do that.

Case in point, I have seen combat reports on the Zero where the pilot deliberately rolled slower than possible and turned less sharp than possible to get a Spitfire to attempt to follow him. If the Spit bit the bait and elected to dogfight, the Zero pilot would be on the Spit's tail in a flash. If not, no harm done and the fight continued.

So the "better" fighter was subjective. How fast, how high, and who was in the more favorable position at the start of the attack.

Anyway, thanks for the detailed posting above! Keep it up.

[Michael Monfils]

There is a lot of confusion about superchargers, especially those supplying the engines which powered the various models of the Mitsubishi Zero. The Nakajima Sakae 12 which powered the Zero 21 has a single-stage, single speed supercharger. The Sakae 21 which powered the Zero 32, 22 and 52 is often described as having a two-stage supercharger. I believe this is incorrect. In Robert Mikesh's earlier book on the Zero there is a cutaway drawing of the Sakae 21 engine which shows only one impeller (not two, which you would see in a two-stage supercharger) and the associated gearing which indicates a two-speed device. Therefore, the Zero 32, 22 and 52 had mechanically-driven single-stage, two speed superchargers, NOT two-stage superchargers.

However, in Mr. Mikesh's second book on the Zero, one of the very best on the subject, he contradicts his earlier book and says that the Sakae 21 had a two-stage, two speed supercharger. I believe that Mr. Mikesh was a curator of the Smithsonian Nat’l Air and Space Museum where they have a Zero 52; I wonder if he ever “looked under the hood.” Even Jiro Horikoshi, the designer of the Zero, in his book "The Eagles of Mitsubishi" mentions that a two-stage supercharger improved the Zero 32's performance. My wife is a Japanese translator and we have concluded that this may be a translation error, but who the hell are we to disagree with the designer of the Zero?! Again, I refer to the cutaway drawing (yes it's the Sakae 21, with longer reduction gear housing, but only one impeller).

In the English language as well it seems that the words (or the concepts) of "speed" and "stage" get confused when it comes to the subject of superchargers. The same confusion occurs in articles in magazines such as Wings and Airpower. I have many books on the subject from Japan such as the Maru Mechanic and nowhere in drawings or photos do I see any physical evidence of a second stage in the Sakae 21's supercharger installation. The vast majority of Japanese aviation and modelling websites also come down on the side of a two-speed, not a two-stage supercharger. Authors Rene Francillon, William Green, and test pilot Cpt. Eric Brown also refer to the Sakae 21 as having "only" a two-speed supercharger.

I think it needs to be remembered that two-stage systems are complex and add weight and extra length and require more elaborate induction and cooling arrangements. From that standpoint alone it is easier to believe that the Zero 32, 22 and 52 had efficient two-speed units rather than two-stage superchargers. Has anyone in this forum actually seen a real genuine Sakae 21 engine installation up close and can they shed any light on this dilemma?

[GregP]

I have seen the engine up close, but did not take particular notice of the supercharger. Also, the engine I saw was fully assembled, with nothing "cutaway", so it would have been impossible to note the number of impellers in any case.

Japanese radial engines in the Zero were very reliable, easy-starting, and smooth-running. In every way, they were exscellent powerplants. They simply did not have enough power for a heavier plane, and were not well suited to power-enhancement development. They were 1000 to 1200 HP engines until late in the war, and I don;t believe the A6M series ever got more than around 1500 HP in its entire service life ... and THAT model was near the end.

The props were also very good and serviceable units.

[BuzzLightyear]

Six months before the war began Mitsubishi started testing a new version of the Reisen - The A6M3, powered by a 1,130 hp Sakae 21 14 cylinder radial equipped with a 2 speed supercharger instead of a single speed unit as used on the earlier Sakae 12.

Japanese Aircraft Of The Pacific War, Rene Francillon, page 366-367

The photo of the Nakajima Sakae 21 on page 524 of the same book does not depict a collector section or rear section of sufficient length to house two impellors.