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Mitsubishi A7M Reppu (Hurricane) 'Sam'

Mitsubishi A7M Reppu (Hurricane) 'Sam'


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Mitsubishi A7M Reppu (Hurricane) ‘Sam’

The Mitsubishi A7M Reppu (Hurricane) 'Sam' was designed to be the replacement for the A6M Zero, but despite a great deal of effort over several years only one production aircraft was completed before the end of the Second World War.

Although the A6M Zero had more than lived up to expectations, even as it was being introduced the Japanese Navy began to think about a replacement. A 16-Shi specification for a new fighter was issued, but Mitsubishi struggled to find the staff to work on the project, and the specification was withdrawn.

Work resumed in 1942, this time to a 17-Shi specification issued on 6 July 1942. This was designed to make sure that the aircraft wouldn't be obsolete by the time it was introduced, probably no earlier than 1945. The new aircraft was thus required to have a top speed of 397mph at 19,685ft, to be able to climb to that height in 6 minutes, to have an endurance of 2hr 30mins at 288mph, a diving speed of 518mph, to be armed with two 20mm cannon and two 13.2mm machine guns. It also had to be as manoeuvrable as the A6M3 Model 32.

Jiro Horikoshi, the main Mitsubishi designer, believed that in order to achieve this impressive performance the aircraft would have to use the new Mitsubishi MK9A or MK9B 18 cylinder radial engine, itself still under development in 1942. The Navy disagreed, and ordered Mitsubishi to use the NK9K Homare engine, perhaps aware of the dangers of relying on an untested engine.

The first prototype, designated as the A7M1, was not ready for its maiden flight until 6 May 1944. It was a fairly typical radial engined fighter of the period, with a cut down fuselage and domed cockpit canopy, giving a good view in every direction. The wings had a flat central section, with dihedral on the outer panels. The wings were very large compared to the A6M5, with a span of 45ft 11 3/16in and a total area of 332.173sq ft. Tests with the prototype proved that the basic design was sound, with good stability and manoeuvrability, but the Homare engine was even more disappointing than Jiro Horikoshi had feared, and the aircraft fell 50mph short of its top speed while its climb rate was nearly twice as slow as required. On 30 July 1944 Mitsubishi were ordered to stop work on the next third to sixth prototypes until a more suitable engine could be found.

Just as Jiro Horikoshi had believed two years earlier that engine turned out to be the Mitsubishi MK9A. The sixth A7M1 prototype was re-engined to become the first of seven A7M2 prototypes and development aircraft. The re-engined prototype made its maiden flight on 13 October, and this time the aircraft was a success. It was ordered into production as the Navy Carrier Fighter Reppu Model 22, with production to be split between Nagoya and Osaka while the engines were built at the Daiko engine factory.

From now on nature and the Americans conspired against the A7M. A massive earthquake hit the Nagoya area, causing many delays. The B-29s bombed the Daiko engine factory, massively reducing the supply of MK9A engines. The first, third and fifth prototypes were also destroyed by American bombing and the second prototype crashed. Only three prototypes were still intact at the end of the war, and only one production aircraft had been completed.

Variants

A7M1

The first two prototypes, with the underpowered Nakajima Homare engine.

A7M2

The planned production version, armed with either two 13.2mm machine guns and two 20mm cannon or four 20mm cannon.

A7M3

A version to be armed with six wing-mounted 20mm cannon and a mechanically drive three-speed supercharger, designed in case the more radical A7M3-J failed. The first prototype was expected to be completed in December 1945.

A7M3-J

The A7M3-J was to have been a land based interceptor version of the A7M. Work on it began early in 1944, with an emphasis on increasing the rate of climb and performance at high altitude. The A7M3-J was to be armed with four wing mounted 30mm cannon and two obliquely mounted 30mm cannon carried in the rear fuselage. Both the fuselage and wings needed major modifications to carry these larger guns. The aircraft was to be powered by a turbo-supercharged engine and was expected to reach 403mph at 32,810ft. A mock-up was completed early in 1945, but the first prototype wasn't expected until October 1945.

Specification (A7M2)
Engine: Mitsubishi MK9A eighteen cylinder air-cooled radial engine
Power: 2,200hp at take off, 2,070hp at 3,280ft, 1,800hp at 19,685ft
Crew: 1
Wing span: 45ft 11 3/16in
Length: 36ft 1 1/16in
Height: 14ft 0 1/2in
Empty Weight: 7,112lb
Loaded Weight: 10,406lb
Max Speed: 390mph at 21,655ft
Cruising Speed: 259mph at 13,125ft
Service Ceiling: 35,760ft
Endurance: 2.5 hours at cruising speed plus 30 minutes combat
Armament: Either two 20mm cannon and two 13.2mm machine guns or four 20mm cannon, all wing mounted
Bomb-load: Two 551lb bombs or two 77 gallon drop tanks


Mitsubishi A7M Reppu (Hurricane) 'Sam' - History


The A7M Reppu (translation: "Hurricane") was designed to be the successor to the Mitsubishi A6M Reisen as a carrier-based fighter for the Japanese Navy, but it never went into service. Specifications were issued in 1940, but Mitsubishi only completed nine prototypes and one production model before the war ended. One of the many reasons for the delay was a disagreement over the engine to be used. When the first prototype took to the air in May of 1944, it failed to reach the required level of performance because of the engine. A different engine was installed, and in October of 1944 the new version fulfilled all of the specifications, and production was authorized. However, in December the factory that was to build the engines was seriously damaged in an earthquake and then further damaged by B-29 air raids. Most of the prototypes were also destroyed. Although the aircraft never became operational, the Allies assigned it the codename of "Sam".

Mitsubishi A7M2 Reppu



Additional information on this aircraft can be found at Wikipedia
HERE .

For a very nice scale color drawing of this aircraft, see here .

Additional color schemes for this aircraft can be found here.

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Contents

Towards the end of 1940, the Imperial Japanese Navy asked Mitsubishi to start design on a 16-Shi carrier-based fighter, which would be the successor to the carrier-based Zero. At that time, however, there were no viable high-output, compact engines to use for a new fighter. In addition, Jiro Horikoshi's team was preoccupied with addressing early production issues with the A6M2b as well as starting development on the A6M3 and the 14-Shi interceptor (which would later become the Mitsubishi J2M Raiden, a land-based interceptor built to counter high-altitude bombers). As a result, work on the Zero successor was halted in January 1941.

In April 1942, the development of the A6M3 and the 14-Shi interceptor was complete, and the Japanese Navy once again tasked Mitsubishi and Horikoshi's team with designing a new Zero successor to become the Navy Experimental 17-shi Ko (A) Type Carrier Fighter Reppu. In July 1942 the Navy issued specifications for the fighter: it had to fly faster than 345 kn (639 km/h 397 mph) above 6,000 m (20,000 ft), climb to 6,000 m (20,000 ft) in less than 6 minutes, be armed with two 20 mm cannon and two 13 mm (0.51 in) machine guns, and retain the maneuverability of the A6M3.

As before, one of the main hurdles was engine selection. To meet the specifications the engine would need to produce at least 1,491 kW (1,999 hp), which narrowed choices down to Nakajima's NK9 (Ha-45) under development (later becoming Homare), or Mitsubishi's MK9 (Ha-43), which was also still being developed. Both engines were based on 14-cylinder (Nakajima Sakae and Mitsubishi Kinsei, respectively) engines converted to 18-cylinder powerplants. The early NK9 had less output but was already approved by the Navy for use on the Yokosuka P1Y Ginga, while the larger MK9 promised more horsepower.

With the larger, more powerful engine, wing loading became an issue. The Navy requested at most 150 kg/m², but wanted 130 kg/m² which complicated design considerations further. With the NK9 it could achieve 150 kg/m², but with the less power it wouldn't meet the specifications for maximum speed. With the MK9 the engineers concluded it could fulfill the requirements however, production of the MK9 was delayed compared to the NK9, and the Japanese Navy instructed Mitsubishi to use the NK9.

Work on the 17-Shi was further delayed by factories prioritizing A6M and Mitsubishi G4M production as well as further work on A6M variants and addressing Raiden issues. As a result, the 17-Shi, which became the A7M1, officially flew for the first time on 6 May 1944, four years after development started. The aircraft demonstrated excellent handling and maneuverability, but was underpowered as Mitsubishi engineers feared, and with a top speed similar to the A6M5 Zero. Ώ] It was a disappointment, and the Navy ordered development to stop on 30 July 1944, but Mitsubishi obtained permission for development to continue using the Ha-43 engine, flying with the completed Ha-43 on 13 October 1944. The A7M2 now achieved a top speed of 628 km/h (339 kn 390 mph), while climb and other areas of performance surpassed the Zero, leading the Navy to change its mind and adopt the craft. ΐ] The A7M2 was also equipped with automatic combat flaps, used earlier on the Kawanishi N1K-J, significantly improving maneuverability.

On June 1945, ace pilot Saburo Sakai was ordered to Nagoya to test the airplane. He declared it to be the fastest fighter he had ever seen, able to surpass anything on the air, Japanese or American. He claimed it could fly in circles, while ascending, around a Hellcat or a Mustang, and that engineers stated it could fight at up to 12,000 meters. Α]

While it was hoped that the A7M would replace the A6M, production was disrupted by an earthquake in December 1944 in the Nagoya region, and by Allied bombing, with only eight aircraft completed by the end of the war. The type never saw combat.


Mitsubishi A7M Reppu (Hurricane) 'Sam' - History

The Mitsubishi A7M Reppu was originally conceived in 1942 to eventually replace the A6M Zero carrier-fighter in the Imperial Japanese Navy. Bigger, more powerful and much faster than the Zero, the “Reppu” (hurricane) was a victim of delays, on the part of both engine development and the Japanese Navy’s decision-making and aircraft procurement process. In the end, they never saw combat, and only seven or so were built, in two versions.

The A7M1 was the original version with the Nakajima Homare radial engine of approximately 1900 hp fitted. Oil cooler and intake ducts were all buried in the cowl with a cooling fan connected to the propeller hub, like the FW 190 and J2M Raiden, among others. It made for a beautifully clean airframe, but difficulties with the engine and overall system caused a shift to the A7M2 configuration, using the Mitsubishi Ha-43 Mk 9D radial of over 2000 hp, and used conventional external cowl ducting. This latter engine was the same type fitted to the Kyushu J7W1 “Shinden” experimental canard interceptor.

The A7M2’s more conventional layout worked much better, and the large aircraft (bigger span and length than an F6F Hellcat) achieved 390 mph in testing with excellent manouverability. A7M2s also had the horizontal stabilizers/elevators squared-off at the tips, and more vertical fin chord.

But it was too late, Japan’s industry was all but nonexistent, and when U.S. occupation forces found the incomplete examples in ravaged factories, the aircraft was given the allied code-name “Sam”. If the war had dragged on, the Reppu may have been a competitive fighter.

Fine Molds released both versions of the A7M in 1/48 about eight years ago, and they are beauties. They have all the correct differences between the two types, and have all the qualities of Hasegawa kits. Great decals, too… but the instructions are only in Japanese!

The orange aircraft represents the first A7M1 prototype. The other is the A7M2. Notice all the subtle differences between the two, especially cowls and tailplanes. I have always been fascinated by this aircraft, one that makes me ask “what if?” questions. I’m glad that Fine Molds did these, and did such a great job on them.

Definitely recommended for any enthusiast of Japanese aircraft. The two kits are still available, and I believe still in production.


World War II Database


ww2dbase The A7M Reppu ("Strong Gale") were designed as the successor to the A6M Zero aircraft. The design work began in Apr 1942 when Mitsubishi engineer Jiro Horikoshi and his team had completed with previous projects. In Jul 1942, the Japanese Navy issued specific requests for this aircraft, already designated Navy Experimental 17-shi Ko Type Carrier Fighter, which demanded a top speed of 639 kilometers per hour, ceiling of 6,000 meters, being able to climb to 6,000 meters in 6 minutes, having two 20-millimeter cannon and two 13-millimeter machine guns, and keeping the maneuverability of the A6M3 Zero fighters. While Horikoshi's team was able to locate an engine that would be able to handle the performance being demanded, the company's responsibility to build G4M bombers and A6M fighters meant that the building of prototype A7M fighters was delayed significantly. The first prototype took flight on 6 May 1944, and was found to be underpowered. War demands led to the Navy's request for Mitsubishi to stop development on the A7M, but the company was able to secure permission to continue with the condition that no resources would be allocated to develop new engines. Instead, A7M development continued using the existing Ha-43 engine. The first prototype with the Ha-43 engine took flight on 13 Oct 1944, achieving a top speed of 628 kilometers per hour and showing better handling than the A6M Zero predecessors. Production began shortly after, but an earthquake in the Nagoya region of Japan on top of the ever waning resources due to the Allied naval blockade meant only eight aircraft would be build before the end of the war. A7M fighters would see no combat.

ww2dbase The Allied codename for the A7M Reppu fighters was "Sam".

ww2dbase Source: Wikipedia

Last Major Revision: Dec 2011

6 May 1944 The A7M1 Reppu fighter took its first flight.
30 Jul 1944 The Japanese Navy ordered Mitsubishi to stop development of the A7M fighter design Mitsubishi was able to secure permission to continue given that the company was to use existing engines rather than develop new ones.
13 Oct 1944 The A7M2 Reppu fighter, equipped with the Ha-43 engine, took its first flight.

A7M2

MachineryOne Mitsubishi Ha-43 engine rated at 2,200hp
Armament2x20mm Type 99 cannon, 2x13.2mm Type 3 machine guns
Crew1
Span14.00 m
Length10.99 m
Height4.28 m
Wing Area30.86 m²
Weight, Empty3,226 kg
Weight, Loaded4,720 kg
Speed, Maximum630 km/h
Speed, Cruising417 km/h
Service Ceiling10,900 m
Range, Normal1,200 km

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Visitor Submitted Comments

1. walter says:
22 Sep 2012 11:02:50 AM

muy interesante.Desearía recibir informaciòn periodicamente sobre el tema. Agradecido.

2. M. Parker says:
10 Aug 2015 07:19:10 PM

What happened to the A7M aircraft. I heard 2 survive? Where are they??

3. Anonymous says:
9 Jan 2016 12:12:12 AM

The A7M3 version has the W/L and P/L of a Ki 100 with more speed and firepower and turn ability with auto combat flaps like the N1K. The best part is the boost for better altitude performance and 2,250 hp.

The A7M3-J Kai is perhaps overkill with the 6x30mm punch at the expense of climb (2 more minutes to about 33,000'). W/L and P/L would be heavier, in the
Ki 61-II ballpark. So it would be more like a US fighter but slower (50 hp less than the A7M3). An F6F might outfly it but not the lighter A7M3 with 6x20mm cannons. Both Reppus 3s are close to 400 mph in estimated speed, but better than the A7M2 at altitude or even the Kawasakis.

The cannons are all high velocity, even the 30mm.
The 20mm might be the faster 750 rpm version produced since May 1945. That's better than the US Hispano M2 20mm. And equal to the RAF Hispano Mk V. The US M3 was still prone to jam but not quite as much as the M2 perhaps.

Anyway, the firepower was most formidable. Handy for tackling B-29s. 4 wing-mounted 30mm cannons and twin dorsal 30mm cannons are superlative for interception.

With the added delay for the A7M3-J Kai, due to the longer nose and general strenthening for the heavier weight of those 30mm weapons, I wonder if the priority should have been to expedite the more than adequate 20mm armed A7M3 first to get it into action in quantity. The Kai was perhaps overkill and a distraction that kept the Reppu from getting in the ring at all. Mitsubishi couldn't afford to lose another 6 months.

4. Anonymous says:
18 Apr 2016 07:31:57 PM

What if?
The rocket motor of the J8M was in the tail to boost speed La-7R style?
That should close the speed gap with Allied fighters.
When Russia attacked at the end of the war, imagine if those two had a dogfight? La7R vs A7M2R!!
Just a thought.

Or just replace the MK9 powerplant with a Karyu jet engine and move the cockpit forward some more! Then pack Navy 20 and 30mm cannons in the nose with ammo on the cg. The US couldn't match those guns.
Of course it's jet engine might be less reliable than the slow 390 mph standard MK9 prop Reppu, but the Lockheed P-80 was coming! It would have made things more interesting than a fighter project that spanned the entire war in developement and never really broke 400 mph and never saw action. All because the 340 mph Zero A6M7 had priority. Go figure! Of couse this Zero worked well as a kamikaze plane or night fighter. The Reppu should have replaced all Zeros years before that, parallel to the Army Ki 84 rival!
Time was wasted between 1940 and 42 and again later, and again after that for the A7M3-J redesign.
This made the Army brass look like geniuses compared to the Navy brass. The Ki 84 was kicking butt in 1943, while the prolific A6M5 Zero was losing the war and wasting resources!

The Navy had only one MK9 factory for the Reppu!!
This engine was so reliable, it was slated to power the Ki 84 too. So why not more factories? When that sole factory was put out of action, more delays followed for the Reppu, predictably.
Jiro Horikoshi was used to frustration with the Navy brass on top of everything else, long before this.

As soon as the A7M2 passed the test flight, it should have been rolling off of all Zero production lines and Ki 43 lines too, with many, many sources for the MK9 engines.

How many late-war Japanese fighters had reliable engines? The Reppu did! So get this fighter out the door and onto all carriers and on all fronts in 1944 already!! As is, it's way better than the obsolete Oscar and Zero. If the diehard aces complain, give them a Reppu! It turned 360 in 12 seconds!! It did 390 mph! It had better handling than the A6M5! It could out-dive it handily. And it could intercept B-29 too. It could pack 4x20mm cannons. What Oscar did that?

Then, in 1945 ramp up the A7M3 with the higher altitude MK9S and 6x20mm cannons in the wings!! 7,000 of these running loose might also give the Russians pause as well as the B-29s.

Then in 1946 field the 30mm cannon packing, super high altitude long-nosed A7M3-J/A8M interceptor version if relevant.

5. ron says:
27 Apr 2016 12:57:03 PM

The Type 99-II type 5 was equal to the RAF Hispano Mk V 20mm cannon and certainly superior to the US version of the Hispano, even the post-war M3 version.

No other Japanese fighter gun equaled it.
750 rpm
1,000m firing range.
128 gpr and 9.9g HE!
750 mps M/V
Up to 250 rpg That's 20 seconds of firing time.
The A6M3 had 6 of these in the wings.
It deserved not to be delayed for the sake of the Zero.

6. ron boren says:
16 May 2016 02:36:19 PM

The shock of the Midway dissaster was still ringing in the ears of the IJN. They were terrified. Their decissions showed it. In the case of the A6M5 they went against the more powerful engine, and relented with the A6M8 2 years later. Again, with the Reppu A7M1 they ordered converting it to take the less powerful NK9 because it was readily acceptable without delay. Then, after the underpowered result disappointed, they lost time letting the engineers have their way about 6 months later with the 2,200 hp MK9. It was a successful A7M2 flight test. It would have been better instead of the A7M1 when there was time to produce prior to the December earquake and B-29 bomb damage brought down the curtain on the Reppu. Japan didn't have time for the IJN to lock horns with the design team.

7. ron boren says:
19 May 2016 03:13:28 PM

Reppu has better handling and turn than A6M5 Zero. Check.
It has speed of Ki 84. Check.
It has climb and dive of J2M3. Check.
It has altitude performance of J2M5. Check.
It has 4x20mm cannons. Check.
It has reliability. Check.
It has top priority. Nope!

All visitor submitted comments are opinions of those making the submissions and do not reflect views of WW2DB.


Micubiši A7M2 22 Reppú [Sam]

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When translation of Reppu is a Japanese Japanese-English dictionary, it is "violent wind", but English reference book is Hurricane? --saburny 03:30, 11 November 2006 (UTC)

Hurricane is a mistrancelation. "Strong gale" is better. I310342 22:49, 26 November 2006 (UTC)


Gaijin Please-the Mitsubishi A7M3 Reppū and the A7M3-J Reppū-Kai

The Mitsubishi A7M Reppu was designed as the successor to the Imperial Japanese Navy’s A6M Zero, with development beginning in 1942. Performance objectives were to achieve superior speed, climb, diving, and armament over the Zero, as well as better maneuverability. To compensate for the weight increase, its overall proportions were significantly greater than its predecessor. The A7M’s allied code-name was “Sam“.

In July of 1942, the Imperial Japanese Navy issued a series of objectives for the replacement of the Zero, a 16-Shi carrier-based fighter. The objectives were: being able to fly faster than 345 knots (639 km/h 397 mph) above 6,000 meters (20,000 ft), reach 6,000 meters (20,000 ft) in less than 6 minutes, be armed with two 20 mm cannons, two 13 mm (0.51 in) machine guns and retain the maneuverability of the A6M3. Jiro Horikoshi's engineers struggled to meet these demands, especially with selecting a proper engine. Because of this, when the A7M1 flew on May 6, 1944, it showed a disappointing top speed, no better than that of the A6M5 Zero's (despite an otherwise excellent display of maneuverability and handling). Thus, the IJN ordered a full stop on the project by July 30, 1944.

Mitsubishi obtained permission to continue on the project, using a newly-developed engine, the Ha-43. This was far more powerful than the engine on the A7M1, and the A7M2 achieved a top speed of 628 km/h (339 kn/390 mph). The following are further developments of the project.

A7M3 Reppū: Proposed land-based fighter version powered by a 2,250 hp (1,680 kW) mechanically driven three-speed supercharged Mitsubishi Ha-43 engine, with a maximum speed of 642 km/h (398 mph). The armament consisted of six 20 mm (.80 in) Type 99 cannons in the wings. Prototype under construction but was incomplete prior to end of war.

A7M3-J Reppū-Kai: Proposed land-based interceptor version powered by a 2,200 hp (1,600 kW) turbo-supercharged Mitsubishi Ha-43 engine including an inter-cooler, with a maximum speed of 648 km/h (402 mph). The armament consisted of six 30 mm (1.20 in) Type 5 cannons, four wing-mounted & two oblique fuselage-mounted. Full-scale mock-up built, but no prototype.


WI:Mitsubishi A7M Reppu 1943-44

Once you start adding in more guns,Armor and self sealing tanks, you needed a lot more engine to drag that larger wing (needed for extra weight of gear)around at speed.

Japanese had real trouble developing 1800HP+ radials

The Japanese had trouble developing and mass producing and sustaining in the field anything more than they already did because of inherent limitations in their industrial base (much like the Italians).

For all of the myth in popular history that the Zero was this uber-advanced design, it in fact highlights all of the limitations in Japan's ability to design and mass produce advanced (by 1942 standards) combat aircraft.

Disclaimer - all credit to the folks at Mitsubishi for doing what the did with the limited resources they had but do what they did they had to make some very difficult compromises.

Zheng He

Just Leo

Saphroneth

173rd LRRP

Zheng He

Kind of like the classic response to the question:

"Why did you lose the game?"

"Well, because the other team scored more points than we did."

Saphroneth

Zoomar

Agreed. Given the losses suffered, I can't really blame the designers for trying to increase survivalability as best they could, but it did hurt already marginal performance for marginal armor. I just like to correct the common misperception that Militarist Japan never used any plane armor or self-sealing fuel tanks out of some philosophical objection.

You raise a good point about armament, too. It is interesting to think about, when so much of the IJN air arm was based on striking hard as fast, on a strong first blow. A pair of 12.7mm machine guns might have been adequate in 1939, but not much later. The 7.7mm machine guns in the A6M were likely always all but useless, which is a problem when your cannon carry so few rounds. It is even more amazing when you remember that the Ki-43 was supposed to carry two 12.7mm guns, but due to supply shortages, many early war models actually carried only one, with the second replaced with a 7.7mm model. When I think about the poor bastards in Burma, assigned to try to take down B-24s in a Ki-43.

Late war fighters were usually designed with four 20mm cannon, if they were a new design, but by then it was too late.


Rank III

Very soon after the A6M2 mod.11 started entering the production phase in end-1940 the Japanese Navy already requested Mitsubishi to design a direct successor of the A6M, which would be dubbed as the 16-shi. But at the time, there was no viable high-output as calculations by Jiro Horikoshi's development team who designed the A6M, suggested that to have a climb rate and top speed needed by the Navy they would have to use a minimum of 2,000hp engine. This proved to be an exceptional challenge as the two engines which theoretically could develop this power were still under development. Besides that, Horikoshi's team were still occupied with engineering the A6M2 mod.21 and designing the 14-shi interceptor (which would later be known in service as the J2M), for these reasons Mitsubishi put the plans for a Zero-successor on hold in January of 1941.

Development

In April of 1942, development of the A6M3 mod.32 and J2M2 mod.11 were finished and the navy once again tasked Mitsubishi and Horikoshi's team to design a new zero successor dubbed this time as the 17-shi Ko. The Navy requirements for the 17-shi were as followed:

As before, one of the main hurdles was engine selection. To meet the specifications, the engine would need to produce at least 2,000 hp (1,500 kW), which narrowed choices down to Nakajima's NK9 "Homare" (Ha-45) or Mitsubishi's MK9 (Ha-43) both engines still being under development. These engines were based on 14-cylinder (Nakajima NK1 "Sakae" (Ha-25) and Mitsubishi MK8 "Kinsei" (Ha-33), respectively) engines converted to 18-cylinder powerplants. The early NK9 had less output but was already approved by the Navy for use on the Yokosuka P1Y Ginga, while the larger MK9 promised more horsepower.

With the larger, more powerful engine compared to the A6M's, wing loading became an issue. The Navy requested at most 150 kg/m² but wanted 130 kg/m², which complicated design considerations further. With the NK9 it could achieve 150 kg/m2, but with less power, it would not meet the specifications for maximum speed. With the MK9's 2,200 hp (1,600 kW), the engineers concluded it could fulfil the requirements however, production of the MK9 was delayed compared to the NK9, and the Japanese Navy instructed Mitsubishi to use the NK9's 2,000 hp (1,500 kW).

Work on the 17-Shi was further delayed by factories prioritizing A6M and G4M production as well as further work on A6M variants and addressing J2M issues. As a result, the 17-Shi, which became the A7M1, officially flew for the first time on 6 May 1944, four years after development started. The aircraft demonstrated excellent handling and manoeuvrability but was underpowered as Mitsubishi engineers feared and with a top speed similar to the A6M5 mod.52. It was a disappointment, and the Navy ordered development to stop on 30 July 1944.

But previously, Mitsubishi obtained permission for development to continue using the Ha-43 engine, Saburo Sakai test-flighted with Ha-43 on 13 October 1944 and after the flight test, Sakai was extremely impressed with the A7M2. The A7M2 now achieved a top speed of 339 kn while climb and other areas of performance surpassed the Zero, leading the Navy to change its mind and adopt the ordered cancel. The A7M2 was also equipped with automatic combat flaps, used earlier on the Kawanishi N1K-J, significantly improving manoeuvrability.

Planned variants

Next to the prototype A7M1 and production ready A7M2 there were 2 direct variants of the A7M:

Proposed land-based fighter version was powered by a 2,250 hp (1,680 kW) mechanically driven three-speed supercharged Mitsubishi Ha-43 with a maximum speed of 642 km/h . Armament consistent of six 20 mm Type 99 Model 2 in the wings.

Proposed land-based interceptor version powered by a 2,200 hp (1,600 kW) turbo-supercharged Mitsubishi Ha-43 engine including an inter-cooler, with a maximum speed of 648 km/h . The armament consisted of six 30 mm Type 5 cannons, four wing-mounted & two oblique fuselage-mounted.

Usage

In late 1944 an earthquake strained the manufacturing of the A7M2 causing only 8 to be built. In early 1945, Allied bombings of Japans mainland lead to the destruction of the A7M plans. This ceased the development of the A7M2, and the plane would never see combat. Only a single A7M2 would be built in 1945 due to allied bombings.


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