Airspeed AS.10 Oxford, part two, Asian users

The Airspeed AS.10 Oxford was a British twin-engined monoplane developed and manufactured by Airspeed Ltd. It was initially conceived as a trainer variant of the Airspeed AS.6 Envoy until it quickly developed into a design of its own and saw wide use as a trainer before, during and after World War 2. It was exported to many Asian countries:

• Union of Burma: At least 15 Oxfords were supplied to the Union of Burma Air force just after its independence in 1948. Some of them were modified to carry pod-mounted forward-firing machine guns and rocket projectiles to be used in anti-insurgency operations.
• India: When India became independent in December 1947 nine Oxfords were transferred to the Royal Indian Air Force which later became Indian Air Force. 
• Israel: Three Oxfords (some sources claim they were four) were in inventory of the, back then, newly founded Central Flying School of the Israeli Defence Force Air Force. They were used, together with the Airspeed Consul, for twin-engined flight training in the early 1950s.
• Imperial State of Iran: Three Oxfords were delivered to the Imperial State of Iran Air Force back in 1938. 
• Ceylon: Three former RAF Oxfords were delivered to the Ceylon Air Force in 1953 (some sources claim it was in 1951). 
• Turkey: The Turkish Air Force was supplied in 1943 with 50 Oxford Mk.I. They were complemented with 20 more in 1946-1947. They served as the Turkish Air Force main twin-engined trainer until the early 1950s when they were replaced by the Beechcraft AT-11 Kansan. The remaining Oxfords were scrapped.

Sources:

1. https://en.wikipedia.org/wiki/Airspeed_Oxford#Other_users

2. http://www.aeroflight.co.uk/waf/aa-mideast/israel/af/types/train1.htm#consul

Airspeed AS.10 Oxford, part one, Australian & New Zealand Users

The Airspeed AS.10 Oxford was a British twin-engined monoplane aircraft that was developed and manufactured by Airspeed Ltd.It was initially considered as just a trainer version of the AS.6 Envoy, however it quickly became a design of its own as it saw use as aircrew trainer in many countries of the British Commonwealth. Its main use was navigation, radio-operating, bombing and gunnery roles through the World War 2.
In this post we're focusing on the use that Australia and New Zealand gave to the Oxford.

• Australia: In Australia, the imported Oxfords retained their original RAF serials, in spite of having been assigned the prefix A25 (just like it happened with the Fairey Battles). The first Oxford was imported into Australia on 28th October 1940 and the last one on 20th March 1944, making a total of 391 machines having served with the Royal Australian Air Force (RAAF). These aircraft were both of the Mk.I and Mk.II variants which, the first ones, had a turret (designed by Armstrong-Whitworth) for gunnery training, and the second ones hadn't. They were mainly employed for pilot and navigation training.
  The Oxford was commonly known by the trainees as the "Ox-Box" and they were employed at the Empire Air Training Schools for instruction in flying, navigation, gunnery, radio and bombing. Additionally, Mk.II versions operated with Nos. 1, 2 and 5 Communication Units, in the communications role.
  In the years after the World War II, the Oxford was retained by the RAAF in the trainer and communications role until 1953 when they finally withdrew from service. Together with the Avro Anson, the Airspeed Oxford was the main trainer in service with the RAAF for more than 10 years.
• New Zealand: Between 1938 and 1954 (some sources claim it was until 1952) the Royal New Zealand Air Force (RNZAF) operated a total of 299 Oxfords. This was more than nearly other type of aircraft then in service with the RNZAF. They were ordered in 1937, making New Zealand one of the first nations to operate the type. An initial batch of five aircraft was delivered with the fifth aircraft being intended to be use as a survey airplane. They were shipped disassembled to New Zealand and were assembled at RNZAF Hobsonville during late 1938. The RNZAF ordered six more machines and later, 30 more of them. When the Commonwealth Air Training Plan was created, further 140 were allocated, which included the last batch of 30 ordered. They were used by many Air Training Schools (ATS) in New Zealand in the trainer role.

Sources:

1. https://en.wikipedia.org/wiki/Airspeed_Oxford

2. https://www.airforcemuseum.co.nz/aircraft/airspeed-oxford/

3. https://www.airforce.gov.au/sites/default/files/minisite/static/7522/RAAFmuseum/research/aircraft/series2/A25.htm

Mitsubishi A6M 'Zero', part six, late variants

This post is a direct continuation of the previous one where we listed some variants of the Mitsubishi A6M 'Zero':

• A6M5 Type 0 Model 52: This variant, which is regarded as the most effective one, was developed to make wings shorter, in order to increase speed and dispense with the folding wing mechanism. Additionally, ailerons, aileron trim tabs and flaps were also revised. The early machines were manufactured by Mitsubishi but production was soon overtook by Nakajima and a total of 747 aircraft were made.
  The prototype was completed in June 1943 by modifying an A6M3 and flew for the first time in August that same year.
  The A6M5 featured a new exhaust system which required cowl flaps to be "notched" and heat shields just aft of the stacks. Apparently, early machines differed from the rest of the series in having the same exhaust system as the A6M3 Model 22, however, from a batch onwards, the machines were standardised and they even received carbon dioxide fire extinguishers in the wing fuel tanks. Later on an improved radio was added which required the antenna mast to be slightly shortened. The new arrangement of the exhaust system expelled the heat just under the wing, causing burns on the forward edge of the landing gear doors and heated the tires. Shorter bottom stacks were installed to prevent this. The A6M5 had a maximum speed of 565 km/h (351 mph) at 6.000 m (20.000 ft) high and could reach that altitude in 7.01 minutes.
  Many sub-variants were manufactured:
• A6M5a Model 52: This variant had its Type 99-2 Mark 3 cannon replaced with a Type 99-2 Mark 4. As those weapons had different ammo feeding system, the bulge created underwing for the ammunition drum was deleted and the ejection port for spent cartridges was moved. Thicker wing skinning was added too to allow higher diving speeds. A total of 391 machines of this sub-variant were manufactured by both Mitsubishi and Nakajima from July 1943 until March 1944.
• A6M5b Model 52: This featured heavier armament as its 7.7 mm (0.303 in) Type 97 machine guns located in the right forward fuselage, was replaced by a 13.2 mm Type 3 Browning-derived machine gun. This larger gun required an enlarged opening creating a distinctive asymmetric appearance to the top of the cowling and a revised gas outlet near the windscreen, where a plate of armoured glass 45 mm (1.8 in) thick was also fitted. Additionally each wing cannon received a fairing at the leading wing edge. A large propeller spinner was also fitted which suggest a new propeller too. The ventral drop tank was also changed as now it had fins and was suspended on a slanted pipe. A total of 470 aircraft were completed from April 1944 (when the prototype was completed) until October 1944.
• A6M5c Model 52: This variant had one 13.2 mm (0.51 in) Type 3 machine gun added in each wing outboard of the cannon and the 7.7 mm machine gun on the left side of the cowl was deleted. Four racks for rockets or small bombs were installed at the outboard of the 13 mm cannon in each wing. It seems that this variant may had been powered by the Nakajima Sakae 31 radial engine. A thicker (55 mm/2.2 in) armoured glass panel was installed at the headrest and an 8 mm (0.31 in) thick plate of armour was placed behind the seat. The mounting of the central 300 L (79 US Gal) drop tank changed to a four-post design. Wing skin was thickened further. The first aircraft of this variant was completed in September 1944 and only 93 machines were completed before the end of the war. Given its extra weight, this variant was used to intercept B-29 bombers and special attack (kamikaze) missions.
• A6M5-S: In order to intercept the B-29 bombers and other night-flying aircraft, the 21st Naval Aviation Workshop at Omura, converted some few (7 machines in total) Model 52 into night-fighters. They were armed with one 20 mm Type 99 cannon placed behind the pilot which was aimed upwards copying the Luftwaffe's Schräge Musik arrangement. However, as they lacked radar, their effectiveness was very limited.
• A6M5-K: Seven machines of the Model 52 were rebuilt into two-seat trainers in February 1945 at the 21st Naval Aviation Workshop in Omura. It was estimated that Hitachi would start mass-producing them, but this didn't happen.
  Additionally, some both A6M3 and A6M5 were converted to fighter-bombers by mounting a bomb rack and a 250 kg (550 lb) bomb instead of the central fuel tank.
• A6M6 Type 0 Model 53: This variant was developed to be powered by the new Nakajima Sakae 31a engine, which featured water-methanol engine boost and self-sealing fuel tanks. Preliminary tests showed its performance to be unsatisfactory as the extra engine power didn't materialise and the fuel injection system proved to be unreliable. Apparently a single prototype was produced in December 1944 but the end of the war prevented further development. 
• A6M7 Type 0 Model 62/63: This was the last variant to see service. It was designed as an answer to a requirement made by the Imperial Japanese Navy Air Service (IJNAS) for a dedicated attack/dive bomber that could operate from smaller aircraft carriers or, according to other sources, replace the obsolete Aichi D3A. This variant had considerable design changes like reinforced vertical stabiliser, a special bomb rack, provision for two 350 L (92 US Gal) drop tanks and the fixed bomb/rocket wing stoppers on the underside of the wings. It was also powered by a new powerplant. A Nakajima Sakae 31 radial engine which yielded 1.130 hp on take-off. Overall it had a general armament layout similar to the A6M5c with the exception of the central bomb rack which was capable of carrying 250 kg or 500 kg bombs.
  An unknown number of aircraft of this variant were made in May 1945 by Mitsubishi and most of them were used in Kamikaze attacks. 
• A6M8 Type Model 64: This variant was similar to the A6M6 but with the Nakajima Sakae engine (which was now out of production) replaced by the Mitsubishi Kinsei 62 radial engine which delivered 1.560 hp of power. This resulted in a modified cowling and nose. Carburettor intake was longer, a long duct like the one of the Nakajima B6N was added and a large spinner, like the one present at the Yokosuka D4Y was mounted. It was armed with two 13.2 mm (0.52 in) Type 3 machine guns and two 20 mm (0.80 in) cannons in the wings. Additionally it was modified to carry two 150 L (40 US Gal) drop tanks on either wing in order to allow the mounting of a 250 Kg bomb under the fuselage. Two prototypes were completed in April 1945 (some sources claim the first one was completed in November 1944 and the second one in June 1945) but the chaotic situation of the Japanese industry during this period of the war prevented the mass-production of this variant of which more than 6.300 machines were expected to be manufactured. Eventually only the two prototypes were completed and flown.

Sources:

1. https://en.wikipedia.org/wiki/Mitsubishi_A6M_Zero

2. https://www.valka.cz/Micubisi-A6M7-63-Reisen-Zeke-Zero-t1281

3. https://www.valka.cz/Micubisi-A6M8-64-Reisen-Zeke-Zero-t27679

4. https://www.valka.cz/Micubisi-A6M6c-53c-Reisen-Zeke-Zero-t35110

5. https://www.valka.cz/Micubisi-A6M5-K-Zeke-Zero-t49190

6. https://www.valka.cz/Micubisi-A6M5a-52A-Reisen-Zeke-Zero-t86308

7. https://www.valka.cz/Micubisi-A6M5b-52B-Reisen-Zeke-Zero-t1280

8. https://www.valka.cz/Micubisi-A6M5c-52C-Reisen-Zeke-Zero-t27682

9. https://www.valka.cz/Micubisi-A6M5d-S-52D-Reisen-Zeke-Zero-t35347

10. Salamander Books - The Complete Book of Fighters

11. AJ Press - Monografie Lotnicze 7 - Mitsubishi A6M Zero (translated)

12. Signal Squadron - Aircraft in Action 59 - Mitsubishi A6M Zero in Action

Mitsubishi A6M 'Zero', part five, mid-life variants

This post is a direct continuation from the previous one where we listed every variant of the Mitsubishi A6M 'Zero':

• A6M3 Type 0 Model 32: With the introduction in 1941 of the Nakajima Sakae engine, which was equipped with a two-speed supercharger, for better altitude performance and yielded 1.130 hp of power, a prototype of a Zero fitted with this engine was made and flew for the first time on 15th July 1941.
  This new engine was slightly heavier and longer because of the superchargers. This extra weight changed the center of gravity and moved it too forward on the airframe. To fix this, the engine mountings were cut back by 185 mm (7.3 in) in order to move the engine toward the cockpit. This created the side effect of reducing the size of the main fuselage fuel tank, which was placed between the engine and the cockpit, from 518 L (137 US Gal) to 470 L (120 US Gal). The cowling was revised to make cowl flaps larger, the oil cooler was revised and the carburettor's air intake was moved to the upper half of the cowling.
  Wings were also redesigned to reduce in order to reduce span, eliminate folding wingtips and square off the tips. The inboard edge of the aileron was placed outward by one rib and wing fuel tanks were enlarged to 420 L (110 US Gal). The two 20 mm wing cannons which were present in previous versions, were upgraded to the Type 99 Mark II, which required a bulge in the sheet metal of the wing below each cannon. The wings also included larger ammunition boxes increasing the amount of ammo to 100 rounds per cannon.
  The Sakae 21 engine increased maximum speed by just 11 km/h (6.8 mph) when compared to the previous A6M2 Model 21 and sacrificed nearly 1.000 km (620 mi) of range. However, the Imperial Japanese Navy Air Service (IJNAS) accepted the type and it entered into production in April 1942.
  Thanks to its shorter wing, it had better rolling capabilities and, considering its reduced drag, the diving speed was increased to 670 km/h (420 mph). However, turning and range, which were the strong points of the A6M2 Model 21, suffered due to the smaller ailerons, decreased lift and greater fuel consumption. The shorter range proved to be a serious handicap during the Solomon Islands Campaign as the Zeroes stationed in Rabaul had to travel nearly to the their maximum range to reach Guadalcanal and return. Therefore the A6M3 was declared as unsuitable for that campaign and was used for shorter range offensive and interception missions.
  When the A6M3 appeared the Americans codenamed it 'Hap'. However that codename didn't live for long time as USAAF Commander Henry "Hap" Arnold protested and forced the change of the codename to "Hamp". Later, it was realized that it was a new variant of the Zero, which already had the codename of 'Zeke' and was accordingly re-codenamed as 'Zeke 32'.
  This variant wasn't flown by many IJNAS units and only 343 units were manufactured by Mitsubishi in Nagoya and Nakajima in Koizumi, both in Japan. It was manufactured from April to December 1942. 
• A6M3 Type 0 Model 22: To correct the flaws of the previous Model 32, a new version with folding tips and redesigned wing was put into service with the IJNAS. The fuel tanks were moved to the outer wings, fuel lines for a 330 L (87 US Gal) drop tank were installed under each wing and the internal fuel capacity was increased to 570 L (150 US Gal). These changes made the model to regain the range numbers seen on the previous A6M2 Model 21.
  This model, however, was put into service before being accepted formally by the Navy and, in December 1942 it was de-facto introduced. Around 560 machines of this type were manufactured from December 1942 until late 1943 by both Mitsubishi and Nakajima.
  Both models 32 and 22 were powered by the Nakajima Sakae.
• A6M4 Type 0 Model 41/42: This designation is not an official Mitsubishi's one. However, in some captured documents from a Naval Air Technical Arsenal dated 1st October 1942, there are some references to a "cross-section of an A6M4 intercooler" which was being designed. Some researched believe that this designation was given to two prototypes fitted with an experimental turbo-supercharger Sakae engine designed for high altitude performance. Mitsubishi's involvement in the project was quite limited or even nul, as the unmodified Sakae engine was exclusively made by Nakajima. The design and testing was made by First Air Naval (Technical) Arsenal in Yokosuka. There's one photo of this variant showing a turbo unit mounted in the forward left fuselage, however we couldn't find it.
  The lack of suitable alloys for manufacture of a turbo-supercharger and its related ducting caused numerous ruptures, resulted in fires and poor performance. Therefore any further development of a turbo-supercharged A6M was cancelled and discontinued. As the IJNAS didn't accept any A6M4 into service and didn't bestow models 41/42 formally. However, it seems that the Arsenal did use the designation of A6M4.

Sources:

1. https://en.wikipedia.org/wiki/Mitsubishi_A6M_Zero#Variants

2. https://www.valka.cz/Micubisi-A6M-Reisen-Zeke-Zero-t15680 (translated)

3. AJ-Press - Monografie Lotnicze 7 - Mitsubishi A-6M Zero (translated)

4.Salamander Books - The Complete Book of fighters

5. Signal Squadron - Aircraft In action 59 - Mitsubishi A6M Zero in Action

Mitsubishi A6M 'Zero', part four, early variants part one

As the 'Zero' was the backbone of the Imperial Japanese Navy Air Service's (IJNAS) fighter force, many variants were manufactured. Some of those are the following:

• A6M1 Type 0 12-shi: The first two A6M prototypes were completed in March 1939. They were powered by a 780 hp Mitsubishi Zusei 13 radial engine driving a two-bladed propeller. They flew for the first time on 1st April and passed testing in a remarkably short period of time. In September that year it had already been accepted by the IJNAS for testing as the 'A6M1 Type 0 Carrier Fighter' with the only change of switching to a three-bladed propeller to fix a vibration problem.
  Just two aircraft were made at Mitsubishi's factory in Nagoya, Japan.
• A6M2a Type 0 Model 11: As the IJNAS was testing the first two prototypes, they suggested the third prototype which was still under fabrication, to be fitted with the 940 hp Nakajima Sakae 12 radial engine. As Mitsubishi had their own engine of this kind under manufacturing as the Mitsubishi Kinsei, and considering the rivalry between Nakajima and Mitsubishi, they were reluctant to use it. Anyway, when the first A6M2 was completed in January 1940, thanks to the Sakae's extra power, it pushed the performance of the Zero well past beyond its original specifications.
  As the reports of this new variant were so promising, the IJNAS had a first batch of 15 machines built and shipped to China before they had completed testing. They arrived in Manchuria in July 1940 and saw combat for the first time over the province of Chungking in August. There, they showed their absolute superiority over the Soviet-built Polikarpov I-16 and I-153 that were a problem for the previous A5M. In a single encounter, a formation of 13 Zeroes shot down 27 I-15s and I-16s in less than three minutes without a single loss for themselves. After listening to those reports, the IJNAS ordered the manufacturing of the A6M2 as the A6M2a Type 0 Carrier Figher Model 11. Some reports of the Zero's performance were filtered to US officials but they were dismissed by most of them who thought it was impossible for the Japanese to build such an aircraft.
  A total of 64 machines were manufactured at Mitsubishi's factory in Nagoya between May and November 1940.
• A6M2b Type 0 Model 21: After the 64th aircraft of the previous model was built, the design was changed to allow folding wingtips to be introduced in order to improve carrier effectiveness. This resulting model, called 'A6M2b Type 0 Carrier Fighter Model 21' became one of the most produced fighters during the early part of the World War 2. It was also fitted with a 520 L (140 US Gal) wing tank which improved its range even further. Production lines were switched towards the Model 21 and, in total, 740 machines were completed by Mitsubishi at Nagoya and 800 of them by Nakajima in Koizumi, Japan, making it a total of 1540 machines manufactured since November 1940 and November 1941 for Nakajima's ones. Two further sub-variants were built: The Nakajima A6M2-N (which will be the subject of its own post) and the A6M2-K.
• A6M2-K: This variant was a two-seat trainer conversion. A total of 508 machines were completed as the A6M2 was being replaced in frontline service by the A6M3. An unknown number of them were fitted with towing equipment and some of them were used in kamikaze attacks. A total of 508 machines were completed in a production period ranging from November 1943 until August 1945.
  They were manufactured by the 21st Naval Aviation Workshop (where it was also designed and 236 of them were completed) at the city of Omura, Japan and the remaining 272 of them were completed by Hitachi at Tachikawa, Japan from May 1944 until August 1945. Something similar was made with the more advanced A6M5 version, but just like the A6M2-N, we will write about it later.
  Apparently there was a makeshift courier two-seater aircraft. At least one machine was modified to make it two-seater as the personal aircraft of a top Japanese Commander in the South Pacific region in 1944. As we could find just one black & white photo of this aircraft, the drawing should be considered as semi-speculative.

Sources:

1. https://en.wikipedia.org/wiki/Mitsubishi_A6M_Zero

2. https://www.valka.cz/topic/view/32999/Micubisi-A6M1 (translated)

3. https://www.valka.cz/topic/view/116760/Micubisi-A6M2-11 (translated)

4. https://www.valka.cz/topic/view/1277/Micubisi-A6M2-21 (translated)

5. https://www.valka.cz/topic/view/27351/Micubisi-A6M2-K (translated)

6. http://www.j-aircraft.com/a6mresearch/zerotrnr.htm

7. AJ-Press - Monografie Lotnicze 7 - Mitsubishi A-6M Zero (translated)

8. Salamander Books - The Complete Book of fighters

9. Signal Squadron - Aircraft In action 59 - Mitsubishi A6M Zero in Action

Mitsubishi A6M 'Zero', part three

The first 'Zeroes' to enter service were 15 A6M2 with the 12th Rengo Kokutai in July 1940. Shortly later, on 13th September they scored their first air-to-air victory when 13 A6M2 attacked 27 Soviet-built Polikarpov I-15s and I-16s belonging to the Chinese Nationalist Air Force, shooting down every fighter without a single Japanese casualty. When they were redeployed one year later, they had shot down at least 99 Chinese aircraft, with some sources claiming 266 losses.
By December 1941, at the time of the attack on Pearl Harbor, there were up to 521 Zeroes active in the Pacific, 328 of them in first line units. The A6M2 Model 21 was the main type the Americans faced during the first stages of the conflict. It was a carrier-borne version with a very long range (2.600 km/1.600 milles) thanks to which they could range much further away from its carrier than expected, appearing over distant battlefronts and giving Allied officers the impression that there were several times as many Zeroes as actually were.
The Zero quickly gained its fearsome reputation, thanks to a combination of excellent manoeuvrability and firepower and could easily battle any Allied fighter opposition in 1941 and early 1942. It proved a serious opponent even for the British Supermarine Spitfire as British and Commonwealth pilots were trained in fighter tactics that were good against German and Italian fighters, but turned to be suicidal against the acrobatic Zeroes. It wasn't as fast as the Spitfire but the Zero could out-turn the Spitfire easily, sustain a climb at a step angle and remain in the air three times longer than the Spitfire.
New tactics to counter the Zero were soon developed by Allied pilots as the traditional turning dogfights were lethal. It was discovered that it was better to swoop down from above in a high-speed pass, firing quick bursts and quickly climb back to an altitude. As the Zero lacked armour a short burst from heavy machine-guns or cannons was enough to shot down its fragile fuselage. These tactics were often employed by the Grumman F-4F Wildcat fighters during the Guadalcanal campaign, through high-altitude ambush, which was possible thanks to a network of Coastwatchers and radar. Such tactics were also used in the China-Burma-India (CBI) Theatre by the American Volunteer Group "Flying Tigers" against both the Zero and another Imperial Japanese Army's aircraft which had similar flying characteristics like the Nakajima Ki-27 and Nakajima Ki-43.
Another important manoeuvre developed by Lt.Cdr. John S. Thach, was the so-called "Thach Wave". In this manoeuvre, two fighters would fly at about 60 m (200 ft) apart. If a Zero latched onto the tail of one of them, the two aircraft would turn toward each other. This way, if the Zero followed his original target through the turn, he would come to a position to be fired by the target's wingman. This tactic was widely used during the Battle of Midway and later during the Battle of Solomon Islands.
Many veteran Japanese pilots were lost in combat resulting in a notable loss of quality, which became a pivotal factor in Allied victories. Unexpected losses of Japanese pilots at the Battle of Midway and the Battle of Coral Sea, dealt a blow to the Imperial Japanese Navy Air Service from which it never fully recovered.
Later in the war, when the Lockheed P-38 Lightning, armed with four 0.5 in machine guns and one 20 mm autocannon, the Grumman F6F Hellcat and the Vought F4U Corsair were introduced in the Pacific Theatre in 1942 and 1943, as each of these two fighters was armed with six 0.5 in machine guns each, the Zero, with its light-powered engine and lighter-armament, was pressed to remain competitive. During this later time, the only positive factor of the Zero was that, in the hands of a competitive pilots, it could out-turn any of them easily and it still was a deadly machine.
Given the problems with aviation engines, in 1945 it was still being manufactured with over 10.000 machines of every variant manufactured by Mitsubishi, Nakajima and Hitachi.

Sources:
1. https://en.wikipedia.org/wiki/Mitsubishi_A6M_Zero
2. Signal Squadron - Aircraft in Action 59 - Mitsubishi A6M Zero in Action
3. https://www.valka.cz/Micubisi-A6M-Reisen-Zeke-Zero-t15680
4. Salamander Books - The Complete Book of Fighters

Mitsubishi A6M 'Zero', part two

The Mitsubishi A5M entered service in early 1937 and the Imperial Japanese Navy (IJN) was already looking for its replacement. On 5th October 1937 they issued a specification for a "12-shi Carrier-based fighter" and sent it both to Mitsubishi and Nakajima. Both companies started with preliminary design works while awaited the specification to be more precise.
Taking the experiences of the A5M in China the IJN sent out updated requirements in October requiring a speed of 270kn (310 mph/500 km/h) at 4.000 m (13.000 ft) high and a climb to 3.000 m (9.800 ft) in 9.5 minutes. Equipped with drop tanks, they required an endurance of two hours at normal power, or six to eight hours at economical cruising speed. Required armament consisted on two 20 mm cannons, two 7,7 mm machine guns and two 60 kg (130 lb) bombs. Every aircraft was also going to be equipped with a complete radio set, together with a radio-direction finder for long range flights. Manoeuvrability was required to be at least equal to that of the A5M and the wingspan had to be less than 12 m (39 ft) to allow the fighter to operate from aircraft carriers.
Nakajima's design team considered the requirements impossible to achieve and pulled out from the competition in January. On the other hand, Mitsubishi's chief engineer, Jiro Horikoshi considered that the requirements could be met but only if the aircraft was made as light as possible. Therefore, every possible weight-saving measure was incorporated into the design. I fact, most of the aircraft was built in a new top-secret material called 'extra super duraluminium' which was developed in 1936 by Sumitomo metal industries. This material was lighter, stronger and more ductile than other alloys used at the time, but it was also more prone to corrosion making it brittle. This defect was countered with an anti-corrosion coating applied after fabrication. This design had no armour protection provided for the pilot, engine or other critical points and self-sealing fuel tanks, which were starting to be popular at the time, were not provided. Those features made the A6M more manoeuvrable, lighter and the longest-ranged single-engined fighter of the World War II, making the fighter capable of searching for an enemy, hundreds of kilometres away, bringing it into battle and then returning into its base or aircraft carrier. However, given its lightness it was also very prone to catch fire and explode when hit by enemy fire.
Given its low-wing cantilever monoplane layout, retractable, wide-set conventional landing gear and enclosed cockpit, the A6M was the most advanced carrier fighter at the time of its introduction. It had a fairly high-lift, low-speed wing with very low wing loading. This, mixed with its light weight, resulted in a very low stalling speed of well below 60 kn (69 mph 110 km/h) which made the main reason for its excellent manoeuvrability, allowing to out-turn every Allied fighter at the time. Early models featured servo-tabs on the aillerons after pilots complained that control forces were too heavy at speeds above 300 km/h (190 mph). They were discontinued on later variants after discovering that the lightened control forces were causing pilots to over stress the wings during vigorous manoeuvres. 
It has been claimed that its design show clear influences from British and American fighters and components exported to Japan in the 1930s, and more in particular to both the Vought V-141 (whose prototype and blueprints were sold to Japan in 1937) and the British Gloster F.5/34.
While the resemblance to the V-141 seems debatable, its obvious that the Japanese took some inspiration from it. However, considering that performances of early models are identical in numbers to those of the Gloster F.5/34, apart from the fact that its dimensions and appearance are also equal and that Gloster had relationship with the Japanese during the Interwar period (Nakajima manufactured the Gloster Gambet under license), it seems that the F.5/34 is the most direct inspiration for the A6M.
Its usually known as the 'Zero' as its Japanese Navy designation was called as 'Type 0 carrier fighter' as it was taken from the last digit of the imperial year 2.600 (1940) when it entered service. It was most commonly called by the pilots as the 'Zero-sen' while the Allied code-name was 'Zeke'.

Sources:
1. https://en.wikipedia.org/wiki/Mitsubishi_A6M_Zero
2. Signal Squadron - Aircraft In action 59 - Mitsubishi A6M Zero in Action
3. https://www.valka.cz/Micubisi-A6M-Reisen-Zeke-Zero-t15680
4. Salamander Books - The Complete Book of Fighters

Mitsubishi A6M 'Zero', part one, foreign users

The Mitsubishi A6M 'Zero' is a Japanese long-range fighter which was manufactured by Mitsubishi Heavy Industries, in Nagoya, Japan. It's considered to have been one of the most capable carrier fighters in the world when it was introduced back in World War II as it had excellent speed ,manoeuvrability and very long range. It was used by many foreign n/ations, albeit every foreign user employed captured exemplars.

• Australia: At the end of the war, a single Zero was given by the TAIU-SWPA (Technical Air Intelligence Unit - South-Western Pacific)  to the No.457 Squadron, Royal Australian Air Force (RAAF) at Clark Field, in Philippines. It was tested by the RAAF.
• Nationalist China: The Republic of China Air Force (ROCAF) operated some captured Zeroes of every variant, A6M2, A6M3 and A6M5 mainly. Most of them were captured after the when war, when the Japanese left China, as most of them belonged to the Japanese 12th, 13th, 14th, 15th and Shanghai Kokutais (Air Groups) which operated from mainland China. They were also part of the Imperial Japanese Air Service's (IJNAS) detachment stationed in Formosa, which were Hao Toko, Takao, Tetshu, Kagi, Toki and Tainan Kokutai. During the last stages of the Chinese Civil War, from 1945 to 1949, the Zeroes were employed by both sides, Communists and Nationalists, but neither of them survived the war or those which did, were scrapped shortly later.
• United Kingdom: Some Zeroes were tested by the ATAIU-SEA (Allied Technical Air Intelligence Unite - South East Asia) after the war. One of them, re-registered as Bi-12 was captured in Malaya and was tested at Tebrau airfield, in Malaya in 1946. However, it seems that most of them  were tested at RAF Seletar, in Singapore.
• Soviet Union: When the USSR took the Sakhalin islands, apparently they captured some Zeroes, of the A6M7 Model 63 variant, which was the last variant to see service. This variant was more focused on ground attack/dive bombing. When it was flown by the Soviet VVS (Soviet Air Force) after the war, it crashed in the second test flight.
• United States of America: During the duration of the conflict the United States captured many exemplars of Zeroes. Those captured during the war, some of them were repainted in US Navy colours and sent to mainland USA to be tested. The ones captured after or during the last stages of the war, were tested by the United States Army Air Force (USAAF), many of them at Clark Field, Philippines. 

Lastly, it seems that there were some reports of A6M2 and A6M5 Zeroes were used as interceptors after the war in 1946-1947 by both the Royal Thai Air Force and the Royal Thai Navy, however, the error seems to be erroneous, as more modern reports indicate that the Zero was never used by Thailand.

Also, it seems that pro-independence Indonesian Guerrillas captured some Zeroes and employed them against Dutch troops in the Indonesian War of Independence from 1945 to 1949. However, even if the reports seems plausible as the Indonesian employed many ex-Japanese aircraft in their National Revolution, we couldn't find any pic of an Indonesian Zero, so we decided not to draw a speculative profile.

Sources:

1. https://en.wikipedia.org/wiki/Mitsubishi_A6M_Zero

2. https://en.wikipedia.org/wiki/List_of_Mitsubishi_A6M_Zero_operators

3. https://captured-wings.wikia.org/wiki/ATAIU-SEA

4. https://web.archive.org/web/20161104191035/http://www.thai-aviation.net/files/Air_Force_Summary.pdf
5. http://www.worldairforces.com/countries/thailand/thl.html

6. https://en.wikipedia.org/wiki/Technical_Air_Intelligence_Unit

7. Signal Squadron - Aircraft In action 59 - Mitsubishi A6M Zero in Action

Mitsubishi Ki-46, part three

The Mitsubishi Ki-46 was introduced by the Imperial Japanese Army Air Force (IJAAF) in Manchukuo and China. A total of seven units were equipped with it. Sometimes, the Imperial Japanese Navy Air Service (IJNAS) also employed the type to perform certain reconnaissance missions over the Northern shores Australia and New Guinea.
The IJAAF used this aircraft in the reconnaissance role in unauthorised missions over British Malaysia during the months prior to the bombardment of Pearl Harbor. Later, during 1942 it was used for high-altitude reconnaissance missions over Burma, Indochina, Thailand and the Indian Ocean. The British Royal Air Force regarded the Ki-46 as an aircraft very difficult to counter, with very few successful interceptions. On 25th September 1944 Flying Officer Wittridge shot down a Ki-46 using a personally modified Supermarine Spitfire Mk.VIII. He had removed two machine guns and the seat armour and polished wing leading edges to gain extra speed. The American Top Ace of the World War II, Richard I Bong, flying a Lockheed P-38 Lightning shot down a Ki-46 over the coast of Papua New Guinea in late 1942.
During the latest stages of the war, in 1944-1945 the Ki-46 was modified as a high altitude interceptor with two 20mm cannons in the nose and one 37mm in an upwards-and-forwards position, copying Luftwaffe's Schräge Musik night fighter guns. These were used to shot down the Boeing B-29 Superfortress over the metropolitan Japanese islands. However, it lacked stability for sustained shooting of the 37mm cannon, had just a thin layer of armour plating, it had no self-sealing fuel tanks and was very slow to climb.
It was also assigned to whole 'Sentai' (Wings/Groups) and 'Chutaicho' (junior operational commands) in the IJAAF during the Pacific War.
Some of them were captured by the Allied, repaired and test flown. It seems that one of them was sent to the Soviet NII VVS (Aerotechnical Institute of the Soviet Air Force) for testing, making it the only Japanese aircraft to be sent to the VVS.

Sources:
1. https://en.wikipedia.org/wiki/Mitsubishi_Ki-46
2. https://www.valka.cz/Micubisi-Ki-46-Sin-Sintei-Dinah-t28814 (translated when needed)
3. Bunrin Do - Famous Airplanes of the World 38 - Mitsubishi Ki-46 (translated)
3a: Translated captions can be found at: http://www.arawasi.jp/Dinahtrans.html

Mitsubishi Ki-46, part two

On 12th December 1937 the Imperial Japanese Army Air Force (IJAAF) issued a specification to Mitsubishi for a long-range strategic reconnaissance aircraft to replace the Mitsubishi Ki-15. The specification demanded an endurance of six hours and enough speed to avoid interception by any existing fighter at the time of development. Otherwise, it didn't constrain the design to a team led by Tomio Kubo, a graduate from the Aeronautical Section of the Faculty of Engineering at Tokyo Imperial University who got graduated in 1931 and whose aesthetics are deeply infused into the resulting design.
The design was a twin-engined, low-winged monoplane with a retractable underwing carriage. It had a small diameter oval-shaped fuselage with room for a crew of two with the pilot and the observer placed in individual cockpits separated by a large fuel tank. Extra fuel tanks were placed in the thin wings both inboard and outboard of the engines, giving a total fuel capacity of 1.490 L (328 Imperial Gallons). It was powered by two Mitsubishi Ha-26 radial engines which, in the first variant, they were rated at 863 hp each and were housed in close fitting cowlings developed by the Aeronautical Research Institute of the Imperial Tokyo University with the aim of reducing drag and improving pilot's field of view.
The first prototype flew in November 1939 from Mitsubishi's factory in Kakamigahara, Gifu, North of Nagoya. After being tested, it proved to be seriously underpowered and was slower than required by the specification as it only reached 540 km/h (336 mph) instead of the specified 600 km/h (373 mph). Regarding other aspects, testings were successful. Considering that the aircraft was still faster than the IJAAF's main fighter, the Nakajima Ki-43 and faster too than the Imperial Japanese Navy Air Service's (IJNAS) Mitsubishi A6M2 Zero (newly introduced into service back then) an order for an initial production was placed by the IJAAF as the Army Type 100 Command Reconnaissance Plane Model 1 (Ki-41-I).
In order to solve performance problems, Mitsubishi replaced the engines with Ha-102 radial ones which were able to yield up to 1.065 hp of power. These engines were basically Ha-26 fitted with two-speed supercharger. On this improved design, fuel capacity was also increased and empty weight was also reduced. It was in flying condition in March 1941 and was commonly known as Ki-46-II. This variant met the speed requirements of the original specification and was therefore ordered in a full-scale production with deliveries starting in July.
At first the Ki-46 was virtually inmune to any fighter interception, however it was soon realised by the IJAAF that improved Allied fighters such as the Supermarine Spitfire the Lockheed P-38 Lightning could contest this immunity, so in July 1942 they instructed Mitsubishi to produce a further improved version as the Ki-46-III. This variant was powered by two fuel-injected Ha-112 radial engines which were able of yielding 1.479 hp of power, it had a redesigned nose with a fuel tank ahead of the pilot and a new canopy, smoothly integrated into the extreme nose of the aircraft eliminating therefore the typical 'step' of the earlier versions. The single defensive machine gun present in earlier versions was also deleted. This new variant flew for the first time in December 1942 and showed significant higher speed 630 km/h (391 mph) at 6.000 m (19.700 ft) high. Thanks to its performance, it proved to be superior to designs made by other rival companies, such as the Tachikawa Ki-70 which didn't enter production.
Trying to achieve even more altitude performance, two prototypes were fitted with exhaust driven turbosupercharged Ha-112-II-Ru engines. These flew for the first time in February 1944.
During its production period ranging from 1941 to 1945, a total of 1.742 exemplars (other sources claim it was 1744) were manufactured. Thirty-four Ki-46-I, 1.093 K-46-II, 613 Ki-46-III and 4 Ki-46-IV all of them at Mitsubishi Heavy Industries, in Nagoya, Japan.

Sources:
1. https://en.wikipedia.org/wiki/Mitsubishi_Ki-46
2. https://www.valka.cz/Micubisi-Ki-46-Sin-Sintei-Dinah-t28814 (translated when needed)
3. Bunrin Do - Famous Airplanes of the World 38 - Mitsubishi Ki-46 (translated)
3a: Translated captions can be found at: http://www.arawasi.jp/Dinahtrans.html

Avro Anson, part Fourteen, British users part three

It was on 6th March 1936 when the Anson entered service with the Royal Air Force (RAF) being the No.48 Squadron the first unit to be equipped with the type. When the type entered service it represented a new level of capability for the service as it could perform not just general reconnaissance roles, as intended but it was also an excellent general-purpose aircraft. When the World War II was waged, there were 824 Ansons in service with the RAF in a total of 26 squadrons. Ten of them assigned to the Coastal Command and the remaining 16 assigned to the Bomber Command.
By 1939 all the squadrons assigned to the Bomber Command that were equipped with the Anson served as operational trainers to prepare bomber crew members for frontline service. Twelve of the squadrons were in the No.6 (Operational Training) Group. Newly trained crews, having previously received individual flying and technical training courses, were first trained as bomber crews in Ansons before they could advance further to the various frontline aircraft types, which, in many occasions, were also in the same squadrons with the Ansons. After training in the frontline aircraft type, crews advanced to the frontline bomber squadrons with those aircraft types (Fairey Battle, Handley Page Hampden, Bristol Blenheim, Vickers Wellington and/or the Armstrong Whitworth Weatley). At the earliest part of the war, the Anson was already being replaced by the American-built Lockheed Hudson in the Coastal Command, one squadron being fully equipped with Hudsons and other one being just partially equipped with both Ansons and Hudsons.
Limited numbers of Ansons continued to serve in operational roles such as coastal patrol and air/sea rescue. Early in the war an Anson scored a probable hit on a German U-boat, though it's unconfirmed. In June 1940 a flight of three Ansons was engaged by nine German Bf.109. Amazingly, before the fight ended, without any Anson lost, they managed to shot down two German machines and damage a third one.
The aircraft's real role, however, was to train pilots for flying multi-engined bombers, such as the Avro Lancaster, the Handley Page Halifax or the Short Stirling. The Anson was also employed to train other crew members of a bomber's crew, like navigators, wireless operators, bomb aimers and air gunners.
During the World War II the British Air Transport Auxiliary (ATA) operated the Anson as their standard taxi aircraft, using the type to ferry pilots to and from aircraft collection points. Remarkably, there was no fatal mechanical failure of an Anson serving with the ATA and was typically very well considered.
After the War, the type was manufactured at Avro's factory in Woodford, Greater Manchester until March 1952 as the type, albeit was still being used by the RAF in the training, light transport and station communications aircraft roles until 28th June 1968. However, those postwar manufactured models were mostly C.19 and T.Mk.20/21 which were light cargo and trainer variants.

Sources:
1. https://en.wikipedia.org/wiki/Avro_Anson
2. https://www.valka.cz/Avro-Anson-t54872 (translated when needed)
3. Hall Park Books - Warpaint 53 - Avro Anson

Avro Anson, part Thirteen, British users part two

The Avro Anson was a twin-engine cantilever low-wing monoplane. It was developed as a general reconnaissance aircraft for which it had many features that made it suitable for that role, just like considerable load-carrying ability and long range. Its structure was relatively simple as it relied on proven methods to make a robust airframe that minimised maintenance requirements. Much of the internal structure was like the one of the Avro 652 airliner from which it was developed. The Anson Mk.I was furnished with a low-mounted one-piece wooden wing which was made of a mixture of plywood and spruce throughout the wingbox and ribs. The fuselage was composed of a welded steel tubing framework which was mainly clad in fabric while the exterior of the nose was clad in magnesium alloy.
The Anson was powered by a pair of Armstrong Siddeley Cheetah IX radial engines which were rated each of them at 350 hp. Each engine had its own duplicated fuel pumps and separate fuel oil tanks which were composed of welded aluminium and were mounted in cradles placed within the wing. The cowlings were designed to have reduced diameter to reduce their negative impact on the external visibility, as it was considered valuable to the type's functions, specially when performing reconnaissance missions. Each of those engines drove a two-bladed Fairey-built metal propellers.
The Anson was equipped with a retractable undercarriage, which, upon the time of its production, wasn't a common feature and it holds the title of being the first Royal Air Force's (RAF) aircraft to enter service with such feature. The main undercarriage retracted into nacelles placed under the engines cowling, but, however, the tailwheel was fixed into position.The main undercarriage was retracted by a hand-operated crank which was placed besides the pilot's seat and it took 144 turns to fully retract it. To avoid this laborious task, early aircraft often performed their short flights with the landing gear extended, which reduced aircraft's cruising speed in about 30 mph (50 km/h).
The initial crew was composed of three, a pilot, a navigator/bomb-aimer and a radio operator/gunner when it was acting in the sea reconnaissance role. From 1938 onwards it was typically manned by a crew of four, which often could be omitted to make room for a passenger.
The defensive armament consisted on a single 0.303 in Vickers machine gun which was fixed within the forward fuselage and was aimed by the pilot. It had another gun turret equipped with a single Lewis K machine gun manufactured by Armstrong Whitworth. Additionally it could carry up to 360 pounds (160 kg) of bombs plus up to 160 pounds (73 kg) smaller bombs externally in the wings. Those Ansons assigned to the training role were equipped with dual controls and, usually, had their turret removed, although some of them, designed specifically for gunnery training were refitted with a Bristol-built turret used on the Bristol Blenheim. The tail fairing on the starboard nacelle contained an inflatable dinghy which was provided with automatic actuators and marine distress beacons.

Sources:
1. https://en.wikipedia.org/wiki/Avro_Anson
2. Hall Park Books - Warpaint 53 - Avro Anson
3. https://www.valka.cz/Avro-Anson-t54872 (translated)

Avro Anson, part Twelve, British users part one

Back in 1933 the British Air Ministry proposed the Royal Air Force (RAF) to acquire a cheap landplane for coastal maritime reconnaissance role, supplementing this way the more capable, albeit more expensive, flying boats. The Air Ministry requested designs from every major aircraft manufacturers to produce an aircraft suitable aircraft to meet this requirement. Avro answered the requirement with the Avro 652A which was a modification of the earlier Avro 652. After submitting the designs, the Air Ministry evaluated them and decided to place orders for single examples of the Avro 652A and the De Havilland DH.89 for evaluation purposes to meet this requirement in late 1934. The evaluation and the selection of the design was expected to take place during May 1935.
On 24th March 1935 the Avro 652A made its maiden flight at Woodford aerodrome, in Greater Manchester and between 11th and 17th May 1935 it competed against the DH.89 by the RAF's Coastal Defence Development Unit at RAF Gosport, in Hampshire. During these trials, the Avro proved to be superior and was selected as the winner of the competition on 25th May. Given its selection, the Air Ministry Specification 18/35 was written around the Avro 652A and shortly later an initial order for 174 aircraft which were given the name "Anson".
On 31st December 1935 the first production Anson rolled out from the factory. It differed from the prototype in having an enlarged horizontal tailplane and reduced elevator span to make stability better. Additionally, whilst the prototype wasn't fitted with flaps, production aircraft could fit their installation from the onset to increase the viable glide angle in order to reduce landing speed. On 6th March 1936 deliveries to the RAF begun. A total of 11.020 Anson were manufactured when the type ceased to be manufactured in 1952, making it the second most manufactured British multi-engined aircraft of the World War 2, only surpassed by the Vickers Wellington.

Sources:
1. https://en.wikipedia.org/wiki/Avro_Anson
2. https://www.valka.cz/Avro-Anson-t54872 (translated)
3. Hall Park Books - Warpaint 53 - Avro Anson