Interesting, but Forgotten Warplanes of World War II

Hindsight is a glorious thing.

From the safe distance of several decades, it is blindingly obvious that many of the aircraft thrown into combat during the Second World War were worse than useless and should never have been built (Messerschmitt Komet, Blackburn Roc, Breda 88, we're looking at you).

Rarer and more obscure today are the outstanding aircraft that never made it. Despite their brilliance, due to politics, bad timing, official indifference or just bad luck, these potentially superb aircraft never got the chance to shine: 

10: Martin-Baker MB3

Despite never entering service, the MB3 has been indirectly responsible for saving 7700 lives (and counting). Friends and partners, James Martin and Valentine Baker had been designing unconventional monoplanes since the early 1930s. From the start, they believed that aircraft should be as simple as possible. 

The MB3 was their response to a wartime RAF requirement for a fast, heavily armed, fighter. Formidably furnished with six 20-mm cannon, it was also designed for ease of maintenance and manufacture (unlike the Spitfire).

Tests flights, which started on 31 August 1942, proved it was both highly manoeuvrable and easy to fly. Its top speed of 415 mph was a touch faster than the contemporary Spitfire Mk VIII. The main load-bearing structures were constructed of heavy tubing (or built-up spars) so it would have been able to survive greater battle damage than an equivalent stressed skin aircraft.

It was not to be, however: on a test flight on 12 September 1942, the engine failed soon after take-off, and the MB3 crashed in a field and killed its pilot, company co-founder Captain Valentine Baker. Though the team had been investigating the idea of escape seats since 1934, it was Baker’s death that motivated Martin to focus exclusively on ejection seats.

9: Martin-Baker MB5

Despite the crash of the MB3 in 1942 due to the failure of its Napier Sabre engine, it was apparent that the plane was worthy of further development. Martin-Baker proposed a Rolls-Royce Griffon-powered version, the MB4, but a more thorough redesign was favoured by the Air Ministry and the MB5 was the result.

A fair contender for the best British piston-engined fighter ever flown, the MB5 was well armed with four cannon, very fast, and as easy to maintain as its predecessor. Flight trials proved it to be truly exceptional, with a top speed of 460 mph (740 km/h), brisk acceleration and docile handling.

Its cockpit layout set a gold standard that RAF testers recommended should be followed by all piston-engined fighters. The only thing the MB5 lacked was good timing; it first flew two weeks before the Allied invasion of Normandy. Appearing at the birth of the jet age, with readily available Spitfires and Tempests, there was never a particularly compelling case for producing the slightly better MB5.

 There is also a suggestion that the MB5 never received a production order because on the occasion it was being demonstrated to assorted dignitaries, including Winston Churchill, the engine failed. If this is true, it must rank as the most pathetic reason for non-procurement of an outstanding aircraft in aviation history.

8: Miles M.20

The M.20 was a thoroughly sensible design, cleverly engineered to be capable of excellent performance yet being easy to produce with minimal delay at its nation’s time of greatest need. As it turned out, its nation’s need was never quite great enough for the M.20 to go into production.

 Flying for the first time a mere sixty-five days after being commissioned by the Air Ministry, the M.20’s structure used wood throughout to minimise the aircraft’s use of potentially scarce aluminium, and the whole nose, airscrew and Merlin engine were conveniently supplied as a single, all-in-one ‘power egg’ unit, as it was already in production for the Bristol Beaufighter II.

To maintain simplicity, the M.20 dispensed with a hydraulic system, and while this meant that the landing gear wasn’t retractable, the weight saved allowed for a large internal fuel capacity and the unusually heavy armament of twelve machine guns with twice as much ammunition as either the Hurricane or the Spitfire.

Tests revealed that the M.20 was slower than the Spitfire but faster than the Hurricane, and its operating range was roughly double that of either. It also sported the first clear-view bubble canopy to be fitted to a military aircraft.

7: Douglas XB-42 Mixmaster

The remarkable XB-42 was in many ways the most advanced piston-engined warplane ever flown (though the Republic XF-12 Rainbow might be a rival for this title). The XB-42 was as fast as the British Mosquito B.XVI but could carry twice the maximum bomb-load, furthermore the Mosquito B.XVI  had no defensive weaponry whereas the Mixmaster had four 0.50-inch machine guns in two remotely-controlled turrets.  

A variety of offensive gun options were considered, including sixteen .50-cals or two 37-mm cannon. Meanwhile, the updated XB-42A prototype, with its improved engines and Westinghouse 19XB-2A turbojets, had a top speed of 488 mph (785 km/h) and a maximum range of 4750 miles (7644 km).

The Mixmaster was superb, but at the risk of being too positive, it should also be noted that it suffered terrible adverse yaw. Additionally, while the aforementioned Mosquito could operate from grass airfields, the XB-42 needed miles of flat smooth concrete due to its limited ground clearance.

By the time the war ended, the US Army Air Force could afford to wait for the inevitable arrival of the jet bomber, but the sleek, rather weird, Mixmaster offers a tantalising insight into how military aircraft may have evolved if the piston age had lasted a little longer.

6: Dornier Do 335

When faced with similar design goals and timing to the Grumman Tigercat, Dornier took a radically different approach with their unique Do 335. To minimize the frontal surface area, drawing on earlier experience with the Do 18 and the P.59 (a 1937 patent for a tractor-pusher bomber), the ‘335 adopted the rather weird ‘push-pull’ configuration, with both engines mounted in the fuselage.

The forward engine is in the traditional location. The aft engine is mounted in the middle of the fuselage (for better weight distribution) and is connected to an aft pusher propeller with a driveshaft. The resulting surface area is only slightly higher than a comparable single-engine fighter.

A pair of Daimler Benz DB-603 engines, each producing 1800 hp, allowed for a maximum weight a little higher than a traditional fighter, armed with a 30-mm cannon firing through the propeller hub and a pair of 20-mm cannons in the cowling.

The aircraft could carry a lot of fuel and provided a combat range 30% higher than the Fw 190 or Me 109. The aircraft was too late to see combat in World War Two, and only 37 were built. Of these, a few reached conversion units for a short duration and the type did not see combat.

5: Focke-Wulf Fw 187

An exceptionally fast aircraft, the handsome Fw 187  suffered as a result of the Luftwaffe having a very precisely defined concept of what they required from a twin engine aircraft. It is often regarded as having been a direct competitor to the Messerschmitt Bf 110 but the truth is rather less straightforward.

Kurt Tank designed the Falke as a long-range single-seat escort fighter. It was both smaller and lighter than the Bf 110 and was broadly equivalent to the British Westland Whirlwind. The new twin was designed as a private venture and was undoubtedly, a fine aircraft.

6: Focke-Wulf Fw 187

Germany at the time was painfully short of aero-engines, and instead of the DB 600s he had wanted Tank had to make do with the Jumo 210 which was some 200 hp lower powered. Despite this impediment, the Fw 187 recorded a speed of 325 mph in 1937, some 50 mph faster than the Bf 109B, yet possessed twice the range and had slightly superior climb and dive performance.

The sixth prototype was fitted with the desired DB 600 engines and clocked 395 mph in 1939 (then the fastest speed attained by a German fighter). Whilst it is unlikely it would have changed the course of the war, its better performance than the Bf 110 and better range than the Bf 109 would have been useful during the Battle of Britain. It was cancelled due to engine unavailability, inexplicable official indifference, and other aircraft being perceived as good enough.

4: Polikarpov I-185

A direct descendant of Polikarpov’s revolutionary I-16, the I-185 Nikolai Polikarpov’s I-185 was an excellent aircraft stymied by engine trouble, politics, timing, and outright bad luck. Uniquely amongst this selection, it was also sent to the front and actually flew on operations. 

It should have been the finest fighter the USSR fielded during the Great Patriotic war with 2000 hp on tap, slightly smaller than a Grumman Bearcat but weighing 1900 lb less in normal loaded condition, faster than the contemporary Bf 109F at all altitudes up to 20,000 feet, its handling was immeasurably better and it was recommended for immediate production in the Autumn of 1942.

However, by this time everything had been thrown into chaos by the German invasion. The Soviets needed lots of fighters immediately and didn’t have the luxury of waiting for promising prototypes. Unpopular but available fighters were produced in their thousands and gradual evolution rather than completely new types ultimately yielded the two major Soviet fighter series from Lavochkin and Yakovlev.

In November 1942, the three prototypes were sent to the front to be evaluated under operational conditions. The report was unambiguously favourable: “The I-185 outclasses both Soviet and foreign aircraft in level speed. It performs aerobatic manoeuvres easily, rapidly and vigorously. The I-185 is the best current fighter from the point of control simplicity, speed, manoeuvrability (especially in climb), armament and survivability.”

3: Beechcraft XA-38 Grizzly

Founded in 1932, Beechcraft is still going strong, and its Bonanza has been in continuous production longer than any other aircraft: 74 years at the time of writing,  and around 17,000 have so far been built. Rather less successful was Beechcraft’s sole foray into the world of combat aircraft: the Grizzly, a mere two examples of which were built.

But what an aircraft: its primary armament was a humongous 75-mm gun in the nose, the same as fitted to the Sherman tank. As a dedicated ground attack aircraft, its enormous gun was intended for use against hardened targets such as pillboxes and tanks. Two forward-firing 50-calibre machine guns were used to aim the main weapon and tests had proved the armament particularly effective.

Most dedicated ground attack aircraft of the Second World War were relatively slow and vulnerable to fighter attack but the Grizzly was fast: despite being the size of a medium bomber it was capable of 376 mph at 5000 feet, 10 mph faster than a P-47D at the same altitude.

It was also extremely well defended with both dorsal and ventral turrets each mounting two 50-calibre machine guns to deal with any fighter aircraft it might not be able to outrun, which were few indeed at the low altitudes it was designed for. Unfortunately for Beechcraft the Grizzly’s fantastic performance was largely a result of its Wright R-3350 ‘Duplex-Cyclone’ engines, the same engines used by the B-29 Superfortress, and there weren’t enough R-3350s to go round, the B-29 had priority and the XA-38 was consigned to history.

2: Grumman F5F ‘Skyrocket’

As it originally appeared in April 1940 the Skyrocket was a radical-looking aircraft, a snub-nosed fuselage ending abruptly on the leading edge of the wing and twin tails to match the two engines. Its distinctive aesthetic was undoubtedly the reason it became a comic book star and its performance matched its futuristic looks, particularly in rate of climb, which may have led to the ‘Skyrocket’ name.

In a 1941 fly-off against a bevy of contemporary operational and experimental US fighters (Curtiss P-40 Warhawk, Bell P-39 Airacobra, Bell XFL Airabonita, Vought XF4U Corsair, Grumman F4F Wildcat, and Brewster F2A Buffalo) with a Spitfire and Hurricane thrown in to give a cosmopolitan international flavour, the F5F came out on top.

Lieutenant Commander Crommelin later stated “I remember testing the XF5F against the XF4U on climb to the 10,000 foot level. I pulled away from the Corsair so fast I thought he was having engine trouble. The F5F was a carrier pilot’s dream, as opposite rotating propellers eliminated all torque…The analysis of all the data definitely favored the F5F, and the Spitfire came in a distant second.”

So why did this wonder aircraft never enter service? Two engines meant added complexity and a more demanding supply chain, which is a serious business when operating from a carrier. Furthermore, the Skyrocket was afflicted with multiple small problems. Ultimately the portly F5F performed its most important work flying as a development aircraft for the impressive F7F Tigercat which entered service in August 1945.

1: Heinkel He 100

Initially, all seemed bright for the He 100.  The prototypes were very fast and their low-drag airframes also made for an impressive range. The only really negative point was the cooling system which was a very aerodynamic but highly complex evaporative cooling system that required 22 separate electric pumps, each with its own warning light in the cockpit, to circulate the coolant around the airframe.

The cooling system was constantly unreliable so it was ditched for the pre-production aircraft and replaced with a conventional radiator. In this form, the Heinkel He 100  was probably the best fighter in the world and ready for a Luftwaffe order, which Heinkel was so confident of getting that it tooled up and started production of its own accord. But of course, the order never came.