Nachtjagd

Already during the Battle of Britain, RAF Bomber Command had gone on the offensive. Painful and bloody experience earlier in the war had demonstrated that unescorted bombers could operate over enemy territory only at night, and so they did, at first with very limited efficacy but in increasing numbers. For the Luftwaffe this created similar problems as the RAF had earlier in the war. At this time, its ground-based radars were more technologically advanced than the British radars, but the problem of directing a fighter close enough to the enemy bombers to initiate attack had not been solved. The air defence of the Reich now needed a fighter with good handling characteristics for night operations, the endurance to loiter in the battle area and pursue fleeting contacts, heavy armament, and the ability to carry of variety of more or less experimental gear.

Kauz

One option was to convert a light, fast bomber, as the British had done with the Blenheim. The closest German equivalent was the Dornier Do 17, a streamlined twin-engined bomber which had first seen combat during the Spanish Civil War and was at the end of its production run in mid-1940. Do 17Z bombers already operated in the intruder role, with extra fuel cells in the bomb bay and sometimes additional guns fitted in a modified nose. Dornier was instructed to create dedicated nightfighter and intruder versions, which they reportedly did by adopting the nose cone of the Ju 88C-2 to their own aircraft. The new model appeared as the Do 17Z-7 Kauz, with a “solid” nose design carrying one 20-mm cannon (first the MG FF and later the MG-151/20) and three (MG-17) rifle-calibre machine guns, modest enough armament by the standards of the time. Ventral and dorsal installations of MG 15 machine guns were retained. The crew of three was given some extra armour protection, and fuel tankage redesigned and increased. The engines remained 1000 hp Bramo 323P-1 radials, doing little to give the aircraft the required performance: It was also primarily intended, it appears, to operate as a long-range intruder aircraft. An interesting concept tested on one of the only two aircraft completed was an infrared detection device known as Spanner. This combined an infrared searchlight with a viewer in the cockpit, allowing the aircraft, at least in theory, to illuminate targets without being seen. (The device would also be installed on some Bf 110s, with little success.)

Remarkably enough, it was decided to convert an additional nine Do 17Z-3 bombers to the Do 17Z-10 Kauz II configuration, which featured a redesigned nose with an extra machine gun. These aircraft were successful enough to serve until 1943. A Do 17Z made the first successful night interception with radar guidance from the ground, in October 1940. More nightfighter conversions were produced of the Do 215, itself a variant of the Do 17 powered by slightly more powerful Daimler-Benz DB601 V-12 engines. The Do 215B-5 Kauz III nightfighter version of this aircraft thus was faster, at 465 km/h instead of 420 km/h. In August 1941 a Do 215B-5 was equipped with the very first Telefunken FuG 202 Lichtenstein BC airborne radar. Its array of external antennas cannot have helped performance but the radar was effective, reportedly allowing its pilot to shoot down six aircraft before the set broke down. About 20 aircraft were converted to nightfighter configuration and they stayed in service until May 1944, with the addition of a ventral tray with an extra pair of cannon.

	Dornier Do 215B-5	Dornier Do 217N-2
Engines	Daimler-Benz DB601Aa	Daimler-Benz DB603A
Rating	2 x 1100 hp	2 x 1750 hp
Wing Span (m)	18.00	19.00
Length (m)	16.66	18.00
Height (m)	4.97	4.60
Wing Area (m2)	55.0	57.0
Empty Weight (kg)		10,270
Loaded Weight (kg)		13,200
Max. Speed (km/h)	465 km/h at 4,800 m	515 km/h at 6,000 m
Climb
Ceiling (m)	9000
Range (km)	1,800	1,755
Guns, fixed	1 × 20 mm MG FF in nose  4 × 7.92 mm MG 17 in nose 2 × 20 mm MG FF in ventral tray	4 × 20 mm MG 151/20 in nose  4 × 7.92 mm MG 17 in nose
Guns, flexible	2 × 7.92 mm MG 15, ventral and dorsal

The logical successor to the Do 17 and Do 215 was Dornier’s Do 217. It is often dismissed as a derivative of these aircraft but was in fact new design, substantially larger and more powerful, a heavy medium bomber in the class of the American B-26. Although some early production aircraft had DB 601 engines, most production aircraft had more powerful BMW 801 radials or DB 603 in-line engines. The BMW-engined Do E-2 was the first to be converted into an improvised night fighter, the Do 217J, which featured a new “solid” nose with four MG 17 machine guns and four MG FF/M cannon, while retaining its dorsal and ventral MG 131 defensive guns. The J-1 did not have radar, but was equipped as an intruder aircraft with full bombing equipment. The J-2 was a true nightfighter with FuG 202 Lichtenstein BC radar. The Do 217J was not very successful but soldiered on from the spring of 1942 until 1944, with a number being transferred to Italy’s Regia Aeronautica. A similar conversion of the faster DB 603-engined Do 217M entered production in late 1942 as the Do 217N. To increase performance, the Do 217N-1 quickly saw the deletion of defensive armament as the N-1/U-1, a choice that became standard on the N-2 model. But although the Do 217 was a good aircraft for night flying and possessed a decent performance, it lacked the agility and rate of climb to make a good fighter. Most of the 364 fighter versions of the Do 217 ended at operational training units.

Besides their pioneering role in the introduction of radar and the less successful infrared devices, the Do 17 and Do 217 family also featured the first installations of a new armament variation that would become notorious as Schräge Musik (slanted music). Rudolf Schönert is credited with the installation of a upward-firing machine guns in a Do 17Z-10 and later in a Do 217. The idea was not truly successful until late 1942, when twin MG FF cannon, angled 70 degrees up, were installed in the rear cockpit of a Bf 110 of II/NJG5, then commanded by Schönert. Production installations later appeared on all German nightfighter types, including a heavy installation of four MG 151/20 cannon on the Do 217N.

Old Soldier

The development of aircraft such as the Do 17Z-7 in 1940 indicates that the Luftwaffe was not totally neglecting night combat. Nevertheless in the first months of the war the home defence consisted of obsolescent models of the Bf 109. These would perform night interceptions with the guidance of searchlights on the ground, a dubious concept as the little fighter was likely to run out of fuel long before it had managed to stalk a bomber this way. The first dedicated Nachtjagdgeschwader was created on 26 June 1940. While at first these units had both the Bf 110 and the Bf 109 on the strength, it was not long before conversion to the Bf 110 was recognised as the best solution. The twin-engined fighter had the endurance and flight characteristics for safe night operations, good enough performance to intercept bombers, and extra crew members to help look for the enemy, the human eye being at this stage the only detection device carried on these aircraft.

The first Bf 110 units added to the growing night defences of the Reich flew day fighter models with minor modifications, such as flame dampers added to the exhaust and changes to cockpit lighting for night operations. Indeed the first nightfighter units were created by renaming Zerstörer units. A layer of matte black paint initially identified the nightfighter aircraft. The night interception technique relied mostly on the development of better ground radars: The Freya warning radar was combined with two short-range Würzburg radar sets, which allowed a ground intercept officer to plot the location of both the target and the intercepting fighter. Reliance on an accurate but short-range ground radar set did tie the nightfighter to the small sector, named Himmelbett, that could be controlled by the radar stations. The “Kammhuber Line”, named after the commander of the Nightfighter Division, gradually expanded to stretch multiple lines of such stations as a barrier between the German cities and the RAF.

More flexible tactics became possible in February 1942 when the first airborne radars were installed. Development had begun in 1940, but was hampered because until late 1941 the Luftwaffe opposed the installation of drag-inducing external antennas, and at the radar wavelengths then in use, internal antenna arrays performed poorly. Thus it was February 1942 before early production models of the FuG 202 Lichtenstein BC radar were installed. Operating at 490 MHz, this radar set required a complex “mattress” of sixteen pairs of small dipoles antennas on the nose. It had a range of about 4 km and a minimum range of about 175 m, enough to help crews to intercept a target and bring it within sight. The drag penalty was substantial, reducing speed by 40 km/h, and crews were distrustful at first. Telefunken’s Dr. Kümmritz complained that some aircrew resorted to a hacksaw to remove the offending antennas. Over time, the radar proved its value.

The Bf 110F-4 was the first dedicated night fighter model, with a third crew member, FuG 202 radar (not installed on the first production aircraft) and the ability to carry ventral tray with two 30-mm MK 108 cannon. It had a top speed of 500 km/h at 4,500 m, or 40 km/h slower than the Bf 110C-1 despite the installation of more powerful 1350 hp DB 601E engines. The further addition of two Schräge Musik cannon (denoted by the suffix /R8), and a growing collection of electronic devices to help in the interception of the RAF bombers, made the aircraft more effective at the cost of performance and handling.

Some relief was expected from the Bf 110G series, which featured the more powerful DB 605 engine. This proposal was accepted in January 1942 when it was clear that the replacement of the Bf 110 by the Me 210 would have to be delayed. Initial production plans envisaged a G-1 fighter-bomber, G-2 heavy fighter and a G-3 reconnaissance machine; the G-1 was soon cancelled and the first production model was the G-2, which entered service in January of 1943. The nightfighter model became the G-4. Improvements during the production run of the G-series included the replacement of the ventral MG FF cannon by the MG 151/20, the replacement of the defensive MG 15 by the MG 81Z, and on the G-4 series, the introduction of larger tail fins to improve handling. During 1943 the G-series and the F-series were produced in parallel, with both models incorporating the same airframe changes, but F series aircraft built to compensate for the limited supply of DB 605 engines and their initial unreliability. As supply and reliability problems eased late in 1943, also F-4 airframes were completed with the new engines.

As daylight attacks of US bombers intensified during 1943, the G-2 Zerstörer version was found effective against them because of its heavy armament, which various modifications sought to enhance. Experiments with a 37-mm BK 37 cannon in a belly pack, which replaced the ventral 20-mm cannon in the /R1 modification, were not very effective, but the weapon saw some combat against US bombers in 1944. More successful, from the autumn of 1943, was the optional installation of four tubular launchers for the WGr 21 rocket, two under each wing. A barrage of such rockets could disrupt a bomber formation when their 40.8 kg warheads exploded at the preset distance, between 600 and 1200 m. However, the tubular launched induced a lot of drag and each unit weighed 111 kg. Even nightfighters, despite the performance penalty imposed by their extra equipment and the lack of training of their crews for such missions, were deployed to oppose the USAAF bomber raids. But when P-51B Mustang escort fighters appeared over Germany in late 1943, the Bf 110 soon ceased to be a viable daylight interceptor, and the use of nightfighters during daylight was finally understood to be a tactical error that resulted in prohibitively heavy losses.

Hence the G-4 nightfighter model became the most built version of the Bf 110, with a production run of about 1850 aircraft, from January 1943 to early 1945. Increasingly, the age of the design was hard to compensate for. Perhaps nothing indicated this as much as the /R3 modification, which entailed the replacement of the four MG 17 machine guns in the upper nose of the fighter by a pair of 30-mm MK 108 cannon. These weapons were far more destructive than the rifle-calibre machine guns that they replaced, but the installation of short-barrelled cannon in the upper nose of a nightfighter was nevertheless a flawed and unpopular concept. Complaints about the blinding muzzle flash were predictable but flame dampers were still under development at the end of the war. To make it worse, soot was deposited on the windscreen, the blast could damage the radar antennas, and crews complained that the powerful but short-range cannon made the aircraft fly through the debris of the enemy bombers.

From June 1943 onwards, the Bf 110G-4 began to receive the FuG 220 Lichtenstein SN-2 radar, which operated at a different (longer) wavelength than the FuG 202 and was thus more resistant to British countermeasures such as Window, at least initially. FuG 220 came with a simpler, but larger set of dipole antennas on the nose of the aircraft. But the Model A radar had to be combined with a FuG 212 Lichtenstein C-1 radar because its minimal range of 500 m was too long to bring the fighter into visual contact with its target, so a smaller set of four pairs of dipoles appeared in the center of the FuG 220 antennas. Later models of the FuG 220 had a shorter minimal range and allowed the FuG 212 to be removed.

Until late 1944 the Bf 110 was an effective nightfighter. It was a clear example where “size matters”: If the Luftwaffe had chosen the little Fw 187 over the Bf 110 in 1940, it would have had a serious problem in 1943, for the sleek Focke-Wulf fighter would not have been able to carry the extra load for this mission. As it was, even the Bf 110 airframe was reaching its limits with the addition of radar, electronics gear, additional armament packs, and usually external fuel tanks to increase the aircraft’s endurance. But the Luftwaffe had not had much success in its search for an alternative, and it was more luck than planning that gave it a better nightfighter in the final years of the war.

	Bf 110G-2	Bf 110G-4 with FuG 202
Engines	2 × DB 605B-1	2 × DB 605B-1
Rating	1475 hp	1475 hp
Wing Span (m)	16.28	16.28
Length (m)	12.07	12.91
Height (m)	4.16	4.16
Wing Area (m2)	38.37	38.37
Empty Weight (kg)	5959	6088
Loaded Weight (kg)	7788	7917
Max. Speed (km/h)	561 km/h at 5800 m	510 km/h at 5800 m
Climb
Ceiling (m)
Range (km)	900 km, 1300 km with external fuel	880 km, 1270 km with external fuel
Fixed Guns	4 × 7.92 mm MG 17 in nose 2 × 20 mm MG 151/20 in nose 2 × 20 mm MG 151/20 in ventral pack	4 × 7.92 mm MG 17 in nose 2 × 20 mm MG 151/20 in nose 2 × 20 mm MG 151/20 in ventral pack
Flexible Guns	1 × MG 81Z	1 × MG 81Z

Innovative Failure

In May 1940, a possible successor to the Bf 110 had made its first flight: The Arado Ar 240. This first flight occurred with some delay, as after the outbreak of the war development work had been put on hold to give priority to the production of types already in service, in the expectation that the war would soon be won. Arado had proposed a fast three-seat fighter in 1937, soon after the first flight of the Bf 110. This E 651 design shared features with McDonnell’s Type 1 of two years later: Two Daimler-Benz engines would be buried in a wide but well streamlined fuselage, and connected to a complex gearbox. From there a shaft would drive a propeller on each wing, installed at the front of a small nacelle, which apparently also contained the cooling radiator. The E 651 would be armed with four cannon in the lower fuselage, while the gunner would be able to operate a dorsal or a ventral MG 81Z. The RLM was not enthusiastic about this complicated concept, and requested a conventional twin-engined design.

The resulting Ar 240 blended features of the E 651 with the E 310 design for a multi-engined, multi-role carrier aircraft. It had a superficially conventional layout, but nevertheless several radical design characteristics. To reduce drag, the engine nacelles and fuselage were slender and long. The fuselage cross-section was barely larger than that of the Bf 109. Annular radiators for the 1100 hp DB 601A engines were installed in front of the engine nacelles, with large hollow propeller spinners to provide airflow. And although the aircraft would be about a ton heavier than the Bf 110, the wing area was 30% smaller. This resulted in a wing loading of 300 kg per square meter, very high for the period. Large Fowler flaps and automatic leading-edge slats were provided to get acceptable landing speeds.

Calculations suggested that it would have a top speed of 674 km/h when equipped with the smaller of two wing designs, of 12.1 m span, and a pressure cabin. But by being a small but heavy aircraft, the Ar 240 would inevitably incur some penalties in handling, worsening as more war equipment was added to the airframe. Indeed the development story of the Ar 240 reveals a constant need for growth, with changes involving bigger wings and tail, a longer fuselage, and more powerful engines. Making things more complicated without much benefit was a dive-bombing requirement. The first prototype was equipped with dive brakes in a tail cone, apparently found unsatisfactory and omitted from the later aircraft.

The first flights revealed that the Ar 240 was indeed fast, but had unsatisfactory handling characteristics, being unstable around all axes. The wing profile was thought to be the cause of the ineffectiveness of the ailerons, on which some development work was done. As work was already proceeding on a much-modified third prototype, the test programmes of the Ar 240V1 and V2 were cut short and ended obscurely. The most obvious change in the Ar 240V3 was the location of the cockpit, which Arado had been instructed to move to the extreme nose, instead of over the wing centre section as on the first aircraft. The new cockpit provided not only a good view of the upper hemisphere, but provided the pilot with a transparent panel in the nose, down to his feet. (The better forward view must have been offset by a much greater vulnerability, and Arado proposed an armour plate in front of the pilot that could be rotated to either provide better protection or the optimal view.) As a consequence of this design change, the engine nacelles were extended forwards to avoid putting the pilot in the plane of the turning propellers, which would have been noisy as well as dangerous. An aft fuselage extension was designed to restore stability. Wing span was increased to 14.3 m.

The Ar 240V3 was still unstable, although the test center in Rechlin found handling in August 1941 to be generally acceptable. Development continued with the V5 and V6 which were more representative of the planned production version, including the installation of the intended defensive armament. Improved rear defence was to be provided by remotely controlled gun barbettes, an upper and a lower FA 13, each containing a MG 81Z twin machine gun. The gunner would aim these from his seat, with remote periscopic sighting heads. The development and test programme stretched deeply into 1942, but already in February 1941 the RLM had accepted a proposal to build a small pre-series of six aircraft, and the first Ar 240A-0 pre-series aircraft flew in June 1942.

Plans to put the type into production evaporated. As a replacement of the Bf 110, the Ar 240 competed directly with the Me 210. The latter had more than its fair share of aerodynamic problems, but in late 1942 solutions for those were being developed. The Ar 240 might be faster but its handling characteristics were far removed from those of a good fighter. Its stability problems, bad stalling characteristics, and poor harmony of control made it a bad weapons platform and restricted its manoeuverability too much. And there was no spare production capacity to support an additional type. It is not quite clear why the team of chief designer Blume did not take more radical steps to address the aerodynamic problems. Instead the team appears to have produced a steady stream of proposals to fit more powerful engines.

The Ar 240 did see limited service as a reconnaissance aircraft, a role for which its potential had been recognised early in 1941. Prototypes and A-series aircraft were converted for this role, in which its high speed was used to advantage. Forward firing armament was restricted to an MG 17 in each wing root. The remote-controlled gun turrets were retained and functioned well. The Ar 240A was credited as the only German reconnaissance aircraft able to complete missions over Britain.

Plans were still made for an Ar 240B powered by DB 605 engines, envisaged by the Luftwaffe as a fast bomber. This was a somewhat odd concept as the type could carry bomb loads only externally. Arado preferred an Ar 240C powered by the bigger DB 603, and converted two A-0 pre-series aircraft to have these engines. The production C-series would be bigger, with a wing span of 16.6 m and a length of 13.35 m. But in December 1942 Arado was told to stop all work on the Ar 240. An attempt to revive the type as the Ar 440 — what’s in a name? — was not successful.

Embarrassment

Messerschmitt’s concept of a successor for the Bf 110 was in some ways close to Arado’s: A smaller, heavier, and faster aircraft with improved defensive armament. But it was a less radical and more elegant design, and sufficiently convincing that in the autumn of 1938 the RLM ordered 2000 aircraft off the drawing board.

The Me 210V1 prototype made its first flight on 2 September 1939. It was a slightly smaller aircraft than the Bf 110, with conventional but pleasing lines. The cockpit was well forward in the nose, which featured a transparent panel to give the pilot a good forward and downward view. Below the cockpit floor, in an unusual location forward of the wing’s leading edge, was a small internal bomb bay. As so many German aircraft of the period, the new fighter was required to have a dive-bombing capability. The 1300 hp DB 601E engines were installed in neat cowlings. The V1 had twin tail fins, also installed at first on the second prototype, Me 210V2. But this was subsequently modified to the single tail fin that had been designed as an alternative, and which was used on all other Me 210s. The V2 also featured the type’s innovative defensive armament: Remote-controlled barbettes with a 13-mm MG 131 each, installed on the side of the fuselage. The rear of the cockpit canopy was modified to provide flat clear-vision panels.

The Me 210 looked good, although its fuselage was tadpole-shaped, with a round, wide nose and a short, sharply tapered aft fuselage. Test flights revealed marginal stability around all axes, poor harmony of controls, and disappointing performance. In an echo from the Ar 240, the wing profile was blamed for longitudinal stability problems. Handling was improved with the single tail, but not sufficiently so. Although a series of prototypes was built incorporating various changes, Messerschmitt failed to make sufficient modifications to cure the problems. In June 1941 it was concluded that after a long development period, the Me 210 was still unsatisfactory; it was too unstable to be a good gunnery platform, unsatisfactory as a dive-bomber, was too difficult to control during take-off, and suffered reliability problems including engine fires. The cause of this failure is unclear but it is likely that Willy Messerschmitt’s strong inclination to build aircraft as light as possible got in the way of some necessary changes, such as an extension of the aft fuselage to make the tail surfaces more effective. Only in February 1942 did the Me 210V17 fly with a longer, deeper fuselage.

The original plan had been to start production in late 1941, and in expectation of this the production of older aircraft had been allowed to taper off. Despite the enduring problems with the prototypes, these plans maintained their momentum. Erprobungsgruppe 210 began operational testing in September 1941, and other units began to receive the new fighter in early 1942. With two 1350 hp DB 601F engines, a fully loaded weight of more than ten tons, a wing loading of 285 kg per square meter, and enduring handling problems, these aircraft were widely perceived to be failures. They were faster than the aircraft they were to replace, but they were also plainly dangerous, with a high accident rate. Especially landing accidents were frequent.

On 12 March 1942, the production of the Me 210 was suspended. The RLM decided to increase production of older types to fill the gap and launch production of the Bf 110G while attempting the repair the defects of the Me 210. Willy Messerschmitt lost his directorship of the company that he had founded, retaining only the leadership of the design office for new projects. Airframes under construction and parts were stored while awaiting the results of the planned modifications, which included a longer fuselage and wing slats.

The project was saved from complete failure by the effect of these modifications, which greatly improved handling. The extension of the fuselage from 11.18 m on the Me 210A-0 to 12.13 m on the A-1 improved controllability during landing and take-off. Slats were added to the wing’s leading edge to enhance controllability at low speeds, the dive brakes were moved to a position in which they no longer disturbed the airflow over the tail, and measures were taken to restore the position of the center of gravity. Even so, the flying characteristics of the Me 210 were not such that the type could be operated safely at night, and thus the Bf 110 would remain in production as a nightfighter. The good news for the RLM was that the short-fuselage aircraft still on the production lines could be converted, and about 200 probably were; a roughly equal number were built from the start with the new fuselage.

These changes made the Me 210A a useful combat aircraft again, but it was underpowered. A possible solution was the installation of the DB 605, which resulted in the production of 272 Me 210Ca-1 in Hungary, on a production line set up to produce aircraft both for the Luftwaffe and for Hungary’s own MKL. German production focused on a version the new, bigger DB 603 engine, first flown in August 1942. The additional forward weight of the engines had to be compensated for by a reduction of the backward sweep of the outer wing panels, a change that could be made on existing airframes. Nevertheless, instead of being called Me 210E, the aircraft would go in production as the Me 410. It would receive priority for the DB 603, while the Bf 109 and Bf 110 would receive the DB 605. The Me 410 had excellent low-altitude performance and satisfactory handling, and was produced in parallel as a fast low-level bomber and attack aircraft, as well as a fighter.

However, the installation of more powerful engines predictably resulted in cooling problems, compounded by reliability issues with the new engine. Because there were also problems to get mass production organised again, the Me 410 did not come off the production lines in substantial numbers until the middle of 1943. The A-1 was a fast bomber version and the A-2 a heavy fighter, both powered by DB 603A engines. They would be followed by the B-1 and B-2, powered by the 1900 hp DB 603G, from April 1944 onwards. The normal fixed armament consisted of a pair of MG 151/20 and a pair of MG 17s, while the flexible barbettes with a MG 131 each provided a rear defence.

The type’s usefulness as a fast bomber was quickly cast in doubt, because of its short range and small bomb bay: With two SC 500, i.e. 500 kg high-explosive bombs, the doors would not even close; leaving a gap that had to be filled by an expendable wooden panel. (The high-explosive bombs were bigger than other bombs of the same weight, as explosives are less dense than steel.) The bomber models also had provision for external bomb racks under the wing roots. But these could not carry extra fuel tanks to extend the type’s range. Bomber versions could be converted to the Zerstörer role by installing a cannon pack in the bay under the cockpit instead, as the Me 410A-1/U2. In May 1944, the conversion of all bomber models was ordered.

The concept of a cannon pack that could be installed as an exchangeable unit was innovative as well as practical, but as was common for German fighters of the period, a bewildering set of armament options was developed. These included the WB 151A with two MG 151/20 cannon, which seems to have been used most, but there were also alternative packs with two 30 mm MK 103, four 30 mm MK 108, or one 50 mm BK 5. Of these the BK 5 was probably the least useful. Derived from a tank gun, this weighed 540 kg and had an ammunition supply of only 21 rounds, fired at 50 rpm. The goal was to shoot US bombers down from a safe distance with a weapon that could destroy them with a single hit, but accuracy and reliability problems made it ineffective. From early 1944 onwards, the presence of US escort fighters put and end to the effectiveness of the Me 410 as a daylight interceptor.

It remained a troubled aircraft in search of a role. A lighter single-seat version without defensive armament was abandoned as it would not be able to fight on equal terms with allied fighters anyway. Finally, in June 1944, in order to rationalise German war production, the Me 410 was abandoned to free raw materials and manpower for other aircraft. The production run of the Me 410 had produced only 1160 aircraft, so that the total production of the Me 210 and Me 410 finally added up to less than the original off-the-drawing-board order.

Heavyweight

The aircraft that filled the gap in the German nightfighter arsenal was the Junkers Ju 88. It was an unlikely success, because the Ju 88 was a medium bomber, and most fighter conversions of such aircraft were seriously disappointing. And the Ju 88A bomber was a substantial aircraft too, with a wing span of 20.08 m and maximum take-off weight of 14 tons, substantially bigger than a Blenheim or an A-20. On the other hand, it was relatively fast, with a top speed of 510 km/h in the Ju 88A-4 bomber version, and remarkably manoeuverable for its size, with light, effective controls. As a bomber, the Ju 88 had its weaknesses, especially its light defensive armament, but it was a true pilot’s aircraft.

Early in the war, the Ju 88 was expected to be the backbone of the Luftwaffe, with a planned strength of 7000 aircraft backed by a complex of factories that would turn out 250 aircraft per month. When shortages forced a reduction of German rearmament plans in the summer of 1939, this was the one programme that the Luftwaffe sought to preserve at all cost. Heinrich Koppenberg was made “special plenipotentiary” for the production of the Ju 88, and he hoped to use the techniques of mass production — often named ‘Fordism’ after the man who had become the symbol of them.

In that context, a fighter version of this versatile aircraft was useful to explore, and in September 1938 the Ju V7 prototype flew with a simple modification, three fixed MG 17 machine guns and one MG FF cannon installed in the right side of the nose. Two further prototypes were more thoroughly modified with a sheet metal nose, and the option to carry the MG 151/20 instead of the MG FF. Experiments were also conducted with a modification of the ventral fairing under the nose of the Ju 88 to install a MG 151/20 or MG 151. The results were promising enough to put a Zerstörer version into production as the Ju 88C, although at first on a very limited scale: Out of 2208 Ju 88s produced in 1940, only 62 would be fighter variants. In 1941 the number would be 66, while 1942 saw a modest increase to 257. In 1943 the production of Ju 88 fighter versions would be above 700, as the German air force was pushed into a defensive role. In 1944, 2518 out of the 3234 Ju 88s produced would be fighter models!

The first Ju 88C-2 model was a straightforward conversion of the A-1 bomber model, with the metal sheet nose containing three machine guns and one 20-mm cannon. The elimination of external bomb racks, dive brakes, and the defensive machinegun installed in the windscreen of the Ju 88A did reduce drag. But the Ju 88C-2 did retain its internal bomb bays, although it often carried an extra fuel tank in the forward bay. And the engines were the same 1200 hp Jumo 211B or 211G used by the bombers, as the desired BMW 801 radials were not available. The Ju 88C-4 was a similar direct conversion of the Ju A-5 bomber, which featured a wing of increased span. It’s forward-firing armament could be boosted by installing two MG FF cannon in the ventral gondola. The Ju 88C-6 had more powerful Jumo 211J engines with paddle-blade propellers, improved defensive armament, and some additional armour plate in the cockpit.

The missions flow by these aircraft were quite diverse. The first deployment, in the spring of 1940, was to bases in Norway to fly anti-shipping missions. The aircraft proved very effective in this role. But later in the year, the units were incorporated in the nightfighter forces, operating from Holland and flying mostly intruder missions against British bases. After intruder missions were cancelled in October 1941 (a serious tactical error on the Luftwaffe’s part) the aircraft were shifted to the Mediterranean instead, as they were thought more suitable for offensive missions than for interceptions at night. In June 1942 the Junkers began to operate against allied anti-submarine aircraft in the Bay of Biscay, a crucial transit area for submarines based in ports on the French coast.

The opponent encountered over the Bay and in the Mediterranean, but also at night over Britain, was frequently the Bristol Beaufighter. The Beaufighter Mk.VI was considerably smaller and lighter (9,798 kg loaded versus 12,350 kg loaded) than the Ju 88C-6, and had more powerful engines (1600 hp Hercules VI radials versus 1400 hp Jumo&211J V-12 engines), It is no surprise that it was faster, with 536 km/h at 4,755 m versus 494 km/h at 5,300 m. However, the Junkers was the more manoeuverable aircraft. The Beaufighter had superior forward firepower, with four 20-mm cannon and six rifle-calibre machine guns against three and three, although only the Junkers also had defensive guns.

Late in 1942, the Ju 88C-6 also began to receive FuG 202 Lichtenstein BC radar sets with their characteristic antenna array on the nose of the aircraft, replaced later by the FuG 212 and in late 1943 the FuG 220. While the Bf 110 was the most numerous aircraft in the Nachtjagd, the bigger Junkers had a greater ability to carry additional equipment, such as the FuG 227 Flensburg homing device, which picked up the emissions of the Monica tail-warning radar fitted to RAF bombers. It was also fitted with Schräge Musik installations, with the guns installed in the bomb bay and firing upward through the fuselage aft of the cockpit. The MG 151/20, heavier but more powerful than the MG FF usually found on the Bf 110, was most often found in such installations.

A big aircraft such as the Ju 88 could always benefit from more engine power if it had to operate in the fighter role. The BMW 801 radial was installed on the Ju 88C-5, but only ten aircraft of this version were built because the engine was much in demand for the Fw 190. This model also saw deletion of the ventral gondola and the installation of a streamlined ventral weapons pack, albeit with just two rifle-calibre machine guns. Similar changes appear to have been made to a handful of Ju C-7 machines, powered either by the Jumo 211J or the BMW 801. In early 1943 the decision was at last made to produce the Ju 88R-1, a straightforward modification of the C-6 with 1600 hp BMW 801A engines, while the R-2 was powered by the 1700 hp BMW 801D. Both models were built as nightfighters, the R-1 with FuG 202 or FuG 212 and the R-2 with the FuG 220. Armament remained unchanged except for the deletion of the ventral defensive gun.

But the R series, of which the production ended in early 1944, was an interim version awaiting the production of the Ju 88G. As it came off the production line in late 1943, the Ju 88G-1 could easily be recognised by its larger, squared-off tail surfaces, adopted from the Ju 188 bomber, which gave more stability. The larger ailerons, fitted to improve control response, were less obvious. Both changes had been required to cope with the increasing weight and power of the nightfighter models. The armament configuration was redesigned, with deletion of the gondola under the cockpit and the installation of four MG 151/20 cannon in a ventral pack. Two more cannon were installed in the nose, but in service these were frequently deleted because of their muzzle flash. A dorsal MG 131 was retained as defensive gun. The engines were BMW 801D. FuG 220 Lichtenstein SN-2 was standard, with masts and antennas reshaped to reduce drag. The changes gave the Ju 88G a different allure than earlier models, pugnacious and sleek.

The final production fighter was the Ju 88G-6, with 1750 hp Jumo 213A inverted V-12 engines, installed in round cowlings with annular radiators in front, so that both versions looked superficially similar. The G-6 was 40 km/h faster than the G-1, despite an increase in weight. Usually FuG 220 radar was fitted, with the antennas installed at 45 degrees from the vertical. Some late-war aircraft had alternative installations, including some that carried FuG 240 Berlin, a copy of the allied magnetron-based, centimetric radar sets, installed with a dish antenna under a wooden nose cap. The G-7, once thought to have been a late-war production model, probably did not get beyond the prototype stage, while the long-range G-10 was produced but did not reach combat units.

The Ju 88G became the Luftwaffe’s main nightfighter in the final year of war. Although it was still fundamentally an improvised fighter, it had good handling and high performance. The large airframe allowed the aircraft to carry heavy armament and a high standard of equipment with a relatively modest performance penalty. Top speed of the model with Jumo 213 engines is usually given as 626 km/h at 9100 m. British test pilot Eric Brown claimed to have reached 644 km/h in one!

Last of the Line

Junkers planned nightfighter derivatives of its later bombers, including a Ju 188R and finally the Ju 388J. The Ju 188 was originally developed as a stop-gap design to counter delays in the Ju 288 project, and was evolved from the Ju 88 with various improvements to the aerodynamics and the cockpit layout. Although the bomber version entered production on a modest scale, the Ju 188R nightfighter model did not. It probably would have offered few advantages over the Ju 88G.

The failure of the Ju 288 and the entire Bomber-B project lead to a further revision of the Ju 88 and Ju 188 line, to meet a requirement for a fast high-altitude bomber under the Hubertus Programm. The Ju 388 thus became a straightforward development of the Ju 188 with high-altitude engines and inheriting some of the equipment developed for the Ju 288.

Accordingly, the first prototype of the Ju 388J was flown in January 1944 with turbocharged BMW 801TJ radials. It carried FuG 220 radar, a belly pack with two 20-mm MG 151/20 and two 30-mm MK 108 cannon, and a remotely controlled tail turret with two 13-mm MG 131 machine guns. The next two prototypes omitted the tail turret and carried FuG 218 Neptun radar, with a streamlined nose cone fitted to reduce the drag of the antenna mast.

The Ju 388J was intended to be a specialised high-altitude nightfighter with a service ceiling of 13,000 m. But it never entered service, as in early 1945 the worsening German war situation resulted in the cancellation of the Ju 388 programme.

Unglued

The Junkers Ju 88 was the closest German equivalent to the British de Havilland Mosquito: A versatile, high-performance twin-engined combat aircraft. But there was also a German aircraft that emulated to Mosquito in another important aspect: Wooden construction. The Ju 88 was of course an all-metal aircraft, but like many other participants in the war, the German government was worried about shortages of aluminium alloys. Late in the war it would achieve some savings by substituting wood for metal parts, for example by fitting a wooden tail to the Bf 109.

The Focke-Wulf Ta 154 was a more radical attempt to develop a multi-role combat aircraft of wooden construction. Proposed by Focke-Wulf’s chief designer, Kurt Tank, it was clearly inspired by the British example. It would make use of advanced woodworking techniques and be glued together with the new Tego-Film adhesive. The initial requirement was for an aircraft powered by two Jumo 211 engines, which were readily available. Discussions during most of 1942 envisaged the new aircraft as a fast bomber, with some concerns raised about the risks of a wooden design. But due to the growing need to defend Germany against bomber attack, the design was recast as a nightfighter in October 1942. The RLM wanted the new aircraft to fly in July 1943, less than one year after signature of the contract. Initially it was called the Ta 211, with the “Ta” code assigned in honor of Dr. Tank, but this was changed into Ta 154.

The Ta 154V1 prototype emerged in June 1943 as a sleek aircraft with a wing at the shoulder position, a tricycle undercarriage, tandem seating for the crew of two, and 1340 hp Jumo 211F engines in streamlined nacelles with circular radiators in front. Both the fuselage, which had an oval cross-section little larger than that of the engine nacelles, and the wing were made of wood. However, metal panels were used to cover the engine nacelles, and the control surfaces were also of metal construction. The wooden construction was potentially heavier than the equivalent all-metal design. With a maximum take-off weight of more than eight tons, the Ta 154 was heavier than the Bf 110, though lighter than the Me 210.

The prototype made its first flight on the first of July. The aircraft flew well, with light, effective controls and a high rate of roll. Nevertheless its flying characteristics came in for some criticism, addressed during development by enlarging the tail to counter the destabilising effect of the radar antennas and to improve controllability with one engine out. And very late in the type’s development, upturned wingtips would be added to improve lateral stability. But the Ta 154 did not have the kind of handling problems that had ruined the Me 210 and Ar 240.

The armament of four cannon (in production aircraft two MG 151/20 and two MK 108) was to be installed in the sides of the fuselage, aft of the cockpit. The gun muzzles were as far forward as the pilot’s seat, well below the rim of the cockpit, but perhaps not ideal when considering the effect of muzzle flash on the crew’s night vision. The crew had a benefit of a cockpit well protected with armour plate and an armour glass windscreen, but the view for the radar operator in the rear seat, below the leading edge of the wing and in between the engine nacelles, was very restricted. The pilot had good forward and upward view, but a poor view to the sides and the rear. This was judged to be acceptable for night operations but considered a serious weakness in daylight.

The first prototype lacked most military equipment; the second had FuG 212 radar and the third carried armament, although only the fourth had the definitive armament installed. Vibration and local damage occurred when firing the guns, and reinforcements were needed. Following the initial successful flights, the RLM had already ordered 250 aircraft, and assigned factories to build the Ta 154 at (as usual) an unrealistically high rate, not only as nightfighters, but also as heavy day fighters and (again) fast bombers. These production schedules soon came apart, not in the least because several factories were destroyed by allied bombing. But the pre-series of 22 A-0 aircraft was followed by the first production aircraft in May 1944. These were A-1 and A-4 models, powered by the Jumo 211N or Jumo 211R and distinguished mostly by their radar, FuG 212 for the A-1 and FuG 218 or FuG 220 for the A-4. They had a wing span of 16.00 m and a maximum take-off weight of 8250 kg.

The top speed of 615 km/h at 5790 m was respectable, but fell short of the initial expectations. The aircraft was underpowered with these engines, and the addition of flame dampers and antenna arrays for night combat badly eroded performance. The evaluation center (Erprobungsstelle) of Rechlin calculated that the top speed of a Ta 154A fully equipped for combat would be only 580 km/h. Combined with the restricted view from the cockpit this made an unfavourable impression on some Luftwaffe pilots, crucially including Adolf Galland and the highly experienced nightfighter pilot Werner Streib. In May 1943, Galland ordered that until a better cockpit could be provided, other development work on the Ta 154 would be stopped. Aircraft built with the old cockpit would serve only as nightfighters or fast bombers. On the positive side, the Ta 154 was easy to fly, which given the poor standard of training of most Luftwaffe pilots in 1944 was very important, and very agile for an aircraft of this size. But the question evidently arose whether this was enough to justify its existence. The programme was being challenged by those within the Luftwaffe who expected more from alternative designs, such as the Ju 388J and the He 219.

The need for more powerful engines had been accepted already in January 1943. The Jumo 213 was the obvious candidate, but its development (and that of the competing DB 603) had been delayed by the low attention given to new projects earlier in the war: It would not be available for production aircraft before March 1944. The version powered by the 1775 Jumo 213A was to be the Ta 154C. To address the criticism of the crew positions, this version was to have a new all-metal forward fuselage, with a bubble canopy to improve rearward view, while the crew was given ejection seats. An extension of the aft fuselage would compensate for the additional engine weight forward. Total take-off weight would climb to 9920 kg. Both a single-seat day fighter version and a two-seat version were being proposed. But in the end, only prototypes were completed with with Jumo 213 engines, the first being the Ta 154V8.

Industrial, more than technical issues, sealed the fate of the Ta 154. The success of the test programme had already been seriously undermined when inspection of the fifth, six and seventh prototypes revealed major defects in construction. This confirmed what opponents in the RLM had already feared, i.e. that wooden construction posed new challenges to an industry used to working in metal, and the need for skilled labour had been underestimated. This seriously affected the ambitious production plans. There were also concerns about field repairs, which would require a new set of skills. In addition reliability issues with the landing gear and hydraulics continued to plague the Ta 154. In June 1944 a production stop had to be imposed by Dr. Tank, while it was investigated why the wing of a Ta 154A-1 had disintegrated in flight. The cause of the problem, rather ironic for a fighter that had been designed as a wooden aircraft to avoid supply problems, was the destruction of the single factory that produced the Tego-Film adhesive. A substitute glue, Kaurit, had been selected, but its application resulted in unsatisfactory quality of construction, as the glue damaged the wood instead of correctly bonding it.

Kurt Tank was forced to defend himself against accusations that he was sabotaging the war effort. In August 1944 he was cleared, but meanwhile the program had been cancelled. As the regime tried to rationalise war production by focusing on a limited number of types, the Ta 154 fell into disfavour, perhaps also because it was regarded as a too specialised nightfighter, despite proposals to build also day fighter versions. About 50 aircraft may have reached combat units. Both the Ta 154C and the further developed Ta 254 remained on the drawing board.

The Ta 154 demonstrated the ability of German engineering to build a high-performance twin-engined fighter out of wood. While the Messerschmit and Arado teams had failed because of unsolved aerodynamic problems, the Focke-Wulf project failed mostly for industrial reasons. The design was not without its flaws, especially the original cockpit design, which was unsuitable for a fighter presumably because the aircraft had originally been intended as a fast bomber. These faults could all have been resolved. But given the choice between the wooden Ta 154 and the all-metal Junkers and Heinkel designs, the more conventional construction technique had substantial advantages.

Overrated

One of the most famous of the German nightfighter designs originated in 1940 as a fast bomber and reconnaissance aircraft. The initial proposal was for a fast bomber and reconnaissance aircraft derived from the Heinkel He 119. That was a very unusual research aircraft which featured a DB 606 engine buried in the mid fuselage, driving the propeller on the nose by means of long extension shafts. The DB 606 consisted of two coupled DB 601 units, and for its new aircraft Heinkel proposed to use the DB 613 (created by coupling together two of the new DB 603 engines) or the DB 615 (two coupled DB 614 engines, themselves planned developments of the DB 603). The DB 613 was expected to deliver 3,800 hp for take-off. At least this avoided the complex angled drives proposed earlier by Arado and McDonnell, but in August 1941 the RLM nevertheless decided that it wanted a heavy fighter and nightfighter of more conventional layout, scrapping the design work done so far. The origins of the project remained visible only in the designation given to it: He 219.

It was intended to be powered by DB 603G high-altitude engines, which delivered 1900 hp for take-off and 1560 hp at 7200 m. But its slow development initially restricted the He 219 to the DB 603A, which delivered only 1750 hp for take-off. It was in this form that the prototype was flown on 6 November 1942. With a wing span of 18.5 m, a wing area of 44.5 square meters and a take-off weight of 11,750 kg, the He 219 was a substantial aircraft for a fighter. It had plain, angular lines: The fuselage had a rectangular cross-section and little taper until half way to the tail. The wing, with a plain and a straight leading edge, passed through the fuselage without any blending or fairing. The tail was a simple structure with twin tail fins. As common on German aircraft if this time, the engines were installed in round nacelles with an annular radiator in front. The design of the He 219 had been optimised for ease of production, allowing Heinkel to claim that the He 219 could be built for a third of the cost of the competing Junkers Ju 188.

Following the pattern now favoured by the Luftwaffe, the crew of two sat in the extreme front of the fuselage, well ahead of the propellers. They sat on ejection seats powered by compressed air, which would lift the seats about four meters, high enough to clear the propellers in an emergency. These seats were back-to-back under a bubble canopy, giving an excellent view forward and all-around the upper hemisphere. The view for landing and take-off was also very good, for the Heinkel had tricycle landing gear. Bays for fixed guns were provided in the wing roots and in a ventral pack, putting the muzzle flash well outside the field of view of the pilot. Earlier plans to install defensive guns were dropped before the aircraft entered production, though they would be reappear in later design sketches.

Early test flights revealed some instability in jaw, as well as vibration of the tail section. These were cured by lengthening the tail and enlarging the tail fins. Otherwise the handling of the prototypes was good. The DB 603A engines left the big aircraft somewhat underpowered and it was slower than expected. But results were encouraging enough to proceed with a series of twelve prototypes.

Its good characteristics would save the He 219 from oblivion, because the production of a specialised nightfighter was repeatedly challenged by the champions of multi-role designs, such as the Junkers Ju 88. After the first comparative flight tests in January 1943, the RLM established a production plan that would see the Bf 110 succeeded as a nightfighter by the Ju 88 and Ju 188, excluding the He 219. But the positive evaluation of the prototype by Major Werner Streib, further comparative tests in March, and the front-line testing of V7, V8 and V9 prototypes from June 1943 onwards, changed these plans. The nightfighter force wanted the He 219, and when offered the Ta 154 instead, turned down the latter because of its inferior cockpit design. General Kammhuber and his staff in the Nachtjagd wanted to have specialised nightfighter, even if the He 219A was a bit too slow to be a good Mosquito interceptor. But these conflicts would have a disruptive influence on the development and production of the He 219. Meanwhile, Heinkel projected multi-role versions, especially in the planned He 219C series, and even proposed a He 419 high-altitude bomber with turbocharged engines.

The production of the He 219 was also beset by the inefficiencies and vacillations that plagued the German armaments industry. In April 1943 the future production rate was set at fifty aircraft per month, far more reasonable than those given for some other projects, although it was increased in June to 150. However, amidst conflicts about the allocation of factories and workers, the initial production rate was only 14 per month. And not only the quantity, but also the quality of the produced aircraft was deficient. At this stage of the war, the German skilled workforce was diluted more and more by foreign workers and slave labour, while German workers were drafted by the army. This was combined with the disruptions caused by allied bombing and the dispersion of the He 219 production over Germany, Austria and Poland. Production finally continued until March 1945, despite a decision in May 1944 to cancel the Heinkel nightfighter, which was soon reversed. Production rates finally stabilised at about 20 aircraft per month, and total production is thought to have been about 330 over a period of nearly two years, a far cry from the force of 2000 aircraft that the Nachtjagd had hoped for.

The type entered combat in June 1943 with NJG 1 at Venlo in the Netherlands, which would for some time be the only base able to service it. The He 219 proved to be a popular aircraft. It was not particularly fast, as top speed with DB 603A engines, flame dampers and the Lichtenstein SN-2 antenna array was only 585 km/h. But it did offer better endurance than other nightfighters, which made the force more effective. The first pre-production A-0 was flown in combat by Major Wener Streib on 11 June 1943, and he claimed five RAF bombers in a mission of 144 minutes. Although the aircraft was lost during landing because of defective flaps, the He 219 had made a successful entry into combat.

The A-0 preproduction run of more than hundred aircraft with FuG 212 radar was followed by the A-2, which had FuG 220 radar and longer range. The later versions are poorly documented, and it is likely that only the A-7 was produced in any number, with DB 603E engines, although the first ones were delivered with the DB 603A. Several of the many prototypes were reconditioned and delivered to combat units, thus creating sparse deliveries of models such as the A-5.

Armament installations were equally confusing. Depending on the model and one of many different variant installations, the wing roots were fitted with the 20-mm MG 151/20 or the 30-mm MK 108, while the ventral pack held four MG 151/20, two or four MK 108, or two high-velocity 30-mm MK 103 cannon. In practice it appears that the reliable and readily available MG 151/20 was often retrofitted in the field. Schräge Musik, when installed, consisted of two MK 108 cannon, but it appears that many crews preferred to have this removed.

To give a much-needed performance boost, versions with more powerful engines were explored. Six A-series aircraft were converted to the Jumo 213E with methanol-water injection (MW 50) to boost performance, but cooling and other installation problems were not yet solved at the end of the war. The engine mounts of the He 219 deviated from the normal German practice and did not permit the exchange of the engines as “power eggs”. A simpler alternative was to install a jet engine to boost performance when needed, and two prototypes flew with a BMW 003 jet engine under the fuselage, the first in August 1943. This gave a boost of 45 km/h when the engine was running, and a penalty of only 10 km/h when it was not.

Rather more far-fetched were plans drafted around the Jumo 222, an unusual engine with six banks of four cylinders in a star configuration, making it conceptually a liquid-cooled radial. Offering 2500 hp at take-off, it was never fully developed. Nevertheless two aircraft became the V16 and V23 prototypes when fitted with these engines, which would have powered the projected H 219B. As the Jumo 222 weighed about 20% more than the earlier engines, the wing span was increased to 22 m and the landing gear wheels enlarged. Without the ventral armament tray and with a redesigned cockpit canopy to reduce drag, the prototype was capable of 700 km/h. The B-2 was planned to be a three-seat aircraft. Also the projected C-series would have been three-seat aircraft, with the addition of a remote-controlled defensive turret, the HL 131V with four MG 131 machine guns.

It is often claimed that the Northrop P-61 was the war’s only purpose-designed nightfighter, but the He 219, despite its complex origins, could be said to be another one. As such it clearly was a competent aircraft, well liked by those who flew it. A less complex design than the P-61, it had similar performance characteristics — agile for its size but handicapped by shortfall in engine output. It also acquired a similar reputation. But in the end it is difficult to escape the conclusion that those in the RLM who preferred the Ju 88 were right. Developments of the Junkers bomber were more than adequate nightfighters and they could be produced in substantial numbers. While the He 219, although cheaper to build in theory, could not. This does not reflect on the quality of the aircraft design, but the state of the German industry in 1944 and 1945.

Push-Pull

Near the end of World War II, a new implementation entered service of an old concept, the twin-engined fighter with a push-pull configuration, with both engines buried in the fuselage. The evident advantage of this concept was that it eliminated engine nacelles on the wing, which otherwise increase drag and result in an unfavourable mass distribution, at least for an aircraft that needs to be agile. Also, in a tandem design there is no asymmetry when one of the engines is shut down. On the other hand, much of the volume of the fuselage is taken up by the two engines, and power transmission from the rear engine is a challenge, as it needs to be in the rear fuselage reasonable close to the centre of gravity.

Several earlier designs, such as the Fokker D.XXIII, solved the latter problem by adopting twin tail booms, which allowed a short and simple transmission to a pusher propeller at a penalty in structural complexity and weight. Dr. Claudius Dornier instead favoured a long drive-shaft to drive a propeller at the extreme end of the aircraft, behind the tailfins. He patented the concept in 1937 and in 1940-1941, proved the feasibility with the small Göttingen Gö 9, which featured a pusher propeller behind a cruciform tail. This tail, of course, necessitated tricycle landing gear.

Work on what would become the Do 335 started in 1942 to meet a request for a fast twin-engined fighter-bomber, and three prototypes were ordered in January 1943. The Do 335V1 made its first flight on 26 October of that year, a very respectable pace of development for a large and complex new aircraft, which broke new ground in many ways. The Do 335 handled well, was fast at sea level, and flew well with one engine shut down. A slightly higher speed could be reached flying with only the rear engine than with only the front engine. The throttle settings of the engines could affect longitudinal stability, but otherwise handling was conventional, with some complaints about heavy aileron forces. During development, leading edge sweep was added to the wing root to cure a tendency towards asymmetric stall.

A dual control trainer was developed in 1944, featuring a second cockpit raised above the first one, over the wing, offered a good forward view for the instructor. A small number of aircraft was converted to this configuration as Do 335A-11 and A-12, which were strictly intended as a trainer and not as a nightfighter.

The Achilles heel of the design was the cooling of the rear engine. The Do 335 was powered by large liquid-cooled V-12 engines, the DB 603 in the first prototypes and most production aircraft, and the alternative Jumo 213 in the V6 and V7 prototypes. The front engine had a frontal ring cooler, much favoured on late-war German aircraft and quite efficient, but the rear engine was provided by a cooler to which air was fed by a large ventral scoop. This worked very well on other aircraft (notably the P-51 Mustang) but its implementation on the Do 335 was problematic. As the control cables ran close to the rear engine, fires in this area would be fatal. The rear engine drove the pusher propeller via a 3.5m long, hollow extension shaft. Reversible pitch on one of the propellers helped to shorten the landing distance.

Inevitably, the Do 335 was big. The first A-0 pre-production series had an empty weight of 6530 kg and a loaded weight of 9510 kg, with a wing span of 13.80 m. But it is fair to compare this with the contemporary Me 410, which also featured two DB 603 engines: The Me 410B-2 had an empty weight of 7982 kg (22% more) and a loaded weight of 11,236 kg (18% more), while its wing span was 16.35 m (18% larger). The Do 335A-0 was a single-seater with a top speed of 732 km/h at 7100 m, enough to make interception by Allied fighters quite difficult, while the Me 410B-2 could do no better than 630 km/h at 8100 m and was quite vulnerable to escort fighters when deployed on bomber interception missions. The Do 335 had excellent speed and acceleration, and was very agile for an aircraft of its size.

The pilot of a Do 335 was not to be envied in all respects. The cockpit was rather heavily framed and offered little or no rearward vision, though rear-view mirrors were fitted and forward view was good. Should the pilot need to leave the aircraft, then he had a press three buttons, one to blow off the rear propeller, a second to remove the upper fin, and a third to arm his ejector seats, then grip two large levers to jettison the canopy, and finally squeeze a trigger to activate the ejector seat, which was then expelled by compressed air.

As a heavy fighter-bomber, the initial Do 335A-0 was fitted with a small bomb-bay, for a 500 kg bomb or an extra fuel tank. External bomb racks could be installed under the wings. A powerful high-velocity 30-mm MK 103 cannon was installed on the centreline, firing through the propeller hub of the front engine, and two 20-mm MG 151/20 in the upper engine cowling.

Considering the size of the aircraft, that armament was modest enough. A planned B-2 series, never produced, would have increased armament by installing two big MK 103 on the wings, in front of the main wing spar, under large fairings — a somewhat awkward-looking arrangement but probably optimal in terms of drag and recoil transfer.

As was commonplace in the Reich, the management of the Do 335 program was inefficient, with only small-scale production even after the He 219 was cancelled in favor of the Do 335, and an excessive number of different prototypes to keep the project team busy: Heavy Zerstörer, trainers, nightfighters, and reconnaissance aircraft with different versions of the DB 603 or Jumo 213 engines. A series of paper designs explored the possibilities of extended wing span, jet engines, and swept wings. Dornier even explored the “twinning” of the Do 335 fuselage to produce a four-engined Do 335Z, which then resulted in a Junkers project to develop this as a strategic reconnaissance aircraft under the name Ju 635, which apparently got as far as the mock-up stage before the end of the war.

Most significant among the prototypes that were actually flown were the nightfighter versions. Two aircraft were completed as the Do 335M10 and M17, prototypes for the A-6 and B-6, respectively. These featured a cabin for a radar operator behind the pilot’s cockpit, with flush-fitting window offering almost no outside view (much in contrast to the two-seat trainer). To compensate for the reduction in size of the main fuel tank, the tankage in the wings was increased. The antennas of the FuG 218 Neptun radar were installed on the wings. Only the M10 was completed during the war, while the M17 was completed after the wa by the French. The M10 may have seen some action in the form of operational testing, but by 1945 it was already thought that the advent of jet aircraft would cut short the operational life of this type.

The British test pilot Eric “Winkle” Brown, who had the opportunity to the Do 335 after the war, praised the aircraft’s combination of speed, stability, and endurance, and believed that it would have been effective as a nightfighter, though it clearly was not agile enough to be a good dogfighter. He also observed, however, that the complex and not fully developed Do 335 was the mechanically most troublesome aircraft of all the German types tested at Farnborough.

Next: Chapter XI