Heinkel He 162

Through 1943 the U.S. 8th Air Force and German Luftwaffe entered a period of rapid evolution as both forces attempted to gain an advantage. Having lost too many fighters to the bombers' defensive guns, the Germans invested in a series of heavy weapons that allowed them to attack from outside the American guns' effective range. The addition of heavy cannons like the 30mm calibre MK 108, and even heavier Bordkanone autoloading weapons in 37mm and 50mm calibres on their Zerstörer heavy fighters, and the spring-1943 adoption of the Werfer-Granate 21 unguided rockets, gave the German single and twin-engined defensive fighters a degree of firepower never seen previously by Allied fliers. Meanwhile, the single-engine aircraft like specially equipped Fw 190As added armor to protect their pilots from Allied bombers' defensive fire, allowing them to approach to distances where their heavy weapons could be used with some chance of hitting the bombers. All of this added greatly to the weight being carried by both the single and twin-engine fighters, seriously affecting their performance.[2][3]

When the 8th Air Force re-opened its bombing campaign in early 1944 with the Big Week offensive, the bombers returned to the skies with the long-range P-51 Mustang in escort. Unencumbered with the heavy weapons needed to down a bomber, the Mustangs (and longer-ranged versions of other aircraft) were able to fend off the Luftwaffe with relative ease. The Luftwaffe responded by changing tactics, forming in front of the bombers and making a single pass through the formations, giving the defense little time to react. The 8th Air Force responded with a change of its own; after Major General Jimmy Doolittle ordered the fighters to enter German airspace far ahead of the bomber formations and roam freely over Germany to hit the Luftwaffe's defensive fighters wherever they could be found.[4]

This change in tactics resulted in a sudden increase in the rate of irreplaceable losses to the Luftwaffe day fighter force, as their heavily laden aircraft were "bounced" long before reaching the bombers.[5] Within weeks, many of their aces were dead, along with hundreds of other pilots, and the training program could not replace their casualties quickly enough. The Luftwaffe put up little fight during the summer of 1944, allowing the Allied landings in France to go almost unopposed from the air. With few planes coming up to fight, Allied fighters were let loose on the German airbases, railways and truck traffic. Logistics soon became a serious problem for the Luftwaffe, as maintaining aircraft in fighting condition became almost impossible. Getting enough fuel was even more difficult because of a devastating campaign against German petroleum industry targets.[6][7]

He 162 120077, surrendered to the British at Leck, pictured at Freeman Field, Indiana, 1945

Addressing this posed a considerable problem for the Luftwaffe. Two camps quickly developed, both demanding the immediate introduction of large numbers of jet fighter aircraft. One group, led by General Adolf Galland, the Inspector of Fighters, reasoned that superior numbers had to be countered with superior technology, and demanded that all possible effort be put into increasing the production of the Messerschmitt Me 262 in its A-1a fighter version, even if that meant reducing production of other aircraft in the meantime.[8]

The second group pointed out that this would likely do little to address the problem; the Me 262 had notoriously unreliable powerplants and landing gear, and the existing logistics problems would mean there would merely be more of them on the ground waiting for parts that would never arrive, or for fuel that was not available.[9] Instead, they suggested that a new design be built – one so inexpensive that if a machine was damaged or worn out, it could simply be discarded and replaced with a fresh plane straight off the assembly line.[10] Thus was born the concept of the "throwaway fighter".

Galland and several other Luftwaffe senior officers expressed their vehement opposition to the light fighter concept,[8][11] while Reichsmarschall Hermann Göring and Armaments Minister Albert Speer fully supported the idea. Göring and Speer got their way; accordingly, a contract tender to supply a single-engine jet fighter that was suited for cheap and rapid mass production was established under the name Volksjäger ("People's Fighter").

The official RLM Volksjäger design competition parameters specified a single-seat fighter, powered by a single BMW 003,[12][13] a slightly lower-thrust engine not in demand for either the Me 262 or the Ar 234, already in service.[14] The main structure of the Volksjäger competing airframe designs would use cheap and unsophisticated parts made of wood and other non-strategic materials and, more importantly, could be assembled by semi- and non-skilled labor, including slave labor.[15][16]

The specification stipulated various performance requirements, including a maximum weight of 2,000 kg (4,400 lb),[12] a maximum speed of 750 km/h (470 mph) at sea level, an operational endurance at least a half hour, while the takeoff distance was to be no greater than 500 m (1,640 ft).[14] Provisions for armour plating in areas such as the fuel tanks and around the pilot were also to be made, however, manufacturers were also asked to provide detail on the aircraft's performance both with and without armour installed. The armament was specified as either a pair of 20 mm (0.79 in) MG 151/20 cannons with 100 rounds each, or two 30 mm (1.2 in) MK 108 cannons with 50 rounds each.[17]

Furthermore, the Volksjäger needed to be easy to fly.[10] Some officials, such as Artur Axmann and Karl Saur, suggested even glider or student pilots should be able to fly the jet effectively in combat and, had the Volksjäger achieved widespread use, this would have been a likely occurrence.[18] After the war, Ernst Heinkel would say, "[The] unrealistic notion that this plane should be a 'people's fighter,' in which the Hitler Youth, after a short training regimen with clipped-wing two-seater gliders like the DFS Stummel-Habicht, could fly for the defense of Germany, displayed the unbalanced fanaticism of those days."[19][20] The clipped-wingspan DFS Habicht models had varying wingspans of both 8 m (26 ft 3 in) or 6 m (19 ft 8 in), and were used to prepare more experienced Luftwaffe pilots for the dangerous Me 163B Komet rocket fighter – the same sort of training approach would also be used for the Hitler Youth aviators chosen to fly the Volksjäger.[21]

On 8 September 1944, the requirement was issued to industry;[15][22] bidders were required to submit their basic designs within ten days while quantity production of the aircraft was to commence by 1 January 1945.[23] Because the winner of the new lightweight fighter design competition would be building huge numbers of the planes, nearly every German aircraft manufacturer expressed interest in the project, such as Blohm & Voss, and Focke-Wulf, whose Focke-Wulf Volksjäger 1 design contender, likewise meant for BMW 003 turbojet power bore a resemblance to their slightly later Ta 183 Huckebein jet fighter design. However, Heinkel had already been working on a series of "paper projects" for light single-engine fighters over the last year under the designation P.1073, with most design work being completed by Professor Benz, and had gone so far as to build and test several models and conduct some wind tunnel testing.[24]

As Heinkel had a head start on its design, some officials believed that the outcome was a largely foregone conclusion.[17] Nevertheless, many companies opted to produce responses; some of these competing designs were technically superior (in particular to the Blohm & Voss P 211 proposal). Messerschmitt did not submit any design, the company's founder, Willy Messerschmitt, dismissed the Volksjäger concept to be a delusional failure.[25] During October 1944, the competition's results were announced, only three weeks following the requirement being issued; to little surprise, Heinkel's submission was selected for production.[26] In order to confuse Allied intelligence, the RLM chose to reuse the 8-162 airframe designation (formerly that of a Messerschmitt fast bomber);[27] Heinkel had reportedly requested another designation, He 500, for the aircraft.[28][29]

The He 162 V1 first prototype flew within an astoundingly short period of time: the design was chosen on 25 September 1944 and first flew on 6 December,[31][41] less than 90 days later. This was despite the fact that the factory in Wuppertal making Tego film plywood glue — used in a substantial number of late-war German aviation designs whose airframes and/or major airframe components were meant to be constructed mostly from wood — had been bombed by the Royal Air Force and a replacement had to be quickly substituted, without realizing that the replacement adhesive was highly acidic and would disintegrate the wooden parts it was intended to be fastening.[42]

The first flight of the He 162 V1, by Flugkapitän Gotthold Peter – the first German jet fighter aircraft design to be jet-powered from its maiden flight onward – was fairly successful, but during a high-speed run at 840 km/h (520 mph), the highly acidic replacement glue attaching the nose gear strut door failed and the pilot was forced to land. Other problems were noted as well, notably a pitch instability and problems with sideslip due to the rudder design.[12][43] None were considered important enough to hold up the production schedule for even a day. On a second flight on 10 December, again with Peter at the controls, in front of various Nazi officials, the glue again caused a structural failure. This allowed the aileron to separate from the wing, causing the plane to roll over and crash, killing Peter.[31][44]

An investigation into the failure revealed that the wing structure had to be strengthened and some redesign was needed, as the glue bonding required for the wood parts was in many cases defective.[31][42] However, the schedule was so tight that testing was forced to continue with the current design. Speeds were limited to 500 km/h (310 mph) when the second prototype flew on 22 December. This time, the stability problems proved to be more serious, and were found to be related to phenomenon known as Dutch roll.[45] While this tendency could be resolved by reducing the dihedral, however, as the He 162 was supposed to enter production within weeks, there was no time to implement major design changes. Instead, a number of small changes were made, such as the addition of lead ballast in the nose to move the centre of gravity towards the front of the aircraft while the tail surfaces were also slightly increased in size. Despite these measures, some figures, such as Alexander Lippisch, declared the flying characteristics of the He 162 to be unsuitable for inexperienced pilots.[46]

The third and fourth prototypes, which used an "M" for "Muster" (model) number instead of "V" for "Versuchs" (experimental) number, as the He 162 M3 and M4, after being fitted with the strengthened wings, flew in mid-January 1945.[47][48] These versions also included – as possibly the pioneering example of their use on a production-line, military jet aircraft – small, anhedraled aluminium "drooped" wingtips, reportedly designed by Alexander Lippisch and known in German as Lippisch-Ohren ("Lippisch Ears"), in an attempt to cure the stability problems via effectively "decreasing" the main wing panels' marked three degree dihedral angle.[49] Both prototypes were equipped with two 30 mm (1.18 in) MK 108 cannons in the He 162 A-1 anti-bomber variant; in testing, the recoil from these guns proved to be too much for the lightweight fuselage to handle, and plans for production turned to the A-2 fighter with two 20 mm MG 151/20 cannons instead while a redesign for added strength started as the A-3. The shift to 20 mm guns was also undertaken because the smaller-calibre weapons would allow a much greater amount of ammunition to be carried.

The He 162 was originally built with the intention of being flown by the Hitler Youth, as the Luftwaffe was fast running out of pilots. However, the aircraft's complexity required more experienced pilots. Both a standard-fuselage length, unarmed BMW 003E-powered two-seat version (with the rear pilot's seat planned to have a ventral access hatch to access the cockpit) and an unpowered two-seat glider version, designated the He 162S (Schulen), were developed for training purposes.[50] Only a small number were built, and even fewer delivered to the sole He 162 Hitler Youth training unit to be activated (in March 1945) at an airbase at Sagan. The unit was in the process of formation when the war ended, and did not begin any training; it is doubtful that more than one or two He 162S gliders ever took to the air.

The Hinterbrühl underground production line for the He 162A was captured in April 1945

Various changes had raised the weight over the original 2,000 kg (4,410 lb) limit, but even at 2,800 kg (6,170 lb), the He 162 was still among the fastest aircraft in the air with a maximum airspeed of 790 km/h (427 kn; 491 mph) at sea level and 839 km/h (453 kn; 521 mph) at 6,000 m (20,000 ft),[51] but could reach 890 km/h (481 kn; 553 mph) at sea level and 905 km/h (489 kn; 562 mph) at 6,000 m (20,000 ft) using short burst extra thrust.[52] The short flight duration of barely 30 minutes was due to only having a single 695-litre (183 US gallon) capacity flexible-bladder fuel tank in the fuselage directly under the engine's intake.[53] The original Baubeschreibung document submittal for the He 162 dated mid-October 1944 showed a pair of fuel tanks for the original version of the Spatz's airframe as-designed: a single, smaller capacity 640 litre (169 US gal) fuselage main tank in approximately the same location as the later 695 litre tank was placed, with an additional wing centre-section tank just above and behind it, never produced for the production run, of some 325 litres (86 US gal) feeding by gravity into the main fuselage tank.[54] The A-2 version, in some examples (as the one flown by Royal Navy test pilot Captain Eric Brown postwar) had an emplacement of a pair of "impregnated" 180 litre (47.5 US gal) wing tanks, one built into each inner wing panel, within the first four wing ribs out from the root and between the spars, that fed into the main 695 litre fuselage tank in a similar manner to what the earlier 325 litre center-section tank had been proposed to do; but were themselves ungauged, their exhaustion of fuel only marked when the main fuel gauge began to fall during flight.[55] The production He 162A-2 was armed with a pair of 20mm MG 151/20 cannon.[51][56]

Multiple facilities were engaged in the production of the He 162, including the assembly lines in Salzburg, the Hinterbrühl, and the Mittelwerk.[51][57] By April 1945, it had been anticipated that output would reach 1,000 aircraft per month, which was double the rate achieved when the Mittelwerk plant commenced deliveries.[51] Furthermore, the Air Ministry expected that production were rise even beyond this figure in order to produce sufficient fighter coverage.[58][59]

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