Messerschmitt Me 163

Variants
Me 163A
Production of a prototype series started in early 1941, known as the Me 163. Secrecy was such that the RLM's "GL/C" airframe number, 8-163, was actually that of the earlier, pre-July 1938 Messerschmitt Bf 163. It was thought that intelligence services would conclude any reference to the number "163" would be for that earlier design. The Me 163A V4 was shipped to Peenemünde to receive the HWK RII-203 engine in May 1941. By 2 October 1941, the Me 163A V4, bearing the radio call sign letters, or Stammkennzeichen, "KE+SW", set a new world speed record of 1,004.5 km/h (624.2 mph), piloted by Heini Dittmar, with no apparent damage to the aircraft during the attempt. Some postwar aviation history publications stated that the Me 163A V3 was thought to have set the record.

The 1,004 km/h record figure would not be officially approached until the postwar period by the new jet fighters of the British and U.S., and was not surpassed (except by the later Me 163B V18 in 1944, but seriously damaged by the attempt) until the American Douglas Skystreak turbojet-powered research aircraft did so on 20 August 1947 with no damage. Five prototype Me 163A V-series aircraft were built, adding to the original DFS 194 (V1), followed by eight pre-production examples designated as "Me 163 A-0".

Landing gear and ground handling procedures
During testing, the jettisonable main landing gear arrangement, of a differing design to that used on the later B-series production aircraft, was a serious problem. The A-series "dolly" landing gear caused many aircraft to be damaged on takeoff when the wheels rebounded and crashed into the aircraft due to the sizable springs and shock absorbers on the A-series "dolly" devices which possessed well-sprung independent suspension systems for each main wheel, not used on the much simpler, crossbeam-axled B-series aircraft dollies. The landing skid on the B-series Komet design possessed a oleo-pneumatic strut for the extendable skid, which had to remain extended after attachment of the dolly to absorb ground-running impacts during the takeoff run and for shock absorption on landing. If the hydraulic cylinder was malfunctioning—or if the pilot simply forgot to release the hydraulic pressure on the skid before landing, after extending it for touchdown to absorb the force of the landing itself—the resulting unbuffered impact of a hard touchdown on the skid could cause back injuries to the pilot when landing.

Once on the ground, the aircraft had to be retrieved by a Scheuch-Schlepper, a converted small agricultural vehicle, originally based on the concept of the two-wheel tractor, carrying a detachable third swiveling wheel at the extreme rear of its design for stability in normal use—this swiveling third wheel was replaced with a pivoting, special retrieval trailer that rolled on a pair of short, triple-wheeled continuous track setups (one per side) for military service wherever the Komet was based. This retrieval trailer usually possessed twin trailing lifting arms, that lifted the stationary aircraft off the ground from under each wing. Another form of trailer, known also to have been trialled with the later B-series examples, was tried during the Komet's test phase, which used a pair of sausage-shaped air bags in place of the lifting arms and could also be towed by the Scheuch-Schlepper tractor, inflating the air bags to lift the aircraft. The three-wheeled Scheuch-Schlepper tractor used for the task was originally meant for farm use, but such a vehicle with a specialized trailer was required as the Komet was unpowered after exhausting its rocket propellants, and lacked main wheels after landing, from the jettisoning of its "dolly" main gear at takeoff. The slightly larger Sd Kfz 2 Kettenkrad half-track motorcycle, known to be used with the Me 262 jet fighter for ground handling needs, and documented as also being used with the Arado Ar 234B jet recon-bomber, was not known to have ever been used for ground handling operations with the Komet at any time.

During flight testing, the superior gliding capability of the Komet proved detrimental to safe landing. As the now un-powered aircraft completed its final descent, it could rise back into the air with the slightest updraft. Since the approach was unpowered, there was no opportunity to make another landing pass. For production models, a set of landing flaps allowed somewhat more controlled landings. This issue remained a problem throughout the program. Nevertheless, the overall performance was tremendous, and plans were made to put Me 163 squadrons all over Germany in 40-kilometre rings (25 mi) around any potential target. Development of an operational version was given the highest priority.

Me 163B
A simplified construction format for the Me 163 fighter's airframe was deemed necessary, as the Me 163A version was not truly optimized for large-scale production, with design work starting in December 1941. The result was the Me 163B subtype, which had the desired, more mass-producible fuselage, wing panel, retractable landing skid and tailwheel designs with the previously mentioned unsprung "dolly" takeoff gear, and a generally one-piece conical nose for the forward fuselage which could incorporate a "windmill" generator for supplementary electrical power while in flight, as well as a one-piece, perimeter frame-only hinged canopy for ease of production.

Meanwhile, Walter had started work on the newer HWK 109-509 bipropellant hot engine, which added a true fuel of hydrazine hydrate and methanol, designated C-Stoff, that burned with the oxygen-rich exhaust from the T-Stoff, used as the oxidizer, for added thrust (see: List of Stoffs). The new powerplant and numerous detail design changes meant to simplify production over the general A-series airframe design resulted in the significantly modified Me 163B of late 1941. Due to the Reichsluftfahrtministerium (RLM) requirement that it should be possible to throttle the engine, the original power plant grew complicated and lost reliability.

The fuel system was particularly troublesome, as leaks incurred during hard landings easily caused fires and explosions. Metal fuel lines and fittings, which failed in unpredictable ways, were used as this was the best technology available. Both fuel and oxidizer were toxic and required extreme care when loading in the aircraft, yet there were occasions when Komets exploded on the tarmac from the propellants' hypergolic nature. Both propellants were clear fluids, and different tanker trucks were used for delivering each propellant to a particular Komet aircraft, usually the C-Stoff hydrazine/methanol-base fuel first. For safety purposes, it left the immediate area of the aircraft following its delivery and capping off of the Komet's fuel tanks from a rear located dorsal fuselage filling point just ahead of the Komet's vertical stabilizer. Then, the other tanker truck carrying the very reactive T-Stoff hydrogen peroxide oxidizer would deliver its load through a different filling point on the Komet's dorsal fuselage surface, located not far behind the rear edge of the canopy.

The corrosive nature of the liquids, especially for the T-Stoff oxidizer, required special protective gear for the pilots. To help prevent explosions, the engine and the propellant storage and delivery systems were frequently and thoroughly hosed down and flushed with water run through the propellant tanks and the rocket engine's propellant systems before and after flights, to clean out any remnants. The relative "closeness" to the pilot of some 120 litres (31.7 US gal) of the chemically active T-Stoff oxidizer, split between two auxiliary oxidizer tanks of equal volume to either side within the lower flanks of the cockpit area—besides the main oxidizer tank of some 1,040 litre (275 US gal) volume just behind the cockpit's rear wall, could present a serious or even fatal hazard to a pilot in a fuel-caused mishap.

Two prototypes were followed by 30 Me 163 B-0 pre-production aircraft armed with two 20 mm MG 151/20 cannon and some 400 Me 163 B-1 production aircraft armed with two 30 mm (1.18 inch) MK 108 cannons, but which were otherwise similar to the B-0. Early in the war, when German aircraft firms created versions of their aircraft for export purposes, the a was added to export (ausland) variants (B-1a) or to foreign-built variants (Ba-1) but for the Me 163, there were neither export nor a foreign-built version. Later in the war, the "a" and successive letters were used for aircraft using different engine types: as Me 262 A-1a with Jumo engines, Me 262 A-1b with BMW engines. As the Me 163 was planned with an alternative BMW P3330A rocket engine, it is likely the "a" was used for this purpose on early examples. Only one Me 163, the V10, was tested with the BMW engine, so this designation suffix was soon dropped. The Me 163 B-1a did not have any wingtip "washout" built into it, and as a result, it had a much higher critical Mach number than the Me 163 B-1.

The Me 163B had very docile landing characteristics, mostly due to its integrated leading edge slots, located directly forward of the elevon control surfaces, and just behind and at the same angle as the wing's leading edge. It would neither stall nor spin. One could fly the Komet with the stick full back, and have it in a turn and then use the rudder to take it out of the turn, and not fear it snapping into a spin. It would also slip well. Because the Me 163B's airframe design was derived from glider design concepts, it had excellent gliding qualities, and the tendency to continue flying above the ground due to ground effect. On the other hand, making a too close turn from base onto final, the sink rate would increase, and one could quickly lose altitude and come in short. Another main difference from a propeller-driven aircraft is that there was no slipstream over the rudder. On takeoff, one had to attain the speed at which the aerodynamic controls become effective—about 129 km/h (80 mph)—and that was always a critical factor. Pilots accustomed to flying propeller-driven aircraft had to be careful the control stick was not somewhere in the corner when the control surfaces began working. These, like many other specific Me 163 problems, would be resolved by specific training.

The performance of the Me 163 far exceeded that of contemporary piston engine fighters. At a speed of over 320 km/h (200 mph) the aircraft would take off, in a so-called "scharfen start" ("sharp start", with "start" being the German word for "take-off") from the ground, from its two-wheeled dolly. The aircraft would be kept at level flight at low altitude until the best climbing speed of around 676 km/h (420 mph) was reached, at which point it would jettison the dolly, retract its extendable skid using a knob-topped release lever just forward of the throttle (as both levers were located atop the cockpit's portside 120 litre T-Stoff oxidizer tank) that engaged the aforementioned pneumatic cylinder, and then pull up into a 70° angle of climb, to a bomber's altitude. It could go higher if required, reaching 12,000 m (39,000 ft) in an unheard of three minutes. Once there, it would level off and quickly accelerate to speeds around 880 km/h (550 mph) or faster, which no Allied fighter could match. The usable Mach number was similar to that of the Me 262, but because of the high thrust-to-drag ratio, it was much easier for the pilot to lose track of the onset of severe compressibility and risk loss of control. A Mach warning system was installed as a result. The aircraft was remarkably agile and docile to fly at high speed. According to Rudolf Opitz, chief test pilot of the Me 163, it could "fly circles around any other fighter of its time".

By this point, Messerschmitt was completely overloaded with production of the Messerschmitt Bf 109 and attempts to bring the Me 210 into service. Production in a dispersed network was handed over to Klemm, but quality control problems were such that the work was later given to Junkers, who were, at that time, underworked. As with many German designs of World War II's later years, parts of the airframe (especially the wings) were made of wood by furniture manufacturers. The older Me 163A and first Me 163B prototypes were used for training. It was planned to introduce the Me 163S, which removed the rocket engine and tank capacity and placed a second seat for the instructor above and behind the pilot, with his own canopy. The Me 163S would be used for glider landing training, which as explained above, was essential to operate the Me 163. It appears the 163Ss were converted from the earlier Me 163B series prototypes.

In service, the Me 163 turned out to be difficult to use against enemy aircraft. Its tremendous speed and climb rate meant a target was reached and passed in a matter of seconds. Although the Me 163 was a stable gun platform, it required excellent marksmanship to bring down an enemy bomber. The Komet was equipped with two 30 mm (1.18 inch) MK 108 cannons which had a relatively low muzzle velocity of 540 meters per second (1,772 feet/sec), and were accurate only at short range, making it almost impossible to hit a slow moving bomber. Four or five hits were typically needed to take down a B-17.

A number of innovative solutions were implemented to ensure kills by less experienced pilots. The most promising was a unique weapon called the Sondergerät 500 Jägerfaust. This consisted of a series of single-shot, short-barreled 50 mm (2 inch) guns pointing upwards, akin to Schräge Musik. Five were mounted in the wing roots on each side of the aircraft. The trigger was tied to a photocell in the upper surface of the aircraft, and when the Komet flew under the bomber, the resulting change in brightness caused by the underside of the aircraft could cause the rounds to be fired. As each shell shot upwards, the disposable gun barrel that fired it was ejected downwards, thus making the weapon recoilless. It appears that this weapon was used in combat only once, resulting in the destruction of a bomber.