Sunday, 27 September 2015

Messerschmitt Me163 Komet. Part 2: Versions - Compiler Luis German Dzib Aguilar.

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 project to produce a small two-passenger light aircraft, which had unsuccessfully competed against the winning Fieseler Fi 156 Storch for a production contract. 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 on 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. (5)(6) Some postwar aviation history publications stated that the Me 163A V3 was thought to have set the record. (7)

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". (6) Some doubt once existed about the Stammkennzeichen code assigned to the Me 163A V4 prototype - at one time it was thought to have used the code CD+IM (also speculated to be the A V3's code), but later re-examination of available Luftwaffe records indicated that the sixth through 13th A-series prototypes were assigned the Stammkennzeichen code block of "CD+IK" through "CD+IR", confirming the "KE+SW" designation for the V4 airframe. (8) .

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, (9) not used on the much simpler, crossbeam-axled B-series aircraft dollies. Malfunctioning hydraulic dampers in the skid — or with the pilot simply forgetting to release the hydraulic pressure on the skid before landing, after extending it for touchdown to absorb the force of the landing itself — could cause back injuries to the pilot when landing, as the aircraft lacked steering or braking control during landing, and was unable to avoid obstacles.Once on the ground, the aircraft had to be retrieved by a Scheuch-Schlepper, a converted small agricultural vehicle towing a special retrieval trailer that rolled on a pair of short, triple-wheeled continuous track setups (one per side), with twin trailing lifting arms, that lifted the stationary aircraft off the ground from under each wing. (10) 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. (11)(10)

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. (12)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 flapsallowed 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 163A

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" take off  gear, and a generally one-piece nose for the forward fuselage which could incorporate a pioneering example of a "windmill" generator at the extreme front 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 andmethanol, 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, with different tanker trucks used for delivering each propellant to a particular Komet aircraft, one at a time, with one truck - usually the one delivering the C-Stoff hydrazine/methanol-base fuel - being the first tanker vehicle to service the aircraft. 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 - most often an Opel Blitz tanker truck, of a special Ausführung S model carrying the very reactive T-Stoff hydrogen peroxide oxidizer would come anywhere near to deliver its oxidizer load to the fighter for safety reasons, through a different filling point on the Komet's dorsal fuselage surface, located not far behind the rear edge of the canopy. (13)
The corrosive nature of the liquids, especially for the T-Stoff oxidizer, required special protective gear for the pilots. To help prevent explosions, the Walter rocket engine and theKomet's propellant storage and delivery systems were frequently and thoroughly hosed down and flushed with water run through both the fuel and oxidizer tanks and rocket engine's propellant systems before and after flights, to clean out any remnants of the hypergolic fuel and oxidizer.[17] 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 with the Me 163B. (14) 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. Occasional references to B-1a or Ba-1 subtypes are found in the literature on the aircraft, but the meanings of these designations are somewhat unclear. Early in the war, when German aircraft firms created versions of their aircraft for export purposes, that 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 quite safe to assume 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 numberthan the Me 163 B-1. (15) 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 solidly derived from glider design concepts, it had excellent gliding qualities, and had 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 used 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 and pull up into a 70° angle of climb, heading upwards rapidly 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 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 its 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 163 Ss 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 (1,207 mph, 1,944 km/h), with the characteristic ballistic drop of such a weapon. The drop meant they were only accurate at short distance, and that it was almost impossible to hit a slow moving bomber when the Komet was traveling very fast. 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. 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 Halifax bomber, although other sources say it was a Boeing B-17. (16)(17)(18)

Later verions

The biggest concern about the design was the short flight time, which never met the projections made by Walter. With only seven and a half minutes of powered flight, the fighter truly was a dedicated point defense interceptor. To improve this, the Walter firm began developing two more advanced versions of the 509A rocket engine, the 509B and C, each with two separate combustion chambers of differing sizes, one above the other, with greater efficiency. (19) The B-version possessed a main combustion chamber with an exterior shape much like that on the single chamber 509A version, with the C-version having a forward chamber shape of a more cylindrical nature, designed for a higher top thrust level of some 2,000 kg (4,410 lb) of thrust, while simultaneously dropping the use of the cubic-shape "frame" for the forward engine propellant flow/turbopump mechanisms as used by the earlier -A and -B versions. (20)(21) The 509B and 509C rocket motors' main combustion chambers were supported by the "thrust tube" exactly as the 509A motor's single chamber had been. They were tuned for "high power" for takeoff and climb. The added, smaller volume "lower" chamber on the two later models, nicknamed the Marschofen with approximately 400 kg (880 lb) of thrust at its top performance level, was intended for more efficient, lower power cruise flight. These HWK 109–509B and C motors would improve endurance by as much as 50%. Two 163 Bs, models V6 and V18, were experimentally fitted with the lower-thrust B-version of the new twin-chamber engine, a retractable tailwheel, and tested in spring 1944.(19)(22) The main combustion chamber of the 509B engine used for the B V6 and V18 occupied the same location as the A-series' engine did, with the lower Marschofen "cruise chamber" housed within the retractable tailwheel's appropriately widened ventral tail fairing. On 6 July 1944, the Me 163B V18 (VA+SP), like the B V6 basically a standard production Me 163B airframe outfitted with the new-twin chamber "cruiser" rocket motor with the aforementioned modifications beneath the original rocket motor orifice to accept the extra combustion chamber, set a new unofficial world speed record of 1,130 km/h (702 mph), piloted by Heini Dittmar, and landed with almost all of the vertical rudder surface broken away from flutter. (5)(23)(24) This record was not broken in terms of absolute speed until 6 November 1947 by Chuck Yeager in flight number 58 that was part of the Bell X-1 test program, with a 1,434 km/h (891 mph), or Mach 1.35 supersonic speed, recorded at an altitude of nearly 14,820 m (48,620 ft).The X-1 never exceeded Dittmar's speed from a normal runway "scharfen-Start" liftoff. Heini Dittmar had reached the 1,130 km/h (702 mph) performance, after a normal "sharp start" ground takeoff, without an air drop from a mother ship. Neville Duke exceeded Heini Dittmar's record mark in 31 August 1953, with the Hawker Hunter F Mk3 at a speed of 1,171 km/h (728 mph), after a normal ground start. (25) Postwar experimental aircraft of the aerodynamic configuration that the Me 163 used, were found to have serious stability problems when entering transonic flight, like the similarly configured, and turbojet powered, Northrop X-4 Bantam and de Havilland DH 108, which made the V18's record with the Walter 509B "cruiser" rocket motor more remarkable.Waldemar Voigt of Messerschmitt's Oberammergau project and development offices started a redesign of the 163 to incorporate the new twin-chamber Walter rocket engine, as well as fix other problems. The resulting Me 163C design featured a larger wing through the addition of an insert at the wing root, an extended fuselage with extra tank capacity through the addition of a "plug" insert behind the wing, and a new pressurized cockpit topped with a bubble canopy for improved visibility, on a fuselage that had dispensed with the earlier B-version's dorsal fairing. The additional tank capacity and cockpit pressurization allowed the maximum altitude to increase to 15,850 m (52,000 ft), as well as improving powered time to about 12 minutes, almost doubling combat time (from about five minutes to nine). Three Me 163 C-1a prototypes were planned, but it appears only one was flown, without its intended engine. (26) By this time the project was moved to Junkers. There, a new design effort under the direction of Heinrich Hertel at Dessau attempted to improve the Komet. The Hertel team had to compete with the Lippisch team and their Me 163C. Hertel investigated the Me 163 and found it was not well suited for mass production and not optimized as a fighter aircraft, with the most glaring deficiency being the lack of retractable landing gear. To accommodate this, what would eventually become the Me 263 V1 prototype would be fitted with the desired tricycle gear, also accommodating the twin-chamber Walter rocket from the start — later it was assigned to the Ju 248 program. (27)(28) The resulting Junkers Ju 248 used a three-section fuselage to ease construction. The V1 prototype was completed for testing in August 1944, and was glider-tested behind a Junkers Ju 188. Some sources state that the Walter 109–509C engine was fitted in September, but it was probably never tested under this power. At this point the RLM reassigned the project to Messerschmitt, where it became the Messerschmitt Me 263. This appears to have been a formality only, with Junkers continuing the work and planning production. (29) By the time the design was ready to go into production, the plant where it was to be built was overrun by Soviet forces. While it did not reach operational status, the work was briefly continued by the Soviet Mikoyan-Gurevich (MiG) design bureau as the Mikoyan-Gurevich I-270. (30)