Tuesday, October 27, 2009

The Bell X-1


The Bell X-1, originally designated XS-1, was a joint NACA-U.S. Army Air Forces/US Air Force supersonic research project and the first aircraft to exceed the speed of sound in controlled, level flight. This resulted in the first of the so-called X-planes, an American series of experimental aircraft designated for testing of new technologies and usually kept highly secret.

On 16 March 1945, the United States Army Air Forces' Flight Test Division and the National Advisory Committee for Aeronautics (NACA) (now NASA) contracted Bell Aircraft to build three XS-1 (for "Experimental, Supersonic", later X-1) aircraft to obtain flight data on conditions in the transonic speed range.  The XS-1 was the first high-speed aircraft built purely for aviation research purposes and was never intended for production.[citation needed]

The X-1 was in principle a "bullet with wings" that closely resembled the shape of the Browning .50-caliber (12.7 mm) machine gun bullet that was known to be stable in supersonic flight  The pattern shape was followed to the point of seating the pilot behind a sloped, framed window inside a confined cockpit in the nose. After the aircraft ran into compressibility problems in 1947, it was modified to feature a variable-incidence tailplane. An all-moving tail was developed by the British for the Miles M.52, and first saw actual transonic flight on the Bell X-1; ] that allowed it to pass through the sound barrier safely.

The rocket propulsion system was a four-chamber engine built by Reaction Motors, Inc., one of the first companies to build liquid-propellant rocket engines in America. It burned ethyl alcohol diluted with water and liquid oxygen. The thrust could be changed in 1500 lbf increments by firing one or more of the chambers. The fuel and oxygen tanks for the first two X-1 engines were pressurized with nitrogen and the rest with steam-driven turbopumps. The all-important fuel turbopumps, necessary to raise the chamber pressure and thrust, while lightening the engine, were built by Robert Goddard who was under Navy contract to provide jet-assisted takeoff rockets.

Bell Aircraft Chief Test Pilot, Jack Woolams became the first to fly the XS-1, in a glide flight over Pinecastle Army Airfield, in Florida, on 25 January 1946. Woolams would complete nine additional glide flights over Pinecastle before March 1946, when the #1 aircraft was returned to Bell for modifications in anticipation of the powered flight tests, planned for Muroc Army Air Field (now Edwards Air Force Base) in California. Following Woolams' death on 30 August 1946, Chalmers "Slick" Goodlin was the primary Bell Aircraft test pilot of X-1-1 (serial 46-062). He made 26 successful flights in both of the X-1 aircraft from September 1946 until June 1947.

The Army Air Force was unhappy with the cautious pace of flight envelope expansion and Bell Aircraft's flight test contract for aircraft #46-062 was terminated and was taken over by the Army Air Force Flight Test Division on 24 June after months of negotiation. Goodlin had demanded a US$150,000 bonus for breaking the sound barrier.  Flight tests of the X-1-2 (serial 46-063) would be conducted by NACA to provide design data for later production high-performance aircraft.

On 14 October 1947, just under a month after the United States Air Force had been created as a separate service, the tests culminated in the first manned supersonic flight, piloted by Air Force Captain Charles "Chuck" Yeager in aircraft #46-062, which he had christened ‘Glamorous Glennis’, after his wife. The rocket-powered aircraft was launched from the bomb bay of a specially modified B-29 and glided to a landing on a runway. XS-1 flight number 50 is the first one where the X-1 recorded supersonic flight, at Mach 1.06 (361 m/s, 1,299 km/h, 807.2 mph) peak speed; however, Yeager and many other personnel believe Flight #49 (also with Yeager piloting), which reached a top recorded speed of Mach 0.997 (339 m/s, 1,221 km/h), may have, in fact, exceeded Mach 1.[citation needed] (The measurements were not accurate to three significant figures and no sonic boom was recorded for that flight.)

As a result of the X-1's initial supersonic flight, the National Aeronautics Association voted its 1948 Collier Trophy to be shared by the three main participants in the program. Honored at the White House by President Harry S. Truman were Larry Bell for Bell Aircraft, Captain Yeager for piloting the flights, and John Stack for the NACA contributions.

The research techniques used in the X-1 program became the pattern for all subsequent X-craft projects. The NACA X-1 procedures and personnel also helped lay the foundation of America's space program in the 1960s. The X-1 project defined and solidified the post-war cooperative union between U.S. military needs, industrial capabilities, and research facilities. The flight data collected by the NACA in the X-1 tests then provided a basis for American aviation supremacy in the latter half of the 20th century.

Aircraft #46-062 is currently on display in the Milestones of Flight gallery of the National Air and Space Museum in Washington, DC, alongside the Spirit of St. Louis and SpaceShipOne. Aircraft #46-063, now the X-1E, is on display in front of the NASA Dryden Flight Research Center headquarters building.

X-1A

Ordered by the Air Force on 2 April 1948, the X-1A (serial 48-1384) was intended to investigate aerodynamic phenomena at speeds above Mach 2 (681 m/s, 2,451 km/h) and altitudes greater than 90,000 ft (27 km), specifically focusing on dynamic stability and air loads. Longer and heavier than the original X-1, with a bubble canopy for better vision, the X-1A was powered by the same Reaction Motors XLR-11 rocket engine. The aircraft first flew, unpowered, on 14 February 1953 at Edwards AFB, with the first powered flight on 21 February. Both flights were piloted by Bell test pilot Jean Ziegler.

After NACA started its high-speed testing with the Douglas Skyrocket, culminating in Scott Crossfield achieving Mach 2.005 on 20 November 1953, the Air Force started a series of tests with the X-1A, which the test pilot of the series, Chuck Yeager, named "Operation NACA Weep". These culminated on 12 December 1953, when Yeager achieved an altitude of 74,700 feet (22,770 m) and a new air speed record of Mach 2.44 (equal to 1620 mph, 724.5 m/s, 2608 km/h at that altitude). Unlike Crossfield in the Skyrocket, Yeager achieved that in level flight. Shortly after, the aircraft spun out of control, due to the then not yet understood phenomenon of inertia coupling. The X-1 dropped from maximum altitude to 25,000 feet (7,620 m), exposing the pilot to accelerations of up to 8g, during which Yeager broke the canopy with his helmet before regaining control.

The aircraft was transferred to NACA in September 1954. Following modifications, including the installation of an ejection seat, the aircraft was lost on 8 August 1955 while being prepared for launch from the RB-50 mothership, becoming the first of many early X-planes that would be lost to explosions.

Douglas Skyrocket (D-558-2 or D-558-II


The Douglas Skyrocket (D-558-2 or D-558-II) was a rocket and jet-powered supersonic research aircraft built by the Douglas Aircraft Company for the United States Navy. On 20 November 1953, shortly before the 50th anniversary of powered flight, Scott Crossfield piloted the Douglas D-558-2 Skyrocket to Mach 2, or more than 1,290 mph (2076 km/h), the first time an aircraft had exceeded twice the speed of sound.

The "-2" in the aircraft's designation referred to the fact that the Skyrocket was the phase-two version of what had originally been conceived as a three-phase program. The phase-one aircraft, the D-558-1, was jet powered and had straight wings. The third phase, which never came to fruition, would have involved constructing a mock-up of a combat type aircraft embodying the results from the testing of the phase one and two aircraft. The eventual D-558-3 design, which was never built, was for a hypersonic aircraft similar to the North American X-15.[1].

When it became obvious that the D558-1 fuselage could not be modified to accommodate both rocket and jet power, the D558-2 was conceived as an entirely different aircraft[2]. A contract change order was issued on 27 January 1947 to formally drop the final three D558-1 aircraft and substitute three new D558-2 aircraft instead[3].

The Skyrocket featured wings with a 35-degree sweep and horizontal stabilizers with 40-degree sweep. The wings and empennage were fabricated from aluminum and the large fuselage was of primarily magnesium construction. The Skyrocket was powered by a Westinghouse J34-40 turbojet engine fed through side intakes in the forward fuselage. This engine was intended for takeoff, climb and landing. For high speed flight, a four-chamber Reaction Motors LR8-RM-6 engine (the Navy designation for the Air Force's XLR-11 used in the Bell X-1), was fitted. This engine was rated at 6,000 lbf (27 kN) static thrust at sea level. A total of 250 gallons (946 liters) of aviation fuel, 195 gallons of alcohol, and 180 gallons of liquid oxygen were carried in fuselage tanks.

The Skyrocket was configured with a flush cockpit canopy, but visibility from the cockpit was poor, so it was re-configured with a raised cockpit with conventional angled windows. This resulted in a greater profile area at the front of the aircraft, which was balanced by an additional 14 inches (36 cm) of height added to the vertical stabilizer. Like its predecessor, the D558-1, the D558-2 was designed so that the forward fuselage, including cockpit, could be separated from the rest of the aircraft in an emergency. Once the forward fuselage had decelerated sufficiently, the pilot would then be able to escape from the cockpit by parachute.

General characteristics
  • Crew: one pilot
  • Length: 42 ft 0 in (12.8 m)
  • Wingspan: 25 ft 0 in (7.6 m)
  • Height: 22 ft 8 in (3.8 m)
  • Wing area: 175 ft² (16.2 m²)
  • Empty weight: 9,421 lb (4,273 kg)
  • Max takeoff weight: 15,266 lb (6,923 kg)
  • Powerplant:
    • 1× Westinghouse J34-WE-40 turbojet, 3,000 lbf (13 kN)
    • 1× Reaction Motors XLR-8-RM-5 rocket engine, 6,000 lbf (27 kN)
Performance
  • Maximum speed: 720 mph, 1,250 mph when air-launched (1,160 km/h, 2,010 km/h when air-launched)
  • Stall speed: 160.1 mph (257.7 km/h)
  • Service ceiling: 16,500 ft (5,030 m)
  • Rate of climb: 22,400 ft/min, 11,100 ft/min under rocket power only (6,830 m/min., 3,380 m/min under rocket power only)
  • Wing loading: 87.2 lb/ft² (426 kg/m²)
  • Thrust/weight (jet): 0.39

Thursday, October 22, 2009

The Whitcomb area rule


The Whitcomb area rule, also called the transonic area rule, is a design technique used to reduce an aircraft's drag at transonic and supersonic speeds, particularly between Mach 0.8 and 1.2. This is the operating speed range of the majority of commercial and military fixed-wing aircraft today.
At high-subsonic flight speeds, supersonic airflow can develop in areas where the flow accelerates around the aircraft body and wings. The speed at which this occurs varies from aircraft to aircraft, and is known as the critical Mach number. The resulting shock waves formed at these points of supersonic flow can bleed away a considerable amount of power, which is experienced by the aircraft as a sudden and very powerful form of drag, called wave drag. To reduce the number and power of these shock waves, an aerodynamic shape should change in cross sectional area as smoothly as possible. This leads to a "perfect" aerodynamic shape known as the Sears-Haack body, roughly shaped like a cigar but pointed at both ends.

The area rule says that an airplane designed with the same cross-sectional area as the Sears-Haack body generates the same wave drag as this body, largely independent of the actual shape. As a result, aircraft have to be carefully arranged so that large volumes like wings are positioned at the widest area of the equivalent Sears-Haack body, and that the cockpit, tailplane, intakes and other "bumps" are spread out along the fuselage and or that the rest of the fuselage along these "bumps" is correspondingly thinned.

The area rule also holds true at speeds higher than the speed of sound, but in this case the body arrangement is in respect to the Mach line for the design speed. For instance, at Mach 1.3 the angle of the Mach cone formed off the body of the aircraft will be at about μ = arcsin (1/M) = 50,3 deg (μ is the sweep angle of the Mach cone). In this case the "perfect shape" is biased rearward, which is why aircraft designed for high speed cruise tend to be arranged with the wings at the rear. A classic example of such a design is Concorde.

The area rule was discovered by Otto Frenzl when comparing a swept wing with a w-wing with extreme high wave drag   working on a transonic wind tunnel at Junkers works in Germany between 1943 and 1945. He wrote a description on 17 December 1943, with the title “Arrangement of Displacement Bodies in High-Speed Flight”; this was used in a patent filed in 1944. The results of this research were presented to a wide circle in March 1944 by Theodor Zobel at the “Deutsche Akademie der Luftfahrtforschung” (German Academy of aeronautics research) in the lecture “Fundamentally new ways to increase performance of high speed aircraft.”  The design concept was applied to German wartime aircraft, including a rather odd Messerschmitt project, but their complex double-boom design was never built even to the extent of a model. Several other researchers came close to developing a similar theory, notably Dietrich Küchemann who designed a tapered fighter that was dubbed the “Küchemann Coke Bottle” when it was discovered by U.S. forces in 1946. In this case Küchemann arrived at the solution by studying airflow, notably spanwise flow, over a swept wing. The swept wing is already an application of the area rule.
Wallace D. Hayes, a pioneer of supersonic flight, developed the supersonic area rule in publications beginning in 1947 with his Ph.D. thesis at the California Institute of Technology.

Richard T. Whitcomb, after whom the rule is named, independently discovered this rule in 1952, while working at the NACA. While using the new Eight-Foot High-Speed Tunnel, a wind tunnel with performance up to Mach 0.95 at NACA's Langley Research Center, he was surprised by the increase in drag due to shock wave formation. The shocks could be seen using Schlieren photography, but the reason they were being created at speeds far below the speed of sound, sometimes as low as Mach 0.70, remained a mystery.

In late 1951, the lab hosted a talk by Adolf Busemann, a famous German aerodynamicist who had moved to Langley after World War II. He talked about the difference in the behavior of airflow at speeds approaching the supersonic, where it no longer behaved as an incompressible fluid. Whereas engineers were used to thinking of air flowing smoothly around the body of the aircraft, at high speeds it simply did not have time to "get out of the way", and instead started to flow as if it were rigid pipes of flow, a concept Busemann referred to as "streampipes", as opposed to streamlines, and jokingly suggested that engineers had to consider themselves "pipefitters".

Several days later Whitcomb had a "Eureka" moment. The reason for the high drag was that the "pipes" of air were interfering with each other in three dimensions. One could not simply consider the air flowing over a 2D cross-section of the aircraft as others could in the past; now they also had to consider the air to the "sides" of the aircraft which would also interact with these streampipes. Whitcomb realized that the Sears-Haack shaping had to apply to the aircraft as a whole, rather than just to the fuselage. That meant that the extra cross-sectional area of the wings and tail had to be accounted for in the overall shaping, and that the fuselage should actually be narrowed where they meet to more closely match the ideal.

The area rule was immediately applied to a number of development efforts. One of the most famous was Whitcomb's personal work on the re-design of the Convair F-102 Delta Dagger, a U.S. Air Force jet fighter that was demonstrating performance considerably worse than expected. By indenting the fuselage beside the wings, and (paradoxically) adding more volume to the rear of the plane, transonic drag was considerably reduced and the original Mach 1.2 design speeds were reached. The culminating design of this research was the Convair F-106 Delta Dart, an aircraft which for many years was the USAF's primary all-weather interceptor.

Numerous designs of the era were likewise modified in this fashion, either by adding new fuel tanks or tail extensions to smooth out the profile. The Tupolev Tu-95 'Bear', a Soviet-era bomber, was modified by adding large bulged nacelles behind the two inner engines, instead of decreasing the cross section of the fuselage next to the wing root. It remains the highest speed propeller aircraft in the world. The Convair 990 used a similar solution, adding bumps called antishock bodies to the trailing edge of the upper wing. The 990 remains the fastest U.S. airliner in history, cruising at up to Mach 0.89. Designers at Armstrong-Whitworth took the concept a step further in their proposed M-Wing, in which the wing was first swept forward and then to the rear. This allowed the fuselage to be narrowed on either side of the root instead of just behind it, leading to a smoother fuselage that remained wider on average than one using a classic swept wing.

One interesting outcome of the area rule is the shaping of the Boeing 747's upper deck. The aircraft was designed to carry standard cargo containers in a two-wide, two-high stack on the main deck, which was considered a serious accident risk for the pilots if they were located in a cockpit at the front of the aircraft. They were instead moved above the deck in a small "hump", which was designed to be as small as possible given normal streamlining principles. It was later realized that the drag could be reduced much more by lengthening the hump, using it to reduce wave drag offsetting the tail surface's contribution. The new design was introduced on the 747-300, improving its cruise speed and lowering drag.

Aircraft designed according to Whitcomb's area rule looked odd at the time they were first tested, (eg. the Blackburn Buccaneer), and were dubbed "flying Coke bottles," but the area rule is effective and came to be an expected part of the appearance of any transonic aircraft. Later designs started with the area rule in mind, and came to look much more pleasing. Although the rule still applies, the visible fuselage "waisting" can only be seen on the B-1B Lancer, Learjet 60, and the Tupolev Tu-160 'Blackjack' — the same effect is now achieved by careful positioning of aircraft components, like the boosters and cargo bay on rockets; the jet engines in front of (and not directly below) the wings of the Airbus A380; the jet engines behind (and not purely at the side of) the fuselage of a Cessna Citation X; the shape and location of the canopy on the F-22 Raptor; and the image of the Airbus A380 above showing obvious area rule shaping at the wing root, which is practically invisible from any other angle. Aftershock bodies are likewise mostly "invisible" today, often serving double-duty as flap actuators, which are also visible on the A380.

Tuesday, October 20, 2009

The Rolls-Royce Thrust Measuring Rig


The Rolls-Royce Thrust Measuring Rig (TMR) was a pioneering vertical take-off and landing aircraft developed by Rolls-Royce in the 1950s. The TMR used two Nene turbojet engines mounted back-to-back horizontally within a steel framework, raised upon four legs with castors for wheels. The TMR had no lifting surfaces (wings, blades, etc.) and was understandably nicknamed the Flying Bedstead.

The output of the jets was directed towards the centre of the rig with one jetpipe discharging downwards through a central nozzle while the other jet discharged downwards through two smaller nozzles on either side. Four outrigger arms extended out from the rig, one on either side and one each at the front and rear, through which compressed air was released for control in roll, pitch and yaw when in flight. The purpose of the rig was, as the name suggests, to test turbojet engines for lifting purposes and to develop techniques for controlling such an aircraft.

The man largely responsible for the development of the TMR was Dr Alan Arnold Griffith who had worked on gas turbine design at the Royal Aircraft Establishment in the 1920s and was a pioneer of jet lift technology. Griffith was employed by Rolls-Royce in 1939.

Two Thrust Measuring Rigs were built with the first taking to the air on 3 July 1953 at Hucknall Aerodrome, Nottinghamshire, England, though it remained tethered to the ground while airborne. The first free flight by the TMR was made on 3 August 1954 with R.T. Shepherd, Rolls-Royce's chief test pilot, at the controls. The TMR had only marginal excess power and flying was tricky due to this, combined with the slow throttle response of the engines, and a considerably degree of anticipation in the use of engine power was required in order to prevent overshooting of desired altitude, and to ensure a gentle touchdown when landing. As the TMR possessed no inherent stability, it incorporated an automatic stabiliser system.

Following successful trials of the TMR, Rolls-Royce began development of the Rolls-Royce RB.108 direct-lift turbojet, five of which were used to power the first true British VTOL aircraft, the Short SC.1.

The second Thrust Measuring Rig (Serial XK426) was destroyed in 1957 but the first (Serial XJ314) is preserved and on public display at the Science Museum in London, England.

Thursday, October 8, 2009

Bristol Britannia

Bristol Britannia



Type 175 Britannia

Royal Air Force Bristol Britannia Spica in 1964.
Role
Airliner
Manufacturer
Bristol Aeroplane Company
First flight
16 August 1952
Introduced
1957
Retired
1975
Primary users
British Overseas Airways Corporation

Royal Air Force
Number built
85
Variants
Canadair Argus

Canadair CL-44
The Bristol Type 175 Britannia was a British medium/long-range airliner built by the Bristol Aeroplane Company in 1952 to fly across the British Empire. Soon after production the turboprop engines proved susceptible to inlet icing and two prototypes were lost while solutions were found. By the time it was cleared, jets from France, UK and the US were about to enter service and only 85 Britannias were built before production ended in 1960. Nevertheless, the Britannia is considered the high point in turboprop design and was popular with passengers, earning itself the title of "The Whispering Giant" for its quiet and smooth flying.

 

In 1942, during the Second world War, the US and UK agreed to split aircraft construction; the US concentrating on transport aircraft, and the UK on heavy bombers. This left the UK with little experience in transport construction at the end of the war, so in 1943, a committee under Lord Brabazon of Tara, investigated the future of the British civilian airliner market. The Brabazon Committee called for four main types of aircraft.

Bristol won the Type I and Type III contracts, delivering their Type I design, the Bristol Brabazon in 1949. The initial requirement for the Type III, Specification C.2/47, was issued by the Minister of Supply for an aircraft capable of carrying 48 passengers and powered with Bristol Centaurus radial engines. Turboprop and compound engines were also considered, but they were so new that Bristol could not guarantee the performance specifications. After wrangling between the Ministry of Supply and British Overseas Airways Corporation (BOAC) over costs, the go-ahead was given in July 1948 for three prototypes, although the second and third were to be convertible to Bristol Proteus turboprops.

In October, with work already underway, BOAC decided that only a Proteus-engined aircraft was worth working on, and the project was redrawn to allow both turboprop and piston aircraft. BOAC purchased options for 25 aircraft on 28 July 1949, to be powered initially with the Centaurus engine but to be re-fitted with the Proteus when available. The design was now aimed at long-haul Empire and trans-Atlantic routes rather than the medium haul Empire routes originaly planned and had grown to accomodate 83 passengers.

By the time the first prototype, registered G-ALBO, first flew on 16 August 1952 at Filton, BOAC and Bristol had dropped the Centaurus because the turboprop Proteus had shown such promise. The Britannia was now a 90-seater and BOAC ordered 15 of these Series 100s. In 1953 and 54, three de Havilland Comets disappeared without explanation, and the Air Ministry demanded the Britannia undergo lengthy tests. Further, delays were caused by engine problems, mostly related to icing and the loss of the second prototype G-ALRX in an accident caused by a failed engine in December 1953. This delayed the in-service date until February 1957, when BOAC put their first Britannia 102s into service on the London to South Africa route, with Australia following a month later.

Bristol then upgraded the design as a larger transatlantic airliner for BOAC, resulting in the Series 200 and 300. The new version had a fuselage stretch of 10 ft 3 in (3.12 m) and upgraded Proteus engines, and was offered as the all-cargo Series 200, the cargo/passenger (combi) Series 250, and the all-passenger Series 300.

The first public service was operated on the 1 February 1957 with a BOAC flight between London and Johannesburg. By August 1957 the first 15 Series 102 aircraft had been delivered to BOAC.  The last ten aircraft of the order were built as Series 300 aircraft for transatlantic operations.

The first 301 flew on 31 July 1956. BOAC ordered seven Model 302s but never took delivery - instead they were taken on by airlines including Aeronaves de México and Ghana Airways. The main long-range series were the 310s, of which BOAC took 18 and, after deliveries began in September 1957, put them into service between London and New York. The 310 series (318) also saw transatlantic service with Cubana de Aviación starting in 1958. In total 45 Series 300s were built, the first jet-powered, albeit in turboprop form, airliner to enter regular non-stop transatlantic service in both directions.

A further 23 Model 252 and 253 aircraft were purchased by the RAF, as the Britannia C.2 and C.1 respectively. Those in RAF service were allocated the names of stars, "Arcturus", "Sirius", "Vega" etc. The last retired in 1975, and were used by civil operators in Africa, Europe and the Middle East into the late 1990s.

Most aircraft were built by Bristol at Filton Aerodrome but 15 were built at Belfast by Short Brothers and Harland.

A licence was also issued to Canadair to build a maritime reconnaissance aircraft , the Canadair Argus and long-range transport, the Canadair Yukon. Unlike the Britannia, the Argus was built for endurance, not speed, and used four Wright R-3350-32W Turbo-Compound engines which use less fuel at low altitude. The unpressurized interior was left with almost no room to move, packed with sensors and weapons. Canadair also built 37 turboprop Rolls Royce Tyne-powered CL-44 variants for the civil market similar those built for the RCAF in CC-106 Yukon guise, most of which were used as freighters. Four were built as CL-44-Js had their fuselages lengthened, making them the highest capacity passenger aircraft of the day, for service with the Icelandic budget airline Loftleiðir. One, a modified Guppy version, remains airworthy, but not flying. Several were built with swing-tails to allow straight-in cargo loading.

General characteristics
  • Crew: 4-7
  • Capacity: 139 passengers (coach class)
  • Length: 124 ft 3 in (37.88 m)
  • Wingspan: 142 ft 3 in (43.36 m)
  • Height: 37 ft 6 in (11.43 m)
  • Wing area: 2,075 ft² (192.8 m²)
  • Empty weight: 86,400 lb   (38,500 kg)
  • Max takeoff weight: 185,000 lb (84,000 kg)
  • Powerplant: 4× Bristol Proteus 765 turboprops, 4,450 ehp (3,320 kW) each
Performance
  • Maximum speed: 397 mph (345 knots, 639 km/h)
  • Cruise speed: 357 mph (310 kn, 575 km/h) at 22,000 ft (6,700 m)
  • Range: 4,430 mi (3,852 nmi, 7,129 km)
  • Service ceiling: 24,000 ft ] (7,300 m)

Bell X-5

Bell X-5
X-5


Role
Research aircraft
Manufacturer
Bell Aircraft Corporation
Designed by
Robert J. Woods
First flight


20 June 1951

Retired
December 1958
Primary users
United States Air Force

National Advisory Committee for Aeronautics
Number built
2
Developed from
Messerschmitt P.1101
The Bell X-5 was the first aircraft capable of changing the sweep of its wings in flight. It was inspired by the untested wartime P.1101 design of the German Messerschmitt company. In contrast with the German design which could only be adjusted on the ground, the Bell engineers devised a system of electric motors to adjust the sweep in flight.

The incomplete Messerschmitt P.1101 fighter prototype recovered by US troops in 1945 from the experimental facility at Oberammergau, Germany, was brought back to the United States. Although damaged in transit, the innovative fighter prototype was delivered to the Bell factory at Buffalo, New York where company engineering staff studied the design closely and led by Chief Designer Robert J. Wood, submitted a proposal for a similar design.

Although superficially similar, the X-5 was much more complex than the P.1101, with three sweep positions: 20°, 40°, and 60°, creating an in-flight "variable-geometry" platform. A jackscrew assembly moved the wing's hinge along a set of short horizontal rails, using disc brakes to lock the wing into its in-flight positions. Moving from full extension to full sweep took less than 30 seconds. The articulation of the hinge and pivots partly compensated for the shifts in center of gravity and center of pressure as the wings moved.

Even so, the X-5 had vicious spin characteristics arising from the aircraft's flawed aerodynamic layout, particularly a poorly positioned tail and vertical stabilizer, which in some wing positions, could lead to an irrecoverable spin. This violent stall-spin instability would eventually cause the destruction of the second aircraft and the death of its Air Force test pilot in 1953.

The unfavorable spin characteristics also led to the cancellation of tentative plans by the US Air Force to modify the X-5's design into a low-cost tactical fighter for NATO and other foreign countries.

Two X-5s were built (50-1838 and 50-1839). The first was completed 15 February 1951, and the two aircraft made their first flights on 20 June and 10 December 1951. Almost 200 flights were made at speeds up to Mach 0.9 and altitudes of 40,000 ft (12,200 m). One aircraft was lost on 14 October 1953, when it failed to recover from a spin at 60 degree sweepback. USAF Captain Ray Popson died in the crash at Edwards Air Force Base. The other X-5 remained at Edwards and continued active testing until 1955, and remained in service as a chase plane until 1958.

The X-5 successfully demonstrated the advantage of a swing-wing design for aircraft intended to fly at a wide range of speeds. Despite the X-5's stability problems, the concept was later successfully implemented in such aircraft as the F-111, F-14 Tomcat, MiG-23, Panavia Tornado and B-1 Lancer.

 

The sole surviving X-5 is now at the National Museum of the United States Air Force at Wright-Patterson Air Force Base near Dayton, Ohio. It was delivered to the Museum in March 1958. It is displayed in the Museum's Research & Development Hanger.


General characteristics
  • Crew: 1
  • Length: 33 ft 4 in (10.1 m)
  • Wingspan:
    • Unswept: 33 ft 6 in (10.2 m)
    • 60° sweep: 20 ft 10 in (6.5 m)
  • Height: 12 ft (3.6 m)
  • Wing area: 175 sq. ft. (16.26 m².)
  • Empty weight: 6,336 lb (2,880 kg)
  • Max takeoff weight: 9,980 lb (4,536 kg)
  • Powerplant: 1× Allison J35-A-17 turbojet, 4,900 lbf (21.8 kN)
Performance
  • Maximum speed: 716 mph (1,150 km/h)
  • Range: 750 mi (1,207 km)
  • Service ceiling: 49,900 ft (15,200 m)

The Viscount


The Viscount was a British medium-range turboprop airliner first flown in 1948 by Vickers-Armstrongs, making it the first such aircraft to enter service in the world. It would go on to be one of the most successful of the first-generation post-war transports, with 445 being built.

The design resulted from the Brabazon Committee's Type II design, calling for a small-sized medium-range pressurised aircraft to fly its less-travelled routes, carrying 24 passengers up to 1,750 mi (2,816 km) at 200 mph (320 km/h).[1] British European Airways (BEA) was involved in the design and asked that the plane carry 32 passengers instead, but remained otherwise similar. During development, Vickers advocated the use of turboprop power, believing piston-engines to be a dead-end in aviation. The Brabazon committee was not so convinced, but agreed to split the design into two types, the Type IIA using piston power, and the Type IIB using a turboprop. Vickers won the IIB contracts, while the IIA was the Airspeed Ambassador.

The resulting Vickers Type 630 design was completed at Brooklands by Chief Designer Rex Pierson and his staff in 1945, a 32-seat airliner powered by four Rolls-Royce Dart engines providing a cruising speed of 275 mph (443 km/h). An order for two prototypes was placed in March 1946, and construction started almost immediately. Originally to be named Viceroy, the name was changed after the partition of India in 1947. There was some work on replacing the Darts with the Armstrong Siddeley Mamba, but this was dropped by the time the prototypes were reaching completion.
The prototype Type 630 flew on 16 July 1948. It was awarded a restricted Certificate of Airworthiness on 15 September 1949, followed by a full Certificate on 27 July 1950, and placed into service with BEA the next day to familiarize the pilots and ground crew with the new aircraft. However the design was considered too small and slow at 275 mph (443 km/h), making the per-passenger operating costs too high for regular service.
The second prototype Viscount was named the Type 663 and was built as a test-bed. This aircraft fitted with two Rolls-Royce Tay (turbojet) engines and first flew in RAF Markings as VX217 at Wisley on 15 March 1950. It demonstrated at the Farnborough SBAC Show in September and was later used in the development of powered controls for the Valiant bomber. Subsequently, Boulton Paul Ltd used it as a test bed for electronic control systems until scrapping in the early 1960s.
General characteristics
  • Crew: Two pilots + cabin crew
  • Capacity: 75 passengers
  • Length: 85 ft 8 in (26.11 m)
  • Wingspan: 93 ft 8 in (28.56 m)
  • Height: 26 ft 9 in (8.15 m)
  • Wing area: 963 ft² (89 m²)
  • Empty weight: 41,479 lb (18,815 kg)
  • Max takeoff weight: 72,281 lb (32,786 kg)
  • Powerplant: 4× Rolls-Royce Dart RDa.7/1 Mk 525 turboprop, 2,100 shp (1,566 kW) each
Performance
  • Maximum speed: 352 mph (566 km/h)
  • Range: 1,735 mi (2,790 km)
  • Service ceiling: 25,000 ft (7,620 m)
  • Wing loading: 75 lb/ft² (368 kg/m²)
  • Power/mass: 0.12 hp/lb (0.19 kW/kg)

Monday, October 5, 2009


Convair XF-92
XF-92


A photo of the Convair XF-92 in flight, courtesy of NASA
Role
Interceptor
Manufacturer
Convair
Designed by
Alexander Lippisch
First flight
1 April 1948
Status
Cancelled
Primary user
United States Air Force
Number built
1
Unit cost
US$4.3 million for the program
Variants
F-102 Delta Dagger
The Convair XF-92 was the first American delta-wing aircraft. Originally conceived as a point-defense interceptor, the design was later made purely experimental. However its design, suitably enlarged, led Convair to use the delta-wing on a number of designs, including the F-102 Delta Dagger, F-106 Delta Dart, and B-58 Hustler as well as the experimental XFY.

Design and development

The XF-92A at Edwards Air Force Base, 1952

The XF-92—nicknamed Dart—traces its ancestry to an August 1945 USAAF proposal for a supersonic interceptor capable of 700 mph speeds and reaching an altitude of 50,000 feet in four minutes. Several companies responded, and in May 1946 Convair (then still Consolidated Vultee) won with their proposal for a ramjet-powered aircraft with a 45-degree swept wing under USAAF Air Materiel Command Secret Project MX-813. However, wind tunnel testing demonstrated a number of problems with this design.

Looking for solutions, Convair came across the work of Dr. Alexander Lippisch, who had come to the United States as part of Operation Paperclip. Before and during the war, Lippisch had worked on a variety of delta-wing aircraft, first as low-speed gliders, and later as high-speed interceptors. Lippisch had concluded that the delta-wing was a natural design for supersonic flight, as the highly swept leading edge remained free of the shock wave off the front of the aircraft. He had plans to develop this as the Lippisch P.13a, but progressed only to a unpowered glider example, the Lippisch DM-1.

The P.13 design consisted of two large triangles joined together. One formed the main structure and wing, the other was the vertical stabilizer and cockpit. The only deviation from the triangular layout was an oval air intake at the nose, and round nozzle at the rear. The engine was powered by coal dust stored in a large rotating disk, the odd power source being a solution to the twin problems of lack of petroleum and manufacturing capability in Germany at the time the design was being proposed.

Convair took up Lippisch's work, redesigning it for jet power using the 1,560 lbf Westinghouse J30 assisted by a battery of six 2,000 lbf liquid-fueled rockets. The engine layout was rather portly and would not fit cleanly into the wing of the original P.13 layout, forcing a redesign. The new layout placed the engine in a seemingly oversized cylindrical fuselage, moving the pilot out of the triangular rudder into a separate cockpit centered in the middle of the fuselage, serving double duty as a shock cone for the engine intake. The basic layout of the fuselage was very similar to the Miles M.52 design, although the M.52 did not use a delta wing. The rudder, no longer serving as the cockpit as well, was reduced in size. The new design was presented to the U.S. Air Force in 1946, and was accepted for development as the XP-92.

In order to gain in-flight experience with the delta wing layout, Convair suggested building a smaller prototype, the Model 7002, which the USAAF accepted in November 1946. The design was similar in general layout as the original, but by placing the pilot in a conventional cockpit at the front, instead of centered in the fuselage, the resulting aircraft looked considerably less odd. In order to save development time and money, many components were taken from other aircraft; the main gear was taken from an FJ Fury, the nosewheel from a P-63 Kingcobra, the engine and hydraulics were taken from a Lockheed P-80 Shooting Star, the ejector seat and cockpit canopy were taken from the cancelled Convair XP-81, and the rudder pedals were taken from a BT-13 trainer.

Construction was well underway at Vultee Field in Downey, California when North American Aviation took over the Vultee plants in summer 1947. The airframe was moved to Convair's plant in San Diego, and completed in the autumn. In December it was shipped without an engine to NACA's Ames Aeronautical Laboratory for wind tunnel testing. After testing was completed, the airframe was returned to San Diego, where it was fitted with a 4,250 lbf. Allison J33-A-21 engine.

By the time the aircraft was ready for testing, the concept of the point-defense interceptor seemed outdated and the (now redesignated) F-92 project was cancelled. They also decided to rename the test aircraft as the XF-92A.

General characteristics
  • Crew: 1
  • Length: 42 ft 6 in (12.99 m)
  • Wingspan: 31 ft 4 in (9.55 m)
  • Height: 17 ft 9 in (5.37 m)
  • Wing area: 425 ft² (39.5 m²)
  • Empty weight: 9,078 lb (4,118 kg)
  • Loaded weight: 14,608 lb (6,626 kg)
  • Powerplant: 1× Allison J33-A-29 turbojet, 7,500 lbf (33.4 kN)
Performance
  • Maximum speed: 718 mph (624 knots, 1,160 km/h)
  • Service ceiling: 50,750 ft (15,450 m)
  • Rate of climb: 8,135 ft/min (41.3 m/s)
  • Wing loading: 34 lb/ft² (168 kg/m²)
  • Thrust/weight: 0.51

Thursday, October 1, 2009

The Lockheed Constellation (Connie)

The Lockheed Constellation (Connie) was a four engine (each with 18 pistons of Radial design, the Wright R-3350) propeller-driven airliner built by Lockheed between 1943 and 1958 at its Burbank, California, USA, facility. A total of 856 aircraft were produced in four models, all distinguished by a triple-tail design and dolphin-shaped fuselage. The Constellation was used as a civilian airliner and as a U.S. military air transport plane, seeing service in the Berlin Airlift. It was the presidential aircraft for U.S. President Dwight D. Eisenhower.
Constellation

Super Constellation

C-69 / C-121



A Qantas Empire Airways L-749 Constellation.
Role
Airliner
Manufacturer
Lockheed
First flight
January 9, 1943
Introduced
1943 with USAAF

1945 with TWA
Retired
1967, airline service

1978, military
Primary users
Trans World Airlines

United States Army Air Forces
Produced
1943–1958
Number built
856
Variants
EC-121 Warning Star

Initial design studies

Since 1937, Lockheed had been working on the L-044 Excalibur, a four-engine pressurized airliner. In 1939, Trans World Airlines, at the encouragement of major stockholder Howard Hughes, requested a 40-passenger transcontinental airliner with 3,500 mi (5,630 km) range[1] - well beyond the capabilities of the Excalibur design. TWA's requirements led to the L-049 Constellation, designed by Lockheed engineers including Kelly Johnson and Hall Hibbard.[2] Willis Hawkins, another Lockheed engineer, maintains that the Excalibur program was purely a cover for the Constellation.

   Development of the Constellation

The Constellation's wing design was close to that of the P-38 Lightning, differing mostly in scale.  The distinctive triple tail kept the aircraft's overall height low enough to fit in existing hangars,  while new features included hydraulically-boosted controls and a thermal de-icing system used on wing and tail leading edges.[ The plane had a top speed of over 340 mph (547 km/h), a cruise speed of 300 mph (483 km/h), and a service ceiling of 24,000 ft (7,315 m).

According to Anthony Sampson in Empires of the Sky, the intricate design may have been undertaken by Lockheed, but the concept, shape, capabilities, appearance and ethos of the Constellation were driven by Hughes' intercession during the design process.

With the onset of World War II, the TWA aircraft entering production were converted to an order for C-69 Constellation military transport aircraft, with 202 aircraft intended for the United States Army Air Forces (USAAF). The first prototype (civil registration NX25600) flew on January 9, 1943, a simple ferry hop from Burbank to Muroc Field for testing.[1] Eddie Allen, on loan from Boeing, flew left seat, with Lockheed's own Milo Burcham as copilot. Rudy Thoren and Kelly Johnson were also on board.

Lockheed proposed model L-249, which was to be a long range bomber. It received the military designation XB-30 but the aircraft was not developed. A plan for a very long-range troop transport, the C-69B, was canceled. A single C-69C, a 43-seat VIP transport, was built in 1945 at the Lockheed-Burbank plant.

The C-69 was mostly used as a high-speed, long-distance troop transport during the war.  22 C-69s were completed before the end of hostilities, and not all of those entered military service. The USAAF cancelled the remainder of the order in 1945.

After World War II, the Constellation soon came into its own as a popular, fast, civilian airliner. Aircraft already in production for the USAAF as C-69 transports were finished as civilian airliners, with TWA receiving the first on 1 October 1945. The first transatlantic proving flight departed Washington, DC on December 3, 1945, arriving in Paris on December 4, via Gander and Shannon.

Trans World Airlines opened post-war commercial intercontinental air service on February 6, 1946, with a New York-Paris flight in a Constellation. On June 17, 1947, Pan American World Airways opened the first ever regularly-scheduled around-the-world service with their L749 Clipper America. The famous flight Pan Am 101 operated for over 40 years.

As the first pressurized airliner in widespread use, the Constellation helped to usher in affordable and comfortable air travel. Operators of Constellations included TWA, Eastern Air Lines, Pan American World Airways, Air France, BOAC, KLM, Qantas, Lufthansa, Iberia Airlines, Panair do Brasil, TAP Portugal, Trans-Canada Airlines (later renamed Air Canada), Aer Lingus and VARIG.

Initial difficulties

The Constellation airliner had three accidents in the first ten months of service, temporarily curtailing its career as a passenger airliner. On June 18, 1946, the engine of a Pan American aircraft caught fire and fell off. The flight crew made an emergency landing with no loss of life. However, on July 11, a Transcontinental and Western Air aircraft fell victim to an in-flight fire, crashing in a field and taking the lives of five of the six on board The accidents prompted the suspension of the Constellation's airworthiness certificate until Lockheed could modify the design. This was dramatized in the motion picture The Aviator (2004) during the scene where Howard Hughes (played by Leonardo DiCaprio) surveys numerous grounded TWA Constellations.

The Constellation proved prone to engine failures (due to her R3350s), earning the nickname "World's Finest Trimotor" in some circles.

Records

Sleek and powerful, Constellations set a number of records. On April 17, 1944, the second production L049, piloted by Howard Hughes and TWA president Jack Frye, flew from Burbank, California to Washington, D.C. in 6 hours and 57 minutes (c. 2,300 mi/3,701 km at an average 330.9 mph/532.5 km/h). On the return trip, the aircraft stopped at Wright Field to give Orville Wright his last flight, more than 40 years after his historic first flight. He commented that the Constellation's wingspan was longer than the distance of his first flight.

On September 29, 1957, a L1649A Starliner flew from Los Angeles to London in 18 hours and 32 minutes (approximately 5,420 mi/8,723 km at 292.4 mph/470.6 km/h). The L1649A holds the record for the longest-duration non-stop passenger flight — during TWA's inaugural London to San Francisco flight on October 1-2 1957, the aircraft stayed aloft for 23 hours and 19 minutes (approximately 5,350 mi/8,610 km at 229.4 mph/369.2 km/h)

Obsolescence

The advent of jet airliners, with the de Havilland Comet, Boeing 707, Douglas DC-8 and Convair 880, rendered the piston-engined Constellation obsolete. The first routes lost to jets were the long overseas routes, but Constellations continued to fly domestic routes. The last scheduled passenger flight of a four-engined piston-engined airliner in the United States was made by a TWA L749 on May 11, 1967 from Philadelphia to Kansas City, MO. However, Constellations remained in freight service for years to come, and were the mainstay of Eastern Airlines' shuttle service between New York, Washington, and Boston until 1968.

One of the reasons for the elegant appearance of the aircraft was the fuselage shape - a continuously variable profile with no two bulkheads the same shape. Unfortunately, this construction is very expensive and was replaced by the mostly tube-shape of modern airliners. The tube is more resistant to pressurization changes and cheaper to build.

With the shutdown of Constellation production, Lockheed elected not to develop a first-generation jetliner, instead sticking to its lucrative military business and production of the modest turboprop-powered Lockheed L-188 Electra airliner. Lockheed would not build a large civil passenger aircraft again until its L-1011 Tristar debuted in 1972. While a technological marvel, the L-1011 was a commercial failure, and Lockheed left the commercial airliner business permanently in 1983.

The Arado Ar 234

The Arado Ar 234 was the world's first operational jet powered bomber, built by the German Arado company in the closing stages of World War II. In the field it was used almost entirely in the reconnaissance role, but in its few uses as a bomber it proved to be nearly impossible to intercept. Twin-engined and single seater, was produced in limited numbers. It was the last Luftwaffe plane to fly over England, in April 1945.

It is commonly known as Blitz ("lightning"), though this name refers only to the B-2 bomber variant, and it is not clear whether it was ever formally applied instead of being derived from the informal term Blitz-Bomber (roughly, "very fast bomber"). The alternate name Hecht ("pike") is derived from one of the units equipped with this plane, Sonderkommando Hecht. The Ar 234 (and the Messerschmitt Me 262) showed in which direction plane technique should develop.
Ar 234


Role
Reconnaissance Bomber
Manufacturer
Arado Flugzeugwerke
Designed by
Walter Blume
First flight


15 June 1943

Introduction
September 1944
Status
Retired
Primary user
Luftwaffe
Number built
210

Background and prototypes

In the autumn of 1940, the RLM offered a tender for a jet-powered high-speed reconnaissance aircraft with a range of 2,156 km (1,340 mi). Arado was the only company to respond, offering their E.370 project, led by Professor Walter Blume. This was a high-wing conventional-looking design with a Junkers Jumo 004 engine under each wing. The projected weight for the aircraft was approximately 8,000 kg (17,600 lb). In order to reduce the weight of the aircraft and maximize the internal fuel, Arado did not use the typical retractable landing gear; instead, the aircraft was to take off from a jettisonable three-wheeled, nosegear-style trolley and land on three retractable skids, one under the central section of the fuselage, and one under each engine nacelle.

Arado estimated a maximum speed of 780 km/h (490 mph) at 6,000 m (19,690 ft), an operating altitude of 11,000 m (36,100 ft) and a range of 1,995 km (1,240 mi).

The range was short of the RLM request, but they liked the design and ordered two prototypes as the Ar 234. These were largely complete before the end of 1941, but the Jumo 004 engines were not ready, and would not be ready until February 1943. When they did arrive they were considered unreliable by Junkers for in-flight use and were only cleared for static and taxi tests. Flight-qualified engines were finally delivered that spring, and the Ar 234 V1 made its first flight on 15 June 1943. By September, four prototypes were flying. The eight prototype aircraft were fitted with the original arrangement of trolley-and-skid landing gear. The sixth and eighth of the series were powered with four BMW 003 jet engines instead of two Jumo 004's, the sixth having four engines housed in individual nacelles, and the eighth flown with two pairs of BMW 003s installed within "twinned" nacelles underneath either wing. These were the first four-engine jet aircraft to fly. The Ar 234 V7 prototype made history on 2 August 1944 as the first jet aircraft ever to fly a reconnaissance mission.

Ar 234B

The RLM had already seen the promise of the design and in July had asked Arado to supply two prototypes of a schnellbomber ("fast bomber") version as the Ar 234B. Since the aircraft was very slender and entirely filled with fuel tanks, there was no room for an internal bomb bay and the bombload had to be carried on external racks. The added weight and drag of a full bombload reduced the speed, so two 20 mm MG 151 cannon were added in a remotely-controlled tail mounting to give some measure of defence. Since the cockpit was directly in front of the fuselage, the pilot had no direct view to the rear, so the guns were aimed through a periscope mounted on the cockpit roof. The system was generally considered useless, and many pilots had the guns removed to save weight.

The external bombload, and the presence of inactive aircraft littering the landing field after their missions were completed (as with the similarly dolly/skid-geared Messerschmitt Me 163) made the skid-landing system impractical, so the B version was modified to have tricycle landing gear. The ninth prototype, marked with the Stammkennzeichen (radio code letters) PH+SQ, was the first Ar 234B, and flew on 10 March 1944. The B models were slightly wider at the mid-fuselage to house the main landing gear, with a fuel tank present in the mid-fuselage location on the eight earlier trolley/skid equipped prototype aircraft having to be deleted for the retracted main gear's accommodation, and with full bombload, the plane could only reach 668 km/h (415 mph) at altitude. This was still better than any bomber the Luftwaffe had at the time, and made it the only bomber with any hope of surviving the massive Allied air forces.

Production lines were already being set up, and 20 B-0 pre-production planes were delivered by the end of June. Later production was slow, however, as the Arado plants were tasked with producing planes from other bombed-out factories hit during the Big Week, and the license-building of Heinkel's heavy He 177 bomber. Meanwhile, several of the prototypes were sent forward in the reconnaissance role. In most cases, it appears they were never even detected, cruising at about 740 km/h (460 mph) at over 9,100 m (29,900 ft).

The few 234Bs entered service in the fall and impressed their pilots. They were fairly fast and completely aerobatic. The long takeoff runs led to several accidents; a search for a solution led to improved training as well as the use of rocket-assisted takeoff. The engines were always the real problem; they suffered constant flameouts and required overhaul or replacement after about 10 hours of operation.

The most notable use of the Ar 234 in the bomber role was the attempt to destroy the Ludendorff Bridge at Remagen. Between 7 March, when it was captured by the Allies, and 17 March, when it finally collapsed, the bridge was continually attacked by Ar 234s of III/KG 76 carrying 1,000 kg (2,200 lb) bombs. The aircraft continued to fight in a scattered fashion until Germany surrendered on 8 May 1945. Some were shot down in air combat, destroyed by flak, or "bounced" by Allied fighters during takeoff or on the landing approach, as was already happening to Messerschmitt Me 262 jet fighters. Most simply sat on the airfields awaiting fuel that never arrived.

The normal bombload consisted of two 500 kg (1,100 lb) bombs suspended from the engines or one large 1,000 kg (2,200 lb) bomb semi-recessed in the underside of the fuselage with maximum bombload being 1,500 kg (3,310 lb). If the war had continued it is possible that the aircraft would have been converted to use the Fritz X guided bombs or Henschel Hs 293 air-to-surface missiles.

Overall from the summer of 1944 until the end of the war a total of 210 aircraft were built. In February 1945, production was switched to the C variant. It was hoped that by November 1945 production would reach 500 per month.
  • Ar 234B-0 : 20 pre-production aircraft.
  • Ar 234B-1 : Reconnaissance version, equipped with two Rb 50/30 or Rb 75/30 cameras.
  • Ar 234B-2 : Bomber version, with a maximum bombload of 2,000 kg (4,410 lb).

[Ar 234C

The Ar 234C was equipped with four BMW 003A engines, mounted in a pair of twin-engine nacelles based on those from the eighth Ar 234 prototype. The primary reason for this switch was to free up Junkers Jumo 004s for use by the Me 262, but this change improved overall thrust, especially in take-off and climb-to-altitude performance. Airspeed was found to be about 20% faster than the B series and, due to the faster climb to altitude, range was increased. Although Hauptmann Diether Lukesch was preparing to form an operational test squadron, the Ar 234C was not developed in time to participate in actual combat operations. There were two primary versions of the C: the C-1, a four-engine version of the B-1, and the C-2, a four-engine version of the B-2. At least seven other versions of the C were designed or were in the planning stages before the war ended, including bombers, armed reconnaissance, night fighters and a heavy bomber. 14 prototypes of the Ar 234C, which included the C-1 and C-2 models, were completed before the end of the war.
  • Ar 234C-1 : Four-engined version of the Ar 234B-1.
  • Ar 234C-2 : Four-engined version of the Ar 234B-2.
  • Ar 234C-3 : Multi-purposed version, armed with two 20 mm MG 151/20 cannons beneath the nose.
  • Ar 234C-3/N : Proposed two-seat night fighter version, armed with two forward-firing 20 mm MG 151/20 and two 30 mm (1.18 in) MK 108 cannons, fitted with a FuG 218 Neptun V radar.
  • Ar 234C-4 : Armed reconnaissance version, fitted with two cameras, armed with four 20 mm MG 151/20 cannons.
  • Ar 234C-5 : Proposed version with side-by-side seating for the crew. The 28th prototype was converted into this variant.
  • Ar 234C-6 : Proposed two-seat reconnaissance aircraft. The 29th prototype was converted into this variant.
  • Ar 234C-7 : Night fighter version, with side-by-side seating for the crew, fitted with an enhanced FuG 245 Bremen O cavity magnetron-based centimetric (30 GHz) radar.
  • Ar 234C-8 : Proposed single-seat bomber version, powered by two 1,080 kg (2,380 lb) Jumo 004D turbojet engines.

Ar 234D

The D model was a two-seat aircraft based on the B-series fuselage, but with a new, enlarged two-seat cockpit, intended to be powered by a pair of more powerful Heinkel HeS 011 turbojet engines. The HeS 011 powerplant never reached quantity production, and no 234D was produced.
  • Ar 234D-1 : Proposed reconnaissance version. Not built.
  • Ar 234D-2 : Proposed bomber version. Not built.

Ar 234P

The P model was a two-seat night fighter version, differing in powerplant options and several options of radar. Several were in the planning stage, but none made it into production.
  • Ar 234P-1 : Two seater with four BMW 003A-1 engines; one 20 mm MG 151/20 and one 30 mm (1.18 in) MK 108.
  • Ar 234P-2 : Also a two seater, with redesigned cockpit protected by a 13 mm (0.51 in) armour plate.
  • Ar 234P-3 : HeS 011A powered P-2, but with two each of the cannon.
  • Ar 234P-4 : as P-3 but with Jumo 004D engines.
  • Ar 234P-5 : Three seat version with HeS 011A engines, one 20 mm MG 151/20 and four 30 mm (1.18 in) MK 108s.
General characteristics
  • Crew: 1
  • Length: 12.63 m (41 ft 5½ in)
  • Wingspan: 14.10 m (46 ft 3½ in)
  • Height: 4.30 m (14 ft 1¼ in)
  • Wing area: 26.40 m² (284.16 ft²)
  • Empty weight: 5,200 kg (11,460 lb)
  • Max takeoff weight: 9,850 kg (21,720 lb)
  • Powerplant: 2× Junkers Jumo 004B-1 turbojets, 8.80 kN (1,980 lbf) each
Performance
  • Maximum speed: 742 km/h (461 mph) at 6,000 m (19,700 ft)
  • Combat radius: 1,100 km (684 mi) with maximum bombload
  • Service ceiling: 10,000 m (32,800 ft)
Armament
  • Guns: 2 × 20 mm MG 151 cannons in tail firing to the rear (optional)
  • Bombs: up to 1,500 kg (3,309 lb) of disposable stores on external racks

The Messerschmitt Me 262 Schwalbe

The Messerschmitt Me 262 Schwalbe ("Swallow") was the world's first operational jet-powered fighter aircraft. It was produced in World War II and saw action starting in 1944 as a multi-role fighter/bomber/reconnaissance/interceptor warplane for the Luftwaffe. It has been considered the most advanced German aviation design in service [5] and according to some Allied historians it was a plane that might have won the war by giving air supremacy back to the Luftwaffe, being much faster and more heavily armed than Allied fighters in service at that time such as the Gloster Meteor I.  But it had a negligible impact on the course of the war due to its late introduction and the small numbers in service. It claimed a total of 509 Allied kills (although higher claims are sometimes made[Notes 1]) against the loss of about 100 Me 262s. The Me 262 influenced the designs of post-war aircraft such as the North American F-86 and Boeing B-47.
Me 262 Schwalbe


Messerschmitt Me 262A
Role
Fighter
Manufacturer
Messerschmitt
First flight
18 April 1941 with piston engines

18 July 1942 with jet engines [1]
Introduction
April 1944[2][3]
Retired
1945, Luftwaffe

1957, Czechoslovakia
Primary users
Luftwaffe

Czechoslovak Air Force
Number built
1,430
The Me 262 was already being developed as Projekt P.1065 before the start of World War II. Plans were first drawn up in April 1939, and the original design was very similar to the plane that eventually entered service. The progression of the original design into service was delayed greatly by technical issues involving the new jet engines. Funding for the jet program was also initially lacking as many high-ranking officials thought the war could easily be won with conventional aircraft. Among those was Hermann Göring, head of the Luftwaffe, who cut back the engine development program to just 35 engineers in February 1940, Willy Messerschmitt, who desired to maintain mass production of the Bf 109 and the projected Me 209, and Major General Adolf Galland, who supported Messerschmitt through the early development years, flying the Me 262 himself on 22 April 1943. By that time problems with engine development had slowed production of the aircraft considerably.

In mid-1943 Adolf Hitler envisioned the Me 262 as an offensive ground-attack/bomber rather than a defensive interceptor, as a high speed, light payload Schnellbomber ("Fast Bomber"), to penetrate Allied air superiority during the expected invasion of France. His edict resulted in the development of (and concentration on) the Sturmvogel variant. It is debatable to what extent Hitler's interference extended the delay in bringing the Schwalbe into operation.  Albert Speer, then Minister of Armaments and War Production, claimed in his memoirs that Hitler originally blocked mass-production of the Me 262 before agreeing to production in early 1944. He rejected arguments that the plane would be more effective as a fighter against Allied bombers then destroying large parts of Germany and wanted it as a bomber for revenge attacks. According to Speer Hitler had felt that its superior speed compared to other fighters of the era meant that it couldn't be attacked and so had preferred it for high altitude straight flying.

Although it is often stated the Me 262 is a "swept wing" design, the production Me 262 had a leading edge sweep of only 18.5°. This was done after the initial design of the aircraft, when the engines proved to be heavier than originally expected, primarily to position the center of lift properly relative to the centre of mass, not for the aerodynamic benefit of increasing the critical Mach number of the wing, where the sweep was too slight to achieve any significant advantage. On 1 March 1940, instead of moving the wing forward on its mount, the outer wing was repositioned slightly aft. The trailing edge of the mid-section of the wing remained unswept.. Based on data from the AVA Göttingen and windtunnel results, the middle section's leading edge was later swept to the same angle as the outer panels

The first test flights began on 18 April 1941, with the Me 262 V1 example, bearing its Stammkennzeichen radio code letters of PC+UA, but since its intended BMW 003 turbojets were not ready for fitting, a conventional Junkers Jumo 210 engine was mounted in the V1 prototype's nose, driving a propeller, to test the Me 262 V1 airframe. When the BMW 003 engines were finally installed, the Jumo was retained for safety, which proved wise as both 003s failed during the first flight and the pilot had to land using the nose mounted engine alone.

The V3 third prototype airframe, with the code PC+UC, became a true "jet" when it flew on 18 July 1942 in Leipheim near Günzburg, Germany, piloted by Fritz Wendel. This was almost nine months ahead of the British Gloster Meteor's first flight on 5 March 1943. The conventional gear, forcing a tail-down attitude on the ground, of the Me 262 V3 caused its jet exhaust to deflect off the runway, with the wing's turbulence negating the effects of the elevators in the tail-down attitude, and the first attempt was cut short. On the second attempt, Wendel solved the problem by tapping the aircraft's brakes at takeoff speed, lifting the horizontal tail above and out of the wing's turbulence.[

The aircraft was originally designed with a tailwheel undercarriage and the first four prototypes (Me 262 V1-V4) were built with this configuration, but it was discovered on an early test run that the engines and wings "blanked" the stabilizers, giving almost no control on the ground, as well as serious runway surface damage from the hot jet exhaust. Changing to a tricycle undercarriage arrangement, initially a fixed undercarriage on the "V5" fifth prototype, then fully retractable on the sixth (V6, with Stammkennzeichen code VI+AA) and succeeding aircraft, corrected this problem.

The BMW 003 jet engines, which were proving unreliable, were replaced by the newly available Junkers Jumo 004. Test flights continued over the next year, but the engines continued to be unreliable. Airframe modifications were complete by 1942, but hampered by the lack of engines, serial production did not begin until 1944, but deliveries were low with 28 Me 262s in June, 59 in July, but only 20 in August.  This delay in engine availability was in part due to the shortage of strategic materials, especially metals and alloys able to handle the extreme temperatures produced by the jet engine. Even when the engines were completed, they had an expected operational lifetime of approximately 50 continuous flight hours; in fact, most 004s lasted just 12 hours, even with adequate maintenance. A pilot familiar with the Me 262 and its engines could expect approximately 20–25 hours of life from the 004s. Changing a 004 engine was intended to require three hours, but this typically took eight to nine due to poorly made parts and inadequate training of ground crews.

Turbojet engines have less thrust at low speed than propellers, and as a result, low-speed acceleration is relatively poor. It was more noticeable for the Me 262 as early jet engines (before the invention of afterburners) responded slowly to throttle changes. The introduction of a primitive autothrottle late in the war only helped slightly. Conversely, the higher power of jet engines at higher speeds meant the Me 262 enjoyed a much higher rate of climb. Used tactically, this gave the jet fighter an even greater speed advantage in climb rate than level flight at top speed.

With one engine out, the Me 262 still flew well, with speeds of 450-500 km/h (280-310 mph), but pilots were warned never to fly slower than 300 km/h (190 mph) on one engine, as the asymmetrical thrust would cause serious problems.

Operationally, the Me 262 had an endurance of 60 to 90 minutes.

General characteristics
  • Crew: 1
  • Length: 10.60 m (34 ft 9 in)
  • Wingspan: 12.60 m (41 ft 6 in)
  • Height: 3.50 m (11 ft 6 in)
  • Wing area: 21.7 m² (234 ft²)
  • Empty weight: 4,404 kg (9,709 lb)
  • Loaded weight: 7,130 kg (15,720 lb)
  • Max takeoff weight: 6977 kg (15,381 lb)
  • Powerplant: 2× Junkers Jumo 004 B-1 turbojets, 8.8 kN (1,980 lbf) each
  • Aspect ratio: 7.32
Performance
  • Maximum speed: 900 km/h (559 mph)
  • Range: 1,050 km (652 mi)
  • Service ceiling: 11,450 m (37,565 ft)
  • Rate of climb: 1,200 m/min (3,900 ft/min)
  • Thrust/weight: 0.28
Armament
  • Guns: 4 × 30 mm MK 108 cannons (A-2a: two cannons)
  • Rockets: 24 × 55 mm (2.2 in) R4M rockets
  • Bombs: 2 × 250 kg (551 lb) bombs or 2 × 500 kg (1,102 lb) bombs (A-2a only)

The Messerschmitt Me 163 Komet

The Messerschmitt Me 163 Komet, designed by Alexander Martin Lippisch, was a German rocket-powered fighter aircraft. It was the only operational rocket-powered fighter aircraft to date. It was a revolutionary design, capable of performance unrivaled at the time. Messerschmitt test pilot Rudy Opitz in 1944 reached 1,123 km/h (698 mph). Only about 300 were built   and it proved ineffective as a fighter responsible for the destruction of about nine Allied aircraft.

Messerschmitt Me 163 Komet


Me 163B-1a at the National Museum of Flight in Scotland
Role
Interceptor
Manufacturer
Messerschmitt
Designed by
Alexander Lippisch
First flight
Me 163 A V4 in 1 September 1941
Introduction
1944
Primary user
Luftwaffe
Number built
~500[citation needed]
Work on the design started under the aegis of the Deutsche Forschungsanstalt für Segelflug (DFS) - the German Institute for the Study of sailplane flight. Their first design was a conversion of the earlier Lippisch Delta IV known as the DFS 39 and used purely as a glider testbed of the airframe.

A larger follow-on version with a small propeller engine started as the DFS 194. This version used wingtip-mounted rudders, which Lippisch felt would cause problems at high speed, and he later redesigned them to be mounted on a conventional vertical stabilizer at the rear of the aircraft. The design included a number of features from its glider heritage, notably a skid used for landings, which could be retracted into the aircraft's keel in flight. For takeoff, a pair of wheels, each mounted onto the ends of a specially designed cross-axle, together comprising a takeoff "dolly" mounted under the landing skid, were needed due to the weight of the fuel, but these were released shortly after takeoff. It was planned to move to the Walter R-1-203 cold engine of 400 kgf (882 lbf) thrust when available.

Heinkel had also been working with Walter on his rocket engines, mounting them in the He 112 for testing, and later the first purpose-designed rocket aircraft, the He 176. Heinkel had also been selected to produce the fuselage for the DFS 194 when it entered production, as it was felt that the highly volatile fuel would be too dangerous in a wooden fuselage, with which it could react. Work continued under the code name Projekt X.

However the division of work between DFS and Heinkel led to problems, notably that DFS seemed incapable of building even a prototype fuselage. Lippisch eventually requested to leave DFS and join Messerschmitt instead. On 2 January 1939, he moved along with his team and the partially completed DFS 194 to the Messerschmitt works at Augsburg.

The delays caused by this move allowed the engine development to "catch up", and once at Messerschmitt the decision was made to skip over the propeller-powered version and move directly to rocket power. The airframe was completed in Augsburg and shipped to Peenemünde West in early 1940 to receive its engine. Although the engine proved to be extremely unreliable, the aircraft had excellent performance, reaching a speed of 342 mph (550 km/h) in one test.

Me 163 A

Production of a prototype series started in early 1941, known as the Me 163. Secrecy was such that the number, 163, was actually that of the earlier, pre-July 1938 Messerschmitt Bf 163 project to produce a small two-passenger light plane, which had competed against the Fieseler Fi 156 Storch for a production contract, as it was thought that intelligence services would conclude any reference to the number would be for that earlier design. Me 163 A V4 was shipped to Peenemünde to receive the HWK RII-203 engine on May 1941, and on 2 October 1941, the Me 163 A V4, bearing the radio call sign letters, or Stammkennzeichen, "KE+SW", set a new world speed record of 1,004.5 km/h (623.8 mph), piloted by Heini Dittmar. This would not be officially approached until the postwar period by the new jet fighters of the British and U.S., and was not surpassed until the American Douglas Skystreak turbojet-powered research aircraft did so on 20 August 1947. Five prototype Me 163 Anton A-series experimental V-aircraft were built, adding to the original DFS 194 (V1), followed by eight pre-production examples designated Me 163 A-0.

During testing the jettisonable main landing gear arrangement proved to be a serious problem and caused many aircraft to be damaged at takeoff when the wheels rebounded and crashed into the aircraft. Malfunctioning hydraulic dampers in the skid could lead to back injuries for the pilot on landing, as the aircraft lacked steering or braking control during the landing run, leaving the pilot unable to avoid obstacles. Once on the ground, it had to be retrieved by an adapted tractor-like vehicle, towing a special retrieval trailer that rolled along on a pair of short continuous track setups (one per side), with twin trailing lifting arms, that lifted the stationary aircraft off the ground, from under each wing panel. The tractor itself was originally meant for agricultural use on small farms, the three-wheeled Scheuch-Schlepper, as the Komet was unpowered and lacked wheels at this point.

During flight testing, the superior gliding capability of the swept-wing Komet proved detrimental to safe landing. The aircraft would rise back into the air with the slightest updraft. Since the approach was made unpowered, there was no opportunity to make another landing pass if the aircraft failed to stop at the proper airfield. For production models, a set of landing flaps allowed somewhat more controlled landings. This issue remained a problem throughout the program, however.

Nevertheless, the performance was tremendous and plans were made to put Me 163 squadrons all over Germany in 40 km (25 mi) rings. Development of an operational version was given the highest priority.

Meanwhile, Walter had started work on the newer HWK 109-509 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.) This resulted in the significantly modified Me 163 B of late 1941. Due to the Reichsluftfahrtministerium (RLM) requirement that it should be possible to throttle the engine, the originally simple power plant grew complicated and lost reliability. The new fuel proved an unfortunate choice as well, since hydrazine hydrate was also used in the launcher of the V-1 "Doodlebug" flying bomb and was in short supply throughout the 1943-45 period.

The fuel system was particularly troublesome, as leaks experienced during hard landings easily degenerated in 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 airframe - yet there were still occasions when Komets simply exploded on the tarmac. The corrosive nature of the liquids also mandated special protective gear for the pilots.

Two prototypes were followed by 30 Me 163B-0 aircraft armed with two 20 mm MG 151/20 cannon and some 400 Me 163B-1s armed with two 30 mm (1.18 in) 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, 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 (Me 262A-1a with Jumo engines, A-1b with BMW engines). As the Me 163 was planned with an alternative BMW P3330A rocket engine it's 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 didn't have any wingtip "washout" built into it, and as a result 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, along the wing's leading edge, of the elevon control surfaces. It was found to be impossible to stall, nor would it 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 beautifully. Because it was derived from a glider, it had excellent gliding qualities which meant it had the tendency to keep on flying above the ground. 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 thing. One had to be careful the control stick wasn't 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 "sharp start" from the ground, from its two-wheeled dolly. The aircraft would be kept 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, pull up into a 70° angle of climb, and rapidly climb to the bombers' altitude. It could go even higher if need be, reaching 12,000 m (40,000 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 hope to match. Because of its thin wings it didn't suffer from compressibility or other aerodynamic problems as much as other early jet aircraft. What's more, 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 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 was at that time underworked. As with many German designs of World War II, parts of the airframe (esp. wings) were made of wood, which allowed furniture manufacturers to act as subcontractors.

For training purposes, the older Me 163A and first Me 163B prototypes were used. But it was planned to introduce the Me 163 S, which removed the rocket engine and tank capacity and placed a second seat for the instructor behind the pilot. The 163 S 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 in) MK 108 cannons which had a relatively low muzzle velocity, with the characteristic ballistic drop of such a weapon, which 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 in) 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, though other sources say it was a Boeing B-17

 

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. In order to improve on this, the Walter firm started on the development of a more advanced engine with two separate combustion chambers of differing sizes, oriented one above the other, as a more efficient powerplant. The upper chamber, intended as the motor's primary power output unit, was of a larger size, and supported by the "thrust tube" exactly as on the 509A motor's single chamber had been. It was tuned for "high power" for takeoff and climb, and the smaller volume, lower chamber with approximately 400 kg (880 lb) of thrust at its top performance level, was intended for use as a way of allowing more efficient, lower-power cruise flight. This HWK 109-509 C would improve endurance by as much as 50%. Two 163 Bs, V6 and V18, were experimentally fitted with the new engine and tested in 1944. On 6 July 1944, the Me 163 B V18 (VA+SP) set a new 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.   This record was not broken in terms of absolute speed until 6 November 1947 by Chuck Yeager in a flight that was part of the 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 (49,000 ft) altitude. . But the X-1 never exceed this speed in a normal runway liftoff, Heini Dittmar reached this 1,130 km/h (700 mph) performance, after a normal "sharp start" ground takeoff, without an air drop from a mother ship. Neville Duke exceed Heini Dittmars record mark in 31 August 1953 with the Hawker Hunter F Mk3 with a speed of 1,171 km/h (728 mph), after a normal ground start.[11] Aircraft of the configuration the Me 163 used were eventually 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 509C "cruiser" rocket more remarkable.

Woldemar Voigt of Messerschmitt's Oberammergau offices started a redesign of the 163 to incorporate the new engine, as well as fix other problems. The resulting Me 163 C 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 giving dramatically improved visibility. 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 twelve minutes, almost doubling combat time (from about five minutes to nine). Three Me 163C-1a prototypes were planned, but it appears only one was flown, and that without its intended engine.

But by this time the project was moved to Junkers. Here 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 defeciency being the lack of a retractable landing gear of any sort. For this the Me 163V-18 was equipped with a non-retractable tricycle landing gear. (This prototype is often called the Me 163D but it is now clear that there never was a 163 D.) 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 109-509 C engine was fitted in September, but it was probably never tested under this power. At this point the RLM re-assigned the project to Messerschmitt, where it became the Me 263. This appears to have been a formality only, with Junkers continuing the work and planning production

However, by the time the design was ready to go into production, after many delays, the plant it was to be made at was overrun by Soviet forces. While it did not reach operational status, the work was briefly continued by the Russian Mikoyan-Gurevich (MiG) design bureau as the Mikoyan-Gurevich I-270[14].