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].

The Heinkel He 178

The Heinkel He 178 was the world's first aircraft to fly under turbojet power, and the first practical jet plane, the pioneering example of this type of aircraft. It was a private venture by the German Heinkel company in accordance with director Ernst Heinkel's emphasis on developing technology for high-speed flight and first flew on 27 August 1939 piloted by Erich Warsitz. This had been preceded by a short hop three days earlier.

In 1936, a young engineer named Hans von Ohain had taken out a patent on using the exhaust from a gas turbine as a means of propulsion.

He presented his idea to Heinkel, who agreed to help develop the concept. Von Ohain successfully demonstrated his first engine in 1937, and plans were quickly made to test a similar engine in an aircraft. The He 178 was designed around von Ohain's third engine design, the HeS 3, which burned diesel fuel. The result was a small aircraft with a metal fuselage of conventional configuration and construction. The jet intake was in the nose, and the plane was fitted with tailwheel undercarriage. The main landing gear was eventually intended to have been made retractable, but remained fixed in its "down" position throughout its flight trials.

The high-mounted wooden wings had the characteristic Günter brothers elliptical trailing edge. Photos showing a "straight wing" (straight-line-taper in the wing planform, for both the leading and trailing edge) were of the second prototype He 178 V2, which never flew under power.

The aircraft was a success; however, speeds were limited to 598 km/h (375 mph) at the proposed service altitude, and combat endurance was only 10 minutes. Its fall to official indifference was that Hermann Göring favoured the higher-developed piston engined fighters of the day which had already achieved higher performance standards, as opposed to investing more money into developing the jet engine. On 1 November 1939, Heinkel arranged a demonstration of the jet for the Reichsluftfahrtministerium ("Reich Aviation Ministry", RLM), where both Ernst Udet and Erhard Milch watched the aircraft perform. However, due to the conservative approach to aircraft design then favoured by both men, no official interest in the concept was shown. Nevertheless, Heinkel was undeterred, and decided to embark on the development of a twin-engine jet fighter, the He 280 as a private venture using what had been learned from the He 178.

The He 178 was placed in the Deutsches Technikmuseum ("German Technical Museum") in Berlin, where it was destroyed in an air raid in 1943.

General characteristics

• Crew: One
• Length: 7.48 m (24 ft 6 in)
• Wingspan: 7.20 m (23 ft 3 in)
• Height: 2.10 m (6 ft 10 in)
• Wing area: 9.1 m² (98 ft²)
• Empty weight: 1,620 kg (3,572 lb)
• Max takeoff weight: 1,998 kg (4,405 lb)
• Powerplant: 1× HeS 3 turbojet, 4.4 kN (992 lbf)

Performance

• Maximum speed: 598 km/h (375 mph)
• Range: 200 km (125 mi)

The Heinkel He 100

The Heinkel He 100 was a German pre-World War II fighter aircraft design from Heinkel. Although it proved to be one of the fastest fighter aircraft in the world at the time of its development, the design was not ordered into series production, Approximately 19 prototypes and pre-production machines were built. The reason for the failure of the He 100 to reach production status is subject to debate. None are known to have survived the war.

Officially, the Luftwaffe rejected the He 100 to concentrate single-seat fighter development on the Messerschmitt Bf 109. Following the adoption of the Bf 109 and Bf 110 as the Luftwaffe's standard fighter types, the RLM announced a "rationalization" policy that placed fighter development at Messerschmitt and bomber development at Heinkel.

Because there are no surviving examples, and since many factory documents - including all blueprints for the He 100 - were destroyed during a bombing raid, there is limited specific information about the design and its unique systems.

Following the selection by the RLM of the Bf 109 as its next single-seat fighter over the He 112, Ernst Heinkel became interested in a new fighter that would leap beyond the performance of the Bf 109 as much as the Bf 109 had over the biplanes it replaced. Other German designers had similar ambitions, including Kurt Tank at Focke-Wulf. There was never an official project on the part of the RLM, but Rudolf Lucht felt that new designs were important enough to fund the projects from both companies to provide "super-pursuit" designs for evaluation. This would result in the single-engined He 100 fighter, and the promising twin-engine Fw 187 Falke Zerstörer-style heavy fighter, both reaching the flight stage of development.

The super-pursuit type was not a secret, but Ernst Heinkel preferred to work in private and publicly display his products only after they were developed sufficiently to make a stunning first impression. As an example of this, the mock-up for the extremely modern-looking He 100 was the subject of company Memo No.3657 on 31 January that stated: The mock-up is to be completed by us... as of the beginning of May... and be ready to present to the RLM... and prior to that no one at the RLM is to know of the existence of the mock-up.

Walter Günter, one half of the famous Günter brothers, looked at the existing He 112, which had already been heavily revised into the He 112b version and decided to start over with a completely new design, Projekt 1035. Learning from past mistakes on the 112 project, the design was to be as easy to build as possible yet 700 km/h (440 mph) was a design goal. To ease production, the new design had considerably fewer parts than the 112 and those that remained contained fewer compound curves. In comparison, the 112 had 2,885 parts and 26,864 rivets, while the P.1035 was made of 969 unique parts with 11,543 rivets. The new straight-edged wing was a source of much of the savings; after building the first wings, Otto Butter reported that the reduction in complexity and rivet count (along with the Butter brothers' own explosive rivet system) saved an astonishing 1,150 man hours per wing.

Walter was killed in a car accident on 25 May 1937, and the design work was taken over by his twin brother Siegfried, who finished the final draft of the design later that year. Heinrich Hertel, a specialist an aircraft structures, also played a prominent role in the design. At the end of October the design was submitted to the RLM, complete with details on prototypes, delivery dates and prices for three aircraft delivered to the Rechlin test center. At this point, the aircraft was referred to as the He 113, but the "13" in the name was apparently enough to prompt Ernst Heinkel to ask for it to be changed to the He 100. It is reported that Ernst Heinkel lobbied for this "round" number in hopes it would improve the design's chances for production.

Design

In order to get the promised performance out of the aircraft, the design included a number of drag-reducing features. On the simple end was a well-faired cockpit, the absence of struts and other drag-inducing supports on the tail. The landing gear (including the tailwheel) was retractable and completely enclosed in flight.

There was also a serious shortage of advanced aero engines in Germany during the late 1930s. The He 100 used the same Daimler-Benz DB 601 engine as the Messerschmitt Bf 109 and Bf 110, and there was insufficient capacity to support another aircraft using the same engine. The only available alternate engine was the Junkers Jumo 211, and Heinkel was encouraged to consider its use in the He 100. However, the early Jumo 211 then available did not use a presurized cooling system, and it was therefore not suitable for the He 100's evaporative cooling system. Furthermore, a Jumo 211-powered He 100 would not have been able to outperform the contemporary DB 601-powered Bf 109 because the supercharger on the early Jumo 211 was not fully shrouded. From a practical matter, the He 100 used a novel cooling system that was complex, dependent upon many small pumps and difficult to maintain under field conditions. In order to reduce weight and frontal area, the engine was mounted directly to the forward fuselage, which was strengthened and literally tailored to the DB 601, as opposed to conventional mounting on engine bearers. The cowling was very tight-fitting, and as a result the aircraft has something of a slab-sided appearance.

In order to provide as much power as possible from the DB 601, the 100 used exhaust ejectors for a small amount of additional thrust. The supercharger inlet was moved from the normal position on the side of the cowling to a location in the leading edge of the left wing, which was also a feature of the earlier He 119. Although cleaner-looking, the long, curved induction pipe most likely negated any benefit.

For the rest of the designed performance increase, Walter turned to the somewhat risky and still experimental method of cooling the engine via evaporative cooling. Such systems had been in vogue in several countries at the time. Heinkel and the Günter brothers were avid proponents of the technology, and had previously used it on the He 119 with promising results. Evaporative or "steam" cooling promised a completely drag-free cooling system. Unfortunately, the systems also proved complex and terribly unreliable in practice. Huge expanses of the airframe's outer skin had to be devoted to cooling, which made such systems susceptible to combat damage. The DB 601 was a pressure-cooled engine in that the water/glycol coolant was kept in liquid form by pressure, even though its temperature was allowed to exceed the normal boiling point. Heinkel's system took advantage of that fact and the cooling energy loss associated with the phase change of the coolant as it boils. Following is a description of what is known about the cooling system used in the final version of Heinkel's system. It is based entirely on careful study of surviving photographs of the He 100, since no detail plans survive. The earlier prototypes varied, but they were all eventually modified to something close to the final standard before they were exported to the Soviet Union.

Coolant exits the DB 601 at two points located at the front of the engine and at the base of each cylinder block casting immediately adjacent to the crank case. In the Heinkel system, an "S"-shaped steel pipe took the coolant from each side of the engine to one of two steam separators mounted alongside the engine's reduction gear and immediately behind the propeller spinner. The separators, designed by engineers Jahn and Jahnke, accepted the water at about 110 °C (230 °F) and 1.4 bar (20.3 psi) of pressure. The vertically-mounted, tube-shaped separators contained a centrifugal impeller at the top connected to an impeller-type scavenge pump at the bottom. The coolant was expanded through the upper impeller where it lost pressure, boiled and cooled. The by product was mostly very hot coolant and some steam. The liquid coolant was slung by the centrifugal impeller to the sides of the separator where it fell by gravity to the bottom of the unit. There, it was pumped to header tanks located in the leading edges of both wings by the scavenge pump. The presence of the scavenge pump was necessary to ensure the entire separator did not simply fill up with high-pressure coolant coming from the engine.

Existing photographs of the engine bay of the final pre-production version of this system clearly show the liquid coolant from both separators was piped along the bottom left side of the engine compartment and into the right wing. The header tanks were located in the outer wing panels ahead of the main spar and immediately outboard of the main landing gear bays. The tanks extended over the same portion of the outer panel's span as the outer flaps. Coolant from the right wing header tank was pumped by a separate, electrical pump to the left wing header tank. Along the way from the right to left wing, the coolant passed through a conventional radiator mounted on the bottom of the fuselage. That radiator was retractable and intended for use only during ground-running or low-speed flight. Nevertheless, coolant passed through it whenever the engine was running and regardless of whether it was extended or retracted. In the retracted position, the radiator offered little cooling, but some heat was exchanged into the aft fuselage. Finally, a return tube connected the left wing's header tank to that on the right. This allowed the coolant to equalize between the two header tanks and circulate through the retractable radiator. The engine drew coolant directly from both header tanks through two separate pipes that ran through the main landing gear bays, up the firewall at the back of the engine compartment, and into the usual coolant intakes located at the top rear of the engine.

The steam collected in the separators was vented separately from the liquid coolant. The steam did not required mechanical pumping to do this, and the build up of pressure inside the separator was sufficient. The steam was piped down the lower right side of the engine bay and led into the open spaces between the upper and lower wing skins of the outer wing panels. There, it further expanded and condensed by cooling through the skins. The entire outer wing, both ahead of and behind the main spar, was used for this purpose covering that portion of the span containing the ailerons (the fuel was also carried entirely in the wings and occupied the areas behind the main spar in the center section and immediately ahead of the outboard flaps). The condensate was scavenged by electrically-driven centrifugal pumps and fed to the header tanks. Sources indicate as many as 22 separate pumps were used for this, each with their own attendant pilot light on the instrument panel, but it is not clear whether that number includes all of the pumps in the entire water- and oil-cooling systems or merely the number of pumps in the outer wing panels. The former is generally accepted.

Some sources state the outer wing panels used double skins top and bottom with the steam being ducted into a thin space between the outer and inner skins for cooling. A double-skinned panel was used in the oil cooling system, but surviving photographs of the wings demonstrate they were conventionally single-skinned, and the coolant was simply piped into the open spaces of the structure. Double skinning over such an extensive area would have made the aircraft unacceptably heavy. Furthermore, there was no access to the inner structure to repair damage, such as a bullet hole, from the inside as would be needed if the system used a double skin. A similar system was used by the earlier Supermarine Type 224. Contrary to assertions in some references, all of the He 100s that were built used the evaporative cooling system described above. A derivative of this system was also intended for a late-war project based on the He 100, designated P.1076.

Unlike the cooling fluid, oil cannot be allowed to boil. This presented a particular problem with DB 601-series engines, because oil is sprayed against the bottom of the pistons resulting in a considerable amount of heat being transferred to the oil as opposed to the coolant. The He 100's oil cooling system was conceptually similar to the water cooling system in that vapor was generated using the heat of the oil and condensed back to liquid by surface cooling through the skins of the airframe. A heat exchanger was used to cool the oil by boiling ethyl alcohol. The oil itself was simply piped to and from this exchanger, which was apparently located in the aft fuselage. The alcohol vapor was piped into the fixed portions of the horizontal and vertical stabilizers and into a double-skinned portion of the upper-aft fuselage behind the cockpit. This fuselage "turtle deck" panel was the only double-skinned portion of the aircraft's cooling system. The use of a double-skinned panel was possible here because the inside of panel was accessible in the event of repair. The retractable radiator below the fuselage was not used for the oil-cooling system. Condensed alcohol was collected by a series of bellows pumps and returned to a single header tank that fed the heat exchanger. Some sources speculate that a small air intake located at the bottom front of the engine cowl was used for an auxiliary oil cooler. No such cooler was fitted, nor was there room for one at that point. This small inlet served simply to admit cool air into what was a very hot portion of the engine bay. Immediately above this vent were the two steam separators, and immediately behind it were the hot coolant pipes coming from the separators.

[edit] World speed record

One aspect of the original Projekt 1035 was the intent to capture the absolute speed record for Heinkel and Germany. Both Messerschmitt and Heinkel vied for this record before the war. Messerschmitt ultimately won that battle with the first prototype of the Me-209, but the He 100 briefly held the record when Heinkel test pilot Hans Dieterle flew the eighth prototype to 746.606 km/h (463.919 mph) on 30 March 1939. The third and eighth prototypes were specially modified for speed with unique outer wing panels of reduced span. The third prototype crashed during testing. The record flight was made using a special version of the DB 601 engine that offered 2,010 kW/2,700 hp) and had a service life of just 30 minutes. Prior to setting this absolute speed record over a short, measured course, Ernst Udet flew the second prototype to a 100 km (62 mi) closed course record of 634.32 km/h (391.15 mph) on 5 June 1938. Udet's record was apparently set using a standard DB 601a engine.

There is a debate regarding the correct designation of the He 100 aircraft actually built. One group holds that all of the machines were either "Versuchs" or "trials" prototypes and pre-production "A-0" series machines. This is consistent with the RLM's normal practice of changing an aircraft's sub-designation only with a significant redesign, such as an engine change. All of the He 100s built were essentially the same, and even the prototypes were later updated to the production standard before they were exported to the Soviet Union. The second group holds that the Heinkel factory intended "A," "B," "C" and "D" series aircraft, and the final version was the "D." This camp also holds that there were separate "D-0" and "D-1" production runs, although in extremely limited numbers. Most literature follows the latter school of thought, Since the He 100 was never accepted for operational use by the Luftwaffe, it is unlikely there was ever an official resolution of this issue. The separate letter designations "A" through "D" appear to have come from internal Heinkel documents.

[edit] Prototypes

The first prototype He 100 V1 flew on 22 January 1938, only a week after its promised delivery date. The aircraft proved to be outstandingly fast. However, it continued to share a number of problems with the 112, notably a lack of directional stability. In addition, the Luftwaffe test pilots disliked the high wing loading, which resulted in landing speeds so great that they often had to use brakes right up to the last 100 m (330 ft) of the runway. The ground crews also disliked the design, complaining about the tight cowling which made servicing the engine difficult. The big problem turned out to be the cooling system, largely to no one's surprise. After a series of test flights V1 was sent to Rechlin in March.

The second prototype addressed the stability problems by changing the vertical stabilizer from a triangular form to a larger and more rectangular form. The oil-cooling system continued to be problematic, so it was removed and replaced with a small semi retractable radiator below the wing. It also received the still-experimental DB 601M engine which the aircraft was originally designed for. The M version was modified to run on "C3" fuel at 96 octane, which would allow it to run at higher power ratings in the future.

V2 was completed in March, but instead of moving to Rechlin it was kept at the factory for an attempt on the 100 km (62 mi) closed circuit speed record. A course was marked out on the Baltic coast between Wustrow and Müritz, 50 km (30 mi) apart, and the attempt was to be made at the aircraft's best altitude of 5,500 m (18,000 ft). After some time cleaning out the bugs the record attempt was set to be flown by Captain Herting, who had previously flown the aircraft several times.

At this point Ernst Udet showed up and asked to fly V2, after pointing out he had flown the V1 at Rechlin. He took over from Herting and flew the V2 to a new world 100 km (62 mi) closed circuit record on 5 June 1938, at 634.73 km/h (394.6 mph). Several of the cooling pumps failed on this flight as well, but Udet wasn't sure what the lights meant and simply ignored them.

The record was heavily publicized, but in the press the aircraft was referred to as the "He 112U". Apparently, the "U" stood for "Udet". At the time the 112 was still in production and looking for customers, so this was one way to boost sales of the older design. V2 was then moved to Rechlin for continued testing. Later in October, the aircraft was damaged on landing when the tail wheel didn't extend, and it is unclear if the damage was repaired.

The V3 prototype received the clipped racing wings, which reduced span and area from 9.4 m (30 ft 10 in) and 14.4 m² (155 ft²), to 7.6 m (24 ft 11 in) and 11 m² (118.4 ft²). The canopy was replaced with a much smaller and more rounded version, and all of the bumps and joints were puttied over and sanded down. The aircraft was equipped with the 601M and flown at the factory.

In August, the DB 601R engine arrived from Daimler-Benz and was installed. This version increased the maximum rpm from 2,200 to 3,000, and added methyl alcohol to the fuel mixture to improve cooling in the supercharger and thus increase boost. As a result, the output was boosted to 1,324 kW (1,776 hp), although it required constant maintenance and the fuel had to be drained completely after every flight. The aircraft was then moved to Warnemünde for the record attempt in September.

On one of the pre-record test flights by the Heinkel chief pilot, Gerhard Nitschke, the main gear failed to extend and ended up stuck half open. Since the aircraft could not be safely landed it was decided to have Nitschke bail out and let the aircraft crash in a safe spot on the airfield. Gerhard was injured when he hit the tail on the way out, and made no further record attempts.

V4 was to have been the only "production" prototype and was referred to as the "100B" model (V1 through V3 being "A" models). It was completed in the summer and delivered to Rechlin, so it wasn't available for modification into racing trim when V3 crashed. Although the aircraft was unarmed it was otherwise a service model with the 601M, and in testing over the summer it proved to be considerably faster than the Bf 109. At sea level, the aircraft could reach 560 km/h (348 mph), faster than the Bf 109E's speed at its best altitude. At  m (6,560 ft), it improved to 610 km/h (379 mph), topping out at 669 km/h (416 mph) at 4,999 m (16,400 ft) before falling again to 641 km/h (398 mph) at 8,001 m (26,250 ft). The aircraft had flown a number of times before its landing gear collapsed while standing on the pad on 22 October. The aircraft was later rebuilt and was flying by March 1939.

Although V4 was to have been the last of the prototypes in the original plans, production was allowed to continue with a new series of six aircraft. One of the airframes was selected to replace V3, and as luck would have it V8 was at the "right point" in its construction and was completed out of turn. It first flew on 1 December but this was with a standard DB 601Aa engine. The 601R was then put in the aircraft on 8 January 1939, and moved to a new course at Oranienberg. After several shakedown flights, Hans Dieterle flew to a new record on 30 March 1939, at 746.6 km/h (463.9 mph). Once again the aircraft was referred to as the He 112U in the press. It is unclear when happened to V8 in the end; it may have been used for crash testing.

V5 was completed like V4, and first flew on 16 November. It was later used in a film about V8's record attempt, in order to protect the record breaking aircraft. At this point, a number of changes were made to the design resulting in the "100C" model, and with the exception of V8 the rest of the prototypes were all delivered as the C standard.

V6 was first flown in February 1939, and after some test flights at the factory it was flown to Rechlin on 25 April. There it spent most of its time as an engine testbed. On 9 June, the gear failed inflight, but the pilot managed to land the aircraft with little damage, and it was returned to flying condition in six days.

V7 was completed on 24 May with a change to the oil cooling system. It was the first to be delivered with armament, consisting of two 20 mm MG FF cannons in the wings and four 7.92 mm (.312 in) MG 17 machine guns arranged around the engine cowling. This made the He 100 the most heavily armed fighter of its day. V7 was then flown to Rechlin where the armament was removed and the aircraft was used for a series of high speed test flights.

V9 was also completed and armed, but was used solely for crash testing and was "tested to destruction". V10 was originally to suffer a similar fate, but instead ended up being given the racing wings and canopy of the V8 and displayed in the German Museum in Munich as the record-setting "He 112U". It was later destroyed in a bombing attack.

Overheating problems and general failures with the cooling system motors continued to be a problem. Throughout the testing period, failures of the pumps ended flights early, although some of the test pilots simply starting ignoring them. In March, Kleinemeyer wrote a memo to Ernst Heinkel about the continuing problems, stating that Schwärzler had asked to be put on the problem.

Another problem that was never cured during the prototype stage was a rash of landing gear problems. Although the wide-set gear should have eliminated the collapse of landing gears that plagued the Bf 109, especially in the difficult takeoffs and landings, the He 100's landing gear was not built to withstand heavy use, and as a result they were no improvement over the Bf 109. V2, 3, 4 and 6 were all damaged to various degrees due to various gear failures, a full half of the prototypes.

He 100D-0

Throughout the prototype period the various models were given series designations (as noted above), and presented to the RLM as the basis for series production. The Luftwaffe never took them up on the offer. Heinkel had decided to build a total of 25 of the aircraft one way or the other, so with 10 down, there were another 15 of the latest model to go. In keeping with general practice, any series production is started with a limited run of "zero series" machines, and this resulted in the He 100D-0.

The D-0 was similar to the earlier C models, with a few notable changes. Primary among these was a larger vertical tail in order to finally solve the stability issues. In addition, the cockpit and canopy were slightly redesigned, with the pilot sitting high in a large canopy with excellent vision in all directions. The armament was reduced from the C model to one 20 mm MG/FF-M in the engine V firing through the propeller spinner, and two 7.92 mm (.312 in) MG 17s in the wings close to the fuselage.

The three D-0 aircraft were completed by the summer of 1939 and stayed at the Heinkel Marienehe plant for testing. They were later sold to the Japanese Imperial Navy to serve as pattern aircraft for a production line, and were shipped there in 1940. They received the designation AXHe.

He 100D-1

The final evolution of the short He 100 history is the D-1 model. As the name suggests the design was supposed to be very similar to the pre-production D-0s, the main planned change was to enlarge the horizontal stabilizer.

But the big change was the eventual abandonment of the surface cooling system, which proved to be too complex and failure prone. Instead an even larger version of the retractable radiator was installed, and this appeared to completely cure the problems. The radiator was inserted in a "plug" below the cockpit, and as a result the wings were widened slightly.

While the aircraft didn't match its design goal of 700 km/h (440 mph) once it was loaded down with weapons, the larger canopy and the radiator, it was still capable of speeds in the 644 km/h (400 mph) range. A low drag airframe is good for both speed and range, and as a result the He 100 had a combat radius between 900 and 1000 km compared to the Bf 109's 600 km ( mi). While not in the same league as the later escort fighters, this was at the time a superb range and may have offset the need for the Bf 110 to some degree. Finally, there were allegations that politics played a role in killing the He 100.

By this point, the war was underway, and as the Luftwaffe would not purchase the aircraft in its current form, the production line was shut down.

The remaining 12 He 100D-1c fighters were used to form Heinkel's Marienehe factory defense unit, flown by factory test pilots. They replaced the earlier He 112s that were used for the same purpose, and the 112s were later sold off. At this early stage in the war, there were no bombers venturing that far into Germany, and it appears that the unit never saw action. The eventual fate of the D-1s remains unknown. The aircraft were also put to an interesting propaganda/disinformation role, as the supposed Heinkel He 113.

Foreign use

When the war opened in 1939 Heinkel was allowed to look for foreign licensees for the design. Japanese and Soviet delegations visited the Marienehe factory in late October, and were both impressed with what they saw. Thus it was in foreign hands that the 100 finally saw use, although only in terms of adopted design features. Six He 100s were exported to the Soviet Union and three were exported to Japan. Although any Japanese aircraft that survived the war would have been destroyed by the allies, there is a possibility that parts of or even a complete He 100 may exist somewhere in storage in Russia. It is also possible the Russians made plans or blueprints of their He 100s while the design was being studied.

The Soviets were particularly interested in the surface cooling system, and in order to gain experience with it they purchased the six surviving prototypes (V1, V2, V4, V5, V6 and V7). After arriving in the USSR they were passed onto the TsAGI institute for study; there they were analyzed with He 100 features influencing a number of Soviet designs, notably the LaGG-3 and MiG-1. Although the surface cooling system wasn't copied, the addition of larger Soviet engines made up for the difference and the LaGG-3 was a reasonably good performer. It's perhaps ironic that German aircraft would later be shot down by German inspired aircraft.

The Japanese were also looking for new designs, notably those using inline engines where they had little experience. They purchased the three D-0s for 1.2 million RM, as well as a license for production and a set of jigs for another 1.8 million RM. The three D-0s arrived in Japan in May 1940 and were re-assembled at Kasumigaura. They were then delivered to the Japanese Naval Air Force where they were re-named AXHei, for "Experimental Heinkel Fighter". When referring to the German design the aircraft is called both the He 100 and He 113, with at least one set of plans bearing the later name.

In tests, the Navy was so impressed that they planned to put the aircraft into production as soon as possible as their land-based interceptor; unlike every other armed forces organization in the world, the Army and Navy both fielded complete land-based air forces. Hitachi won the contract for the aircraft and started construction of a factory in Chiba for its production. With the war in full swing in Europe, however, the jigs and plans never arrived. Why this wasn't sorted out is something of a mystery, and it appears there isn't enough information in the common sources to say for sure what happened.

The DB 601 engine design was far more advanced than any indigenous Japanese design, which tended to concentrate on air-cooled radial engines. To get a jump into the inline field, Kawasaki had already purchased the license for the 601A from Daimler Benz in 1938. The adoption process went smoothly, they adapted it to Japanese tooling and had it in production by late 1940 as the Ha-40.

At the same time Kawasaki was working on two parallel fighter efforts, the Ki-60 heavy fighter and the Ki-61 Hien. The former was abandoned after poor test results (the test pilots disliked the high wing loading) but work continued on the lightened Ki-61 with the Ha-40 engine. The Ki-61 was clearly influenced by the He 100.

Like the Ds, the Ki-61 lost the surface cooling system (although an early prototype may have included it), but is otherwise largely similar in design except for changes to the wing and vertical stabilizer. Since the Ki-61 was supposed to be lighter and offer better range than the Ki-60, the design had a longer and more tapered wing for better altitude performance. This also improved the handling and the aircraft was put into production. The Hien would prove to be the first of the Japanese aircraft that was truly equal to the contemporary US fighters.

Further developments

In late 1944, the RLM went to manufacturers for a new high-altitude fighter with excellent performance - the Ta 152H (a version of the Focke-Wulf Fw 190) was currently in limited production for just this task but Heinkel was contracted to design an aircraft, and Siegfried Günter was placed in charge of the new Projekt 1076.

The resulting design was similar to the He 100, but the many detail changes resulted in an aircraft that looked all new. It sported a new and longer wing for high-altitude work, which lost the gull wing bend and was swept forward slightly at 8°. Flaps or ailerons spanned the entire trailing edge of the wing giving it a rather modern appearance. The cockpit was pressurized for high-altitude flying, and covered with a small bubble canopy that was hinged to the side instead of sliding to the rear. Other changes that seem odd in retrospect is that the gear now retracted outward like the original Bf 109, and the surface cooling system was re-introduced. Planned armament was one 30 mm (1.18 in) MK 103 cannon firing through the propeller hub, and two wing mounted 30 mm (1.18 in) MK 108 cannons.

The use of one of three different engines was planned: the DB 603M with 1,361 kW (1,825 hp), the DB 603N with 2,051 kW (2,750 hp) or the Jumo 213E with 1,305 kW (1,750 hp). The 603M and 213E both supplied 1,566 kW (2,100 hp) using MW-50 water injection. Performance with the 603N was projected to be 880 km/h (546 mph), which would have stood as a record for many years even when faced with dedicated racing machines. Performance would still be excellent even with the far more likely 1,500 kW (2,000 hp) class engines, the 603M was projected to give it the high speed of 855 km/h (532 mph).

These figures are somewhat suspect though, and are likely just optimistic guesses that could not have been met - something Heinkel was famous for. Propellers lose efficiency as they approach the speed of sound, and eventually they no longer provide an increase in thrust for an increase in engine power. Even the advanced counter-rotating VDM design is unlikely to have been able to effect this problem too much.

The design apparently received low priority, and it was not completed by the end of the war. Siegfried Günter later completed the detailed drawings and plans for the Americans in mid-1945.

In 1939, it was reputedly one of the most advanced fighter designs, even faster than the later Fw 190, with performance unrivalled until the introduction of the Vought F4U Corsair in 1943. Nevertheless the aircraft was not ordered into production. The reasons the He 100 wasn't put into service seems to vary depending on the person telling the story, and picking any one version results in a firestorm of protest.

Some say it was politics that killed the He 100. However, this seems to stem primarily from Heinkel's own telling of the story, which in turn seems to be based on some general malaise over the He 112 debacle. The fact is that Heinkel was well respected within the establishment regardless of Messerschmitt's success with the Bf 109 and Bf 110, and this argument seems particularly weak.

Others blame the bizarre production line philosophy of the RLM, which valued huge numbers of single designs over a mix of different aircraft. This too seems somewhat suspect considering that the Fw 190 was purchased shortly after this story ends.

For these reasons, it seems safe to accept the RLM version of the story largely at face value; that the production problems with the DB series of engines was so acute that all other designs based on the engine were canceled. At the time the DB 601 engines were being used in both the Bf 109 and Bf 110 aircraft, and Daimler couldn't keep up with those demands alone. The RLM eventually forbade anyone but Messerschmitt from receiving any DB 601s, leading to the shelving of many designs from a number of vendors. Furthermore, the Bf 109 and Bf 110 were perceived as superior to their likely opponents, which made the requirement for an even more powerful aircraft less imperative.

The only option open to Heinkel was a switch to another engine, and the RLM expressed some interest in purchasing such a version of the He 100. At the time the only other useful inline was the Junkers Jumo 211, and even that was in short supply. However, the design of the He 100 made adaptation to the 211 difficult; both the cooling system and the engine mounts were designed for the 601, and a switch to the 211 would have required a redesign. Heinkel felt it wasn't worth the effort considering the aircraft would end up with inferior performance, and so the He 100 production ends on that sour note.

For this reason more than any other the Focke-Wulf Fw 190 became the next great aircraft of the Luftwaffe, as it was based around the otherwise unused Bramo 139 (and later BMW 801) radial engine. Although production of these engines was only starting, the lines for the airframes and aircraft could be geared up in parallel without interrupting production of any existing design, which was exactly what happened.

There is some disagreement on various measures depending on the source, this appears to be due to the limited number of records left for the aircraft. Common disagreements are on the service ceiling, and the empty weight is also often listed at 1,810 kg (3,990 lb). Another issue is the overall height of the aircraft which is sometimes listed at 2.5 m (8.2 ft). The other common figure of 3.6 m (11.8 ft) is used in this article because that is likely correct for the enlarged tail of the D-1 models.

Most importantly it should be noted that almost all of the aircraft underwent engine modifications and tweaking during their lifespan. The 650 km/h (400 mph) speed is almost universally quoted for the D-1 models, but it may be the case that this is the speed of the earlier and more streamlined V4 "A" model. In general, it appears likely that the AIR 40/237 number in the 628 km/h (390 mph) range is accurate for the production aircraft.

General characteristics

• Crew: one, pilot
• Length: 8.20 m (26 ft 11 in)
• Wingspan: 9.42 m (30 ft 11 in)
• Height: 3.60 m (11 ft 10 in)
• Wing area: 14.5 (156 ft)
• Empty weight: 2,070 kg (4,563 lb)
• Max takeoff weight: 2,500 kg (5,512 lb)
• Powerplant: 1× Daimler-Benz DB 601M liquid-cooled supercharged V12 engine, 876 kW (1,175 hp)

Performance

• Maximum speed: 668 km/h (362 kn, 416 mph)
• Range: 900 km (486 nmi, 560 mi)
• Service ceiling: 11,000 m (36,090 ft)

Armament

• 1 × 20 mm MG FF cannon
• 2 × 7.92 mm (.312 in) MG 17 machine guns