Friday, 5 February 2016

Arado Ar 234.The Begining of Blitz. Part 1.

Text found in the internet.

"This document with excerpts from several books has been created under ‘fair use’ copyright as background information for trips to Alt Lönnewitz and Rheine that we made in 2015 as part of a study project. All copyrights remain with the copyright holders named in the references. If you wish to use copyrighted material from this document for purposes of your own that go beyond ‘fair use’, you must obtain permission from the copyright owners.


Arado 234A


In the late 1930s turbojet engines then under development by BMW and Junkers became reliable enough to be used for aircraft. The Reich Air Ministry (Reichsluftfahrtministerium or RLM) invited tenders for the design of a jet powered high-speed fighter and reconnaissance aircraft. The bid for the fighter design was won by the Messerschmitt factory and resulted in the creation of the Messerschmitt Me 262 Schwalbe. The only response for a reconnaissance aircraft came from Arado which submitted the E.370/IV project led by Professor Walter Blume along with Hans Rebeski and Rudinger Kosin.



Early jet engine developments 

Heinkel He178
Heinkel He280
Concept of the turbojet engine originated in 1935 from Hans von Obain and Max Hahn in Göttingen and was further developed by Heinkel. 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. On 27 August 1939 the Heinkel He 178 became the first aircraft to take off with this type of powerplant. The German Air Ministry was not very interested in the Heinkel, and the He 178 never materialized beyond its prototype stage. The later twin-turbojet fighter prototype He 280 lost the competition with the Messerschmitt Me 262 fighter.

In October 1941, they presented a project for a single-seat, cantilever high-wing monoplane of monococque construction, with straight wings and single-fin tail unit. The aircraft was to be propelled by two BMW P 3302 jet engines located in underwing nacelles. The fuselage, of cylindrical cross-section, was to house a pressurized cockpit, three fuel tanks and two Rb 50/30 (or Rb 70/30) photographic cameras. Defensive armament was to consist of one fixed 13mm MG 131 machine gun mounted in the aft fuselage. Total fuel capacity was 4,000 liters.
The design of the aircraft's landing gear changed several times. The team worked on several solutions: a single retractable fuselage skid; a bogie of small auxiliary wheels mounted underneath the fuselage with skids beneath the engine nacelles; and a tricycle landing skids mounted beneath the fuselage and engine nacelles. Eventually, the last variant was chosen. The rather basic landing gear had its advantages. It constituted only 3% of the aircraft's take-off weight. The airplane would taxi and takeoff atop a wheeled trolley that the pilot jettisoned as the jet left the runway. Ground crews recovered the trolley and refurbished it for the next flight.
On 17th November 1941, Ernst Udet, who was the director-general of equipment for the Luftwaffe, committed suicide. Udet's successor, Erhard Milch, visited the Arado plant in Brandenburg on the 4th February 1942. Milch was shown the E.370/IV project, and he was impressed by it. Milch ordered a full-scale wooden mock-up to be built. In April of 1942, the RLM ordered six prototypes, designated Arado 234. Throughout 1942, scale models of the Arado 234 were submitted to windtunnel tests.
BMW engine development problems repeatedly slowed flight testing the first Ar 234. While the engines were growing in diameter, wider engine nacelles became necessary, which on its turn affected the aerodynamics of the aircraft. Arado decided to employ the Junkers Jumo turbojet, for which the aircraft's wings had to be re-designed. On 28th December 1942 the RLM ordered an additional 14 prototypes. However, the RLM was not satisfied with the aircraft's undercarriage system. Arado designed the Ar 234B variant with a tricycle retractable landing gear, for which the fuselage had to be widened by 21 cm. The project was approved, and on 9th February 1943 the RLM ordered two prototypes of the new variant, which was to be a bomber version of the basic reconnaissance design.
Tests of the delivered Jumo 004 engines showed that the engines did not deliver the necessary thrust. Additional thrust at take-off was to be delivered by two external rocket boosters. The boosters were parachuted to the ground once their fuel was consumed. Another alternative that was proposed by Arado was the installation of four BMW engines instead of two Jumo engines, but this had to be postponed until the BMW power plants would be reliable enough.

Walter HWK 109-500 

Walter HWK 109-500
Puting in place under the wing
The Walter HWK 109-500 was a liquid fuelled rocket motor developed by Walterwerke in Germany during the Second World War. During development the model was designated RI-201. Once accepted for production, the RLM gave it the designation HWK 109-500. Production was given to the Heinkel werke at Jenbach, who manufactured around 6,000 units during the course of the war.
The liquid-fuel rocket booster shortened the take-off distance and facilited take-off with heavy load. In front of the nacelle a parachute was mounted, enabling it to land softly after having been jettisoned from the aircraft. It allowed multiple use of the same engine. The propellant consisted of three components. The propellant components were forced to the combustion chamber by compressed air. The combustion chamber was cooled with hydrogen peroxide.

On Sunday 18th July 1943 the dismantled prototype Arado 234 V1 was delivered to Rheine aerodrome, where it was re-assembled. The aircraft had previously been shipped unassembled in an Ar 232 to Rheine, since Brandenburg did not have a runway of adequate length. Three days later the Jumo 004 engines had been installed and taxiing tests were conducted. During another ground test on 26th July a loose cowling caused the port engine to catch fire. Following repairs, the Ar 234 V1 was test flown for the first time on 30th July by Heinz Selle. At 500 meters the pilot released the trolley, but it smashed to the ground due to a faulty parachute deployment. The flight time of the first flight was 14 minutes.
Pic 1
Pic 2
Pic 3
Pic1,2,3,4: Arado Ar 234 V1 (WNr. 130 001) fitted with tricycle take-off trolley
The airplane was test flown for the second time on 10th August. Again the take-off trolley was wrecked due to faulty parachutes. The second flight was 55 minutes. The experience gathered during the first two flights made the designers revise the procedure for releasing the trolley. Now it was to be dropped immediately after leaving the ground. On 29th August 1943 Heinz Selle took off for his third test flight, following successfully the new procedure of releasing the take-off trolley. While Heinz approached the airport for landing he attempted to select more power to stay on the approach path in vain. He crash landed the Ar 232 V1, and it was damaged beyond repair.
In early September 1943 the second prototype was completed, however the engines had to be replaced. The second prototype was test flown on 13th September by Selle from Brandenburg to Alt Lönnewitz, where he performed two more test flights the following days. On 29th August Selle flew the third prototype for the first time from Brandenburg to Alt Lönnewitz. The following day another flight took place. During take-off the trolley, dropped from a height of approximately 1.5 - 2 meters, flipped onto its back and was again wrecked. As a result, it was recommended that the trolley be released while it was still rolling on the ground.

On 1st October 1943 Selle took off for hist fifth flight at the controls of the Ar 234 V2 prototype. The objective was to test the machine's climb rate. In the climb at an altitude of approximately 29,000 ft, the port engine cut out. Selle glided down, while reporting fluttering of the elevators. A fire inside the port wing caused the plane to crash, killing Selle and delaying the programme by another month. Following the crash, various improvements to the other prototypes were made.

The Ar 234 V3 was flown again on 11th November 1943 for a 17 minutes flight with Arado's new chief test pilot Walter Kröger at the controls. The following day the aircraft flew from Alt Lönnewitz to Jüterborg by Johan Ubbo Janssen, a test pilot who had just joined the Ar 234 programme. The return flight to Alt Lönnewitz was delayed until 15th November 1943. On 21st November the dismantled Ar 234 V3 was delivered to Insterburg in East Prussia, where it was re-assembled. On 26th November it was put on display with many other new aircraft and prototypes at an exhibition for the head of state and other high ranking Germans. The ruler of the Reich promised Arado all the support necessary, ordering at least 200 Ar 234s of the bomber variant to be ready by the end of 1944.


Arado Ar 234 V5 (WNr. 130 005) taking-off from a trolley

Another prototype, the Arado Ar 234 V4, was first flown on 26th November 1943 by Johan Ubbo Janssen. Shortly before landing the machine developed a malfunction in its port engine. The aircraft was not ready to perform a second flight until 6th January 1944. The fifth prototype, the Arado Ar 234 V5, was first test-flown on 22nd December 1943 by Janssen. The aircraft was fitted with Junkers Jumo 004B-0 engines. At landing the port engine failed to revert to idle revolutions, and the aircraft touched down diagonally to the runway resulting in damage to the port wing. After necessary repairs the V5 prototype flew again on 21st January 1944.
On 22nd February 1944, during the sixth flight of the Ar 234 V5, Janssen noticed some vibrations in the starboard wing and tailplane. These were caused by a piece of engine cowling that had torn loose. During touchdown the main landing skid retracted, resulting in damage to the lower part of the cockpit glazing and fuselage, as well as to the starboard wing and stabilizing skid. Two days later Janssen conducted the first flight test of the braking parachute that had been mounted in the Ar 234 V3. The parachute was fitted into a container located in the lower, rear part of the fuselage. Tests of the braking parachute proved that it performed well and that it could be mounted on series production machines equipped with a conventional undercarriage.
The last intensive tests of Ar 234A prototypes equipped with two Jumo 004 engines and a take-off trolley took place in April 1944. The Ar 234 V5 was twice slightly damaged. The first incident occured on 2nd April 1944, during the aircraft's eight flight. At take-off from Alt Lönnewitz, Janssen failed to jettison the trolley. Once airborne, he attempted to loose the trolley by rapidly accelerating and decelerating, but did not succeed. Janssen landed on the trolley, but without braking the aircraft rolled the entire length of the runway to come to a halt in a adjacent field with some minor damage. The other accident occurred on 24th April, during a landing following the thirteenth flight. This time, Günter Eheim flew the aircraft. The main landing skid did not extend fully, resulting in damage to the lower part of the fuselage.
Continuing problems with the Ar 234A's unconventional undercarriage system led to the decision to discontinue development of the variant. Walter Kröger flew the last prototype, Ar 234 V7, equipped with Jumo 004B-0 engines on 22nd June 1944. A week later, the aircraft was passed to an operational unit.

References

  • Arado: Geschichte eines Flugzeugwerks; author Jörg Armin Kranzhoff
  • German Aircraft Industry and Production 1933 - 1945; authors Ferenc A. Vajda, Peter Dancey
  • Aircraft Profile No. 215: Arado 234 Blitz; author Richard P. Bateson
  • Arado 234 Blitz (vol I & II); authors Marek J. Murawski, Marek Rys
  • Blitz!: Germany's Arado Ar 234 Jet Bomber; authors J. Richard Smith, Eddie J. Creek
  • American Raiders; author Wolfgang W.E. Samuel
  • airandspace.si.edu
  • wikipedia.org"