http://www.walter-rockets.i12.com/ato/me262i.htmIntroduction.
[Messerschmitt Me.262.C-1a Taking Off]
Very early in the development of the Messerschmitt Me.262, meetings between the RLM, Messerschmitt and BMW had proposed alternate power plants for the Me.262. However, the first serious proposals were published in the Project Bureau report of July 22nd 1943.
Three proposed designs were designated the Interceptor I, II and III. However, once work began on the first design in September 1944, it was initially called the Me.262.J1 or Heimatschützer I - "Home Defender I". One of the early series Me.262s Wkr.Nr 130186 had a modified rear fuselage, adapted to carry a redesigned HWK 109-509 motor, with the combustion chamber exhausting at the tail end, beneath a specially cut-away rudder. By the time the first flight had been made, the new model had been given the soubriquet, Me.262.C-1a.
History.
[Me.262.C-1a]
The prototype Me.262.C-1a, "186" was completed, making its first flight on October 16th 1944. But it was not until 27th February 1945 that the first take-off was made with the rocket motor. The take-off run was reduced by at least 200m, and with the turbojets operating, the three minute running of the rocket motor could push the Me.262.C-1a to 26,000 feet.
One recorded interception was made in the rocket-powered "186", when Major Heinz Bar of III./EJG2 took off from Lechfeld. Climbing to nearly 30,000 feet in a little over three minutes he was able to intercept and shoot down a USAF Thunderbolt.
The internal mounting of the HWK motor was problematic in terms of servicing, and severely limited the amount of the J2 fuel which could be carried for the turbo jets. Although there was a limited amount of success with this installation, the Interceptor II and Interceptor III projects were investigated as other important options.
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Description.
[HWK 109-509.S1 Main Installation]
The installation in the Heimatschützer I was a modification of the HWK 109-509.A-1, with the standard parts of the motor repositioned through the rear fuselage.
The combustion chamber (1) was supported on a three-tube thrust mounting (3), the forward of each being attached to a fuselage frame, with the standard HWK support tube (7) to carry the weight of the distant portion of the combustion unit.
The combustion chamber was cooled by the C-Stoff fuel.
[HWK 109-509.S1 Fuel Regulator]
The illustration on the right shows the fuel flow and pressure regulating valve, with the three stage T-Stoff fuel flow pipes towards the camera. Also plainly in view is the C-Stoff fuel filter, turned up from the standard HWK 109-509.A-1 position, in order to fit the reduced space in the installation.
Shown slightly more clearly are the thrust bearers (3), which take the place of the large, cast thrust plate in the "A-1" model. These stays are bolted to pressed brackets which are fixed to the skin and fuselage stringers.
Labelled in the picture are the push-pull dural rods (15) for the rudder and elevators. Also, the profile of the flat steel plate (5), which is fixed between the angle frames which make up the rear fuselage transport joint.
The steel sandwich plate is shaped and anchored, it's thought, to prevent distortion of the fuselage from the radial components of the thrust transmitted down the stays, when the rocket motor is under power.
Also shown, is the combustion chamber support tube (7), and its attachment point.
[HWK 109-509.S1 Fuselage Installation]
This is an illustration taken down the fuselage tunnel, from behind the wings, looking towards the tail and the Walter motor. Shown is the prominent steam generator (9), which provides motive power for the fuel pump turbine. The pump itself is not clearly visible, but it is mounted on a frame (8), suspended around the thrust tube attachment points. This motor seems to be an "A-1" derivative, as there does not appear to be a T-Stoff starter tank, and the picture does seem to show an electric starter geared onto the end of the T-Stoff pump.
Item (17) is the rudder trim control, and the very large diameter pipes in the well of the fuselage (18) are the fuel pipes leading the T-Stoff and C-Stoff from the fuselage tanks.
[HWK 109-509.S1 Exhaust Venturi]
This final picture shows how the Walter combustion chamber exhaust is fitted into the rear of the fuselage. The rudder was cut away at the base to keep the structure out of the severe rocket blast.
Shown in the picture, is the bottom rudder hinge point (12).
The Me.262's fuel tanks were modified to carry the extra fuels. The forward 900 litre tank was replaced with a non-corrosive tank of the same capacity for the T-Stoff. The 250 litre tank below the cockpit was kept for J2 fuel, as was the 900 litre tank behind the cockpit. The rearmost tank was replaced with a 625 litre tank for the C-Stoff.
At least one author adds a note that two drop tanks of T-Stoff were added below the fuselage nose, but the RAE's investigation of the Me.262.C-1a, was confined to the remains of the fuselage which they captured, so does not mention any additional tanks.
The additional motor controls in the cockpit were arranged on the left side above the pilot's throttle quadrant.
Interestingly the Me.262.C-1a had a duplicate set of 770x270 main wheels fitted alongside the standard undercarriage wheels, which were jettisonable after take-off.
