This motor has been on display at Cosford for a number of years. It is obviously a Walter motor with auxilliary combustion chamber, mounted below the main combustion chamber.

The absence of the girder frame, the fact that the fuel control valve unit is arranged "horizontally", not vertically and the completely different layout of the C-Stoff and T-Stoff pipes leads to the conclusion that this is a "C" series motor.

The lack of a well-defined motor thrust plate with the mounting bolts being towards the very front of the unit, with almost all of the component parts of the motor aft of the mounting, defines the "C Series". In comparison, for the "A" and "B" Series motors, the thrust plate divides the motor into a "fore and aft" configuration, the thrust tube and combustion chamber being aft and the main motor components being forward of the fuselage mounting.

There is no discernable manufacturer's plate (nor an obvious place where it should be), but this is certainly the only "C" Series motor so far confirmed in existance.

Known History.

At the time of writing, no documentation for this particular exhibit has been confirmed. Post capitulation reports show that at Walterwerke in Kiel, teams of British intelligence officers ran an HWk 109-509.C on a regular basis. At the factory's close, a large amount of material was brought to Britain, including a number of captured projects. A Walter 109-509.C motor was photographed extensively by the RAE, and displayed in the Foreign Aircraft Exhibition in Autumn 1945.

From 1947, the RPE ("Rocket Projectile Establishment") at Westcott in Buckinghamshire, carried a collection of captured rocket motors in their Aircraftsman Hall "museum", which was almost certainly the preserved residue of the RAE's investigative work on German rockets after the war. No paperwork has been unearthed as yet, but photographs exist showing an HWK 109.509.C motor at the RPE England in 1972, before its closure. The vast majority of the survivors from this collection were sent to the RAF Museum and used as the core exhibits to form the Missile Collection at the RAF Museum in Cosford. With no other motor of this type having been identified, it is possibly safe to say that the example in Cosford can trace its history at least back to the RAE.

The following photographs were taken in 2008, at RAF Museum Cosford's Missile Collection.

Description.

This motor is a well preserved example, and quite possibly unique.

All photographs © Shamus Reddin

This view shows the main part of the motor. The horizontally lying, silver unit just visible behind the aluminium pipes, towards the left, is the main fuel flow and pressure equalising unit. The larger diameter silver pipe nearest the camera, is the T-Stoff output pipe rising from the main T-Stoff pump. First, second and third stage T-Stoff propellant delivery pipes for the main combustion unit are shown near it.

Although the steam generator itself is hidden, the T-Stoff starting gravity tank is prominent, mounted vertically just above the rearmost part of the motor frame. Also plainly visible is the cruising combustion chamber, slung below the main combustion chamber.

Viewed from the forward part of the motor looking aft, the fuel pump dominates the lower half of the motor. Of the propellant turbo-pump unit, the T-Stoff pump is the section to to the right with its bifurcated output. The largest diameter aluminium pipe to the right is the T-Stoff pump outlet, rising to the fuel flow-pressure regulator. The three, smaller diameter aluminium, closely grouped pipes carry T-Stoff, curving to the left, to pass down through to the combustion chamber.

On the left of the turbo-pump unit as we look at it, is the C-Stoff pump. Also shown are the corresponding C-Stoff pipes (each of a smaller, different diameter) all painted a darker colour, which curve right and down, to lead out through the centre of the main thrust tube to the combustion chamber.

Just Visible towards the left, inboard of the C-Stoff pump output pipe, is the largest diameter, curving steam pipe which delivers the steam to drive the turbine of the fuel pump.

This image shows an additonal view of the motor control mechanism, with the turbine speed control visible in the middle of the photograph.

This close-up of the motor illustrates the principle differences of the "C" unit. There is no obvious "box" frame, the prominent accessories gearbox unit is missing, and the steam generator is "inverted" and served by a T-Stoff header tank.

In this view the main elements of the main rocket motor are very clearly shown. At the bottom left, is the main turbo-pump unit. In the centre of the photograph is the modified turbine speed control unit. The top section controls the flow of T-Stoff to the main combustion chamber, and you can make out another section on the under surface which controls the flow of T-Stoff to the auxilliary chamber. To the right, just visible as a horizontal unit with two horizontal aluminium T-Stoff pipes emerging, is the secondary fuel-flow and pressure regulating unit for the auxilliary combustion chamber.

Due to the "double-circuit" propellant control systems for main and auxilliary combustion chambers, to the left of the centre is a vertical column of multiple control linkages which carry the simple movement of the pilot's throttle control through to the various elements of the engine control system.

The aluminium tank to the right, is the T-Stoff gravity header tank for the steam generator.

In this view, looking down onto the top of the motor, is visible the control linkage between the C-Stoff fuel control valve at the right of the shot and the T-Stoff header tank and turbine speed control just out of view to the top left of the picture.

The looped black pipe at the top of the picture leads C-Stoff out to the combustion chamber for cooling, the return flow entering the fuel filter from the right.

The fuel flow control valve might be difficult to make out, but is lying horizontally below the C-Stoff filter. However, the three stage C-Stoff control valve is shown, with its multiple stage output.

Here is the auxilliary "cruising" combustion chamber, slung below the main combustion chamber. This combustion chamber is a single-stage unit, without variable thrust - either not used, or operating on full thrust.

Running into the head of the combustion chamber are three aluminium T-Stoff pipes, and two smaller diameter lines. These are the combustion chamber pressure monitoring line, and a steam line to flush through the combustion chamber. This is used to purge the combustion space of residual liquids before the propellant flow for combustion is begun. Removing residual propellant prevents premature or uncontrolled decomposition which could result in an explosion.

The steel, black-painted line, is the C-Stoff outflow from the auxilliary control unit to the auxilliary combustion chamber's own cooling jacket. One thing to note, is that there is no return flow pipe. Not visible in this illustration, but there is a small loop which takes the cooling C-Stoff directly from the cooling space to the combustion head for controlled delivery to the combustion space. Sufficient cooling propellant is used to sustain the single-stage combustion thrust.

Additional History

For many years, the HWK 109-509.C was displayed at Cosford painted in red, yellow, silver and blue colours. These were used to show the primary and auxilliary propellant circuits, T-Stoff and C-Stoff flow circuits. Colourful it might have been, but authentic it was not. It was thought that maybe these colours had been painted while the unit was at Westcott, being used as an instructional unit. However, it seems that the colours had been painted after the arrival at Cosford.

This picture (left) is a small part from an illustration in "Top Secret Bird" by Wolfgang Späte (p264, 1989 Pictorial Histories Edition), taken in 1987, which shows the HWK 109-509.C at Cosford. As you can see, it clearly shows the motor before it was painted in its garish colour scheme as shown, indicating that the motor was painted by staff whilst already at the Cosford Museum.

Photographs © Shamus Reddin

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