The Walter 109-509.A-1 motor was an efficient power plant that worked to specification. However, for pilots, the lack of endurance, although important, was secondary to the tendancy for the HWK 109-509.A-1 to stall under manouvering - and this might include take-off. If the Walter rocket motor failed on take-off, the pilot was in serious trouble; with a full load of fuel and no chance to restart the motor.

The main weakness in the Me.163 system, was the tendancy for air to be drawn into the propellant system, mainly during manouvering, when fluid lifted in the tanks under negative acceleration. At best, air in the suction lines caused the pump to fail to prime properly giving irregularities in the propellant flow, causing uneven combustion and loss of performance; or at worst stoppages. Whilst tackling this problem, Walterwerke were also keen to boost the performance of the motor, by improving the thrust and/or reducing the weight.

To produce the "A-2", Walters changed the 109-509 motor design to remove the heavy gearbox and accessories unit and add a method of drawing air from the propellant lines.

Main Features

• Single unit, box frame design
• Removed accessories unit and gearbox
• Electrical starter motor removed
• T-Stoff starter
• Lower unit weight
• Steam ejectors added

In the above pair of pictures, the "A-1" motor is on the left, and the "A-2" motor the right. On the right, notice that the motor is missing the electrical starter motor and the large silver gearbox and accessories unit to which it is connected; compare this with the motor on the left.

Instead, the motor on the right has a new device, the small silver box where the accessories unit should be - this is the steam ejector for the T-Stoff line.

One final thing to note, is that the steam generator on the "A-1" motor is visible above the box frame. Although the angle of the photograph on the "A-2" is slightly lower, the steam generator is now reversed, below a T-Stoff starting tank, and not visible above the motor frame.

The picture above of the "A-2" does not show a typical "A-2" motor. It is from the motor at the Museum of Flight in Scotland, which has a non-standard T-Stoff cooling system, and so the fuel flow around the motor in this example differs from a standard production motor.

Walter 109-509.A-2 Schematic   By following this link, you can jump to a page with a diagramme of the "A-2" motor which has been taken from an RAE report. Although the image takes a while to download, it is a good illustration of the systems of the Walter 109-509 series motors, and it includes the steam ejectors.

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