Introduction.

In common with a number of projects, Walterwerke put a lot of time and effort into designing motors best fitted for the job required for the Natter. As mentioned, the initial design was to have used the HWK 109-509.C dual chamber motor in the production Natter. As this was not ready when the Natter became available for powered flight testing, another motor was used.

The majority of the technical literature so far studied seems to point to Walterwerke working on a derivative of the 109-509.A-2 for the Natter, to be called the "109-509.E". Why time and resources were spent developing this motor, when effort could have been put into advancing the 109-509.C, (which was designed to be used in a range of other, very high priority projects) is so far a mystery. But they did.

The next bone of contention, is were any of the 109-509.E motors used? Beeton says no, although there is evidence that these motors were being worked on, and intended to be built into the airframe, as 1945 diagrammes exist with the 109-509.E installed. But, being one of the few writers to even mention these motors, I'm about to say that I'm not sure any of them were used. In common with a number of Walterwerke motors, I don't think it was ready in time, and I think Beeton is right.

To see a further discussion on the subject of the Walter motor for the Natter, follow this link.

Evidence? The few pictures I have seen of Natters in production are exceedingly poor quality reproductions in books - it would be nice to see an original photographic print which would show some detail - but on fairly close examination, the Walter motors shown appear to be standard 109-509.A-1 motors (not even A-2 motors) with a modification to the combustion chamber support tube.

The picture shown here on the left, is a common reproduction, showing Natters in final assembly. Two Walter motors are shown, one fitted to the Natter which the man is working on, and one on a stand just behind him. Both of them are single chamber motors.

This image on the left, isn't an easy illustration to decipher, but it shows a close-up from the image above, of the motor on the stand.

By looking carefully at the left of the picture, you can see that the motor quite clearly shows a 109-509.A-1 steam generator, mounted high on the port side of the thrust plate.

The combustion chamber support tube is now on the upper side (rather than the lower side for the Messerschmitt Me.163), although in this picture, I don't beleive it is connected to anything. The motor stand is taking the weight of the motor, and the tube is just rested on the top of the mechanical linkage from the fuel control valve to the steam control valve which runs across the top of the thrust plate. Compare it with the angle of the support tube on the motor in the picture below, which is bolted to the airframe.

For me, this picture isn't clear enough - interpret it how you may, and it will probably give the answer you need. It shows the other Walter motor, the one fitted to the Natter airframe the man is working on.

However, sticking my neck on the block, I think I can make out another grey area just aft of the top of the thrust plate, which looks to be in the same place I would expect a 109-509.A-1 steam generator to be. If it was an "A-2" or an "E" model, the grey shape would be different. I think this is another Walter HWK 109-509.A-1.

Discussion.

So what is an "HWK 109.509.A-2E"? To be honest, I'm not sure. I know of two different names used for Walter motors destined for use in the Natter, both of which imply that they are "A-2" derivatives.

The evidence so far, is that the "109-509.E" motor was in preparation. I have no idea what a "109-509.A-2E" is. The only motor I have seen appears to be a slightly modified 109-509.A-1. Is this an "A-2E"? I'm not sure.

So for the time being, until I find some clarification, or another motor, I'll call this modified "A-1" an "A-2E" even though I know very well that the name is all wrong; just for the sake of making it different from the Messerschmitt Me.163 standard motor.

If you have any pictures, or can point me to any resources, just let me know, as this is a knotty problem I'd love to know more about.

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