Walter M701-500

This is a Walter (Motorlet) M701-500 turbojet that I have recently acquired. This was quite a bargain as the engine comes complete (including a Starter!) in addition to the associated airframe bulkhead. There are a lot of bits attached that we will not need such as the hydraulic pump + hoses/pipes, electrical connectors, transducers etc… these will be all chucked into my spares bin.

The engine was made in Czecheslovakia and used in the Aero L29 Soviet Trainer Jet, its a real bit of Cold War history. It seems it has spent most of it’s days with the Romanian Airforce.

The M701 is a very basic yet rugged little engine; it has a single centrifugal compressor, 7 combustion chambers and a turbine. The design is very similar to the Rolls Royce Derwent (they probably nicked the plans during the Cold War!!). It should produce about 1900 lbs of thrust at full RPM.

Above you can see some the goodies that have come with the engine. The hydraulic oil tank is in the top of the picture and some sort of hydraulic pressure controller/transducer type gizmo is in the foreground.My first job is to strip off the bulkhead and see if we can then get her up and running. Hopefully there shouldn’t be too much to do as I plan to use the control box from the Viper.

Here’s the Walter after I’ve stripped off all the ancillaries. In the centre is the fuel pump, below you can see the oil tank containing the pump and filters. On the right of the engine, not seen in this view, is the ignition excitor (that’s a bit faulty so we’re using a seperate unit). The starter motor is in the nose-cone, more on that later. It’s a great looking engine, hope it works!

Having stripped off the bulkhead and accessories the next stage was to dis-inhibit the fuel and oil system. This was quite easily done, as the oil filters are easily removable. To clear the fuel system required motoring the engine with the starter, to do this I connected up a PWM motor controller to act as a soft start and to vary the speed.

Problem…..the motor works but the rotating assembly does not rotate. This could be a problem with the clutch or something more sinister.Time to strip down the front nose cone and remove the starter and clutch to see what’s going on.

Having taken the clutch and epicyclic gear mechanism off, the cause of the problem is obvious….a broken drive shaft. This may explain why the engine was removed from the airframe in the first place. Obtaining a replacement could be tricky as we do not know the part number. I have decided to take my chances and have it professionally repaired.

Well, I have had the shaft repaired, Roger at Cross Engineering in Gorseinon has done a superb job. The shaft is back in and the clutch re-assembled with the starter motor back in position.  The engine fuel system has been primed so all we have to do is connect everything up and see if she fires-up.

Success!!!! despite an initial hot start because of a wrong throttle setting the second attempt the engine fired up perfectly to reach its idle speed.

You can watch the first start up on Youtube

This video shows a more controlled run-up. I had to limit the power to 60% RPM as the engine started to lift -off the pallet !!

23 May 2010

Had another look at the ignition exciter of the M701. The unit does not work although the oscillator appears to function. I was wondering if the capacitors had given up the ghost. Took the unit off the engine and opened the casing with a grinder. As suspected the whole thing is sealed solid in resin, impossible to remove any of the components……bin. Will try and find a suitable replacement from E-Bay.

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Jet Engine Projects from Justin Woolgar