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Shut-off for F2D-Combat

Test flying

Finally, time to test the shut-off system.

Sunday, 25th of March, very nice weather, 10-12 degrees (spring is finally here!).
Low wind from the east. The flying field is located close to a small airport so the wind direction is very important for the test. The most common weather here is strong wind from the west, so we are very lucky.

The plan is first to make a flight with exactly 40 ml in the bladder. Measure the run time and then make an other flight with the same amount of fuel.
With just enough fuel for few seconds left we will let go of the handle. If the shut-off system is working it should stop the engine. If not, the engine will run out of fuel a few seconds later and model will land not too far away.

First we had some problems with getting the model into the air. The shut-off is activated to soon and kills the engine before the model builds up enough speed to keep the spring open.
With a piece of piano wire and a streamer we improvised a delay in the system and finally we managed to get airborne. As planned I made some loopings over my head and when the time was up, I let go of the handle.

And . . . yes!!! . . . the engine stopped !

The model soared in big circles, stabilized by the lines and the handle, and landed safely about 100 m away.

The engine was very quick to stop. Much quicker than expected. From the video you can see (and hear) that the engine stops only 1.5 seconds after the handle has left the hand.

We did three more "fly-away" tests, all with the same result. So 4 out of 4 times this shut-off did what it was designed to.

Let go of the handel

See the video (divx, 2.8 Mb) from one of the tests.

You will also find it on YouTube:

Later that day we got some more wind (approximately 8 m/s) and I tried to fly small loopings directly into the wind. Trying to find out if the shut-off would stop the engine due to low line tension.
To my surprise I succeeded a couple of times.
At the tests last year I could fly the model into the wind, lose all line tension but catch the model again without shutting off the engine.

At the end of the day we had demonstrated that this shut-off system is working when the pilot loose the handle.
We still need to solve the problem with the engine being killed at the start and the problem with low line tension when flying small loops into the wind.

Update, 30/6 -07:
After the test flying I realized that the adjustment of the spring that block the system was set lower than the line tension that could hold the fuel line open. The result was that the model never got a chance to build up speed before the fuel line was pinched. I adjusted the lock to be activated at a higher line tension and the problem was solved.

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Shut-off start - F2D.dk