On the first of april (my birthday), I went for a quick flight. The first flight went without any incident. After a while I started my second flight. After a few minutes I started to get a warm feeling in my back. In didn't really pay much attention to it at that time because I thought I was just sweating and feeling hot. However a minute later I started to feel intense burning pain in my back. The pain was unbearable and I had to get to the ground as fast as possible. I cut my engine and went down as fast as I could (must have been my record). I couldn't handle the pain even as I was landed, I quickly got out of the harness and checked the engine.

I saw that in the back of my seat there was a huge hole (15 cm diameter) melted away straight through all the cloth and back protection.
That explained the intense pain. Now how did it get there?

After an inspection of the engine I noticed that the exhaust pipe was facing the wrong way, straight to the harness. This means the heated exhaust fumes blew directly on the harness at which the harness started melting.
I could not manually turn the exhaust so I didn't understand how this could be possible.

I was sure my exhaust was OK before launch (engine inspection). I got the proof since somebody was filming my takeoff and the exhaust could be seen as in the correct direction (pointing to the back).
So the exhaust must have been turning during flight, but it was still locked tight, so how could it turn?

There is a little rivet on the end of the engine which stops the inner part of the exhaust pipe to twist among the outer part. Although the rivet still looked OK and was attached properly and firmly it was broken on the inside. I could only verify that after completely removing the exhaust pipe.
So there was my problem.

Close call!!

Patrick Vandenbulcke
http://www.parafun.be

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