... I saw this thread, and thought this may be a good place to post this potential issue
before it happens to someone in the air. Some ignitions, electronic, and computer
based, (as in some automotive type ECUs) Will throw out one random spark when
switched on. As a rule this usually isn't a big problem, but under certain conditions
it can be. If the throttle is in idle position it is less likely to happen, but if it is much
above idle the fuel system is feeding fuel and unburned air into the engine and loading
up the muffler and exhaust system with this volatile mixture. If your ignition is one that
throes this random spark, it can ignite this mixture inside the muffler, in essence making
your muffler into a bomb, and potentially putting you and your aircraft in harms way.
You may wish to investigate this further if you are not using magnetos, or have an
aftermarket system installed. A good practice is to try any action of this type on the
ground a couple of times, prior to doing it while airborne. This scenario is fresh in my
mind, as it recently happened at my home airport to a fellow with his RV-10. This
resulted in some considerable damages to his aircraft, muffler, lower cowl, and a
small fire. Needless to say it would have been frightening at best were he airborne.
Stay Safe, Allan--