In a message dated 00-01-09 14:53:09 EST, you write: > Here's my first question: If you turn the prop "backwards" with the mag > switch 'on' and it hits compression on one cylinder and 'bounces' back > in the forward direction and slips out of your hands, (putting you > 'off-balance) couldn't this be dangerous since now the impulse couplings > on the mags would be active? Of course if the mag switch is 'off' then
The impulse couplings are not much of an issue in this case. They don't come into play until about 25 degrees BTDC and fire at about TDC. If you don't move the prop in the correct direction, starting before they engage and folllowing through the lag angle (to roughly TDC) then they are not contributing. HOWEVER, it is possible to fire a plug without the impulse coupling, by turning the engine through the angle where the ignition points open IN EITHER DIRECTION. If you don't agree, take a plug lead in your hand and try it. > it would be okay as long as the grounding works properly. Many one handed pilots can attest to the fact that you should never rely on the grounded p-leads for anything. > Question #2: By turning the engine backwards, the oil pump is also > turning backwards and not pumping any oil into the engine. Wouldn't it > be better to leave the mag switch 'off' and turn the prop 'forward' for > a few blades and lube the cylinders before starting the engine? You would have to turn about 50 blades through to move a significant amount of oil. Some benefits are spreading what ever oil is already in the cylinders, a quick "Armstrong" compression test, and priming if you have a Stromberg and no primer, or if you have a primer and don't want to use it. (You're correct about radials. The bottom cylinder(s) can collect enough oil or fuel or both to bend a rod.) This reminds me of something I saw a couple of months ago. A couple of guys were getting ready to fly a Cessna 180. One slight old guy was "pulling the prop through". A 180 is a taildragger and the spinner is about 5 or 6 feet off the ground. This guy had his arms wrapped around the prop in such a way that if it fired, it would have cut him in half and flung the parts across the ramp. Should I have said anything? Lefty __________________________________________________________________________ ______ To unsubscribe from this list please send mail to [EMAIL PROTECTED] _____________________________________________________________ Keep up with breaking news! Join our Hot Topics list. http://www.topica.com/lists/breakingnews/t/12
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