I was doing a practice exam (Not BT one) and it asked in what stroke does ignition happen. My answer was the Compression Stroke due to ignition happening just before TDC. Apparently that was wrong and the answer was the Power Stroke.
Just looking for some understanding of this as I know it all happens very quickly ?
It's all about timing the spark so that the combustion produces the maximum force on the piston at the point where the connecting rod is at right angles to the crankshaft throw (maximum torque). Because the charge takes a finite time to burn, the spark must occur before that point. The spark on most aircraft engines occurs just before TDC on the compression stroke to achieve maximum torque at the right point on the power stroke.
See General Knowledge Study Guide, Ignition timing Page 6.
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Thanks Bob....appreciate the reply.
