Dear all,
I am so sorry to reply this late as I was very busy with my school work recently. My sincere apology.
To clarify, in my knowledge, propeller's torque is referring to a drag force while engine torque refers to rotational force generated by the engine.
I have read through all of your replies and I am very thankful for all of your comments.
Now I understand much better on these two parameters.
Basically, now I know that:
At an optimum RPM, the propeller torque is equal to the engine torque, the only difference is its direction. Say, for example, if now the engine torque is in clockwise (viewing from the cockpit), the propeller torque would be in anti-clockwise direction.
Now my questions becomes, what happen if engine torque is greater than propeller torque? I know that the RPM would then become faster, but how would this affect the efficiency of the engine? I don't quite get it. Hope someone would shed me some light on the issue.