You are not far out. The P38 is indeed the Lightning with twin booms and a Rudder directly behind each engine.
In normal flight there will be no asymetric blade effect (P factor) and the slipstram effect on each rudder will balance out. If you lose an engine, the yaw caused by engine loss and the introduction of asymetric blade effect at a high angle of attack will be oposed by the slipstream effect on the rudder behind the live ingine. If the engines rotated the other way, the slipstream effect would add to and increase the yaw.
The title refers to critical engine. There is no critical engine in this case.
[ 04 January 2002: Message edited by: Noggin ]</p>