R1066 wrote:
I thought during a head on shot tail hits were applied to engine?
Yes, that's right... unless you are talking about 2-seaters!
In fact, the "directional hits" rule never applies to observer's fire (it is considered that his plane is flying at a different altitude, so that he doesn't need perfect lining to aim and fire).

That's correct, sort of. Observer fire straight out of the tail (6 o'clock) into a plane straight into either engine or tail(1 or 6 o'clock) will give the converted hits. Any of the fire from the firing arc will desregard the directional hits regardless of the plane it is shooting at.