I have had an email asking me to comment on this situation on RCU. I don't have a Kingcat but I do have two Bobcats, similar configuration, but with only slightly angled engines. I do think the engine angle on the Kingcat looks excessive, greater than anything I have seen before. That said, the DH Vampire of similar configuration, had a noticeably angled engine, too, but the DH110, Sea Vixen, did not but the tailplane WAS higher up the fins.

My theory is that the jet efflux accelerates the airflow over the stab. particularly the bottom surface and lowers the pressure, thus increasing the download produced by the tailplane causing a pitchup. If that is the case there are probably three fixes:

1. Raise the tailplane towards the top of the fins.
2. Reduce the camber of the tailplane, paricularly on the lower surface. (but this may have undesirable effects at other speeds and power settings.)
3. Do what was done and adjust the engine thrustline to cause a nose down pitch to balance the noseup pitch produced by the tailplane, the simplest solution.

Regards,

David Gladwin.