We soon noted that our aircraft was not performing as well as it should be in terms of power setting versus airspeed. We started to take some performance data for comparison with the POH. The most daming evidence came in two parts; firstly as the graph below shows our aircraft was increasingly diverging (pink line) from the POH values (Blue line) as airspeed increased. This suggestive that a drag issue was involved. The second piece of evidence was found at high altitude. At 10,000 feet a considerable nose down trim was requied to keep the aircraft level. (see photos)

 

Trim tab wheel setting at 10,000 ft for level flight

 

 Position of trim tab as it would have been at 10,000ft for level flight

 

 As a result of the above finding the aircraft will have its mainplane angle of attack adjusted at next maintenance check.