04th Nov ’03                                               



Francis Donaldson

Chief Engineer



Dear Francis,





        On the 28th of Nov ’03 I flew Ken Atkinson’s KR2 to evaluate its handling, characteristics and asses the stick free oscillation in pitch while in turbulence as requested in your letter of 13 Nov ’03.


First Flight. 28/11/03.


        The conditions at Liverpool were:


     Surface 170/10-12kts 9999 Few035 Sc055 +7/+3 1006 QNH

        2000 ft 190/20 [no turbulence] vis +20 nm OAT +2 Deg C


        The AUW was 899 lbs with a CG 9.42 ins aft of datum.


        I note your comment ‘not a one-liner’ report in your letter. I promise to do better than that but will keep it as brief as possible by not covering any ground already competently dealt with by David Scouller.  [The PFA test pilot]


1                  Aircraft flown at VNE at 2500 ft Altitude in smooth air for 2 mins and experienced no buffet at all.


2                  Configuration: Aircraft in trim 110 kts/2900 rpm. Six separate times the nose was lowered to an estimated 10 to 15 degrees and stick free the following average result was obtained:


Speed increased to 130 kts then slowly fell back to 89 kts returning to stable flight at 110 kts after only one cycle.

The time for the cycle was 45 seconds.

This seems reasonable to me and compares well with my Kr2 at a similar CG position.




3          The stick free oscillation. In order to experience some in-flight turbulence I descended to 1000 ft down wind of the Peckforton hills and experienced stick free oscillation in pitch as described by David Scouller.

I did not examine the magnitude of this for David has already done that but concentrated on controlling the aircraft in pitch.

I found it quite easy but was aware of an intermittent gentle elevator buffet through the stick while in turbulence.


    I also noticed that while climbing in still air an occasional similar gentle elevator buffet was transmitted to the stick. This became apparent especially if the aircraft was gently rocked fore and aft in pitch. 



The Solution.


        Suspicion fell on the cockpit canopy lifting handles. 


     On the lower frame of the cockpit canopy, on both sides at the back, thin flaps of metal parallel to the top longerons were attached to lift open the canopy.  These flaps/handles were about 1 3/4" long and protrude nearly 1" into the airflow directly in line with the tail plane in normal flight. 

If there was any angle of attack on these flaps they could act like vortex generators.  In steady climb it is likely that any such vortex would miss the tail plane because of the angle of attack/pitch of the aircraft but might strike the tail plane if the nose was lowered slightly.

In normal smooth air cruise there was no buffet presumably because these canopy flaps were at 0 degrees incidence but in turbulence any modification of the airflow over them would come off as a vortex and possibly go straight back over the tail plane causing the buffet.


Only one way to find out!


        The canopy lifting handles were removed and a farther air test was arranged.


Second Flight. 04/12/03


The conditions at Liverpool were:


        Surface 040/07 6K B/18 +9/+4 1033 QNH


        2000 ft 050/30 +5


        The AUW was 875 lbs with a CG of 9.73 ins aft of datum.



        This flight was conducted in its entirety without any elevator buffet or stick free oscillation being experienced in the climb or at any speed while in turbulence.


      My general impression of G-BVIA is of a well built thoughtfully constructed aircraft in all departments. The cockpit is comfortable, sensibly arranged and the whole ‘package’ instilled confidence in the pilot. Its handling is as good as any KR2 I have flown and better than most. I noted particularly how docile it was to land in a quite brisk crosswind on the first flight on 28/11/03.


      I believe Ken will experience no difficulty and will enjoy flying G-BVIA.


                Yours sincerely,


                           Willie Wilson.



One of the [red] canopy handles.