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Many thanks to Al Bowers for this document! Copy of letter from Dear Mr. Burtton: You will have received my cable of May 11th as follows:- "Horten flight tested great success May 7th - stop - will advise shipping date" and naturally you will wish to have more ample information as to what has been happening over here with the Horten IV glider and I feel I'm probably the best person to supply this information. The aircraft was assembled at the College of Aeronautics at Cranfield last week by Mr. H.E. Bolton of the Hawkridge Aircraft Co. Ltd., Denham. Mr. Bolton has maintained a life long interest in gliders and is one of the best engineers of its field. He gave his undivided attention to the rigging and assembly of the Horten IV and was extremely careful on the control adjustments. When the aircraft reaches you I would strongly advise that the individual adjustments are not changed, since the aircraft flies perfectly as rigged. The pilot for the occasion was Flight Lieutenant Forbes, Chief Flying Instructor at the R.A.F Glider School at Detling, Maidstone, Kent and he made two perfect flights and was completely satisfied with the aircraft. Moreover he said that was a thousand pities that it was leaving the country for America and I should think it is just about the most efficient glider in the world and one with whom new records are bound to be created. Incidentally the aircraft towed off by a Moth. In view of the highly successful flights, during the course of which sufficient observations were made to satisfy the British Glider Association, the aircraft was immediately dismantled so as to be available for the transportation company which is handling the packing and shipping for formalities. I hope to advise you a few days as to the shipping date and anticipated arrival date of arrival in Detroit. The aircraft is, of course, sensitive on the controls, since the longitudinal, lateral, and directional derivatives have very low values. Consequently, very small movements are required to maneuver the aircraft. Forbes states that it turns very nicely on aileron application only and that at the C.G. position as flown the stall is straightforward and innocuous. For information you will find the following figures useful:- Weight empty 560 pounds Weight as flown 720 pounds Gross affective projected wing area 2001 square feet Projected wing span 66.42 feet Standard mean cord length 3.03 feet distance of quarter standard mean cord point aft of datum 4.820 feet C.G. as flown 4.54* feet aft of datum = 16% S.M.C. C.G. empty 4.76* feet aft of datum = 23% S.M.C The datum referred to is the leading edge of the wing on the center line of the aircraft and such is the most forward point. The characteristic of some tailless aircraft of the C.G. is too far aft is a periodic longitudinal oscillation, which is only cured by forward movement of the center of gravity. As stated earlier this particular aircraft flies perfectly and there is no hint of such oscillation, neither would we expect it with a 16% S.M.C position of the center of gravity. I enclose some copies of photographs, taken on the occasion of the test flights, which are not very good, being purely amateur efforts. The occasion was one of very great interest to the students of the College of Aeronautics and it was indeed a very pretty piece of flying. Yours Sincerely,
(F.F. Crocombe).
*Measured normal to the wing hinge from axis.
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