The Burnelli Web Site
Evidence of Suppression and Official denial is overwhelming
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Reprinted from - Flight Magazine and the Aircraft Engineer, December 1935, London, England

Experimental Verification

Since all of the above hinges greatly upon the assumptions made, the writer made extensive studies of available experimental data in Mr. Burnelli's files and in every instance found confirmation of the possibility of simple superimposition of body and wing effects since the relative position of the zero lift line, slope of the lift curve and L-max always check very well. It was decided to attempt to break down the experimental lift and drag curves from the latest test of a Burnelli monoplane as given in the New York University Report No. 715.

The general procedure outlined above was followed to obtain the combined effect of aerofoil body and wing, and it was noted that the zero lift point of the body was shifted considerably in the range of positive angles of the wing. Upon completion of the analysis, which showed remarkably close agreement with experimental data, as can be seen from Fig. 3, it was decided that a better co-ordination could be obtained by approaching closer the two zero lift point. This was confirmed by the study, the results of which are given in Fig. 4. It was further observed by an approximate stability calculation that this arrangement would further lead to an improvement in the condition of downwash with a consequently better stability. To prove definitely all these findings it was decided to design a new body form which would fulfill all the desired conditions and locate the wing in such a way as to approach the two zero lift points as close as it was feasible without extensive changes in the wind tunnel model.

The body was made 33 per cent thicker, since the investigation indicated that this increase could be well afforded because of better co-ordination. Fig. 4 shows the remarkably close agreement of the wind tunnel test (New York University Wind Tunnel Report No. 715B) and the predicted characteristics. The zero lift point checks extremely well while being different from the former zero lift point by 2.5 degrees. The slopes of the lift curves are in very close agreement. From all these investigations, confirmed by experimental verification, it is evident that the simplified analysis gives sufficient practical accuracy. It further proves that interference effect for the case of Burnelli design is negligible, that with properly coordinated aerofoil body and wing location the fuselage carries a considerable percentage of lift constant through the whole flying range and easily determinable. Structural significance of this fact is apparent since the weight of the body now becomes useful weight contributory to the lift somewhat in the same sense in which we regard the drag of wings as compared to the parasite drag.

The weight of the wings is reduced partly because of the smaller area required and partly because of smaller wing root bending moments.

The points of safety, accessibility and volume were not touched upon but they cannot be disputed.

In conclusion it can be definitely stated that for the same aerodynamic efficiency the Burnelli type of design results in considerable saving of weight and for equal weight gives higher aerodynamic efficiency.

Watter Article part 1

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