302 AIRCRAFT ENGINEERING November, 1936 A n Account of Experiments Made i n 1932 on th e Rudlick i Oblique Empennage By A . V. Stephens , M.A., A.F.R.Ae.S. REFERENCES TO LITERATURE. T may b e recollected that a description of cinema camera and analysed by measuring an ingenious simplification of the con (1) " The Rudlicki Vee Tail." AIKCRAFT ENGINEERING, Vol. IV, th e inclination of wings and body to the I March, 1932, pp. 63-64. ventional aeroplane tail unit, in which the horizontal on selected cinema pictures. A time (2) "Measured Spins of Aeroplane 11." Gates. April, 1931 vertical and horizontal surfaces were replaced scale on th e cinema film was provide d by a n R. & XI. 1403. by a pair of surfaces arranged in th e form of a electrically operated tuning fork so tha t the (3) " Spinning of Single Scaler Fighter with Deepened Body vee, appeared in AIRCRAFT ENGINEERING in and Raised Tail Plane." Irving, liaison and Stephens. Dec. 1931. rate of rotatio n of th e model could be deduced. R. & M. 1421. March, 19321. At th e same time the suggestion The rate of descent of the model relative (4) " l'"rec Flight Spinning Experiments with Several Models." was pu t forward that this arrangement might t o the air was obtained from the wind speed Stephens. April, 1931. R. & M. 1404. prove an effective cure for dangerous spinning of the tunnel . For th e tests in which it wa s qualities. This suggestion followed naturally desired to study recoveries from a spin the from th e discovery tha t the vertical tail surfaces controls were fully reversed as described above of conventional aeroplanes became extremely after the model had been spinning steadily for ineffective under flat-spinning conditions, owing about 20 seconds. The time which elapsed Rathe r more than four years ago ther e t o shielding b y th e tai l plane. There was also between the control movement and th e instan t wa s published in AIRCRAFT EN evidence that the addition of a small positive when the model stopped spinning was taken GINEERIN G the first description of a dihedral to the tailplane had in some cases by stop-watch. In these experiments the given improved control in spins. In order to novel type of tail, described by it s in controls were reversed suddenly. Subsequent test the theory that the main value of M. tests showed that if the rudder and elevators ventor as an oblique empennage, to Rudlicki's invention might lie in it s effect upon were moved over smoothly the time of recovery which we gave the nam e " Th e Rudlicki th e dangerous spin, the writer carried out a of the standard model was roughly doubled ; Vee Tail. " For i t wer e claimed advan few experiments in th e Free Spinning Tunnel bu t this should not affect the comparative a t the Roya l Aircraft Establishment. tages i n resistance , weigh t and improved significance of th e results obtained. field of fire to the rear . In a leading article we hazarded the suggestio n that Pla n of the Tests Th e Results Tabulated it might also have valuable qualities as During 1931 a number of spinning experi I n presenting the results it is convenient t o a n anti-spinning device. This sug ments (both model and full scale) had been convert all quantities to full scale ; this has carried out on a single-seater fighter, which in gestion aroused interest a t th e tim e and been done on the assumption of dynamical its original form had proved to have an ex we understoo d tha t official investigations similarity between model and aeroplane. tremely dangerous flat spin.2 This was remedied were to be mad e to test its soundness. b y raising the tailplane vertically to a position Rudlick i tail Rudlick i tail Only recently we learnt tha t in fact these near the top of the rudder and slightly in wit h 24 deg . wit h 45 deg. Standar d experiment s were mad e a t Farnborough , dihedra l dihedra l mode l creasing the fin area. 3, 4. The test s on th e Rudlicki tail were done on a scale model of bu t for some reason the results were Incidenc e in spin 74 deg. 72 deg. 69 deg. th e same aeroplane. Rat e of turn 7·4 rad/sec. 6· 5 rad/sec. 6·5 rad/sec. never published. They did no t suppor t Rat e of descen t '. . 77 ft./sec. 85 ft./sec. 81 ft./sec. Two arrangements of th e vee tail were tested. th e view we pu t forward and the vee Sideslip angle 5 deg. 10 deg. 10 deg. I n both of these the projection s of th e oblique Tim e of recover y with full tail appears not to have the qualities opposit e controls 10·5 sec. 4·7 sec. 8·2 sec. surfaces on th e horizontal plane were made i n spin that seemed possible. In spite equal in area to th e tailplane of the original of the laps e of tim e we got int o touch design, so that the same pitching moment The tests showed that the oblique tail was characteristics and elevator control would be wit h Mr. Stephens, who carried out the less effective than a bad example of th e con maintained. But in one case the sum of th e experiments , and he ha s kindl y written ventional type with corresponding projected projections of the inclined surfaces on th e areas in tha t the steady spin was even faster and thi s account of them for publication vertical plane was equal t o th e original fin an d flatter, and recovery from it with full opposite here , as we feel that some readers ma y rudder area, whereas in th e other it was 130 per controls definitely slower. Even with a Vee still be intereste d in having the matte r cent greater. The dihedra l angles of th e two tail of exaggerated form, which involved an tail units were 24 deg. and 45 deg. respectively. cleared up even after this long interval increase in effective fin area of 130 pe r cent over The equivalent vertical and horizontal areas th e original design, the flat spin was still converted to full scale were as given in th e possible although recovery was more satis following schedule. factory. It was concluded that the Vee tail had little merit as a n anti-spinning device. Rudlick i tail Rudlick i tail down 40 deg. without moving the starboard I n order t o avoid misunderstanding it should wit h 24 deg. wit h 45 deg. Standar d one. A simple delayed-action mechanism wa s dihedra l dihedra l tai l be stated tha t the experiments described above Tota l area .. .. 30·6 sq. ft . 40·4 sq. ft. 40·4 sq. ft . incorporated in th e model and arranged t o move were done four years ago, when the technique Effective fin and rudder th e flap on one side from —40 deg. t o +4 0 deg. are a .. .. 12·4 „ 28·6 „ 12·4 „ of the Free Spinning Tunnel was only partially Effective tailplane and a t a predetermined instant, thus simulating the developed. More searching and conclusive elevato r area . . .. 28·0 ,, 28·6 „ 28·0 ,, action of a pilot reversing both rudder and tests were subsequently devised and it is elevator for recovery from a spin. The two tail possible that if the Vee tail had been tested The oblique planes of th e tw o Rudlick i tails units were loaded to maintain the same centre a t a later date and under more varied con were of th e same plan form as th e original tail- of gravity position as the standard model, ditions it would have appeared in a more plane, the ratio of the flap to fixed portion without appreciably changing the moments of favourable light. But it seems very unlikely being unaltered. Maximum control angles were inertia. tha t under any conditions it would prove take n as ±2 0 deg. for flaps functioning either superior, as regards spinning, to an ordinary as rudders or as elevators ; as rudders they Spinning Tests tail unit with the bulk of the fin and rudder would be applied differentially and as elevators situated below the tailplane. the y would be moved up or down together. The model with its three different tail units Full right rudder and stick back would accord was tested in th e Free Spinning Tunnel accord The writer is indebted to the Director of ingly move the port flap up 40 deg., leaving ing to a procedure which has often been de Scientific Research at the Air Ministry for th e starboard one neutral: similarly reversing scribed. Continuous spins with the controls permission to make use of hithert o unpublished th e controls fully would move the port flap locked were photographed with a high speed material in th e preparatio n of this article.
Aircraft Engineering and Aerospace Technology – Emerald Publishing
Published: Nov 1, 1936