Anti-flip deflector strut for amphibious aircraft

Abstract

Disclosed are various embodiments for reducing or eliminating the nose-down pitching moment during water landings of amphibious aircraft when the landing gear is in the down position. Shielding struts forward of the wheels generate hydrodynamic lift and reduce hydrodynamic drag in order to alter the pitching moment about the aircraft center of mass.

Claims

1. A deflector strut system on an amphibious aircraft to reduce or to eliminate nose-down pitching moment during wheels-down water landings, the deflector strut system comprising: a deployable nose gear having a nose wheel, the nose gear being deployable into a down position; and a deflector strut positioned forward of the nose wheel when the nose gear is in the down position, wherein the deflector strut is configured to be narrower in the spanwise direction that the nose wheel.

2. The system of claim 1 wherein the deflector strut is configured as a wedge shape.

3. The system of claim 1 wherein the deflector strut has a non-constant spanwise width.

4. The system of claim 1 wherein the deflector strut has a concave upstream surface.

5. The system of claim 1 wherein the perpendicular bisector to the deflector strut from its centroid is a line that extends substantially through the center of mass of the aircraft.

6. The system of claim 1 wherein the perpendicular bisector of the deflector strut from its centroid is a line that extends in front of the center of mass of the aircraft.

7. The system of claim 1 wherein the deflector strut is curved.

8. The system of claim 1 wherein the lower extremity of the deflector strut consists of a replaceable segment.

9. The system of claim 1 wherein the top of the deployed deflector strut is forward of the bottom of the deployed deflector strut.

10. The system of claim 1 wherein the deflector strut is deployed in the down position by means of mechanical connection to the nose gear.

11. A deflector strut system on an amphibious aircraft to reduce or to eliminate nose-down pitching moment during wheels-down water landings, the deflector strut system comprising: a deployable main gear having a main wheel, the main gear being deployable into a down position; and a deflector strut positioned forward of the main wheel when the main gear is in the down position, wherein the deflector strut is configured to be narrower in the spanwise direction that the main wheel.

12. The system of claim 11 wherein the deflector strut is configured as a wedge shape.

13. The system of claim 11 wherein the top of the deflector strut is forward of the bottom of the strut.

14. The system of claim 11 wherein the deflector strut is mechanically connected to the main gear.

Description

DESCRIPTION OF THE DRAWINGS

(1) In FIG. 1, a conventional amphibious aircraft 1 with floats 2 lands on the water surface 3 with the nose wheels 4 and main wheels 5 mistakenly in the down position. Force vector 6 is generated on the nose wheel support structure 7, and force vector 8 is generated on the main wheels, resulting in a large nose-down pitching moment 9 about the aircraft center of mass 10.

(2) In FIG. 2, deflector struts 11 have been incorporated into the support structure forward of nose wheels 4 and support structure 7 to generate force vector 12, along a line 13 that is oriented forward of the aircraft center of mass 10, resulting in a nose-up pitching moment 14. Deflector struts 15 have been incorporated forward of the main wheels 5 to generate force vector 16, along a line 17.

(3) In FIG. 3, deflector strut 11 is mounted forward of nose wheel 4 and its support structure 7.

(4) In FIG. 4, illustrates a concave geometry of the upstream surface 19 of a deflector strut 20, positioned upstream of nose wheel 4 in a horizontal cross section below the wheel axle.

(5) In FIG. 5, a horizontal cross section below the wheel axle illustrates a wedge geometry of the upstream side 21 of a deflector strut 22, with half angle 23, positioned upstream a distance 24 forward of nosewheel 4 of width 25.

REFERENCES

(6) Chapman, R. B. 1971 Spray Drag of Surface-Piercing Struts, TP251, Naval Undersea Research and Development Center, September. Hoerner, S. F. 1965 Fluid-Dynamic Drag, self-published. Kiceniuk, T. 1954 A Preliminary Experimental Study of Vertical Hydrofoils of Low Aspect Ratio Piercing a Water Surface, Report No. E-55.2, Hydrodynamics Laboratory California Institute of Technology, Pasadena, CA. Tulin, M. P. 1957 David W. Taylor Model Basin, Washington DC, USA, Department of the Navy, Published in: Schiffstechnik, Band 4, Heft 21. von Karman, T. 1929 The Impact on Seaplane Floats during Landing, National Advisory Committee for Aeronautics, 321 309-313. Wagner, H. 1933 ber das Gleiten von Wasserfahrzeugen, Jahrbuch der Schiffbautechnik, 34. Also published in English as NACA TM 1139. Washington, April 1948. Wu, T. Y-T. 1972 Cavity and wake flows, Annual Reviews of Fluid Mechanics, 4, 243-284.