Takeoff and landing platform for V/STOL airplane

A takeoff and landing platform for V/STOL aircraft has features to reduce ground effect. The platform has a plurality of vanes mounted above a flat horizontal surface. Each of the vanes is curved to turn the jet stream from the vertical. The upper edges of all the vanes lie in a plane that is parallel with the horizontal surface. This plane is located at a distance from the horizontal surface that is about 0.5 to about 2.0 times the engine nozzle diameter at takeoff and landing of the type aircraft that use the platform.

BACKGROUND OF THE INVENTION 
This invention relates in general to takeoff and landing platforms for 
V/STOL airplanes, for reducing undesirable ground effect. 
Vertical and short takeoff and landing airplanes are known as "V/STOL" 
airplanes. Normally, a V/STOL airplane has jet engines with nozzles that 
will deflect downwardly for takeoff and landing. A V/STOL airplane 
experiences undesirable ground effect during the takeoff and landing. The 
hot high velocity jet exhaust gas streams striking the landing surface 
create a suckdown force, reducing lift. Another effect, known as 
"fountain", results in an upward force on the aircraft. The fountain can 
be disadvantageous, also, since the positioning of the fountain is 
difficult to control. Also, the hot, upwardly deflected gasses if ingested 
by the engine inlet(s) will reduce the efficiency of the engine(s). 
Consequently, it is normally desirable to minimize such ground effects. 
Some prior art proposals employ blades or vanes in a platform mounted above 
the underlying horizontal surface or ground plane and positioned to 
intercept exhaust gases from the engine and turn them so they are 
discharged away from the plane. e.g., laterally. Some of these proposals 
are complex, requiring spring loaded check valves or locating the vanes 
higher than desired above the ground plane, e.g., for shipboard use. 
Others utilize relatively small platforms, one for each jet stream or have 
constructions requiring rather precise positioning of the aircraft with 
respect to the blades during takeoff and landing to properly direct the 
engine exhaust. 
SUMMARY OF THE INVENTION 
The apparatus of this invention consists of a single platform large enough 
to physically support a V/STOL airplane on its upper surface. The platform 
has a plurality of vanes of substantially uniform height adapted to be 
mounted in unobstructed relation above a flat horizontal surface. Each 
vane is curved to turn the jet from the vertical direction, causing the 
jet to sweep laterally outward beneath the vanes and above the flat 
surface. The top edges of the vanes all lie in a single plane that is 
parallel with the horizontal surface and located at a distance from the 
horizontal surface that is about 0.5 to about 2.0 times the engine nozzle 
diameter at takeoff and landing. Preferably this distance will be from 
about 0.5 to about 1.4 engine nozzle diameters with excellent results 
having been found when this distance is from about 0.5 to about 0.86 
nozzle diameters. With this device, the ground effects are reduced to near 
zero. Also, the construction provides a low height installation above a 
horizontal base or gound plane (e.g. a deck) that permits the desired 
directional movement of the exhaust away from the airplane during takeoff 
and landing of a V/STOL airplane in any airplane azimuth orientation 
relative to the apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1, a V/STOL aircraft 11 is schematically shown in a 
takeoff or landing position. The aircraft has two turbine engine nozzles 
13, one on each wing. Each engine nozzle 13 will move vertically to direct 
propulsive jet streams 15 from a horizontal position for horizontal flight 
to a downwardly or vertical position for takeoff and landing. 
The apparatus for reducing ground effect includes a platform 17. Platform 
17 is mounted on columns or legs 19 that are fixed to a concrete pad 21 or 
a metal deck of a ship, forming a fixed ground plane. To reduce the 
detrimental effects of heat on the concrete pad 21, a steel plate 23 is 
located on top. Steel plate 23 is coextensive with platform 17 and is 
located in a horizontal plane. 
Referring to FIG. 3, the front and back walls of the platform 17 comprise 
beams 25 that extend the width of the platform 17. The front wall 25 is 
not shown in FIGS. 1 and 2 in order to better illustrate the structure of 
platform 17. A plurality of vanes 27 are rigidly and stationarily mounted 
to and between the walls 25 in unobstructed relation above the flat 
horizontal surface 23. Vanes 27 are perpendicular to walls 25 and extend 
the full length of platform 17, over the full width thereof. 
Each vane 27 is identical and curved when viewed in vertical cross-section 
as shown in FIG. 2. Each vane has an upper edge 27a and a lower edge 27b. 
Edges 27a and 27b are straight and parallel with each other. All of the 
upper edges 27a lie in a single plane that is parallel with the horizontal 
plane of steel plate 23. Similarly, all of the lower edges 27b lie in a 
single plane that is parallel to and above the horizontal plane of plate 
23. All of the upper edges 27a are located at a selected distance above 
plate 23. 
This distance has been found to be highly efficient when between about 0.5 
and about 0.86 times the diameter of the engine nozzle 13 of the aircraft 
11 for which the platform 17 is designed. The distance could be greater 
than 0.86 times the engine nozzle 13 diameter such as 1.4 times, and it is 
feasible for the height to be at least 2.0 times the nozzle 13 diameter. 
For example, if the engine nozzle diameter is 18 inches, then the distance 
from upper edge 27a to plate 23 would be between 9 inches and 151/2 
inches, using the range of 0.5 to 0.86. Some engine nozzles 13 vary in 
diameter depending on flight position. For computing the distance to the 
top of vanes 27, the diameter at the takeoff and landing should be used. 
The term "nozzle" as used herein means the point at which the jet stream 
leaves a chamber with greater than atmospheric total pressure and enters 
the atmosphere. In some aircraft, the outlet for a single engine is 
divided by vanes, thus could be considered a series of nozzles that 
combine to create a single jet stream. If the outlet is circular, the 
total diameter across the outlet should be considered the nozzle diameter. 
The outlet might also be square or rectangular. If so, the smaller total 
distance across the outlet should be considered the nozzle diameter. The 
smaller distance in a rectangular nozzle is normally the longitudinal 
distance, measured along the length of the aircraft, when the nozzle is 
turned downward. 
The spacing between vanes 27 is also important so as to turn the jet 
streams 15 efficiently. At least three of the vanes 27 should intersect 
the jet stream 15. Consequently, the distance between any two of the vanes 
27 should be less than about one half the diameter of engine nozzle 13. 
For an 18 inch engine nozzle, a distance between vanes 27 of about 6 to 9 
inches would be suitable. However, the distances between all of the vanes 
27 are equal. 
Vanes 27 have a uniform cross-sectional thickness, resulting in curved, 
preferably arcuate, parallel surfaces on both sides of each vane. This 
results in a concave configuration when viewed in vertical cross-section, 
as shown in FIGS. 2 and 3. Excellent results are obtained when the vane 27 
curvature is the arc of a circle. The radius at which the vanes 27 are 
formed should be sufficient to turn the jet streams 15 so that the streams 
strike the steel plate 23 at a low angle, preferably tangential. However, 
the curvature should not be so great so as to drastically reduce the 
distance between the vanes 27 at their lower edges 27b. 
For efficiency in manufacturing and also for the proper turning angle, a 
height defined by about a 50 to about 70 degree arc, has been found to be 
suitable for vanes 27. Excellent results have been obtained using a 
60.degree. arc. A radius that is less than the distance from upper edge 
27a to plate 23 is preferred. Approximately the distance between vanes 27 
is suitable as a radius, such as 6-9 inches as in the above-described 
example. The centerpoint 29 of the arc is selected so that the upper 
portion of each vane 27 will be tangent to a vertical plane. To accomplish 
this, centerpoint 29 should be about in the same horizontal plane as the 
upper edges 27b of the vanes. A radius R taken about centerpoint 29 for 60 
degrees will result in a total vane 27 height that is about one half the 
distance from plate 23 to the upper edge 27a. Centerpoint 29 for a 
particular vane 27 will be located between the next two adjacent vanes. 
With these parameters, the cross-sectional width of the jet stream 15, 
measured normal to the stream 15 as it discharges below two vanes 27, will 
be about 60% (percent) of the width between the two vanes at the top. 
Because of the far greater length of the vanes 27 than the nozzle 13 
diameter, no appreciable restriction will occur. 
In the preferred embodiment, all of the vanes 27 are mounted parallel with 
each other, but with half of the vanes having their concave sides facing 
toward the right, as shown in FIG. 1. The other half of the vanes 27 have 
their concave sides facing in the opposite direction, to the left as shown 
in FIG. 1. Where it is desired that all the engine exhaust be directed in 
a single direction, all of the vanes advantageously will be faced in the 
same direction. 
Referring to FIGS. 2 and 3, a grid 31 is mounted on top of the vanes 27. 
Grid 31 is comprised of lateral members 33 that are perpendicular to vanes 
26 and intersect members 35 at right angles. The longitudinal and lateral 
members 35 and 33 are flat strips oriented vertically, defining square 
apertures 37 for the passage of the jet streams 15. There are several 
longitudinal members 35 spaced parallel with and between each pair of 
vanes 27. The porosity, that is the ratio of the cross-sectional area of 
the total apertures 37 to the total grid surface area, should be greater 
than about 40%. In the preferred embodiment, there are at least five 
longitudinal members 35 between each two vanes 27. Apertures 37 are 
preferably square. The longitudinal and lateral members 35 and 33 
preferably have serrated upper edges, as shown in FIG. 2, to provide a 
good gripping surface for personnel walking on the platform 17. 
The platform 17 will be normally permanently mounted to a ship or to a 
concrete pad 21. Spaces exist between legs 19 on the two sides for 
discharging jet streams 15, so as substantially to prevent or to minimize 
engine injestion of exhaust gasses, and suckdown and fountain effects. 
The platform length in the direction that the vanes 27 extend will be 
probably about 50% greater than its width. The width is greater than the 
distance between the outer edges of nozzles 13. A typical platform 17 
would be about 30 feet wide and 50 feet long, or large enough to 
physically support an airplane on its upper surface, and intercept all of 
the downward flowing jets 15 when the airplane is in the landed position. 
For this size, the vanes advantageously are in the area of about 5 to 
above 7 inches in height, with their upper edges spaced above the ground 
plane about 9 to about 16 inches. 
In operation, when taking off or landing, jet streams 15 are directed 
vertically downward. The streams 15 flow undeflected through the apertures 
37 of grid 31, then are turned horizontally by the vanes 27 and underlying 
horizontal surface 23 to flow unobstructedly out the sides of platform 17. 
The flow exits the sides transverse to the lengths of the vanes 27. 
Normally, one stream 15 will discharge through the vanes 27 facing one 
side and the other stream 15 through the vanes 27 facing the opposite 
side. When the aircraft 11 contacts platform 17, the grid 31 supports the 
aircraft and provides an area for personnel to reach the aircraft. 
The invention has significant advantages. Lift loss due to suckdown forces 
is held to a low percentage. Fountain is held to near zero. This minimizes 
the ground effects on the V/STOL aircraft for more efficient and safer 
takeoff and landing. The apparatus is simple in construction, having no 
moving parts. The large surface area of the platform reduces the 
requirements for precise maneuvering for landings. The positioning of the 
vanes and their curvature allows a low platform with a relatively light 
weight and size. 
While the invention has been shown in only one of its forms, it should be 
apparent to those skilled in the art that it is not so limited but is 
susceptible to various changes and modifications without departing from 
the spirit of the invention.