Modifications to jet aircraft having aft fuselage-mounted nacelles overlapping the wing assemblies

A Gates Learjet aircraft of the 23, 24, 25, 28 or 29 model type having aft fuselage mounted engine nacelles partially overlapping trail edge portions of the aircraft's wings, comprising:

• a channel defined by said aircraft fuselage, trailing edge portions of said wings, pylon assemblies extending between said fuselage and said nacelles, portion of the outer surface of said nacelle and an imaginary plane extending from a lowermost surface of said nacelle into perpendicular contact with said trailing wing portion;
• channel means having an area ratio of cross-sectional area at the channel exit to the minimum cross-sectional area at a position within said channel, said area ratio being less than or equal to 1:1.065 for preventing the formation of shock waves in said channel during transonic flight of said jet aircraft.

A method for modifying a jet aircraft of the type having aft fuselage-mounted engine nacelles partially overlapping trailing edge portions of the aircraft's wings, said jet aircraft being of the type which normally cruises in the transonic regime and including a channel for air formed on each side of the aircraft defined by the upper wing surface extending to its said trailing edge portion, the aircraft fuselage, a pylon support assembly extending between said fuselage and said nacelle, a surface of said nacelle overlapping said wing, and an imaginary plane of symmetry extending from a lowermost outer surface of said nacelle into perpendicular contact with said wing, the improvement which comprises:

• contouring the surfaces defining said channel so as to decrease the ratio of the cross-sectional area at the exit end of said channel to the minimum cross-sectional area of the channel as compared to the ratio of at least 1.0:1.11 for said same areas in the original unmodified aircraft,
• said ratio being decreased to a value such that the air passing through said channel at transonic cruising speeds of the aircraft maintains a velocity over substantially the entire length of the channel which is subsonic.

A method for modifying a jet aircraft of the type having aft fuselage-mounted engine nacelles partially overlapping trailing edge portions of the aircraft's wings, said jet aircraft being of the type which normally criuses in the transonic regime and including a channel for air formed on each side of the aircraft defined by the upper wing surface extending to its said trailing edge portion, the aircraft fuselage, a pylon support assembly extending between said fuselage and said nacelle, a surface of said nacelle overlapping said wing, and an imaginary plane of symmetry extending from a lower-most outer surface of said nacelle into perpendicular contact with said wing, the improvement which comprises:

• contouring the surfaces defining said channel so as to decrease the ratio of the cross-sectional area at the exit end of said channel to the minimum cross-sectional area of the channel as compared to the ratio of at least 1.0:1.11 for said same areas in the original unmodified aircraft,
• said decrease in said ratio being accomplished by both increasing said minimum cross-sectional area and decreasing said area at the channel exit;
• said ratio being decreased to a value such that the air passing through said channel at transonic cruising speeds of the aircraft maintains a velocity over substantially the entire length of the channel which is subsonic.

In a jet aircraft of the type having aft fuselage mounted engine nacelles partially overlapping trailing edge portions of the aircraft's wings, said jet aircraft being of the type which normally cruises in the transonic regime and including a channel for air formed on each side of the aircraft defined by the upper wing surface extending to its said trailing edge portion, the aircraft fuselage, a pylon support assembly extending between said fuselage, and said nacelle, a surface of said nacelle overlapping said wing, and an imaginary plane of symmetry extending from a lower-most outer surface of said nacelle into perpendicular contact with said wing, the improvement which comprises:

• the surfaces defining said channel being contoured so as to decrease the ratio of the cross-sectional area at the exit end of said channel to the minimum cross-sectional area of the channel as compared to the ratio of at least 1.0:1.11 for said same areas in an unmodified aircraft of similar configuration,
• said ratio being decreased to a value such that the air passing through said channel at transonic cruising speeds of the aircraft maintains a velocity over substantially the entire length of the channel which is subsonic.

In a jet aircraft of the type having aft fuselage-mounted engine nacelles partially overlapping trailing edge portions of the aircraft's wings, said jet aircraft being of the type which cruises in the transonic regime and including a channel for air formed on each side of the aircraft defined by the upper wing surface extending to its said trailing edge portion, the aircraft fuselage, a pylon support assembly extending between said fuselage and said nacelle, a surface of said nacelle overlapping said wing, and an imaginary plane of symmetry extending from a lower-most outer surface of said nacelle into perpendicular contact with said wing, the improvement which comprises:

• the surfaces defining said channel being contoured so as to decrease the ratio of the cross-sectional area at the exit end of said channel to the minimum cross-sectional area of the channel as compared to the ratio of at least 1.0:1.11 for said same areas in an unmodified aircraft of similar configuration,
• said decrease in said ratio including an increase in said minimum cross-sectional area of said channel and a decrease in said area at the channel exit,
• said ratio being decreased to a value such that the air passing through said channel at transonic cruising speeds of the aircraft maintains a velocity over substantially the entire length of the channel which is subsonic.

In a jet aircraft of the type having aft fuselage mounted engine nacelles partially overlapping trailing edge portions of the aircraft's wings, said jet aircraft being of the type which cruises in the transonic regime, the improvement comprising modifications to said aircraft in which:

• a glove assembly is attached to the inboard portion of each wing, each glove assembly including upper and lower smoothly contoured surfaces which join the respective existing upper and lower wing surfaces, with each glove having a bluntly shaped leading edge enclosing a portion of the original leading edge area of the respective wing;
• and
• means for smoothly decelerating the air flow speed over each wing aft of the location of maximum negative pressure coefficient in the vicinity of a forward portion of said wing, said means comprising a part of the upper wing surface and said glove assembly jointly forming a portion of concave configuration streamwise at a location substantially opposite the leading portion of the engine nacelle, said means further comprising a portion of increased convexity streamwise forward of said concave portion as compared to the unmodified aircraft, said means acting to maintain a negative coefficient of pressure over the entire inboard portion of said wing at transonic cruising speeds.