Control linkage for T-tail aircraft elevator surfaces

A dual elevator system for an aircraft having a vertical stabilizer and a horizontal stabilizer attached to said vertical stabilizer, said dual elevator system comprising:

• a first elevator assembly, said first elevator assembly having a first elevator surface and a first elevator hinge, said first elevator hinge being rotatably attached to said horizontal stabilizer of said aircraft;
• a second elevator assembly, said second elevator assembly having a second elevator surface and a second elevator hinge, said second elevator hinge being rotatably attached to said horizontal stabilizer of said aircraft;
• and
• a modified constant velocity joint control linkage mechanism that comprises:
• a first universal joint yoke assembly having a yoke axle coupled to said first elevator hinge,
• a second universal yoke assembly having a yoke axle coupled to said second elevator hinge,
• a central cage coupled between said first universal joint yoke assembly and said second universal joint yoke assembly, and
• an input push rod assembly having a first end coupled to said central cage and a self-aligning second end coupled to a control lever, said control lever being fixedly attached to said vertical stabilizer of said aircraft.

A method for inducing synchronous motion of two adjacent controllable devices, comprising:

• providing a first rotational joint comprising two first yoke uprights with a first yoke axle disposed therebetween and a first hinge axle oriented at a right angle to said first yoke axle, said first yoke axle being coupled at a right angle to a first one of said controllable devices;
• providing a second rotational joint comprising two second yoke uprights with a second yoke axle disposed therebetween and a second hinge axle oriented at a right angle to said second yoke axle, said second yoke axle being coupled at a right angle to a second one of said controllable devices;
• providing a cross-connection coupled between said first and second hinge axles of said first and second rotational joints, said cross connection comprising a third hinge axle between said first and second hinge axles and being adjustable to produce differential motion between said first and second controllable devices;
• providing a self-aligning input push rod assembly having a first end coupled to said cross connection at said third hinge axle between said first and second hinge axles, and a second end configured for coupling to receive a single input control motion;
• and
• inducing said synchronous motion in said first and second controllable devices in response to said single input control motion received at said third hinge axle of said cross connection;
• wherein said synchronous motion is induced by providing control motion to said first controllable device through said first rotational joint, and providing control motion to said second controllable device to said second controllable device through said second rotational joint;
• and
• wherein said two adjacent controllable devices comprise dual elevator surfaces of a T-tail aircraft.

A method of installing a modified constant velocity joint control linkage mechanism in an existing dual elevator system of an aircraft having a vertical stabilizer and a horizontal stabilizer attached to said vertical stabilizer, said method comprising:

• providing an aircraft having an existing dual elevator system and original control system for same, said existing dual elevator system having a vertical stabilizer and a horizontal stabilizer attached to said vertical stabilizer;
• and
• retrofitting said aircraft by replacing one or more components of said original control system with said modified constant velocity joint control linkage mechanism in the following manner:
• providing said modified constant velocity joint control linkage mechanism that comprises:
• a first universal joint yoke assembly,
• a second universal yoke assembly,
• a central cage coupled between said first universal joint yoke assembly and said second universal joint yoke assembly, and
• an input push rod assembly having a first end coupled to said central cage and a self-aligning second end;
• attaching said first universal joint yoke assembly to a first elevator hinge of a first elevator assembly of said elevator system, said first elevator hinge being rotatably attached to said horizontal stabilizer of said aircraft;
• attaching said second universal yoke assembly to a second elevator hinge of a second elevator assembly of said elevator system, said second elevator hinge being rotatably attached to said horizontal stabilizer of said aircraft;
• and
• attaching said self-aligning second end of said input push rod to a control lever of said elevator assembly;
• wherein said first universal joint yoke assembly is configured to rotate in a single plane relative to said central cage;
• and wherein said second universal joint yoke assembly is configured to rotate in multiple planes relative to said central cage.

A method for inducing synchronous motion of two adjacent controllable devices, comprising:

• providing a first rotational joint comprising two first yoke uprights with a first yoke axle disposed therebetween and a first hinge axle oriented at a right angle to said first yoke axle, said first yoke axle being coupled at a right angle to a first one of said controllable devices;
• providing a second rotational joint comprising two second yoke uprights with a second yoke axle disposed therebetween and a second hinge axle oriented at a right angle to said second yoke axle, said second yoke axle being coupled at a right angle to a second one of said controllable devices;
• providing a cross-connection coupled between said first and second hinge axles of said first and second rotational joints, said cross connection comprising a third hinge axle between said first and second hinge axles and being adjustable to produce differential motion between said first and second controllable devices;
• providing a self-aligning input push rod assembly having a first end coupled to said cross connection at said third hinge axle between said first and second hinge axles, and a second end configured for coupling to receive a single input control motion;
• and
• inducing said synchronous motion in said first and second controllable devices in response to said single input control motion received at said third hinge axle of said cross connection;
• wherein said synchronous motion is induced by providing control motion to said first controllable device through said first rotational joint, and providing control motion to said second controllable device to said second controllable device through said second rotational joint;
• and
• wherein said first yoke axle is coupled at a right angle to a hinge line of said first one of said controllable devices;
• wherein said second yoke axle is coupled at a right angle to a hinge line of said second one of said controllable devices;
• and wherein said hinge line of said first one of said controllable devices is skewed relative to said hinge line of said second one of said controllable devices.