Three-position aircraft tail skid mechanism and method of actuation

Patent metadata

Field	Value
Publication number	US-10086930-B2
Application number	US-201514834369-A
Country	US
Kind code	B2
Filing date	Aug 24, 2015
Priority date	Aug 24, 2015
Publication date	Oct 2, 2018
Grant date	Oct 2, 2018

Abstract

A system includes an aircraft having a fuselage with a tail portion. A tail skid is disposed in an opening of the tail portion. The tail skid includes a ground contact shoe and a mechanism configured to selectably move the ground contact shoe between respective ones of a stow position disposed within the opening, a landing position disposed below the opening, and a takeoff position different than the stow and landing positions. Before a takeoff or a landing, the ground contact shoe is moved to a corresponding one of the takeoff or landing positions. In the event of an over-rotation or an over-flaring of the aircraft during a takeoff or a landing, respectively, the ground contact shoe makes contact with the ground and a shock absorber of the system absorbs a shock of the contact and thereby prevents tail strike damage to the aircraft.

First claim

What is claimed is:

1. A system, comprising:
an aircraft having a fuselage with a tail portion; and
a tail skid disposed in an opening of the tail portion, the tail skid comprising:
a ground contact shoe; and
a mechanism configured to selectably move the ground contact shoe between respective ones of a stow position disposed within the opening, a landing position disposed below the opening, and a takeoff position different than the stow and landing positions, wherein the mechanism comprises:
first and second attach pins respectively pinioned within a structure of the aircraft for rotation relative thereto;
a linkage comprising two pairs of links coupled between the first and second attach pins and defining a node at a middle of the linkage; and
an actuating device configured to selectably rotate respective ones of the first and second attach pins in such a way as to move the node between positions respectively corresponding to the stow, landing, and takeoff positions, and wherein the actuating device comprises:
first and second crank arms respectively fixed to opposite first and second ends of the first attach pin for conjoint rotation;
a third crank arm fixed to a first end of the second attach pin for conjoint rotation; and
first and second actuators, each having opposite ends, wherein
 a first end of the first actuator is coupled to an outer end of the first crank arm for relative rotation,
 a second end of the first actuator is coupled to an outer end of the third crank arm for relative rotation,
 a first end of the second actuator is coupled to an outer end of the second crank arm for relative rotation, and
 a second end of the second actuator is coupled to an end of the second attach pin opposite to the first end thereof for relative rotation.

2. The system of claim 1 , wherein the linkage comprises:
first and second vertical links, each having opposite ends, wherein
an upper end of the first vertical link is coupled to the first attach pin for conjoint rotation therewith,
an upper end of the second vertical link is coupled to a lower end of the first vertical link for rotation relative thereto; and
first and second horizontal links, each having opposite ends, wherein
a front end of the first horizontal link is coupled to the second attach pin for conjoint rotation therewith,
a front end of the second horizontal link is coupled to a rear end of the first horizontal link for rotation relative thereto, and
a rear end of the second horizontal link is coupled to a lower end of the second vertical link for rotation relative thereto at the node.

3. The system of claim 1 , further comprising a dual over-center locking mechanism for locking the ground contact shoe in each of the stow, landing and takeoff positions.

4. The system of claim 3 , wherein the dual over-center locking mechanism comprises:
a first over-center mechanism that contains a first horizontal stop feature disposed on a first horizontal link and a second horizontal stop feature disposed on a second horizontal link, the first and second horizontal stop features being configured to prevent downward movement of a hinge defined between the first and second horizontal links when the two horizontal stop features are disposed in contact with each other and past a locked position in which the hinge is disposed below a load line extending between two horizontal link attach points and to permit unlocking upward movement of the hinge relative to the locked position; and
a second over-center mechanism that contains a first vertical stop feature disposed on a first vertical link and a second vertical stop feature disposed on a second vertical link, the first and second vertical stop features being configured to prevent lateral movement aft of a hinge defined between the first and second vertical links when the two stop features are in contact with each other and past a locked position in which the hinge is disposed aft of a load line extending between the two horizontal link attach points and to permit unlocking forward movement of the hinge relative to the locked position.

5. The system of claim 3 , further comprising a mechanism for unlocking then re-locking the over-center locking mechanism when the ground contact shoe is moved from the takeoff position to the stow position, and the ground contact shoe is moved from the stow position to the landing position.

6. The system of claim 1 , wherein the mechanism further comprises:
an elongated shock absorber having opposite ends, a first end being coupled to the node for relative rotation; and
a lever arm having opposite ends, a first end being coupled to a third attach pin for relative rotation and a second end being coupled to a second end of the shock absorber for relative rotation, wherein the ground contact shoe is disposed on the second end of the lever arm.

7. The system of claim 6 , wherein the shock absorber compresses to absorb energy.

8. A method for protecting an aircraft against tail strike damage, the method comprising:
providing a tail skid disposed in an opening of a tail portion of the aircraft, the tail skid comprising an elongated shock absorber having a ground contact shoe disposed at a lower end thereof, the ground contact shoe being moveable between respective ones of a stowed position disposed within the opening, a landing position disposed below the opening, and a takeoff position disposed at a position different than the stowed and the landing positions, and a dual over-center locking mechanism operable to releasably lock the ground contact shoe in respective ones of the stowed, landing, and takeoff positions;
moving the ground contact shoe to the takeoff position before a takeoff such that, in an over-rotation of the aircraft during the takeoff, the ground contact shoe makes contact with a ground surface and the shock absorber absorbs a shock of the contact to reduce tail strike damage to the aircraft; and
releasably locking the ground contact shoe in the takeoff position with the dual over-center locking mechanism.

9. The method of claim 8 , further comprising:
moving the ground contact shoe to the landing position before a landing such that, in an over-flaring of the aircraft during the landing, the ground contact shoe makes contact with the ground surface and the shock absorber absorbs a shock of the contact to reduce tail strike damage to the aircraft; and
releasably locking the ground contact shoe in the landing position with the dual over-center locking mechanism.

10. The method of claim 8 , further comprising:
sensing whether a landing gear of the aircraft is deployed;
sensing whether the landing gear is bearing a weight of the aircraft;
moving the ground contact shoe to the stowed position if the landing gear is not deployed;
moving the ground contact shoe to the landing position if the landing gear is deployed and is not bearing the weight of the aircraft;
moving the ground contact shoe to the takeoff position if the landing gear is deployed and is bearing the weight of the aircraft; and
releasably locking the ground contact shoe in the position to which it was moved with the dual over-center locking mechanism.

11. A tail skid mechanism, comprising:
an upper vertical link having opposite upper and lower ends, the upper end being coupled to a first attach pin for conjoint rotation therewith;
a lower vertical link having opposite upper and lower ends, the upper end being coupled to the lower end of the upper vertical link for rotation relative thereto and defining a first hinge between the upper and lower vertical links;
a front horizontal link having opposite front end and rear ends, the front end being coupled

Assignees

• Boeing Co

Inventors

• Mellor Mitchell L R

Classifications

• B64C25/32 Primary

  characterised by elements which contact the ground or similar surface  (arrester hooks B64C25/68) · CPC title

• B64C2025/005

  Tail skids for fuselage tail strike protection on tricycle landing gear aircraft · CPC title

• B64C25/52 Primary

  Skis or runners · CPC title

• B64C25/26

  Control or locking systems therefor · CPC title