A known type of aircraft landing gear is a controlled articulation landing gear. Generally speaking, such landing gear have a bogie beam pivotally coupled to a lower portion of a telescoping strut and a bogie control linkage arranged to control the position of the bogie beam as the strut extends and contracts. During take-off, vertical load on the landing gear is progressively reduced and, as such, the shock strut extends. The bogie control linkage controls the orientation of the bogie beam during extension of strut such that the aft axle is lower than the forward axle. In this way, as the aircraft rotates for take-off, the aircraft pivots about the aft axle, thereby providing a height and clearance advantage for the aircraft which allows a higher pitch attitude prior to the aircraft tail touching the ground and as such enables a shorter take-off.
Different types of bogie control linkage are known. A first type, known in the art as a passive controlled articulation linkage, relies on a series of links in combination with an actuator to control the position of the bogie beam. A second type, known as an active controlled articulation linkage, controls the position of the bogie beam by varying the length of a pitch trimming actuator connected directly between the bogie beam and strut.
Generally speaking, an active controlled articulation linkage is more complex than a passive controlled articulation linkage because of the requirement for a flight mode awareness control system and complex electrical and hydraulic systems for controlling the actuator.
However, passive controlled articulation linkages may suffer from a drawback in that during take-off, the bogie beam pitch angle increases to its pitch-up position and then during free-extension of the strut, the bogie beam can be forced to over-rotate and may collide with the strut, causing damage to the bogie beam and/or the strut. It is known to provide “stop blocks” at the region where impact may occur. However, stop blocks and the like can lead to corrosion of the bogie beam and/or the strut.
USPTO Backgrounds
USPTO Backgrounds