Abstract: An aircraft includes an active drag control system such as a Laminar Flow Control (LFC) system having a port LFC apparatus and a starboard LFC apparatus. The aircraft has a control system to test how efficiently the LFC system is working by differentially operating the port LFC apparatus and the starboard LFC apparatus, for example by deactivating either LFC apparatus, and measuring the effect on the direction of flight of the aircraft. The control system also can change the direction of the aircraft, and trim the aircraft, by differentially operating the port LFC apparatus and the starboard LFC apparatus.

Abstract: An aircraft landing gear assembly (112) including a shock absorber strut (114), a bogie (120), a link assembly (124), and a movement detector (132). The shock absorber strut includes an upper and a lower telescoping parts (116, 118), the upper part being connectable to the airframe of an aircraft and the lower part being connected to the bogie. The link assembly extends between the upper and lower telescoping parts. The movement detector is arranged to detect movement of the link assembly relative to the bogie. The movement detector includes: a piston (338) slidably received within a cylinder (336), fluid which flows as a result of relative movement between the piston and the cylinder; and a pressure transducer (336) arranged to sense a local pressure change in the fluid.