Abstract: The cylinder may be an aircraft landing gear axle. The items may be pick-ups the sense axle deformation. A ring (30) for supporting the pick-ups is made of highly resilient material. It is initially of such a size that its cylinder-engaging surface overlaps the cylindrical surface it is to engage. The ring is then deformed by urging at least two points (34 to 37) around its circumference to increase the degree of overlap. While maintaining the deforming force on the ring, its cylinder-engaging surface (31) is machined so that there is no longer any overlap, and still maintaining the force, the ring is engaged with the cylinder. The force is then removed. The said points move resiliently away from the cylinder, but intermediate points are consequently resiliently urged into contact with the cylinder. The contact is smooth and progressive, thus avoiding the kind of stress concentrations that could reduce cylinder life by fatigue, etc.

Abstract: This invention concerns an improved variometer which is used in aircraft which operates on a circuit that calculates the instantaneous speed hx.degree. of the aircraft and the potential vertical speed of the aircraft h.sub.T .degree.. A luminous display is also provided to display the values so calculated to alert the pilot of the aircraft.The instantaneous vertical speed hx.degree. is obtained by means of a circuit solving the equation: ##EQU1## in which j.sub.z.sbsb. is the component of the acceleration on the vertical axis of the aircraft, g is the acceleration of gravity, .phi. is the angle of roll of the airplane, s is the Laplace operator, .tau..sub.1 and .tau..sub.2 are constants of time and h.degree..sub.A is a signal of vertical speed.

Abstract: A variometer for an aerodyne. The variometer has at least one dial conventionally graduated to represent speed, a needle indicating on said graduation the instantaneous vertical speed. The variometer also has an indicator which is representative of the potential vertical speed, and can move around the dial so that the position of the indicator with respect to the needle indicates instantaneously the acceleration on the trajectory of the aircraft.