The variometer includes a measuring chamber communicating with the atmosphere through a first passageway and an elastically deformable measuring box, positioned within the measuring chamber, communicating with the atmosphere through a second passageway. One of the passageways, preferably the second passageway, is provided with a system of orifice inserts serving to delay pressure equalization between the measuring chamber and the measuring box. The system of orifice inserts includes at least two orifice inserts with successive orifice inserts being separated from each other by an intermediate space. The orifice inserts are threaded into the internally threaded bore of a hollow screw, and preferably three orifice inserts are provided so as to define two intermediate spaces. At least one of the orifice inserts is displaceable axially of the hollow screw, and preferably two orifice inserts are so displaceable. Each orifice insert is a hollow externally threaded member in which the orifice is formed in a bore through a jewel or the like at one end of the orifice insert.
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.
