Variometer

DETAILED DESCRIPTION The invention has, therefore, more particularly for its object a variometer whose general principal is similar to thart of the above-mentioned application, but is able to utilize the parameters available on the aircraft not having any inertial guidance units.
In order to achieve this result, according to the invention, the value of the instantaneous vertical speed indicated by the needle of the variometer is obtained by incorporating to the filtered vertical speed, a lead phase which is the function of the acceleration following the vertical axis of the airplane J.
sub.
z.
sbsb.
1, calculated from the vertical accelerartion measured according to the axis connected to the aircraft and of the angle of rolling .
phi.
of the aircraft.
The expression of this instantaneous vertical speed is therefore in the form: ##EQU4## formula in which: j.
sub.
z.
sbsb.
1 is the component of the acceleration on the vertical axis connected to the plane; g is the acceleration of gravity; .
phi.
is the angle of roll of the airplane.
According to another embodiment of the invention, the potential vertical speed h.
degree.
.
sub.
T of the aircraft is furnished from the following formula: ##EQU5## in which: I: hx.
degree.
is the instantaneous vertical speed of the aircraft (which is obtained as previously indicated); II: V.
sub.
H is a composite speed which has for its expression: ##EQU6## the expression TAS designating the True Air Speed of the aircraft; .
tau.
'.
sub.
1 and .
tau.
'.
sub.
2 being constants of time; .
theta.
being the longitudinal position of the aircraft; j.
sub.
x.
sbsb.
1 being the component of the acceleration on the longitudinal axis of the aircraft; s being the Laplace operator; III: dVx/dt consists of a mixture of the derivative of the true speed of the aircraft and of the longitudinal accelerartion compensated for gravity, the expression dVx/dt being of the form: ##EQU7## in which .
tau.
.
sub.
3 is a time constant.
An important advantage in the method of determination of the potential vertical speed previously described, consists in that it allows one to obtain, in case of a wind gradient a true readout whatever the airspeed of the aircraft may be, and this, without it being necessary to effect other corrections, as that was the case in the variometer according to the principal patent