US 4,319,333 A · Mach airspeed indicator

Abstract

A mach airspeed indicator capable of internally determining mach number and VMO from measured altitude and airspeed information directly. An internal microprocessor, capable of storing a plurality of selectable VMO curves and a table of mach number versus q.sub.c /P.sub.s, receives the measured altitude and airspeed information, determines VMO and mach number therefrom, and directly drives the VMO and mach number displays where q.sub.c represents the impact pressure and P.sub.s represents the static pressure. The measured altitude and airspeed signals are analog synchro signals. In order to drive the VMO display, the received analog altitude synchro signals are digitized in a synchro-to-digital converter comprising a single multiplying digital-to-analog converter for both sin .theta. and cos .theta. synchro functions, and fed to the microprocessor which verifies the appropriate VMO from the preselected VMO curve, and drives the VMO analog pointer via a stepper motor servo loop closed by the microprocessor. If the VMO is exceeded, the microprocessor provides an overspeed alarm control signal. In order to drive the mach number display, both the received measured analog altitude and airspeed synchro signals are received, digitized in the synchro-to-digital converter, and fed to the microprocessor. The microprocessor converts the digital airspeed signal into q.sub.c /P.sub.s signal which is used to determine mach number from the stored values. The microprocessor then drives the mach number counter display via a separate stepper motor servo loop closed by the common microprocessor.

Claims70

Dependent claims

In an airspeed indicator apparatus comprising a VMO display means responsive to variable measured airspeed and altitude information provided thereto;

the improvement comprising means for receiving said variable measured altitude information and providing an altitude signal therefrom;
and a first closed VMO servo loop operatively connected to said variable altitude information receiving means for receiving said altitude signal therefrom and directly driving said VMO display means in response thereto, said first closed VMO servo loop comprising microprocessor means, VMO servo means operatively connected between said microprocessor means and said VMO display means for directly driving said VMO display means in response to servo control signals provided thereto from said microprocessor means, and VMO display position indicating means operatively connected between said VMO display means and said microprocessor means in a feedback path for providing a signal to said microprocessor means indicative of the display position of said VMO display means, said microprocessor means closing said first closed VMO servo loop and storing a predetermined VMO curve and providing a variable desired VMO value servo control signal to said VMO servo motor means in response to said altitude signal, said microprocessor means being capable of providing a servo control error signal to said VMO servo motor means in response to said VMO display position indication signal for nulling said first closed VMO servo loop at said variable desired VMO value, whereby said microprocessor means directly drives said VMO display means by closing said first closed VMO servo loop.

In an airspeed indicator apparatus comprising a mach number display means for displaying mach number from variable measured airspeed and altitude information provided thereto;

the improvement comprising means for receiving said variable measured altitude and airspeed information and for providing an altitude signal and an airspeed signal therefrom;
and a first closed mach servo loop operatively connected to said variable measured altitude and airspeed information receiving means for receiving said airspeed and altitude signals therefrom and directly driving said mach number display means in response thereto, said first closed mach servo loop comprising microprocessor means, and mach servo motor means operatively connected between said microprocessor means and said mach number display means for directly driving said mach number display means in response to servo control signals provided thereto from said microprocessor means, said microprocessor means further converting said altitude and airspeed signals into an actual mach number value display servo control signal for directly driving said mach number display means in response thereto.

Dependencies are inferred from the claim text.

Mach airspeed indicator

Life of this patent

Mach airspeed indicator

Life of this patent

Abstract

Claims70