Communications: electrical – Aircraft alarm or indicating systems – Flight alarm
Reexamination Certificate
1998-11-30
2001-08-07
Wu, Daniel J. (Department: 2736)
Communications: electrical
Aircraft alarm or indicating systems
Flight alarm
C340S969000, C073S180000
Reexamination Certificate
active
06271769
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to flight instrumentation for aircraft. More particularly, it relates to a measurement, data manipulation and information display system and method for use on air vehicles, wherein the system includes pressure sensors, a data processor, at least one data port for electrically exporting angles from zero lift, and an indicator for communicating information relating to angles from zero lift.
Past and present pressure type angle of attack devices use a variety of differently shaped probes. A hemispherical end sensor is described in U.S. Pat. No. 3,318,146. Angle of attack and angle of side slip both are calculated from the pressure signals present at five ports on the end. This angle of attack measuring device requires use of the probe as described and the probe must be installed at a very precise angle relative to the cord of the wing or some other longitudinal plane of the air machine.
Sharp tipped pitot static tubes with angle of attack sensing ports are shown in U.S. Pat. Nos. 4,096,744 and 4,378,696. These patents show probes providing differential pressures which are used for determining angle of attack. In the '696 patent, a combination of differential pressure at two ports on the probe, measured pitot and static pressure is used. In the '744 patent, measured pitot pressure, pressure at one of the angle of attack sensitive ports and measured impact pressure are utilized for the calculations.
U.S. Pat. No. 5,616,861 discloses a plurality of air sensing probes symmetrically mounted on opposite sides of a vertical center plane of the air vehicle which includes the longitudinal axis of the air vehicle.
In each of the above instances, the angle of attack systems require special probes usually installed at very precise angles relative to the cord of the airfoil, each other, or other longitudinal axis of the air vehicle.
One problem with systems such as those noted above is that the measurement used was based on angle of attack which is the angle between the cord of the airfoil and the relative wind. The above patented devices are representative of the many devices that have been invented and installed on aircraft to produce a known pressure differential at a known angle of attack. Typically, they require that a probe or probes be installed at a fixed angle relative to a known plane of the air vehicle, usually the cord or surface of the wing or longitudinal axis of the air vehicle.
In recent years, there has been emphasis on making pressure sensing probes compact, light and with low drag as illustrated by the devices shown in U.S. Pat. Nos. 4,836,019, 5,616,861 and 5,331,849. However, there is still room for improvement.
U.S. Pat. No. 4,350,314 describes a stall condition detector that uses four pressure ports in the wing which are ported to a capacitance device within the wing. The detector involves four electrically conductive hollow tubes with rods extending up through the tubes. The tubes are filled with a dielectric fluid. Devices of this type may be subject to errors induced by temperature and other forces acting upon the dielectric fluids resulting from turbulence, G loads, slips and skids. Additionally, with the emphasis of higher loaded airfoils, the newer airfoil designs are smaller and thinner, thus having smaller interior compartments, making these devices difficult to install. In addition, the angle of attack display of this type of device does not take into account high lift devices which may significantly reconfigure the shape of the airfoil.
An aircraft instrument system for communicating accurate information involving angles from zero lift, wherein the information may be derived from simple pressure ports rather than known probes or detectors of the type disclosed in the '314 patent, would be advantageous.
SUMMARY OF THE INVENTION
The present invention relates to a measurement and display system for use on air vehicles having an indicator visibly displaying angles from zero lift and having a data port for electrically exporting angles from zero lift. In one embodiment, pressures from upper and lower wing ports and pressures from the typical pitot and static ports of an air vehicle are converted to digital data and mathematically divided one into the other. The result is a coefficient of pressure (CP) which varies uniquely with angles from zero lift of the air vehicle. The angular deviation from angle of zero lift display is designed for air vehicles and is located in the cockpit and displays angles from zero lift on a digital display. The data port electrically exports angles from zero lift to other electronic devices using a compatible communications port. It has been discovered that if the coefficient of pressure data point for zero degrees angular deviation from angle of zero lift and a minimum of one other coefficient of pressure data point is stored permanently in the system's non-volatile memory, other angles from zero lift can be determined given any coefficient of pressure. For any given airfoil it has been discovered that a minimum of two or more coefficient of pressures will accurately define the relationship between the coefficient of pressure and the angular deviation from angle of zero lift. Once the data points are stored in the system's non-volatile memory, all other coefficient of pressures can be equated to a specific angular deviation from angle of zero lift. Thus, in one embodiment, the present invention provides an apparatus and method for measuring pressures, for deriving and storing in non-volatile memory two or more coefficient of pressure data points, and for exporting and displaying the angles from zero lift.
An advantage of the present invention is that a microprocessor may be used to permanently store the two or more coefficient of pressures which may be copied and installed in the angular deviation from angle of zero lift system of similar air vehicles of the same type to accurately display angles from zero lift.
The instrument of the present invention could also measure angle-of attack (AOA) which is the angle between the relative wind and the chord of the airfoil. But the zero reference for AOA is of no value to the pilot and has no aerodynamic significance. In the case of measuring angles from zero lift, the reference zero angle from zero lift is the angle where the air vehicle creates no lift and therefor is the only angle where the induced drag is zero. For symmetrical airfoils, AOA and angles from zero lift are the same. For a nonsymmetrical airfoil, AOA and angles from zero lift vary by a fixed constant.
The present invention provides an apparatus and method for use on aircraft and includes pressure sensors, a processor, at least one data port for electrically exporting angles from zero lift, and an indicator for visibly displaying angles from zero lift. The present invention provides the apparatus and method for measuring angular deviation from angle of zero lift using pressures from pressure sensing ports, assembled with pressure sensors that minimize the need for temperature compensation and a processor that computes angular deviation from angle of zero lift using two or more flight data points permanently recorded into non-volatile memory for a variety of airfoil configurations. In one embodiment, upper and lower airfoil pressure ports ported to an angular deviation from angle of zero lift processor may be simply a small hole or holes bussed together in the upper surfaces of the wing and/or a small hole or holes bussed together in the lower surfaces of the wing and connected to tubes routed to the processor. In this embodiment, there would be no need for probes such as those described in the above-noted patents. For example, the pressure ports for the pitot and static pressures may be from a pitot/static tube or individual pitot and static ports of the type described in the above-noted patents, or may be from the air vehicles airspeed pressure tubes, eliminating the need for a separate pitot static probe.
It will be noted that the existence an
Dorsey & Whitney LLP
Proprietary Software Systems, Inc.
Tweel , Jr. John
Wu Daniel J.
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