The present invention relates to detection of errors in global positioners which enable altitude data of an air vehicle to be obtained during a flight.

As is known, global positioners have become essential measurement equipment which are frequently used today in detecting altitude data of an air vehicle. However, in some cases, there are differences between the global positioners and the actual altitude data of the air vehicle. As is known, corrections are made for barometric altitude by using local temperature and pressure values, and the geometric altitude and the barometric altitude are equalized. On the other hand, depending on the air pressure and temperature of the take-off/landing place, the barometric altitude and the altitude value obtained by means of the global positioner differ as the air vehicle gains altitude.

Current calculations are generally based on the QNH pressure correction received by the pilot from the tower. In QNH pressure correction, the pilot inputs a QNH value received from the tower so that he/she allows correction of the barometric altitude.

According to the United States patent document no. US8922427, which is included in the known-state of the art, a distortion detection method is provided for global positioning system (GPS) measurements using the measurements of IMU and Inertial Navigation System (INS) sensors. In this method, differences in parameters obtained with the h elp of GPS and INS at each time instant are used as test statistics. A sequential likelihood ratio test based on said parameter differences is used to detect GPS distortions.

With an air data computer developed with this invention, a system is obtained, which detects exposure of the signals used to obtain data that is critical for air route safety to interruption, jamming, suffocation and distortion in a short time.

The air data computer realized to achieve the object of the invention and defined in the first claim and the claims dependent thereon comprises a first sensor similar to a pitot tube, which is located on the air vehicle and allows measurement of the air pressure acting on the air vehicle; a temperature sensor which allows temperature measurement; an air data unit containing data such as air pressure data received from the first sensor, temperature data received from the second sensor; a control unit which calculates barometric altitude data of the air vehicle by using the pressure value obtained by means of the first sensor; a global positioner which allows data such as position, speed and geometric altitude of the air vehicle to be obtained by the signal received from multiple satellites on the earth orbit.

The air data computer of the invention comprises a control unit which calculates a new barometric altitude by using sea level temperature data obtained by means of the first sensor and compares the calculated barometric altitude value with the geometric altitude data obtained by the global positioner, thus enabling detection of spoofing and/or jamming distortions that occur in the global positioner.

In an embodiment of the invention, the air data computer comprises a control unit which allows a more accurate altitude value to be obtained for the air vehicle by comparing the barometric altitude value corrected with sea level temperature value with the geometric altitude data obtained by means of the global positioner.

In an embodiment of the invention, the air data computer comprises a filter which allows the control unit to make a more accurate altitude estimation for the air vehicle.

In an embodiment of the invention, the air data computer comprises a Kalman type filter which allows the control unit to send more accurate altitude data to the air vehicle and makes altitude estimation.

In an embodiment of the invention, the air data computer comprises a control unit which statistically compares the barometric altitude data, which is calculated by using sea level temperature value, with the geometric altitude data obtained by means of the global positioner, and in case of a deviation, deactivates the global positioner and enables generation of an error signal.

In an embodiment of the invention, the air data computer comprises a control unit which allows barometric altitude data to be updated by means of QNH pressure correction of the barometric altitude data calculated in the air data unit, wherein the QNH pressure correction is input by the pilot to the tower side.

In an embodiment of the invention, the air data computer comprises a control unit which allows calculation of an actual value for the sea level temperature value on the air vehicle.

In an embodiment of the invention, the air data computer comprises a control unit which allows barometric altitude calculation by using an approximate sea level temperature that is obtained by statistically averaging the sea level temperature value and the desired number of values determined with the sliding window method.

In an embodiment of the invention, the air data computer comprises a global positioner in the form of any of the GPS, Galileo, GLONASS, COMPASS and QZZS satellite networks.

The air data computer realized to achieve the object of the present invention is illustrated in the attached drawings, in which:

Figure 1 is a block diagram of an air data computer.

All the parts illustrated in figures are individually assigned a reference numeral and the corresponding terms of these numbers are listed below:

1. Air Data Computer

2. First Sensor

3. Second Sensor

4. Air Data Unit

5. Control Unit

6. Global Positioner

7. Filter

The air data computer (1) comprises a first sensor (2) which is located on the air vehicle and allows measurement of the air pressure; a second sensor (3) which allows temperature measurement; an air data unit (4) containing data such as air pressure and temperature, which are obtained by means of the first sensor (2) and the second sensor (3); a control unit (5) which allows calculation of barometric altitude data of the air vehicle by using the air pressure data received from the air data unit (4); at least one global positioner (6) which allows real-time geometric altitude data of the air vehicle to be obtained by the signal received from multiple satellites on the earth orbit (Figure 1).

The air data computer (1) of the invention comprises a control unit (5) which allows calculation of a real-time altitude data of the air vehicle by statistically comparing the barometric altitude value, which is calculated by correcting with sea level temperature value, with the geometric altitude value obtained by means of the global positioner (6).

Pressure is measured by means of the pitot tube-like first sensor (2) which allows measurement of the air pressure acting on the air vehicle. The measured pressure value is transferred to the air data system (4). In the air data system (4), the pressure value acting on the air vehicle and the sea level temperature accepted as 15°C are taken into account by the control unit (5), so that the altitude data and the barometric altitude data of the air vehicle is determined. Moreover, the geometric altitude data obtained by the global positioner (6) informs the air vehicle regarding its altitude.

While the air vehicle is on the runway, the temperature measured by the second sensor (3) and the sea level temperature value of the region relative to the pressure ratio of the runway and air vehicle are calculated by the control unit (5). Using the temperature value obtained, a more accurate barometric altitude data of the air vehicle is calculated by the control unit (5). The barometric data calculated by the control unit (5) and the geometric altitude data obtained by means of the global positioner (6) are compared; and if the difference statistic therebetween is above a determined threshold value, it is detected that the global positioner (6) is subjected to distortions.

In an embodiment of the invention, the air data computer (1) comprises a control unit (5) which allows calculation of a real-time altitude data of the air vehicle by statistically comparing the barometric altitude value, which is calculated by correcting with sea level temperature value, with the geometric altitude value obtained by means of the global positioner (6). Thus, it is detected that the global positioner (6) is subjected to spoofing and/or jamming distortions. In an embodiment of the invention, the air data computer (1) comprises a filter (7) which allows the control unit (5) to estimate a current altitude data of the air vehicle. Thus, more reliable altitude data is obtained in the air vehicle by means of the filter (7) (Figure 1).

In an embodiment of the invention, the air data computer (1) comprises a Kalman-type filter (7) which allows estimation of a real-time altitude data of the air vehicle by using the barometric altitude value, which is calculated by correcting with sea level temperature value, and the geometric altitude data obtained from the global positioner (6). The barometric altitude value calculated by sea level temperature and pressure values and the geometric altitude data obtained by means of the global positioner (6) are input to the Kalman-type filter (7) operated in the control unit (5). Real-time altitude data of the air vehicle are estimated by means of the filter (7).

In an embodiment of the invention, the air data computer (1) comprises a control unit (5) which deactivates the global positioner (6) and allows generation of an error signal if a ratio of the difference between the barometric altitude data, which is calculated by correcting with sea level temperature value, and the geometric altitude data obtained by means of the global positioner (6) to the square root of the total error variances of these altitude values deviates more than the determined threshold value. Statistical calculations are made with the ratio of the difference between instantaneous altitude data estimated by the filter (7) and the instantaneous altitude measurements obtained by the global positioner (6) to the square root of the total error variances of these measurement values, the limit values of the statistics are determined, and the threshold value is selected by the user. With the two hypotheses generated, a defective state and a non-defective state in the altitude data measured by the global locator (6) can be detected. According to the statistical result, when the threshold value selected by the user is lower than the statistical calculation, the altitude data measured by the global positioner (6) is considered to be in the defective state, and when the threshold value is higher than the statistical calculation, the altitude data is considered to be in the non-defective state. The threshold value can be updated by collecting flight data containing distortions occurring in the global positioner (6).

In an embodiment of the invention, the air data computer (1) comprises a control unit (5) which allows direct correction of barometric altitude data by performing QNH pressure correction received from the tower in addition to the barometric altitude value calculated by means of the air data unit (4). The control unit (5) calculates the barometric altitude data with the pressure value obtained from the air data unit (4). The QNH pressure correction received from the tower is input by the pilot. Thus, the barometric altitude value is updated by means of the control unit (5).

In an embodiment of the invention, the air data computer (1) comprises a control unit (5) which allows the sea level temperature value on the air vehicle to be calculated simultaneously. While the air vehicle is on the runway, the second sensor (3) measures the runway temperature value. The temperature value on the runway and the sea level temperature value are measured by the control unit (5) by making pressure ratios. Thus, the actual sea level temperature of the region where the air vehicle is flying is calculated. More accurate results are obtained by taking into account the actual sea level temperature in the barometric altitude calculation formula, rather than the assumptions regarding sea level temperature. In addition, barometric altitude and geometric altitude differences occurring at high altitudes are prevented.

In an embodiment of the invention, the air data computer (1) comprises a control unit (5) which enables the sea level temperature value in the air data unit (4) to be obtained by statistically calculating the number of values determined by the sliding window method. With the sliding window method, an average of the desired number of temperature values by the user is transferred to the air data unit (4) by means of the control unit (5). The new temperature value obtained with the sliding window method is added, the first temperature value taken into account is removed, and the temperatures are averaged without changing the number of temperature values.

In an embodiment of the invention, the air data computer (1) comprises a global positioner (6) as in any of the satellite network types such as GPS, Galileo, GLONASS, COMPASS and QZZS. Thus, data of the global positioners (6) belonging to different countries that are desired to be used in the air vehicle can be utilised.