Large amphibious aircraft radio compass deviation calibration method

Abstract

The invention belongs to the field of avionics system design, and particularly relates to a large amphibious aircraft radio compass deviation calibration method, which comprises the following steps of: completing installation, calibration and power-on inspection according to the size of an aircraft and part of airborne equipment, and calibrating a site environment state, coordinates of a ground omnidirectional beacon station and the like. The invention provides a compass deviation calibration method for the radio compass of the aircraft, so that the radio compass compass deviation calibration of the aircraft can be more efficiently completed in a general assembly base, the cost is reduced, and the production efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of avionics system design, and in particular relates to a method for calibrating compass error of a large amphibious aircraft. Background Technology

[0002] Due to their superior amphibious capabilities, which are unmatched by land-based aircraft and ships, large amphibious aircraft have received increasing attention from various countries in recent years for civilian applications. The unique amphibious characteristics of amphibious aircraft make them suitable for a wide range of applications, including forest firefighting and water rescue, as well as marine environmental monitoring, near-shore and far-sea patrols, and the transport of strategic materials. Radio compasses have been used for a long time; during flight, aircraft can use ground beacon stations to guide them and correct their course to stay on the designated route. While aircraft can also fly using a combination of global satellite navigation systems and inertial navigation systems, satellite systems are significantly affected by satellite signals and can be susceptible to deception and interference, especially in high-latitude regions where satellite signals are limited. Radio compasses, on the other hand, rely on ground base stations, which offer stable and reliable signals. Furthermore, ground base stations are widely distributed and have low maintenance costs, making them an indispensable navigation device.

[0003] Radio waves are affected during transmission by factors such as the aircraft's metal fuselage, the ionosphere, atmospheric conditions (e.g., temperature and humidity), the nature of the Earth's surface, geographical environment, and human interference, leading to directional errors. These errors can be broadly categorized into interference errors from the metal conductor near the loop antenna, radio wave propagation errors, and equipment errors. When radio waves radiated by a ground station reach metal objects such as the aircraft fuselage, they induce alternating currents in the metal. These currents then generate radiated radio waves around the metal object; this phenomenon is called secondary radiation. When the secondary radiated radio waves are superimposed on the original signal waves, the direction of the loop antenna acting on the composite wave differs from the original wave propagation direction by an angle, thus altering the directional direction and causing a directional error. This angle is called quadrant error or compass error. Compass error can lead to significant errors in the relative azimuth angle. To compensate for these errors, the radio compass needs to be calibrated for compass error. Therefore, conducting aircraft radio compass error calibration is of great significance.

[0004] To ensure the proper functioning of the radio compass of a large amphibious aircraft, compass error calibration is essential. Generally, compass error calibration is carried out at a compass field or airport runway, and it must be conducted during the day. This involves the issue of renting a dedicated compass field or runway. In addition, the aircraft is large, and the space occupied by the aircraft during compass error calibration is large. Therefore, it is particularly important to find a calibration method that is not limited by location or funding. Summary of the Invention

[0005] The purpose of this invention is to propose a method for calibrating the compass error of a large amphibious aircraft radio compass, which provides strong support for the normal use of the aircraft radio compass and offers multiple navigation possibilities for the aircraft.

[0006] The technical solution of this invention: A method for calibrating the compass error of a large amphibious aircraft using a radio compass includes: Step 1: Install a radio compass on a large amphibious aircraft; Step 2: Determine the location and operational status of the ground omnidirectional beacon stations, and determine the location of the helipad; Step 3: Install the inertial navigation system on the large amphibious aircraft, and perform calibration and power-on checks on the inertial navigation system. At the same time, perform power-on checks and mutual tests on the radio compass, aircraft display and control system, integrated automatic tuning system, and integrated radio navigation system. Step 4: Determine the 0° azimuth line and select a measurement point on the 0° azimuth line; Step 5: Move the aircraft to the designated parking apron, with the aircraft's center located at the measurement point on the 0° bearing line; Step 6: The radio compass system receives the signal sent by the ground omnidirectional beacon station, rotates the aircraft so that the longitudinal axis of the aircraft is aligned with the 0° bearing line and the nose is facing the omnidirectional beacon station, and records and displays the inertial magnetic heading information and the relative bearing angle RB′ of the radio compass read by the control system. Step 7: Rotate the aircraft according to the inertial navigation magnetic heading information, starting from the 0° bearing line, and rotate it at several angles in sequence to obtain the relative bearing angle RB relative to the omnidirectional beacon station at multiple rotation angles; at the same time, read out the relative bearing angle RB′ of the radio compass corresponding to each rotation angle through the display control system. Step 8: Calculate the difference between RB and RB′ at the corresponding rotation angle to obtain the quadrant error correction QEC; Step 9: Plot the "QEC-RB" curve to obtain the error distribution pattern under different azimuth angles; Step 10: Perform staggered binding according to the distribution pattern; Step 11: After binding, repeat steps 6-8 to verify the binding result.

[0007] Furthermore, in step 1, the installation of the radio compass includes the installation of a processor and an ADF antenna. The ADF antenna is positioned on the top of the fuselage of the large amphibious aircraft, and the longitudinal section of the ADF antenna coincides with the plane of symmetry of the aircraft.

[0008] Furthermore, in step 3, the inertial navigation navigation accuracy reaches above 0.1°; Before powering on the radio compass, complete the installation and testing of the integrated automatic tuning system, display control system, integrated processing system, and position detection and take-up control unit. Complete the continuity and insulation resistance checks of all cables. During the power-on check of the power system, ensure that the equipment involved in the above systems is powered on normally. Move the aircraft to the designated parking apron, ensuring that the omnidirectional beacon station signal is not blocked. Power on the integrated automatic tuning system, display control system, integrated processing system, and position detection and retraction control unit. Adjust the ADF antenna offset, display the ADF antenna azimuth angle and reading, and complete the power-on check and mutual testing.

[0009] Furthermore, in step 4, based on the relative positions between the omnidirectional beacon station, the apron, and the airport runway, the azimuth angle of the 0° azimuth line is calculated using trigonometric functions, thus determining the 0° azimuth line.

[0010] Furthermore, the large amphibious aircraft is equipped with two sets of NAV-4000 radio compasses. Before performing step 6, the compass alignment of the two sets of radio compasses is first performed. All pins of one set of radio compasses are left empty; pins 41 and 46 of the other set of radio compasses are grounded, and the remaining pins are left empty.

[0011] Furthermore, step 6 includes: Step 6.1: Between two hours after sunrise and two hours before sunset, move the aircraft to the designated parking apron, with the center of the aircraft at the measurement point; Step 6.2: Power on the display and control system, integrated automatic tuning system, integrated processing system, integrated radio navigation system, and inertial reference system of the large amphibious aircraft. Close all openings of the aircraft, leaving only the ground power supply line accessible through the rear cabin door on one side of the aircraft. Step 6.3: Set the radio compass to ADF mode and tune its frequency to 204kHz. The radio compass will then begin receiving signals from the ground omnidirectional beacon station. Step 6.4: Rotate the aircraft so that its longitudinal axis is aligned with the 0° bearing line and the nose is facing the omnidirectional beacon station. Record and display the inertial magnetic heading and the relative azimuth angle RB′ of the radio compass at 0° bearing, as read by the control system.

[0012] Further, step 7 includes: rotating the aircraft according to the inertial magnetic heading, starting from the 0° azimuth line, and sequentially rotating by 30°, 15°, 15°, 30°, 30°, 15°, 15°, 30°, 30°, 15°, 15°, 30°, 30°, 15°, 15°, and 30°. The relative azimuth angles RB with respect to the omnidirectional beacon station at these multiple rotation angles are 0°, 30°, 45°, 60°, 90°, 120°, and 135°, respectively. The relative azimuth angles RB′ of the radio compass corresponding to the aircraft's rotations of 30°, 15°, 180°, 210°, 225°, 240°, 270°, 300°, 315°, 330°, and 360° are displayed and read out by the display control system.

[0013] Further, in step 8, the differences between the relative azimuth angles RB′ obtained from the radio compass when the relative azimuth angles RB are 0°, 30°, 45°, 60°, 90°, 120°, 135°, 150°, 180°, 210°, 225°, 240°, 270°, 300°, 315°, 330°, and 360° respectively, and the differences between these values ​​and the differences between the relative azimuth angles RB′ obtained from the aircraft rotating 30°, 15°, 15°, 30°, 30°, 15°, 15°, 30°, 30°, 15°, 15°, 30°, 30°, 15°, 15°, 30°, 15°, 15°, and 30° respectively, are calculated to obtain multiple quadrant error corrections (QECs).

[0014] Furthermore, in step 9, the plotted "QEC-RB" curve has RB as the horizontal axis and QEC as the vertical axis, and the curve approximates a sine / cosine curve.

[0015] Furthermore, in step 10, the compass alignment requirement for large amphibious aircraft is 25°. The two sets of radio compasses are re-aligned, that is, pins 40, 46, and 47 of the two sets of radio compasses are grounded and the remaining pins are left empty. Furthermore, in step 11, the aircraft is rotated again starting from the 0° line, rotating sequentially according to the inertial magnetic heading, 45° each time, for a total of 7 rotations. The relative azimuth angles RB with respect to the omnidirectional beacon station are 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°, respectively. The relative azimuth angles RB′ of the aircraft at each rotation angle are read out by the display control system. This process is completed two hours before sunset. The QEC calculation was performed again, and the result was between -3° and +3°, thus completing the radio compass error calibration.

[0016] The beneficial effects of this invention are as follows: This invention provides a method for calibrating the compass error of a large amphibious aircraft radio compass. Based on the size of the aircraft itself, some airborne equipment is installed, calibrated, and powered on for inspection. The calibration site environmental conditions and ground omnidirectional beacon station coordinates are also checked. This provides a method for calibrating the compass error of the aircraft radio compass, making it easier to complete the radio compass error calibration more efficiently at the final assembly base, reducing costs and improving production efficiency. Attached Figure Description

[0017] Figure 1 This invention provides the relative positions of the final assembly base and the runway. Figure 2 This invention provides an airport ground radio navigation and instrument landing station; Figure 3 This invention provides a 0° azimuth line diagram for radio compass error calibration of a large amphibious aircraft at the final assembly base; Figure 4 This is an example diagram illustrating the relative azimuth angle between the aircraft and the omnidirectional beacon station according to the present invention. Detailed Implementation

[0018] The following description of embodiments provides a more detailed explanation of the specific implementation of the present invention, including the shape and structure of each component, the relative positions and connections between the parts, the function and working principle of each part, the manufacturing process, and the operation and use methods, in order to help those skilled in the art to have a more complete, accurate, and in-depth understanding of the concept and technical solution of the present invention. One embodiment of the present invention is as follows: A method for calibrating the compass error of a large amphibious aircraft using a radio compass is proposed, including: Step 1: Install a radio compass on a large amphibious aircraft; Step 1 includes the installation of a processor and an ADF antenna. The ADF antenna is located on the top of the fuselage of the large amphibious aircraft, and the longitudinal section of the ADF antenna coincides with the plane of symmetry of the aircraft.

[0019] Step 2: Determine the location and operational status of the ground omnidirectional beacon stations, and determine the location of the helipad; Step 3: Install the inertial navigation system on the large amphibious aircraft, and perform calibration and power-on checks on the inertial navigation system, ensuring that the inertial navigation navigation accuracy reaches 0.1° or higher; at the same time, perform power-on checks and mutual tests on the radio compass, aircraft display and control system, integrated automatic tuning system, and integrated radio navigation system. Before powering on the radio compass, complete the installation and testing of the integrated automatic tuning system, display control system, integrated processing system, and position detection and take-up control unit. Complete the continuity and insulation resistance checks of all cables. During the power-on check of the power system, ensure that the equipment involved in the above systems is powered on normally. Move the aircraft to the designated parking apron, ensuring that the omnidirectional beacon station signal is not blocked. Power on the integrated automatic tuning system, display control system, integrated processing system, and position detection and retraction control unit. Adjust the ADF antenna offset, display the ADF antenna azimuth angle and reading, and complete the power-on check and mutual testing.

[0020] Step 4: Determine the 0° azimuth line and select a measurement point on the 0° azimuth line; In step 4, based on the relative positions of the omnidirectional beacon station, the apron, and the airport runway, the azimuth angle of the 0° azimuth line is calculated using trigonometric functions, thus determining the 0° azimuth line.

[0021] Step 5: Move the aircraft to the designated parking apron, with the aircraft's center located at the measurement point on the 0° bearing line; The large amphibious aircraft is equipped with two sets of NAV-4000 radio compasses. Before performing step 6, the compass alignment of the two sets of radio compasses is first performed. All pins of one set of radio compasses are left empty; pins 41 and 46 of the other set of radio compasses are grounded, and the remaining pins are left empty.

[0022] Step 6: The radio compass system receives the signal sent by the ground omnidirectional beacon station, rotates the aircraft so that the longitudinal axis of the aircraft is aligned with the 0° bearing line and the nose is facing the omnidirectional beacon station, and records and displays the inertial magnetic heading information and the relative bearing angle RB′ of the radio compass read by the control system. Step 6 includes: Step 6.1: Between two hours after sunrise and two hours before sunset, move the aircraft to the designated parking apron, with the center of the aircraft at the measurement point; Step 6.2: Power on the display and control system, integrated automatic tuning system, integrated processing system, integrated radio navigation system, and inertial reference system of the large amphibious aircraft. Close all openings of the aircraft, leaving only the ground power supply line accessible through the rear cabin door on one side of the aircraft. Step 6.3: Set the radio compass to ADF mode and tune its frequency to 204kHz. The radio compass will then begin receiving signals from the ground omnidirectional beacon station. Step 6.4: Rotate the aircraft so that its longitudinal axis is aligned with the 0° bearing line and the nose is facing the omnidirectional beacon station. Record and display the inertial magnetic heading and the relative azimuth angle RB′ of the radio compass at 0° bearing, as read by the control system.

[0023] Step 7: Rotate the aircraft according to the inertial magnetic heading information, starting from the 0° bearing line, and rotate it sequentially by several angles to obtain the relative azimuth angle RB relative to the omnidirectional beacon station at multiple rotation angles; simultaneously, read the relative azimuth angle RB′ of the radio compass corresponding to each rotation angle through the display and control system; Step 7 includes: rotating the aircraft according to the inertial magnetic heading, starting from the 0° bearing line, and rotating it sequentially by 30°, 15°, 15°, 30°, 30°, 15°, 15°, 30°, 30°, 15°, 15°, 30°, 30°, 15°, 15°, 30°, 15°, 30°, 15°, 15°, 30°, at multiple rotation angles... The relative azimuth angles RB with respect to the omnidirectional beacon station are 0°, 30°, 45°, 60°, 90°, 120°, 135°, 150°, 180°, 210°, 225°, 240°, 270°, 300°, 315°, 330°, and 360°, respectively. At the same time, the relative azimuth angles RB′ of the radio compass corresponding to the aircraft rotating sequentially by 30°, 15°, 15°, 30°, 30°, 15°, 15°, 30°, 30°, 15°, 15°, 30°, 30°, 15°, 15°, and 30° are read out by the display control system.

[0024] Step 8: Calculate the difference between RB and RB′ at the corresponding rotation angle to obtain the quadrant error correction QEC; In step 8, the differences between the relative azimuth angles RB and the relative azimuth angles RB′ of the radio compass obtained by rotating the aircraft by 30°, 15°, 15°, 30°, 15°, 180°, 210°, 225°, 240°, 270°, 300°, 315°, 330°, and 360° respectively, relative to the omnidirectional beacon station, are calculated one-to-one, and obtained by corresponding to the relative azimuth angles RB′ of the radio compass obtained by rotating the aircraft by 30°, 15°, 15°, 30°, 30°, 15°, 15°, 30°, 30°, 15°, 15°, 30°, 30°, 15°, 15°, and 30° respectively. This yields multiple quadrant error corrections (QECs).

[0025] Step 9: Plot the "QEC-RB" curve to obtain the error distribution pattern under different azimuth angles; the plotted "QEC-RB" curve has RB as the horizontal axis and QEC as the vertical axis, and the curve approximates a sine / cosine curve.

[0026] Step 10: Based on the "QEC-RB" curve and in accordance with the compass conversion and binding requirements for large amphibious aircraft, perform compass conversion and binding on the radio compass.

[0027] In step 10, the compass alignment requirement for large amphibious aircraft is 25°. The two sets of radio compasses are re-aligned, that is, pins 40, 46, and 47 of the two sets of radio compasses are grounded and the remaining pins are left empty. Step 11: Repeat steps 6-8 to verify the binding result.

[0028] In step 11, the aircraft restarts its rotation from the 0° line, rotating sequentially according to the inertial magnetic heading, 45° each time, for a total of 7 rotations. The relative azimuth angles RB relative to the omnidirectional beacon station are 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°, respectively. The relative azimuth angles RB′ of each rotation angle are read out by the display and control system. This process is completed two hours before sunset. The QEC calculation was performed again, and the result was between -3° and +3°, indicating that the radio compass error calibration was successfully completed.

[0029] A second embodiment of the present invention proposes a method for calibrating the compass error of a large amphibious aircraft using a radio compass, comprising: I. Technical Preparation 1) Installing the ADF antenna: The longitudinal section of the automatic direction finder (ADF antenna) is aligned with the aircraft's plane of symmetry using the mounting bolts in the drawings. Because a certain large amphibious aircraft operates on water, the antenna cannot be mounted on the fuselage; therefore, the ADF antenna is mounted on the top of the fuselage.

[0030] 2) Before starting the radio compass power-on check, complete the installation and testing related to the integrated automatic tuning system, display control system, integrated processing system, and position detection and retraction control unit. Complete the continuity and insulation resistance checks of all aircraft cables, and ensure the power supply to the aforementioned systems is normal during the onboard power-on check of the power system. Tow the aircraft to the apron, ensuring the omnidirectional beacon station (NDB) signal is not obstructed. Power on the relevant equipment of the integrated automatic tuning system, display control system, integrated processing system, and position detection and retraction control unit. Adjust the ADF offset and display the ADF azimuth and reading on the interface data unit (IDU) to complete the power-on check.

[0031] 3) Because radio compass calibration requires the aircraft to rotate 360°, marking the 0° azimuth line is crucial for the aircraft's radio compass calibration. The 0° azimuth line is calculated based on the runway angle and the location of the ground station. A large amphibious aircraft chose the final assembly base apron as the calibration site. Considering the need to select a ground station that can provide sufficient and clear signals for radio compass calibration, and also considering its distance from tall buildings, the "Gaolan NDB" navigation station was selected for testing based on the location of navigation stations near the apron. The 0° azimuth line angle was calculated using the sine and cosine theorems, based on the airport runway, the relative positions of the Gaolan NDB station, and the runway. A certain company is the manufacturer and developer of this aircraft. Its apron, located near Workshop 203, is situated near the end of the runway. Since the NDB (Navigate the Main) monitoring station is relatively far away, the distance between the runway end and the apron is negligible. Therefore, the location near the Gaolan NDB station at the end of the apron is selected as the starting point of the 0° bearing line. A marker line parallel to the runway is drawn from this starting point, followed by another bearing line with a 2° angle. This bearing line is the 0° bearing line. To ensure the aircraft can rotate 360° on the apron, a measurement point is selected on the 0° bearing line. The selection of this measurement point takes into account the aircraft's turning radius and the existing length and width of the apron.

[0032] II. Conditions and Procedures 1) Radio waves transmitted by ground-based radio stations undergo complex changes during propagation due to the influence of the ionosphere, the earth, and the sea surface, resulting in transmission errors. The magnitude of these errors generally varies depending on the receiving location, time, and season. The errors in radio direction finding caused by radio wave propagation mainly include polarization errors (nighttime effect), mountain effect errors, and coastal effect errors. The nighttime effect typically occurs between two hours before sunset and two hours after sunrise, and the direction finding error caused by the nighttime effect is generally 10°~15°. Due to the constraints of aircraft manufacturing, minimizing the impact of the nighttime effect is a primary consideration under limited conditions. Therefore, radio compass calibration must be performed during the daytime, between two hours after sunrise and two hours before sunset.

[0033] 2) In addition to the equipment involved in the power-on check of the radio compass, the aircraft must also complete the installation and calibration of the inertial reference system and pass the power-on check.

[0034] 3) Implementation steps Step 1: Connect the two sets of radio compasses to the wiring and perform compass binding. Set all pins of one set to empty, and ground pins 41 and 46 of the other set (generally, large aircraft are bound from 10°). Leave the rest empty. Step Two: Two hours after sunrise, tow the aircraft to the apron, with the center of the aircraft at the measurement point. Power on the aircraft's display control system, integrated automatic tuning system, integrated processing system, integrated radio navigation system, and inertial reference system. Close all aircraft doors, windows, and other openings, leaving only the ground power supply line accessible through the rear cabin door on one side of the aircraft. Step 3: Operate the radio tuning unit to set the radio compass to ADF mode and tune its frequency to 204kHz; Step 4: Rotate the aircraft so that its longitudinal axis is aligned with the 0° bearing line and its nose is facing the NDB station. Record the inertial magnetic heading and the relative azimuth angle (RB′) from the radio compass, as read by the display and control system. Rotate the aircraft according to the inertial magnetic heading, adding the following angles: 30°, 15°, 15°, 30°, 30°, 15°, 15°, 30°, 30°, 15°, 15°, 30°, 30°, 15°, 15°, 30°. The relative azimuth angles (RB) relative to the selected station are 0°, 30°, 45°, 60°, 90°, 120°, 135°, 150°, 180°, 210°, 225°, 240°, 270°, 300°, 315°, 330°, and 360° respectively. Read the relative azimuth angle (RB′) for each state through the display and control system and record the degree values. Step 5: Calculate QEC (Quadrant Error Correction), QEC = RB (Beacon) - RB′; Step 6: Plot the "QEC-RB" curve (the horizontal axis is RB, and the vertical axis is QEC). The curve should approximate a sine / cosine curve. Step 7: Based on the QEC curve, the compass deviation of a large amphibious aircraft is set to 25°. Re-set the two radio compasses, grounding pins 40, 46, and 47 of both devices and leaving the remaining pins empty. Allow the aircraft to rotate again from the 0° line, using the inertial magnetic heading in increments of 45°. The relative azimuth angles (RB) relative to the selected stations are 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315° respectively. The relative azimuth angles (RB′) for each state are read and recorded using the display and control system. This process is completed two hours before sunset.

[0035] Step 8: Perform QEC calculation based on the results of the second rotation. The calculation results are between -3° and +3°.

[0036] III. Flight Verification after Calibration The test flight was conducted according to AC 25-7D, and the flight results met the requirements of a certain large amphibious aircraft. The test flight method is not described in detail in this paper, but it is shown that the test flight results further verified the effectiveness of the ground compass calibration method.

[0037] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for calibrating compass error of a large amphibious aircraft using a radio compass, characterized in that, include: Step 1: Install a radio compass on a large amphibious aircraft; Step 2: Determine the location and operational status of the ground omnidirectional beacon stations, and determine the location of the helipad; Step 3: Install the inertial navigation system on the large amphibious aircraft, and perform calibration and power-on checks on the inertial navigation system. At the same time, perform power-on checks and mutual tests on the radio compass, aircraft display and control system, integrated automatic tuning system, and integrated radio navigation system. Step 4: Determine the 0° azimuth line and select a measurement point on the 0° azimuth line; Step 5: Move the aircraft to the designated parking apron, with the aircraft's center located at the measurement point on the 0° bearing line; Step 6: The radio compass system receives the signal sent by the ground omnidirectional beacon station, rotates the aircraft so that the longitudinal axis of the aircraft is aligned with the 0° bearing line and the nose is facing the omnidirectional beacon station, and records and displays the inertial magnetic heading information and the relative bearing angle RB′ of the radio compass read by the control system. Step 7: Rotate the aircraft according to the inertial navigation magnetic heading information, starting from the 0° bearing line, and rotate it at several angles in sequence to obtain the relative bearing angle RB relative to the omnidirectional beacon station at multiple rotation angles; at the same time, read out the relative bearing angle RB′ of the radio compass corresponding to each rotation angle through the display control system. Step 8: Calculate the difference between RB and RB′ at the corresponding rotation angle to obtain the quadrant error correction QEC; Step 9: Plot the "QEC-RB" curve to obtain the error distribution pattern under different azimuth angles; Step 10: Perform binding according to the error distribution pattern; Step 11: After binding, repeat steps 6-8 to verify the binding result.

2. The method for calibrating compass error of a large amphibious aircraft radio compass according to claim 1, characterized in that, In step 1, the installation of the radio compass includes the installation of the processor and the ADF antenna. The ADF antenna is positioned on the top of the fuselage of the large amphibious aircraft, and the longitudinal section of the ADF antenna coincides with the plane of symmetry of the aircraft.

3. The method for calibrating compass error of a large amphibious aircraft radio compass according to claim 1, characterized in that, In step 3, the inertial navigation navigation accuracy reaches above 0.1°; Before powering on the radio compass, complete the installation and testing of the integrated automatic tuning system, display control system, integrated processing system, and position detection and take-up control unit. Complete the continuity and insulation resistance checks of all cables. During the power-on check of the power system, ensure that the equipment involved in the above systems is powered on normally. Move the aircraft to the designated parking apron, ensuring that the omnidirectional beacon station signal is not blocked. Power on the integrated automatic tuning system, display control system, integrated processing system, and position detection and retraction control unit. Adjust the ADF antenna offset, display the ADF antenna azimuth angle and reading, and complete the power-on check and mutual testing.

4. The method for calibrating compass error of a large amphibious aircraft radio compass according to claim 3, characterized in that, In step 4, based on the relative positions of the omnidirectional beacon station, the apron, and the airport runway, the azimuth angle of the 0° azimuth line is calculated using trigonometric functions, thus determining the 0° azimuth line.

5. The method for calibrating compass error of a large amphibious aircraft radio compass according to claim 4, characterized in that, The large amphibious aircraft is equipped with two sets of NAV-4000 radio compasses. Before performing step 6, the compass alignment of the two sets of radio compasses is first performed. All pins of one set of radio compasses are left empty; pins 41 and 46 of the other set of radio compasses are grounded, and the remaining pins are left empty.

6. The method for calibrating compass error of a large amphibious aircraft radio compass according to claim 5, characterized in that, Step 6 includes: Step 6.1: Between two hours after sunrise and two hours before sunset, move the aircraft to the designated parking apron, with the center of the aircraft at the measurement point; Step 6.2: Power on the display and control system, integrated automatic tuning system, integrated processing system, integrated radio navigation system, and inertial reference system of the large amphibious aircraft. Close all openings of the aircraft, leaving only the ground power supply line accessible through the rear cabin door on one side of the aircraft. Step 6.3: Set the radio compass to ADF mode and tune its frequency to 204kHz. The radio compass will then begin receiving signals from the ground omnidirectional beacon station. Step 6.4: Rotate the aircraft so that its longitudinal axis is aligned with the 0° bearing line and the nose is facing the omnidirectional beacon station. Record and display the inertial magnetic heading and the relative azimuth angle RB′ of the radio compass at 0° bearing, as read by the control system.

7. The method for calibrating compass error of a large amphibious aircraft radio compass according to claim 6, characterized in that, Step 7 includes: rotating the aircraft according to the inertial magnetic heading, starting from the 0° azimuth line, and sequentially rotating by 30°, 15°, 15°, 30°, 30°, 15°, 15°, 30°, 30°, 15°, 15°, 30°, 30°, 15°, 15°, 30°, 30°, 15°, 15°, and 30°. The relative azimuth angles (RB) with respect to the omnidirectional beacon station at these multiple rotation angles are 0°, 30°, 45°, 60°, 90°, 120°, 135°, and 1... 50°, 180°, 210°, 225°, 240°, 270°, 300°, 315°, 330°, 360°; simultaneously, the relative azimuth angle RB′ of the radio compass corresponding to the aircraft rotating sequentially by 30°, 15°, 15°, 30°, 30°, 15°, 15°, 30°, 30°, 15°, 15°, 30°, 30°, 15°, 15°, 30°, 15°, 30°, 15°, 30°, 15°, 30°, 15°, 30°, 15°, 30° is read out through the display control system.

8. The method for calibrating compass error of a large amphibious aircraft radio compass according to claim 7, characterized in that, In step 8, the differences between the relative azimuth angles RB′ obtained from the radio compass when the relative azimuth angles RB are 0°, 30°, 45°, 60°, 90°, 120°, 135°, 150°, 180°, 210°, 225°, 240°, 270°, 300°, 315°, 330°, and 360° respectively, and the differences between these values ​​and the differences between the relative azimuth angles RB′ obtained from the aircraft rotating 30°, 15°, 15°, 30°, 30°, 15°, 15°, 30°, 30°, 15°, 15°, 30°, 30°, 15°, 15°, 30°, 15°, 15°, and 30° respectively, are calculated to obtain multiple quadrant error corrections (QECs).

9. The method for calibrating compass error of a large amphibious aircraft radio compass according to claim 8, characterized in that, In step 9, the plotted "QEC-RB" curve has RB as the horizontal axis and QEC as the vertical axis, and the curve approximates a sine / cosine curve.

10. The method for calibrating compass error of a large amphibious aircraft radio compass according to claim 9, characterized in that, In step 10, the compass alignment requirement for large amphibious aircraft is 25°. The two sets of radio compasses are re-aligned, that is, pins 40, 46, and 47 of the two sets of radio compasses are grounded and the remaining pins are left empty. Step 11 specifically involves restarting the aircraft from the 0° line, rotating it sequentially according to the inertial magnetic heading, 45° each time, for a total of 7 rotations. The relative azimuth angles RB relative to the omnidirectional beacon station are 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°, respectively. The relative azimuth angles RB′ of each rotation angle are then read out by the display and control system. This process is completed two hours before sunset. The QEC calculation was performed again, and the result was between -3° and +3°. The quadrant error correction QEC was then corrected.

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