A stall flight test method for fly-by-wire civil aircraft based on high angle of attack protection function
By using reasonable mission planning and flight test maneuver criteria, and by employing auxiliary and normal control laws, the stall envelope of a fly-by-wire civil aircraft with high angle-of-attack protection was determined. This resolved the flight test risks of aircraft with high angle-of-attack protection under high vibration characteristics, and enabled safe and efficient stall flight tests.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINESE FLIGHT TEST ESTAB
- Filing Date
- 2022-12-14
- Publication Date
- 2026-06-09
AI Technical Summary
Existing technologies make it difficult to safely and effectively test the stall envelope in fly-by-wire civil aircraft with high angle-of-attack protection, especially under high vibration characteristics, which poses risks to flight testing and unpredictable aerodynamic flutter problems.
Through reasonable mission planning, flight test action criteria, and data processing, and by using auxiliary control laws and normal control laws, the protection angle and maximum angle of attack of the high angle of attack protection function are gradually determined to ensure safe stall characteristic flight testing under high vibration characteristics and to verify stall characteristics under various scenarios.
It enables the safe and effective testing of an aircraft's stall envelope under high vibration conditions, reasonably avoids flight test risks, improves flight test efficiency, provides reliable risk prevention suggestions, and ensures aircraft safety and performance.
Smart Images
Figure CN115924103B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to, but is not limited to, the fields of thrust characteristic evaluation and flight test technology, and particularly to a fly-by-wire civil aircraft stall test method based on high angle-of-attack protection function.
[0002] This method is applicable to stall test flights of fly-by-wire civil aircraft with high angle-of-attack protection and high aerodynamic vibration characteristics before the peak of lift. Background Technology
[0003] Many civilian transport aircraft now incorporate fly-by-wire control systems, which offer excellent maneuverability and stability, significantly reducing pilot workload. Furthermore, the aircraft features high angle-of-attack protection, mitigating the risks of overspeed and stall. Through simulated flight tests and adjustments of various flight scenarios, fly-by-wire civilian aircraft can safely recover and resume normal flight even when entering a stall at low speeds or due to misoperation.
[0004] Fly-by-wire civil aircraft load important envelope protection functions into the flight control computer to prevent the aircraft from accidentally entering a stall state. This requires that during flight testing, the aircraft's true stall angle of attack must be determined to find a suitable envelope protection angle of attack to ensure the aircraft's reasonable performance and safety. Summary of the Invention
[0005] The purpose of this invention is to provide a stall test method for fly-by-wire civil aircraft based on high angle-of-attack protection. Through reasonable mission planning, test flight action criteria, and data processing, the stall envelope of the aircraft can be safely and effectively tested under high vibration characteristics.
[0006] The technical solution of the present invention: The embodiments of the present invention provide a method for stall test flight of a fly-by-wire civil aircraft based on high angle-of-attack protection, comprising:
[0007] Step 1: Complete the pre-flight preparations;
[0008] Step 2: Conduct stall characteristic test flight verification under auxiliary control law to preliminarily confirm the protection angle and maximum angle of attack of high angle of attack protection for fly-by-wire civil aircraft;
[0009] Step 3: Conduct stall characteristic test flight verification under normal control law. By loading the protection angle and maximum angle of attack of the high angle of attack protection determined in Step 2, determine the angle of attack operating range of the high angle of attack protection.
[0010] Step 4: Conduct stall characteristic test flights to verify the fly-by-wire civil aircraft in various scenarios;
[0011] Step 5: Conduct a stall characteristic test flight to verify the stall characteristics under angle of attack overshoot conditions.
[0012] Optionally, in the above-described fly-by-wire civil aircraft stall test method based on high angle-of-attack protection function,
[0013] The pre-flight preparations mentioned in step 1 include: engine in-flight start-up test, emergency power supply function test, high-angle maneuver test, low-speed handling stability check, auxiliary recovery device test, and simulator training.
[0014] Optionally, in the fly-by-wire civil aircraft stall test method based on high angle-of-attack protection function as described above, step 2 includes:
[0015] Step 21: Through the auxiliary control law, the control surfaces are directly commanded by the control stick, giving fly-by-wire civil aircraft high maneuverability and functional capabilities;
[0016] Step 22: By manipulating the control stick, gradually expand the aircraft's angle of attack from the center of gravity of medium weight towards the boundary line, and preliminarily confirm the protection angle of attack and the maximum angle of attack of the fly-by-wire civil aircraft for high angle of attack protection.
[0017] Optionally, in the above-described fly-by-wire civil aircraft stall test method based on high angle-of-attack protection function,
[0018] In the aforementioned steps, during the operation under the auxiliary control law, the lever is stabilized and corrected in time before the force of the lever approaches unacceptable severe vibration.
[0019] Optionally, in the fly-by-wire civil aircraft stall test method based on high angle-of-attack protection function as described above, step 3 includes:
[0020] Step 31: Under normal control law, control joystick command overload, and on this basis, apply the protection angle of attack and maximum angle of attack of the high angle of attack protection determined in step 2;
[0021] Step 32: By manipulating the normal control law and taking into account the vibration of the fly-by-wire civil aircraft during actual flight tests, adjust the protection angle and maximum angle of attack of the high angle of attack protection function of the fly-by-wire civil aircraft.
[0022] Step 33 verifies the aircraft stall characteristics, handling characteristics, and lift coefficient under normal control law, and finally determines the angle of attack operating range of high angle of attack protection.
[0023] Optionally, in the above-described fly-by-wire civil aircraft stall test method based on high angle-of-attack protection function,
[0024] During the execution of step 3, when determining the maximum angle of attack value for high angle of attack protection, the aircraft is most prone to dangerous high vibration characteristics.
[0025] Optionally, in the fly-by-wire civil aircraft stall test flight method based on high angle-of-attack protection function as described above, step 4 includes:
[0026] Based on the angle-of-attack operating range of the high angle-of-attack protection function determined in step 3 above, stall verification test flights are conducted for various flight scenarios to ensure that the aircraft no longer exhibits high vibration characteristics within the high angle-of-attack protection operating range.
[0027] Optionally, in the fly-by-wire civil aircraft stall test flight method based on high angle-of-attack protection function as described above, step 5 includes:
[0028] Under the normal control law with high angle of attack protection, the maximum angle of attack value of the right boundary is gradually shifted backward to ensure that even if a large angle of attack overshoot occurs during normal high angle of attack protection operation, the vibration of the aircraft will not exceed the unacceptable stopping flutter that occurred during the test in step 3.
[0029] Optionally, in the above-described fly-by-wire civil aircraft stall test method based on high angle-of-attack protection function,
[0030] During the stall test flight of the aforementioned fly-by-wire civil aircraft, the ability to identify risks is required, and corresponding risk mitigation measures must be provided.
[0031] The beneficial effects of this invention are as follows: This invention provides a stall test flight method for fly-by-wire civil aircraft based on high angle-of-attack protection. Specifically, it can reasonably avoid test flight risks, improve test flight efficiency, and determine the natural stall angle of attack, protection angle of attack, and maximum operating angle of attack for fly-by-wire civil aircraft with high angle-of-attack protection. In this test flight method, through reasonable mission planning, test flight action criteria, and data processing, it ensures that the aircraft's stall envelope can be safely and effectively tested under high vibration characteristics. The technical solution of this invention has the following beneficial effects:
[0032] (1) The technical solution of the present invention provides a stall test flight method for fly-by-wire civil aircraft under high vibration characteristics. The stall characteristics are tested under the auxiliary control law, normal control law and normal control law with high angle of attack protection function. This ensures that the true stall characteristics of the aircraft are explored before abnormal vibration occurs, and a reliable angle of attack protection function is established. The key points that need to be paid attention to during the stall test flight of fly-by-wire civil aircraft are given, as well as various risk prevention suggestions, which eliminate and prevent the possible dangers during the test flight to the greatest extent.
[0033] (2) The technical solution of the present invention can safely and effectively provide various data, personnel and technical support for the stall characteristics of fly-by-wire civil aircraft throughout the stall test flight stage, promote the safe and efficient stall test flight of fly-by-wire civil aircraft, and provide strong stall data support for the aircraft in the type qualification certification test flight. Attached Figure Description
[0034] The accompanying drawings are provided to further understand the technical solutions of the present invention and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of the present invention and do not constitute a limitation on the technical solutions of the present invention.
[0035] Figure 1 This is a flowchart of a fly-by-wire civil aircraft stall test flight method based on high angle-of-attack protection function, provided as an embodiment of the present invention. Detailed Implementation
[0036] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.
[0037] As explained in the background section, fly-by-wire civil aircraft load important envelope protection functions into their flight control computers to prevent the aircraft from accidentally entering a stall state. This requires that during flight testing, the aircraft's true stall angle of attack must be determined to find a suitable envelope protection angle of attack, ensuring the aircraft's reasonable performance and safety.
[0038] For fly-by-wire civil aircraft with high chattering stall characteristics, this invention provides a stall test method for fly-by-wire civil aircraft based on high angle of attack protection. Through reasonable mission planning, test flight action criteria, and data processing, the stall envelope of the aircraft can be safely and effectively tested under high vibration characteristics.
[0039] The present invention provides the following specific embodiments, which can be combined with each other. For the same or similar concepts or processes, they may not be described again in some embodiments.
[0040] This invention provides a stall test method for fly-by-wire civil aircraft based on high angle-of-attack protection. This method is applicable to stall test flights of fly-by-wire civil aircraft, which has high angle-of-attack protection and high aerodynamic vibration characteristics before the lift peak.
[0041] This invention provides a method for reasonably mitigating flight test risks, improving flight test efficiency, and determining the natural stall angle of attack, protection angle of attack, and maximum operating angle of attack for fly-by-wire civil aircraft with high angle-of-attack protection. For fly-by-wire civil aircraft with high angle-of-attack protection, the stall flight test regulations are as follows:
[0042] Stall tests of fly-by-wire civil aircraft involve many unforeseen circumstances, one of which is high vibration. When an aircraft approaches a stall, airflow separation occurs in the wings, causing aerodynamic flutter. For aircraft with such high flutter characteristics, the pilot will experience severe aerodynamic flutter as they pull the stick all the way back, making it impossible for them to control the aircraft or read the instruments. Continuing to pull the stick will exacerbate the airflow separation, leading the aircraft into an even more complex state.
[0043] Figure 1 This is a flowchart illustrating a stall test flight method for a fly-by-wire civil aircraft based on high angle-of-attack protection, provided by an embodiment of the present invention. The stall test flight method for a fly-by-wire civil aircraft based on high angle-of-attack protection, provided by an embodiment of the present invention, includes the following steps:
[0044] Step 1: Complete the preliminary preparations;
[0045] This step involves pre-flight preparations including: engine in-flight start-up test, emergency power supply function test, high-angle maneuver test, low-speed handling stability check, auxiliary recovery device test, simulator training, etc.
[0046] Step 2: Conduct stall characteristic test flights to verify the stall characteristics under the auxiliary control law;
[0047] Stall characteristics of a fly-by-wire civil aircraft were verified under an auxiliary control law. Through this law, the control surfaces are directly commanded from the control stick, demonstrating the aircraft's high maneuverability and operational capabilities. Based on this, the aircraft's angle of attack was gradually increased from the center of attack at medium weight towards the boundary line to explore the aircraft's stall characteristics. The protection angle and maximum angle of attack for high angle-of-attack protection of the fly-by-wire civil aircraft were preliminarily confirmed. It should be noted that under this auxiliary control law, the control stick force is relatively large; before approaching unacceptable severe vibrations, timely stick recovery is necessary.
[0048] Step 3: Conduct stall characteristic test flights under normal control law to determine the operating angle of attack range of high angle of attack protection;
[0049] Under normal control law, the control stick commands overload or other parameters are applied. Based on this, the protection angle and maximum angle of attack of the high angle of attack protection in step 2 are applied. Through normal control law manipulation, and combined with the vibration conditions of fly-by-wire civil aircraft during actual flight tests, the protection angle and maximum angle of attack of the high angle of attack protection function of the fly-by-wire civil aircraft are further adjusted. The aircraft stall characteristics, handling characteristics, and lift coefficient under normal control law are verified, and finally the operating angle of attack range of the high angle of attack protection is determined. When determining the maximum angle of attack value of the high angle of attack protection, the aircraft is most prone to dangerous high vibration characteristics.
[0050] Step 4: Conduct stall characteristic test flights to verify the fly-by-wire civil aircraft in various scenarios;
[0051] Based on the angle-of-attack operating range of the high angle-of-attack protection function determined in the previous steps, stall verification test flights were conducted for various flight scenarios to ensure that the aircraft no longer exhibits high vibration characteristics within the high angle-of-attack protection operating range, thereby achieving the goal of meeting the handling characteristics specified in the regulations.
[0052] Step 5: Conduct a stall characteristic test flight to verify the stall characteristics under angle-of-attack overshoot conditions;
[0053] After confirming the high angle of attack protection function, the stall characteristics were verified by flight testing. Under the normal control law with high angle of attack protection function, the maximum angle of attack value of the right boundary was gradually shifted backward to ensure that even if a large angle of attack overshoot occurs during normal high angle of attack protection operation, the vibration of the aircraft will not exceed the unacceptable stopping flutter that occurred during the test in step 3.
[0054] The stall test flight method for fly-by-wire civil aircraft based on high angle-of-attack protection provided by this invention specifically aims to reasonably avoid test flight risks, improve test flight efficiency, and determine the natural stall angle of attack, protection angle of attack, and maximum operating angle of attack for fly-by-wire civil aircraft with high angle-of-attack protection. In this test flight plan, through reasonable mission planning, test flight action criteria, and data processing, the stall envelope of the aircraft can be safely and effectively tested under high vibration characteristics. The technical solution of this invention has the following beneficial effects:
[0055] (1) The technical solution of the present invention provides a stall test flight method for fly-by-wire civil aircraft under high vibration characteristics. The stall characteristics are tested under the auxiliary control law, normal control law and normal control law with high angle of attack protection function. This ensures that the true stall characteristics of the aircraft are explored before abnormal vibration occurs, and a reliable angle of attack protection function is established. The key points that need to be paid attention to during the stall test flight of fly-by-wire civil aircraft are given, as well as various risk prevention suggestions, which eliminate and prevent the possible dangers during the test flight to the greatest extent.
[0056] (2) The technical solution of the present invention can safely and effectively provide various data, personnel and technical support for the stall characteristics of fly-by-wire civil aircraft throughout the stall test flight stage, promote the safe and efficient stall test flight of fly-by-wire civil aircraft, and provide strong stall data support for the aircraft in the type qualification certification test flight.
[0057] It should be noted that during stall tests of fly-by-wire civil aircraft, the airflow separation is unclear before the aircraft reaches its peak lift coefficient. The aircraft's response and vibration magnitude at the critical angle of attack are unknown, and there is a high possibility of unacceptable vibrations, wing loss, and nose-dropping stall phenomena occurring simultaneously. Therefore, during stall characteristic flight tests of fly-by-wire civil aircraft under these characteristics, it is necessary to identify flight test risks and provide mitigation measures. Specific risk identification and mitigation measures are as follows:
[0058] (1) Engine failure:
[0059] During high angle-of-attack test flights, the reduced engine air intake and excessive air intake angle can easily cause air intake distortion, leading to engine shutdown or other abnormal situations. During the test, it is necessary to use the continuous ignition function in a timely manner, monitor the engine's operating status in real time, and conduct the test in the airspace close to the landing airport to ensure that the aircraft can drift and land even in the event of dual engine failure.
[0060] (2) Aircraft out of control:
[0061] Unpredictable aerodynamic responses may occur during a stall, and the high angle-of-attack protection function may exhibit abnormal responses. Dangerous attitudes during stall entry and stall recovery may cause the airspeed system to malfunction. During testing, a gradual approach should be taken, with a thorough understanding of the stall characteristics of the test aircraft built upon prior performance assessments and simulator training. The airflow in the test area should be stable, the test maneuvers should be gentle, and changes in aircraft parameters should be closely monitored.
[0062] (3) Aircraft system failure:
[0063] Large attitudes, large angles of attack, and even large stall recovery maneuvers can cause abnormal operation of the aircraft's hydraulic, fuel, and pressurization systems. During the test, the monitoring of each system on the ground is increased, and the crew on board will conduct a cyclical check of the operation of each system after the test mission is completed. If any abnormality is found, the aircraft will return to the ground and land in time.
[0064] (4) Flight control system downgrade:
[0065] Flight control system downgrade. Due to the fault in Article (3), the flap / slat jamming failure may occur, which will cause the aircraft to be downgraded and the handling efficiency to be reduced. If such a situation is found during the test, the action should be stopped in time, the aircraft should be returned to the field in time, and the faulty configuration should be used for landing. When landing, pay attention to speed and weight limits.
[0066] The following is a specific implementation example illustrating the implementation method of the fly-by-wire civil aircraft stall test flight method based on high angle of attack protection provided by the present invention.
[0067] Implementation Example
[0068] Reference Figure 1The implementation example provides a fly-by-wire civil aircraft stall test method based on high angle-of-attack protection, which includes the following steps:
[0069] (1) Complete the preliminary preparations, including: engine in-flight start, emergency power function test, high-gradient maneuver, low-speed handling stability check, auxiliary recovery device test, simulator training, etc.
[0070] (2) Under the auxiliary control law, the aircraft’s stall characteristics were verified, and the protection angle and maximum angle of attack of the high angle of attack protection function were initially determined.
[0071] (3) Under normal control law, apply the protection angle and maximum angle of attack of the high angle of attack protection function, and gradually adjust the initially determined protection angle of attack and maximum angle of attack.
[0072] (4) After determining the protection angle and maximum angle of attack for high angle of attack protection, stall characteristic tests are conducted in various configurations and scenarios;
[0073] (5) Move the maximum working angle of attack backward to verify that when the stall angle of attack is overshooted, its highest vibration characteristics still meet the requirements of the regulations. The test ends.
[0074] While the embodiments disclosed in this invention are as described above, they are merely illustrative of the embodiments to facilitate understanding of the invention and are not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and variations in the form and details of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection for this invention shall still be determined by the scope defined in the appended claims.
Claims
1. A method for stall test flight of a fly-by-wire civil aircraft based on high angle-of-attack protection, characterized in that, include: Step 1: Complete the pre-flight preparations; Step 2: Conduct stall characteristic test flight verification under auxiliary control law to preliminarily confirm the protection angle and maximum angle of attack of high angle of attack protection for fly-by-wire civil aircraft; Step 3: Conduct stall characteristic test flight verification under normal control law. By loading the protection angle and maximum angle of attack of the high angle of attack protection determined in Step 2, determine the angle of attack operating range of the high angle of attack protection. Step 4: Conduct stall characteristic test flights to verify the fly-by-wire civil aircraft in various scenarios; Step 5: Conduct a stall characteristic test flight to verify the stall characteristics under angle-of-attack overshoot conditions; Step 2 includes: Step 21: Through the auxiliary control law, the control surfaces are directly commanded by the control stick, giving fly-by-wire civil aircraft high maneuverability and functional capabilities; Step 22: By controlling the control stick, gradually expand the aircraft's angle of attack from the center of gravity of medium weight towards the boundary line to initially confirm the protection angle of attack and the maximum angle of attack of the fly-by-wire civil aircraft's high angle of attack protection. Step 3 includes: Step 31: Under normal control law, control joystick command overload, and on this basis, apply the protection angle of attack and maximum angle of attack of the high angle of attack protection determined in step 2; Step 32: By manipulating the normal control law and taking into account the vibration of the fly-by-wire civil aircraft during actual flight tests, adjust the protection angle and maximum angle of attack of the high angle of attack protection function of the fly-by-wire civil aircraft. Step 33: Verify the aircraft stall characteristics, handling characteristics, and lift coefficient under normal control law, and finally determine the angle of attack operating range of high angle of attack protection. Step 5 includes: Under the normal control law with high angle of attack protection, the maximum angle of attack value of the right boundary is gradually shifted backward.
2. The fly-by-wire civil aircraft stall test method based on high angle-of-attack protection function according to claim 1, characterized in that, The pre-flight preparations mentioned in step 1 include: engine in-flight start-up test, emergency power supply function test, high-angle maneuver test, low-speed handling stability check, auxiliary recovery device test, and simulator training.
3. The fly-by-wire civil aircraft stall test method based on high angle-of-attack protection function according to claim 1, characterized in that, In step 3, during the operation under the auxiliary control law, the lever is stabilized and corrected in time before the force of the lever approaches unacceptable severe vibration.
4. The fly-by-wire civil aircraft stall test method based on high angle-of-attack protection function according to claim 1, characterized in that, During the execution of step 3, when determining the maximum angle of attack value for high angle of attack protection, the aircraft is most prone to dangerous high vibration characteristics.
5. The fly-by-wire civil aircraft stall test method based on high angle-of-attack protection function according to claim 1, characterized in that, Step 4 includes: Based on the angle-of-attack operating range of the high angle-of-attack protection function determined in step 3 above, stall verification test flights are conducted for various flight scenarios to ensure that the aircraft no longer exhibits high vibration characteristics within the high angle-of-attack protection operating range.
6. The fly-by-wire civil aircraft stall test method based on high angle-of-attack protection function according to any one of claims 1 to 5, characterized in that, During the stall test flight of the aforementioned fly-by-wire civil aircraft, the ability to identify risks is required, and corresponding risk mitigation measures must be provided.