A method of accelerated stall flight testing

Abstract

A method of accelerated stall flight test comprising a deceleration rate build-up step of increasing a deceleration rate of an aircraft to a target deceleration rate, an overload build-up step of increasing an overload of the aircraft to a target overload, and a stall trigger step of decelerating the aircraft at the target deceleration rate, the overload build-up step starting after and ending before the deceleration rate build-up step and running in parallel with the deceleration rate build-up step.

Description

Technical Field

[0001] This invention relates to a method for test flight of an aircraft with acceleration and stall. Background Technology

[0002] An aircraft stall occurs when the angle of attack (angle of attack) between the aircraft's wing and the airflow exceeds a critical value, causing the airflow to separate into laminar and turbulent flow over the wing's upper surface, resulting in a sharp decrease in lift. A stall causes the aircraft to descend rapidly, posing a significant threat to flight safety. Therefore, operating systems on aircraft such as civil aircraft typically include stall warning systems. These systems provide visual and auditory warnings to the pilots when the aircraft is approaching a stall, prompting them to take timely counter-stall maneuvers.

[0003] The proper functioning of the aforementioned stall warning system is crucial for aircraft flight safety. Therefore, during aircraft test flights, it is often necessary to test the stall warning system. Specifically, this involves first conducting stall characteristic test flights to assess the aircraft's stall characteristics, then designing the stall warning system based on the data obtained from these tests, and finally testing its functionality by having the pilot manipulate the aircraft to trigger a stall during stall warning test flights.

[0004] Currently, in the aforementioned stall characteristic test flights and stall warning test flights, accelerated stall test flights are often used to test the aircraft's stall characteristics and the effectiveness of the aircraft's stall warning system. Here, "accelerated" in "accelerated stall" does not refer to an increase in aircraft speed, but rather to an increase in the aircraft's load factor (hereinafter sometimes referred to as overload), i.e., an increase in acceleration.

[0005] To conduct accelerated stall test flights, the current main method involves "first entering a high-G maneuver state through steep turns, and then continuously increasing the aircraft's angle of attack and decelerating while maintaining stick control until a stall is triggered." However, continuously maintaining stick control and decelerating under high-G maneuver conditions is quite difficult; therefore, the success rate of accelerated stall test flights is generally not high. Summary of the Invention

[0006] This invention was made in view of the above-mentioned problems, and its purpose is to provide an accelerated flight test method with a high success rate.

[0007] To achieve the above objectives, the present invention provides an accelerated flight test method, which includes: a deceleration rate establishment step of increasing the deceleration rate of the aircraft to a target deceleration rate; an overload establishment step of increasing the overload of the aircraft to a target overload; and a stall triggering step of decelerating the aircraft at the target deceleration rate, wherein the overload establishment step begins after the deceleration rate establishment step but before its end and is performed in parallel with the deceleration rate establishment step.

[0008] According to the accelerated stall test method of the present invention, the overload establishment begins after the deceleration rate establishment starts but before it ends (i.e., before reaching the target deceleration rate), thereby enabling high-overload maneuvers to begin under the inertia of the deceleration state. Compared with the conventional accelerated stall test method that establishes overload first and then deceleration rate, the operational difficulty is reduced, and it avoids the failure of stick deceleration operations caused by the difficulty in controlling the aircraft during high-overload maneuvers such as turns. This effectively improves the success rate of accelerated stall test flights, thereby reducing the cost of the test flight project. Furthermore, since the deceleration rate establishment and overload establishment are carried out in parallel after a certain period of time in the deceleration rate establishment step, the waiting time in the test flight process is shortened, and the efficiency of the test flight is improved.

[0009] Furthermore, in the accelerated stall test flight method of the present invention, it is preferable that the stall triggering step is performed after the deceleration rate establishment step and the overload establishment step.

[0010] Therefore, it is possible to decelerate after reaching the target deceleration rate and target overload to trigger a stall or reach near the stall threshold, thus improving the success rate of test flights.

[0011] Furthermore, in the accelerated stall test flight method of the present invention, it is preferred that the target overload is greater than 1G.

[0012] Furthermore, in the accelerated stall test flight method of the present invention, it is preferable that, in the overload establishment step, the aircraft is made to turn at a bank angle of 30°.

[0013] Furthermore, in the accelerated stall test flight method of the present invention, it is preferred that the target overload is 1.5G in the overload establishment step.

[0014] Furthermore, in the accelerated stall test flight method of the present invention, it is preferable to further include an acceleration step that increases the speed of the aircraft before the deceleration rate establishment step.

[0015] This provides a range for establishing the deceleration rate, preventing the stall speed from being reached during the deceleration rate establishment process and improving the success rate of flight tests.

[0016] Furthermore, in the accelerated stall test flight method of the present invention, it is preferred to include a trim step before the acceleration step, in which the aircraft flies horizontally at a speed greater than the reference stall speed.

[0017] Furthermore, in the accelerated stall test flight method of the present invention, it is preferred that, before the trim step, the method further includes: a step of completing pre-test flight preparation work; a step of training on the aircraft simulator; and a step of setting different stall protection angles of attack on the aircraft and conducting test flights.

[0018] Therefore, by preparing for the test flight and getting the pilots used to the test flight procedures, the success rate of the test flight can be improved.

[0019] (Invention Effects)

[0020] According to the accelerated stall test method of the present invention, the overload establishment begins after the deceleration rate establishment starts but before it ends (i.e., before reaching the target deceleration rate), thereby enabling high-overload maneuvers to begin under the inertia of deceleration. Compared with the conventional method of establishing overload first and then deceleration rate, the implementation difficulty of high-overload maneuvers such as turns under deceleration inertia is lower, thus avoiding the failure of stick deceleration operations due to the difficulty in controlling the aircraft during, for example, turns. This effectively improves the success rate of accelerated stall test flights, reduces the number of test flights, and thus reduces the cost of the test flight program. Furthermore, since the deceleration rate establishment and overload establishment are carried out in parallel after a certain period of time in the deceleration rate establishment step, the waiting time in the test flight process is shortened, improving the efficiency of the test flight. In addition, by accelerating before establishing the deceleration rate, the stall speed is avoided before the overload establishment is completed, improving the success rate of the test flight. Moreover, by carrying out pre-test preparation work and familiarizing oneself with the test flight process, the success rate of the actual test flight is effectively improved. Attached Figure Description

[0021] Figure 1 This is a general flowchart of the accelerated stall test flight method for the implementation method.

[0022] Figure 2 yes Figure 1 The flowchart for step S2 in the process.

[0023] Figure 3 yes Figure 1 The flowchart for step S3 in the process.

[0024] Figure 4 yes Figure 1 The flowchart for step S4 in the process. Detailed Implementation

[0025] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0026] like Figure 1 As shown, the accelerated stall test flight method of this embodiment mainly includes four steps: S1 to S4.

[0027] In step S1, preparations are made for the accelerated stall test flight to ensure that the basic performance of the aircraft meets the test flight requirements.

[0028] Specifically, the pre-flight preparations in step S1 include: engine in-flight start-up test, high-angle maneuver test, low-speed handling stability check, and drift landing procedure rehearsal.

[0029] In step S2, the relevant test pilots practice test flight maneuvers, crew assignments, and stall recovery maneuvers on the simulator. It should be understood that the term "aircraft" in the following description of step S2 refers to a training simulator that can respond to pilot operations on the ground and simulate the flight conditions of a real aircraft.

[0030] Specifically, such as Figure 2 As shown, step S2 includes the following steps S21 to S25.

[0031] In step S21, deceleration rate control training under wing level conditions is conducted. In this training, while maintaining level flight (bank angle of 0°), the pilot establishes a deceleration rate by increasing the angle of attack by pulling the stick or adjusting the throttle. Establishing a deceleration rate refers to the process of gradually increasing the deceleration rate from 0 kN / s until a specified target deceleration rate (e.g., 3 kN / s) is reached.

[0032] In step S22, deceleration rate control training is performed under fixed overload / gradient conditions.

[0033] Here, overload and the aforementioned load factor are essentially the same concept, both referring to the ratio of the total external forces acting on the aircraft (specifically lift) to gravity. It reflects the aircraft's acceleration state during maneuvering and is quantified using gravitational acceleration (G). For example, in level flight, the lift acting on the aircraft equals gravity, resulting in an overload of 1G. However, when lift is greater than gravity (e.g., during turns or climbs), the overload is greater than 1G.

[0034] Bank angle refers to the angle at which an aircraft tilts its fuselage around its longitudinal axis (front-to-back axis) when turning. The centripetal force required for an aircraft to turn is provided by the horizontal component of the lift force acting on the tilted wings, while the vertical component of the lift force is used to balance gravity. Therefore, the overload during an aircraft turn is usually greater than 1G, and the greater the angle of wing tilt (i.e., bank angle), the greater the lift required to maintain the turn, and the greater the overload.

[0035] Furthermore, the aircraft's bank angle can gradually increase from level flight (where the bank angle is 0°) as it turns, and remain constant once it enters a stable turn. The process of controlling the increase of the aircraft's bank angle to reach a predetermined bank angle will be referred to as bank establishment.

[0036] Therefore, in step S22, the pilot can turn the aircraft and eventually maintain a fixed bank angle, or turn the aircraft and maintain a specific bank angle to achieve a fixed overload, and then control the aircraft's deceleration rate while maintaining a fixed bank angle or overload.

[0037] In step S23, a test flight maneuver training is conducted that involves increasing the bank angle while decelerating. In this training, the pilot first establishes a deceleration rate (i.e., gradually increasing the deceleration rate from 0 km / s) through the training content in step S21, and after the process of establishing the deceleration rate begins, the bank angle is established while continuing to increase the deceleration rate, that is, the bank angle is increased while the deceleration rate is increased.

[0038] In step S24, stall recovery maneuver training is conducted. Stall recovery refers to the process of maneuvering the aircraft to escape a stall state by reducing the angle of attack, for example. In this training, the pilot, for example, induces a stall state based on the training content of steps S21-23 above, and then uses appropriate maneuvers to extricate the aircraft from the stall state.

[0039] In step S25, the crew members involved in the stall test flight, including the pilots, undergo division of labor training. The division of labor includes, for example, aircraft operation, checking system operation status, parameter monitoring, data recording, and executing emergency plans.

[0040] After completing step S2 on the simulator, proceed to step S3. In step S3, conduct test flights step by step on the aircraft being tested by adjusting the stall protection angle of attack.

[0041] Specifically, such as Figure 3 As shown, step S3 includes the following steps S31 and S32.

[0042] In step S31, a test flight is performed while reducing the stall protection angle of attack. The stall protection angle of attack is a threshold angle of attack set in the aircraft control system. When the aircraft angle of attack approaches or exceeds the stall protection angle of attack, the stall protection system will automatically perform operations such as pushing the stick to reduce the angle of attack, so as to prevent the aircraft from triggering a stall or to relieve the stall state when it has already stalled.

[0043] In step S31, the stall protection angle of attack in the control system is set to a smaller angle than the stall protection angle of attack during the final accelerated stall test flight (hereinafter also referred to as the target value of the stall protection angle of attack). For example, if the target value of the stall protection angle of attack is 20°, the stall protection angle of attack is set to 18° in step S31. Then, during the test flight, by operating the training content described in step S21 above, the aircraft is pulled on the stick in level flight to establish and maintain a certain rate of deceleration until the aircraft angle of attack reaches 18°, thereby verifying whether the aircraft's stall protection function (e.g., automatic stick push) is functioning properly.

[0044] Next, in step S32, a test flight is performed while gradually adjusting the stall protection angle of attack to the target value. Specifically, in step S32, starting from 18°, the stall protection angle of attack is gradually adjusted in the order of, for example, 18.5°, 19°, 19.5°, and 20°. For each set stall protection angle of attack, the test flight action in step S31 is performed, and the effectiveness of the stall protection function when the angle of attack reaches the set stall protection angle of attack is verified.

[0045] Through the aforementioned steps S31 and S32, it is possible to verify whether the stall protection function of the aircraft undergoing test flights is functioning properly within the angle of attack range (e.g., 18°–20°) that is prone to triggering stall, thereby improving the safety of subsequent acceleration-stall test flights. Furthermore, pilots can become familiar with the operation of the test aircraft through multiple test flights, thus minimizing the possibility of failure in acceleration-stall test flights due to unfamiliarity with the controls.

[0046] After completing the test flight maneuver in step S3, proceed to step S4 to perform an accelerated stall test flight. Here, the accelerated stall test flight is actually applied to the aforementioned stall characteristic test flight and stall warning test flight.

[0047] Specifically, such as Figure 4 As shown, step S4 includes the following steps S41 to S45.

[0048] In step S41, the pilot trims the aircraft at the target trim speed. This target trim speed is set to different values ​​depending on the actual flight test. Specifically, it is set to 1.1–1.3 Vsr in stall characteristic flight tests and 1.3 Vsr in stall warning flight tests. Vsr is the reference stall speed, which is the calibrated airspeed at which the wing airflow begins to separate and cause the aircraft to lose altitude when it is in level flight (i.e., at 1G overload). Step S41 brings the aircraft into a stable level flight state.

[0049] Next, in step S42, while keeping the aircraft trim (level flight) state unchanged, the speed is increased by approximately 30 knots. Here, the purpose of increasing the speed is to provide a range for establishing the deceleration rate in the subsequent steps.

[0050] Specifically, the process of establishing the deceleration rate takes time, during which the aircraft is continuously decelerating. Therefore, if the deceleration rate is established directly from the target trim speed, the aircraft may decelerate to near the stall speed before reaching the target deceleration rate, potentially preventing the test flight from being completed completely. Thus, increasing the speed before establishing the deceleration rate can improve the success rate of the test flight.

[0051] In addition, the aforementioned acceleration process can provide additional kinetic energy reserves, ensuring sufficient altitude or speed margin to cope with unexpected situations during subsequent deceleration. Furthermore, acceleration can reduce attitude fluctuations when decelerating from level flight.

[0052] Next, in step S43, while keeping the wing level, the pitch angle is increased using the stick to begin establishing the deceleration rate. Here, in the case of stall characteristic test flight, the deceleration rate establishment process, for example, starts from 0 kN / s and increases the deceleration rate until it reaches 3 kN / s, while in the case of stall warning test flight, the deceleration rate establishment process, for example, starts from 0 kN / s and increases the deceleration rate until it reaches 2 kN / s.

[0053] In step S44, the aircraft is turned to establish a bank angle or overload. Here, step S44 and step S43 are executed in parallel.

[0054] Specifically, in step S44, after the increase in deceleration rate in step S43 but before reaching the target deceleration rate, the aircraft begins to turn to establish bank angle or overload. Here, the start time of establishing bank angle is slightly later than the start time of establishing deceleration rate in step S43, that is, the establishment of bank angle or overload begins when the aircraft has already decelerated. Therefore, it is possible to start turning to establish bank angle or overload while the aircraft is already decelerating, allowing the aircraft to utilize the inertia of deceleration while turning. Compared to starting to establish deceleration rate after turning, this avoids the difficulty of stick control during turning and makes it easier to increase and ultimately maintain the target deceleration rate.

[0055] Furthermore, preferably, the deceleration rate reaches the target deceleration rate as a result of establishing the bank angle or overload, while simultaneously achieving the target deceleration rate as a result of establishing the deceleration rate. This facilitates continuous operation with a consistent feel until both steps are completed, improving the success rate of the operation. At the same time, it reduces the waiting time before subsequent steps, which helps to shorten the flight test process and improve flight test efficiency.

[0056] In addition, regarding the aforementioned target bank angle and overload, a bank angle of 30° needs to be established during stall characteristic test flights, while an overload of 1.5G needs to be established during stall warning test flights, and the bank angle required to establish this overload is approximately 47°.

[0057] Finally, in step S45, while maintaining the bank angle or overload established in step S44, the aircraft continues to decelerate at the deceleration rate established in step S43. Here, in the stall characteristic test flight, the aircraft continues to decelerate until a stall is triggered, and triggers a stall protection function such as an automatic stick push, thereby restoring the aircraft to level flight. In the stall warning test flight, the aircraft continues to decelerate until a stall warning is triggered, and after the warning lasts for 1 second, the pilot performs a stall recovery to restore the aircraft to a stable level flight.

[0058] (Main effects of this implementation method)

[0059] According to the accelerated stall test method of this embodiment, the step of establishing overload (S44) begins slightly later than the step of establishing deceleration rate (S43), thereby enabling high-overload maneuvers to begin under the inertia of deceleration. Compared with the conventional method of establishing overload first and then establishing deceleration rate, the implementation difficulty of high-overload maneuvers such as turns under deceleration inertia is lower, thus avoiding the failure of deceleration operations due to the difficulty in controlling the aircraft during, for example, turns. This effectively improves the success rate of accelerated stall test flights, reduces the number of test flights, and thus reduces the cost of the test flight program. Furthermore, since the establishment of deceleration rate can be carried out in parallel with the establishment of overload and end simultaneously, the waiting time in the test flight process is reduced, improving the efficiency of the test flight. In addition, by accelerating before establishing deceleration rate, the stall speed is avoided before the establishment of overload is completed, improving the success rate of the test flight. Moreover, by carrying out pre-test preparation work and familiarizing oneself with the test flight process, the success rate of the actual test flight is effectively improved.

[0060] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above embodiments.

[0061] For example, in the above embodiments, the deceleration rate established during stall characteristic flight tests and stall warning flight tests has been described, but the established deceleration rate is not limited to this. For example, the deceleration rate established during stall characteristic flight tests may be slightly greater than 3 kN / s, and the deceleration rate established during stall warning flight tests may be greater than 2 kN / s. In this case, the deceleration rate is preferably slightly greater than 2 kN / s.

[0062] Furthermore, in the above embodiment, the speed was increased by 30 kN / s in step S42 before the deceleration rate was established in step S43. However, the speed increase is not limited to this. It can be adjusted according to the actual aircraft characteristics and the pilot's operating habits. For example, it can be 20 kN / s to 30 kN / s, or less than 20 kN / s.

[0063] Furthermore, in the above embodiment, the example given is that step S44 begins slightly later than step S43, but this is not a limitation. For example, step S44 can begin as soon as the deceleration rate is established in step S43, and it can be specifically adjusted according to the actual flight test situation, such as starting step S44 when the aircraft already has a clear deceleration trend. In addition, step S44 can also begin almost simultaneously with step S43.

[0064] Furthermore, in the above embodiment, the example given is that the processes of establishing the deceleration rate in step S43 and establishing the slope or overload in step S44 are completed simultaneously, but this is not a limitation. For example, either the establishment of the deceleration rate in step S43 or the establishment of the slope or overload in step S44 may be completed before the other. In this case, it is preferable that the interval between the completion times of the two is small.

[0065] It should be understood that within the scope of this invention, the various parts of the embodiments can be freely combined, or the various parts of the embodiments can be appropriately modified or omitted.

Claims

1. A method for accelerated stall test flights, characterized in that, include: Steps for establishing a deceleration rate that increases the aircraft's deceleration rate to the target deceleration rate; Overload establishment steps to increase the overload of the aircraft to the target overload; as well as The stall triggering step that causes the aircraft to decelerate at the target deceleration rate. The overload establishment step begins after the deceleration rate establishment step starts but before it ends, and runs in parallel with the deceleration rate establishment step.

2. The acceleration stall test flight method as described in claim 1, characterized in that, The stall triggering step is performed after the deceleration rate establishment step and the overload establishment step.

3. The acceleration-stall test flight method as described in claim 2, characterized in that, The target overload is greater than 1G.

4. The acceleration stall test flight method as described in claim 3, characterized in that, In the overload establishment step, the aircraft is made to turn at a bank angle of 30°.

5. The acceleration stall test flight method as described in claim 3, characterized in that, In the overload establishment step, the target overload is 1.5G.

6. The acceleration stall test flight method as described in any one of claims 1 to 5, characterized in that, Also includes: Before the deceleration rate establishment step, there is an acceleration step that increases the speed of the aircraft.

7. The acceleration stall test flight method as described in claim 6, characterized in that, Also includes: Prior to the acceleration step, a trim step is performed to make the aircraft fly horizontally at a speed greater than the reference stall speed.

8. The acceleration stall test flight method as described in claim 7, characterized in that, The following steps are included before the balancing step: Steps for completing pre-flight preparations; The steps of training on the aircraft simulator; and The procedure involves setting different stall protection angles on the aircraft and conducting test flights.

9. The acceleration stall test flight method as described in claim 4, characterized in that, The accelerated stall test method is used for stall characteristic test flights of the aircraft.

Images