A flight maneuver envelope design method for firefighting aircraft

Abstract

The present invention discloses a method for designing a flight maneuvering envelope of a fire-fighting aircraft. Based on the design characteristics and overall design requirements of the fire-fighting aircraft, the design flap speed VF under the fire-fighting mission is calculated and the design fire-fighting flight speed VFF is formulated; based on the terrain adaptability and flight safety of the use scenario, the maneuvering load factor n under the fire-fighting mission is calculated and formulated; based on VF, VFF and n, the flight maneuvering envelope is formulated and drawn. The present invention can obtain a reasonable flight maneuvering envelope of a fire-fighting aircraft, and provide a basis for aircraft load calculation, structural strength design analysis, use restriction formulation and flight manual compilation.

Description

Technical Field

[0001] The invention belongs to the technical field of aircraft load calculation design, and in particular relates to a flight maneuver envelope design method for a fire-fighting aircraft. Background Art

[0002] The aircraft flight maneuvering envelope is a two-dimensional envelope, with the horizontal axis being the equivalent airspeed V and the vertical axis being the maneuvering load coefficient n, so it is also called the Vn envelope. Generally, aircraft mainly calculate the design airspeed and the limited maneuvering load coefficient based on the requirements of airworthiness regulations or national military standards, combined with parameters such as aircraft weight, configuration, maximum aerodynamic normal force coefficient, and use altitude, so as to design the aircraft flight maneuvering envelope. Firefighting aircraft have the use modes of low-altitude fire scene reconnaissance and water-dropping firefighting. The mission environment, especially the terrain, is complex and changeable. Aircraft designers must reasonably formulate the aircraft flight maneuvering envelope based on these use modes, and use it as the basis for aircraft load calculation, structural strength design analysis, use restriction formulation, and flight manual compilation. At present, there are two main methods for designing the flight maneuvering envelope of firefighting aircraft: one is to directly use the requirements of airworthiness regulations or national military standards. This method has a greater limit on the maneuverability of firefighting aircraft when performing water-dropping firefighting tasks; the other is to determine it based on the extreme value of the aircraft's aerodynamic normal force. This method has higher requirements on the structural strength of the firefighting aircraft's fuselage, and usually requires a greater structural weight cost. Summary of the invention

[0003] The purpose of the present invention is to provide a method for designing the flight maneuvering envelope of a fire-fighting aircraft. The present invention can obtain a reasonable flight maneuvering envelope of a fire-fighting aircraft, and provide a basis for aircraft load calculation, structural strength design analysis, use restriction formulation and flight manual compilation.

[0004] The technical solution of the present invention is: a method for designing the flight maneuver envelope of a fire-fighting aircraft, based on the design characteristics and overall design requirements of the fire-fighting aircraft, calculates the design flap speed V under the fire-fighting mission F And formulate the design firefighting flight speed V FF ; Based on the terrain adaptability and flight safety of the use scenario, calculate and formulate the maneuvering load factor n under the fire-fighting mission; based on V F 、V FF and n, develop and plot the flight maneuvering envelope.

[0005] The aforementioned method for designing the flight maneuver envelope of the fire-fighting aircraft comprises the following steps:

[0006] (1) Based on the design weight of the firefighting aircraft, the flap deflection for firefighting missions and its stall speed V S1 , calculate the design flap speed V F ;

[0007] (2) Based on the maximum water-dropping airspeed V specified in the overall design requirements for firefighting aircraft MX and design flap speed V F , formulate the design firefighting flight speed V FF ;

[0008] (3) Based on the analysis of the use scenarios of firefighting aircraft, V FF As the design reference speed, calculate the maximum limiting maneuvering load factor n that meets different terrains and usage modes. max ;

[0009] (4) Calculate and formulate the minimum limiting maneuvering load factor n of the aircraft based on the flight safety analysis of the firefighting aircraft usage scenario min ;

[0010] (5) Based on the above V F 、V FF and n max 、n min , combined with the minimum water-dropping airspeed V specified in the overall design requirements MN , and the maximum static normal force coefficient C of the aircraft in the firefighting configuration NMAX , calculate and draw the flight maneuver envelope.

[0011] In the step (1) of the above-mentioned method for designing the flight maneuvering envelope of the fire-fighting aircraft, the aircraft design flap speed V F The calculation process is as follows: Based on the design weight of the firefighting aircraft, the flap deflection of the firefighting mission and its stall speed V S1 ; For firefighting missions, the flap deflection is 1.6V at the maximum design takeoff weight of the aircraft S1 and 1.8V at maximum weight after being submerged in water S1 Compare and take the larger one.

[0012] In step (2) of the aforementioned method for designing the flight maneuver envelope of a fire-fighting aircraft, the aircraft is designed to fly at a fire-fighting speed V FF Than the maximum water-dropping airspeed V specified in the overall design requirements of firefighting aircraft MX Large, with sufficient speed margin, and not exceeding V F .

[0013] In step (3) of the aforementioned method for designing the flight maneuvering envelope of a fire-fighting aircraft, the aircraft maximum limiting maneuvering load factor n max It is based on the use scenario analysis of firefighting aircraft, with V FF As the design reference speed, it is calculated to meet different terrains and usage modes.

[0014] In the aforementioned design method for the flight maneuvering envelope of a firefighting aircraft, the aircraft's maximum maneuvering load factor n maxMeet the minimum requirements for the maneuvering load factor n for executing hillside sliding, direct fire extinguishing, pulling up and disengaging, and hillside inclined turning and water dropping between specified valleys.

[0015] In step (4) of the aforementioned method for designing the flight maneuvering envelope of a fire-fighting aircraft, the aircraft minimum limiting maneuvering load factor n min The value of is as follows: According to the flight safety analysis of the firefighting aircraft usage scenario, in order to avoid unnecessary low-altitude collision risk, the minimum limit maneuvering load factor n is set. min is equal to zero.

[0016] In step (5) of the above-mentioned method for designing the flight maneuvering envelope of the fire-fighting aircraft, the horizontal axis speed range of the flight maneuvering envelope of the fire-fighting aircraft is the minimum water-dropping flight airspeed V specified in the overall design requirements. MN To the design flap speed V F The range of the maneuvering load factor n on the longitudinal axis is from the minimum limiting maneuvering load factor n min To the maximum limit maneuvering load factor n max ; The envelope boundary also includes V MN 、V MX 、V FF and V F Corresponding point.

[0017] The advantages of the present invention are as follows: based on the design characteristics and overall design requirements of the fire-fighting aircraft, the present invention calculates the design flap speed V under the fire-fighting mission. F And formulate the design firefighting flight speed V FF ; Based on the terrain adaptability and flight safety of the use scenario, calculate and formulate the maneuvering load factor n under the fire-fighting mission; based on V F 、V FF and n, formulate and draw the flight maneuvering envelope; it not only ensures the maneuverability of the fire-fighting aircraft when performing water-dropping fire-fighting tasks, but also does not bring about the unfavorable structural weight increase cost. It is easy to implement and is applicable to all newly developed or modified fire-fighting aircraft. It has been verified that under the same aircraft maneuverability requirements, the use of the present invention can reduce the structural weight of the aircraft by 2% to 3%, with significant weight reduction.

[0018] In summary, the present invention can obtain a reasonable flight maneuver envelope of a fire-fighting aircraft, and provide a basis for aircraft load calculation, structural strength design analysis, use restriction formulation, and flight manual compilation. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the flight maneuvering envelope of the fire-fighting aircraft described in the present invention. Figure 1 The horizontal axis V in the middle represents the equivalent airspeed in km / h; the vertical axis n represents the aircraft maneuvering load factor; point V MNIndicates the minimum water-dropping speed of the aircraft; point V MX Indicates the maximum water-dropping speed of the aircraft; V FF Indicates the designed fire-fighting flight speed; V AF Indicates the upper left corner boundary point of the envelope; V F Indicates the design flap speed for the fire-fighting mission configuration.

[0020] Figure 2 It is a schematic diagram of the use mode of the fire-fighting aircraft described in the present invention, namely, sliding down a hillside - directly extinguishing a fire - pulling up and disengaging. Figure 2 A and B represent two adjacent mountains; θ1 is the slope angle of the inner slope of mountain A; θ2 is the slope angle of the inner slope of mountain B; R represents the turning radius in the vertical plane when the firefighting aircraft performs the task of dropping water to extinguish fire between mountains A and B, in meters; H represents the vertical height of the slope corresponding to the aircraft's start of turning from the bottom of the valley, in meters; L represents the lateral distance from the bottom of the valley, in meters. The aircraft slides down from the top of mountain A along its inner slope, drops water above the fire point to extinguish the fire, and then performs a pull-up maneuver to leave the valley upward along the inner upslope of upper body B.

[0021] Figure 3 It is a schematic diagram of the use mode of the fire-fighting aircraft turning fire-fighting described in the present invention. Figure 3 R represents the turning radius of the aircraft, in meters; the circle points on the arc curve represent the points of the aircraft's motion trajectory. The aircraft enters from the opposite side of the fire point, performs a turn with a radius of R, and then flies above the fire point to drop water to extinguish the fire. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with the accompanying drawings and embodiments, but they are not intended to limit the present invention.

[0023] Embodiment 1. A method for designing a flight maneuver envelope of a firefighting aircraft, such as Figure 1-3 As shown in the figure, based on the design characteristics and overall design requirements of the fire-fighting aircraft, the design flap speed V under the fire-fighting mission is calculated. F And formulate the design firefighting flight speed V FF ; Based on the terrain adaptability and flight safety of the use scenario, calculate and formulate the maneuvering load factor n under the fire-fighting mission; based on V F 、V FF and n, formulate and draw the flight maneuver envelope. The specific steps are as follows:

[0024] (1) Based on the design weight of the firefighting aircraft, the flap deflection for firefighting missions and its stall speed V S1 , calculate the design flap speed V F , V F The flap deflection for firefighting mission should be 1.6V at the maximum design takeoff weight of the aircraft. S1and 1.8V at maximum weight after being submerged in water S1 the greater of

[0025] (2) Based on the maximum water-dropping airspeed V specified in the overall design requirements for firefighting aircraft MX and design flap speed V F , formulate the design firefighting flight speed V FF , V FF Should be compared to V MX Large and leave enough speed margin, and do not exceed V F ;

[0026] (3) Based on the analysis of the use scenarios of firefighting aircraft, V FF As the design reference speed, calculate the maximum limiting maneuvering load factor n that meets different terrains and usage modes. max , n max The minimum value requirement of the maneuvering load factor n for hillside sliding, direct fire extinguishing, pulling out and hillside tilt turning and water throwing between specified valleys shall be met;

[0027] (4) Based on the flight safety analysis of the firefighting aircraft’s use scenarios, in order to avoid unnecessary low-altitude collision risks, the minimum limiting maneuvering load factor n is specified. min is equal to zero;

[0028] (5) Based on the above design speed and load factor results, combined with the minimum water-dropping airspeed V specified in the overall design requirements MN , and the maximum static normal force coefficient C of the aircraft in the fire-fighting configuration NMAX , calculate and draw the flight maneuver envelope.

[0029] Example 2. For a certain type of aircraft, the flight maneuver envelope design method of the fire-fighting aircraft proposed in the present invention is used to design the flap speed V of the aircraft. F And formulate the design firefighting flight speed V FF , the limiting maneuvering load factor n and the flight maneuvering envelope are calculated and formulated as follows:

[0030] (1) The maximum takeoff weight of a certain type of firefighting aircraft is 60,000 kg. The maximum weight of the aircraft after dropping water is 57,400 kg. The flap deflection of the firefighting mission configuration is 17 degrees. After calculation, the corresponding maximum takeoff weight is 1.6V S1 Equal to 296km / h, corresponding to 1.8V of the maximum weight of the aircraft after dropping into water S1 =326km / h, so the design flap speed V is selected F Equal to 326km / h.

[0031] (2) According to the overall design requirements, the maximum water-dropping flight speed V of a certain type of firefighting aircraft MX=270km / h, so after taking a safety speed margin of 10 knots, the designed firefighting flight speed V FF Equal to 288.5km / h, V FF Lower than the V obtained in step (1) above F .

[0032] (3) For the attached Figure 2 The use mode of a certain type of firefighting aircraft shown in the figure is to slide down the hillside - directly extinguish the fire - pull up and detach. The maximum limited maneuvering load factor n of the aircraft adapted to this terrain max At least:

[0033]

[0034] In formula (1), g is the acceleration due to gravity; R is the turning radius.

[0035] (4) For the attached Figure 3 The use mode of a certain type of firefighting aircraft for firefighting on a hillside is shown in the figure. The aircraft's limited maneuvering load factor n that is suitable for this terrain max At least:

[0036]

[0037] In formula (2), is the aircraft's bank angle when turning, and V is the aircraft's real-time flight speed.

[0038] (5) Compare the n obtained in steps (3) and (4) above max , the larger one is taken as the maximum limiting maneuvering load factor of a certain type of firefighting aircraft;

[0039] (6) When a certain type of firefighting aircraft drops water to extinguish a fire, the height from the ground or treetops does not exceed 50m. In order to avoid the risk of losing altitude and crashing into the ground, no negative maneuvers are performed and the minimum limiting maneuvering load factor can be taken as zero.

[0040] (7) Minimum water-dropping flight speed V for a certain type of aircraft MN =230km / h. Combine the design airspeed and limited maneuvering load factor obtained in the above steps to draw the flight maneuvering envelope of a certain type of firefighting aircraft, as shown in the attached figure. Figure 1 shown.

[0041] The present invention provides a flight maneuver envelope design method for a fire-fighting aircraft. Based on the design characteristics and overall design requirements of the fire-fighting aircraft, the design flap speed V under the fire-fighting mission is calculated. F And formulate the design firefighting flight speed V FF ; Based on the terrain adaptability and flight safety of the use scenario, calculate and formulate the maneuvering load factor n under the fire-fighting mission; based on V F 、V FFand n, formulate and draw the flight maneuvering envelope; it not only ensures the maneuverability of the fire-fighting aircraft when performing water-dropping fire-fighting tasks but also does not bring about adverse structural weight gain costs.

[0042] Example 3. A method for designing the flight maneuver envelope of a firefighting aircraft, see Figure 1-Figure 3 , the design flap speed V for the aircraft fire extinguishing configuration F and the designed firefighting flight speed V FF , Maximum limit maneuvering load factor n max , minimum limiting maneuvering load factor n min etc. to carry out calculation and analysis, and formulate the Vn envelope of the aircraft fire extinguishing configuration.

[0043] The flight maneuver envelope design method of the fire-fighting aircraft comprises the following steps:

[0044] (1) Based on the design weight of the firefighting aircraft, the flap deflection for firefighting missions and its stall speed V S1 , calculate the design flap speed V F ;

[0045] (2) Based on the maximum water-dropping flight speed V specified in the overall design requirements for firefighting aircraft MX and design flap speed V F , formulate the design firefighting flight speed V FF ;

[0046] (3) Based on the analysis of the use scenarios of firefighting aircraft, V FF As the design reference speed, calculate the maximum limiting maneuvering load factor n that meets different terrains and usage modes. max ;

[0047] (4) Calculate and formulate the minimum limiting maneuvering load factor n of the aircraft based on the flight safety analysis of the firefighting aircraft usage scenario min ;

[0048] (5) Based on the above V F 、V FF and n max 、n min , combined with the minimum water-dropping airspeed V specified in the overall design requirements MN , and the maximum static normal force coefficient C of the aircraft in the firefighting configuration NMAX , calculate and draw the flight maneuver envelope, and provide a basis for aircraft load calculation, structural strength design and analysis, use restriction formulation and flight manual compilation.

[0049] Design flap speed V F When calculating, refer to the requirements of Article 25.335(e)(2) of Subpart C of the Civil Aviation Regulations of China Part 25, based on the flap deflection and stall speed VS1 , and consider the maximum weight of the aircraft before and after dropping water, and make a comprehensive calculation to determine it.

[0050] Designed fire-fighting flight speed V FF It should be consistent with the maximum water-dropping flight airspeed V specified in the overall design requirements. MX There should be enough safety margin, but it is not necessary to exceed the design flap speed V F .

[0051] Maximum limit maneuvering load factor n max It is calculated based on the water-dropping fire-fighting flight mode of the fire-fighting aircraft, combined with consideration of terrain adaptability.

[0052] Minimum limiting maneuvering load factor n min It is formulated based on the flight safety analysis under the use scenarios of firefighting aircraft.

[0053] The horizontal axis speed range of the firefighting aircraft flight maneuvering envelope is the minimum water-dropping flight airspeed V specified in the overall design requirements. MN To the design flap speed V F The maneuvering load factor range of the longitudinal axis is from the minimum limiting maneuvering load factor n min To the maximum limit maneuvering load factor n max , the envelope boundary should include V MN 、V MX 、V FF and V F Corresponding point.

[0054] Example 4. A method for designing the flight maneuver envelope of a firefighting aircraft, see Figure 1-3 , based on the design characteristics and overall design requirements of the firefighting aircraft, calculate the design flap speed V under the firefighting mission F And formulate the design firefighting flight speed V FF ; Based on the terrain adaptability and flight safety of the use scenario, calculate and formulate the maneuvering load factor n under the fire-fighting mission; based on V F 、V FF and n, develop and plot the flight maneuvering envelope.

[0055] The aforementioned method for designing the flight maneuver envelope of the fire-fighting aircraft comprises the following steps:

[0056] (1) Based on the design weight of the firefighting aircraft, the flap deflection for firefighting missions and its stall speed V S1 , calculate the design flap speed V F ;

[0057] (2) Based on the maximum water-dropping airspeed V specified in the overall design requirements for firefighting aircraft MX and design flap speed V F, formulate the design firefighting flight speed V FF ;

[0058] (3) Based on the analysis of the use scenarios of firefighting aircraft, V FF As the design reference speed, calculate the maximum limiting maneuvering load factor n that meets different terrains and usage modes. max ;

[0059] (4) Calculate and formulate the minimum limiting maneuvering load factor n of the aircraft based on the flight safety analysis of the firefighting aircraft usage scenario min ;

[0060] (5) Based on the above V F 、V FF and n max 、n min , combined with the minimum water-dropping airspeed V specified in the overall design requirements MN , and the maximum static normal force coefficient C of the aircraft in the fire-fighting configuration NMAX , calculate and draw the flight maneuver envelope.

[0061] In the above step (1), the aircraft design flap speed V F The calculation process is as follows: Based on the design weight of the firefighting aircraft, the flap deflection of the firefighting mission and its stall speed V S1 ; For firefighting missions, the flap deflection is 1.6V at the maximum design takeoff weight of the aircraft S1 and 1.8V at maximum weight after being submerged in water S1 Compare and take the larger one.

[0062] In the above step (2), the aircraft is designed to fly at a firefighting speed V FF Than the maximum water-dropping airspeed V specified in the overall design requirements of firefighting aircraft MX Large, with sufficient speed margin, and not exceeding V F .

[0063] In the above step (3), the maximum limiting maneuvering load factor of the aircraft n max It is based on the use scenario analysis of firefighting aircraft, with V FF As the design reference speed, it is calculated to meet different terrains and usage modes.

[0064] Aircraft maximum limited maneuvering load factor n max Meet the minimum requirements for the maneuvering load factor n for executing hillside sliding, direct fire extinguishing, pulling up and disengaging, and hillside inclined turning and water dropping between specified valleys.

[0065] In the above step (4), the aircraft minimum limiting maneuvering load factor n minThe value of is as follows: According to the flight safety analysis of the firefighting aircraft usage scenario, in order to avoid unnecessary low-altitude collision risk, the minimum limit maneuvering load factor n is set. min is equal to zero.

[0066] In the aforementioned step (5), the horizontal axis speed range of the fire-fighting aircraft flight maneuvering envelope is the minimum water-dropping flight airspeed V specified in the overall design requirements. MN To the design flap speed V F The range of the maneuvering load factor n on the longitudinal axis is from the minimum limiting maneuvering load factor n min To the maximum limit maneuvering load factor n max ; The envelope boundary also includes V MN 、V MX 、V FF and V F Corresponding point.

[0067] The above-mentioned embodiments only express the implementation mode of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for designing a flight maneuver envelope of a fire-fighting aircraft, characterized in that: Based on the design characteristics and overall design requirements of the firefighting aircraft, the design flap speed V under the firefighting mission is calculated. F And formulate the design firefighting flight speed V FF ; Based on the terrain adaptability and flight safety of the use scenario, calculate and formulate the maneuvering load factor n under the fire-fighting mission; based on V F 、V FF and n, formulate and draw the flight maneuver envelope; the steps are as follows: (1) Based on the design weight of the firefighting aircraft, the flap deflection for firefighting missions and its stall speed V S1 , calculate the design flap speed V F ; Aircraft design flap speed V F The calculation process is as follows: For the fire-fighting mission, the 1.6V at the maximum design takeoff weight of the aircraft under the flap deflection S1 and 1.8V at maximum weight after being submerged in water S1 Compare and take the larger one; (2) Based on the maximum water-dropping airspeed V specified in the overall design requirements for firefighting aircraft MX and design flap speed V F , formulate the design firefighting flight speed V FF ; Aircraft design firefighting flight speed V FF Than the maximum water-dropping airspeed V specified in the overall design requirements of firefighting aircraft MX Large, with sufficient speed margin, and not exceeding V F ; (3) Based on the analysis of the use scenarios of firefighting aircraft, V FF As the design reference speed, calculate the maximum limiting maneuvering load factor n that meets different terrains and usage modes. max ; (4) Calculate and formulate the minimum limiting maneuvering load factor n of the aircraft based on the flight safety analysis of the firefighting aircraft usage scenario min ; (5) Based on the above V F 、V FF and n max 、n min , combined with the minimum water-dropping airspeed V specified in the overall design requirements MN , and the maximum static normal force coefficient C of the aircraft in the fire-fighting configuration NMAX , calculate and draw the flight maneuver envelope.

2. The method for designing the flight maneuver envelope of a fire-fighting aircraft according to claim 1, characterized in that: Aircraft maximum limited maneuvering load factor n max Meet the minimum requirements for the maneuvering load factor n for executing hillside sliding, direct fire extinguishing, pulling up and disengaging, and hillside inclined turning and water dropping between specified valleys.

3. The method for designing the flight maneuvering envelope of a fire-fighting aircraft according to claim 1, characterized in that: In step (4), the aircraft minimum limiting maneuvering load factor n min The value of is as follows: According to the flight safety analysis of the firefighting aircraft usage scenario, in order to avoid unnecessary low-altitude collision risk, the minimum limit maneuvering load factor n is set. min is equal to zero.

4. The method for designing the flight maneuver envelope of a fire-fighting aircraft according to claim 1, characterized in that: In step (5), the horizontal axis speed range of the fire-fighting aircraft flight maneuvering envelope is the minimum water-dropping flight airspeed V specified in the overall design requirements. MN To the design flap speed V F The range of the maneuvering load factor n on the longitudinal axis is from the minimum limiting maneuvering load factor n min To the maximum limit maneuvering load factor n max ; The envelope boundary also includes V MN 、V MX 、V FF and V F Corresponding point.

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