Method for calculating takeoff stopping brake energy of airplane

Abstract

The invention provides a method for calculating takeoff stopping brake energy of an airplane. The method comprises the following steps: establishing an airplane ground motion model; calculating takeoff stopping brake energy; comparing the braking energy with the energy limit of the braking system; the aircraft takeoff stopping speed and takeoff stopping brake energy under the energy limitation of the brake system are obtained; calculating a takeoff stopping distance of the airplane; comparing the size relationship between the takeoff stopping distance and the airport runway length; and the final takeoff stopping weight, takeoff stopping distance, takeoff stopping speed and takeoff stopping brake energy are obtained. The method combines an aircraft ground motion model, considers actual flight parameters in the whole process of aircraft suspended takeoff and drag parachute release, can obtain the suspended takeoff speed and takeoff weight when the aircraft suspended takeoff under the airport runway length limit and the brake system energy limit, ensures the plateau flight safety of the aircraft, and improves the flight safety of the aircraft. And a new and accurate thought is provided for the design of comprehensively considering the deceleration capability of the aircraft drag parachute and the capability of a brake system.

Description

Technical Field

[0001] The invention relates to the field of aviation science and technology of aircraft, and in particular to a method for calculating braking energy of an aircraft aborted takeoff. Background Art

[0002] Braking energy is the energy absorbed by the brakes when the aircraft uses the brakes during the ground taxiing process. The wheel braking energy of the aircraft is an important indicator of the braking system, which directly limits the takeoff weight and braking speed of the aircraft when it aborts takeoff. Compared with the energy generated by stepping on the brakes during landing, the takeoff weight and braking speed of the aircraft when it aborts takeoff are large, and the braking energy generated is also greater. Therefore, the accuracy of the braking energy calculation method determines the safety of the aircraft tires and braking system, as well as the safety of the entire take-off and landing process of the aircraft. The calculation result should not be too conservative, resulting in the weight limit or speed limit being too small when the aircraft brakes, nor should it be too aggressive, resulting in the braking energy exceeding the limit when the aircraft aborts takeoff with heavy weight and high speed, causing the tire to burst or flat, the aircraft to be unable to stop, and the aircraft to run off the runway and cause an accident.

[0003] At present, the existing aircraft braking energy calculation has the following three deficiencies:

[0004] 1. The existing calculation method of braking energy is too simple, without combining the aircraft ground motion model, and without considering the changes of the actual flight parameters of the aircraft over time when the takeoff is aborted, resulting in large errors. The braking energy in most literature is directly equal to the kinetic energy when the aircraft starts to use the brakes, or a simplified formula related only to the aircraft weight and braking speed is given based on design experience.

[0005] 2. The existing braking energy calculation does not take into account the impact of the drag parachute on the braking energy calculation model, nor the contribution of the drag parachute to the reduction of wheel braking energy.

[0006] 3. The existing braking energy calculation does not take into account the length of the airport runway, which poses a risk of the aircraft running off the runway and causing an accident.

[0007] Based on this, we need to propose a method to calculate the braking energy of an aircraft aborted takeoff in detail. Summary of the invention

[0008] Taking into account the deficiencies of the above-mentioned prior art, the present invention provides a method for calculating the braking energy of an aircraft aborted takeoff for a conventional three-point front-end layout aircraft. The method combines the aircraft ground motion model and takes into account the actual flight parameters of the aircraft during the entire process of aborting takeoff and releasing the drag parachute. The aborted takeoff speed and takeoff weight of the aircraft when the takeoff is aborted under the airport runway length limit and the braking system energy limit can be obtained, thereby ensuring the safety of the aircraft's plateau flight and providing a new and more accurate idea for comprehensively considering the design of the aircraft's drag parachute deceleration capacity and the braking system capacity design.

[0009] The technical solution provided by the present invention is:

[0010] A method for calculating the braking energy of an aircraft aborted takeoff, characterized in that it specifically comprises the following steps:

[0011] Step 1: Establish an aircraft ground motion model;

[0012] Step 2: Considering the situation of deploying the drag parachute, a work model is established based on the aircraft ground motion model to calculate the braking energy for aborted takeoff;

[0013] Step 3: Compare the braking energy with the braking system energy limit: if the braking energy is greater than the braking system energy limit, reduce the takeoff abort speed and return to step 2 above; if the braking energy is less than or equal to the braking system energy limit, proceed to step 4;

[0014] Step 4: Obtain the aircraft aborted takeoff speed and aborted takeoff braking energy under the brake system energy limit;

[0015] Step 5: Calculate the taxiing distance of each stage according to the aborted takeoff speed, and then calculate the aborted takeoff distance of the aircraft;

[0016] Step 6: Compare the aborted takeoff distance and the airport runway length: if the aborted takeoff distance is greater than the airport runway length, reduce the aborted takeoff weight and return to step 2 above; if the aborted takeoff distance is less than or equal to the airport runway length, proceed to step 7;

[0017] Step 7: Obtain the final aborted takeoff weight, aborted takeoff distance, aborted takeoff speed, and aborted takeoff braking energy.

[0018] Furthermore, in step 1, the aircraft ground motion model includes:

[0019] Vertical:

[0020] Vertical:

[0021] Where: M is the mass of the aircraft; a is the horizontal acceleration; T is the instantaneous thrust of the engine; α is the aircraft angle of attack; is the engine installation angle; μ is the friction coefficient between the tire and the ground; F N is the support force on the aircraft; ρ is the air density; V is the flight speed of the aircraft; C L is the aircraft lift coefficient; S 0 , C D0 are the aircraft wing area and drag coefficient respectively; S 1 , C D1are the drag parachute area and drag coefficient respectively; g is the acceleration of gravity; φ is the slope of the airport runway.

[0022] Furthermore, the step 2 specifically includes:

[0023] Step 2-1: Establish the engine thrust work model: Calculate the engine takeoff thrust work W T1 、Engine slow speed thrust work W T2 ;

[0024] Step 2-2: Establish the rolling friction work model: Calculate the rolling friction work W N ;

[0025] Step 2-3: Establish a model of aerodynamic drag work: Calculate the aerodynamic drag work W D ;

[0026] Step 2-4: Establish the parachute work model: Calculate the parachute work W D1 ;

[0027] Step 2-5: Calculate the aborted takeoff braking energy W S :

[0028] W S =W T1 +W T2 -W N -W D -W D1 .

[0029] Furthermore, in step 4, obtaining the aircraft takeoff abort speed and takeoff abort braking energy under the energy limit of the braking system includes:

[0030] a) If W S ≤W M , then the speed V used during braking is the takeoff termination speed, W S To terminate the takeoff braking energy;

[0031] b) If W S >W M , then it is necessary to reduce the aborted takeoff speed V, keep the aborted takeoff weight G unchanged, and recalculate W according to steps 2 to 3 S , until W S ≤W M , then V at this time is the takeoff termination speed under the energy limit of the braking system, and the corresponding W S That is, the braking energy of the aircraft aborting takeoff under the energy limitation of the braking system.

[0032] Preferably, the termination takeoff speed V = VN × ΔV, N = 1, 2, 3 ..., ΔV is 0.1 m / s or other reasonable speed steps, and V should not exceed the takeoff speed V at the corresponding weight. LOF , Maximum allowable braking speed V M Small and medium ones.

[0033] Furthermore, the step 5 specifically includes:

[0034] Step 5-1: Obtain the rolling distance L from the time the aircraft starts at zero speed to the moment the throttle is closed and the brake is applied 1 ;

[0035] Step 5-2: Obtain the rolling distance L of the aircraft from the moment the brakes are applied to the moment the drag parachute is released 2 ;

[0036] Step 5-3: Obtain the aircraft's rolling distance L from the moment the drag parachute is released to the moment it is abandoned 3 ;

[0037] Step 5-4: Obtain the rolling distance L from the moment the aircraft abandons the drag parachute to the moment the aircraft stops 4 ;

[0038] Step 5-5: Calculate the aircraft's aborted takeoff distance L S :

[0039] L S =L 1 +L 2 +L 3 +L 4 .

[0040] Furthermore, in step 7, obtaining the final aborted takeoff weight, aborted takeoff distance, aborted takeoff speed, and aborted takeoff braking energy includes:

[0041] a) If L S ≤L, the takeoff weight G used is the aborted takeoff weight, L S is the aircraft's aborted takeoff distance, V obtained in step 4 is the aborted takeoff speed, and W obtained in step 4 is S To terminate the takeoff braking energy;

[0042] b) If L S > L, then the aborted takeoff weight G needs to be reduced, and the aircraft aborted takeoff distance L is calculated according to steps 2 to 6. S , until L is satisfied S ≤L, then the takeoff weight G at this time is the maximum aborted takeoff weight limited by the airport runway length, and the corresponding L S is the aircraft aborted takeoff distance limited by the runway length, V obtained in step 4 is the maximum aborted takeoff speed, and W obtained in step 4 isS The maximum aborted takeoff braking energy limited by the airport runway length.

[0043] Preferably, the terminated takeoff weight G=M×gN×ΔM×g, N=1, 2, 3..., ΔM is the unit mass of the aircraft weight reduction.

[0044] Beneficial Effects

[0045] 1. The present invention combines the aircraft ground motion model, considers the actual flight parameters of the aircraft during the whole process of aborting takeoff and releasing the drag parachute, and provides a relatively accurate method for calculating the braking energy of the aircraft aborting takeoff. The aborted takeoff speed and takeoff weight of the aircraft when the takeoff is aborted under the restriction of the airport runway length and the energy restriction of the braking system can be obtained, which provides a new and more accurate method for comprehensively considering the design of the deceleration capacity of the aircraft drag parachute and the design of the braking system capacity.

[0046] 2. The present invention can more accurately calculate the braking energy of an aircraft when taking off, and ensure the safety of the aircraft in plateau flight. When an aircraft takes off under plateau conditions, the air density decreases, the true air speed increases, and the braking energy increases compared to that in plains. Therefore, the accuracy of the braking energy calculation is particularly important, which is directly related to the take-off performance of the aircraft at the plateau airport. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 The present invention is a flow chart of a method for calculating the braking energy of an aircraft aborted takeoff. DETAILED DESCRIPTION

[0048] This exemplary embodiment is provided to make the present invention more complete and comprehensive, and to fully convey the concepts and steps of the specific embodiments to those skilled in the art.

[0049] The implementation case is a specific application of the implementation method of the aircraft aborted takeoff braking energy calculation method. Now, the features of the present invention will be further described in detail with reference to the accompanying drawings.

[0050] Implementation Case 1

[0051] Reference Figure 1 , a method for calculating the braking energy of an aircraft aborted takeoff, specifically comprising the following steps:

[0052] Step 1: Establish an aircraft ground motion model;

[0053] Step 2: Considering the situation of deploying the drag parachute, a work model is established based on the aircraft ground motion model to calculate the braking energy for aborted takeoff;

[0054] Step 3: Compare the braking energy with the braking system energy limit: if the braking energy is greater than the braking system energy limit, reduce the takeoff abort speed and return to step 2 above; if the braking energy is less than or equal to the braking system energy limit, proceed to step 4;

[0055] Step 4: Obtain the aircraft aborted takeoff speed and aborted takeoff braking energy under the brake system energy limit;

[0056] Step 5: Calculate the taxiing distance of each stage according to the aborted takeoff speed, and then calculate the aborted takeoff distance of the aircraft;

[0057] Step 6: Compare the aborted takeoff distance and the airport runway length: if the aborted takeoff distance is greater than the airport runway length, reduce the aborted takeoff weight and return to step 2 above; if the aborted takeoff distance is less than or equal to the airport runway length, proceed to step 7;

[0058] Step 7: Obtain the final aborted takeoff weight, aborted takeoff distance, aborted takeoff speed, and aborted takeoff braking energy.

[0059] In this implementation case, specifically, in step 1, the longitudinal and vertical ground motion models of the aircraft are established by combining formulas (1) and (2), including:

[0060] Vertical:

[0061] Vertical:

[0062] Where: M is the mass of the aircraft; a is the horizontal acceleration; T is the instantaneous thrust of the engine; α is the aircraft angle of attack; is the engine installation angle; μ is the friction coefficient between the tire and the ground; F N is the support force on the aircraft; ρ is the air density; V is the flight speed of the aircraft; C L is the aircraft lift coefficient; S 0 , C D0 are the aircraft wing area and drag coefficient respectively; S 1 , C D1 are the drag parachute area and drag coefficient respectively; g is the acceleration of gravity; φ is the slope of the airport runway.

[0063] In this implementation case, specifically, in step 2, considering the situation of deploying the drag parachute, based on the aircraft ground motion model obtained in step 1, the engine thrust work model, rolling friction work model, aerodynamic drag work model, and drag parachute work model are established to calculate the engine takeoff thrust work W T1 、Engine slow speed thrust work W T2 , rolling friction work WN 、 Aerodynamic resistance work W D 、Work done by the drag parachute W D1 , use formula (3) to calculate the aborted takeoff braking energy W S ,include:

[0064] W S =W T1 +W T2 -W N -W D -W D1 (3)

[0065] In this implementation case, specifically, in step 3, the braking energy W obtained in step 2 is compared. S With brake system energy limit W M Size relationship.

[0066] In this implementation case, specifically, in step 4, in combination with the comparison result in step 3, obtaining the aircraft aborted takeoff braking energy and aborted takeoff speed under the energy limit of the braking system includes:

[0067] a) If W S ≤W M , then the speed V used during braking is the takeoff termination speed, W S To terminate the takeoff braking energy;

[0068] b) If W S >W M , then the takeoff termination speed V needs to be reduced (let V = VN × ΔV, N = 1, 2, 3 ..., ΔV is 0.1m / s or other reasonable speed steps, V should not exceed the takeoff speed V at the corresponding weight LOF , Maximum allowable braking speed V M (smaller or larger), keep the aborted takeoff weight G unchanged, and recalculate W according to steps 2 to 3. S , until W S ≤W M At this time, V is the takeoff termination speed under the energy limit of the braking system, and the corresponding W S That is, the braking energy of the aircraft aborting takeoff under the energy limitation of the braking system.

[0069] In this implementation case, specifically, in step 5, according to the aborted takeoff speed obtained in step 4, based on the aircraft ground motion model obtained in step 1, the rolling distance L of the aircraft from the start of the speed being zero to the moment of closing the throttle and applying the brake is calculated. 1 , the aircraft's rolling distance from the moment the brakes are applied to the moment the drag parachute is released L 2 , the aircraft's rolling distance L from the moment the drag parachute is released to the moment it is abandoned 3, the rolling distance L from the moment the aircraft abandons the drag parachute to the moment the aircraft stops 4 , use formula (4) to calculate the aircraft aborted takeoff distance L S ,include:

[0070] L S =L 1 +L 2 +L 3 +L 4 (4)

[0071] In this implementation case, specifically, in step 6, the takeoff termination distance L obtained in step 5 is compared. S Relationship with the airport runway length L.

[0072] In this implementation case, specifically, in step 7, the final aborted takeoff distance, aborted takeoff weight, aborted takeoff speed, and aborted takeoff braking energy are obtained in combination with the comparison result in step 6, including:

[0073] a) If L S ≤L, the takeoff weight G used is the aborted takeoff weight, L S is the aircraft's aborted takeoff distance, V obtained in step 4 is the aborted takeoff speed, and W obtained in step 4 is S To terminate the takeoff braking energy;

[0074] b) If L S > L, then the aborted takeoff weight G needs to be reduced (let G = M × gN × ΔM × g, N = 1, 2, 3 ..., ΔM is the unit mass of the aircraft weight reduction), and the aircraft aborted takeoff distance L is calculated according to steps 2 to 6. S , until L is satisfied S ≤L, then the takeoff weight G at this time is the maximum aborted takeoff weight limited by the airport runway length, and the corresponding L S is the aircraft aborted takeoff distance limited by the runway length, V obtained in step 4 is the maximum aborted takeoff speed, and W obtained in step 4 is S The maximum aborted takeoff braking energy limited by the airport runway length.

[0075] Implementation Case 2

[0076] Implementation Case 2 is a specific application of a method for calculating the braking energy of an aircraft aborted takeoff proposed in Implementation Case 1.

[0077] Given the relevant characteristic parameters of a civil aircraft such as weight, wing area, lift and drag characteristics, engine thrust, fuel consumption data, relevant characteristic parameters of the drag parachute, rolling and sliding friction coefficients, airport-related parameter conditions, and energy limitations of the wheel brake system, the braking energy required for the aircraft wheel brakes is calculated.

[0078] According to the aircraft takeoff abort braking energy calculation method provided by the present invention, it can be divided into the following four situations:

[0079] Case 1: The calculated braking energy is less than or equal to the braking system energy limit, and the corresponding aborted takeoff distance is less than or equal to the airport runway length;

[0080] Case 2: The calculated braking energy is greater than the braking system energy limit, and the corresponding aborted takeoff distance is less than or equal to the airport runway length;

[0081] Case 3: The calculated braking energy is less than or equal to the braking system energy limit, and the corresponding aborted takeoff distance is greater than the airport runway length;

[0082] Case 4: The calculated braking energy is greater than the braking system energy limit, and the corresponding aborted takeoff distance is greater than the airport runway length.

[0083] 1) For case 1: Both the braking energy and the aborted takeoff distance meet the restriction conditions. The braking energy calculated at this time is the result of the calculation under the conditions of the airport. For example, for a three-wheeled aircraft, the takeoff weight is 22,000 kg and the wing area is 70 m 2 , rolling friction coefficient 0.03, sliding friction coefficient 0.35, brake system energy limit 35MJ. If the height of a plain airport is 0m, the temperature is 15℃, and the runway length is 2200m, calculate according to steps 1 to 7 in the technical solution, and the results are shown in Table 1. The calculation results show that both the braking energy and the aborted takeoff distance meet the restriction conditions.

[0084] Table 1 Calculation results of brake energy for aborted takeoff (case 1)

[0085]

[0086] 2) For case 2: the braking energy does not meet the limit condition, the takeoff abort speed needs to be reduced until the calculated result meets the braking energy limit. For example, for a three-point aircraft, the takeoff weight is 22,000 kg and the wing area is 70 m 2 , rolling friction coefficient 0.03, sliding friction coefficient 0.35, brake system energy limit 35MJ. If a plain airport is known to have a height of 0m, a field temperature of 35℃, and an airport runway length of 2200m, calculate according to steps 1 to 4 in the technical solution, and the results are shown in Table 2.

[0087] Table 2 Calculation results of brake energy for aborted takeoff (case 2)

[0088]

[0089] The calculated braking energy result in Table 2 is greater than the braking system energy limit, and the aborted takeoff speed is reduced, and the calculation is performed according to item b) of step 4 in the technical solution until the braking energy meets the limit condition; the aborted takeoff distance is calculated according to steps 5 to 7 in the technical solution, and the calculation results are shown in Table 3. The calculation results show that the braking energy and aborted takeoff distance after reducing the aborted takeoff speed both meet the limit conditions.

[0090] Table 3 Calculation results after reducing the aborted takeoff speed (case 2)

[0091]

[0092] 3) For case 3: the takeoff distance does not meet the restriction condition, the takeoff weight needs to be reduced until the calculated result meets the airport runway length restriction. For example, for a three-point aircraft, the takeoff weight is 22,000 kg and the wing area is 70 m 2 , rolling friction coefficient 0.03, sliding friction coefficient 0.35, brake system energy limit 55MJ. If it is known that a certain plateau airport is 4000m high, the field temperature is -14℃, and the airport runway length is 3000m, calculate according to steps 1 to 7 in the technical solution, and the results are shown in Table 4.

[0093] Table 4 Calculation results of brake energy for aborted takeoff (case 3)

[0094]

[0095] The calculation result of the aborted takeoff distance in Table 4 is greater than the airport runway length limit. Reduce the aborted takeoff weight and calculate according to item b) in step 7 of the technical solution until the aborted takeoff distance meets the limit conditions. The calculation results are shown in Table 5. The calculation results show that the braking energy and aborted takeoff distance after reducing the aborted takeoff weight both meet the limit conditions.

[0096] Table 5 Calculation results after reducing the aborted takeoff weight (case 3)

[0097]

[0098] 4) For case 4: Both the braking energy and the aborted takeoff distance do not meet the restriction conditions, and the aborted takeoff speed and aborted takeoff weight need to be reduced to first meet the braking system energy restriction condition and then meet the airport runway length restriction condition. For example, for a front three-point aircraft, the aircraft takeoff weight is known to be 22,000 kg and the wing area is 70 m 2 , rolling friction coefficient 0.03, sliding friction coefficient 0.35, brake system energy limit 55MJ. If it is known that a certain plateau airport is 4000m high, the field temperature is 5.8℃, and the airport runway length is 3000m, calculate according to steps 1 to 4 in the technical solution, and the results are shown in Table 6.

[0099] Table 6 Calculation results of brake energy for aborted takeoff (case 4)

[0100]

[0101] The calculated braking energy result in Table 6 is greater than the braking system energy limit. Reduce the aborted takeoff speed and calculate according to item b) in step 4 of the technical solution until the braking energy meets the limit condition. The calculation results are shown in Table 7.

[0102] Table 7 Calculation results after reducing the aborted takeoff speed 1 (Case 4)

[0103]

[0104] The aborted takeoff distance is calculated according to steps 5 to 7 in the technical solution, and the results are shown in Table 8. The aborted takeoff distance calculation result in Table 8 is greater than the airport runway length limit, and the aborted takeoff weight is reduced, and the aborted takeoff distance is calculated according to item b) in step 7 in the technical solution until the aborted takeoff distance meets the restriction conditions. The calculation results are shown in Table 9. The calculation results show that the braking energy and aborted takeoff distance after reducing the aborted takeoff speed and aborted takeoff weight meet the restriction conditions.

[0105] Table 8 Calculation results after reducing the aborted takeoff speed 2 (Case 4)

[0106]

[0107] Table 9 Calculation results after reducing the aborted takeoff weight (Case 4)

[0108]

[0109] In both cases 2 and 4, the braking energy exceeds the limit. At this time, it is possible to consider improving the functional performance of the wheel brake system and increasing the wheel brake limit energy, thereby relaxing the brake system energy limit conditions, which will help increase the maximum abort takeoff weight and abort takeoff speed.

[0110] In cases 2, 3, and 4, the braking energy exceeds the limit or the aborted takeoff distance exceeds the limit, or both. In this case, it is possible to consider improving the drag parachute function and performance, increasing the parachute rope carrying capacity, thereby increasing the drag parachute release speed and the aircraft drag reduction capability, which can reduce the braking energy and aborted takeoff distance, and help increase the maximum aborted takeoff weight and aborted takeoff speed.

[0111] The implementation cases listed above only provide specific implementation methods of the present invention, which are convenient for those skilled in the art to understand. It should be noted that the calculation steps given in the drawings and implementation methods of the present invention do not need to be strictly followed in this order by the technician, and can be omitted, combined or decomposed for execution. Without departing from the technical solution given in this application, any improvements or modifications made still fall within the scope of protection of this application.

[0112] This application is intended to cover any improvements or modifications of the present invention, including some common sense techniques or principle concepts and formulas in the technical field that are not disclosed in the present invention.

Claims

1. A method for calculating the braking energy of an aircraft aborted takeoff, characterized in that: The specific steps include: Step 1: Establish an aircraft ground motion model; Step 2: Considering the situation of deploying the drag parachute, a work model is established based on the aircraft ground motion model to calculate the braking energy for aborted takeoff; Step 3: Compare the braking energy with the braking system energy limit: if the braking energy is greater than the braking system energy limit, reduce the takeoff abort speed and return to step 2 above; if the braking energy is less than or equal to the braking system energy limit, proceed to step 4; Step 4: Obtain the aircraft aborted takeoff speed and aborted takeoff braking energy under the brake system energy limit; Step 5: Calculate the taxiing distance of each stage according to the aborted takeoff speed, and then calculate the aborted takeoff distance of the aircraft; Step 6: Compare the aborted takeoff distance and the airport runway length: if the aborted takeoff distance is greater than the airport runway length, reduce the aborted takeoff weight and return to step 2 above; if the aborted takeoff distance is less than or equal to the airport runway length, proceed to step 7; Step 7: Obtain the final aborted takeoff weight, aborted takeoff distance, aborted takeoff speed, and aborted takeoff braking energy.

2. The method for calculating the braking energy of an aircraft aborted takeoff according to claim 1, characterized in that: In step 1, the aircraft ground motion model includes: Vertical: Vertical: Where: M is the mass of the aircraft; a is the horizontal acceleration; T is the instantaneous thrust of the engine; α is the aircraft angle of attack; is the engine installation angle; μ is the friction coefficient between the tire and the ground; F N is the support force on the aircraft; ρ is the air density; V is the flight speed of the aircraft; C L is the lift coefficient of the aircraft; S0, C D0 are the wing area and drag coefficient of the aircraft respectively; S1, C D1 are the drag parachute area and drag coefficient respectively; g is the acceleration of gravity; φ is the slope of the airport runway.

3. The method for calculating the braking energy of an aircraft aborted takeoff according to claim 1, characterized in that: The step 2 specifically includes: Step 2-1: Establish the engine thrust work model: Calculate the engine takeoff thrust work W T1 、Engine slow speed thrust work W T2 ; Step 2-2: Establish the rolling friction work model: Calculate the rolling friction work W N ; Step 2-3: Establish a model of aerodynamic drag work: Calculate the aerodynamic drag work W D ; Step 2-4: Establish the parachute work model: Calculate the parachute work W D1 ; Step 2-5: Calculate the aborted takeoff braking energy W S : IN S =In T1 +W T2 -IN N -IN D -IN D1 。 4. The method for calculating the braking energy of an aircraft aborted takeoff according to claim 1, characterized in that: The step 4 obtains the aircraft takeoff abort speed and takeoff abort braking energy under the brake system energy limit, including: a) If W S ≤W M , then the speed V used during braking is the takeoff termination speed, W S To terminate the takeoff braking energy; b) If W S >W M , then it is necessary to reduce the aborted takeoff speed V, keep the aborted takeoff weight G unchanged, and recalculate W according to steps 2 to 3 S , until W S ≤W M , then V at this time is the takeoff termination speed under the energy limit of the braking system, and the corresponding W S That is, the braking energy of the aircraft aborting takeoff under the energy limitation of the braking system.

5. The method for calculating the braking energy of an aircraft aborted takeoff according to claim 4, characterized in that: The termination takeoff speed V = VN × ΔV, N = 1, 2, 3 ..., ΔV is 0.1m / s or other reasonable speed steps, V should not exceed the takeoff speed V at the corresponding weight. LOF , Maximum allowable braking speed V M Small and medium ones.

6. The method for calculating the braking energy of an aircraft aborted takeoff according to claim 1, characterized in that: The step 5 specifically includes: Step 5-1: Obtain the rolling distance L1 from the aircraft speed being zero to the moment when the throttle is closed and the brake is applied; Step 5-2: Obtain the rolling distance L2 of the aircraft from the moment the brakes are applied to the moment the drag parachute is released; Step 5-3: Obtain the aircraft's rolling distance L3 from the moment the drag parachute is released to the moment it is abandoned; Step 5-4: Obtain the rolling distance L4 from the moment the drag parachute is abandoned to the moment the aircraft stops; Step 5-5: Calculate the aircraft's aborted takeoff distance L S : <h2 style=";text-align:left;direction:ltr">L<h2 style=";text-align:left;direction:ltr"> S <h2 style=";text-align:left;direction:ltr"> (L1+L2+L3+L4) 7. The method for calculating the braking energy of an aircraft aborted takeoff according to claim 1, characterized in that: In step 7, obtaining the final aborted takeoff weight, aborted takeoff distance, aborted takeoff speed, and aborted takeoff braking energy includes: a) If L S ≤L, the takeoff weight G used is the aborted takeoff weight, L S is the aircraft's aborted takeoff distance, V obtained in step 4 is the aborted takeoff speed, and W obtained in step 4 is S To terminate the takeoff braking energy; b) If L S > L, then the aborted takeoff weight G needs to be reduced, and the aircraft aborted takeoff distance L is calculated according to steps 2 to 6. S , until L is satisfied S ≤L, then the takeoff weight G at this time is the maximum aborted takeoff weight limited by the airport runway length, and the corresponding L S is the aircraft aborted takeoff distance limited by the runway length, V obtained in step 4 is the maximum aborted takeoff speed, and W obtained in step 4 is S The maximum aborted takeoff braking energy limited by the airport runway length.

8. The method for calculating the braking energy of an aircraft aborted takeoff according to claim 7, characterized in that: The terminated takeoff weight G=M×gN×ΔM×g, N=1, 2, 3..., ΔM is the unit mass of the aircraft weight reduction.

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