CN113533784B - GPS (global positioning system) round-trip non-constant-speed flat flight airspeed calibration method - Google Patents

Abstract

The invention relates to a GPS (global positioning system) round-trip non-constant-speed flat flight airspeed calibration method, which is used for determining the range of a full envelope of an airplane to be tested, wherein the range of the air pressure altitude within the range of the full envelope of the airplane to be tested isH ₁ ～H _N ，NIs a natural number more than 1, and comprises the following steps: step 1, selecting a height ofH _m In airspace, a plurality of groups of airspeed calibration results of non-constant speed back-and-forth fly-to-fly flight are tested in sequence to obtain the altitude ofH _m Airspeed calibration results of airspace; step 2, according to the same method of the step 1, respectively testing the height ofH ₁ 、H _N And is high atH ₁ ～H _N And obtaining airspeed calibration results within the full envelope range according to airspeed calibration results of a plurality of airspaces within the full envelope range. The method is used for carrying out airspeed calibration based on different flight speeds, avoids repeated flight of the same speed, improves the efficiency of airspeed calibration, reduces the trial flight number of airspeed calibration, promotes the progress of a trial flight task and has high accuracy.

Description

GPS (global positioning system) round-trip non-constant-speed flat flight airspeed calibration method

Technical Field

The invention relates to the technical field of airspeed calibration methods of aircraft atmospheric systems, in particular to a GPS (global positioning system) round-trip non-constant-speed flat flight airspeed calibration method.

Background

The airspeed calibration test flight of the aircraft atmospheric system is a basic subject for scientific research of the test flight of the aircraft, is also a key subject, and is often related to the design of a flight control law and the safety of flight control. However, in the trial flight phase, due to the constraint of the aircraft commissioning time, the constraint of the trial flight cost, and the limitation of the number of flight frames, only airspeed calibration trial flight is often performed on individual sample points, the trial flight sample points do not sufficiently cover the full envelope of the aircraft, an accurate airspeed calibration correction amount of the atmospheric system in the full envelope range cannot be obtained, and the safety of subsequent trial flight is affected. Therefore, how to obtain a more accurate correction quantity for calibrating the airspeed of the atmospheric system by using a smaller sample size or irregular test flight data in the test flight process is a long-term focus of attention of researchers. The problem that the accuracy of airspeed calibration is affected due to the fact that the amount of data samples is small or the data is irregular is solved, and different test flight methods and correction algorithms need to be adopted to improve the test flight efficiency.

At present, many experts and scholars propose a plurality of test correction algorithms related to atmospheric calibration, for example, methods such as a GPS round-trip constant speed flat flight method, a GPS round-trip flat flight acceleration method, a GPS double altitude calibration method, a GPS single altitude calibration method and the like perform airspeed calibration, so that airspace limitation requirements are reduced, test flight landing data and data processing workload are reduced, and test flight verification shows that the test results have high accuracy. A GPS velocity method aiming at the position error of an airspeed system is also proposed to carry out airspeed calibration; and a theoretical basis and a test method for carrying out airspeed calibration by adopting a GPS trilateral method. The method selects the same speed to carry out flight at different track angles, and completes airspeed calibration of the atmospheric system. However, these methods have the following disadvantages: the repeated flight at the same speed consumes a large amount of flight time and flight number, and particularly, for an airplane with short flight time, the single number is not enough to finish the test flight of a plurality of airspeed calibration sample points, so that the airspeed calibration of all test flight test points in the altitude-speed full envelope can be finished only by increasing the flight number and delaying task nodes, and the test complexity and the test error are increased.

Disclosure of Invention

The invention aims to: aiming at the defects in the prior art, a GPS round-trip non-constant speed flat flight airspeed calibration method is provided. The method is used for carrying out airspeed calibration based on different flight speeds, avoids repeated flight of the same speed, improves the efficiency of airspeed calibration, reduces the trial flight number of airspeed calibration, advances the progress of a trial flight task, ensures the accuracy, and has positive significance and profound influence on the design of the subsequent flight control law of the airplane and the safety of flight control.

In order to achieve the purpose, the invention adopts the technical scheme that:

a GPS round-trip non-constant speed flat flight airspeed calibration method comprises the following steps:

step a, at a height ofH _m Selecting a starting flying point in a certain directionV _it1Indicating vacuum speed to fly at uniform speed for a certain strokeS ₁ Acquiring first data during flight, the first data including an indication of true airspeedV _it1Total atmospheric temperatureT ₀₁Total pressure ofP ₀₁Speed of the earthV _d1；

Step b, after reaching the back-and-forth point, the parallel and opposite stroke is followedS ₁ In the direction ofV _it2Indicating that the vacuum speed flies at a constant speed, wherein,V _it1is not equal toV _it2And acquiring second data during the flight, the second data including an indication of true airspeedV _it2Total atmospheric temperatureT ₀₂Total pressure ofP ₀₂Speed of the earthV _d2；

Step c, solvingV _it1AndV _it2and obtaining a set of airspeed calibration results of the back-and-forth fly-to-fly flight by using the airspeed calibration results under two different indicated vacuum speeds.

The GPS round-trip non-constant-speed flat flight airspeed calibration method provided by the invention comprises the test of an airspeed calibration result of non-constant-speed round-trip flight, and the method is used for calibrating the airspeed based on different flight speeds, so that repeated flight at the same speed is avoided, the airspeed calibration efficiency is improved, the trial flight number of airspeed calibration is reduced, the progress of a trial flight task is promoted, the accuracy is ensured, and the method has positive significance and profound influence on the design of a subsequent flight control law of an airplane and the safety of flight control. In the whole test process, in the range of the full envelope to be tested, selecting a high airspace, sequentially carrying out multiple groups of non-constant speed back and forth flying in the same high airspace, obtaining airspeed calibration results of the same high airspeed, and then carrying out airspeed calibration tests of different high airspeeds in the range of the full envelope to be tested according to the same method to obtain space calibration results in the range of the full envelope to be tested.

Further, solving forV _it1 AndV _it2 the specific procedure for the airspeed calibration results at two different indicated vacuum speeds is as follows:

step A, measuring the total pressureP ₀₁ 、P ₀₂Respectively substituting the first equation into the first equation to obtain a first equation and a second equation;

wherein, the first formula is:

；P ₀is the total pressure of the mixture,Pin order to be at a static pressure,Mis a Mach number of the component (A),ris the specific heat ratio;

the first equation is:

；

the second equation is:

；P ₀₁ 、P ₀₂ respectively indicating vacuum speed for differentV _it1 AndV _it2 the total pressure of the reaction mixture under reduced pressure,P ₁ 、P ₂ respectively indicating vacuum speed for differentV _it1 AndV _it2 the static pressure of the lower part of the tank,M ₁ 、M ₂ respectively indicating vacuum speed for differentV _it1 AndV _it2 lower Mach number;

step B, the total temperature of the atmosphereT ₀₁、T ₀₂Respectively substituting into the second formula to obtain a third formula and a fourth formula;

wherein, the formula two is:

；T ₀ the total temperature of the atmosphere is the temperature of the atmosphere,Tthe temperature is set to be a static temperature,T ₁ =T ₂ =T，Mis Mach number;

the third program is:

；

the fourth equation is:

；T ₀₁ 、T ₀₂ respectively indicating vacuum speed for differentV _it1 AndV _it2 the total temperature of the atmosphere below the temperature,T ₁ andT ₂ respectively indicating vacuum speed for differentV _it1 AndV _it2 the temperature of the mixture is lower than the normal temperature,M ₁ 、M ₂ respectively indicating vacuum speed for differentV _it1 AndV _it2 lower Mach number;

wherein, T₁＝T₂＝T_x；T_xIs a static temperature value;

step C, mixing the ground speedV _d1、V _d2Respectively substituting the formula III to obtain a fifth equation;

wherein, the formula three is:

；V _dn andV _dm indicating vacuum speed for different purposesV _itn AndV _itm ground speed for downward forward flight and reverse flight;M _n andM _m is different fromIndicating vacuum speedV _itn AndV _itm t is the static temperature;

the fifth equation is:

；V _d1 to indicate the vacuum speedV _it1 The ground speed of the lower forward flight,V _d2 to indicate the vacuum speedV _it2 Ground speed of the reverse flight; tx is a static temperature value;M ₁ 、M ₂ respectively indicating vacuum speed for differentV _it1 AndV _it2 lower Mach number;

step D, simultaneously establishing a first equation, a second equation, a third equation, a fourth equation and a fifth equation; the Mach number can be obtainedM ₁、M ₂(ii) a Static pressureP ₁、P ₂And static temperatureTI.e. test flight sample points at different indicated vacuum speedsT，P ₁，M ₁) And (a)T，P ₂，M ₂）；

Step E, substituting the two sample points obtained in the step D into a formula seven to obtain two different actual vacuum speeds, and obtaining the vacuum pressureV _it1AndV _it2two different airspeed calibration results at indicated vacuum speeds;

wherein, the formula seven is:

(ii) a Wherein the content of the first and second substances,V _tin order to realize the vacuum speed,Tthe temperature is set to be a static temperature,Mis mach number.

Further, in the step b, the process is carried outS ₁ And returning the original path to test.

Further, the time interval between the step b and the step a is controlled within 20 min. The research finds that the interval time of the non-constant speed opposite flight cannot be too long, the too long time can cause excessive change of the environment, the stability is poor, and the error of the calibration result is large. Further, the time interval between the step b and the step a is 5-20 min.

Further, the indication of the vacuum rate, the total temperature of the atmosphere and the total pressure are measured by an atmospheric system, and the ground speed is measured by a GPS device.

Further, after completing a set of back-and-forth flying flights of the step a and the step b, the flying speed is changed, and the flying speed is changed at the same height according to the same method of the step a and the step bH _m And c, performing multiple groups of back-and-forth fly-to-fly flights, and calculating the airspeed calibration result of each group of back-and-forth fly-to-fly flights according to the same method in the step c, so as to obtain the airspeed calibration result at the same altitude.

Further, after completing the calibration of the airspeed at a height, according to the same method, the height is respectively testedH ₁ 、H _N （NIs a natural number greater than 1) and has a height ofH ₁ ～H _N The airspeed calibration results of a plurality of height airspaces within the range of obtaining the height from the groundH ₁ ～H _N And (5) calibrating the airspeed within the full envelope range.

In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:

1. the invention provides a GPS (global positioning system) round-trip non-constant-speed flat flight airspeed calibration method, which comprises the steps of firstly selecting a high airspace within a full envelope range to be tested, sequentially carrying out multiple groups of non-constant-speed round-trip flight in the same high airspace to obtain an airspeed calibration result of the same high airspace, and then carrying out airspeed calibration tests of different high airspaces within the full envelope range to be tested according to the same method.

Drawings

FIG. 1 is a plot of the airspeed calibration test procedure for the full envelope range of example 1.

Fig. 2 is a chart showing the shuttle to flight of the airplane in embodiment 1.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings.

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1

As shown in fig. 1, a method for calibrating a GPS round-trip non-constant velocity flat flight airspeed includes the following steps: determining the range of the full envelope of the airplane to be tested, wherein the range of the vertical height from the ground in the range of the full envelope to be tested isH ₁ ～H _N ，NIs a natural number greater than 1.

General assumptions for the airspeed calibration method:

(1) the short-time atmospheric environment in the same airspace is the same, namely the static temperature and the wind speed/wind direction are the same;

(2) the total pressure is the sum of static pressure and dynamic pressure.

1 test flight procedure

1.1 test flight method

In the same airspace and at the same height H_mSelecting two different speeds respectivelyV _it1AndV _it2and the shuttle pair flight is performed, and the chart is shown in figure 2.

The test procedure of the airspeed calibration result of non-constant speed back-and-forth flying flight is as follows:

step a, at a height ofH _m In a space domain, a flying point is selected along a certain directionV _it1Indicating vacuum speed to carry out uniform speed flight for a section of travelS ₁ Reading first data by using a GPS system in the flight process: indicating vacuum speedV _it1Total atmospheric temperatureT ₀₁Total pressure ofP ₀₁Speed of the earthV _d1。

Step b, then, flying the airplane to the height H_mIn the airspace parallel to the strokeS ₁ In the direction ofV _it2The indicated vacuum speed is flown at the uniform speed, and a GPS system is utilized to read second data in the flying process: indicating vacuum speedV _it2Total atmospheric temperatureT ₀₂Total pressure ofP ₀₂Speed of the earthV _d2。

The time interval between the step b and the step a is controlled within 20 min.

1.2 data acquisition

In airspeed calibration test flight, the test flight data to be collected are vacuum speed, total atmospheric temperature, total pressure and ground speed, wherein the vacuum speed, the total atmospheric temperature and the total pressure are measured by an atmospheric system, and the ground speed is measured by a GPS device.

2 airspeed calibration method

Solving forV _it1AndV _it2and obtaining the airspeed calibration result of the group of non-constant-speed back-and-forth opposite flight by two airspeed calibration results under different indicated vacuum speeds:

2.1 mechanics model

2.1.1 pressure dependence of Mach number

（1）

Wherein the content of the first and second substances,P ₀is the total pressure of the mixture,Pin order to be at a static pressure,Mis a Mach number of the component (A),rthe specific heat ratio is generally 1.4.

2.1.2 relation of total atmospheric temperature, static temperature and Mach number

（2）

Wherein，T ₀The total temperature of the atmosphere is the temperature of the atmosphere,Tthe temperature is set to be a static temperature,Mis mach number.

2.1.3 ground speed vs. vacuum speed

（3）

Wherein the content of the first and second substances,V _din order to obtain the ground speed,V _tin order to realize the vacuum speed,V _windis the wind speed.

2.1.4 relation of vacuum speed, Mach number and static temperature

（4）

（5）

To obtain

（6）

Wherein the content of the first and second substances,V _tin order to realize the vacuum speed,Tthe temperature is set to be a static temperature,Mis mach number.

2.2 airspeed calibration algorithm

2.2.1 pressure and Mach number relation at different indicated vacuum speeds

According to equation (1) of bar 2.1.1, the vacuum rate (1) can be indicated at different pointsV _it1AndV _it2the same applies below), the pressure and mach number formula is:

（7）

（8）

wherein the content of the first and second substances,P ₀₁、P ₀₂respectively indicating vacuum speed for differentV _it1AndV _it2the total pressure of the reaction mixture under reduced pressure,P ₁、P ₂respectively indicating vacuum speed for differentV _it1AndV _it2the static pressure of the lower part of the tank,M ₁、M ₂respectively indicating vacuum speed for differentV _it1AndV _it2the Mach number of the lower one,rthe specific heat ratio is generally 1.4.

According to item 1.2, it is knownP ₀₁ 、P ₀₂Measured by an atmospheric data system to be a known number;P ₁、P ₂、M ₁andM ₂is an unknown number.

2.2.2 different atmospheric total temperature and static temperature relations under indicated vacuum speed

According to the equation (2) in item 2.1.2, the relationship between the total temperature and the static temperature of the atmosphere at different indicated vacuum speeds can be obtained as follows:

（9）

（10）

according to the general assumption of airspeed calibration, the addition formula is as follows:

（11）

obtaining the equation set of the total temperature and the static temperature of the atmosphere under different indicated vacuum speeds:

（12）

（13）

wherein the content of the first and second substances,T ₀₁、T ₀₂respectively indicating vacuum speed for differentV _it1AndV _it2the total temperature of the atmosphere below the temperature,Tthe different indicated vacuum rates obtained for equation (11)V _it1AndV _it2the temperature of the mixture is lower than the normal temperature,M ₁、M ₂respectively indicating vacuum speed for differentV _it1AndV _it2lower mach number.

According to item 1.2, it is knownT ₀₁、T ₀₂Measured by an atmospheric data system to be a known number;T、M ₁andM ₂is an unknown number.

2.2.3 relation between ground speed and actual vacuum speed under different indicated vacuum speeds

Two different indication vacuum speeds are selected to carry out the GPS forward and reverse flight path method pair flight method, which is shown in figure 2. At this time, according to equation (3) of 2.1.3, the actual vacuum speed, ground speed and wind speed at the two different indicated vacuum speeds satisfy the following relation:

（14）

（15）

wherein the content of the first and second substances,V _d1the ground speed of the forward flight is the ground speed,V _d2in order to reverse the ground speed of the flight,V _t1is the actual vacuum speed of the forward flight,V _t2for the actual vacuum velocity of the reverse flight,V _wind1is the wind speed of the forward flight,V _wind2the wind speed of the reverse flight.

According to the general assumption of airspeed calibration, the addition formula is as follows:

（16）

obtaining two relation formulas of actual ground speed and actual vacuum speed under different indicated vacuum speeds:

（17）

wherein the content of the first and second substances,V _d1the ground speed of the forward flight is the ground speed,V _d2in order to reverse the ground speed of the flight,V _t1is the actual vacuum speed of the forward flight,V _t2the actual vacuum velocity of the reverse fly.V _d1、V _d2Measured separately by GPS, are known numbers,V _t1、V _t2is an unknown number.

2.2.4 different relation expressions of actual ground speed, Mach number and static temperature under indicated vacuum speed

According to the formula (6) of 2.1.4, the relation among the actual vacuum speed, the Mach number and the static temperature under different indicated vacuum speeds is as follows:

（18）

（19）

meanwhile, the coupling type (17), (18) and (19) can obtain:

（20）

wherein the content of the first and second substances,V _d1the ground speed of the forward flight is the ground speed,V _d2in order to reverse the ground speed of the flight,M ₁、M ₂indicating the mach number at different vacuum speeds.V _d1、V _d2Measured separately by GPS, are known numbers,T、M ₁andM ₂is an unknown number.

2.2.5 airspeed calibration algorithm

The five equations of (7), (8), (12), (13) and (20) are combined to solve the Mach number at different indicated vacuum speedsM ₁、M ₂Static pressure ofP ₁、P ₂Static temperatureTI.e. test flight sample points at different indicated vacuum speedsT，P ₁，M ₁) And (a)T，P ₂，M ₂). The two sample points are substituted into the 2.1.4 equation (6) to obtain the actual vacuum speed corresponding to the two different indicated vacuum speed test points, which is shown in table 1.

TABLE 1 actual vacuum Rate corresponding to two different indicated vacuum Rate test points

3 airspeed calibration of full envelope

3.1 same height, different speed

To calibrate for the same altitude, airspeed is calibrated for different indicated vacuum speeds. The test flight and calibration of airspeed can be performed according to the 1-strip and 2-strip methods with different indicated vacuum speeds. The actual vacuum speed corresponding to the same height and different indicated vacuum speed test points can be obtained at the same height H_mIn the airspace, the same non-isotachy test method was used for the test of the 2n (n is a natural number greater than or equal to 1) group, and the calibration results of the test are shown in table 2.

TABLE 2 actual vacuum rate corresponding to the same height, different indicated vacuum rate test points

3.2 full envelope range

To calibrate the airspeed for an actual vacuum speed within the full envelope range (i.e., different altitudes, different indicated vacuum speeds). At different altitudes, airspeed test flight and calibration are carried out according to the method of 3.1 knots, and airspeed calibration results in the range of altitude-speed full envelope are obtained, and are shown in tables 3 and 4.

TABLE 3 airspeed calibration results for altitude-velocity full envelope

TABLE 4 airspeed calibration results for altitude-velocity full envelope

The test height isH ₁ 、H _N And is high atH ₁ ～H _N The invention provides a method for calibrating airspeed of GPS (global positioning system) round-trip non-constant-speed flat flight, which comprises the steps of firstly selecting one airspeed within a full envelope range to be tested, sequentially carrying out multiple groups of non-constant-speed round-trip flight in the same airspeed, obtaining the airspeed calibration result of the same airspeed, and then carrying out airspeed calibration tests of different altitudes within the full envelope range to be tested according to the same methodThe method has the advantages that the progress of the test flight task is guaranteed, the accuracy is guaranteed, and the method has positive significance and profound influence on the design of the subsequent flight control law of the airplane and the safety of flight control.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims (7)

1. A GPS round-trip non-constant speed flat flight airspeed calibration method is characterized by comprising the following steps: the method comprises the following steps:

step a, at a height ofH _m Selecting a starting flying point in a certain directionV _it1Indicating vacuum speed to fly at uniform speed for a certain strokeS ₁ Acquiring first data during flight, the first data including an indication of true airspeedV _it1Total atmospheric temperatureT ₀₁Total pressure ofP ₀₁Speed of the earthV _d1；

Step b, after the return point is reached, the plane is parallel and opposite to the strokeS ₁ In the direction ofV _it2Indicating that the vacuum speed flies at a constant speed, wherein,V _it1is not equal toV _it2And acquiring second data during the flight, the second data including an indication of true airspeedV _it2Total atmospheric temperatureT ₀₂Total pressure ofP ₀₂Speed of the earthV _d2；

Step c, solvingV _it1AndV _it2obtaining a set of airspeed calibration results of back-and-forth fly flight by the airspeed calibration results under two different indicated vacuum speeds;

wherein, solvingV _it1 AndV _it2 the specific procedure for the airspeed calibration results at two different indicated vacuum speeds is as follows:

step A, measuring the total pressureP ₀₁ 、P ₀₂Respectively substituting into formula one to obtain the first partyA program and a second equation;

wherein, the first formula is:

；P ₀is the total pressure of the mixture,Pin order to be at a static pressure,Mis a Mach number of the component (A),ris the specific heat ratio;

the first equation is:

；

the second equation is:

；P ₀₁ 、P ₀₂ respectively indicating vacuum speed for differentV _it1 AndV _it2 the total pressure of the reaction mixture under reduced pressure,P ₁ 、P ₂ respectively indicating vacuum speed for differentV _it1 And V_it2The static pressure of the lower part of the tank,M ₁ 、M ₂ respectively indicating vacuum speed for differentV _it1 AndV _it2 lower Mach number;

step B, the total temperature of the atmosphereT ₀₁、T ₀₂Respectively substituting into the second formula to obtain a third formula and a fourth formula;

wherein, the formula two is:

；T ₀ the total temperature of the atmosphere is the temperature of the atmosphere,Tthe temperature is set to be a static temperature,Mis Mach number;

the third program is:

；

the fourth equation is:

；T ₀₁ 、T ₀₂ respectively indicating vacuum speed for differentV _it1 AndV _it2 the total temperature of the atmosphere below the temperature,T ₁ andT ₂ respectively indicating vacuum speed for differentV _it1 AndV _it2 the temperature of the mixture is lower than the normal temperature,M ₁ 、M ₂ respectively indicating vacuum speed for differentV _it1 AndV _it2 lower Mach number;

wherein, T₁＝T₂＝T_x；T_xIs a static temperature value;

step C, mixing the ground speedV _d1、V _d2Respectively substituting the formula III to obtain a fifth equation;

wherein, the formula three is:

；V _dn andV _dm indicating vacuum speed for different purposesV _itn AndV _itm ground speed for downward forward flight and reverse flight;M _n andM _m is different to indicate the vacuum speedV _itn AndV _itm lower Mach number;

the fifth equation is:

；V _d1 to indicate the vacuum speedV _it1 The ground speed of the lower forward flight,V _d2 to indicate the vacuum speedV _it2 Ground speed of the reverse flight; tx is a static temperature value;M ₁ 、M ₂ respectively indicating vacuum speed for differentV _it1 AndV _it2 lower Mach number;

step D, simultaneously establishing the first equation, the second equation, the third equation, and the fourth equationEquation and a fifth equation; the Mach number can be obtainedM ₁、M ₂(ii) a Static pressureP ₁、P ₂And static temperatureTI.e. test flight sample points at different indicated vacuum speedsT，P ₁，M ₁) And (a)T，P ₂，M ₂）；

Step E, substituting the two sample points obtained in the step D into a formula seven to obtain two different actual vacuum speeds, and obtaining the vacuum pressureV _it1AndV _it2two different airspeed calibration results at indicated vacuum speeds;

wherein, the formula seven is:

(ii) a Wherein the content of the first and second substances,V _tin order to realize the vacuum speed,Tthe temperature is set to be a static temperature,Mis mach number.

2. The method according to claim 1, wherein in step b, the distance between the GPS and the non-constant speed flat flight is measured along the pathS ₁ And returning the original path to test.

3. The GPS round-trip non-constant velocity flat flight airspeed calibration method according to claim 1, wherein the time interval between step b and step a is controlled to be within 20 min.

4. The method according to claim 3, wherein the time interval between step b and step a is 5-20 min.

5. The GPS round-trip non-constant-velocity flat flight airspeed calibration method according to claim 1, wherein the vacuum velocity, the total atmospheric temperature and the total pressure are measured by an atmospheric system, and the ground velocity is measured by a GPS device.

6. GPS roundtrip non-constant speed flat flight according to any of claims 1-5The airspeed calibration method is characterized in that after a set of back-and-forth flying flights of the step a and the step b are completed, the flying speed is changed, and the flying speed is at the same height according to the same method of the step a and the step bH _m And c, performing multiple groups of back-and-forth fly-to-fly flights, and calculating the airspeed calibration result of each group of back-and-forth fly-to-fly flights according to the same method in the step c, so as to obtain the airspeed calibration result at the same altitude.

7. The method as claimed in claim 6, wherein after the calibration of the airspeed at a certain altitude, the altitude is measured according to the same methodH ₁ 、H _N And is high atH ₁ ～H _N The airspeed calibration results of a plurality of height airspaces within the range of obtaining the height from the groundH ₁ ～H _N And (5) calibrating the airspeed within the full envelope range.

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