RU2396569C1 - Method of determining aerial parametres in flight tests of aircraft flying at high angle of attack - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: method involves measurement of aerial parametres and angular parametres of the position of an airplane in space using standard equipment, measurement of trajectory parametres, achieving probe and test modes and post-flight processing of flight test results. The probe mode is achieved at the beginning of each test mode on high angle of attack with heading angle close to the heading angle of the corresponding test mode. For the test mode on high angle of attack, true values of air speed are calculated from the condition of invariance of the value and direction of wind speed when probe and test modes are achieved. Based on trajectory measurements and true calculated values of temperature and static pressure obtained for the probe mode, the actual ambient temperature and static pressure are calculated in the test mode. Using the obtained true values of air speed, temperature and static pressure, the true Mach number, overall pressure and calibrated air speed are calculated. True calculated values of the angle of attack α and the gliding angle β are determined from the true values of air speed and measurements of angular parametres. The obtained true calculated values of parametres are compared with parametres measured using standard onboard equipment. A set of similar modes is used to construct an expectation function of calibrating curves for standard air pressure receivers and flow angle sensors. Further, the aerial parametres measured by standard onboard equipment are used to accurately determine true values of aerial parametres in flights at high angle of attack taking into account the determined calibrated curves.

EFFECT: more accurate determination of aerial parametres in flight tests of aircraft flying at high angle of attack.

5 dwg, 1 tbl

Description

The invention relates to technical physics, measuring and aeronautical engineering, and in particular to flight parameter meters of an aircraft (LA), and can be used in flight tests of an aircraft to determine the actual values of air parameters and evaluate means for determining the air parameters of an aircraft.

The invention is focused on testing aircraft equipped with modern flight and navigation systems with low delay coefficients in the pressure transmission paths (λ _s ≤0.1).

In practice, flight tests of aircraft use various methods and approaches to solving the problem of determining air parameters at large angles of attack. Methods using standard receivers and indirect methods using external trajectory measurements and information on atmospheric state parameters can be distinguished.

In methods using reference receivers, the air parameters are determined by the values of the parameters measured by the standard means (see AC-21-40 (0), Measurement of airspeed in light aircraft - certification requirements, 2005). The main task in the implementation of the methods is the standardization of the reference tools themselves.

Technical difficulties arise due to the need to remove receivers from the aerodynamic influence zone of the aircraft. The implementation of the methods involves the study of the installation of reference facilities on an airplane, and the equipping of aircraft with special technological devices. Due to the difficulty of completely eliminating the aerodynamic effect of the aircraft on measuring air parameters, the application of the methods requires special studies for each type of aircraft to evaluate the flow perturbation in the area of the placement of the reference means.

Methods using reference receivers are widely used in flight tests of aircraft abroad. By AC-25-7A EASA, in support of testing the aircraft under braking conditions with access to large angles of attack, it is prescribed to use a nose bar with an air pressure receiver (LDPE) to determine stall speeds.

на режимах маловысотного полета h_отн<500 м, определение зависимости погрешности восприятия статического давления ПВД в полном эксплуатационном диапазоне изменения скорости (числа М) и угла атаки, где Δр=Р-Р_ист - прототип.Among indirect methods, the “Method for determining the aerodynamic errors of air pressure receivers in flight tests of an aircraft” is known, RF patent No. 2177624, IPC G01P 21/00, G01P 5/14, including the implementation of horizontal platforms (GP) at given heights, speeds (Mach numbers ) and angles of attack α, measuring the current values of the perception of static pressure P, geometric height h, air temperature T, determining the change in atmospheric pressure with a change in geometric altitude, determining the dependence of the perception error I am the LDPE static pressure on the Mach number and angle of attack

at low altitude flight modes h _rel <500 m, determining the dependence of the error in the perception of static pressure of the LDPE in the full operational range of changes in speed (number M) and angle of attack, where Δр = Рr Р _ist is a prototype.

This method allows you to determine the air parameters only in the horizontal steady flight modes.

The technical result to which the invention is directed is to increase the accuracy of determining air parameters in flight tests of aircraft at large angles of attack.

To achieve the named technical result in the proposed method, including the operation of measuring air parameters and angular parameters of the position of the aircraft in space by standard means of the aircraft, measuring the path parameters of the flight, performing sounding flight modes in the form of a horizontal steady flight (GP) without sliding, after-flight processing of the results of flight tests , determining the true values of static, total pressures, calculating the true values of the Mach number, the temperature of the outside air, ozdushnoy probing rate modes, sounding mode is performed at the beginning of each test mode at high angles of attack with course angle close to the course angle corresponding test mode. Using the measured ground speed and heading angle, taking into account the obtained airspeed values, the wind speed vector is determined in the sounding mode, for the test mode at large angles of attack, the true airspeed values V _{in are} calculated from the conditions of constant value and Direction of wind speed during sounding and test modes. Based on the trajectory measurements and the true calculated values of temperature and static pressure obtained for the sounding mode, the true outdoor temperature and static pressure P _{c are} calculated in the test mode using the atmospheric static equation, then the true air speed, temperature and static pressure are calculated true Mach number, total pressure P _p , indicator earth velocity V _iз . The true calculated values of the angles of attack α and slip β are determined from the true values of air speed and measurements of angular parameters.

The obtained true calculated values of the parameters are compared with the parameters measured using standard on-board means, the relative aerodynamic error in speed is determined

коэффициенты статического

static coefficients

полного

full

pressures and dependencies

α = f (M _ISM , α _ISM , δ), β = f (M _ISM , β _ISM , δ),

where V _CR - measured instrument speed, q - measured velocity head, δ - configuration of the aircraft, M _ISM , α _ISM , β _ISM - measured values of the Mach number, angle of attack and slip. Based on the totality of such modes, mathematical expectations of calibration dependencies for standard LDPEs, aerodynamic angle sensors (DAUs) are built. Further, by measuring air parameters using standard on-board means, taking into account certain calibration dependencies, the true values of air parameters in flights at large angles of attack are specified.

This makes it possible to increase the completeness and accuracy of determining calibration dependences for LDPE, DAU and, accordingly, the accuracy of determining air parameters in flight tests of aircraft.

The calculation of the true pressure by the method specified in the prototype is performed in horizontal flight, whereas in the proposed method, the calculation is performed for flying at large angles of attack.

The proposed method is illustrated in the following drawings.

Figure 1-5 presents the results for test modes of braking with access to large angles of attack.

Figure 1 shows the dependence of the relative aerodynamic error in speed on the measured angle of attack.

Figure 2 shows the dependence of the coefficient of total pressure on the measured angle of attack.

Figure 3 shows the dependence of the coefficient of static pressure on the measured angle of attack.

Figure 4 shows the change in instrument and indicator earth speeds during the test mode.

Figure 5 shows the relationship between measured and true estimated angles of attack.

The method is as follows.

и полное

давления по измеряемым значениям статического Р_{c изм}, полного Р_{п изм} давлений с учетом градуировочных зависимостей ПВД:In probing mode, true static

and complete

pressure according to the measured values of static R _{c ISM} , full R _{p ISM} pressure taking into account the calibration dependences of the LDPE:

- градуировочные зависимости ПВД, полученные в горизонтальном полете, ΔP_c=Р_{c изм}-Р_c, ΔP_п=Р_{п изм}-Р_п Where

- calibration dependences of the LDPE obtained in a horizontal flight, ΔP _c = P _{c ISM} -P _c , ΔP _p = P _{p ISM} -P _p

M _ISM - measured Mach number;

α _ISM - measured angle of attack;

δ is the configuration of the aircraft.

Then, in the probing mode, the values of the Mach number M _s and air speed are determined according to the formulas:

where R is the universal gas constant;

g is the acceleration of gravity;

k is the adiabatic exponent;

- температура наружного воздуха на момент выполнения зондирующего режима, определяемая из соотношения:

- the outdoor temperature at the time of the sounding mode, determined from the ratio:

where T _T is the braking temperature measured by the on-board receiver;

N is the airborne receiver quality factor.

Knowing the value of the air speed, the components of the wind speed U _x and U _z in the probing mode can be determined from the relations:

where ψ is the course angle of the sounding mode;

W _x , W _z are projections of the ground speed vector.

It is assumed that the wind velocity vector lies in the horizon plane and does not change over time.

Performing a probing mode without sliding immediately before the test mode:

- provides the determination of the basic parameters of the atmosphere (static pressure, temperature, wind velocity vector) necessary to solve the problem, with small errors due to correction of pressure perception errors in the sounding mode;

- significantly reduces the influence of random factors (spatio-temporal variability of atmospheric parameters) on determining the actual values of air parameters and calibration dependences for LDPE in test modes.

Measurement of the angular parameters of the position of the aircraft in space, the trajectory parameters of the flight together with the obtained values of the atmospheric parameters allow us to obtain a solution to the problem of determining the mathematical expectation of calibration dependencies on the main influence factors.

With known wind characteristics U _x , U _{z, the} air speed V _in at large angles of attack is determined from the relation:

where W _y is the component of the speed of the aircraft, the normal plane of the horizon.

The outdoor temperature in test mode is determined by the formula

where Δh is the difference between the current geometric height and the height of the sounding mode;

τ = 0.0065 deg / m.

Then, from the ratio (3) using the obtained values of the outdoor temperature and air speed in the test mode, the number M is determined.

The true value of the static pressure in the test mode is determined by recalculation from the sounding mode using the equation of atmospheric static:

The true value of the total pressure is calculated on the basis of the true values of the static pressure obtained from relation (9) and the number M:

With known values of static and total pressure, you can calculate the values of the indicator V _i and indicator earth V _iz speeds (see figure 4) according to the formulas:

where P _din = P _p -P _c - dynamic pressure;

α ₀ is the speed of sound at H = 0 in a standard atmosphere;

P ₀ - atmospheric pressure at H = 0 in a standard atmosphere.

To determine the true angles of attack and slip, it is necessary to calculate the projection of air speed on the connected axis of the aircraft V _x1 , V _y1 , V _z1 according to the formulas:

where ϑ is the pitch angle;

γ is the angle of heel.

Taking into account relations (13) - (15), we obtain the expressions for the true angles of attack α and slip β:

Taking into account the true values obtained from the relations (9), (10), (12), (16), (17), calibration curves are determined at large angles of attack in the form of relative errors

as shown in figure 1,

где ΔV_a=V_пр-V_iз, V_пр - измеренная приборная скорость, ΔР_c=Р_{c изм}-Р_c и т.д.

where ΔV _a = V -V _{Ih ave,} V _ave - measured airspeed,? P _c = P _c -P _{edited c} etc.

and the dependences α = f (M _ISM , α _ISM , δ), see FIG. 5, β = f (M _ISM , β _ISM , δ).

и

представленные на фиг.2, 3, с использованием соотношений:Then the dependencies are determined

and

presented in figure 2, 3, using the ratios:

The obtained calibration dependences are then used to refine the measured air parameters using relationships of the form (1).

For example, for aircraft braking modes with speeds of 340 ÷ 170 km / h at an altitude of 5000 ÷ 6000 m in the range of measured angles of attack of 1 ÷ 42 degrees, the proposed method calculated the true values of air parameters, constructed calibration curves for LDPE and DAE, which are used to refine the values air parameters in flight tests of aircraft in braking modes with access to large angles of attack.

The ranges of flight parameters during braking with access to large angles of attack are shown in table 1. The results are shown in figures 1-5.

Table 1 Options Units Range of parameter change in braking modes from before M - 0.2 0.4 V _ave, V _Ih Km / h 170 340 V _in m / s 60 125 q mmHg. 10 40 P _c mmHg. 320 390 P _p mmHg. 340 415 α _meas hail one 42 β hail -four 3

Table 1 continued γ hail -3 3 ϑ hail four 23 T _nv ° C -47 -38 N M 5000 6000 U _x , U _z m / s -7 eleven

Braking modes are performed in take-off, flight and landing configurations. Figure 1-3, 5 shows the calibration dependences, common for all configurations 8. Calibration dependencies are determined in the form of functions of several variables, namely M _ISM , α _ISM , β _ISM . In figures 1-3, 5 calibration curves are shown only depending on the measured angle of attack.

на режиме горизонтального полета, 5 - зависимость

на больших углах атаки.Figure 1 shows the calibration dependence of the relative error in determining the speed, determined in the horizontal flight and braking modes with access to large angles of attack (the results of flight tests at large angles of attack are indicated by +). Figure 1 presents: 1 - values of the angle of attack, 2 - values of the relative error in determining the speed, 3 - experimental data, 4 - dependence

in horizontal flight mode, 5 - dependence

at large angles of attack.

на режиме горизонтального полета, 8 - зависимость

на больших углах атаки.Figure 2 shows the calibration dependence of the total pressure coefficient, determined in the horizontal flight and braking modes with access to large angles of attack (the results of flight tests at large angles of attack are indicated by +). Figure 2 presents: 1 - values of the angle of attack, 6 - values of the coefficient of total pressure, 7 - dependence

in horizontal flight mode, 8 - dependence

at large angles of attack.

на режиме горизонтального полета, 11 - зависимость

на больших углах атаки.Figure 3 shows the calibration dependence of the static pressure coefficient, determined on the horizontal flight and braking modes with access to large angles of attack (the results of flight tests at large angles of attack are indicated by +). Figure 3 presents: 1 - values of the angle of attack, 9 - values of the coefficient of static pressure, 10 - dependence

in horizontal flight mode, 11 - dependence

at large angles of attack.

Figure 4 shows the change in instrumental indicator earth speed during the test mode. Figure 4 presents: 12 - the runtime of the mode, 13 - the values of the instrumental and indicator earth speeds, 14 - the curve of the change in the instrument speed, 15 - the curve of the change in the indicator earth velocity.

Figure 5 shows the functional dependence of the true estimated angle of attack from the measured angle of attack. Figure 5 presents: 1 - values of the angle of attack, 16 - values of the true estimated angle of attack, 17 - dependence curve.

Thus, the proposed method allows to determine the values of the atmospheric parameters - temperature, pressure, wind speed, determine the air parameters in test modes, determine the calibration dependences for air pressure receivers and aerodynamic angle sensors, reduce the influence of random factors of variability of atmospheric parameters on the error in determining air parameters, increase the accuracy of determining air parameters when flying at large angles of attack.

Claims (1)

A method for determining air parameters in flight tests of an aircraft (LA) at large angles of attack, including measuring air parameters and angular parameters of the position of the aircraft in space using standard LA means, measuring flight path parameters, performing sounding flight modes in the form of a horizontal steady flight (GP) without slip, post-flight processing of flight test results, determination of true values of static, total pressures, calculation of true values of Mach number, tempo outside air, airspeed in sounding modes, characterized in that the sounding mode is performed at the beginning of each test mode at large angles of attack with a heading angle close to the heading angle of the corresponding test mode, according to measurements of ground speed and heading angle, taking into account the obtained air values speeds in the sounding mode determine the vector of wind speed for the test mode at large angles of attack by measuring the ground, vertical speeds and the calculated wind speed calculate the true values of the air velocity V _in from the condition of the magnitude and direction of the wind speed during the execution of the probing and test modes, based on the trajectory measurements and the true calculated values of temperature and static pressure obtained for the probing mode, in the test mode, calculate the true outdoor temperature and _with the static pressure P static atmosphere using the equation, then the obtained values of the true air speed, temperature and stat critical pressures calculated true Mach number, the total pressure P _p, the calibrated airspeed V _Ih at true values of airspeed and measurements of the angular parameters determine the true design values α and sliding β angles of attack received true calculated parameter values are compared with the parameters measured by the standard airborne means, determine the relative aerodynamic error in speed

, the coefficients of static

full

pressures and dependences α = f (M _ISM , α _ISM , δ), β = f (M _ISM , β _ISM , δ), where V _CR is the measured instrument speed, q is the measured pressure head, δ is the configuration of the aircraft, M _ISM , α _ISM , β _ISM — the measured values of the Mach number, angle of attack and slip, using the aggregate of similar modes, build the mathematical expectations of the calibration dependencies for standard air pressure receivers (LDPE), aerodynamic angle sensors (DAU), then using airborne measurements taking into account certain calibration dependences of ut chnyayut the true values of the parameters in the air flying at high angles of attack.

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