RU2474863C1 - Method of changing flight altitude of aircraft - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: according to the method of changing the flight altitude of aircraft, transitioning from the current flight altitude to the desired altitude is carried out with constant absolute speed. The path of transitioning to another altitude is a sinusoidal half-period. The angle between the vertical and the tangent to said path, which passes at its initial and final points lying on the current and desired altitudes, respectively, is equal to 90 degrees. The path of transitioning from the current flight altitude to the desired altitude can be selected from multiple similar paths distinguished by the length of the half-period.

EFFECT: minimising overload on the vertical axis.

4 cl, 20 dwg

Description

The invention relates to the field of automatic control systems for aircraft, in particular to methods of piloting in a vertical plane.

To transfer the aircraft to a different altitude, at present, it is generally accepted as a method according to which the transition from the current flight altitude to the desired altitude is carried out along a path including three sections. The first section of the trajectory is an arc of a circle connecting the horizontal flight line at the current height with the second section, which has the form of a straight line, inclined to the horizontal. The third section of the trajectory is an arc of a circle opposite the convex arc of the first section, and matches the second section of the trajectory with the horizontal flight line at the desired height. This method is disclosed in detail, for example, in patent publication GB 1270754 (A), G05G 1/06, 04/12/1972.

A factor explaining the prevalence of the known method is that on the longest second section of the trajectory, the plane moves uniformly in a straight line. Thus, to maintain the trajectory in the second section, it is not necessary to change the position of the steering surfaces or change the engine thrust, which simplifies the aircraft control algorithms.

However, the known method of moving the aircraft to another altitude has a significant drawback. When changing sections of the trajectory of the known method in a short period of time, the operating mode of the engines and the position of the steering surfaces change, which means that the aircraft is subjected to significant overloads, which negatively affects the comfort of passengers.

The objective of the invention is to ensure smooth movement of the aircraft in a vertical plane.

To solve this problem, a method for changing the flight altitude of an aircraft is proposed, in which the transition from the current flight altitude to the desired altitude is carried out with a constant absolute speed along the trajectory, which is a half-wave of a sinusoid. In this case, the angles between the vertical and the tangents to the indicated trajectory, drawn at its starting and ending points located at the current and desired heights, respectively, are 90 °.

In the preferred case of the invention, the trajectory of the transition from the current flight altitude to the desired altitude is selected from a variety of similar trajectories that differ in half-length.

In the particular case of the invention, the plurality of trajectories comprises a trajectory in which the fuel consumption of the aircraft has a minimum value.

In another particular case of the invention, the plurality of paths comprises a path providing a minimum transition time from the current flight altitude to the desired altitude.

The technical result achieved by using the invention is to minimize overload on the vertical axis.

The implementation of the invention will be explained with reference to the figures:

figure 1 and figure 2 - calculated trajectories practiced by the plane when moving from a height of 10,000 m to a height of 4,000 m, respectively, known and proposed methods;

figure 3 and figure 4 - the vertical components of the overload experienced by the Tu-204CM aircraft with the specified reduction, carried out respectively by the known and proposed methods;

figure 5 and figure 6 - horizontal components of the overload experienced by the TU-204CM aircraft with the specified reduction, carried out respectively by the known and proposed methods;

Fig.7 and Fig.8 - the vertical speed of the Tu-204CM aircraft with the specified reduction, carried out respectively by known and proposed methods;

Fig.9 and Fig.10 - the absolute speed of the Tu-204CM aircraft with the specified reduction, carried out respectively by known and proposed methods;

11 and 12 - the calculated trajectory of the aircraft, implemented upon transition from a height of 400 m to a height of 6400 m, respectively, by known and proposed methods;

Fig.13 and Fig.14 are the vertical components of the overloads experienced by the TU-204CM aircraft at the indicated lift, carried out respectively by the known and proposed methods;

Fig and Fig - horizontal components of the overload experienced by the TU-204CM aircraft at the specified lift, carried out respectively by the known and proposed methods;

Fig.17 and Fig.18 - the vertical speed of the Tu-204CM aircraft at the specified lift, carried out respectively by known and proposed methods;

Fig.19 and Fig.20 - the absolute speed of the Tu-204CM aircraft with the specified lift, carried out respectively by known and proposed methods.

A comparison of the known and proposed methods for changing the height will be carried out by analyzing the parameters of the Tu-204CM aircraft when it implements these methods.

Figure 1 shows the calculated trajectory of the aircraft when it is reduced from the current altitude of 10,000 m to the desired altitude of 4,000 m and the implementation of the known method of transition to another altitude. This trajectory is calculated by the on-board computer and is worked out by the aircraft as a result of controlling the position of the steering surfaces and engine thrust using an automatic control system (ACS). The actual trajectory of the aircraft is somewhat different from the calculated one, however, in the context of this application, these differences are not significant.

As shown above, the trajectory of the known method is characterized by the presence of three sections. The first and third sections are oppositely convex arcs of circles, and the second section is a straight line, inclined to the horizontal. Fulfilling the trajectory by a known method, the aircraft experiences overload, which has a vertical component N _y and a horizontal component N _x (hereinafter, vertical and horizontal overloads, respectively). Overload refers to the ratio of the resultant force acting on an airplane to gravity. In the conditions of uniform rectilinear flight, N _y = 1, N _x = 0.

When switching from one part of the trajectory according to the known method to another, the steering surfaces and engine thrust control algorithm changes dramatically, which causes a significant overload of N _y , the bursts of which are visible in FIG. 3. Overload N _x is also observed (Fig. 5), however, horizontal overload practically does not affect flight comfort - vertical overload causes the thrill of discomfort for passengers.

In Fig.7, you can also see areas with a stepwise changing vertical speed.

From figure 9 it follows that as a result of the reduction, the aircraft did not restore its original absolute speed and additional actions are required to correct it. Under the absolute speed of the aircraft in the context of this application refers to its speed relative to the ground.

It should be noted that by changing the distance over which the known method is implemented, it is possible to optimize the known method of changing heights for various tasks, including decrease in vertical overload. However, an increase in the indicated distance is not always possible from the point of view of flight rules, in addition, this approach will only allow a slight decrease in vertical overload, while delaying the phase of height change uncomfortable for passengers.

Figure 2 shows the calculated trajectory of the aircraft when it decreases from the current altitude of 10,000 m to the desired altitude of 4,000 m and the implementation of the proposed method of transition to another altitude. The calculated trajectory has the form of a sinusoid and is based on the following equation:

, где

where

H ₁ - current height, for the considered example 10,000 m,

H ₂ - the desired height, for the considered example 4000 m,

x is the distance traveled from the zero point - the beginning of the implementation of the method, is a variable and takes values from 0 to L,

L is the longitudinal distance over which a change in height is carried out, for the considered example 12000 m, is an optimization parameter.

An essential condition of the proposed method of changing altitude is the invariance of the absolute speed of the aircraft.

As follows from equation (1), the trajectory according to the proposed method is described by the cosine function and has the form of a half-period of a sinusoid. It is important that the trajectory of the proposed method is smooth, i.e. it does not have sections described by various functions, which means it allows the use of a single control algorithm. To work out such a trajectory, a constant smooth change in the position of the steering surfaces and engine thrust over the entire specified longitudinal distance is required, which is not a problem for modern automatic control systems.

The plane begins to move along the trajectory of the proposed method of changing altitude, moving rectilinearly and horizontally at the current altitude. In the same position, the aircraft finishes moving along the trajectory, reaching the desired height. Thus, the angles between the vertical and the tangents to the given trajectory, drawn at its start and end points, are 90 °.

As can be seen in figure 4, the vertical overload in this case is almost equal to unity, and the horizontal overload (Fig.6) is not higher than that of the known method. The vertical speed shown in Fig. 8 changes without jumps, and the absolute speed (Fig. 10) is kept constant throughout the entire process of changing the height.

It should be noted that in the presented example, the descent trajectory of the aircraft according to the proposed method corresponds to more severe conditions than the descent trajectory of the known method — this can be seen by the distance over which the altitude was changed (12,000 m and 18,000 m, respectively). However, even under these conditions, as a result of using the proposed method, the vertical overload is close to unity (Fig. 4), which will positively affect the comfort of aircraft passengers.

11-20 illustrate the known and proposed method for the case of lifting the aircraft from the current altitude of 400 m to the desired altitude of 6400 m. All of the above reasoning and conclusions are fully valid. The trajectory of ascent according to the proposed method is described by equation (1), has the form of a half-cycle of a sinusoid and is performed by an airplane without changing modes while maintaining a constant absolute speed.

From Fig.14 it follows that the vertical overload during the implementation of the proposed method and in this case is close to unity, in contrast to the known method (Fig.13).

Thus, the proposed method of changing the height of the aircraft solves the problem of minimizing the increment of vertical overload, both when reducing and when climbing, providing comfortable conditions for passengers.

However, the proposed method allows you to optimize the trajectory of the change in height depending on specific tasks. The following can be considered as such tasks: ensuring the minimum rise time to the desired height; minimizing fuel consumption, etc. For each task, taking into account the design limitations of the aircraft, the on-board computer calculates the longitudinal distance L, over which it is advisable to change the flight altitude, i.e. half-wavelength of a sine wave. It is important at the same time that each trajectory of a change in height from the whole set of possible trajectories is characterized by a vertical overload value close to unity and is comfortable for passengers.

Claims (4)

1. The method of changing the flight altitude of the aircraft, in which the transition from the current flight altitude to the desired altitude is carried out with a constant absolute speed along the path, which is a half-cycle of a sinusoid, and the angle between the vertical and the tangents to the specified path, carried out at its start and end points, located respectively at the current and desired heights, is 90 °. 2. The method according to claim 1, characterized in that the trajectory of the transition from the current flight altitude to the desired altitude is selected from a variety of similar trajectories that differ in half-length. 3. The method according to claim 2, characterized in that the set of trajectories contains a trajectory, during which the fuel consumption of the aircraft has a minimum value. 4. The method according to claim 2, characterized in that the plurality of trajectories comprises a trajectory providing a minimum transition time from the current flight altitude to the desired altitude.

Images