RU2486596C1 - Method of determining and indicating rotor approximation to vortex ring conditions at single-rotor helicopter pre-landing maneuvers - Google Patents

Abstract

FIELD: aircraft engineering.

SUBSTANCE: method comprises measuring incident air flow nearby rotor by air pressure receiver fitted at blade tip. Helicopter vertical speed, pitch and wobble plate lengthwise deflection are measured. Rotor angle of attack, tangential and normal components of incident airflow velocity in real time are computed. Measured also are incident airflow velocity nearby rotor at its decrease due to oncoming inductive velocities created by helicopter vortex trace and axial velocity are measured. Measured magnitudes are compared to limiting parameters of cortex ring zone. At helicopter descent at the rate over 3 m/s and tangential velocity nearby rotor lower than 45-50 km/h, pilot is warned about approach to said rig zone by light and voice signals. Besides, instruction on decrease in pitch to landing magnitude is sent to control system and, at a time, vertical rate of helicopter descent is stabilised to not over 2.0 m/s.

EFFECT: higher accuracy.

2 cl, 4 dwg, 1 ex

Description

The invention relates to aviation, in particular to the field of rotor aerodynamics (HB) of a single-rotor helicopter, in particular to a method for determining and signaling the rotor approaching the zone of “vortex ring” modes on pre-landing maneuvers.

State of the art

It is known that at helicopter pre-landing maneuvers, the helicopter enters the “vortex ring” with an unexpected and sharp loss of flight altitude, which leads to accidents and catastrophes of helicopter equipment due to inevitable rough landings. Jackson W. Helicopter Theory. - M.: Mir, 1989, p. 108.

A control system is known for preventing a rotorcraft from entering the “vortex ring”, which compares the air speed of the incoming flow and the current helicopter lowering speed in the selected flight mode, generates signals in response to entering the “vortex ring” flight mode and generates a vibrating cycle to contain the rotor disk from entering the “vortex ring”, patent No. SU 2006/0006279 A1, 2006. However, this maneuver may affect the flight path.

A known method for detecting and signaling the approach to the "vortex ring" of a rotorcraft, comprising measuring in preliminary flight tests using a system of air flow velocity meters with significant errors and the associated tangential and normal components of the air velocity near the rotor, the formation of these paired the values on the abscissa and ordinates of the diagram of the boundaries of the appearance of the zone of regimes of the “vortex ring” of the rotorcraft, comparison during flight the stifling speed of the helicopter and the associated vertical speed with the boundary parameters of the vortex ring zone according to the diagram and, when the parameters correspond to the vortex ring mode, the formation of a warning signal. Air pressure receivers (LDPEs) are mounted opposite the two shoulders of the rotary arm mounted on the rod above the rotor of the rotorcraft (US Pat. No. 7907066 B2, 2011, WO 2009074745 A1).

However, in the known method, the tangential and normal (axial) free air velocities near the HB are determined without taking into account their dependence on the angle of attack of the HB, calculated by the pitch angle, the angle of deviation of the swashplate in the longitudinal direction, the ratio of the vertical speed of the helicopter to the horizontal speed of the air flow near the HB , which significantly reduces the accuracy when determining the zone of modes of the "vortex ring" and the moment the alarm is triggered, increasing the likelihood of flight accidents. In addition, the complexity of the HB design reduces reliability and affects the flight path during pre-landing maneuvers.

The present invention is aimed at achieving a technical result, which consists in increasing the safety of helicopter flights on pre-landing maneuvers.

To obtain the indicated technical result in the method of determining and signaling the rotor (HB) approaching the zone of the “vortex ring” modes on pre-landing maneuvers of a single-rotor helicopter, which includes measurement during preliminary flight tests using a translational speed measurement system taking into account wind and vertical helicopter speed at modes to reduce _cf. H = 1000 m, and this pair of values on the axes of abscissa and ordinate build boundaries diagram occurrence "vortex ring" of the helicopter (4), the comparison the course of the pre-landing maneuver of the air flow velocity and the associated vertical velocity with the boundary parameters of the zone of the vortex ring mode, the determination and signaling of approaching the vortex ring mode and the formation of a warning signal, while the air flow velocity near the rotor is measured using air pressure receiver (LDPE) installed in the tip of the blade. On the pre-landing maneuvers of the helicopter, the vertical speed of the helicopter, the pitch angle of the helicopter, the angle of deviation of the swash plate in the longitudinal direction are measured, and the angle of attack of the HB, the tangential and normal components of the air flow velocity in the current time are calculated according to the following formulas:

$$\alpha =\vartheta +\phi sa\mathrm{to}l+D\mathrm{one}\delta \mathrm{at}+arctg3.6\times Vy/Vx,(\mathrm{one})$$

where α is the angle of attack of the HB, in degrees;

ϑ is the pitch angle of the helicopter, in degrees;

φzakl - the angle of the spell (tilt forward) of the axis of rotation of the HB, in degrees;

δв - angle of deviation of the swashplate in the longitudinal direction, in degrees;

D1 - gear ratio from the swash plate to the resultant traction HB;

Vy - the vertical speed of the helicopter, in m / s;

Vx is the horizontal speed of the air flow near the HB, in km / h;

determine the total tangential velocity in the plane of the ends of the blades:

$$Vt=Vx\cos \alpha +Vy\sin \alpha (2)$$

and total normal (axial) speed:

$$Voc=Vy\cos \alpha +Vx\sin \alpha (3)$$

The tangential velocity of the incoming flow near the rotor when it decreases (Figs. 1 and 2) due to the action of counter inductive velocities created by the vortex wake of the HB, and the axial (normal) velocity is compared with the boundary parameters of the vortex ring zone. When reducing the helicopter at a speed of more than 3 m / s and flying at a speed of less than 45-50 km / h, the pilot begins to signal the approach to the zone of the "vortex ring" intermittent light and speech signals (figure 3), as well as in the automatic control system ( Self-propelled guns) send a command to reduce the pitch angle to a landing value that excludes touching the safety fifth of the underlying surface, and at the same time stabilize the helicopter's vertical speed of descent to a value of not more than 2.0 m / s. In addition, when entering the "vortex ring" mode, the alarm signals are amplified (Fig. 4), which requires the pilot to immediately increase the flight speed and, if there is an engine power reserve, try to reduce the vertical speed after acceleration to Vx = 40 km / h.

Thus, the technical result is achieved by clarifying the boundaries of the appearance of the “vortex ring” by taking into account in the calculations the total tangential velocity in the plane of the ends of the blades and the total axial velocity of the air flow depending on the angle of attack of the airfield, calculated on the basis of the sum of the parameters (ϑ + φcl. + D1δv + arctan 3.6 × Vy / Vx).

The proposed method is illustrated in figures 1-4.

Figure 1 shows the calibration characteristics of the progressive low speed indicator of the helicopter - Vx in the climb and descent modes of the Mi-8 helicopter at an average altitude of 1000 m, where (1) is the dependence of the translational speed of the helicopter on the speed of decline Vy when kept by the indicator Vx = 100 km / h, (2) - the dependence of the translational speed of the helicopter on the vertical speed - Vy at Vx = 50 km / h, (3) - the dependence of the translational speed of the helicopter on Vy at Vx = 15 km / h, (4) - the dependence of the translational helicopter speed from Vy at Vx = 0.

Figure 2 presents the dependence of air speed near the main rotor, near the standard LDPE and the truth according to measurements of the ground speed according to the movie theodolite stations (CTS) taking into account the wind speed W, equal to 4 m / s, in the horizontal braking mode of the Mi-8 helicopter, 20 m high:

5 - air speed near NV Vx versus time according to the readings of the indicator of a helicopter speed meter (VIS) operating from LDPE on the HB - blades;

6 - the dependence of speed on time according to the CCC taking into account the wind speed W;

7 - the dependence of speed on time according to the indications of the indicator of the speed indicator US-250, operating from LDPE on the fuselage of the helicopter;

8 - the boundary zone of the "vortex ring" at the translational speed of the helicopter.

Figure 3 shows a block diagram of a device for warning a pilot about approaching and falling into a vortex ring zone, containing a unit for processing actual measurements and calculating current values of Vt and Voc (9), connected by inputs to the outputs of measuring instruments of vertical helicopter speed, horizontal air speed flow near the HB, the pitch angle of the helicopter, the angle of deviation of the swashplate in the longitudinal direction; a database block (10) representing, by means of a diagram in the system of axes associated with the HB, the boundary parameters of the zone of the “vortex ring” mode, and the abscissa and ordinates of which correspond to the tangential and normal components of the air velocity near the HB, with the output (10) and the output of the actual measurement processing unit (9) is connected to the inputs of the comparison unit (11) of the current values of Vt and Voc with boundary parameters for detecting a pair of tangential and axial velocity components approaching the HB to the zone of the “vortex ring” mode in the current flight time and signal generation, the output of which is connected to the input of the pilot warning unit about approaching the “vortex ring” zone with the light (12) and with the speech signal (13) and self-propelled guns (14).

Figure 4 shows the boundaries (16) of the zone of modes of the "vortex ring" (15) for a single-rotor helicopter and shows the modes without showing signs of a "vortex ring" (17)

The method is as follows.

During preliminary flight tests in the helicopter lowering modes at an average altitude of 1000 m, the path speed of the helicopter is recorded using external trajectory measurements and its air speed and vertical speed are determined taking into account wind speed. Based on these paired values, taking into account the criterion for increasing the helicopter's decrease speed due to an increase in the required engine power, diagrams of the boundaries of the “vortex ring” occurrence are constructed (Fig. 4) and entered into block 10 in Fig. 3.

At pre-landing maneuvers with the help of LDPE installed in the tip of a single-rotor helicopter blade connected to a low-speed meter, the air speed of the incoming flow near the main rotor is measured. In addition, measure the vertical speed of the helicopter, the pitch angle of the helicopter, the angle of deviation of the swashplate in the longitudinal direction to calculate the angle of attack of the HB. In the current time, the angle of attack of the HB, the tangential and normal components of the airflow velocity of the incoming flow in the calculator of the block, (9) of block 9 in figure 3 of the pilot warning device about approaching and falling into the vortex ring zone are calculated according to the following formulas:

$$\alpha =\vartheta +\phi sa\mathrm{to}l+D\mathrm{one}\delta \mathrm{at}+arctg3.6\times Vy/Vx(\mathrm{one})$$

α is the angle of attack of the HB, in degrees;

ϑ is the pitch angle of the helicopter, in degrees;

φzakl - the angle of the spell (tilt forward) of the axis of rotation of the HB, in degrees;

δв - angle of deviation of the swashplate in the longitudinal direction, in degrees;

D1 - gear ratio from the swash plate to the resultant traction HB;

Vy - the vertical speed of the helicopter, in m / s;

Vx is the horizontal speed of the air flow near the HB, in km / h;

determine the total tangential velocity in the plane of the ends of the blades:

$$Vt=Vx\cos \alpha +Vy\sin \alpha (2)$$

and total normal (axial) speed:

$$Voc=Vy\cos \alpha +Vx\sin \alpha (3)$$

At the second stage in real-time helicopter flight, see Fig. 3, the outputs of block (9) and block (10) are connected to the inputs of the comparison block (11), in which the tangential velocity of the incoming flow near the rotor when it decreases due to the action of oncoming inductive velocities created by the vortex wake, and the axial (normal) velocity are compared with the boundary parameters of the zone of the vortex ring mode. Based on the results of the comparison, in block (11) the predicted air speed is determined when a pair of tangential and axial velocities is detected within the zone of the “vortex ring” modes, and light signals are generated from the block (11) entering the inputs of the blocks (12 and 13) and warning speech signals.

In addition, according to the results of the experiments, a speed range with an unstable regime of flow around the screw was also determined: an unstable regime of flow around the screw was observed with a decrease in the air speed near the NW to Vx≤45-50 km / h and the speed of decrease and Vy≥3-2 m / s and mode at Vx≥45 km / h and Vy≤3-2 m / s when there is no instability. When the helicopter decreases with a speed of more than 3 m / s and an air speed near the propeller, measured by a helicopter speed meter (VIS), less than 45-50 km / h, the pilot begins to signal the approach of the “vortex ring” zone with light and speech signals, as well as the automatic control system sends a command to reduce the pitch angle to the landing value, which excludes touching the safety fifth of the underlying surface, and at the same time stabilize the helicopter's vertical speed of descent to a value of not more than 2.0 m / s.

When entering the "vortex ring" mode, the alarm signals are amplified, which requires the pilot to immediately increase the flight speed and, if there is an engine power reserve, try to reduce the vertical speed after acceleration to Vx≥40 km / h.

Example

At the stage of the experiment, the rotor (HB) is predicted to approach the “vortex ring” regime zone in the pre-landing maneuvers of the Mi-8 single-rotor helicopter by measuring in time the vertical velocity of the helicopter Vy and the airspeeds Vx near the blade using the LDPE installed in its tip connected with a low speed meter. In addition, the angle of attack α of the screw is calculated for the corresponding combinations of speeds Vx and Vy. Based on these data, the total tangential and normal components of the velocity values near the rotor are determined by the formulas (1), (2), (3) in block (9) in Fig. 3. In preliminary flight tests of a single-rotor helicopter according to well-known criteria: an increase in the helicopter's decrease in speed due to an increase in the required power, increase in the pulsation of the NV thrust, by visualizing a satellite vortex wake or by determining the decrease in the helicopter control efficiency with measuring the helicopter trajectory parameters in modes and fixing the wind speed modes of the "vortex ring", figure 4, which is used to identify the modes of HB when approaching the zone in the current time real pre-landing maneuvers.

For the estimated calculation of the position of the Mi-8 helicopter NV relative to the zone of “vortex ring” modes, a fixed approach time is taken corresponding to the helicopter flight speed of 60 km / h. According to the instructions, the vertical descent speed during approach should not exceed 2 m / s. In this helicopter flight mode, there is a joint effect on the decrease in local speed near the HB from the decline, Fig. 1, and braking, Fig. 2, which corresponds to a decrease speed of -4 m / s in Fig. 1. So, at a decrease speed of Vy = -4 m / s, the low-speed indicator near the HB showed a decrease in the horizontal component of the air flow velocity near the HB by 43 km / h, that is, from 60 km / h it decreased to 17 km / h = 4.7 m / s, which may correspond to the combined effect of lowering and braking in a real pre-landing maneuver.

The angle of attack is determined α = arctgVy / Vx = arctan (-2) / 4.7 = 23 ⁰ 30 ⁱ . Then determine the total tangential Vt and axial Voc speeds according to formulas (2) and (3):

Vt = 5.1 m / s = 18.36 km / h and Voc = -3.72 m / s.

Such a paired combination of tangential Vt and axial Voc velocities corresponds to falling into the zone of modes of the "vortex ring", see figure 4.

It is important what happens near the HB in the pre-landing maneuver at an air speed of 80 km / h. As at 60 km / h, figure 1, there was an underestimation of the speed of the air flow near the HB by an amount close to 43 km / h. Therefore, the horizontal speed in the plane of the ends of the blades will be equal to 37 km / h = 10.3 m / s. The angle of attack α = arctg (-2) / 10.3 = 11 ° is determined. Then, the total tangential Vt and axial Voc velocities are determined by formulas (2) and (3):

Vt = 10.49 m / s = 37.72 km / h and Voc = -3.93 m / s.

At a helicopter speed of 80 km / h, the HB is also located near the “vortex ring” mode zone, and a slight increase in the helicopter's reduction speed or increase in its pitch will lead to the “vortex ring” regime entering the zone.

Since the pilot does not even suspect the proximity of the zone of modes of the "vortex ring", he receives a voice and light warning.

According to the results of the experiments, a criterion was also determined by which an unstable regime of flow around a screw is estimated: an unstable regime of flow around a screw was observed with a significant decrease in air speed near the HB:

Vx≤45 km / h and Vy≥3-2 m / s and the mode when Vx≥45 km / h and Vy≤3-2 m / s, there is no instability.

At the stage of flight, a warning device is used to approach the zone of modes of the "vortex ring", issuing light and sound signals, a block diagram of which is shown in figure 3. In addition, the signal enters the self-propelled guns, with the help of which the helicopter pitch is reduced to the landing value and the speed of the helicopter is reduced to a value of no more than 2 m / s.

Thus, obtaining additional information in flight tests at positive angles of attack about a significant decrease in the air flow near the HB will significantly improve the known methods of warning the pilot about getting into the “vortex ring” zone as applied to pre-landing maneuvers of helicopter equipment.

Claims (2)

1. A method for determining and signaling the rotor (HB) approach to the zone of “vortex ring” modes on pre-landing maneuvers of a single-rotor helicopter, including measurement in preliminary flight tests using a system of horizontal and vertical airspeed meters of a helicopter, determining from these paired values on the axes abscissa and ordinates of the diagram of the boundaries of the appearance of the “vortex ring” of a helicopter, comparison during the pre-landing maneuver of the tangential and normal air flow velocities with the parameters of the zone of the "vortex ring", the definition and signaling of approaching the "vortex ring" mode and the formation of a warning signal, characterized in that the air speed of the incoming flow near the rotor is measured using an air pressure receiver (LDPE) installed in the tip of the blade , on the pre-landing maneuvers of the helicopter, the vertical speed of the helicopter, the pitch angle of the helicopter, the angle of deviation of the swashplate in the longitudinal direction are measured, and the angle of attack of the HB, tangential y and the normal components of the air flow speed in the current time according to the following formulas:
$$\alpha =\vartheta +\phi sa\mathrm{to}l.+D\mathrm{one}\delta \mathrm{at}+arctg3.6\cdot Vy/Vx,(\mathrm{one})$$

where α is the angle of attack of the HB, in degrees;
ϑ is the pitch angle of the helicopter, in degrees;
ph. - angle of spell (tilt forward) of the axis of rotation of the HB, in degrees;
δв - angle of deviation of the swashplate in the longitudinal direction, in degrees;
D1 - gear ratio from the swash plate to the resultant traction HB;
Vy - the vertical speed of the helicopter, m / s;
Vx is the horizontal speed of the air flow near the HB, km / h;
determine the total tangential velocity in the plane of the ends of the blades:
$$Vt=Vx\cos \alpha +Vy\sin \alpha (2)$$

and total normal (axial) speed:
$$Voc=Vy\cos \alpha +Vx\sin \alpha ,(3)$$

the tangential velocity of the incoming flow near the rotor when it decreases due to the inverse oncoming speeds created by the HB vortex wake, and the axial (normal) speed is compared with the boundary parameters of the vortex ring zone, and when the helicopter decreases with a speed of more than 3 m / s and at an air speed near the propeller of less than 45-50 km / h, the pilot begins to signal about approaching the “vortex ring” zone by light and speech signals, as well as an automatic control command is transmitted to the automatic control system (ACS) enii pitch angle value before planting precluding safety fifth touch the underlying surface and simultaneously stabilize the vertical descent rate of the helicopter to a value not exceeding 2.0 m / s. 2. The method of detecting and signaling the rotor (HB) approaching the zone of “vortex ring” modes on pre-landing maneuvers of a single-rotor helicopter according to claim 1, characterized in that when it enters the “vortex ring” mode, alarm signals are amplified, which requires the pilot an immediate increase in flight speed and in the presence of a reserve of engine power, after acceleration to Vx = 40 km / h, try to reduce the vertical speed.

Images