CN110930639B - Airborne wind shear alarm system and method for helicopter - Google Patents
Airborne wind shear alarm system and method for helicopter Download PDFInfo
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Abstract
The invention discloses a helicopter airborne wind shear alarm system and a method, wherein the system comprises an early warning type wind shear module and a reactive wind shear alarm module, the early warning type wind shear module obtains an early warning type threat factor value according to total available power, required power of the current flight state, the current vertical flight speed of a helicopter and the maximum wind speed of downdraft of a wind field, judges whether an alarm critical value is reached, and provides an alarm if the alarm critical value is reached; the reactive wind shear alarm module obtains a reactive threat factor value according to the total available power, the required power of the current flight state and the current vertical flight speed of the helicopter, judges whether the reactive threat factor value reaches an alarm critical value, and provides an alarm if the reactive threat factor value reaches the alarm critical value. The invention designs an airborne wind shear alarm system and method special for helicopters and aircrafts with similar flight characteristics by combining the characteristics of the helicopters, and can provide an alarm for the aircrafts encountering wind shear and enhance the flight safety.
Description
Technical Field
The invention relates to wind field airborne alarming of a helicopter, in particular to a wind shear airborne alarming method under two conditions of an early warning type and a reaction type.
Background
Wind shear generally refers to air flow with sharp changes in time or space, and in the many wind shear variant, the most dangerous is the slight downburst of horizontal vortex generally under 600m high altitude, wherein the downburst of central air is converted into outward radiating horizontal wind, so that the wind shear has the characteristics of wind speed variation diversity and wind shear strength variation severity.
The helicopter has the characteristics of low-altitude low-speed low-energy flight, is widely applied to low-altitude tasks such as marine rescue, forest fire fighting and the like, has increased probability of encountering wind shear, and has the characteristics of high wind shear strength, strong burstiness and the like, so that the threat of the wind shear to the helicopter cannot be ignored. At present, the existing wind shear alarm method applied to the airplane is more authoritative, but the flight condition and the flight mechanism of the helicopter are not completely the same as those of the airplane, and a corresponding alarm method is lacked.
Therefore, it is necessary to analyze the threat that the helicopter may encounter in wind shear and establish a corresponding warning method.
The wind shear alarm method of the airplane comprises the following steps: generally speaking, an early warning type Windshear (Predictive Windshear) alarm system measures airflow in front of a machine body based on an airborne radar, obtains a threat value through calculation, and gives an alarm if an alarm threshold is reached so as to guide a driver to avoid a wind field, and belongs to active monitoring.
The Reactive Windshear (Reactive Windshear) detects the energy level of the airplane through the sources of other system signals of the airplane, judges the existence of the Windshear and belongs to passive detection. In the wind shear environment, parameters such as the attitude, the calculated airspeed, the ground speed, the altitude, the track angle and the like of the airplane are obviously changed, the changes are provided to a Flight stability Augmentation Computer (Flight acceleration Computer) by an Atmospheric Data and Inertial Reference Unit (ADIRU), in addition, signals such as wind speed gradient, vertical wind speed and the like measured by other sensors can be calculated, then the FAC judges the existence of wind shear through calculation, and when the airplane energy is lower than a minimum safe energy threshold value, a warning is triggered to guide the airplane to escape. The system provides accurate F-factor readings, but requires that the warning be provided after the aircraft has flown in the wind field for 1km, i.e. after the aircraft has been fully immersed in the wind field, and a typical landing flight speed of the aircraft is about 75m/s, which requires a time delay of about 15 s.
The aircraft has high flying speed, lift force is generated mainly through wings, the relative incoming flow speed of an engine body is of great importance to the magnitude of the lift force of the aircraft, if the lift force is too small, the height is reduced, the thrust of the engine needs to be increased by the engine, and the flying speed is improved.
On the contrary, the helicopter has the advantages of low flying speed, generally 0-250km/h, approximate wind field horizontal wind speed range, strong maneuverability and short engine response delay; in addition, the horizontal direction and the vertical manipulation of the helicopter are mutually independent, and the vertical channel is less coupled with other manipulation channels, which is one of the main characteristics of the helicopter different from the airplane.
Disclosure of Invention
In order to fill the blank of the existing helicopter wind shear alarm method, the invention aims to provide a helicopter airborne wind shear alarm method.
In order to achieve the purpose, the invention adopts the technical scheme that:
a helicopter airborne wind shear warning system comprising an early warning wind shear module and a reactive wind shear warning module, wherein:
the early warning type wind shear module predicts and actively informs the wind shear in front of the helicopter through a meteorological radar system, and guides the helicopter to avoid; the early warning type wind shear module obtains an early warning type threat factor value according to the total available power, the required power of the current flight state, the current vertical flight speed of the helicopter and the maximum value of the wind speed of the downdraft of the wind field, judges whether the value reaches an alarm critical value or not, and provides an alarm if the value reaches the alarm critical value;
the reactive wind shear alarm module triggers an alarm when vertical downdraft exists and threatens the safety of the helicopter and the helicopter cannot overcome the vertical wind through normal operation in advance; and the reactive wind shear alarm module obtains a reactive threat factor value according to the total available power, the required power of the current flight state and the current vertical flight speed of the helicopter, judges whether the reactive threat factor value reaches an alarm critical value, and provides an alarm if the reactive threat factor value reaches the alarm critical value.
The early warning type wind shear module comprises a forward-looking wind shear radar, a torque meter or a power meter, an engine body motion sensor and a height sensor, wherein:
the forward-looking wind shear radar is used for obtaining the maximum value of the wind speed of the downdraft of the wind field in the front wind field through observation and calculation;
the torque meter or the power meter is used for measuring the required power of the current flight state of the helicopter;
the body motion sensor is used for measuring the current vertical flying speed of the helicopter;
the height sensor is used for measuring the current altitude to obtain the maximum continuous total available power of the engine.
The reactive wind shear alarm module comprises a torque meter or a power meter, a height sensor and a body motion sensor, wherein:
the torque meter or the power meter is used for measuring the required power of the current flight state of the helicopter;
the height sensor is used for measuring the current altitude to obtain the maximum continuous total available power of the engine;
the body motion sensor is used for measuring the current vertical flying speed of the helicopter.
A helicopter airborne wind shear warning method comprises an early warning type wind shear warning method and a reactive type wind shear warning method, wherein:
the early warning type wind shear method includes the steps that according to total available power, required power of a current flight state, current vertical flight speed of a helicopter and the maximum value of wind speed of downdraft of a wind field, an early warning type threat factor F calculation expression is brought into the early warning type threat factor F to obtain an early warning type threat factor value, whether the early warning type threat factor F reaches an alarm critical value or not is judged, and if the early warning type threat factor F reaches the alarm critical value, an alarm is provided;
the early warning type threat factor F is calculated and expressed as follows:
wherein, when F<1 indicates safety, when F>1 represents a threat, G being the total weight of the helicopter, VzIs the current vertical flying speed of the helicopter, WzFor the maximum value of the measured downdraft wind speed of the wind field, PcurPower demand, P, for the current flight situationTOTIs the total available power;
the reactive wind shear alarm method includes the steps of substituting a reactive threat factor F' calculation expression to obtain a reactive threat factor value according to total available power, required power of a current flight state and current vertical flight speed of a helicopter, judging whether the reactive threat factor value reaches an alarm critical value, and providing an alarm if the reactive threat factor value reaches the alarm critical value;
the formula of the formula threat factor F' is calculated as:
wherein, F '< 1 indicates safety, F' <1 indicates threat, G is total weight of helicopter, VzIs the current vertical flying speed, P, of the helicoptercurPower demand, P, for the current flight situationTOTIs the total available power.
And when any one of the early warning type threat factor and the reactive type threat factor reaches an alarm critical value, an alarm is triggered.
Has the advantages that: the invention designs an airborne wind shear alarm system and method special for helicopters and aircrafts with similar flight characteristics by combining the characteristics of the helicopters, and can provide an alarm for the aircrafts encountering wind shear and enhance the flight safety.
Drawings
FIG. 1 is a schematic illustration of a helicopter encountering wind shear;
FIG. 2 is a graph of vertically descending airflow boundaries and their corresponding collective pitch stems for different combinations, where (a) is the vertically descending airflow boundary constrained by power conditions; (b) the total distance control lever amount corresponding to the boundary value in (a);
FIG. 3 is a diagram illustrating a comparison of threat factor expressions;
FIG. 4 is a schematic view of a reactive wind shear warning system;
FIG. 5 is a schematic view of a pre-warning wind shear warning system;
FIG. 6 is a combined early warning and reactive helicopter wind shear warning system.
Detailed Description
The invention is further explained below with reference to the drawings.
Fig. 1 shows a schematic view of a scenario in which a helicopter flies over a wind farm. As shown in fig. 1, a helicopter 1 enters a wind field 2, and sequentially passes through an upwind 3, a downwind 4 and a downwind 5, horizontal wind gradually weakens from high-speed upwind, then increases and turns to a high-speed downwind environment, and the horizontal wind speed changes obviously. In addition, vertical downdraft exists in the center of the wind field, the vertical wind speed is high when the wind field is away from the ground, and the vertical wind speed is weakened when the wind field is close to the ground. Under the above-mentioned scene, when the helicopter flies along the horizontal direction and encounters the wind direction change from the upwind to the downwind, the helicopter can better adapt to the change of the horizontal wind speed and keep the body stable through the assistance of proper operation and the stability augmentation system and through the excellent acceleration and deceleration maneuvering performance of the helicopter. Therefore, horizontal wind shear is less threatening to the helicopter. And the vertical downwind can cause the lift force of the rotor wing to be reduced, so that the body descends. In order to overcome the descending speed of the body, the lift force of the rotor wing can be improved by operating the total distance, but the required power is increased. If the vertical wind speed is too high, the control limit or the power limit of the helicopter can be reached, so that the risk of falling exists. Vertical winds dominate the helicopter threat.
Therefore, it is necessary to analyze the variation trend and the range of the boundary of the downwind threat, namely the variation trend and the range of the extreme value of the downwind speed acceptable by the helicopter. From the flight condition of the helicopter, the factors influencing the boundary threatened by downwind mainly include load and altitude, and the constraint condition is the operation of available power and total distance. For comprehensively considering the influence of power and starting from larger safety margin, the maximum continuous available power output P of the helicopter caused by the change of the flight altitude h is consideredTOT(h) Which may be expressed as a function of altitude, generally, the available power decreases as altitude increases.
Typical flight conditions can be selected to calculate the coverage of threat boundaries and their trend of change. In the embodiment, three combinations of loads and altitudes are selected, the minimum design load flight altitude is 300m, the maximum design load flight altitude is 300m, and the maximum design load flight altitude is 2000 m. The altitude of 300m represents the state when the available power output of the body is maximum, and the altitude of 2000m is about the hovering rising limit of the sample helicopter, and the altitude can take the characteristics of wide flight speed envelope range and high altitude into consideration.
As fig. 2 shows the calculation results in the above embodiment, it can be seen that the vertical gas flow boundary changes significantly. Fig. 2 (a) shows the vertical downwind variation corresponding to the above 3 different combinations with the change in the forward flight speed. The baseline configuration at 300m altitude analyzes the threat boundary when the helicopter is at maximum load. The vertical wind boundary is primarily limited by the available power of the helicopter, which is not greatly affected by collective pitch, yet leaves sufficient maneuvering margin. In addition, the curve shows a tendency to be high in the middle and low on both sides. Because the trend of the required power of the saddle curve shape of the helicopter is generally simply estimated, the residual available power in horizontal flight can be approximately converted into the climbing required power, and therefore, the bearing capacity of the helicopter body to vertical airflow is strongest when the helicopter flies at cruising speed.
In addition, the vertical air flow envelope varies significantly with the total load of the body. The configuration with the same altitude and the lightest load has the strongest resistance to vertical wind and the highest vertical downdraft envelope line due to larger available residual power. In addition, (a) in fig. 2 shows that the envelope boundary speed difference is continuously reduced as the forward flight speed is increased under different load conditions of the helicopter. This is mainly because, as the forward flight speed increases, the proportion of the type drag power to the total required power increases, which is only related to the flight speed of the helicopter, but not to the load, and the remaining available power tends to be similar.
Further, the vertical airflow envelope varies significantly with altitude. The change trend is more uniform for the same helicopter configuration. With the increase of the forward flight speed, the difference of envelope curve difference values of different altitudes is smaller and is consistent with the linear change of available power along with the altitude, the required power change of the helicopter is not obvious, and therefore the change of the residual power along with the flight speed is basically a constant value.
Fig. 2 (b) shows a total distance rod amount change curve required at each corresponding vertical speed in the above figure. Generally speaking, the factors affecting the vertical downdraft boundary are the total weight of the airframe, the altitude, and the forward flight speed. However, the more influencing factors do not fit the engineering practice. And therefore are considered from other perspectives. When the wind field threat boundary shown in fig. 2 (a) is calculated, the boundary constraint condition mainly applied is power limitation, the residual power can represent the residual energy of the helicopter, can cover the full-flight envelope of the helicopter along with the change of the altitude, the flight state of the helicopter and the like, can also represent the capability of the helicopter in resisting the wind field, and is suitable for being used as the judgment condition of the threat alarm method.
From the helicopter performance calculations, when estimating helicopter power, there are:
Pcur＝Plevel+G(Wz-Vz)
wherein, PcurPower demand, P, for the current flight situationlevelThe required power of the helicopter in flat flight without wind field, Wz，VzThe wind field downdraft wind speed and the helicopter vertical flying speed (positive downwards) are respectively, and G is the total weight of the helicopter. The above formula can show that when the vertical motion speed exists, the total power required by the machine body is divided into two parts, namely the power required by the plane flight PcurPower G (W) required for vertical movementz-Vz). Wherein the power required for vertical movement can be converted into the gravitational potential energy of the helicopter.
Helicopters have unique vertical flight capabilities and, therefore, their flight status has a variety of conditions. Such as level flight, climb, descent, etc. Among them, horizontal flight is the primary state of helicopter flight. The power required by each state is different, and under the same forward flight speed, the power required by climbing is the largest, the power required by flat flight is the next highest, and the power required by descending is the smallest. When the available power of the engine is determined to be a fixed value, the available residual power in the climbing state is minimum, and the available residual power in the descending state is maximum. Under the condition of being threatened by a wind field, if the helicopter reserves power in a mode of descending along with the wind field, the height of the helicopter body is reduced, and the safety margin cannot be ensured. If the climbing flight state is adopted, the wind speed is increased from bottom to top in the vertical direction in the range of a wind field, and the increase of the wind speed also causes the flight safety margin of the aircraft to be lower in the state of lower climbing residual power.
Combining the above analysis, define: if the helicopter can fly over the wind field in a horizontal flight state at the height of entering the wind field, the wind field has no threat to the aircraft.
In fact, the early warning type wind shear is predicted by a meteorological radar system and actively informed of the wind shear ahead, so that the airplane is guided to avoid. And the early warning time is long in advance, and enough time can be provided for the pilot to avoid.
The pre-warning wind shear radar generally comprises an infrared radar, a microwave doppler radar, a laser doppler radar and the like. The infrared wind shear radar detects wind shear by detecting a temperature field according to the linear relation between the speed and the temperature of downwash, so that the wind speed of vertical wind can be directly measured. The microwave Doppler radar and the laser Doppler radar are based on Doppler effect and can detect radial wind speed.
The threat of the helicopter mainly comes from the influence of vertical wind, the horizontal wind shear has little threat to the helicopter, if a Doppler radar is utilized, only the radial speed can be measured, and the vertical wind speed can be obtained through horizontal wind shear fitting.
The early warning type wind shear is predicted by a meteorological radar system and actively informed of the wind shear in front, so that the airplane is guided to avoid. During the forward flight, the radar monitors or applies a scaling factor to calculate the vertical airflow. And then calculating the power value of the helicopter flying over the wind field at the current flying speed and encountering the vertical wind, and if the power value is lower than the total required power, ensuring that the safety is not threatened, namely
Plevel+GWz＝Pcur-GVz+GWz<PTOT
Wherein, PcurPower demand, V, for the current flight situationzIs the current vertical flying speed of the helicopter, WzAnd G is the maximum value of the measured downdraft wind speed of the wind field, and is the total weight of the helicopter.
The above formula is converted to be applicable to various helicopters, and can be represented by a uniform quantization standard F. F, in fact, as a threat factor, may be represented by F1 and F2, respectively, specifically,
both of the above equations indicate safety when F <1, and indicate a threat if F > 1.
In combination with the actual needs of engineering, and considering the factors of the above formula, such as rough estimation of the available power of the rotor, early warning time and the like, the critical value of F can be set to be less than 1 on the premise of not increasing the false alarm rate.
Both F1 and F2 can be used for calculating the early warning threat factor of wind shear, and the difference of the two is further analyzed in order to reduce the false alarm rate and the false alarm rate of the warning method.
FIG. 3 shows the velocity V of the vertical motionzDetermining the current power PcurUnder known conditions, the threat factor F follows the vertical wind speed WzA change in (c). The intersection point of the two straight lines is the critical point for judging the threat, and both the intersection points are in the states of F1 and F2 at the alarm critical value 1. The dashed line in fig. 3 shows the critical edge line of the threat factor F between alarm and security, above the dashed line, i.e. F>1, representing a threat area; below the dotted line, i.e. F<When 1, a safety region is indicated. The slopes of the two expressions are different under the same calculation state quantity, F1Is smaller in slope, F2The slope of the threat factor is larger, the larger slope indicates that the threat factor is more sensitive to vertical wind speed change, and the threat factor caused by the same vertical wind speed change is larger in change, so that the calculation result is more differentiated. In practical engineering practice, more sensitive threat factors are needed to accommodate various types of emergencies. It can be understood that when the helicopter encounters wind shear, the earlier the early warning time is, the longer the operation time is left for the operator, so that the operator can more effectively avoid the risk of partial shear. Therefore, the expression of the pre-alarm threat factor F may be expressed as:
FIG. 4 is a pre-warning wind shear module and method flow thereof, the pre-warning wind shear module 10 predicts and actively informs the wind shear ahead of the helicopter through a weather radar system, and directs the helicopter to avoid; the early warning type wind shear module 10 obtains an early warning type threat factor value according to the total available power, the required power of the current flight state, the current vertical flight speed of the helicopter and the maximum value of the wind speed of the downdraft of the wind field, judges whether the value reaches an alarm critical value or not, and provides an alarm if the value reaches the alarm critical value. The pre-warning type wind shear module 10 comprises a forward-looking wind shear radar 11, a torque meter or power meter 12, a body motion sensor 13 and a height sensor 14, wherein: observing and calculating by the forward-looking wind shear radar 11 to obtain the maximum value of the wind speed of the downdraft of the wind field in the front wind field; meanwhile, a torque meter or a power meter 12 measures the required work of the current flight state of the helicopter; meanwhile, the body motion sensor 13 measures the current vertical flying speed of the helicopter; meanwhile, the current altitude is measured by the altitude sensor 14, and the maximum continuous total available power of the engine is obtained; and finally, according to the total available power, the required power of the current flight state, the current vertical flight speed of the helicopter and the maximum value of the wind speed of the downdraft of the wind field, bringing the values into a calculation expression of an early warning threat factor F to obtain an early warning threat factor value, judging whether the value reaches an alarm critical value, and if the value reaches the alarm critical value, providing an alarm.
The early warning type wind shear module and the method thereof have the advantages that the calculation formula is simple, the required calculation parameters are few, and the means in the prior art can basically meet the calculation precision requirement so as to obtain the accurate threat factor value. In addition, the complexity is low, the power is taken as a key factor and is used as a judgment reference, the flying envelope of the machine body can be effectively and comprehensively covered, and the machine body state can be expressed in real time. On the other hand, the characteristics of basic flight control of the helicopter are effectively combined, and the helicopter is suitable for various helicopters.
The helicopter airborne wind shear alarm system and method further comprise a reactive wind shear alarm module and a method thereof, wherein reactive wind shear is input through other system signals and judged by a flight stability augmentation computer, namely the reactive wind shear alarm can be judged by combining with the body state.
When the helicopter is flying horizontally in the wind field, i.e. VzNo height loss, where the vertical wind speed is WzThe constraint condition of the required power of the helicopter at this time is lower than the total available power PTOTAnd then:
Plevel+WzG<PTOT
and Pcur＝Plevel+G(Wz-Vz) Simultaneous elimination of vertical wind speed Wz：
GVZ<PTOT-Pcur
The reactive threat factor F' may be expressed as:
and the alarm critical value is F' less than 1.
In the reactive wind shear, the helicopter is in the environment of a wind field, the vertical downdraft is coupled with the descending speed of the helicopter body, the wind speed sensor is arranged on the helicopter body, and the influence of the downwash action of the rotor wing needs to be considered, so that the wind speed value measured by the sensor on the helicopter body has certain limitation, the vertical movement speed of the helicopter can be accurately measured by the sensor on the helicopter body, and the confidence coefficient is high.
The calculation of the reactive threat factor takes the current flight state of the helicopter as a calculation quantity, and wind field information is not input. Therefore, there is a need to verify the possibility of the method providing an alarm in normal flight conditions. The above analysis is based on a flat flight state analysis, and the following demonstrates the practicality in climbing and descending states, respectively.
1) If the body is in climbing phase, i.e. Vz<0, although vertical airflow exists at the moment, the power is still abundant for climbing, the height of the machine body is increased, the energy is increased, obviously, no threat exists, and the corresponding F' is less than 0.
2) If the body is lowered by Vz in the non-vertical wind environment, the corresponding reactive threat factor F' is:
no alarm is triggered.
False alarm rate (e.g. reaching a dangerous wind shear condition without warning) probability analysis:
the method is established on the premise that: in the case of a descending speed of the body, the driver avoids the descending of the body by means of correct steering (total distance increase), if the danger caused by the driver not performing steering, such as the great descending of the height, even the falling of the ground, is out of the consideration of the method; or the helicopter height keeps the stability augmentation control system in an open state, so that the situation of body height reduction can be effectively responded.
In summary, when and only when there is vertical downdraft and threatens the safety of the machine body, and it is judged in advance that the machine body cannot overcome the vertical wind through normal operation, an alarm is triggered.
Fig. 5 shows a reactive wind shear warning system and a method thereof, wherein the reactive wind shear warning module 20 includes a torque meter or power meter 21, an altitude sensor 22, and a body motion sensor 23, wherein: a torque meter or a power meter 21 measures the required power of the current flight state of the helicopter; meanwhile, the current altitude is measured by the altitude sensor 22, and the maximum continuous available power of the engine is obtained; meanwhile, the body motion sensor 23 measures the current vertical flying speed of the helicopter; and finally, substituting the total available power, the required power of the current flight state and the current vertical flight speed of the helicopter into a reactive threat factor F' calculation expression to obtain a reactive threat factor value, judging whether the reactive threat factor value reaches an alarm critical value, and providing an alarm if the reactive threat factor value reaches the alarm critical value.
The reactive wind shear alarm system and the method thereof have simple calculation formula and less required calculation parameters, and the prior art means can basically meet the calculation precision requirement to obtain the precise threat factor value. The sources of all calculation parameters are helicopter existing equipment, other equipment does not need to be additionally arranged, and extra load of the helicopter body is reduced. The calculation parameters are real-time calculation parameters of the helicopter, the timeliness is good, and the alarm can be effectively provided for operators. In addition, the complexity is low, the power is taken as a key factor and is used as a judgment reference, the flying envelope of the machine body can be effectively and comprehensively covered, and the machine body state can be expressed in real time. On the other hand, the characteristics of basic flight control of the helicopter are effectively combined, and the helicopter is suitable for various helicopters.
Wind shear evasion: under the condition of the same descending speed and vertical wind, the required power P of the horizontal flight is smallerlevelCorresponding to smaller required power PcurThe corresponding F-factor is small, so that the cruising flight airspeed (in this state) is usedPower demand P for flat flightlevelMinimum), the bearing degree of the vertical downwind by the crossing wind field is highest, and is consistent with the change of the threat boundary. When the pilot receives the wind shear alarm, the pilot is instructed to control the front flight airspeed to approach the cruising speed, the power required by the front flight is reduced, and the total distance is increased; the radar can also indicate the direction with smaller vertical wind to guide the pilot to avoid; and under the condition of ensuring the safety distance from the ground, the height is properly reduced to enter a vertical wind speed weakening area.
According to the characteristics of similarity of basic principles and multiple common points of the two embodiments, the wind shear alarm system can be further combined into a comprehensive wind shear alarm system. Fig. 6 illustrates an on-board helicopter wind shear warning system 100 of the present invention, which includes an early warning wind shear module and a reactive wind shear warning module 20, which combines early warning and reactive helicopter wind shear warning. When any threat factor value reaches the alarm critical value, an alarm can be sent out. The comprehensive system inherits the advantages of two wind shear alarm methods, effectively enhances the redundancy of the alarm system and improves the safety.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (9)
1. A helicopter airborne wind shear warning system characterized by: including early warning formula wind shear module and reaction formula wind shear alarm module, wherein:
the early warning type wind shear module predicts and actively informs the wind shear in front of the helicopter through a meteorological radar system, and guides the helicopter to avoid; the early warning type wind shear module obtains an early warning type threat factor value according to the total available power, the required power of the current flight state, the current vertical flight speed of the helicopter and the maximum value of the wind speed of the downdraft of the wind field, judges whether the value reaches an alarm critical value or not, and provides an alarm if the value reaches the alarm critical value;
the early warning type threat factor F is calculated and expressed as follows:
wherein, F is less than 1 to represent safety, F is more than 1 to represent threat, G is the total weight of the helicopter, VzIs the current vertical flying speed of the helicopter, WzFor the maximum value of the measured downdraft wind speed of the wind field, PcurPower demand, P, for the current flight situationTOTIs the total available power;
the reactive wind shear alarm module triggers an alarm when vertical downdraft exists and threatens the safety of the helicopter and the helicopter cannot overcome the vertical wind through normal operation in advance; the reactive wind shear alarm module obtains a reactive threat factor value according to the total available power, the required power of the current flight state and the current vertical flight speed of the helicopter, judges whether an alarm critical value is reached, and provides an alarm if the alarm critical value is reached;
the calculation expression of the reactive threat factor F' is as follows:
wherein, F '< 1 indicates safety, F' <1 indicates threat, G is total weight of helicopter, VzIs the current vertical flying speed, P, of the helicoptercurPower demand, P, for the current flight situationTOTIs the total available power.
2. A helicopter airborne wind shear warning system according to claim 1, characterised in that: the early warning type wind shear module comprises a forward-looking wind shear radar, a torque meter or a power meter, an engine body motion sensor and a height sensor, wherein:
the forward-looking wind shear radar is used for obtaining the maximum value of the wind speed of the downdraft of the wind field in the front wind field through observation and calculation;
the torque meter or the power meter is used for measuring the required power of the current flight state of the helicopter;
the body motion sensor is used for measuring the current vertical flying speed of the helicopter;
the height sensor is used for measuring the current altitude to obtain the maximum continuous total available power of the engine.
3. A helicopter airborne wind shear warning system according to claim 1, characterised in that: the reactive wind shear alarm module comprises a torque meter or a power meter, a height sensor and a body motion sensor, wherein:
the torque meter or the power meter is used for measuring the required power of the current flight state of the helicopter;
the height sensor is used for measuring the current altitude to obtain the maximum continuous total available power of the engine;
the body motion sensor is used for measuring the current vertical flying speed of the helicopter.
4. A method for alarming wind shear onboard a helicopter based on the system of any of claims 1-3, characterized in that: the method comprises an early warning type wind shear method and a reactive type wind shear warning method, wherein:
the early warning type wind shear method obtains an early warning type threat factor value according to the total available power, the required power of the current flight state, the current vertical flight speed of the helicopter and the maximum value of the wind speed of downdraft of a wind field, judges whether an alarm critical value is reached, and provides an alarm if the alarm critical value is reached;
the reactive wind shear alarm method obtains a reactive threat factor value according to the total available power, the required power of the current flight state and the current vertical flight speed of the helicopter, judges whether the reactive threat factor value reaches an alarm critical value, and provides an alarm if the reactive threat factor value reaches the alarm critical value.
5. The helicopter airborne wind shear warning method of claim 4, characterized in that: in the early warning type wind shear method, bringing the early warning type threat factor into an early warning type threat factor F calculation expression to obtain an early warning type threat factor value;
the early warning type threat factor F is calculated and expressed as follows:
wherein, F is less than 1 to represent safety, F is more than 1 to represent threat, G is the total weight of the helicopter, VzIs the current vertical flying speed of the helicopter, WzFor the maximum value of the measured downdraft wind speed of the wind field, PcurPower demand, P, for the current flight situationTOTIs the total available power.
6. A helicopter airborne wind shear warning method according to claim 5, characterized in that: the early warning type threat factor F calculation expression is obtained by the following method:
in the forward flight process, radar monitors or applies a scale factor to calculate vertical airflow, then the power value of the helicopter flying over a wind field at the current forward flight speed and encountering the vertical wind is calculated, and if the power value is lower than the total required power, the safety is not threatened, namely
Plevel+GWz＝Pcur-GVz+GWz＜PTOT
Wherein, PlevelThe required power of the helicopter in the flat flight without wind field;
the above formula is converted to be applicable to various helicopters, and threat factors F are introduced, wherein F is represented by F1 and F2, specifically:
the two formulas represent safety when F is less than 1, and represent threat if F is more than 1;
at the current vertical flying speed V of the helicopterzDetermining the current power PcurUnder known conditions, the threat factor F follows the vertical wind speedWzThe intersection point of the two straight lines is the critical point for judging the threat, and both the states are F1 and F2 in the state of the alarm critical value 1, and under the same calculation state quantity, F is2The threat factor is more sensitive to vertical wind speed change, the threat factor caused by the same vertical wind speed change is more variable, and the threat factor with higher sensitivity is needed to adapt to various emergency situations, so the expression of the early warning type threat factor F is as follows:
7. the helicopter airborne wind shear warning method of claim 4, characterized in that: in the reactive wind shear alarm method, a reactive threat factor F' calculation expression is substituted to obtain a reactive threat factor value;
the formula of the formula threat factor F' is calculated as:
wherein, F '< 1 indicates safety, F' <1 indicates threat, G is total weight of helicopter, VzIs the current vertical flying speed, P, of the helicoptercurPower demand, P, for the current flight situationTOTIs the total available power.
8. A helicopter airborne wind shear warning method according to claim 7, characterized by: the formula of the formula threat factor F' calculation expression is obtained by the following method:
when the helicopter is flying horizontally in the wind field, i.e. VzNo height loss, where the vertical wind speed is WzThe constraint condition of the required power of the helicopter at this time is lower than the total available power PTOTAnd then:
Plevel+WzG＜PTOT
and Pcur＝Plevel+G(Wz-Vz) Simultaneous elimination of vertical wind speed Wz：
GVZ＜PTOT-Pcur
The reactive threat factor F' is expressed as:
9. the helicopter airborne wind shear warning method of claim 4, characterized in that: and when any one of the early warning type threat factor and the reactive type threat factor reaches an alarm critical value, an alarm is triggered.
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