1. 1 Overview
As a modern weapon, with the development of science and technology, the composition and functions of its various systems are becoming more and more perfect and advanced. As a result, the development cost and single machine price of aircraft have increased correspondingly, and the development cycle has also increased. When making investment decisions, such as the development of new machines and the major improvement of old machines, it is necessary to analyze the cost-benefit ratio. The basis and difficulty of fighter cost-effectiveness analysis lies in how to evaluate its operational effectiveness. When the air force and navy departments make the procurement plan of a certain type of aircraft or put forward new requirements to the research department, they also urgently require the operational effectiveness analysis for the operational objectives: the research department pays attention to a new technology in the development work.
When making technical decisions, the main consideration is to meet the needs of the troops as much as possible, and the important aspects of judging whether to meet the needs need to be analyzed. Therefore, the analysis and research of fighter air combat effectiveness is the demand promoted by the development of science and technology; It is the objective need of personnel at all levels engaged in the development of weapons and equipment. Fighter combat effectiveness evaluation is a comprehensive technology and a means to measure the quality of fighter. The evaluation of fighter as a weapon system fully reflects the influence of the main technologies adopted by the aircraft on its combat capability. According to the development of previous air combat experience and tactical theory research, the composition, maneuvering flight trajectory, fire control system and weapons used by fighter groups in different air combat stages are different.
Therefore, the air combat of fighters is mainly divided into two stages: over-the-horizon air combat and close air combat. The effectiveness of over-the-horizon air combat mainly depends on airborne equipment and weapons; The effectiveness of close air combat mainly depends on the maneuverability of the aircraft and the off-axis ability of the missile (including the use of photoelectric radar or helmet). As a first-generation and second-generation aircraft, it basically has no over-the-horizon air combat capability (only a few second-generation aircraft have improved over-the-horizon attacks), and the effectiveness of close air combat is relatively poor. Early models of the third generation aircraft, such as the F-A aircraft, mainly improved maneuverability and close combat effectiveness. The mobility of the third-generation aircraft is about 70% higher than that of the second-generation aircraft, which leads to a difference of 2-3 times between the close combat effectiveness of the two generations of fighters. With the development of technology, the improved third-generation fighter, such as F- 16C, is equipped with AIM-7F medium-range missile, which greatly enhances the over-the-horizon combat effectiveness. In order to further improve the operational efficiency of the aircraft, the fourth generation fighter adopts stealth technology and long-range supersonic cruise mode, installs long-range detection radar and hangs active radar air-to-air missiles; Advanced aerodynamic layout is adopted at close range, which has good aerodynamic characteristics and thrust vector at high angle of attack. On the basis of the maneuverability of the third generation aircraft, it is emphasized to improve the agility and post-stall maneuverability of the aircraft. The work of air combat effectiveness analysis has long been valued by the world. Fighter combat effectiveness evaluation mainly adopts weighted parameter method, which belongs to static evaluation method and depends on user's experience to a great extent. In the 1980s, the way to study air combat simulation in China mainly used differential game, which had a large amount of calculation and could not directly reflect the parameter influence of aircraft and its weapon system. It is inconvenient to use in aircraft design, and the reliability of its calculation results is often doubtful. At the end of 1980s, China developed an air combat effectiveness analysis software which can simulate the action of aircraft. The software is simple in simulating fire control systems and missiles, but there is still a certain gap in evaluating the operational effectiveness of modern fighters.
1.2 development trend of foreign combat effectiveness technology
The United States, Russia and other aviation developed countries attach great importance to the research on the operational effectiveness of military aircraft, and have set up special institutions to do these research work, such as Gosnias in Russia, where special departments conduct the research on the operational effectiveness of aviation weapon systems.
As early as 1970s, a kind of air combat simulation device combining computer simulation with hardware-in-the-loop simulation and human in the loop was put forward abroad. The cost of building such facilities is very high, and the calculation period is very long. The United States, the former Soviet Union, France, Britain, Germany and other countries have built such facilities for air combat simulation.
In 1980s, with the rapid development of computer workstations and microcomputers and the wide application of simulation technology, the United States, Europe and Russia all adopted digital simulation as the main means of combat effectiveness analysis. In the design process of American F-22 aircraft, in order to determine the matching of aircraft, fire control system, weapons and other parameters, 1 million air combat simulations including various situations were carried out on the microcomputer, and 10 thousand air combat simulations were completed every day. From the situation of various foreign combat effectiveness research, according to its complexity, aircraft combat effectiveness research can be preliminarily divided into four levels [8:: comparison method (performance parameter analysis), calculation and evaluation method (effectiveness index analysis), computer simulation method (hardware-in-the-loop simulation of air combat simulator and computer air combat full digital simulation) and flight test (real flight test and full-physical simulation of air combat exercise). Each method has its own advantages and disadvantages and is suitable for a certain range of applications. Many times, different methods need to complement each other to better explain the problem. Simulator air combat simulation and computer air combat simulation are widely used in the top-level analysis and demonstration stage.
1) comparison method
This method is often used in engineering applications, and its main manifestation is to list the main index parameters in the table according to the combat objects to be compared, and then make a comparative analysis. The parameters listed in the table generally mainly include performance parameters, radar parameters, missile parameters and RCS, including flight envelope (aircraft altitude and speed range), steady hovering overload, instantaneous hovering angular velocity, climb rate, range and operational radius, takeoff and takeoff. Radar parameters include radar detection distance, tracking distance, search and tracking airspace, etc. Missile parameters include attack distance, overload, off-axis angle and terminal guidance distance.
2) Calculation and evaluation methods
Calculation and evaluation method is a method to select the parameters closely related to the effectiveness of combat aircraft and calculate them according to certain laws to get the index or representative value of effectiveness. Examples of this method are close attack coefficient method and operational effectiveness index method. The specific formula of the near attack coefficient method is expressed as an equation of n (stable hovering overload) and Nyinax (maximum use overload) SEP (unit residual power). By selecting the above parameter values, the near attack coefficient values can be calculated, and the operational effectiveness of each aircraft can be obtained through the above calculation for different aircraft.
The operational efficiency index method can be divided into air-to-air efficiency index and air-to-ground efficiency index, and the key problem in using the calculation and evaluation method is to choose evaluation parameters. Parameters closely related to different combat aircraft should be selected according to their main tasks. For example, parameters related to the attack power and target detection ability of mobile weapons can be selected to evaluate air-to-air effectiveness; Parameters related to bomb load, number of pylons of external weapons, survivability and penetration ability can be selected to evaluate air-to-ground effectiveness. For some parameters that are difficult to obtain by technical calculation, they can be selected by expert decision.
3) Computer simulation method
Computer simulation methods are divided into digital simulation method and air combat simulation (air combat simulator) method. Among them, the simulation calculation is to calculate the flight trajectory of the aircraft step by step according to the accurate data and motion equation of the aircraft. The calculation result is given in the form of loss rate, and it takes many air combat simulation calculations to finally get the statistical average. Air combat simulation is developed on the basis of digital simulation. The six-degree-of-freedom motion equation is adopted, and the cockpit vision system, flight control system and instructor monitoring system are added. Operation requires throttle lever, pedal, steering lever, radar interception and weapon launch button.
4) Flight test method
The flight test method is relatively complex, which can truly evaluate the combat effectiveness of both sides in air combat, but it takes a lot of time, money and manpower, and it is very difficult to realize. Because the digital simulation method integrates aircraft aerodynamic performance, radar fire control, missile, stealth and other professional technologies, and is closely combined with dragonfly air combat tactics, the theory and simulation in China still need to be improved. From the development trend, operational effectiveness evaluation technology will become an essential technology for future aircraft design. Therefore, from the perspective of engineering application, it is very important to carry out this research, track the world's advanced technology and better apply it to the model.
1.3 the basic characteristics of air combat and the significance of effectiveness evaluation research.
The third generation fighter is a fighter with missiles as its main weapon for air combat. It is generally believed that modern air combat includes two stages: over-the-horizon and close range, but the characteristics of air combat in each stage are different. In the stage of over-the-horizon air combat, the activities of fighters have the characteristics of fleet combat. General fighters are divided into different tactical task groups, and each task group should complete the tasks specified in the overall operational intention, such as intercepting enemy bombers and preparing to encounter enemy escort fighters. However, in any case, the maneuvering flight carried out by each crew to complete the scheduled task must ensure that the fighters enter a favorable weapon launching state. To this end, it can be considered that the air combat mode of fighters consists of the following stages:
The stage of approaching and searching. At this time, according to the command of the ground (or air) commander, the fighter plane climbed to the predetermined flight altitude and approached the target. When the target enters the detection range of the fighter's airborne radar, the fighter's flight tries to make the radar intercept the target. Subsequently, the fighter plane entered the stage of preparing for maneuver to ensure the missile launch conditions;
-Prepare for the maneuver phase. At this stage, in order to ensure that the airborne radar always intercepts the target and reach the missile launch conditions as soon as possible, the fighter must carry out corresponding curve tracking flight.
-Missile launch and guidance phase after launch. When the target enters the missile attack zone, the missile can be launched. However, after the missile is launched, for medium and long-range missiles with semi-active radar terminal guidance, fighter radar is required to continuously illuminate the target (providing the necessary information for the missile to correct the target position error) until the missile enters the active guidance section.
-Avoid the attack stage of enemy missiles. At this stage, the fighter completes a sharp maneuver flight (such as afterburner turn and dive). ) to avoid the attack of enemy missiles, and finally the fighter quits the over-the-horizon air combat or enters the close air combat.
Close air combat is carried out when the pilot can see the target visually and there is no information support from the ground (or air) commander. At this time, the distance between the enemy and ourselves is close, which determines the brevity of the battle, and the fighters have to complete various tricky maneuvers. In this case, sharp maneuvering flight can be divided into:
-Maneuvering of the search target. For example, when the target is above the fighter, it uses combat turning maneuver flight; On the contrary, use half-rolling and flying backwards. ;
-Preparatory exercises to ensure that missile launch conditions are met. When using an all-round attack missile that can be launched off-axis, the principle of fighter maneuvering is to make the longitudinal axis of the aircraft point to the target quickly. Because, in close air combat, the effectiveness of the first missile launch plays a decisive role in the air combat. At the same time, under the condition that the missile performance of both sides is equivalent, the time for the fighter to aim at the target in advance should not be less than the time for the missile to fly to the target.