According to the engineering practice of new aircraft flight test in recent years, combined with the experience of foreign flight test,

This paper describes the characteristics of modern fighter flight test, including the number and period of flight test, air test and ground test.

Time monitoring, ground support facilities, flight tests of other aircraft and organization and management; Flight tests highlighted by fly-by-wire control

Test technology, including flight control system stability margin, flutter and aero-servo elasticity (ASE), man-machine closed-loop flying quality and

The high angle of attack flight test technology puts forward some problems existing in domestic flight test work.

Keywords: flight test; Flight control; Flight mechanics; Remote control; Modern fighter

Modern fighters are the so-called third generation fighters, such as F 16.

F 18, CY-27, gust, EF2000, etc. , with the following characteristics: advanced.

Aerodynamic layout, fly-by-wire flight control system, highly integrated aviation

Electronic systems, high-performance power devices, including composite materials.

Structure. Because of these new technologies, the plane is wide.

Performance envelope, excellent flying quality, excellent maneuverability and so on.

Functional communication, navigation, weapon fire control and electronic warfare capabilities. these

The characteristics bring many differences to the flight test of modern fighters.

Requirements, contents, scale and technology of previous aircraft flight tests.

This paper is mainly based on my flight test practice, combined with foreign third

According to the experience of aircraft flight test, the characteristics of modern fighter flight test are summarized.

Point, organization and management, flight test technology and some existing problems.

1 flight test characteristics of modern fighters

1. 1 flight test sorties and cycle

The flight test of modern fighters is about 1500~4000 times.

The flight time is about 2000 ~ 5000 h. The flight test cycle is about full flight.

The development cycle of the machine is 1/4~ 1/2, and the natural time is 3~8a. as a result of

On such a large scale, it takes so long. The main reasons are:

1) The aircraft envelope is very wide.

For the sake of safety, the envelope of speed, altitude, overload and angle of attack is extended.

The exhibition should be gradually expanded. In the full afterburner state, each point

The clock consumes hundreds of kilograms of oil, so in such a sortie.

Just a few minutes. Such factors will increase a lot of test flights.

Ups and downs.

2) Airplanes have many functions, configurations and weapons.

Modern aircraft have all functions, many combat objects, many modes, and are empty/

Air, air/ground, air/sea; Communication, navigation and identification; Combat, cruise, reconnaissance

Inspection, electronic warfare, aerial refueling, etc. Different tasks and purposes bring many opportunities.

Many different flight test profiles and flight test configurations.

3) There are many new technologies and system redundancies.

Modern fighter is a synthesis of advanced technology, otherwise it is impossible.

Reflect the overall operational performance. This makes the aircraft need to be verified.

There are many new technologies and systems to check. For the reliability of the aircraft.

Most systems adopt the concept of redundancy.

In most cases, normal system and emergency system, system reconfiguration and transfer.

All changes must be verified, which is also an important reason for more flights.

Reason.

1.2 airborne test and ground real-time monitoring

There are thousands of parameters collected in modern fighter flight test, but the ground

There are one or two thousand real-time monitoring parameters.

1.2. 1 Reasons for too many airborne test parameters

1) system is complex, and there are many parameters that need to be tested, monitored and verified.

A redundant digital fly-by-wire control system needs to be collected.

The parameters are about several hundred; The data volume of main bus of avionics system exceeds 1000.

If you want to test and record the internal bus information of each subsystem, it

The amount of information will multiply.

2) Add test sensors.

In order to evaluate the performance of aircraft and systems, understand aircraft and systems.

In the working environment, it is often necessary to test many applications during the flight test.

Variation, vibration, flow, pressure, temperature, etc. , sensors need to be installed.

A lot. There are hundreds of parameters in this section.

3) The need of comprehensive flight test.

In order to improve the effectiveness of flight test and shorten the flight test cycle,

Reduce flight test take-off and landing, adopt integrated flight test technology as far as possible, and require flight.

The parameters of computer examination cover the needs of various occupations as much as possible, so they are added.

The number of test parameters is increased.

4) The concept that the participating aircraft are mutually backup.

Possibility of breakdown or even accident of the participating aircraft.

Sex exists. In order not to affect the progress of the whole project, we adopted

The concept of mutual backup between participating aircraft requires two aircraft.

Test parameters should be able to cover each other, and aircraft parameters should be increased.

Number of tests.

1.2.2 reasons for real-time ground monitoring

1) to ensure flight safety.

The cockpit information of modern fighters is very rich, but it is still

On the whole. It is impossible to display all the subtle changes in the system.

Show it. Even if you can pull up the detailed information, because the test pilot has energy.

Limited, we must rely on ground professionals to help monitor the aircraft and its systems.

Situation.

For those who need to calculate and identify risks through standards

Characteristic parameters such as flutter damping and system stability margin are needed.

Real-time surface calculation and monitoring.

2) Improve flight test efficiency.

Because the ground monitoring has real-time computing ability, the test flight results

We can know in time, so that we can decide whether we can enter the next landing.

Ok, how to do it, and whether it is necessary to supplement the test center or increase the flight test.

And so on, can greatly improve flight efficiency.

1.3 ground support facilities

The flight test of modern fighter depends more on the ground.

Facility support. There are only three ground facilities here.

1) flight simulation

Flight simulation plays an important role in the development, verification and inspection of flight control law.

Optimization plays a vital role. For test flight, it is very important for test pilots.

Training, flight test plan arrangement, task list exercise, flight test result prediction

Measurement and safety measures play an important role, especially for this purpose.

Some risk themes are more important. Take the flight simulator as one.

A training exchange platform can receive more, faster, better and cheaper effects.

2) Avionics Laboratory

This is a system integration, development and verification facility, which has also passed the flight test.

A platform for troubleshooting, making and practicing flight test plans during flight. From the experience,

Look, the comprehensive and easy-to-use flight test site avionics.

System support facilities are very necessary.

3) Ground support facilities of airborne test system

Modern fighter flight test needs very complicated airborne test.

System. The scale and complexity of this system is no less than that of the first airplane.

A large subsystem that collects and records signals transmitted by telemetry.

Types cover almost all signal types of the whole system. for

Ensure that the system has reasonable matching, accurate calibration, reliable integration and simple operation.

Convenient and quick troubleshooting also requires a set of ground support.

A laboratory.

1.4 test flight of other aircraft

The flight test of other aircraft is an important part of the model flight test, which mainly

The main purpose is to reduce the risk of the main engine, shorten the flight test cycle of the main engine and train.

Test pilot.

There are mainly two kinds of testing machines here. One is an air flight model.

Quasi-testing machine; The second is the airborne avionics tester. Air flight model.

The quasi-testing machine is mainly to verify whether the flight control law of the aircraft meets the flight requirements.

Line quality specification requirements, so as to optimize the design; Another main purpose

The purpose is to train test pilots. All new planes of the US Air Force must pass by.

The link of air flight simulation.

The avionics testing machine is responsible for the flight test of modern fighters.

Very important task, because modern avionics system.

High integration, complex software, many sensitive units and many antennas.

High density, very sensitive to the environment, the ground environment is difficult to replace air.

Generally speaking, avionics systems including radar and electronic warfare are all in the air.

The test flight time of other aircraft takes hundreds of flight hours.

In short, the more modern fighters adopt new technologies, the more they try.

Fly over the demand.

1.5 organization and management of modern fighter flight test

The birth of first-class aircraft requires first-class design, manufacturing and

You need a first-class flight test. And you must have a first-class flight test.

A joint flight test force integrating scientific research, flight test and users.

Based on this concept, there are two reasons for the organization and management of modern flight tests.

Then: the principle of test flight and home combination. The so-called joint test flight, that is,

Aircraft and its system development factory, flight test appraisal unit and use

Troops * * * cooperate to organize a flight test team, from making flight test plans and

Planning, handling and analyzing technical problems, with division of responsibilities and consultation.

Business and mutual support. For a big model, being involved in this.

There are hundreds of people on the test flight.

In order to carry out joint test flight, the choice of test flight location is adopted.

Use the principle of Principlesite, that is, try to fly the whole flight as much as possible.

Concentrate in one place. Try to avoid duplication and shorten the cycle, which is also convenient

Concentrate superior forces to make the test flight go smoothly.

2 flight test technology

The application of any new aviation technology should be correspondingly new.

Flight test means inspection and verification. Or test a new action, or

It is a new acquisition and recording method or a new data processing software.

But for modern fighters, it has the greatest impact on flight test technology.

There is nothing bigger than the flight control system of a telex plane. Here, it's just for the sake of

Some flight test topics in this field are briefly described.

2. 1 Flight test of flight control system stability margin

Stability margin test of control system used in general laboratory.

Routine work performed by general-purpose equipment. But in flight.

Many special problems need to be solved to test the stability margin of flight control system.

problem

1) system input

The input of the system is the steering column force or displacement obtained by driving.

It is achieved by the pilot's manual frequency sweep. The frequency is 0.2 ~ 5 Hz. ask

The driver scans continuously from low frequency to high frequency, making each frequency as much as possible.

There is enough harmonic information at this point. The amplitude of the scanning frequency should be large enough to

Overcome the nonlinear influence. The amplitudes at different frequencies also remain as constant as possible.

Keep the same position. At the same time, try to keep flying.

Change. To do this, we mainly rely on the daily training of test pilots, especially

Train on a flight simulator.

2) System output

The selection of system output points should be based on the system state, because flight

The control system is a multi-loop system with a plurality of control surfaces, and the control surfaces

There is a cross connection between them. Generally speaking, the steering column command is taken as input,

The total feedback signal of the system is used as the output to calculate the open-loop frequency characteristics.

The phase reserve and gain reserve of the system can be obtained. special case

In this case, it is necessary to test the stable reserve of a specific control loop as long as

The input and comprehensive feedback signal of this specific control loop are measurable.

Or indirectly measurable.

3) data processing

The system can be obtained by using special frequency characteristic processing software.

Frequency characteristics, but signal filtering is very important, it is straight.

Thereby affecting the validity of the processing result.

2.2 Flutter excitation

Flutter flight test has always been the most concerned course in aircraft flight test.

Because it directly affects flight safety, the mode of flutter excitation is very

Among them, rocket excitation is a traditional flight test method, which is simple and easy to operate.

Single, short action time, especially in the case of full afterburner or dive.

Action time is very precious, but for telex control

In terms of machinery, a new type of flutter excitation system must be adopted, that is, adopting

The airborne signal generating unit transmits various excitation signals through flight control.

The steering gear drives the control surface, thus stimulating the response of the aircraft structure and system. this

The advantage of this excitation method is that the excitation energy of each harmonic is concentrated and the effect is good.

Good; More importantly, this method can measure the output of the required measuring point.

Input signal, so as to analyze the frequency characteristics and get the pneumatic servo bullet.

Stability margin of sex (ASE). The biggest problem with this method is flying.

Incorporate the dynamic characteristics of the control system into the dynamic characteristics of the whole system.

This requires distinguishing these features in data processing and analysis,

So as to analyze the dynamic characteristics of the structure. On the other hand, due to the frequency of the steering gear,

Band limitation makes it difficult to excite structural modes as high as 50~70Hz.

In the future, this requires the choice of excitation amplitude to change with frequency.

The incentive range will also change automatically. If you don't do this, from the low frequency

Use the same amplitude for high frequency, otherwise the low frequency response will be too large, which will affect safety.

All; Either the high frequency response can't be excited or analyzed.

All kinds of incentive methods have their own advantages and disadvantages, and the development trend is to use

A variety of exciting modes are used to carry out flutter test flight in critical state, in order to obtain

Reasonable and reliable results, the price paid is the increase of flying.

Takeoff, landing and time. It is worth noting that atmospheric turbulence is used in flight.

Flutter analysis of airflow response to aircraft excitation is very promising.

Safe and economical. Facts show that in many cases, atmospheric turbulence

The excitation energy is considerable, even exceeding the artificial excitation.

Even bigger.

It should also be pointed out that the flutter excitation used in the flight test of new aircraft

This system (FES) can be used not only for flutter and ASE excitation, but also for.

Flight test of flight control stability margin, especially the stability margin of heading system.

The test flight must rely on this equipment, because it is difficult for the driver to pedal.

Perform a manual frequency scan. FES can also generate other signals for execution.

Flight test of other subjects, such as: step, pulse, "32 1 1", etc.

Operation stability analysis and system identification are of great significance. In short,

FES has unlimited potential for flight test engineers.

2.3 Man-machine closed-loop flight quality test flight

As long as there are manned aircraft, there are manned closed-loop flying objects.

Quality problem. Because the fly-by-wire control system has outstanding high order and high

Gain and time delay, as well as various signals are added to the system.

Cross-linking makes the coupling relationship between aircraft and pilot behavior closer.

Generally speaking, because the control law is constantly optimized.

Iteration makes the fly-by-wire aircraft have excellent flying quality; But in particular,

In this case, if the driver performs a high-gain task, it is possible to form.

Caught in the cliff of flying quality, the man-machine closed-loop coupling vibration is caused.

Swing. Because this situation is beyond the classical open-loop quality index.

Therefore, modern fighter flight test emphasizes man-machine closed-loop flight.

High quality flight test. This kind of test flight is to give the pilot a high gain.

Services, such as accurate tracking, aerial refueling, fixed-point rectification landing, etc. , fly

The results and conclusions mainly depend on the driver's qualitative comments, see reference 1.

Fixed flight parameters, even sorted out some closed-loop performance indicators,

Such as HQDT (Tracking Control Quality). It should be noted that these tests

Flight verification can explain some problems, but not all.

The main reason is that the so-called driver's high income is related to psychology, which is very difficult.

Form and determine. So far, there is not a set of recognized, can be

Performance index used for engineering judgment to identify whether it is possible.

Pilot induced oscillation (PIO). Not only according to the traditional quality specifications,

Check various open-loop index requirements, and also carry out man-machine closed-loop flight.

High quality flight test. At the same time, the test pilot will fly with the stable aircraft.

Conduct quality training.

In particular, the rate saturation nonlinearity is caused by the following factors.

One of the main factors of man-machine closed-loop coupling oscillation. If due to

For example, local airflow disturbance near the runway leads to the steering column.

The correction is too fast and too large, which leads to the saturation of the flight control system, thus making the flight

The phase lag of the machine response control instruction reaches 180, forming

PIO, this is a very dangerous situation. Many telex planes were lost.

Everything is related to this, which should lead to new aircraft developers and flight tests.

Inspection engineers should be alert enough and pay attention to the development of flight control system and the training of pilots.

Do more work in training and flight test projects to prevent accidents.

Healthy.

2.4 Test flight at high angle of attack

The more aviation technology develops, the more important it is to test flight at high angle of attack.

In the past, the research on high angle of attack of fighter aircraft mainly focused on the aerodynamic characteristics of aircraft.

Sex, to prevent the aircraft from entering stall/spin, how to get out once it enters,

Ensure flight safety. At that time, the plane maneuvered only by angle of attack.

The range of more than ten degrees; Today's third-generation aircraft not only study its aerodynamic characteristics.

It is also necessary to study the control law of high angle of attack to make the plane fly normally.

The maneuvering angle of attack extends to the limit range, for example, close to 30 degrees, and

And verify whether the control law can automatically prevent entering stall/spin.

Once in, it can automatically change to a safe range. With vector thrust

With the application of technology, the next generation of fighters will welcome aircraft in a wider range.

Angle as a normal angle of attack, that is, post-stall maneuver, the angle of attack is as high as

Over 50. All these must be verified by flight tests.

The greater the angle of attack, the more reliable the ground wind tunnel data that need flight test.

To verify.

For the test flight of modern fighters, the test flight at high angle of attack can be divided into controllable.

Possible areas and uncontrollable areas within the angle of attack limit.

Control area; Outside the range of the angle of attack limiter, it is uncontrollable. Controllable

In this area, the angle of attack of the aircraft is 20 ~ 30 through flight test.

The operability and stability of the scope; Determine the minimum maneuvering speed and the maximum maneuvering speed.

Xiaoping is flying fast; Check and verify the correctness of the control law of angle of attack limitation.

Sex and reason. In the flight test method, conventional control actions are used,

Such as step, pulse, frequency sweep, longitudinal and lateral heading.

The flying quality of the plane. However, its control range is larger than that of conventional control.

Gradually reaching the extreme value, the control speed is also steep, because at the angle of attack.

In the range of limiter, the stall angle of attack has not been determined, but the minimum machine has been determined.

Dynamic speed and minimum flight speed are very important for the use of troops.

Therefore, the table speed obtained by maintaining a stable 45-degree hover is determined to be the maximum.

Low speed of mobile platform; Take the minimum platform speed achieved by stable horizontal flight as

Minimum frisbee speed; Verify welcome with convergence turn and deceleration turn.

Angle limiter boundary. It should be pointed out that even in the controllable area, large and small.

Appropriate safety measures should also be taken in the flight test at angle of attack. This measure

It should include two aspects: one is to set temporary restrictions in the control law.

Boundary, that is, set two temporary edges with a difference of 2 within the maximum boundary.

The boundaries, namely αmax-4 and α max-2, gradually reach α max; another

The measure is to install an anti-rotation umbrella. Once it is made for some special reason,

The plane entered stall/spin, and normal means could not make the plane.

When refitting, the aircraft can be controlled by anti-spin parachute.

State. With these measures, we can also carry out some more intense

Tactical maneuver to evaluate the reliability of angle of attack limiter. if

These test flights show that the aircraft still has the potential to relax the angle of attack limiter.

On the basis of αmax, the aircraft can be appropriately expanded in increments of 2.

The angle of attack limits the envelope.

After the flight test in the controlled area is completed, it should be carried out outside the α limit value.

Flight test at high angle of attack in uncontrolled area. There are two ways to enter this area: one.

It adopts the straight chain mode of flight control system to directly enter stall/spin.

Test flight, provided that the aircraft is controllable at this time; Another method is manual.

Cut off the angle of attack limiter and the test pilot will let the plane enter through the normal system.

In the uncontrollable high angle of attack region, the stall and deviation of the aircraft should be evaluated first.

Characteristics, functions and reliability of anti-spin mode: finally, I have to

A stall/spin test flight was conducted to determine the aerodynamic characteristics of the aircraft at high angle of attack.

And the recovery method after entering stall/spin.

Flight test at high angle of attack is a high-risk flight test subject.

The biggest risk is that it is difficult to accurately predict the behavior of aircraft. In order to reduce

It is very necessary to reduce risks and make adequate technical preparations, including

Carefully study the wind tunnel test results, especially the vertical wind tunnel test results.

Fruit; Carry out model test flight, find out the spin mode of the aircraft and change the spin.

Methods; On this basis, all-ground simulation and test pilots are carried out.

Training. At the same time, effective anti-spin measures should be formulated and implemented.

Generally, reverse spin umbrella is more suitable. Aircraft test is very important for spin test flight.

It is also particularly important, especially the angle of attack sensor, its range selection and calibration.

The accuracy is more prominent, and it should be specially developed to adapt to the general specification when necessary.

Angle of attack sensor around the test.

Three problems in flight test

In recent years, the cause of flight test has made a qualitative leap.

Technology, facility construction, test pilot training, software development and maintenance support.

Great progress has been made in the organization and management of flight tests. however

However, China's flight test still has many shortcomings.

1) have a superficial understanding of flight test.

Many people simply think that test flight is the last stage of model development.

Section, not from the top, but from its depth as a system.

Engineering science. A new model is often anxious as soon as it is tested.

The correct way is to proceed from the overall project plan.

The test flight should be planned, and the flight should be carried out from the beginning of the aircraft design.

The test design should be reserved for flight test in terms of investment and cycle.

There's plenty of room. It should be recognized that the so-called prototype is only for the purpose of

A testing machine developed to meet the technical requirements. With this

This idea, many test flight problems should be considered in the design.

Test pilots and flight test engineers are part of aircraft design members.

Only in this way, the model test flight will not be too hard and difficult to satisfy.

Elbow, and even left many important problems for the army to use.

2) Insufficient pre-research and technical research.

Flight test is a practical science, which should keep pace with the times.

Many technological developments should be ahead of research. Thanks to the basic work.

Not solid enough, it takes time and manpower to really test the model.

It is not allowed to do detailed work, which will inevitably affect the safety and quality of flight test.

And efficiency; Some of the most basic subjects cannot be fully developed.

3) Other machines were not verified in advance.

One of the basic principles of model flight test is that it can be solved on the ground.

Don't take the problem to the sky; Risks that can be shared on other planes, no

Take it. This basic principle has not been implemented enough. special

Avionics system. The avionics system has the longest flight test cycle.

Actually, there are not many ups and downs, and most of the time I am checking and optimizing the system.

Some functions and performance tests are insufficient. Is the plane still in the army?

Broken cans fall and fly around, and it is difficult to form combat effectiveness. It must be said that this is a kind of

Courses. Ground comprehensive test of avionics software system of American F22 aircraft.

As long as 1 ~ 20000 hours, in the electronic test of Boeing 757 aircraft modification.

The comprehensive flight on board is 400 ~ 500 hours. Their practice is worth learning from.

Draw lessons from.

4) There is still a big gap in the training of test pilots.

Compared with the international level, the theoretical and practical training of test pilots

No, international communication is very insufficient. In some people's minds.

There doesn't seem to be much difference between test pilots and pilots. This is a test flight.

One of the important reasons why the project has not been carried out in depth.

5) Flight test and design are not closely combined.

At present, the depth of aircraft design participating in flight test has changed, but

The design depth of flight test intervention is too shallow, which directly affects

Quality of flight test. It should be said that these two disciplines cannot be related to each other.

But can only be combined with each other, which is conducive to the development of aviation.

Exhibition.

4 Conclusion theory

1) The flight test of modern fighters is characterized by flight test and landing.

More; There are many airborne acquisition records and many real-time monitoring parameters on the ground; On a larger scale

Dependence on ground facilities support; The test flight of other aircraft is a modern fighter test.

An important part of flight work; Achieve unity in organization and management.

The principle of test flight and home court.

2) In flight test technology, the application of fly-by-wire control makes modern warfare

The flight test technology of bucket aircraft is very different from that of previous aircraft, such as flight control.

Stability margin flight test: flutter /ASE flight test: man-machine closed-loop flight products

Quality test flight; High angle of attack flight test, etc. We must attach great importance to it.

3) Although China's flight test technology is much better than before.

However, there are still many problems that need to be considered and changed.

These problems are mainly superficial understanding of flight test.

The lack of pre-research and tackling key problems of flight technology plays an important role in the test flight of other aircraft.

If it is not enough, the technical training of test pilots needs to be strengthened; Flight test and setup

The integration between them still needs efforts.