As a test pilot, you must understand all kinds of knowledge in test flights, and this pilot induces concussion, which is the most dangerous one.

The MIL-STD-179A standard defines PIO as: "persistent or uncontrollable aircraft oscillations caused by the pilot's attempt to maneuver the aircraft." Its essence is the poor coupling between aircraft dynamics and pilot dynamics.

This undesirable phenomenon is rare and unpredictable, and can happen to someone, even an experienced pilot.

Because the term "pilot-induced concussion" makes people think of the cause of the accident on the pilot, in fact, most of the aircraft that have this situation have problems with the control system itself, so some people call it Aircraft Pilot Coupling (APC). This avoids placing the blame and responsibility for the PIO phenomenon on the driver.

This is mainly due to the design flaw of the aircraft, when the aircraft oscillates in flight, the pilot will instinctively use the steering stick to eliminate the shock, as if to apply a force to stop the oscillating swing. However, due to a defect in the aircraft's control system, the force exerted by the pilot did not reduce the shock, but rather exacerbated it. It's like when the swing is at the top, push it again. The concussion of the plane became more and more severe.

Whether it's PIO or APC, it's a different name for pilot-induced concussion. In the fly-by-wire system, the main reason for this failure is that the software control law design of the fly-by-wire flight control system is not perfect, which leads to a lag between the actual evaluation and transmission of the pilot's control input control surface.

In normal flight, this lag is basically negligible and will not affect the handling. However, this is not the case when fine altitude adjustments are required during take-off and landing, and the manoeuvring lag is likely to cause a significant asynchrony between the pilot's input and the aircraft's actual response, forcing the pilot to increase his maneuvers, which in turn will cause greater asynchrony and eventually lead to loss of control of the aircraft.

So, it's almost always a problem that arises during the take-off and landing phases.

After talking for a long time, if you give a simple example, when landing, the fighter began to bow its head, and the pilot pulled the operating stick back, wanting to reduce the bow, but pulled too much, and the fighter began to raise its head, so the pilot pushed the operating stick again, originally wanted to reduce the situation of raising his head, but he lowered his head again, so that the plane bowed his head even more.

If the plane does not get out of control several times like this, it must be God forbid.

That's the problem with PIO, a terrible test flight.

Qin Feng knew this thing, and it started with the prototype of the F-16, that is, the YF-16 test flight.

In the high-speed sliding, it is necessary to pull the rod to see if the aerodynamic layout is appropriate, and to see if the tail rudder can pry up the nose of the aircraft.

As a result, there was a problem with the design of the flight control rate of the YF-16, and the test pilot pulled up the operating stick, wanting to make the plane look up, but unexpectedly, the maiden flight began like this, and it actually flew!

The moment the test pilot found out that he was going to fly, he hurriedly pushed the operating lever, but it was useless, the plane had already flew, and this push, the plane lowered its head again, like a small boat in the waves, and repeatedly swayed back and forth several times, and finally came down again, fortunately not falling off the fighter.

If it is said that it was imperfect in the early stage, then it was the same in the later period, when the YF-22 was tested for this reason, one fell for the same reason, the plane was scrapped, and the test pilot was able to climb out of the cockpit by himself, which is another miracle.

And our own J-20 fighter, during the test flight, also had this phenomenon.

The J-6 fighter was converted into a stabilized aircraft, with fly-by-wire operation, and the first flight control software designed by the other side.

At this time, experienced pilots are needed to fly, and they must have professional training in this area.

However, there is no such condition in the country.

After the plane is built, someone has to fly it, and the question we are facing now is who will fly.

Back then, this test flight accident of the YF-16 had already been reported by an aviation magazine, explaining the process in detail, anyway, the F-16 has begun to be sold everywhere, which is not a leak.

Then, Qin Feng also studied that many planes have this phenomenon.

In fact, a hundred years ago, the Wright aircraft had a PIO or PIO trend, and the pilot was always in an unstable over-maneuvering state during the flight, and the magnification time of the aircraft's pitch attitude divergence was about 0.6s. Since then, there has been a PIO or PIO trend in many conventional and modern aircraft.

Tu-144 supersonic airliners and F-8 fighters have also had this kind of problem, although they are hydraulically operated, but also because of the lag of the operating system, coupled with the pilot's operating amplitude, there was a large swing in the end.

"I'll fly." Qin Feng said again: "I know that there is a great danger in it, but if we don't touch it because there is danger, then how can we progress?" ”

"If this happens, the best thing to do is to adjust gently, gently, slowly." Qin Feng said.

This is also the introduction of that article, even if there is a problem with the control rate, as long as it can be operated gently, it will eventually fall gently, and when adjusting, the slower the better, and you can't be impatient.

Of course, the original words in it were to stroke gently like stroking a woman, and in this case, Qin Feng couldn't say it in front of Lao Zhou.

"Besides, we still have mechanical backup, when it is critical, let's switch to mechanical backup, rest assured." Qin Feng patted Lao Zhou's shoulder vigorously.

The use of J-6 training aircraft, front and rear two-seater, just to keep a backup, hearing Qin Feng's words, Lao Zhou finally nodded: "Yes, only you come to fly, we can rest assured, but you are very dangerous." ”

Whoever flies is dangerous, and Qin Feng is no exception.

Qin Feng nodded, danger, he is not afraid, as long as the domestic aviation industry can progress, it is worth his sacrifice.

Suddenly, Qin Feng's hand touched the peace charm.

Even if Qin Feng is a straight man, he can feel the tenderness in Gu Tingting's eyes, and there seems to be a father's voice in his ears again, the girl brought from the city is better, and she is still waiting to hold her grandson.

If you sacrifice, what about your lover? How much damage will it cause her? In this case, it is better to reject Gu Tingting and let her find an ordinary person to marry, it is better than being frightened like this, right?

Test pilots, a lifetime of danger.

Qin Feng's heart was extremely conflicted.

"By the way, our test flight institute has spent a lot of money to import their most advanced 'Daming' TT&C system from France, and it will be much easier for us to conduct a test flight." Suddenly remembered something, Lao Zhou said.

France's latest measurement and control equipment is really good, and it can be transmitted directly to the ground!

Qin Feng is also happy, that's great, go take a look!