Chapter 225 Xu Cang takes action!
Before the final approach fix point on the fifth side of Runway 28 at Qitai Airport, a Boeing 737 was already maintaining level flight, preparing to join the glide path after the final approach fix point.
Chen Guoli and a National University Aviation instructor teamed up to verify the single-engine procedure for Qitai Airport's Runway 28. Qitai Airport only has blind landing on one side, and there is no instrument landing system on the other side.
The other runway does not have an instrument landing system because the opposite runway faces the Tianshan Mountains, leaving basically no space for approach.
Qitai Airport had no civilian purpose when it was first built. Moreover, due to the poor environment of the airport's location, the airport's various navigation facilities are very basic. In addition, Qitai Airport is prone to wind and snow, which often covers the road surface in a short period of time, making it difficult to obtain visual references.
Ordinary pilots simply cannot handle this kind of airport, and even younger instructors are not up to the task. Only the best ones have the possibility of landing safely. Therefore, this verification is destined to be only the final backup plan for some special situations.
Chen Guoli and his companion took off from Shule Airport. As soon as they took off, they could see the entire Tianshan Mountain Range. After crossing a gap in the mountains, they arrived at Qitai Airport.
The straight-line distance between the two is very short, and the flight takes no more than half an hour. The only obstacle is the Tianshan Mountains.
Since Qitai Airport is close to the Tianshan Mountains, the terrain conditions in its approach area are extremely complex. The initial approach fix point is just after the top of the Tianshan Mountains. Therefore, after passing the initial approach fix point, you cannot immediately descend and need to maintain altitude. However, due to the need to delay the descent, the descent rate must be maintained at 1,500 to 2,000 feet per minute in the final stage until the fourth turn.
If the descent rate is lower than 1,500 feet per minute, it is impossible to intercept the glide path normally at the final approach fix point. If the descent rate is higher than 2,000 feet per minute, it will easily cause a terrain warning, especially after cutting into the four sides, which will almost certainly trigger a terrain warning.
However, thanks to the reminders from the technical department and the extreme caution of Chen Guoli and his companions, the situation was good until just before reaching the glide path.
"There is an obstacle that needs attention at the fifth and sixth nautical miles. According to the feedback from Qitai Airport, the blind landing glide path is unstable. So we won't press the APP for a while?" asked the National University instructor.
The instability of the blind landing signal at Qitai Airport was not caused by the equipment, which was the conclusion reached after multiple inspections. The only explanation was environmental factors, such as wind and snow.
But in fact, even in the case of heavy snowfall, there are few problems affecting blind landing signals at other airports. This statement is actually not very convincing. Fortunately, the instability of the blind landing signal at Qitai Airport is relatively small, and given the special situation of Qitai Airport, the matter was finally tacitly accepted.
If it is a plain airport, occasional instability in blind landing is not a big deal. But under the complex terrain of Qitai Airport, you have to be careful. Unstable blind landing signals may lead the aircraft to a sudden descent rate. Once it hits the terrain on the fifth side, the risk factor is too high.
Therefore, faced with this situation, not pressing the APP as mentioned by the instructor of NUS Aviation is a solution.
The most threatening thing during the final descent phase at Qitai Airport is a mountain peak six nautical miles away. Basically, after passing this peak, even if there is a sudden high descent rate, it will not really cause too much danger.
And according to the airport feedback, at low altitudes, blind landing signals are more stable. Therefore, as long as you pass the six-nautical-mile mountain, the rest will be much safer.
Since there is obvious instability in the blind landing signal from the final approach fix point to five miles and six nautical miles, and it is mainly concentrated on the glide path, the G/S method is not used, but V/S is used manually to follow a rough descent trajectory.
The instability of blind landing signals, especially glide path signals, is usually manifested by a sudden twitch of the glide path signal point. Sometimes it twitches to the bottom. Then the autopilot thinks that the aircraft is above the standard glide path and will generate a large descent rate in an attempt to catch up with what it believes to be the standard glide path, resulting in an unexpectedly large descent rate of the aircraft and causing terrain impact.
However, this twitch usually only lasts for a moment and will not last for a long time. Therefore, the crew can roughly refer to the glide path signal and manually push out a stable descent rate. In this way, even if the glide path signal is temporarily crazy, the aircraft will still descend at the previously set descent rate without G/S and AP connected, and there will be no steep descent.
However, this only applies to short-term unstable glideslopes. If the time is too long, the pilot will not know whether he is still on the standard glideslope. After all, the speed of the aircraft is constantly changing slightly, and there are airflow effects. If you want to always stay on the standard glideslope, it is impossible to keep a constant descent rate all the way.
In a short period of time, even if there is a deviation, the difference will not be very large. Once the glide path signal stabilizes again, the descent rate can be corrected. However, if the glide path signal is unstable for too long and the pilot has no reference, it will be more dangerous. After all, not everyone can calculate the real-time descent rate from the ground speed in real time like Xu Cang.
The final approach positioning point of Runway 28 at Qitai Airport is approximately fifteen nautical miles from the head of the runway. This is considered a relatively long final descent phase, and usually this length is maintained at around ten nautical miles.
The altitude of intercepting the glide path was 3,900 meters. Chen Guoli had done a good job before. After cutting into the final leg, he kept level flight for a short time, so the workload was relatively light.
"Well, let's establish the configuration first. After passing the FAF point, I will manually push the descent rate." Chen Guoli looked at the airspeed indicator: "Speed is less than 170, flaps 25."
The model this time is not the 737-800, but the smaller 700 model. Therefore, when lowering the flaps, after flaps 15, you have to lower flaps 25 as a transition, while on the 800 model, after flaps 15, you can directly lower flaps 30.
The NUS instructor glanced at the airspeed indicator, confirmed that there was no problem with the speed, and then moved the flap handle to the 25 position.
Chen Guoli immediately began to slow down. When the flap indicator reached the 25 position, Chen Guoli almost did not pause and directly ordered: "Speed less than 165, flaps 30."
The NUS instructor followed instructions and moved the flap handle to the last thirty position.
"21 meters against the wind..." The NUS instructor reminded Chen Guoli when he saw him making the final speed adjustment.
As soon as Chen Guoli touched the speed knob, he was stunned for a moment: "Where's the crosswind?"
"14 meters, positive crosswind. The good news is that we don't need to factor it into the wind correction. The bad news is that we have reached the limit of crosswind." The NUS instructor had a serious expression on his face: "Instructor, I'm afraid it will be difficult to fly."
Given Chen Guoli's age, even this NUS instructor had to call him "Instructor". However, this did not mean that this younger NUS instructor was inexperienced. On the contrary, he was a pilot who could convince everyone in an airline like NUS Airlines and was definitely very capable.
If nothing else, the headwind is 21 meters and the crosswind is 14 meters. This is a very troublesome airflow environment no matter where it is placed.
"Runway braking effect?"
The NUS instructor seemed well prepared. "Just now they reported that there were still 4, but now it's estimated to be only 3, and it's still snowing outside. Instructor, according to the QRH landing distance table, plus a 15% margin, it just matches the length of Runway 28 at the airport. Instructor, you can't drift anymore. If you drift a little longer, the plane may not be able to stop."
Runway braking effect is an indicator of the friction coefficient of the runway surface, ranging from 0 to 6. The larger the number, the higher the friction coefficient. Generally speaking, 5 and 6 are considered relatively good. A runway braking effect of 6 generally refers to a dry runway. If the runway braking effect is 0 or 1, takeoff and landing are basically not allowed.
Qitai Airport has rain and snow all year round, so there is basically no dry runway. Runway braking effect 3 or 4 is a normal situation, and it is not that Chen Guoli is unlucky. However, the runway of Qitai Airport is short, so the braking distance of the aircraft is more dangerous.
Whether it was the final airflow or the braking distance, it was an unprecedented challenge for Chen Guoli. No wonder Bi Lin wanted Xu Cang to do it. This was with two engines. If it was a single engine, the difficulty would be even higher. This was a bit unreasonable. Even Chen Guoli was not sure.
Finally, Chen Guoli set the wind correction to 10. If it was too large, the subsequent approach speed would be difficult to control, and it would be too close to the bottom of the red and black speed band, making it too easy to exceed the speed limit. After a while, the descent began, and the airflow must have been quite unstable. If the wind correction was set too large, he would have almost no room for maneuver.
However, if you really set it up according to the headwind, the wind correction of 10 knots is definitely too low, and you will probably have to be more cautious about reducing the throttle later. Otherwise, if you reduce the throttle a little too early or too quickly, the plane will definitely fall down uncontrollably.
At the altitude of Qitai Airport, once the plane starts to sink, it will be difficult to save it even if you add throttle.
Seeing Chen Guoli's solemn profile, the NUS teacher suddenly made a suggestion: "Teacher, should we land with flaps 40?"
In theory, flaps 30 and flaps 40 are both normal landing configurations. However, most people don't use flaps 40 for many reasons. However, the most intuitive change of using flaps 40 is that it can effectively reduce the approach speed, which is undoubtedly of great help in shortening the braking distance.
However, if flaps 40 are used, the speed range will be further reduced, which further compresses Chen Guoli's maneuvering space. In the low-altitude turbulence behind, Chen Guoli needs to maintain the airspeed more accurately, otherwise it is easy to cause overspeed or stall.
Chen Guoli could understand the intention of the NTU instructor, but after thinking about it, he finally refused. He did not have the confidence that he could really maintain the airspeed accuracy at low altitude.
At 0.2 nautical miles before FAF, Chen Guoli derived a descent rate of 950 feet per minute based on the ground speed. At such an altitude, the ground speed is a bit higher, so the standard descent rate will also be relatively high. However, the descent rate of 950 feet per minute derived from a normal configuration is indeed a bit outrageous, which shows that Qitai Airport cannot be judged by common sense.
The reason for slightly earlier departure is that it takes a certain amount of time for the aircraft to establish a descent rate from level flight. If you really wait until you pass the final approach fix point before pushing, it will be too late.
However, 0.2 nautical miles in advance is actually a bit late. At least when the aircraft passed the final approach fix point, the aircraft's descent rate was just over 700 feet per minute. This is also the reason why Chen Guoli pushed the initial descent rate to be relatively large.
About five seconds after the actual descent rate of 950 feet per minute was formed, according to the glide path signal, the aircraft was clearly on the standard glide path, but Chen Guoli reduced the descent rate to 900 feet per minute in advance.
Pilots cannot just focus on the glide path signal, but must adjust the descent rate appropriately after referring to the ground speed changes and all advance amounts so that the aircraft can obtain a smooth and consistent glide path.
In fact, if the required navigation performance technology is widely used and matured, the computer can calculate the specific value of the aircraft's deviation from the standard glide path on the fourth page of the progress page, and even provide a reference descent rate value.
However, this glide path is calculated through GPS signals, and there are slight differences from the signals provided by the blind landing equipment, especially when the temperature deviates too much from ISA. The greater the deviation value, the greater the difference between the two glide paths.
According to the temperature of Qitai Airport, there is indeed some gap between the two, but it still has certain reference significance.
This manual glide slope tracking operation is not difficult for instructors of Chen Guoli's level. He is not unfamiliar with the need to use this technique occasionally when flying to some complex airports.
However, since the airflow on the final leg was too chaotic, Chen Guoli needed to constantly correct the throttle in order to keep the airspeed within a relatively stable range.
After passing six nautical miles, Chen Guoli pressed the APP button, the aircraft intercepted the glide path, the descent rate window value disappeared, and the autopilot began to automatically correct the descent rate based on the blind landing signal.
"Tower, 1533, No. 28 has made a blind landing."
Since this is not a commercial flight, the call sign is replaced by the aircraft number.
"1533, surface wind now 310/16, gusts 18, light snow and wet runway, corrected sea pressure 1031, clear to land, watch out for final airflow."
"Corrected sea pressure 1031, runway 28, clear for landing, 1533."
As soon as the teacher of the National University finished reciting, Chen Guoli cursed secretly. The wind was getting stronger and stronger. The automatic driving could barely maintain it, but the automatic throttle could not keep up at all.
The Boeing 737's autothrottle was so incompetent compared to the 320 that Chen Guoli had to constantly intervene in the throttle. At about 1,000 feet above the ground, Chen Guoli couldn't stand it anymore and directly disconnected the autothrottle and took control of the throttle himself.
However, at the moment the automatic throttle was disconnected, the automatic driving could no longer withstand the influence of the airflow and disconnected by itself.
Chen Guoli immediately took control of the steering wheel with his left hand when the autopilot was disconnected. Chen Guoli was prepared for this, so even when the autopilot was on, he kept his left hand on the steering wheel, which allowed him to take over the flight immediately if the autopilot was suddenly disconnected.
However, as he manually flew, Chen Guoli could not help but sweat on his forehead. The plane was like a small boat on the crest of the wave, up and down, left and right, and violently bumping without any rules. He had set the wind correction value to a relatively small value, but the airspeed was still approaching the bottom of the red and black speed band from time to time, and sometimes it was less than the Vref speed, close to the yellow zone speed.
"What the hell is this!"
Chen Guoli cursed involuntarily while concentrating all his energy on controlling the plane. He had been flying civil aircraft for more than 20 years, but this was the first time he encountered such turbulent air currents. No wonder the autopilot could not maintain its position.
However, Chen Guoli really has real skills. Even though the airspeed fluctuated up and down, he was just about to exceed the speed limit or stall each time, but he always stopped at the last moment, and the speed was always within the specified range. This skill is also amazing.
After passing 500 feet, the airflow increased instead of decreasing, and Chen Guoli was almost unable to hold on. Moreover, due to the extremely strong crosswind, the nose of the plane was not facing the runway, but was approaching sideways at an exaggerated angle of almost 30 degrees.
"One hundred is the final decision." The teacher from the National University felt his palms sweating even though he was watching from the side: "It's almost on the ground, hold on a little longer, teacher!"
At this moment, the air pressure altitude was three hundred feet above the airport's altitude, and we were close to landing.
"Hold!"
Chen Guoli was really going crazy, but he still gritted his teeth and tried his best to land the plane. The only reason that supported the two of them was that the speed, localizer, and glide path were all within the deviation limit. According to the regulations, they could continue to go down.
I have to say that Chen Guoli really has solid skills.
At an altitude of about one hundred feet, the turbulence finally became smaller.
Chen Guoli shouted, "Go back, listen to my orders, monitor the missed items, and take decisive action when necessary!"
In such an environment, even Chen Guoli, although he had reached an altitude of 100 feet, was still unsure whether he could land and had to be prepared for a go-around at any time. Moreover, what was even more fatal was that in a low-altitude environment, the turbulence was smaller, but the crosswind volume unexpectedly increased a little.
The drift angle was already large, and now the direction of the nose of the plane was at an angle of more than 40 degrees to the centerline of the runway, which was simply terrifying.
However, Chen Guoli also had superb skills. When the radio altimeter of the aircraft reported ten feet and before landing, he pushed the left rudder and actually straightened the nose of the aircraft in the air. This kick alone was a real effort.
Many pilots, even captains, dare not use the rudder in the air. Instead, they wait for one wheel to touch the ground first and then straighten the plane before the other wheel touches the ground. How could Chen Guoli straighten the plane in the air?
Even the NTU instructor sitting on the right seat had his eyes light up when he saw Chen Guoli's steering operation, and couldn't help but exclaim: "How amazing!"
Chen Guoli had done a good job, almost straightening the plane with one kick, but he was not Xu Cang after all, and could not push the nose of the plane exactly. Under normal circumstances, this slight difference would not be a big deal, but for a slippery runway like Qitai Airport, this slight deviation would be fatal.
Because the left landing gear was not fully aligned, it touched the ground a little earlier than the right landing gear. Single-wheel touchdown is a common situation in strong crosswinds, but as soon as the left landing gear touched the ground, it did not catch the road surface, but instead produced an extremely obvious side slip.
In the cockpit, after feeling a clear touchdown, Chen Guoli could now use the centerline of the pavement as a reference, and could already see the slight flaws he had corrected. He was about to straighten the plane completely, but suddenly, the entire fuselage of the plane slid to the left.
Chen Guoli was horrified. Without a second thought, he stepped on the accelerator and shouted, "Go!"
…
"It took four tries before it landed?"
At the door of the preparation room, Xu Cang listened in disbelief as Lu Jinghua described everything that happened at Qitai Airport.
After Chen Guoli made a go-around, he tried again, but the second time he didn't even reach the decision height and had to go around because the aircraft's state deviation was too large. After another round, Chen Guoli asked the instructor of the National University to try again, but it didn't work. The fourth time, Chen Guoli tried again, and finally landed.
For a pilot of Chen Guoli's level, it is rare to circle so many times before landing.
"I heard that after Teacher Chen came down, his shirt was soaked. You know, the temperature at Qitai Airport was more than ten degrees below zero. The teacher from the National University turned pale." Lu Jinghua also found it unbelievable, because he knew the teacher from the National University. That person was not a fool, but a real capable person. How could he be scared like this?
"Is it so difficult to fly?" Xu Cang knew that Qitai Airport was difficult to fly, but he didn't expect it to be so difficult and put so much pressure on the two instructors.
"It seems that the teacher from NUS refused the subsequent single-shot verification after landing." Lu Jinghua said.
According to the plan, the aircraft would be tested for single engine operation after a short repair at Qitai Airport. However, if the aircraft was flying with two engines in such a dreadful way, how could it fly with a single engine? Wouldn't that be courting death?
Based on this idea, the instructor of the National University directly refused to take off. As a result, the crew was short of one person, which was difficult to deal with.
Xu Cang sighed: "Are you scared to death?"
I guess this instructor will have a psychological trauma towards Qitai Airport in the future.
Suddenly, Lu Jinghua said, "What about you?"
"Me? What's wrong with me?" Xu Cang was stunned, and then he immediately thought of the agreement he had made with Bi Lin, and suddenly felt that something was wrong. Just as Xu Cang was thinking about this, his cell phone suddenly rang.
Xu Cang looked at the vibrating phone, gritted his teeth, and answered it. Before he could say anything, Di Qingquan's voice came from the other side: "Xu Cang, do you know about the Qitai Airport incident?"
"Got it." Xu Cang said in a low voice.
Di Qingquan said in a very serious tone: "If it is convenient, please come to Shule as soon as possible. It seems that you are needed to take action!"
