Chapter 11 Thrust Attenuation
Jianchuan City has a special geographical location, with warm winters and cool summers, which is where many birds spend the winter. Moreover, the airport is remote, so the number of birds is even greater.
The captain stretched himself and saw the bird-scaring vehicle on the path at the edge of the runway. Fireworks were occasionally blasted in the sky. It looked like another crew had reported a bird strike, which made the airport anxious.
If there are too many bird strikes, the airport will be ordered to close in the worst case scenario. It would be a laughing stock if Jianchuan Airport was temporarily closed by the authorities because of this.
Seeing that he would have to wait for a while, the captain simply pulled the parking brake, turned off the taxi lights, pulled the seat back, and nestled into the seat, looking very comfortable.
As the cockpit became quiet, Xu Cang could feel that the fuselage of the aircraft seemed to be shaking all the time, and it was not caused by the engine running.
"It's windy!" The captain put his hands behind his head and lazily turned his head to look at the wind bag beside the runway: "This damn place is really unlucky. The thunderstorm season has just passed and the wind season has come."
The co-pilot followed the captain's gaze and saw that the wind bag was blown straight and parallel to the ground and was still rotating, which indicated that the wind direction was very unstable.
"It's not even afternoon yet. Won't the wind be stronger on the way back?"
As soon as the co-pilot said this, the tower issued an order: "Flying feather 6321, clear to enter runway 23 , corrected sea pressure 1020."
The captain, who thought he would have to wait a while, suddenly stood up, stepped on the parking brake, increased the throttle a little, and scanned the runway and the fifth approach to confirm that there was no risk of runway incursion.
The first officer responded to the tower, turned on all exterior lights, activated the terrain display on his side, pushed the weather radar test button, and switched TCAS to TA/RA.
"Runway five is safe, takeoff thrust 93.5." The co-pilot opened his mouth, and it seemed that Xu Cang was not the only one who felt sleepy at work.
While the aircraft was aligned with the centerline of the runway, the tower control gave the take-off instructions.
"Feathers 6321, surface wind 15012, gusts 15 meters, runway 23 clear for takeoff."
"Runway 23 is clear for takeoff, flight feather 6321!" The co-pilot raised his eyebrows. "When we were preparing, the METAR showed only a steady wind of seven meters. How did it change so quickly?"
Even though the captain and the co-pilot seemed lazy before, once the plane was about to take off, both of them focused their minds and sat up straight.
When the plane was about to align, the captain pressed the timing button and started to push the throttle forward, saying, "The wind is a little unstable. Watch out for wind shear."
"Hmm!" the co-pilot responded, knocking on the handle of the side window and adjusting the seat position to make himself more comfortable. Finally, he quickly scanned the takeoff configuration and confirmed that it was correct. Noting that the thrust had stabilized at 40%, he did not hesitate and shouted directly: "Good direction, takeoff thrust is stable!"
"Let's go!" The captain immediately pressed the TO/GA switch, and the two CFM56-7B24 engines roared into life. The power of up to 220,000 DaN pushed the fuselage weighing tens of tons to accelerate continuously.
Xu Cang bent his head, boredly looking at the runway centerline markings that flew by in front of him, and heard the standard shouts from the captain and the co-pilot. Although the content was roughly the same, there were still some differences in the details. Even in the standard operating procedures, there were differences between different companies.
Suddenly, Xu Cang felt the plane shake, and even the taxiing direction changed . Xu Cang had not paid close attention to the plane's status. After all, he was not operating a flight, so there was no need to be so diligent. Subconsciously, he thought it was caused by the air current.
As the aircraft speed increases, the effect of the aircraft's control surfaces becomes stronger and stronger, and the impact of turbulence on the aircraft begins to become obvious.
However, what was originally thought to be just a minor incident turned out to be that the plane's taxiing direction became increasingly unstable afterwards.
"Hmm?" Suddenly, the co-pilot noticed that the thrust of the No. 2 engine had fluctuated slightly. However, he hesitated for a moment, because the thrust of the engine was not constant, and very small changes were normal.
However, after a moment's hesitation, the thrust of the No. 2 engine suddenly dropped from the preset standard thrust of 93.5 to 91. A 1% change in N1 speed is acceptable, but a sudden drop of so much is obviously a problem.
The co-pilot did not wait any longer and immediately reminded the captain: "Brother, the thrust of the No. 2 engine is abnormal."
While the co-pilot was talking, the thrust of the No. 2 engine dropped from 91 to below 80. Now, there was a significant thrust difference between the two sides, and the already unstable taxiing direction instantly worsened.
"Not good!" The captain spared his attention and quickly glanced at the engine display of the upper DU, and immediately locked onto the abnormal N1 of the No. 2 engine.
As the pilot, most of his energy was focused on the outside during the takeoff phase. Just now, the plane was shaking, and he thought it was caused by airflow, just like Xu Cang, but now it seems that it may be caused by unstable thrust caused by engine failure.
At this point, the aircraft speed had exceeded 80 knots, and only engine failure would meet the conditions for aborted takeoff. But now that the thrust of the No. 2 engine was continuously decreasing, did it meet the conditions?
In this case, the engine seemed to have failed, but it had not completely failed! This kind of ambiguous situation is the most annoying. Perhaps because he had never encountered such a situation before, the captain was a little undecided for a moment.
The decision to abort the takeoff can only be made by the captain in charge. The co-pilot was nervous and waiting for the captain's decision. Suddenly, the cockpit fell into an eerie silence.
Although the captain hesitated, he did not give up control of the aircraft's status . Even when the thrust of the No. 2 engine continued to decline, the aircraft's taxiing direction was stabilized.
Moreover, the captain's hesitation did not last too long. In just over a second, he made a decision: "Interrupt!"
A reaction time of one second cannot be considered as a quick decision, but it is definitely not an excessive performance.
But the moment he called out the abort, the co-pilot was ready to cooperate with the captain to abort the takeoff. However, a roar suddenly came from behind them: "Go ahead, V1!"
One second is just the time it takes to blink twice, but in that one second, the plane increased its speed by six knots, directly exceeding the V1 speed. However, this plane did not have V1 electronic transmission, and the co-pilot was distracted by the abnormality of the engine, so he did not notice that the speed of the plane had exceeded V1.
Only Xu Cang, who was standing behind him, saw it! So, he spoke!
At this moment, the captain showed a decisiveness different from before. He did not even verify Xu Cang's words himself, and stopped the movement of his right hand on the throttle lever.
He did it!
