Exactly a decade ago, on November 1, 2011, Lotte’s Boeing B767 landed at the airport without a long landing gear. Chopin In Okęcie Warsaw. The difficult and dangerous maneuvering was carried out perfectly by the crew, and then the evacuation was carried out with equal efficiency. As a result, none of the 231 people on board were injured, and the event became popular all over the world.
Since it was quickly created, as a rule, the emergency landing gear extension system worked. Only he had no power supply, because the C829 circuit breaker was turned off in the cockpit for an unknown reason. When pressed down, the landing gear of the aircraft raised from the waist was easy to extend.
Scrutiny incident It took the experts nearly six consecutive years to make their recommendations. The comprehensive report of the State Commission for the Investigation of Aircraft Accidents in 2017 describes exactly what happened. Although there are no specific answers or indications of blame.
All through the hose and valve
LOT’s B767 took off from Newark Airport near New York just before dawn Polish time. The inspections conducted by the American technician Captain Wrona and co-pilot Jerzy Schwark on the plane did not show anything abnormal. Only in the air the sensors detected a pressure drop in one of the hydraulic systems responsible for extending the landing gear. After consulting with the ground, the crew decided to fly to Warsaw and extend the landing gear in emergency mode. Regardless of the apparently damaged hydraulic system. After seven hours over Poland, to the consternation of the crew, this emergency system was not working. Consulting the floor, resetting the systems, checking the positions of the selected switches and fuses did not help. Attempts to force the landing gear by gravity and the sudden movements of the aircraft also failed.
Examining the plane, specialists quickly found, even before it was removed from the landing site, the root cause of the whole situation. One of the hoses in the hydraulic system has failed. As mentioned, it was partially a LOT error. As early as 2000, Boeing’s concerns stated that the installation of this version of the duct, which went into production in 1995, was faulty. It has been subjected to loads greater than it should have, and sometimes it breaks. Therefore, a modification of hose connections and a new method of their installation were developed. A set of parts and relevant instructions for conversion are included in the so-called technical bulletin, which is communicated to all users of the device. However, it was given low priority, so making adjustments was optional. LOT decided not to implement it, relying on its “own evaluation and prior experience”. According to the standards, the cable was checked every three thousand hours in the air. The last time technicians checked it was in March 2011 and didn’t find any problems. Eight months later, it cracked where Boeing thought it was likely to be.
Regardless, the aircraft’s landing gear must be able to glide using the emergency electric motor. Therefore, the possibility of wire breakage does not cause alarm. There was always stock, chances were small so modification was optional. But on this unfortunate trip, the emergency system didn’t work either. He had no right, because his power was interrupted simply by turning off the circuit breaker C829. Why didn’t the crew notice this? The commission was unable to state unequivocally.
The circuit breaker C829 is located in the lower left corner of panel P6-1. So he was above the ground behind the seat of the first officer, who was checking the position of the valves and switches at critical moments. The captain, seated in his left seat, could not see him. The co-pilot, sitting alone, can make a lot of effort, but he has little chance of this. However, during the flight, he got up from his seat and walked around the cockpit. He even looked at board P6-1, where the C4248 circuit breaker is also located, directly controlling the power supply for the emergency landing gear extension system. However, this was placed at its top, about 30 cm above the ground. was pressed. For some reason, the C829 pilot, turned off a little less, which was a collective fuse, the second layer of protection, among other things, for the extension of the emergency landing gear and a few others, worked only in rare cases of emergency. The aircraft’s electrical and electronics systems are built in such a way that this fact is not indicated anywhere. He was also not mentioned in the emergency procedures.
In its analysis, the commission concluded that such oversight was possible due to the difficult and stressful situation of the co-pilot. He’s been flying for hours, knowing that his main landing gear extension system is malfunctioning. The critical phase of the flight, the landing, was approaching. In addition, for reasons he did not understand, the emergency landing gear extension system did not work. Not all the emergency instructions on the plane helped solve the problem. At the same time, he had to communicate with air traffic control, two F-16 fighter pilots escorting the B767 in the last hour of the flight, and above all, consult technical experts on the ground and follow their instructions. Everything was under a lot of pressure and on his own as the captain was focused almost exclusively on driving. In such a situation, according to experts, he could have missed the fact that the fuse was extinguished, whose importance was not informed by emergency procedures or specialists on the ground. Once he checked the P6-1 board, he focused on the C4248 fuse switch and did not take a quick look.
Accident investigation experts have emphasized that in modern aviation, routine and automatic procedures of the crew and strict adherence to procedures are of great importance. Only in third place is independent analysis and critical thinking, and there may be no time and place in an emergency and stressful situation.
The committee also tried to explain why and when the C829 actually turned off. Unfortunately, there was no clear answer here either. The fuse was checked in several ways and shipped to United States of America. All tests confirmed no problems and correct operation. So the explanation remained that he was accidentally stopped by someone in the cockpit. The crew testified that before takeoff they checked the location of all the fuses, and confirmed this by signing a relevant document. So the C829 had to be pressed to the ground in the USA, because no one noticed that it wasn’t. It had to be turned off somehow later, after a pre-departure check. When and why remain unexplained.
But experts have discovered that airlines have reported problems with the P6 board in the past to Boeing. Because it was located above the ground and behind the co-pilot’s seat, the valves were accidentally pulled out. Whether it’s during cleaning, whether it’s accidental with the foot, or due to crew bags containing documents. Boeing noticed the problem and first introduced additional paid covers for the entire panel. It then introduced it as standard equipment, but not until a few years after the LOT’s B767 was in production. The Polish airline did not decide to purchase an additional cover.
accident without sequelae
Experts from SCAAI do not judge. They do not utter guilt. They don’t accuse anyone. they just say facts and make recommendations. In this case, they only recommended a few changes to the pilots’ instructions in case of problems with the landing gear and adding one if landing without it. Boeing rejected the Polish proposals. The Americans stated that the instructions should not be overly complicated, but should be as simple as possible and assume that the crew will first check the location of all relevant valves:
The checklist instructions indicate that before the start of the NNC checklists, the controls on each system are assumed to be in the normal configuration of the flight stage. For the event under consideration, normal configuration means that the relevant valves are in the correct positions (closed)
Similar recommendations on actions were directed at LOT. Partially implemented by the Poles. They also confirmed that they turned to the American company with a question about the possibility of installing covers for valve plates. In addition, minor improvements in the operation of the rescue system at Chopin Airport were recommended, and this was done.
It is a task, perhaps, to hold those involved in the accident to account Prosecutor’s Office. This, however, did not find it appropriate to do so in this case. On the contrary, the crew of the machine were honored as heroes and received state honors. The plane itself ended up donating parts and scrap. The emergency landing caused serious damage to the fuselage, and its removal in such an old machine (24 years old) was considered unprofitable. First, salvageable engines were sold. The rest of the machine was sold for parts just over six months later. After two years of emergency landing and dismantling anything of value, it was shredded to scrap.
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