The hidden danger. Accident 1991.
Morning. March 3 1991 years. After a short 17 minute flight from Denver, flight 585 companies "United Airlines"Landing in Colorado Springs. It was a great day, but meteorologists reported that Colorado Springs expected strong turbulence and wind gusts. Commander Boeing 737 52 years was Harold Green. He was a pilot with 20 years of experience and an excellent reputation. All about the series:The hidden danger. Accident 1991. read below ...
In the municipal airport in Colorado Springs air traffic controller is ready to take flight 585. Soon, the pilots saw the aircraft airport. They got a good approach and began to decline to the band 39. By reducing the speed of flight 585 become more sensitive to turbulence. Therefore, the co-pilot asked for details of the landing of other aircraft. They were told that because of the gusts of wind there was a brief drop in speed at an altitude of 150 meters.
Coming down, the pilots experienced some difficulties due to the strong wind. However, they coped with it. From the windows of the airport tower controller observed the final stage of the approach flight 585. The closer the airport, the plane started to shake strongly. Suddenly, unexpectedly, Boeing 737 began to go out of control. His start spinning and he went into an uncontrolled spin. Pilots could not do anything. Manager watched Boeing 737 hit the ground. Rescue services arrived at the crash site almost immediately, but from the aircraft is almost nothing left. A pile of debris 38 ton passenger plane was buried in blackened from the fire impact craters.
Eyewitness: The plane did not slide and bouncing like a normal landing. He just hit his nose on the ground. That's all.
No one survived. All 20 5 passengers and crew members died from hitting the ground. Colorado Springs was the site of one of the most mysterious air disasters in history. Before nightfall arrived at the crash site investigators from the National Transportation Safety Committee (NTSB). They had a very difficult investigation, because of the aircraft is almost nothing left.
Investigator: Police cordoned off the area. One of the doctors gave me a cup of tea. We were all shocked by what he saw.
The key to the fate of Flight 585 lay shattered in a deep hole. The fuselage of a stroke formed accordion. Other parts of the aircraft were scattered around. Much damage has been done by the fire. Everything happened in a relatively small area and many of the details were burned. Similarly, it was clear that before the collision with the ground, the aircraft was intact. Bang in the air was not. Investigators have tried as best they could, but they did not know that their investigation will be the longest in the history of aviation.
The turbine engine, a hydraulic pressure gauge, voice recorder in the cockpit were gently removed from the accident scene, photographed and sent to the laboratory for analysis. First, investigators have begun to study the "black boxes" of the aircraft. 70% of all aircraft accidents occur because of errors of pilots and investigators want to find out what the crew was doing before the accident.
Investigator: I immediately realized that this crew was one of the most exciting, with whom I had to deal with. By appointment only create a sense of a great crew, rarely makes a mistake. I thought it wiser to seek the cause of the crash in the mechanics of the aircraft.
The more experts examined flight 585, the greater the suspicion falls on some mechanical failure. Researchers suspect a malfunction steering control, which is located at the end of the tail of the aircraft.
Investigator: We focused on what could cause a reversal of the aircraft.
The study makes it very difficult rudder damage. Fortunately, he survived the control unit. This unit is used constantly in flight. It performs functions similar to the power steering in the car. When the driver presses the pedal, the direction of the track is supplied to the control unit hydraulic fluid. It makes movement in the pilot pressure, which is necessary for the movement of the rudder Boeing 737. The heart valve is a control unit with two hydraulic actuators. It takes the form of cans of soda. It has two movable mechanism, which slide past one another, directing the flow of pressurized hydraulic fluid which operates the wheel.
Expert: This valve is very unique. In essence, this two valves in one. He has a complex structure.
When the technician opened the control unit, he found shards of metal floating in the hydraulic fluid. This was an alarming discovery. These particles can cause jamming of the valve. In this case, control the rudder would have been impossible. Still, experts do not rush to conclusions.
Investigator: The aircraft crashed and burned. It was severely damaged control devices that we have tested. The badly damaged item, the harder we were to conclude that it is working.
The control unit is sent to the laboratory of the manufacturer. There is version of interference due to the strange pieces of metal had been rejected. Investigators explained that the filter does not allow them to sensitive valve that directs the liquid and drives the wheel. Investigators could no longer find anything that would explain the strange movement of the rudder.
Investigator: We have had no clear information as to say that the crash was to blame for the faulty control unit.
The investigation was stalled. But there was another suspect - bad weather conditions. Experts meteorologists were trying to establish whether the wind factor that contributed to the accident. They listened to eyewitness testimony that on the day of the crash in the mountains there was a strange weather. At a time when the flight landed 585, the car of one man almost blown off the road by a strong gust of wind. But over time it became clear that the downdrafts of air could not bring down the plane and put it into a tailspin.
21 month has passed since the start of the investigation. The investigators examined all the evidence available to them, but are left with nothing. Only the fourth time in its history, NTSB issued a report before reaching conclusions. The reason for the crash of Flight 585 has not been established.
After 2 years after the publication of the report, there was another accident. On a clear calm day 427 American flight was approaching Pittsburgh. Captain Peter Germano and the second pilot Chuck Emmett were preparing for landing. Approaching the airport, the pilots watched on another flight, which flew in 10 kilometers above them. No signs of trouble. However, after going through a turbulent zone formed after the other aircraft, Boeing 737 suddenly and dangerously began to wrap the left. None of the pilots' actions did not help. He also went into a tailspin, crashed into the ground. While rescuers arrived quickly, no hope for 132 passengers was not.
When the crash came experts from the NTSB, they realized that the search otgadok will be long and exhausting. Soon, thanks to witnesses and data from the "black boxes", investigators have begun to realize that there were striking similarities between the case to the board and flight 427 585. In essence, they are mirror images of each other. When landing flight 585 wrapped right, and "US Air»427 - left. Both crews were caught by surprise, and after a few seconds both aircraft dived into the ground.
Investigators: We all know about the accident in Colorado Springs. We tried not to get hung up, and re-examine the situation.
Job investigators continued and growing list of similar items. In 427 flight engines are also working properly. But there was one major difference. When the flight was approaching Pittsburgh 427 was completely calm.
Judge: After examining the flight data recorder, it became clear that the evening was quite calm. There was no turbulence. Pilots were calm and spoke about the landing.
Just as in the case of flight 585, investigators have focused on the mechanical causes of the crash. Almost immediately, they made an encouraging discovery. Miraculously most of the plane's tail and rudder survived. Hydraulic equipment in the tail as well preserved. These details are immediately sent for examination, because the pressure on the NTSB from the public is growing. In both accidents, the plane fell Boeing 737. In this connection, a question was raised about their safety.
Investigator: As the chief investigator, I have never allowed the thought that this investigation remains unresolved. We went ahead and tried until we had to learn.
Investigators studied all versions, but the main suspect remained gidroventil - part of the unit control of the aircraft. As with the last time the experts found that the hydraulic fluid are metal particles. However, research has shown that they do not affect the performance of the system.
Expert: This unit has passed all performance tests. There was no indication of his failure. He worked on the set parameters, as it should.
Investigators returned to the study of the actions of the pilots. They knew that the rudder is fully turned in one direction. Also, investigators found that the co-pilot, who at the time of the accident was piloting the plane, in fact, strongly pressed the pedal of the rudder and hold it. It was very unusual.
Investigator: I thought about it, because I'm a pilot myself. It was not like a rational behavior.
Also, the data recorder of flight data showed that problems in flight 427 began when passing through the passing air flow. Registrar gave even the dull sound of hitting turbulence when flying flight 427 the zone. These data showed that there was something that caught drivers by surprise. They responded very quickly, but it turned out that nothing worked.
It has been almost 2 years since the disaster, and the investigation stalled. The fall of both aircraft were strikingly similar, but the investigators did not know the reason.
Investigator: We started to give up. Months began to grow in the years to come. Boeing 737 - excellent aircraft. We can not find a flaw in it. It does not go out of our heads.
9 1996 June last year, there was a long-awaited clearance. Another Boeing 737 landing at Richmond (Virginia). Suddenly, the plane began spinning to the right.
Captain: We realized that we had some problems with the rudder. I turned the control knob in the opposite direction and push the pedal, but it did not budge.
For more than 30 seconds the aircraft was flying dangerously careening to the right. The pilots did everything possible to the aircraft is not overturned. Then, just as suddenly, a mysterious force that kept the plane let him, returned to the horizontal position of the wings. No sooner had the pilots and passengers to recover the plane again wrapped to the side. 30 seconds Boeing 737 lived his life. Then it leveled off.
Captain: After the second time I looked at the co-pilot and said, 'Declare a state of emergency. Tell the dispatcher that we have a problem. "
Fortunately, a third inversion has occurred and the aircraft was able to land safely.
Captain: When I zarulivaet plane, then felt my legs shaking. I took a speaker to explain to the passengers what had happened. But I realized that he knew nothing. I just could not find the words.
The next day the team arrived in Richmond investigators. Finally, they had access to Boeing 737 defective rudder, which survived. Also, the crew survived, and they could tell a lot. It immediately became clear that the incident with the board 517 very similar to the two previous cases. The pilots told investigators that the foot pedal steering devoured, and they could not move it. The control unit is removed, examined and tested again and again. To everyone's dismay, he functioned perfectly. Even with a plane and the living pilots, investigators were unable to solve the case.
Soon, the experts decided to press harder on what they already investigated. They were subjected to thermal shock controller. The cold block filed overheated hydraulic fluid.
Expert: We stood and watched the blocks move the steering wheel right and left. Suddenly he stopped. It just stuck. Completely ceased to function.
Investigators experimentally proved that the valve is controlled rudder could get stuck. It was an ominous discovery, because Boeing 737 was the most popular passenger aircraft. However, they waited another discovery.
Investigator: The most important discovery happened when a mechanic Boeing, studying the results of the test data set, which indicated that the gate reverses direction.
It became clear that the valve can not only stuck, but also work in the opposite direction. This meant that every time trying to correct the inversion, the pilot only aggravates the situation. Drivers faced a very precarious situation and did not understand what was happening.
After investigations were made extensive changes to aircraft, to increase the safety of Boeing 737 and the aviation industry as a whole. They also developed new training protocols to teach pilots to react in case of abnormal situations in flight. Dual hydraulic valve has been redesigned to eliminate the possibility of malfunctions. But Boeing has spent hundreds of millions of dollars to replace valves in thousands of aircraft worldwide. After the replacement of such incidents do not happen.
Investigators took 10 years to solve this complicated case.
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