Central Air Safety An Investigation Gone Right

航空发表于 2010-8-16 00:18:02

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航空发表于 2010-8-16 00:18:22

April 2000 – US AIRWAVES 9 John Cox (PHL) Vice Chairman, ALPA Executive Air Safety Committee Central Air Safety “ . . . all operators of the Airbus 318/319/320/321 will be told what we learned and how to avoid or contend with the problems that one of our flight crews experienced.” An Investigation Gone Right All too often, the reports we hear are about the story of an incident and an investigation gone wrong. Occasionally, there is a story about an incident where the investigation goes the way it should. In January, an event occurred in Charlotte that started an investigation where cooperation, diligence, and hard work came together to produce a better understanding about the inter-workings of our Airbus 319/320s. As a result, all operators of the Airbus 318/319/320/321 will be told what we learned and how to avoid or contend with the problems that one of our flight crews experienced. In mid-January, a low-pressure system reduced the visibility in Charlotte to less than one mile with snow falling. As the snow accumulated, runway plowing caused a single runway to be used. Air traffic control vectored one of our A319s for the ILS approach to Runway 36R. This A319 was one of a large number of inbound aircraft. Because there was only one runway in use, when the Airbus received clearance for the ILS approach, they were over 25 miles from the runway threshold. In level flight, flying 160 knots at 3600 feet, the Captain armed the approach mode and armed the second autopilot in accordance with procedure. Soon afterwards, they approached the localizer and the Airbus turned to intercept it. As they tracked the localizer, all appeared normal. As they closed to 22 miles from the runway, the airplane pitched up abruptly. The crew realized that the airspeed had deteriorated below 135 knots. Quickly, the Captain disengaged the autopilot and autothrust systems. As expected, the A319 responded normally to the manual inputs made by the Captain. They descended back to 3,600 feet and accelerated back to 160 knots. What just happened? Why did it occur? Would it happen again? After reengaging the autopilot and autothrust, the airplane flew a normal coupled approach and auto-landing. Arriving at the gate the Captain entered the pitch event into the maintenance logbook. As one would expect, the outbound flight canceled. First indications were that an angle of attack sensor provided incorrect information, and that caused the pitch up. Later, upon further analysis, this did not prove to be correct. The crew contacted the Company and the ALPA Central Air Safety Committee. After some initial conversations with the Fleet Manager, Captain Bob Skinner, we realized that there were several unanswered questions and very similar levels of concern. This was a significant inflight event and there was not a good explanation of the cause. We decided that this required much more investigation. A call to our Airbus avionicsengineering experts in Tampa verified the de10 US AIRWAVES – April 2000 Central Air Safety tails of the event. As we studied the flight data recorder, several anomalies appeared. We began to ask specific questions of Airbus to help us understand what happened. A conference call followed with the Airbus engineers at the factory in Toulouse. They explained what they saw in the flight data recorder data. At the conclusion of the call, there were still many unanswered questions. We discussed using the engineering simulator to recreate the event. Airbus concurred, and they set up the time and the needed experts for the tests. After a short debate, we decided that it would be prudent for a couple of us to attend the tests. Just before leaving for Toulouse, we were able to contact ALPA Safety representatives at other airlines that operate the Airbus and ask if they were aware of any similar events. Surprisingly, the answer came back that some of the maintenance engineers were aware, but the pilots were not. Two days later, we arrived in Toulouse and met with the Airbus engineers in person. Over the next two days, we agreed on the conditions that we would use in the simulator. Additionally, we agreed that the participants in a postsimulator meeting would decide on future action. The stage was set to not only understand the event but to take newly learned information and distribute it to other operators. Early in the morning, we met at the engineering simulator. Along with the engineers was a pilot from the Flight Testing Department. The technicians loaded the data into the simulator, and we began our tests. As expected, the simulator followed the flight path of the event airplane. It began to pitch up 22 miles from the runway threshold just as the event airplane had. The flight data recorder had recorded a glide slope signal prior to the event. As the A319 tracked the localizer, all the conditions were armed for a glide slope intercept. This would have been normal except for the large scallop in the glide slope signal that occurred causing the flight management guidance computer to believe that the aircraft was approaching the glide slope. It then switched into glide slope ‘*’ (capture) mode. The scallop was very quick so that the computer believed it was below a valid glide slope and began to climb. This explained the pitch-up and the quick rate of the pitch-up because glide slope * can command up to three times the normal pitch rate to capture the glide slope. In addition, we then understood the airspeed decay. It is normal for the Airbus to “ The event was the result of the airplane performing exactly as designed. Pilot intervention was appropriate and necessary. ” trade airspeed for altitude in an effort to capture the glide slope. We also learned that the airplane remains within its protected flight envelope. There is no danger of a stall. (You cannot stall an Airbus when it is in normal law.) The event was the result of the airplane performing exactly as designed. Pilot intervention was appropriate and necessary. This condition was not unique to the Airbus: Other airplanes have tracked false localizers or invalid glide slopes. What was significant was the expectation of the flight crew did not match the flight path of the airplane. The pilots did not expect the airplane to pitch-up, and they did not expect the airspeed to decay appreciably. After understanding what happened and why it happened, we agreed that this information should be sent to all Airbus pilots. Airbus agreed to send a notice to all operators about false glide slope interceptions. US Airways created a Flight Information Letter for all Airbus pilots. This way the information about the consequences of a false glide slope capture would be known and the appropriate pilot intervention could occur earlier. Airbus agreed to evaluate the design of the logic for glide slope capture to reduce the possibility of attempting to capture a false signal. There are improvements that have been made to the A330/340 and that logic improvement may be usable in the A320 family. While some follow-up work remains, the majority of the investigation is complete. In less than one month we learned of an event, analyzed it, met with the Company about it, met with Airbus about it, agreed on a plan to improve pilot information worldwide about it, and helped draft the flight information letter for US Airways Airbus pilots, which then was distributed promptly. Sometimes an investigation goes right. This one was the first time that we had seen a noteworthy issue occur on the Airbus since we began service in November 1999. The Company agreed with our assessment and joined us in the investigation. Airbus agreed with us and joined us. Cooperation led to a quick resolution. When it comes to safety and cooperation, diligence and hard work is in everyone’s interest. April 2000 – US AIRWAVES 11 Central Air Safety In September 1989, one of our B-737-400s performed a rejected takeoff in New York. It resulted in an accident. I worked as the ALPA representative on the powerplant group. After the field phase was complete, Captain Bill Sorbie, then-Central Air Safety Committee Chairman, asked me to write an article for US AIRWAVES about the investigation. That first article began my regular contribution to US AIRWAVES. It is now over 10 years later and this is my last regular article. In early March, ALPA’s Steering and Oversight Committee selected me to the position of Vice Chairman of ALPA’s Executive Air Safety Committee. This is the number two position in the safety structure for ALPA. This demanding job deals with the safety concerns of 52 airlines across two countries. There is considerable diversity in the flight operations of these 52 airlines. They include small freight operations in Canada to United Air Lines B-747s. It is impossible do justice to this new job while remaining as the AAA Chairman of the Central Air Safety Committee. For that reason, I have resigned as Chairman of your Central Air Safety Committee. The decision to take this new position was not an easy one. It has been my privilege to work with an outstanding group of professionals while I was part of ALPA’s Safety Committee at US Airways. The work was hard and the hours long, but we made a difference. Safety at our airline has improved. This advancement is due, in part, to the work of many of ALPA’s Central Air Safety Committee members. We are industry leaders in effective cooperation between the Association, the Company, and the FAA. Over the years, many other airlines have visited us to see how we operate, how we are organized, and how we take issues that are of concern to our line pilots and improve the safety of our flight operation. We led the industry with our Altitude Awareness Program. That is now expanded into the Aviation Safety Action Partnership (ASAP), which will be the standard of the airline industry soon. We led the way in Flight Operation Quality Assurance (FOQA). Again, that will be a standard soon. We are much more standardized in our flight operations than we were 10 years ago. The list of our accomplishments is far too long to enumerate here. Nevertheless, I remember them all. It has been a privilege to be a part of this. I have been glad to help our pilots when there is a problem, incident or accident. We have worked effectively with the NTSB and FAA to ensure that our pilots received fair, unbiased investigations. The Central Air Safety Committee is working as well as it ever has. The members are involved in large numbers of projects. This commitment will grow with our airline. International operations are growing and so is the safety responsibility to the crews that fly to foreign countries. This is an area of focus for this year. The effectiveness of the committee in all of these projects will continue. While my office will be in the ALPA building in Herndon, Virginia, I will continue to be available if needed. The relationship between the ALPA Executive Air Safety Committee and the US Airways Central Air Safety Committee is very close. I expect that this will continue and expand in the future. Captain Terry McVenes has been appointed as the interim Chairman of the Central Air Safety Committee. Terry’s proven leadership will serve to make the transition seamless. His dedication is well established. Ladies and gentlemen, thank you for the opportunity of representing you in safety matters for the last 14 years. I will continue to do the best I can to improve safety in the aviation industry for 51,000 airline pilots. I sincerely appreciate the comments that many of you have made about my US AIRWAVES articles. I never claimed to be a writer. After 10 years of writing articles regularly, I have learned more about communication than I ever expected to know. I look forward to seeing you on the line. Hopefully, I will get to fly a little more in this new position. A Change “ Safety at our airline has improved. This advancement is due, in part, to the work of many of ALPA’s Central Air Safety Committee members. We are industry leaders in effective cooperation between the Association, the Company, and the FAA. ”

涟漪雨 发表于 2010-11-11 10:13:38

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Central Air Safety An Investigation Gone Right