| 波音737存在根本設計問題，無法用軟件修正 |
| 送交者: 香椿樹1 2019年06月03日02:46:24 於 [軍事天地] 發送悄悄話 |
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紐約時報的這篇文章看上去氣勢洶洶實際上是在替波音公司洗地。 當然媒體扯謊不會讓人抓到把柄，總是會把真相藏在假象里， 換句話說就是欺負讀者腦殘，誰讓你沒讀懂。 報道開頭就說波音公司軟件設計草率地把多個傳感器喚醒的控制系統改成只用一個傳感器，是愚蠢行為，給人的印象是只要把多個傳感器改回來就萬事大吉了。 一個愚蠢的決定，草率的決定修改起來似乎很容易。 但是， 真相藏在細節里。 MCAS出現的原因就是因為換了大發動機之後的波音737在高速飛行的時候不再穩定。 當時的工程師要求修改機翼和氣動外形，波音風洞實驗覺得做不到， 所以決定用軟件打補丁。 波音公司從2012年折騰到2016年，再次試飛的時候發現飛機低速的時候也不穩定， 波音公司這次已經不再考慮修改氣動外形和控制系統了， 波音公司的決定是修改軟件補丁MCAS。 而修改的方法簡直就是草菅人命， 拆掉多傳感器的限制， 只用一個傳感器， 並且把控制力度增加了5倍！！ 換句話說，波音只用一個傳感器不是“愚蠢”的決定， 而是“無奈”的決定， 更是一個“黑心”的決定。 話句話說， 波音737絕對不是修改軟件補丁就變得安全， 波音需要得是重新設計飛機的氣動外形！ —————————— MCAS Is BornIn 2012, the chief test pilot for the Max had a problem. During the early development of the 737 Max, the pilot, Ray Craig, a silver-haired retired Navy airman, was trying out high-speed situations on a flight simulator, like maneuvers to avoid an obstacle or to escape a powerful vortex from another plane. While such moves might never be necessary for the pilot of a passenger plane, the F.A.A. requires that a jet handle well in those situations. But the plane wasn’t flying smoothly, partly because of the Max’s bigger engines. To fix the issue, Boeing decided to use a piece of software. The system was meant to work in the background, so pilots effectively wouldn’t know it was there. Mr.
Craig, who had been with Boeing since 1988, didn’t like it, according to
one person involved in the testing. An old-school pilot, he eschewed
systems that take control from pilots and would have preferred an
aerodynamic fix such as vortex generators, thin fins on the wings. But
engineers who tested the Max design in a wind tunnel weren’t convinced
they would work, the person said. 【補丁飛機高速時出現飛行不穩定正常情況下需要修改飛機的控制系統和外形， 小修改不管用，才相到用軟件強行修公正】 Mr. Craig relented. Such high-speed situations were so rare that he figured the software would never actually kick in. To ensure it didn’t misfire, engineers initially designed MCAS to trigger when the plane exceeded at least two separate thresholds, according to three people who worked on the 737 Max. One involved the plane’s angle to the wind, and the other involved so-called G-force, or the force on the plane that typically comes from accelerating. A
Boeing 737-800 flight simulator. When Mr. Craig simulated high-speed
maneuvers for the Max, it didn’t fly smoothly, so Boeing settled on MCAS
for a fix.CreditAviation-Images.com, via Getty Images The Max would need to hit an exceedingly high G-force that passenger planes would probably never experience. For the jet’s angle, the system took data from the angle-of-attack sensor. The sensor, several inches long, is essentially a small wind vane affixed to the jet’s fuselage. Adding More PowerOn a rainy day in late January 2016, thousands of Boeing employees gathered at a runway next to the 737 factory in Renton, Wash. They cheered as the first Max, nicknamed the Spirit of Renton, lifted off for its maiden test flight. “The flight was a success,” Ed Wilson, the new chief test pilot for the Max, said in a news release at the time. Mr. Wilson, who had tested Boeing fighter jets, had replaced Mr. Craig the previous year. “The 737 Max just felt right in flight, giving us complete confidence that this airplane will meet our customers’ expectations,” he said. But
a few weeks later, Mr. Wilson and his co-pilot began noticing that
something was off, according to a person with direct knowledge of the
flights. The Max wasn’t handling well when nearing stalls at low speeds. 【補丁飛機低速時也不穩定， 再次證明波音737的設計有問題， 整個機體和氣動外形有問題， 高速和低速時都不穩定。 高速不穩定還好說， 不飛高速就算了， 低速怎麼辦？】 In a meeting at Boeing Field in Seattle, Mr. Wilson told engineers that the issue would need to be fixed. He and his co-pilot proposed MCAS, the person said. The change didn’t elicit much debate in the group, which included just a handful of people. It was considered “a run-of-the-mill adjustment,” according to the person. Instead, the group mostly discussed the logistics of how MCAS would be used in the new scenarios. “I don’t recall ever having any real debates over whether it was a good idea or not,” the person said. The change proved pivotal. Expanding the use of MCAS to lower-speed situations required removing the G-force threshold. MCAS now needed to work at low speeds so G-force didn’t apply. The change meant that a single angle-of-attack sensor was the lone guard against a misfire. Although modern 737 jets have two angle-of-attack sensors, the final version of MCAS took data from just one. Ed Wilson, right, with his co-pilot, Craig Bomben, after the first Max test flight in 2016.CreditElaine Thompson/Associated Press Using
MCAS at lower speeds also required increasing the power of the system.
When a plane is flying slowly, flight controls are less sensitive, and
far more movement is needed to steer. Think of turning a car’s steering
wheel at 20 miles an hour versus 70. 【為了趕進度真正的草菅人命來了】 The original version of MCAS could move the stabilizer — the part of the tail that controls the vertical direction of the jet — a maximum of about 0.6 degrees in about 10 seconds. The new version could move the stabilizer up to 2.5 degrees in 10 seconds. Test pilots aren’t responsible for dealing with the ramifications of such changes. Their job is to ensure the plane handles smoothly. Other colleagues are responsible for making the changes, and still others for assessing their impact on safety. Boeing declined to say whether the changes had prompted a new internal safety analysis. |
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