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Old 07-19-2017, 03:32 PM   #1
Tweety
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Default United 232

Interesting read, especially considering how close they were to pulling off a acceptable landing given they had no control on any axis.

http://www.popularmechanics.com/flig...-232-16755928/


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Old 07-19-2017, 10:19 PM   #2
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Creative software designers created software that could control a plane using only engine power, but in response to the regular pilot's controls... not by diddling the throttles. In a demo the software successfully landed a DC10. In essence the software implemented what the pilots did in United 232.

Authorities decided that the likelihood of another such emergency was low, and the SW was not put into service.


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Old 07-19-2017, 10:56 PM   #3
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Thousands of hours of routine followed by minutes of sheer terror. I flew a lot on business on many airlines flying less than exemplary examples and knew that there was some risk but nothing other than blown tires twice and one aborted takeoff happened, though I did miss a flight in Venezuela that crashed on landing in heavy rain. No one was killed but looking at the wreck when we arrived two hours later, it must have been terrifying for all on board as the 727 skidded across a muddy field and went into a grove of trees going backwards. Before the one described in that article, there was another DC-10 that had a massive decompression due to a baggage door blowing off east of Detroit, resulting in the cabin floor collapsing and cutting all the lines, wires and cables for the rear engine and surfaces. In that one the crew landed with no fatalities, if I recall right on a military base in Michigan. I'm sure GM knows more about it than I do.
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Old 07-20-2017, 03:26 AM   #4
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In these days of Mandatory Crew Resource Management Training UAL 232

is often the example of how to do it right.

Wrong was Air Florida 90.
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Old 08-15-2017, 08:41 PM   #5
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The accident started in the GE plant with the casting of the fan disc. At that time they used a double melt process to get the impurities to go the the bottom of the cylinder of metal. The cylinder was then sliced into 9 slices, the top 8 to make the fan discs and the bottom one with the impurities. After machining the fan disc they were inspected. One was found to have a flaw. It was removed from production and sent to the far end of the factory. Years later the defective disc was sliced open to see the flaw. None were found. A serial number discrepancy was found. One of the 8 dics from this melt was missing. There had been a serial number duplication. The "defective" disc s/n was xxx. They serial number on United 232 was the same xxx.
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Old 08-15-2017, 09:40 PM   #6
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Default United 232

The sad thing about how close they came to pulling off the landing was that on final they were both too fast and had too much sink rate. Since the under-wing engines were all they had to control attitude, they were in a difficult spot, since reducing power would have reduced airspeed, but would have caused the nose to drop, increasing sink rate. When they increased power to try to reduce the sink rate, one engine didn't spool up to full power so that wing dropped and they cartwheeled. Without flaps or horizontal stabilizer control, the only way they could have reduced both sink and speed would have been to get behind the power curve, then apply extra thrust. Maybe that's what they tried to do but were thwarted by the asymmetric engine response. Without hydraulics, would the yaw damper necessary to prevent Dutch roll still have been operating?
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Old 08-16-2017, 02:09 AM   #7
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The DC-10 yaw damper is nothing more than a mechanical computer that drives a servo that moves the rudder. It would require hydraulics to operate.

Eric
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Old 08-17-2017, 05:17 PM   #8
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Default United 232

So without hydraulics, as United 232 was, would the yaw damper be functional? Was that the cause of the multiple circling track?
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Old 08-17-2017, 07:49 PM   #9
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They had nothing, not even pitch trim which would have probably made all the difference.

Yaw damper is most effective at altitude and high speed anyway.
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Old 08-17-2017, 08:30 PM   #10
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The damage to the tail caused the aircraft to have a significant yawing moment so it made the aircraft even more unstable. They could only turn in one direction. The circles were because of this and the need to loose altitude...

Eric


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