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Subject:  Re: Boeing Engineering Date:  3/18/2019  1:59 AM
Author:  steve203 Number:  555112 of 595111

The fact that there was a AoA vane option package indicates that someone at Boeing knew that this was a problem. The old Boeing would have over-engineered it and just added the redundant systems.

Only tangentially related, but another incident caused by cheap and dirty engineering: the DC-10 that lost an engine and crashed in Chicago decades ago. I read an article comparing the engineering of the DC-10 to the L-1011. The problem with the American Airlines DC-10 started with an incorrect maintenance procedure that damaged the engine mount. That was the direct cause of the engine falling off. As the engine was producing a lot of thrust when it separated, it rolled over the top of the wing, which exposed Douglas' cheap and dirty engineering.

The DC-10 had all three hydraulic systems running close together in the leading edge of the wing. When the engine rolled over the top of the wing, it damaged all three hydraulic systems. The L-1011 had the hydraulic systems installed in different areas of the wing so localized damage would not take out all the systems.

The leading edge slats of the DC-10 wings are held open by hydraulic pressure. When all of the hydraulic systems were damaged, the loss of pressure allowed the slat on that wing to close, causing that wing to stall. On the L-1011, the leading edge slats latch into the open position, and require positive hydraulic pressure to unlatch so they can retract.

Bottom line, if it had been an L-1011 that dropped an engine due to AA's poor maintenance procedure, it probably would not have lost all the hydraulic systems and, even if it did loose all hydraulics, the slat would not have closed and the wing would not have stalled. It might have made a difference.

Watched a piece on TV years ago about an old 737 that crashed in the Central American jungle. The plane was flying at night, over uninhabited jungle so very difficult to eyeball up and down, so the crew was dependent on their instruments.

Flight data recorder showed the plane making a series of sharp banking maneuvers, at an impossibly high rate, in other words, according to the data, the plane would go from a 45 degree right bank to a 60 degree left bank in a second.

That model 73 had 3 artificial horizon displays, and 3 gyros. One display in front of the pilot, one in front of the copilot and a third one off to the side. Normal use is for each display to be driven by it's own gyro. If a discrepancy is noted between the two main displays, they would be compared to the third to determine which display was wrong. Once the defective unit is identified, a selector switch was provided to switch both of the displays to the gyro that was working correctly.

Examining the wreckage, it was found the pilot had the gyro selector switch set, wrongly, so both main displays were running off one gyro, and there was a lose wire in the wire harness for that gyro. The wire would make contact for a moment and show the plane in a bank. The pilot would make adjustments to correct the bank, but the wire would break contact, so the pilot couldn't tell when the plane rolled past level into opposite bank. Then the wire would make contact for a moment, showing the bank in the opposite direction, which the pilot would again try to correct. Because the selector switch was set wrong, both of the main displays were showing the same information to the pilots, so they never thought to look at the third display, which was working perfectly. The pilots soon lost control of the plane and it augered in.

Personally, I find it stunning that Boeing would design any flight control system with no redundancy. I'm sure making a critical flight control system with no backup was cheaper, and that is what matters in our beancounter driven culture.

The U.S. Department of Transportation is investigating whether there were lapses in the Federal Aviation Administration’s approval of Boeing planes involved in two recent fatal crashes, The Wall Street Journal reported on Sunday.

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