Avionic design, flight control systems

Answered Oct 15

Three answers so far all adhering to the Boeing bullshit explanation of “it’s third world pilots”.

Precisely three incidents of angle-of-attack vane failure have occurred on the MAX. The first Lion Air incident was solved by three pilots working together, since there was one flying as a passenger in the jump seat. He noticed the trim wheels running in an odd fashion and alerted the pilot in control, who recovered the trim situation, but still elected to complete the flight, with all the warnings going and the stick shaker on the whole time. They didn’t know what had gone wrong, and wrote it up as “STS running in reverse”. Lion Air maintenance records show that the vane was changed, and yet on the next flight the same problem showed up, eventually taking the aircraft straight down nose-first into the sea, killing all on board. The Ethiopian Airlines incident was started by the vane completely failing just after takeoff – it is theorised that it was a bird strike that took the vane itself away, leaving the balance weight to take the reading to a full nose-up end stop. The pilots had received the message from Boeing revealing the MCAS and its vulnerability, but saying it was just like a runaway trim situation. It wasn’t, never was, and the aircraft ended up going straight down nose-first into the desert, killing all on board.

It’s the AoA vane failure that triggered the weakness in the badly-designed, criminally inadequately tested, MCAS that killed two full planeloads of passengers and crew. It was a failure that should have been dealt with by the system, but instead had catastrophic consequences, which shows that the MCAS is not fit for purpose and the MAX should never have been certified.

The JATR report is newly-published, and contains all the information you need.



how come there were no accidents within the US or Europe?

Luck, no AoA vanes failed on any American or European low-cost airline’s MAX, and aviation authorities outside the US were quick to ground it after the second accident.

The FAA has a lot of explaining to do, still. Boeing is still smiling, saying as little as possible and keeping their share price high. But there’s chickens coming home to roost.

Lion Air is not free of criticism, as the accident aircraft should not have flown again until the nature of the problem was discovered – but their maintenance crews followed Boeing’s procedures to the letter. Fault reporting and resolution should be overhauled at the very least.

Ethiopian Airlines’s crew were doomed by Boeing’s inadequate response to the Lion Air incident, recommending only that the crew should follow the known Stab trim runaway procedure, which they did, but the MCAS had added too much nose-down trim for them to recover by that process. Yes, I know they didn’t reduce power, but if you’re trying to recover from a nose-down situation in a jet with underslung engines, reducing power will make it worse.

Kazan- Kazan National Research Technical University Казанский национальный исследовательский технический университет имени А. Н. Туполева he graduated in Economics in 1982

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