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Just as a sidenote, the article ends with: > That being said, the probable continued existence of unapproved parts on the market should not really be cause for

Just as a sidenote, the article ends with: > That being said, the probable continued existence of unapproved parts on the market should not really be cause for alarm to the flying public. [...] The fact is that Partnair flight 394 remains the only crash of a commercial airliner linked to unapproved parts, placing the issue rather far down the list of problems that cause the most crashes. It's worth a read, but the summary is that the problem is mostly under control and unlikely to cause a crash. > In general, this is because unapproved parts cause annoying breakdowns and increase maintenance costs, but don’t directly cause crashes, simply because there are very few individual parts on an aircraft which could cause a crash if they fail. Redundancy in aircraft design largely shields us from the consequences, with the primary exception being very old aircraft like LN-PAA which predate many modern airworthiness requirements. Even then, it took multiple unapproved parts in multiple locations, plus inadequate inspections and poor documentation, to actually bring down the plane.

kayfox 3y ago
Since that article was written in 2018, Lion Air Flight 610 crashed in part because of an unapproved replacement angle of attack sensor installed without proper testing. So there's at least one more crash associated with unapproved parts.
- felixg3 3y ago
  How is lion air 610 related to that? The issue was not the single unapproved part but a whole series of malicious business decisions and corporate misconduct by a internally corrupt airplane manufacturer.
- Prickle 3y ago
  Not really no. Lion Air 610, and the 23 other near miss incident reports all point to a fundamental design flaw in the Boeing 737 Max8 Primarily, that there is only one angle of attack sensor that feeds the MCAS system. There are two sensors, but the system just doesn't compare them. It just takes the result from one sensor and uses it regardless of errors. For comparison, Airbus A320 actually has a very similar system. But it is fed by 3 different angle of attack sensors. All 3 sensors are constantly compared against each other. I almost forgot! Below quotes are straight from Wikipedia MCAS page. > Boeing's own internal design guidelines related to the 737 MAX's development stated that the system should "not have any objectionable interaction with the piloting of the airplane" and "not interfere with dive recovery".[68] The operation of MCAS violated those.[69] > the specific failure modes that could lead to unintended MCAS activation (such as an erroneous high AOA input to the MCAS) were not simulated as part of these functional hazard assessment validation tests. As a result, additional flight deck effects (such as IAS DISAGREE and ALT DISAGREE alerts and stick shaker activation) resulting from the same underlying failure (for example, erroneous AOA) were not simulated and were not in the stabilizer trim safety assessment report reviewed by the NTSB."

kayfox 3y ago

Since that article was written in 2018, Lion Air Flight 610 crashed in part because of an unapproved replacement angle of attack sensor installed without proper testing. So there's at least one more crash associated with unapproved parts.

felixg3 3y ago
How is lion air 610 related to that? The issue was not the single unapproved part but a whole series of malicious business decisions and corporate misconduct by a internally corrupt airplane manufacturer.
Prickle 3y ago
Not really no. Lion Air 610, and the 23 other near miss incident reports all point to a fundamental design flaw in the Boeing 737 Max8 Primarily, that there is only one angle of attack sensor that feeds the MCAS system. There are two sensors, but the system just doesn't compare them. It just takes the result from one sensor and uses it regardless of errors. For comparison, Airbus A320 actually has a very similar system. But it is fed by 3 different angle of attack sensors. All 3 sensors are constantly compared against each other. I almost forgot! Below quotes are straight from Wikipedia MCAS page. > Boeing's own internal design guidelines related to the 737 MAX's development stated that the system should "not have any objectionable interaction with the piloting of the airplane" and "not interfere with dive recovery".[68] The operation of MCAS violated those.[69] > the specific failure modes that could lead to unintended MCAS activation (such as an erroneous high AOA input to the MCAS) were not simulated as part of these functional hazard assessment validation tests. As a result, additional flight deck effects (such as IAS DISAGREE and ALT DISAGREE alerts and stick shaker activation) resulting from the same underlying failure (for example, erroneous AOA) were not simulated and were not in the stabilizer trim safety assessment report reviewed by the NTSB."