Originally Posted by
tdracer
Also demonstrably false. MCAS met current certification standards - but only because of some very bad assumptions regarding pilot reactions and training. MCAS failure was classified as "MAJOR" (classifications are MINOR, MAJOR, HAZARDOUS, and CATASTROPHIC). MAJOR failures are allowed to occur at ~10-5/hr (for example, 'routine' engine failures are considered MAJOR) - which basically means 'increased crew workload', and redundancy is not required. The regulations regarding such faults haven't materially changed in decades.
In 20-20 hindsight, MCAS should have been classified as at least HAZARDOUS (and probably CATASTROPHIC) - which means probability of occurrence of 10-7/hr (or 10-9 for catastrophic) and require redundancy.
The problem wasn't the cert rules, it was the interpretation of the seriousness of the fault (which, to some extent, was hidden from the FAA).
For the benefit of others, Unicode includes code points for superscripted numerals and 'plus' and 'minus' signs.
10⁺⁻¹²³⁴⁵⁶⁷⁸⁹⁰
So the maximum failure rates can be rendered as:
MAJOR: ~10⁻⁵
HAZARDOUS: ~10⁻⁷
CATASTROPHIC: ~10⁻⁹
The relevant code points are
Superscripted 'plus' sign: U+207A
Superscript 'minus' sign: U+207B
Superscript Left Parenthesis: U+207D ⁽
Superscript Right Parenthesis: U+207E ⁾
Superscript Numeral One: U+00B9
Superscript Numeral Two: U+00B2
Superscript Numeral Three: U+00B3
Superscript Numeral Four: U+2074
Superscript Numeral Five: U+2075
Superscript Numeral Six: U+2076
Superscript Numeral Seven: U+2077
Superscript Numeral Eight: U+2078
Superscript Numeral Nine: U+2079
Superscript Numeral Zero: U+2070
Copying and pasting from this post should work.