etudiant, re ‘…
evolution, old aircraft, new world’
This is central to the safety debate; and as identified by lomapaseo, ‘
As an industry we are left with "best practices" which remain unregulated (cost and time prohibited)’.
Historically safety intervention uses cost equivalence of fatalities vs action, placing a value on life when judging the cost-time tradeoff between modifying the aircraft or training the pilot.
The cost of modifying old aircraft might be disproportionately higher than newer models, also with larger fleets the cumulative cost could easily exceed training cost, which would benefit manufacturers - cost of modification (manufacturer pays) vs cost in training (operator pays).
The fallacy with training is the belief that its safety effect can be equated with modifying the aircraft, not so; ‘Training solutions are typically only assumed to be effective, not proven.’ *
Also, a cost-time evaluation must consider growing fleet size, future time in service, and thus greater exposure to the original risk. Which in turn requires more pilots to be trained, and many new pilots in following years - expensive, but hidden (forgotten) cost. How many aircraft / pilots since 737-500.
The industry's safety focus must change from past fatalities to future risk, particularly in an industry with a high level of safety. (Amalberti and Dekker argue that there will be little effective improvement above the overall 10^7 level).
In this 737 event, action based on fatalities could similarly misjudge safety tradeoff (older aircraft); and overlook the safety value in understanding preceding flights without fatalities. If action is warranted then perhaps dusting off the proposed mod; someone considered it to be of value at the time;- td
tdracer ‘
The real question remains - why didn't the crew notice?’
I disagree
, - why wasn't the proposed modification mandated. The safety thinking at that time needs to be understood. Also, why the industry apparently overlooked the findings of PSM+ICR, where the majority of issues in this discussion had been identified 20yrs ago. And irrespective of how many of the extensive training recommendations were accepted, why do we still continue to seek a training solution, which in failing to prevent this accident, implies that training has not been successful.
* PSM+ICR pages 67-68
https://www.faa.gov/aircraft/air_cer...ne_psm_icr.pdf
And for the inattentive: effective thrust monitoring requires comparing engine instruments (thrust parameter) not the input levers.