Police helicopter crashes onto Glasgow pub

[AnFI]

FMEA and CA

Henry - thank you for that educational point.

I'd be fascinated to see the maths and figures used for a real life FMEA. It would be interesting to see how the various factors are determined and whether wider implications are taken into account.

For example when mitigating engine failure risk (by using two engines) are the consequent additional risks factored in? (like: pilot closing the wrong throttle(happens), critical components having less margin, worse autorotation performance, more complex gearbox (malfuntions), reduced payload/utility, fuel system complications (eg the A109 in Wales)). Reliability of FMEA work? - is that factored in?

What severity is assosciated with ditching (very servere or low risk?) - when a twin flys over a 'safe assured landing' surface are the additional risks consequent to twins factored? Is the ratio of time exposed to time with 'safe landing assured' factored?

I presume the answers to most of those questions is yes - but it would still be fascinating to analyse a real example.

Helicopters are inherently Simplex with many neccessarily Single Point Failure Critical Components - I like the fact that those Simplex components appear impirically to be very reliable, whereas many of the Duplex components do not seem to be (I suppose the logic is that they don't need to be, theoretically?).


But you cannot disagree complexity provides many more opportunities to fail to spot the obscure consequences - the "Unknown Unkowns"


I agree FMEA should provide a framework for answering the complex addition of systems - IF the INPUT DATA and ASSUMPTIONS are correct. ("garbage in garbage out" - right?)


Seems, for the North Sea, the maths is dubious (on first inspection) wrt Ditching. If the risk of ditching is severe enough to justify 2 engines, and this risk is mitigated by 2 engines then why waste payload on floats? If floats are neccesary to mitigate the (frequent) need to ditch and they are effective (which they appear to pretty good) then going to extreme capacity reducing measures (2 engines) to avoid ditching can't be worth it?
Maybe, making 'all-weather water landing' risk-free, could help straighten out the maths?