[SystemSafety] A different Historical Question

[Matthew Squair]

I think this might go all the way back to the ICAO 90 minute rule for twin
engine (might also be for 3/4) operations... Hope that helps.

On Thu, Mar 23, 2017 at 4:20 AM, SPRIGGS, John J <John.SPRIGGS at nats.co.uk>
wrote:

> Way back in the last millennium, someone did an analysis of aircraft
> accident data, selected out a set based on various criteria, such as
> ‘western built’ commercial air traffic in controlled airspace, etc., and
> came up with a figure for accidents per flight.
>
> On behalf of ECAC, someone applied an improvement factor, truncated the
> answer to two decimal places and declared a ‘safety target’ of better than
> 2.31x10^-8 accidents per flight.  At that time, it was conventional to
> assume an average flight is ninety minutes. This was applied to the result
> and rounded up to give a target of better than 1.55x10^-8 accidents per
> controlled flying hour.
>
> I used to have references for these things, but I have lost them (the ECAC
> targets are quoted in a document called ESARR4 which is still available
> despite being obsolete in the EU for over a decade). In particular I wanted
> a reference for the ninety minute flight convention.  This is because I
> have been shown a standard (not from the commercial air traffic domain)
> that takes the ECAC targets as the basis for arguing that the average
> length of a flight is 89.4 minutes, i.e. taking the truncated and rounded
> results as ‘truth’ …  I would like to challenge it with references.
>
>
>
>
>
> John
>
>
>
>
>
>
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-- 
*Matthew Squair*
BEng (Mech) MSysEng
MIEAust CPEng

Mob: +61 488770655
Email: MattSquair at gmail.com
Website: www.criticaluncertainties.com <http://criticaluncertainties.com/>
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