DB
COST BENEFIT ANALYSIS: CBA
Yes - what you say is the B part, I agree!!! Not in dispute (mostly)
To make a valid decision you need to look at the C part: The COST
You cant just claim the B without the C. Can you? Do you not accept that there IS a cost?
Many are 'uninteded consequences', that cannot justly be ignored.
The Costs are many, some:
Economic activity stifled, jobs lost, utility hampered, ordinary people (taxpayers) priced out of utility of helicopters, super wealthy 'elites' only? Tried hiring/buying your own helicopter?
Fuel pressure: to be tight on fuel because you carry engine redundancy may not be safest.
Complexity of airframe, applies to systems and pilots, causes accidents that would not otherwise occur:
Leicester: as crab says a helicopter of AW139 size (due to engine redundancy) HAS to have a hydraulic Tail Rotor. It killed them.
Cultha: SIX (?) working fuel pumps and an experienced pilot can't get the 20+mins fuel remaining to the engines, because the system is complex and the pilot is confused, perhaps, because it is a twin prompting feeder tanks. 'Captain Murphy' will always come through.
AS332/H225: Gearbox's madly complex, breaks killing several helicopters full of people - FORTUNATELY not over urban areas, otherwise that COST would be very ovious.
Bigger energy impacts - imagine 15tons of helicopter in the Albert Hall on Proms night.
You cannot shut down the wrong engine in a single.
Critical components work harder: Any twin would have better margins for the same payload for many critical systems, (eg TR authority, etc etc etc).
Complexity has consequences !!!
If you don't asses the COST part of CBA, then you are clearly distorting the arguement.
I'd love to hear from JimL on this. ANY rationale? CBA? What's your 'A' part?
To exactly quote JimL:
"The argument that simplicity is safer than complexity is a given, only the consequence is in question"
I agree, DB - you don't?
What is the quantification of risk to 3rd parties on the ground ? ALoSP??? What is it?
We need to know because we must weigh the C against the B that you correctly identify.
We have to DO the 'A'. ABC : CBA !!
(ref 4 engines, yes ETOPS calculations include reduced risk of negative consequences of more engines (that can explode, and CAUSE the problem), this is similar to the exposure to more freewheel units, for example, EH101, Thruxton AS355)
[Crab - no argument with the Authorities, the Authorities have no view on this topic.
There are former employees, 'consulting', with a view to impose this on the rest of the world through ICAO.
They'll have consulting jobs for life, trying to explain to developing counties why they must take off upwards and backwards.
They are trying to move the goal posts: Hostile Areas WILL lead to Catastropic outcomes - really???
The current ICAO "land without undue hazard to persons and property on the ground" is being changed completely to become a Catastrophy requiring 10^-9. T'aint right, wake up world these rules are coming your way soon !!
They have not given their rationale.
They will undermine the credibility of the ICAO base line (and others), that has done so much good for the world.]
Bell, yes the stats are open to abuse, but one should try, feel free, go ahead, try and find neutral truth. Maybe twins do 4 times as many pax.hours, I don't know, i doubt it, but even then it doesn't seem like a good result does it? Worth the COSTs?