Originally Posted by
JimL
Are you trolling me AnFI?
The fact that tail rotors were not meeting their expected reliability led to CAA action resulting in a CAP with recommendations to address the issue. It does not change the mathematics but when reliability does not reach expected levels, it triggers a review process.
Hughes500: Perhaps that question should be addressed to AnFI, he might have relevant experience in that field.
Jim
Hi JimL
No I am definately not trolling you. I only want a valid discussion. A "well balanced debate".
Has the CAA study you refer to actually led to an improvement in tail rotor reliability of a factor of 50000 !?
How have they acheived that? Seems a little unrealistic. Especially in light of Leicester. A tail rotor is an assembly of parts each made with the target 10^-9 in mind, how many critical components are there in a TR assembly?
You can't make a TR with a reliability rate of 10^-9, these are not realistic numbers. A simple TR is a more inherently reliable assembly.
You say it does not change the maths, but if you fix the cause of 1% of fatal accidents by increasing complexity and that results in other accidents more often and of a more catestrophic nature, then
the maths are changed. You can't take the upside without accounting for the downside.
You have an odd idea of catestrophic.
This is catestrophic:
so is this
and this
and this !
and this !
These on the other hand are MAJOR/inconvenient ? :
That's not to say 3rd party fatal consequences are impossible from engine failure in urban areas, there's a recent exception
in Tampa (and Sao Paulo), very unusual and unlucky, even in a gentle landing like this it can go wrong, hitting wires / poles can do that.
Any landing poorly executed
can go wrong.
Wait for the report but it looks like it'll be an answer to Hughes500 question, reports suggest it was known in advance that the engine was sick.
BUT nothing like as bad as this would be in an urban area:
Is it really justified to make the world perform to the engine-centric North Sea 'special case' - can you justify the safety yeild?
How much safer does 2 engines make it? Some/none/less ? Sometimes in specific scenarios?
What are the numbers?
99% of fatal accidents are from causes other than engines.
Even the slightest increase in the frequency of the 99% completely negates any benefit.
I don't expect serious answers because I don't think there are any serious answers to that.
If there are it would be great to hear them.