JimL
The points are serious and answer your questions. Not
that complex.
(compared to fuel systems of A109, EC135, (S61? 10 fuel tanks?! (how often do you get a fueltank failure? About 10 times as often as if you had 1 I suppose?))) Perhaps you could give a thought to some of my questions there?
and you can see I suffer from being selectively mis-quoted
also... (which bit is inaccurate?)
Is it safer for urban overflight in Twins or Singles?
Given the nature of the catastrophic events that occur so often with heavy twins? see post #97
How do you calculate it? OR are you just taking the upside of less engine failure forced landings without the consequential (potentially greater) downsides?
Maybe try answering some of the points, are there answers? Do you have them?
Do you think it takes highly trained / experienced / checked / SoP'd multi crew to stand a chance of seeing the sliveringly thin
theoretical upside of engine redundancy? Or can all pilots and operations benefit?
Do you think the 'North Sea model' is really likely to work
'onshore', world wide?
Lots of reasons why it probably won't.
One of which is the disproportionate cost, which prices out most potential helicopter users in order to return an unspecified theoretical gain. Removing the utility of helicopters for a vast number of ordinary people.
Oil / State / EMS are exceptionally highly funded areas, not typical or proportionate to the depth of pockets of the typical civil helicopter user.
What is the COST / BENEFIT ANALYSIS ? Is there one?
Crab, (still v personal
my ego has nothing to do with it.)
369 has trim actuators for
cyclic loads. Tail rotors don't have a cyclic control, just a 'collective control', called yaw pedals. The 369 does not have trim motors to assist the collective, only the cyclic. It is '
well designed'. The main rotor collective control for a 369 is very light but able to control large thrust. The size of the 369 TR is about the same as the TR of a Mil26, which is a very large helicopter.
The pedal forces are a function of the Centre of Pressure being a significant distance from the Pitch Change Axis of the TR blades, this is a function of design and is not necessary, therefore hyd assisted TR pedals are not necessary if the TR were designed to not require such large forces, which is evidently possible. If you can design it without an unecessary system that can kill you then you probably should try and do that. TR loads on HYD assisted AS350 have been known to cause accidents = not better off.
Crab I think you must have mis-read what I say about 2 pilots, you seem to be aggreeing, is that what you intend?:
Crab: "a second pilot is for far more reasons than just giving redundancy for medical emergencies affecting the PF"
Yes that's right, that's what this says:
Me: "A Spare Pilot
is useful
more than once per
100,000 hours when the other guy has a heart attack.
He is COMPLEMENTARY, that is he actually improves the overall performance of the piloting. This is the highest yeilding safety return.
So to summarise:
a spare engine is only bad until it's useful
and
a spare pilot is only useful until he's bad
(and then the spare pilot concept kicks in)
The Glasgow incident would probably be averted by a spare pilot, but was enhanced by a spare engine."
(and it answers JimL's point, although surprising he didn't know that/had to ask me to explain the difference. If you
really wanted safety yield you'd mandate 2 pilots before 2 engines) (Crab: the second engine is a liability (in risk (fire, explosion, freewheel unit failure), weight and complexity, carried for the day it may be necessary/useful, that day has to come often enough to justify the downsides. Does it? (How often must you have an engine failure to negate these downsides?)). The 1950's concept of having 2 engines because one wasn't powerful enough has long gone. The performance/utility of a SE Lynx variant would probably be staggeringly good, weighing 500kg(?) less, doubling(?) it's utility. They still crashed them because of 1 engine failing and there was twice the chance.)
Nubian
Yes you are quite right. I mention that in #97:
"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."
They are extremely rare to end (that) badly, and until those 2 very recent examples, there were
almost no cases, but in any case many fewer than caused by 2 engined helicopters in urban areas. Everything is possible and will occur with
some frequency, it's really just a case of what that frequency is, how grave are the consequences and whether it's acceptable.
Nobody has defined what is the
ACCEPTABLE
Level of
Safety
Performance.
In the UK in the last 10 years the 'scores' for fatalities by engine philosophy are:
TWINS: 49 dead (people on the ground 8)
SINGLES: 13 dead (people on the ground NIL)
The reputational damage to helicopters has largely come from the 2 engine helicopter. (
Societal Risk, ask Airbus)
(bigger splash !)
The case is NOT clear.
One hopes that there are serious 'experts' considering these points. (JimL, you? what's the logic?)
Rather than just being blindly wedded to the intuitive 'feeling of comfort' that the 2 engine religion gives.
Given the effectiveness of placebo effect, you can't deny that the 'comfort' plays a part. (especially for SLF)
If it makes you feel better .... you should be free to chose it, but no one should be
forced into this dubious religion.