Nubian
I believe Anfi has said twice he was referring to the tail rotor... And the electric trim was 5hite on the R44.

no, he argued that since a 369 main rotor was the same size as a Mi 26 tail rotor and the former didn't need hydraulic assistance, it followed in his logic that the latter, or any other TR for that matter, didn't need hydraulics which is clearly cobblers.
Perhaps he forgets that the 369 had electric trim actuators to reduce the control loads as well - you never know with AnFI, he flip-flops from one part of the argument to another without pausing for breath.

Perhaps he would like to show how a 6 tonne helicopter can have a TR without hydraulic assistance?
I am sure his answer will be that it just isn't designed properly since his ego puts him so far above the legion of designers, engineers and manufacturers who have been making helicopters for many years.

AnFi, have you ever operated a multi-crew helicopter on anything other than a sightseeing jaunt? perhaps you might better understand that having a second pilot is for far more reasons than just giving redundancy for medical emergencies affecting the PF.

The spare pilot is useful all the time when used correctly - he is there to monitor the PF when conducting critical manoeuvres, especially IMC - not just to act as the in-flight secretary...

The spare engine is useful ALL of the time since it is not a spare but permits greater capability from the aircraft ( AUM, payload, speed etc) than a single engine helicopter. How many 6 to 8 tonne single engined, helicopters are there btw?

crab
I'm not sure you are right there.
Have you considered the Bell 214 v Bell 212 for example?
Or the AS350 v AS 355?

The reason there are not many heavier twin types made is most likely due to the regulations requiring twins...
Ever thought why the K-MAX only has one engine?

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.

So now you have narrowed your 'excellent' statistical analysis just to UK because worldwide statistics don't suit your argument - that is both barrels in both feet AnFI

:rolleyes:
xxxxxxx

You certainly haven't.

Isn't that how statistics work? Sometimes nothing bad happens for ages and then it does? The 2 cases Nubian mentions happened, despite your logic and single engined helicopters with engine problems killed people on the ground - dress it up however you like but a single engine helicopter with an engine failure over a congested area is FAR more likely to have a catastrophic outcome than a twin engine helicopter having a single engine failure........

Do you mean center of pressure or do you mean aerodynamic centre? Do please explain how you will design a tail rotor system where the CP is consistently aligned with the pitch change axis - you understand that the pitching moments change with AoA????

a bit like serious politicians considering UKIPs fantasies perhaps:E

Go back to school, and learn again the difference between correlation and causation.
AnFI: All Noise, Feckall Insight.

One would have thought that for as long as you've been involved in rotary wing aviation, you'd have run across a clue.
Nope.

Crab ; yes you are right - I have not, (I have suggested some figures) ... but neither have those purporting to:
ref post #118 re ALoSP - why not ??
"Isn't that how statistics work?" yes it is. "dress it up" no need to, that's how stats work, I AGREE

"a single engine helicopter with an engine failure over a congested area is FAR more likely to have a catastrophic outcome than a twin engine helicopter having a single engine failure........" yes true, but that's not the point, that downside has to not be out weighed by the increased fatalities from other consequent fatal accidents, caused by excessively focusing on engine redundancy. (Like those in post #97). It is not clear that happens. It's just a 'nice idea'.

"Do please explain how you will design a tail rotor system where the CP is consistently aligned with the pitch change axis - you understand that the pitching moments change with AoA????"
I do, and I understand when they don't too. You'll have to look that up yourself, it's really obvious, class is closed for today.

Let's get to the bottom of this. I take it you aggree with much of what I say, eg 2 pilots/1950s/some downsides/some upsides
You agree that the upsides should be measured against the downsides and not just upsides in isolation?
It should be measured in terms of ALoSP (agree?), the people considering this issue are not producing this figure.
Why not? because it doesn't work?

Lonewolf 50 "Go back to school, and learn again the difference between correlation and causation." I didn't make any comment regarding cause or correlation, it's just a factoid. What should I be learning about those ideas at school, and why should I learn it again? Always happy to learn, feel free to point out what clues you think I've missed.
"... for as long as you've been involved in rotary wing aviation" - I don't claim any experience, just looking for a logical analysis.

It would be great if JimL could answer some of the substantive points, it would be interesting, he is regarded as an SME. What's the ALoSP?
Should we balance upside against downsides? Is it worth it? How worth it?
What's the CBA? Is there one? Aren't you interested to know? or you already do?

Here's me thinking that reputation was brought about by the Robbie. You do know the Puma accidents had nothing to with engines, or numbers there of? Perhaps not.

hahaha - that one is just hilarious...........

AnFI, why don't you just admit your agenda is doing battle with the regulators to allow (or not restrict) SEH over congested areas and stop beating around the bush with made-up statistics and circular arguments.

DB has summarised the argument succinctly but you keep banging on about engine redundancy like you have just invented the cure for the common cold.

DB - no, we all know who the pig is but it is fun to prod him now and again:ok:

Chopjock look at why the 214 was upgraded to the ST - performance, with safety as an added benefit.


As for the Kmax - it has a single purpose which doesn't include CAT.

Hehe, Chop Chop!

I know very ''well'' how the trim worked, thanks...

Now, I wonder if you 2 geniuses can't just contact MIL and ask them why they don't develop a single engine MI26?? You guys are brilliant! For sure, it would be saving the weight of the ''other'' extra deadweight, combining gearbox, and all those extra bull**** systems not needed. Leave out the HYD systems, as that just complicate stuff...and a real Chop/AnFI designed machine would need only 1 pilot (with fairly strong arms) to fly it. When you're at it, maybe you should ask Sikorsky as well, why the hell they have been making the S64/CH54 all these years with 2 engines...Completely waste of time and efforts! Those were sure as hell not made with regards to overfly congested areas and CAT operations according to EASA regs.

Yeah, the Kamax is a real great example no?! What a success story....

As for the 214's, originally planned exclusively for Iran and military use. Khomeini changed that plan...

AnFI,

Without more info on the numbers, you don't have a case.
Can you from your numbers above, perhaps tell us the number of flight hours generated for twins and for singles, so we can divide the dead per hour? You can keep it for the UK for now, and we get the numbers world wide later.

Maybe you can give us a list of controlled in flight engine shut-downs (twin), due to some sort of problems, where the result was return to base, land and do some extra paperwork vs. Single engine failure, forced landing/crash and even more paperwork done by someone else?! Also per flight hours? The UK would do for now.
Preferably, split into private/corporate non AOC work vs. commercial operation.

Numbers are easy to manipulate to support any agenda, even a poorly thought out one.
Without background data such as the amount of missions or hours flown, or even the number of accidents avoided, numbers on their own are meaningless.
The heavier category aircraft have all had a larger crew count, thus more fatalities, which has been used to imply the aircraft are less safe, which is creative mathematics in action.
Including Clutha in the calculation is just plain old fashioned scumminess.
With the backwards logic demonstrated, you would have to conclude that airline travel is incredibly unsafe - just look at the fatalities each year.
In Anfi's world that probably makes sense since those poor buggars are stuck with up to 4 engines, that's more than double the danger of any twin.

AnFI - as I am sure you know, creating ALoSP requires a State Safety Plan including Safety Performance indicators to accurately produce data. This data needs to be based on a mandatory reporting system that highlights the required SPIs and therefore relies on operators being truthful about causes of incidents so that accurate data is recovered.

Imagine if someone, say, ran out of fuel and lost an aircraft (fortunately without loss of life) and then was untruthful about the cause of the fuel shortage (piss poor planning perhaps) - surely that person would be guilty of undermining the whole ASoLP process - just a hypothetical scenario but worthy of consideration.

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?

A fully "Mandraulic" helicopter i.e. one without powered flight controls cannot, by definition, have an autopilot. Any helicopter flown in IMC requires an autopilot. Having trained to fly unstabilised, single engined helicopters in IMC from an early stage in my career and having had to fly an unstabilised twin in a later public transport role (it used to be allowed some twenty years ago), I would not want to do it ever again.

One engine = one power source for electrical equipment. If it stops, you are going downhill and possibly without some of the normal electrical systems, making your life even more difficult.

Accident statistics involving twin engined helicopters operating over congested areas might seem relatively high compared to singles, but a single cannot have an accident over a congested area if it is not allowed to be flown there.

You opening classes is a waste of time. Find another profession, I'm a slow learner, but I've failed to learn anything from any of your posts. Just a troll IMHO.

All things aside, the regulator decides what can and can't be done with a single or twin, flight over water being a biggy.

Remember the early days of a certain twin, we became expert at single engine landings (not that it takes any great skill) because of precautionary shutdowns. Engines were eventually sorted. Not unlike the MAX having recent engine failure troubles, down to carbon build up on the combustor disrupting airflow pattern. Glad it had another to get back, else there would be a third MAX in the dirt, parked in the suburbs of Orlando.

AnFI, I've tried to stay out of the circular arguments that ensue from your assertions, but I'd suggest that statistical analysis is one area that you need to brush up. Flat base stats without background are meaningless, since the exposure of single/multi engine types to the operational areas is a main feature which is ignored by you yet would significantly change the data that you are (so far) presenting.

Something like the year-to-date road fatalities so loved by many roads and policing authorities which completely ignore VKT, annual growth numbers, age groupings, 5 year trends, 12 month comparisons etc. You really are making a bit of a clot of yourself by creating inaccurate data references which mean absolutely nothing :ugh:

Now, I am no expert in aircraft economics but it does occur to me that what determines if a type is profitable or cost-effective to run, requires a few more variables than just the number of engines, and the associated capital and direct operational costs.
You can choose to ignore that regulators determine the minimum required for operations and that this has been done as a result of many hard lessons learned over decades.
There is only so much you can move with a single, to be cost-effective, how much and how fast you can transport something is of more importance to the cost equation.
Add to that the liability should something go wrong, and what another engine costs becomes unimportant.
Why do you think Boeing and Airbus aren't investing their money in single-engined airliners?
You continue to choose ridiculously over-simplified points to support an argument that is entirely non-sensical.

If you really want to save everyone some money, then perhaps you can also discuss how pointless certification and testing is. This really does cost people money, so let's get rid of that also, it's just unnecessary regulation if you ask me.
While you're at it, all this training that has to be done. What a waste of time and money, let's get rid of that as well.
We need more visionaries like you :}

DB, Shy, megan, JE and BR

There are some really good points there, thank you.
They do throw out a few elements out that might help the religious extremists understand the infidels, and maybe vice versa.

DB: 2 engines as an insurance policy. Very good point on so many levels. If you had no accidents in many years then you would expect the premium to be low. ie STILL WORTH PAYING. If the premium is ridiculously expensive then it fails
Cost Benefit Analysis.
So its all about CBA !
Fully comp, 3rd Party?? $10k per year to insure the hull of a $10k automobile, not worth it. So 3rd party only.
INSURANCE (premium) IS A MEASURE of the RISK.
3rd Party Insurance for a helicopter to insure the risk of people on the ground IS THE free market PRICING of this risk.
Look at the ground payout risk to insurance companies for Twin Engine helicopters in urban areas. Cultha is expensive.
North Sea helicopters over cities... could be very expensive.
Carrying a spare engine as an insurance policy is very expensive:
What cost 500kg being carried for 100,000hrs??? $100,000,000?? Very expensive just to insure against a 'fender bender'. Unrealistic.
It does not indicate it's worth it, and because it doesn't make sense the state(? or who ?) imposes it. T'aint right.
People are generally upset with being pushed around without justification. We expect more from our 'experts'.
["applies to SEHs but no one has ever exploited it." (I think an operator out of London Heliport does)]


Hi Shy, my engineering degree friend, some questions for you:
1 'Mandraulics' (great term) sure, agree - no good for autopilots.
As for Tail Rotors: IF Hyd TR is not necessary AND HydTR can kill you, THEN do you chose HydTR? (AW139 drivers?)
2 "One engine = one power source for electrical equipment." Sounds like a thoroughly lousy reason to carry a spare engine.
Spare electricity can be provided in so many more ways. Maybe like HYD, a GENi on the XMsn(?), if you were really worried about that then 30kg of extra batteries would do it ... OR 500kg of spare engine complication ((that can kill you)).
Which source of spare electricity would you chose?
3 'Stats against Twins look bad, because the singles aren't flying there'. You said it. YES THEY DO LOOK BAD... they are bad. The singles ARE THERE (eg only restricted in LONDON by R160) and the rest of history and the rest of the world leaves a data set that blows that argument away, and that argument flips the other way too: look at the MAJOR twin accidents that have not killed people on the ground because they were over barren sea/land, and NOT over urban areas !! Had they been over urban areas we'd have a total disaster for helicopters in general. (maybe over the NS but over London? A risk worth taking??)
4 Engineering wise: isn't simplicity the goal? Leonardo DaVinci, Simplicity is the ultimate sophistication. Occam, Newton, Einstein, KISS (Kelly Johnson). Not a fan of simplicity ?

megan "the regulator decides what can and can't be done", yes and has a duty to do so judiciously (for better reasons than just the retirement plans of some ex-employees). They have a LEGAL DUTY to decide in a judicious way.
They have not laid out their reasoning, and they should. Is it ok to avoid the daylight and push this through on the QT? What is their ALoSP? What is the likely fatality rate in 3rd Party Deaths per 100,000 hours of urban overflight? How does it compare to singles? Estimates anyone?
"Remember the early days of a certain twin, we became expert at single engine landings" I think the common theme often here is the "early days", and it makes the position understandable. Sure in the very 'early days' there were 2 engines because they didn't have single engines powerful enough. Engines were very unreliable, and there's no doubt that there's a reliability number at which it is worth carrying a spare. There's also a number at which it is not worth it. THAT number is the question. For instance at 1 per million hours, the price of carrying a spare is almost certainly not worth the Cost of carriage, Complexity (pilot and systems) and Increased failures of other systems compared to the very very rare usefulness of it, will not be 'worth it'.

JE
You are right, there's no analysis from me there, it's just a fact but it's not an inacurate one (as you alledge). There are all kinds of factors to apply to see it 'in context'.(ie make excuses for it). It's not good though is it? There'd have to be a lot of flying going on in twins to reverse that bad news for twins. 8 times more to make twins just twice as good. If twins, with all their other mitigators, only managed twice as good would it be worth it? Twins are flown by more experienced pilots, required to have more training, often are Multi Pilot (the biggest yeilding factor), more likely to have better other equipment.
According to EASA Safety Review 2018
25% of Offshore fatal accidents were from engine failure (twin)
5% of Other Comercial Air Transport was engine failure (also twin, no singles), most other causes were wires and weather and LOC.
However we want to spin the stats (and they are spinable, of course), there is just not a clear case, especially if you want to be rational or proportionate, or to actually cost the idea. I note your criticism of police authorities wrt road fatalities.

BR "Now, I am no expert in aircraft economics but it does occur to me that what determines if a type is profitable or cost-effective to run, requires a few more variables than just the number of engines, and the associated capital and direct operational costs." Well I think that is a really good point. The scale IS important. When the aircraft is LARGE, and carries many people there is a good case for carriage of a spare engine. It becomes a very small proportion of payload and expense. So the CBA may well show a favourable result for larger helicopters.
"many hard lessons learned over decades." yes, mostly decades ago !! Out of date now.
I understand a lot of 'old timers' are emotionally attached to spare engines. Don't want to re-evaluate their religion.
"to be cost-effective, how much and how fast you can transport something is of more importance to the cost equation."
Good point, so there's a size element to the estimation, I agree.
"the liability should something go wrong, and what another engine costs becomes unimportant." This is imagined fear, and the cost is not unimportant, it needs to be proportionate, It does cost more than money, some big accidents too... GREDL over LONDON!?!? Cultha? They need to be factored in also.
Smaller helicopters make smaller holes in the ground and don't economically/justifiably carry a spare engine so well.
"Boeing and Airbus aren't investing their money in single-engined airliners?" It really is different for Airliners. Airliners carry many more people, land with much greater destructive energy (more than just a fender-bender), do have 'independant engines', don't have a common output mechanism, don't have so many other critical components that could use the performance expenditure better, aren't so critical on pure capabilities. From the 'Airline world' Pilatus really proves the point that smaller scale singles do outperform twins. Commanche anyone? If a single makes sense in an aeroplane it makes more sense in a helicopter.
"ridiculously over-simplified points" well it's either too complex or too simple, no pleasing some people. KISS !! ?


(and THEN you have to ask: If you put the same amount of effort it making a simplex system not fail, as the resource you put in to 'preserve its unreliability' through redundancy then what result would you get?
You'd get a helicopter that didn't need redundancy, along with all it's downside costs.)
Come on America, you want to have to use twins?

Breaking News - The AnFI Aviation Safety Authority has discovered that all accidents were preceded by the crew eating food. The recommendation is that henceforth all crews be not permitted to eat food.

and most are too low at the time of the accident ...:8

Probably one of your most fatuous arguments AnFI - it's like arguing that if we had adjoining tectonic plates and volcanoes in UK we would be much more likely to die in an earthquake or eruption.
'Look, over there, that's really bad - imagine if it was over here!' So very Daily Mail and no basis for anything other than scaremongering.

I thought we had established that on larger helicopters ie most twins, a hyd TR is necessary because of the power required to operate that TR with the high disc loadings involved.
Even light singles trying to get by on a non-hyd TR can run out of authority because the designer is trying to keep the disc loading low.

And btw the crash you keep harping back to was a 169 not a 139 - another erroneous 'fact' from you.

Any TR can fail and kill you, especially in a 400' hover at high power - your argument, as usual, lacks logical progression - just because it was a hyd TR doesn't mean all other TRs are inherently safe.

Do you seriously want free access to London for singles? What is wrong with the existing helilanes? They allow sufficient access whilst minimising risk to those below - what is wrong with that.

Twins can be allowed more freedom but are still most likely to be routed along the helilanes so what is your beef - do you want all singles to have the same freedoms as the air ambulance, police and SAR? That wouldn't make doing their job more difficult would it????

1) The A139 accident appears to have been caused by a tail rotor control failure, not by a hydraulic failure. As you obviously don't hold an engineering degree, perhaps you haven't grasped the reality that control feedback forces increase markedly with an increase in aircraft size. Perhaps you drive a car with servo assisted brakes or power steering? If so, have you complained to the manufacturer that both systems add unnecessary weight, complication and expense? I doubt it. Perhaps you would prefer to fly in an airliner without powered controls? I doubt it.

2) The main thrust (!) of your campaign is to make the main rotor gearbox simpler by only having one engine. Yet now you advocate making them more complicated to generate electrical power.... I fail to see any contiguous logic in that.

3) I take it that you operate singles in other congested areas. I hope that you make a point of obtaining the necessary CAA Permissions. I always do, for twin engined helicopters.

4) Engineering always requires compromises and there is seldom a simple answer. There could never be an autopilot or stability systems, a point I already stated and with which you agreed. Pilot fatigue would become a more important factor. If you wanted to build a large helicopter with no hydraulics, there would be considerable design compromises. These would include heavier control runs, which in turn would require structural reinforcement, adding weight and reducing payload. A much larger, single engine, rather than two smaller ones, would require a far stronger and heavier gearbox that you might at first imagine. Again, it would require a far heavier structure to support it. A doubling of size doesn't necessarily result in a doubling of material strength. - it might require a "square" increase. Again, see my answer 2).

A further point. I noticed that you posted your last two replies at 01:07 and 03:54. As flattered as I am that you consider me a friend and that a prompt reply to my post obviously so important for you to stay up so late, I suggest you get more sleep, it helps engender rational thought. Obviously, as an instructor, you already will know that. I'm not flying today, but still got a good night's sleep. I hope you aren't in the air until well rested. ;)

Shy - looks like you needed a bit more sleep :E

Cost - of allowing SEH unrestricted access over congested/hostile areas = negligible, just a paperwork exercise

Benefit - to those few exercising such privileges = increased freedom - to those millions living underneath the privileged few = decreased through noise and additional risk as any failure is likely to lead to loss of life on the ground.

Analysis - pretty much a waste of time since - to quote Mr Spock - the needs of the many outweigh the needs (or desires in this case) of the few

Yes, looks like it! I've edited the word "driving" to "having".

Ah, the simple joys of being in places where special permissions aren't required and singles can operate over congested areas.
Incredibly, they do seem to get this right without flattening people below.
Catastrophic failures do seem to be few and far between.

Statistics for the US FY 2018 – first % is fleet size, second % is accidents. To make it easy those in blue have zero accidents

S350 7% 5%
BK117 2% 3%
EC120 1%
EC130 2% 3%
EC135 2%
SA330J < 1% 1%
206Bs 8% 6%
206Ls 5% 1%
212 1%
407 6% 3%
412 1%
429 1%
R-22 7% 15%
R-44 13% 21%
R-66 2% 1%
S-76 2% 3%
S-92 1%
Brantly B-2 1% 1%
Enstrom 280 1% 1%
480 1%
F28 1%
Cabri G2 < 1% 1%
Hiller UH-12/H-23 2%
Leonardo A109 1% 1%
(formerly Agusta Westland) A119 1%
AW139 1%
MDHI369 6% 15%
600N < 1% 1%
Restricted Category (all TCs) HH-1/TH-1/UH-1 5% 5%
OH-58 3% 4%
Schweizer Rotorcraft Services Group 269/300/TH-55 4% 8%
Scott's Bell 47 5% 1%

Megan - don't tell AnFI but it almost looks like single engine helicopters have the highest accident rate......................surely that can't be true or AnFI would have told the truth in the first place:E

Woah, who would have thought....