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Category A Takeoff: Background

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Category A Takeoff: Background

Old 12th Apr 2019, 20:09
  #101 (permalink)  
 
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MG & Crab - yeeup, stylish arrival, and the girl dun good too (300hrs)
As for 2 tail rotors, yup there are some pretty silly ideas around, same with gearboxes, 2 of those too???
Control runs, duplicate? Even sillier what about 2 types of fuel incase one is contaminated?
Dual rotor head? KMax, either rotorhead can get to to the scene of the arrival??

What next? Two pilots? Ah yes that is good idea since 80% pilot error.
As for 2 engines, 600+? kg extra, for comfort (?) , why not, that seems sensible to some people?
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Old 12th Apr 2019, 20:30
  #102 (permalink)  
 
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Originally Posted by AnFI View Post
MG & Crab - yeeup, stylish arrival, and the girl dun good too (300hrs)
As for 2 tail rotors, yup there are some pretty silly ideas around, same with gearboxes, 2 of those too???
Control runs, duplicate? Even sillier what about 2 types of fuel incase one is contaminated?
Dual rotor head? KMax, either rotorhead can get to to the scene of the arrival??

What next? Two pilots? Ah yes that is good idea since 80% pilot error.
As for 2 engines, 600+? kg extra, for comfort (?) , why not, that seems sensible to some people?

Well I found it quite comfortable having two when one of them went bang over a congested area allowing me to fly to my base rather than ditch in a river. Pretty sure my pax did too.
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Old 13th Apr 2019, 15:18
  #103 (permalink)  
 
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OvertHawk
You are of course spot on.
That’s the point, more comfortable.

Sometimes carrying a spare engine WILL be helpful. Like your case.
Quite right you feel more comfortable.
Much nicer to fly home than to swim to shore.

You must take that upside and weigh it against the downsides.
Against the ONE HUNDRED TIMES MORE PROBABLE likely causes of your death.

Your comfort from the spare engine needs to outweigh the downsides.
If it does 'you’re good'.
It needs to outweigh the chance that a freewheel unit will let go and tear off your gearbox and rotor head. That the overcomplicated gearbox doesn’t break and leave you without counter gravitational support. (poor sods). Your hydraulically assisted tail rotor (why does it need to be hydraulically assisted?) doesn’t force full travel and leave you like my friend in Leicester.

When those things happen you don’t get to swim to the bank, but you’d wish (briefly, as you remember this post) you could be given the chance instead to simply autorotate.

make sense?
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Old 14th Apr 2019, 04:23
  #104 (permalink)  
 
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In 20K hours the only emergencies I ever had were two hand grenade engine failures, fortunately both in twins. The first one would have resulted in the likely death of all eleven had it been a single. Blessed are those who fly twins.
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Old 14th Apr 2019, 16:15
  #105 (permalink)  
 
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Originally Posted by megan View Post
In 20K hours the only emergencies I ever had were two hand grenade engine failures, fortunately both in twins. The first one would have resulted in the likely death of all eleven had it been a single. Blessed are those who fly twins.
So had it been a single, which one of those two engines would it have had? The one that blew up or the one that didn't...
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Old 14th Apr 2019, 17:18
  #106 (permalink)  
 
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Originally Posted by chopjock View Post
So had it been a single, which one of those two engines would it have had? The one that blew up or the one that didn't...
well, doesn’t really matter, cause he returned safely.
I recal al sputtering turbine on a Bell206, everytime I increased power.
Nursed it home and they found, that parts from the compressorhousing, the area where the blades spin, went through the engine....
What a tense feeling looking for spots to autorotate to in case of....
What a different, nice feeling in a modern twin, knowing that an engine failure wouldn’t impair take off or landing path.
Or hovering over a build up area, possible to relax cause the remaining engine would keep me there for 30 sec or with a little fuel burned, 2 ˝ minutes, without any need of immediate action (sure I would react - but I wouldn’t be cought out looking outside i.e.)
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Old 15th Apr 2019, 11:12
  #107 (permalink)  
 
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Originally Posted by AnFI View Post
Your hydraulically assisted tail rotor (why does it need to be hydraulically assisted?)
I thought you were a helicopter pilot and instructor AnFI................

Surely you have flown something like AS350 and done hyd- out landings? Which was the most difficult control? Yaw by any chance? Now double the AUM and the size of the helicopter and try flying it without hydraulics...............
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Old 17th Apr 2019, 19:18
  #108 (permalink)  
 
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Of course AnFi - I was forgetting that your main interest is in trying to get singles access to fly over congested areas and also obfuscating when questions are asked about fuel planning on long overwater trips..........I suppose if you run out of fuel, the whole single vs twin argument becomes irrelevant...........
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Old 18th Apr 2019, 17:47
  #109 (permalink)  
 
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Personally I think with more reliable engines now this whole thing on CAT A take off's should change, recently looking at accident reports that has proved to be the case.
They are not fit more the modern helicopter the profile should change according to site landing/take off requirements to make the best of what you got.
How? that's a tuff cookie to crack, but surely were looking for the safest way in and out, should something unforeseen happen and a CAT A take off isn't it!!
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Old 18th Apr 2019, 18:11
  #110 (permalink)  
 
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Until you can guarantee 100% reliability of engines you are very unlikely to get things changed, especially without a viable alternative. I know that doesn't address any of the other particular component failures but finding a one-size-fits all procedure is the stuff of fantasy.
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Old 19th Apr 2019, 00:17
  #111 (permalink)  
 
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I assume all the anti Cat A protagonists take the same view when it comes to their loved ones flying on commercial airlines? No need for any of that engine failure accountability nonsense - it will all be fine!
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Old 19th Apr 2019, 18:17
  #112 (permalink)  
 
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Good one 212man!
All I have to say is that when I had an engine resign (very loudly!) in a 206L I sure wished I had another one.
I had 3 engines quit on me all in single engine airframes. I was very, very lucky never to roll one up in a ball.
Strangely enough never had a failure in a twin.
I think my total time is about 50/50 between singles and twins.
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Old 19th Apr 2019, 19:13
  #113 (permalink)  
 
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I'm doing a lot of single time at the moment and. while the engine has a very good history of reliability, I am much more conscious of what I overfly and at what height!
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Old 19th Apr 2019, 19:18
  #114 (permalink)  
 
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Hey Crab , i see you revert to your old practice of attacking the man, nothing constructive to say? Could we agree to keep it on the technical points?
(i feel a circular discussion coming on unless you can keep to the points)

(the point about hydraulics was to make you think. why are hydraulics necessary on a helicopter tail rotor? (it's a rhetorical question). Bad design maybe? Especially if it involves introducing an unecessary system to a system that can kill you, once per 50,000hrs. As for your point about forces on an AS350 with the hydraulics turned off, I am sure you can see the flaw with your question, moving hydraulic fluid around is hard work. If the centre of pressure is too far behind the pitch change axis then there also a lot of unecessary work to do, (bad design; that could be offloaded by spring). The main rotor of an H369 is about the same size as the Tail Rotor of a Mil26, 5 blades too. The H369 does not have hydraulics, and moving it's collective lever forces, with your feet would not be at all difficult. So why do you need hydraulics on a helicopter TR (?) , answer is you don't.)

Crab wrote: "I suppose if you run out of fuel, the whole single vs twin argument becomes irrelevant........... "
Yes spot on, and very topical wrt the Glasgow thread. Pretty pointless having 2 engines there and killing all those people.
Better over a Hostile Congested Area in a single with fuel, than in a twin with no fuel.
Given the choice 'spare fuel' or 'spare engine' which one delivers real world benefits??
Fuel is a real world necessity. (anyone flying over long stretches of the worlds most inhospitable water has probably worked out their fuel. If their engine were to stop, for some strange reason, then their chance of survival (according to JimL) should be 10^-9. If they did survive then its not 100% fatal right? It's just inconvenient. Inconvenient requires 10^-3 reliability ? )
Complexity kills too, you have fuel but you can't figure out how to get it to the engines, this is NOT PILOT ERROR, this is inherent in complexity.
Complexity is dangerous, 2 pilots partially mitigates that.


Singles do fly over congested areas. They do so almost completely safely, relatively (with 2 very rare recent exceptions).
Please ge back and look at thread #97 to see what heavy twins do in congested areas.
If 'North Sea twins' flew over cities, then the Catastrophic outcome would be obviously unacceptable. IMAGINE G-REDL in central London, ouch, it would look like Glasgow but much worse. 'Leicester' catastrophe, in the city centre, no good). If the Tail Rotor failure that happened to the police AS355 helicopter in Wales had been an AW139 then imagine the impact damage to the house. Mass kills.
The only previously airbourne helicopters that have killed anyone on the ground in the UK are twins.

There is no justification for mandating multi engine for helicopters over congested areas, it will lead to more deaths not less.

The focus on engines is totally distorting the approach to the actual cause of deaths. It's 99% NOT engines.
If you want to set an Acceptable Level of Safety Performance then looking at engines isn't going to get anything achieved at all.
What is the ALoSP for a State?
1 death per person on the ground per million hours ? 10 million hours?
Where is that number? Currently for twins is it running at about 1 fatality per 100,000hrs, worse ? Who knows? WHO is in charge of this?
The ONE THING that it is very insensitive to is engine reliability. It is the single least helpful indicator of anything to do with safety.

(serious if you can please Crab)

212 the engine argument for aeroplanes is totally different to the consideration for helicopters for many fundamental reasons.
Aeroplanes don't combine the drive to a common output. Airliners have more independent engines. Airliners land very much more energetically than helis in autorotation.
Gearboxes and freewheel units and tailrotors make the mix of what gives best safety yeild different. By far the most important component is the pilot. Aeroplanes just HAVE to keep moving. Helicopters can land non fatally almost anywhere. In a helicopter use of 2 engines introduces additional mechanical risk factors. Sometimes you are better off in a helicopter having a bigger window than another engine, more chance to see the wires. Helicopters operate in environments where the biggest practical benefit is real performance margins and reliability. Reliability is not acheived by redundancy. Redundancy gives increased unreliability in exchange for (a degree of) fault tollerance.

Albatross, unlucky/lucky you. You must have had a few more hairy moments too i bet.
Crab, singles, good for you, PM me if I can help, don't lose too much sleep about what you fly over, it's the OTHER 99% ways to die you want to watch out for.

Last edited by AnFI; 19th Apr 2019 at 19:19. Reason: adding
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Old 20th Apr 2019, 02:39
  #115 (permalink)  
 
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Why don't you get a job with the regulator and have the system/design changed. According to you the people doing the job don't have a clue.

Accidents by activity- Commercial air travel & aerial work - Training 7.62%, Positioning/Ferry 5.1%, Air travel 14.6%, Agriculture 7%, Passenger/Cargo aerial work 38.2%, External load 3.2%, Aerial observation 1.3%, Air tour/sightseeing .65%, Emergency medical 5.1%, Utilities patrol 12.7%, SAR 1.3%, Other 3.2%.

Accidents by immediate cause - System failure 22%, Errors 38%, Violations 33%, Other 7%.

Accidents caused by system failures - Engines 75.9%, Main gear box fire, Tail rotor blade breakage, Directional control failure, Pitch control failure, Tail boom breakage, Tail rotor pylon breakage, Trimming failure, each contributed 3.4%

Accidents by error - Misassessment of weather 18.2%, Misjudgement of landing 8%, Not going around 4%, Flight below MSA 21%, Overload 2.8%, Not considering wind 2.8%, Inadequate pilot judgement 34.7%, Poor circumspection 8.5%.

Accidents by violation - Violation of MSA 55%, Violation of weather minima 30%, Other 15%.

The figures are according to the International Helicopter Safety Team, but what would they know.
PM me if I can help
Crab, my advice is, DON'T.
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Old 20th Apr 2019, 14:29
  #116 (permalink)  
 
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AnFI, if you intend to quote someone, perhaps you should provide a reference or justify your statement:

If their engine were to stop, for some strange reason, then their chance of survival (according to JimL) should be 10^-9.
You need to explain why redundancy with pilots, does not add unacceptable complexity!

Redundancy is only required when a component (or system) doesn't meet a specified reliability target and the consequences of failure is not acceptable - to some criterion.

Protection of third parties is the highest priority with aviation Authorities; the next is CAT passengers.

To my knowledge, there is no regulation that prevents a pilot, of other than a CAT flight, from flying over a sea area where a failure of the engine or another system would result in a hazardous or catastrophic outcome. Rules of Air kick in only when third parties are exposed.

Jim

Last edited by JimL; 20th Apr 2019 at 16:25.
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Old 21st Apr 2019, 07:19
  #117 (permalink)  
 
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(the point about hydraulics was to make you think. why are hydraulics necessary on a helicopter tail rotor? (it's a rhetorical question). Bad design maybe? Especially if it involves introducing an unecessary system to a system that can kill you, once per 50,000hrs. As for your point about forces on an AS350 with the hydraulics turned off, I am sure you can see the flaw with your question, moving hydraulic fluid around is hard work. If the centre of pressure is too far behind the pitch change axis then there also a lot of unecessary work to do, (bad design; that could be offloaded by spring). The main rotor of an H369 is about the same size as the Tail Rotor of a Mil26, 5 blades too. The H369 does not have hydraulics, and moving it's collective lever forces, with your feet would not be at all difficult. So why do you needhydraulics on a helicopter TR (?) , answer is you don't.)
Perhaps with your aviation time spent solely on light singles, you fail to understand the concept of disc loading - the harder you make the rotor work, the bigger the feedback forces and the more power required to combat those.

Have you never wondered why pretty much every helicopter over a ton and a bit has hydraulic assistance for main and TR?

Perhaps your ego asserts that you are man enough to manage such forces hour after hour but for us mere humans the hydraulics are essential.
You could of course just double the size of the main and TRs to reduce the power they consume but that's not very practical, is it?

As to playing the man, well you want to have your cake and eat it AnFI, you like to use your 'secret, Clark Kent' identity on PPRuNe to harangue and badger aviation professionals with your special agenda and use your 'Superman' persona to try to force your will on regulators.

Crab, my advice is, DON'T.
Megan - don't worry, I have played that game before and he just gets abusive
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Old 21st Apr 2019, 11:27
  #118 (permalink)  
 
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JimL, thanks for the sincere answer, great respect to you for that, I hope these are useful points.

Originally Posted by JimL View Post
AnFI, if you intend to quote someone, perhaps you should provide a reference or justify your statement:
Jim
Hi JimL; it's a paraphrse rather than a quote. it's a mathematically tongue-in-cheek implication of what you say about probability of catestropic events, you say should be 10^-9 (10^-6 would already be pretty darn good), this 'catastrophy' is a conflation of your product of probability of risk factor and probability of fatal outcome (catestrophic consequence). If you hold that the consequence IS 100% fatal (which you do) and If the risk x consequence is < 10^-9 (you use), 'given' that the risk becomes a certainty then if the consequence is actually survival (for an event), then it must have been very very very lucky to survive, something like 10^-9. Of course the truth is these consequences are being wrongly identified as 100% fatal. If you had a 99:1 chance of survival, and the acceptability of the event were 'reasonable' ie 1 per million hours, then the aircraft would only need 10^-4 probability of forced landing.


Originally Posted by JimL View Post
You need to explain why redundancy with pilots, does not add unacceptable complexity!
Jim
Good point. In a complex aircraft, the reality is that a single pilot can easily be swamped by work load and confusion, his 'flight secretary' can reduce the work load to a manageable degree. The pilot error rate for a complex single pilot machines opperated by the most basically qualified pilot would be ludicrously high. It's an error rate that can justify the extra weight of another pilot.
It's a weight / utility / complexity calculation:
A spare engine is only doing BAD STUFF for you, ALL THE TIME, it's introducing extra freewheel, extra explosion risk, extra gear box complication and payload consumed etc etc
It has to make up for it by being useful. The only time it gets to do that is ONCE per million hours. Really obviously not worth it.
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.


Originally Posted by JimL View Post
Redundancy is only required when a component (or system) doesn't meet a specified reliability target and the consequences of failure is not acceptable - to some criterion.
Jim
ALoSP: You need an expected death rate for people on the ground per 100,000hrs to determine whether it is an 'acceptable rate'.
The principle that you can't have any death at any cost is not realistic. If that were the case everything would have to be banned.
The HSE provide clear guidance about the value of economic activities incurring mortal costs and is clear that one can expect a degree of cost.
They suggest figures like 10^-3 per year. What is the probability of a given person on the ground being exposed to death from over flight of a single engined helicopter vs a multi engined helicopter? Something like 1 per 1000 billion hours?
What differentiation in that rate occurs by engine type? Anything measurable? How much is it? How unacceptable is it?
"you have to measure it to regulate it" - QUOTE?
Is someone actually computing the ALoSP - rather than some random application of an inappropriate criterion for component reliability.
10^-9 was set for critical components. A Tail Rotor, a Gearbox, a RotorHead, Control Runs are made from an assembly of many components where 10^-9 is applied in manufacture to those component parts. These are the component reliabilities that deliver between approx 0.1 and 2 fatalities per 100,000hrs.



Originally Posted by JimL View Post
Protection of third parties is the highest priority with aviation Authorities; the next is CAT passengers.
Jim
What outcome risk level is the criterion? There does not appear to be a 'target'. There is no case made for there being a greater or lesser risk by mandating engine redundancy.

Originally Posted by JimL View Post
Protection of third parties is the highest priority with aviation Authorities; the next is CAT passengers.

To my knowledge, there is no regulation that prevents a pilot, of other than a CAT flight, from flying over a sea area where a failure of the engine or another system would result in a hazardous or catastrophic outcome. Rules of Air kick in only when third parties are exposed.
Jim
Not only is it debatable that engine redundancy delivers reduced risk to these 3rd parties.
ALSO
as you say the priority is to 3rd parties. For people on the ground that would entail you restricting (banning) PRIVATE HELICOPTERS from overflight of hosile congested areas. (and under your definitions hostile congested areas include playing fields, parks, rivers, car parks etc etc)
Is it justified? By what criteria in deaths per hour, say?

Did you look at post #97, how do you account for that, most death is not engines.

Crab, v personal again, some heli TR have hydraulics not does not equal MUST have hydraulics. The 'why' i answered.
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Old 21st Apr 2019, 13:33
  #119 (permalink)  
 
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That is the most extreme example of the introduction of complexity seen for a while.

Will you please refrain from scattering your posts with false accusations and inaccuracies. For example:

it's a mathematically tongue-in-cheek implication of what you say about probability of catestropic events

For people on the ground that would entail you restricting (banning) PRIVATE HELICOPTERS from overflight of hosile congested areas. (and under your definitions hostile congested areas include playing fields, parks, rivers, car parks etc etc)
However tongue-in-cheek that might be!
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Old 21st Apr 2019, 13:55
  #120 (permalink)  
 
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Originally Posted by AnFI View Post
What outcome risk level is the criterion? There does not appear to be a 'target'. There is no case made for there being a greater or lesser risk by mandating engine redundancy.
Not only is it debatable that engine redundancy delivers reduced risk to these 3rd parties.
ALSO as you say the priority is to 3rd parties. For people on the ground that would entail you restricting (banning) PRIVATE HELICOPTERS from overflight of hosile congested areas. (and under your definitions hostile congested areas include playing fields, parks, rivers, car parks etc etc)
Is it justified? By what criteria in deaths per hour, say?

Did you look at post #97, how do you account for that, most death is not engines.

Crab, v personal again, some heli TR have hydraulics not does not equal MUST have hydraulics. The 'why' i answered.
Hey AnFI,

Here is links to 2 very recent accidents (and far from the only ones) with your favourite machine.... Both R-44's involved innocent dead 3rd partys on ground....

Brazil:

Sao Paulo R44 crash

Florida:

R44 down killing a passenger in a passing vehicle

Now, I really look forward to see your explanation of these.....



When it comes to twin engine helicopters and the requirement for this. It has been produced twins long before it was seen as a requirement. (and HYD assisted flight controls as well)
I think helicopter designers around the world would know this better than a mere FI from England....

When you're on about the overcomplexity.... Why did your favourite brand introduce HYD for the R44?? It worked fine with the electrical trim..... (at least when it was working, but why did it need the trim in the first place??) Why did they had that big chunk of tungsten on the cyclic before the HYD was added? Feedback perhaps? On such a light machine?! Should be completely unnecessary!!!


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