Where does the UK/JAR "twin only" mentality come from?
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Tandem Rotor;
Having experience of both I know you are right.
DB;
The Scillies crash resulted in the addition of RadAlts, and a few other changes and was very relevant to today, much as I hate to say it as two good friends went on the Brent Spar and the Cormorant Alpha, they were basically due to mishandling the aircraft, not automation problems.
SND
Having experience of both I know you are right.
DB;
The Scillies crash resulted in the addition of RadAlts, and a few other changes and was very relevant to today, much as I hate to say it as two good friends went on the Brent Spar and the Cormorant Alpha, they were basically due to mishandling the aircraft, not automation problems.
SND
Avoid imitations
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The Military system seemed to say, we'll teach you everything we know, show you every component, practise every emergency, and when we say you're good enough we'll call you limited combat ready for a while under supervision before you're in charge of it.
The civi system said, we can't afford any more, you need to be out in this earning revenue, get your head in the books in between jobs and pray nothing serious happens in the first few hundred hours. Then I had a 1 hr briefing and 40 minute flight to 'convert' to the 135 T2 with its glass cockpit and 3 axis AP! Same again with the P2. It's all about the MONEY.
The civi system said, we can't afford any more, you need to be out in this earning revenue, get your head in the books in between jobs and pray nothing serious happens in the first few hundred hours. Then I had a 1 hr briefing and 40 minute flight to 'convert' to the 135 T2 with its glass cockpit and 3 axis AP! Same again with the P2. It's all about the MONEY.
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Just to further highlight the extremes, when our Sqn was re-equipped with Mk9 Lynx from 7s we attended a differences course at Middle Wallop (skids to wheels being the main difference!) which included about 4 days in the simulator doing procedural Tacan work, flying DME arcs etc, just because there was one more instrument in the cockpit!
Maybe the UK "twin only" mentality is just an construction from the yellow journalism that dogs the helicopter world there.
On the other hand, engine failures are so common in that part of the world that even a sensationalistic article from a couple days ago failed to even make a mention on pprune.
Press and Journal - Article - ?Our terror in copter plunge?
On the other hand, engine failures are so common in that part of the world that even a sensationalistic article from a couple days ago failed to even make a mention on pprune.
Press and Journal - Article - ?Our terror in copter plunge?
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Malabo;
That's just the P&J, maintaining it's usual abysmal standards of journalism.
People used to say of the P&J that the day after the Titanic sank the headline was "North East man dies in boating tragedy."
I've appeared in that august publication and the story bore no relationship to the truth whatsoever. (I trawl the transvestite clubs and call myself Susan on weekends, not Thursdays)
SND
That's just the P&J, maintaining it's usual abysmal standards of journalism.
People used to say of the P&J that the day after the Titanic sank the headline was "North East man dies in boating tragedy."
I've appeared in that august publication and the story bore no relationship to the truth whatsoever. (I trawl the transvestite clubs and call myself Susan on weekends, not Thursdays)
SND
Originally Posted by Art of flight
Just to further highlight the extremes, when our Sqn was re-equipped with Mk9 Lynx from 7s we attended a differences course at Middle Wallop (skids to wheels being the main difference!) which included about 4 days in the simulator doing procedural Tacan work, flying DME arcs etc, just because there was one more instrument in the cockpit!
Last edited by diginagain; 25th Mar 2014 at 18:53.
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Got a couple of hours on '917 just trying to sort out an intermittent vibe, think it turned out to be the (badly fitted) LH armoured seat touching the centre console! gave the engineers plenty of practice taking the nose wheel assembly out and putting it back though. Now there was an aircraft that kids could fly.......happy days.
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Now there was an aircraft that kids could fly.......happy days.
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JimL:"Just to correct the basis of the statistics: the figure for engine failures (power plant, not core failures) comes out consistently at 1:100,000/flying hour. The probability of failure of an engine in a single is therefore 1 x 10**-5; the probability of an engine failure in a twin (one or the other) is 2 x 10**-5; and the probability of two failures in a twin (from unconnected causes - i.e. one and then the other) is 2 x 10**-5 and (times) 1 x 10**-5 - that is 2 x 10**-10"
Jim you are absoloutly right that that is the basis used BUT Jim this is arithmetic nonsense, it is faulty maths, incorrect and wrong:
This is why:
The 1:100,000 is per flying hour . So the result you have calculated is the chance of both engines failing within an hour of flight. So to get the chance of the second failing within the subsequent 10 seconds (say) you have to divide by another 360, making the chance of this occuring about 5^10-13. That is once per 50,000,000,000,000 hours (that's once per 50 thousand billion hours !!). Since the chance of losing 2 engines within 10 seconds has happened at least 10,000,000 times more frequently than that there must be something wrong with some other assumption in your statement. The only thing that is likely to be is the (ridiculous) assumption that the systems are independant.
What you say is of course true(ish) if (as you say clearly) we assume (wrongly btw) that the engines are independant.
1 There are many reasons why the engines are not independant:
They share a common drive chain.
They have the same pilot (trying) to control them.
They share fuel system components.
They share common fuel (impurities, wrong grade etc)
Theyt are located near eachother (so they would have to theoretically never interfere?)
The engine controls look alike and are located in a similar place.
They have had a similar history having flown together for possible all of their life.
They consume the same air (or water, snow, ice, flame, dust, chemical or volcanic ash!)
They are both maybe fixed by the same engineer (who puts the wrong oil in both etc etc)
The second engine is expected to do more than it has ever done before and operate to new maxima, which are previously untested (for that engine).
Same electronic control components subject to RadHaz, software problems.
The heat seeking missile (which might have an easier job!) doesn't know it is 'only suppose to blow the bloody' port engine.
2 And not to be ignored there are other factors where the risk is increased:
Reduced margins of other critical components.
Increased risk from engine explosion/fire.
Increased system risk from increased complexity gearbox. (More critical cogs, and bearings)
Higher risk from freewheel unit faults.
Complexity causing more pilot confusion and more scope for error.
3 Not to mention that to shift the same payload the reduced payload of a twin may result in more trips (exposures) being required.
If the capacity reduction in the NS required twice the number of trips we might expect twice the number of accidents, all else being equal.
People are totally screwed in their use and understanding of statistics: If you increase a risk in the 10^-6 realm in order to improve a risk in the 10^-9 realm then you've shot yourself in the foot (maybe a thousand times!).
(Incorrect) Theory doesn't deliver, that's why legislators should not design soloutions, design engineers should.
There were no losses asociated with banning onshore SE helicopter PT at night. Just unfounded instinct.
The loss rate (of night twins, not neccessarily PT) has been pretty high since.
Jim you are absoloutly right that that is the basis used BUT Jim this is arithmetic nonsense, it is faulty maths, incorrect and wrong:
This is why:
The 1:100,000 is per flying hour . So the result you have calculated is the chance of both engines failing within an hour of flight. So to get the chance of the second failing within the subsequent 10 seconds (say) you have to divide by another 360, making the chance of this occuring about 5^10-13. That is once per 50,000,000,000,000 hours (that's once per 50 thousand billion hours !!). Since the chance of losing 2 engines within 10 seconds has happened at least 10,000,000 times more frequently than that there must be something wrong with some other assumption in your statement. The only thing that is likely to be is the (ridiculous) assumption that the systems are independant.
What you say is of course true(ish) if (as you say clearly) we assume (wrongly btw) that the engines are independant.
1 There are many reasons why the engines are not independant:
They share a common drive chain.
They have the same pilot (trying) to control them.
They share fuel system components.
They share common fuel (impurities, wrong grade etc)
Theyt are located near eachother (so they would have to theoretically never interfere?)
The engine controls look alike and are located in a similar place.
They have had a similar history having flown together for possible all of their life.
They consume the same air (or water, snow, ice, flame, dust, chemical or volcanic ash!)
They are both maybe fixed by the same engineer (who puts the wrong oil in both etc etc)
The second engine is expected to do more than it has ever done before and operate to new maxima, which are previously untested (for that engine).
Same electronic control components subject to RadHaz, software problems.
The heat seeking missile (which might have an easier job!) doesn't know it is 'only suppose to blow the bloody' port engine.
2 And not to be ignored there are other factors where the risk is increased:
Reduced margins of other critical components.
Increased risk from engine explosion/fire.
Increased system risk from increased complexity gearbox. (More critical cogs, and bearings)
Higher risk from freewheel unit faults.
Complexity causing more pilot confusion and more scope for error.
3 Not to mention that to shift the same payload the reduced payload of a twin may result in more trips (exposures) being required.
If the capacity reduction in the NS required twice the number of trips we might expect twice the number of accidents, all else being equal.
People are totally screwed in their use and understanding of statistics: If you increase a risk in the 10^-6 realm in order to improve a risk in the 10^-9 realm then you've shot yourself in the foot (maybe a thousand times!).
(Incorrect) Theory doesn't deliver, that's why legislators should not design soloutions, design engineers should.
There were no losses asociated with banning onshore SE helicopter PT at night. Just unfounded instinct.
The loss rate (of night twins, not neccessarily PT) has been pretty high since.
Last edited by AnFI; 25th Mar 2014 at 22:58. Reason: error correction and missed missile, add reason
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AnFI. Genuinely just trying to understand.
Like a single?
Like a single?
Partly.
Like a single?
'Near'? You mean in the same aircraft? ''Never' interfere? Really?
Which is why pilots require rigid adherence to high quality training?
Sometimes?
Like a single?
Sometimes? Like a single?
Previously 'untested'? Are you sure?
Like a single?
Easier job? Not sure you are entirely conversant with the way IR missiles work? Any helicopter struck by an IR missile, probably has more to worry about than power!!!
You keep banging on about increased risk from gearbox complexity. Please can you share that data with us?
I'm happy with the quality of my training, and much prefer my chances of shutting down the correct engine than landing in a congested area at night having lost my ONE engine!
Last military helicopter (a civil version currently exists!) I flew had a PAYLOAD of 12 tonnes! Which singles can carry that in fewer trips?
'High' in comparison with what? How many night hours are flown in twins in comparison with the number of night hours flown in singles??
There is indeed someone here with a closed mind. I can't be at all sure it's me! But please do keep trying to convince me!
They share a common drive chain.
They have the same pilot (trying) to control them.
They share fuel system components.
They share common fuel (impurities, wrong grade etc)
Theyt are located near eachother (so they would have to theoretically never interfere?)
The engine controls look alike and are located in a similar place
They have had a similar history having flown together for possible all of their life.
They consume the same air (or water, snow, ice, flame, dust, chemical or volcanic ash!)
They are both maybe fixed by the same engineer (who puts the wrong oil in both etc etc)
The second engine is expected to do more than it has ever done before and operate to new maxima, which are previously untested (for that engine).
Same electronic control components subject to RadHaz, software problems.
The heat seeking missile (which might have an easier job!) doesn't know it is 'only suppose to blow the bloody' port engine.
You keep banging on about increased risk from gearbox complexity. Please can you share that data with us?
Complexity causing more pilot confusion and more scope for error.
3 Not to mention that to shift the same payload the reduced payload of a twin may result in more trips (exposures) being required.
The loss rate (of night twins, not neccessarily PT) has been pretty high since.
There is indeed someone here with a closed mind. I can't be at all sure it's me! But please do keep trying to convince me!
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Tandem, well you are trying to understand, good, I agree with your "like a single" comments BUT it is supposed not to be the case in order for the twin maths to work. They are supposed to be independent. They are all factors which demonstrate that 2 engines are not 2 independent engines. You are agreeing that the assumptions for the maths upon which the rules are based is wrong. Thanks for putting in the time.
"You keep banging on about increased risk from gearbox complexity. Please can you share that data with us?" Where have you been? How many recent major events have been gearbox related? Major fatal accidents from complex gearbox failures are part of the twin downside. Newfoundland, Northsea, Thruxton, statistically significant.
A combiner gearbox (where relevant) is an additional system upon which the delivery from engines is depenent, no singles have combiner gearboxes.
... but really I am not against the twin (as I keep saying) we just must not be deluded. Some people think that flying a single is an emergency condition !!
Horses for courses - but banning single from urban areas is absurd since it has been the twins breaking tiles!
Remeber the BlackHawk crash due one engine failing up the mountain?
When you carry 12 tons are you needing both engines? If so theoretically better in a single. (not that there are any at that scale, agree)
Scale: Large scale suits the twin where the marginal increase in weight can be worth the penalty esp if the twin were less able to perform an EOL (as they seem to be).
"You keep banging on about increased risk from gearbox complexity. Please can you share that data with us?" Where have you been? How many recent major events have been gearbox related? Major fatal accidents from complex gearbox failures are part of the twin downside. Newfoundland, Northsea, Thruxton, statistically significant.
A combiner gearbox (where relevant) is an additional system upon which the delivery from engines is depenent, no singles have combiner gearboxes.
... but really I am not against the twin (as I keep saying) we just must not be deluded. Some people think that flying a single is an emergency condition !!
Horses for courses - but banning single from urban areas is absurd since it has been the twins breaking tiles!
Remeber the BlackHawk crash due one engine failing up the mountain?
When you carry 12 tons are you needing both engines? If so theoretically better in a single. (not that there are any at that scale, agree)
Scale: Large scale suits the twin where the marginal increase in weight can be worth the penalty esp if the twin were less able to perform an EOL (as they seem to be).
Last edited by AnFI; 26th Mar 2014 at 00:24.
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AnFI
I'm obviously not against twins either! Though I confess I felt FAR more comfortable when I flew the two aircraft on my licence with four engines!
Nor do I think flying an aircraft on one engine (when I took off with two!) is a major drama. But flying an aircraft on none makes it (at best!) a glider, and I've never been qualified on those!
But if singles are banned (or required to land clear of the congested area) then they could never form part of the statistics could they?? I know of a twin squirrel that had a tail rotor failure and landed on a house roof. Also the 'pilot error' 109 in London, though I don't know whether a single could have suffered precisely the same fate? Plus the recent EC135, cause not yet determined. But I also know of a Strathclyde B206 that struck a block of flats, so where does that lead us? Conversely I am aware of a number of twins that have suffered engine failures and happily diverted away from the congested area?
I prefer to fly twins (when I'm not flying a quad!) because I'm confident my training will help mitigate any 'confusion' the additional 'complexity' may bring. I accept others may not be so fortunate. In the right hands, two engines offer an additional layer of safety.
Please convince me otherwise?
... but really I am not against the twin (as I keep saying) we just must not be deluded. Some people think that flying a single is an emergency condition !!
Horses for courses - but banning single from urban areas is absurd since it has been the twins breaking tiles!
Horses for courses - but banning single from urban areas is absurd since it has been the twins breaking tiles!
Nor do I think flying an aircraft on one engine (when I took off with two!) is a major drama. But flying an aircraft on none makes it (at best!) a glider, and I've never been qualified on those!
banning single from urban areas is absurd since it has been the twins breaking tiles!
I prefer to fly twins (when I'm not flying a quad!) because I'm confident my training will help mitigate any 'confusion' the additional 'complexity' may bring. I accept others may not be so fortunate. In the right hands, two engines offer an additional layer of safety.
Please convince me otherwise?
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if they were banned (unjustifiably) then they would no longer supply the data which they are currently supplying that there is not an issue when they do have to land in urban areas. They do not (and should not) be required to land clear (like aeroplanes are) merely they should land safely like the statistically significant examples have demonstrated. (we have had about six good examples, from hawaii, to San Antonio, to London, Sao Paulo etc)
Feeling safer in a twin is one of the reasons for there existance, but not supported by fact.
Feeling safer in a twin is one of the reasons for there existance, but not supported by fact.
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AnFI
Reading your recent posts is interesting. You have clearly gone to a lot of thought to consider why a second engine failure rate in twins might be higher that it statistically should be. But if you were balanced in your views, would you not have mentioned that the failure rate of even one engine on a twin might be less than for a single because in twins they generally run at a lower % of maximum power and therefore are under less stress?
What are your thoughts on the probability of a first engine failure in a twin vs a single?
For now let's assume it's not greater. Then maybe other Ppruners can let us know of any personal experiences; (1) how many have experienced an engine failure on a twin that has resulted in a safe undamaged landing on the second engine, and (2) how many have experienced an engine failure on a twin that has been followed by the failure of the other engine? Now clearly the Glasgow 135 falls into (2). I suspect most incidents of (2) result in a well publicised serious accident whereas most of (1) go unknown as they are unremarkable.
Reading your recent posts is interesting. You have clearly gone to a lot of thought to consider why a second engine failure rate in twins might be higher that it statistically should be. But if you were balanced in your views, would you not have mentioned that the failure rate of even one engine on a twin might be less than for a single because in twins they generally run at a lower % of maximum power and therefore are under less stress?
What are your thoughts on the probability of a first engine failure in a twin vs a single?
For now let's assume it's not greater. Then maybe other Ppruners can let us know of any personal experiences; (1) how many have experienced an engine failure on a twin that has resulted in a safe undamaged landing on the second engine, and (2) how many have experienced an engine failure on a twin that has been followed by the failure of the other engine? Now clearly the Glasgow 135 falls into (2). I suspect most incidents of (2) result in a well publicised serious accident whereas most of (1) go unknown as they are unremarkable.
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In the UK, Police and AA are carried out in twin engine aircraft, the end.
So lets look at statistics........ I am extremely alarmed here.......... ALL the accidents and incidents with police and AA seem to be on twin engine aircraft!! I cant find one single accident with a single. Therefore, single engine helicopters must be safer.
Next, engine shutdowns and transits clear of congested areas are not reported as accidents. The newspapers don't report them and, more importantly, customers don't stop using helicopters because of negative publicity. How many times have I been asked, "you're a helicopter pilot? Arent they really dangerous?"
The fact is that you can spout your guff all day and twist statistics like a Labour MP, but I will choose a well trained crew in a twin over a well trained crew in a single EVERY time.
The End again.........
So lets look at statistics........ I am extremely alarmed here.......... ALL the accidents and incidents with police and AA seem to be on twin engine aircraft!! I cant find one single accident with a single. Therefore, single engine helicopters must be safer.
Next, engine shutdowns and transits clear of congested areas are not reported as accidents. The newspapers don't report them and, more importantly, customers don't stop using helicopters because of negative publicity. How many times have I been asked, "you're a helicopter pilot? Arent they really dangerous?"
The fact is that you can spout your guff all day and twist statistics like a Labour MP, but I will choose a well trained crew in a twin over a well trained crew in a single EVERY time.
The End again.........
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AnFI
I believe it may have been Thomas Coupling who provided this:
So it seems to me you need to be lobbying ICAO with your theory. I believe you can contact them here:
ICAO Headquarters
999 University Street
Montréal
Quebec
H3C 5H7
Canada
Because you are making absolutely no headway whatsoever with the very many professionals here. They are the people who in stark contrast to you are very happy to state that they have both seen it and done (do) it! We seem to find your argument, (unsupported by any peer reviewed research!) utterly unconvincing.
Not at all sure there is anything else to say. To continue this is just going round and round in circles.
if they were banned (unjustifiably) then they would no longer supply the data which they are currently supplying that there is not an issue when they do have to land in urban areas. They do not (and should not) be required to land clear (like aeroplanes are) merely they should land safely like the statistically significant examples have demonstrated. (we have had about six good examples, from hawaii, to San Antonio, to London, Sao Paulo etc)
There is no twin-only mentality; the restriction on flights over a hostile environment (and specifically a congested hostile environment) arises from compliance with the ICAO Annexes - you know, the Chicago Convention to which all States agree to comply:
Specifically:
ICAO Annex 2 - Rules of the Air; and Annex 6 - Operation of Aircraft.
Respectively, the need to 'land clear' (protection of third parties) and the requirement for a 'safe-forced-landing' (protection of crew and passengers).
There is also linkage to the the certification principle that no hazardous outcome should be permitted with an event which has a classification of 'Reasonably Probable' (which is based upon a probability on the order of between 1:1,000 and 1:100,000). Because engines tend to fail within that probability spectrum, ICAO SARPs attempt to keep the helicopter away from an area where the effect of the failure could be hazardous.
Specifically:
ICAO Annex 2 - Rules of the Air; and Annex 6 - Operation of Aircraft.
Respectively, the need to 'land clear' (protection of third parties) and the requirement for a 'safe-forced-landing' (protection of crew and passengers).
There is also linkage to the the certification principle that no hazardous outcome should be permitted with an event which has a classification of 'Reasonably Probable' (which is based upon a probability on the order of between 1:1,000 and 1:100,000). Because engines tend to fail within that probability spectrum, ICAO SARPs attempt to keep the helicopter away from an area where the effect of the failure could be hazardous.
ICAO Headquarters
999 University Street
Montréal
Quebec
H3C 5H7
Canada
Because you are making absolutely no headway whatsoever with the very many professionals here. They are the people who in stark contrast to you are very happy to state that they have both seen it and done (do) it! We seem to find your argument, (unsupported by any peer reviewed research!) utterly unconvincing.
Not at all sure there is anything else to say. To continue this is just going round and round in circles.
