Where does the UK/JAR "twin only" mentality come from?
A couple of rather spurious arguments here I think -
Nick - I doubt that "the vast majority of ppruners (esp those from the correct side of the pond) are aghast that the current crop of twins cannot hover on one engine. "
As I expect you know, twin-engine operations under JAR rules are not predicated on being able to hover on one engine, but on (for Performance Class1)
"performance such that, in case of critical
power unit failure, it is able to land on the rejected take-off area or safely
continue the flight to an appropriate landing area, depending on when
the failure occurs"
And Robbo Jock - In saying
"I find it a little strange that certification authorities seem perfectly happy (under ETOPS-180) to allow hundreds of passenger to be flown for up to three hours on one engine over hostile terrain or oceans, yet have the screaming heebie-jeebies over flying a fare-paying passenger in a single-engine helicopter into a field in a 'congested area'."
-you seem to miss the point that one case is AFTER the highly statistically unlikely engine failure, and the other is BEFORE.
Nick - I doubt that "the vast majority of ppruners (esp those from the correct side of the pond) are aghast that the current crop of twins cannot hover on one engine. "
As I expect you know, twin-engine operations under JAR rules are not predicated on being able to hover on one engine, but on (for Performance Class1)
"performance such that, in case of critical
power unit failure, it is able to land on the rejected take-off area or safely
continue the flight to an appropriate landing area, depending on when
the failure occurs"
And Robbo Jock - In saying
"I find it a little strange that certification authorities seem perfectly happy (under ETOPS-180) to allow hundreds of passenger to be flown for up to three hours on one engine over hostile terrain or oceans, yet have the screaming heebie-jeebies over flying a fare-paying passenger in a single-engine helicopter into a field in a 'congested area'."
-you seem to miss the point that one case is AFTER the highly statistically unlikely engine failure, and the other is BEFORE.
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farsouth, you don't know what you are saying, the results of two threads I have started here on pprune to debate the subject of how much Cat A was enough ended up in routs, with the need for hover - to - hover Cat A as the dominant position of UK ppruners, even considering the inherent loss of range and payload. That tells me that the idea of venturing out in a single would make most UK ppruners shiver in their shoes. Any single engine helo advocate need not search pprune for consolation.
I stand by my position.
And you don't have to post FAR/JAR for me, I was flying Cat A test flights when most ppruners were busy figuring out how shoe laces worked.
BTW, you are also quite wrong about the FAR/JAR interpretation of engine failure probability, robbo jock is correct. The CAA accepts the failure rate in an ETOPS airliner that they won't accept in a helo. The probability of a turbine engine failure for engine cause in a single is approximately two to five times less likely than the probability that the pilot will fly into terrain while the engine is running very nicely.
I stand by my position.
And you don't have to post FAR/JAR for me, I was flying Cat A test flights when most ppruners were busy figuring out how shoe laces worked.
BTW, you are also quite wrong about the FAR/JAR interpretation of engine failure probability, robbo jock is correct. The CAA accepts the failure rate in an ETOPS airliner that they won't accept in a helo. The probability of a turbine engine failure for engine cause in a single is approximately two to five times less likely than the probability that the pilot will fly into terrain while the engine is running very nicely.
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Nick
You say: "The CAA accepts the failure rate in an ETOPS airliner that they won't accept in a helo."
Interesting comment. Can you lay out the facts you working from in making that statement please?
Robbo Jock: Remember that twin airliners are trying to fly the Atlantic etc on two engines. A rare emergency diversion on one is not the same as flying on one all the time!
You say: "The CAA accepts the failure rate in an ETOPS airliner that they won't accept in a helo."
Interesting comment. Can you lay out the facts you working from in making that statement please?
Robbo Jock: Remember that twin airliners are trying to fly the Atlantic etc on two engines. A rare emergency diversion on one is not the same as flying on one all the time!
Any mention of ETOPS in this discussion is surely just a red herring. I would've thought that 'ETOPS' is an argument for, rather than against, twin engine heli operations.
I'm sure that on a technical level, Boeing/Airbus could design and produce single engine airliners. (A Trent 1000 strapped to a 737 airframe should probably produce sufficient thrust.) Will they though? Of course not. Because they want power unit redundancy.
Which, surely, is the same reason why the CAA/JAA insist on twin engines for certain operations or environments...
I'm sure that on a technical level, Boeing/Airbus could design and produce single engine airliners. (A Trent 1000 strapped to a 737 airframe should probably produce sufficient thrust.) Will they though? Of course not. Because they want power unit redundancy.
Which, surely, is the same reason why the CAA/JAA insist on twin engines for certain operations or environments...
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zalt,
I think the comparison is valid. The ETOPS is based on the probability of the second engine failing, after the first one is presumed to have failed with a probability of one (in other words, the flight is 180 minutes of single engine flight, with passengers, and it is presumed that this happens on any flight.) The probability of the one engine failing (the second) is about the same for turbines, so it logically follows that an ETOPS airliner is allowed to operate where a single engine helo is not.
I certainly agree that the double probability (first one then the second) is an enormous number, but that is not how the ETOPS flight path is determined. Also, I do believe that enroute Cat A or limited exposure window calculations are a brilliant way to balance OEI safety levels to the safety of the rest of the aircraft, and I do believe that passengers expect and require those levels. Zero exposure aircraft trade too much payload, cost to maintain and fuel costs to make the "extra" safety of zero exposure Cat A worthwhile.
manfromuncle, thanks - I must admit, shoelaces are complex, I always wore zipper flight boots because if I took a long lunch, I had to be retrained.
I think the comparison is valid. The ETOPS is based on the probability of the second engine failing, after the first one is presumed to have failed with a probability of one (in other words, the flight is 180 minutes of single engine flight, with passengers, and it is presumed that this happens on any flight.) The probability of the one engine failing (the second) is about the same for turbines, so it logically follows that an ETOPS airliner is allowed to operate where a single engine helo is not.
I certainly agree that the double probability (first one then the second) is an enormous number, but that is not how the ETOPS flight path is determined. Also, I do believe that enroute Cat A or limited exposure window calculations are a brilliant way to balance OEI safety levels to the safety of the rest of the aircraft, and I do believe that passengers expect and require those levels. Zero exposure aircraft trade too much payload, cost to maintain and fuel costs to make the "extra" safety of zero exposure Cat A worthwhile.
manfromuncle, thanks - I must admit, shoelaces are complex, I always wore zipper flight boots because if I took a long lunch, I had to be retrained.
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In response to Man from Uncle`s original post, it should not be overlooked that , right from the inception of the JAA concept, the CAA has been falling over itself to be the front runner in the formulation of policy and implementation of legislation, much of it unnecessarily restrictive and unhelpful. From the late 1980`s and early 1990`s members of the CAA , with JimL well to the fore, were proposing policy documents which now form the basis of much of the quagmire that has been adopted as JAR Ops and trying to convince other national authorities within Europe that the CAA`s was the correct and only view of the future. The bullying and threatening tactics that were adopted by Flight Ops over the questions of UK AOC applications and the direction of UK aviation lend weight to the assumption that a junta within the hallowed halls of Gatwick opted for the morass that is now JAA and vowed to force it through at all costs, with JimL working many of the strings.
So, in a nutshell, yes it was the CAA pure and simple and if you ever come across someone who boasts he was part of that process, feel free to poke him in the eye!
So, in a nutshell, yes it was the CAA pure and simple and if you ever come across someone who boasts he was part of that process, feel free to poke him in the eye!
I have just completed 7 years with a major airline and with eight night stopping aircraft we changed one engine (due to a birdstike) in that time.
Having returned to rotary I have been involved in 4 engine changes for mechanical reasons in 5 months, albeit none requiring an inflight shutdown.
In the past I have seen several helicopters return to base single engined from offshore. If singles they would all have gone for a swim.
One case was a 365C which not only suffered an engine failure just after takeoff from a rig but the second engine failed to wind up to 100% due to a dormant FCU problem. It was impossible to hover.
The pilot (John Carrol) went on to make a rather exciting run on landing at North Denes.
I also remember two cases of engine failure, a BO 105 and a 365c that made offshore helideck landings after an engine failure, again both candidates for a swim.
The reliability of the smaller harder working helicopter engines is a factor and comparisons with fixed wing are a bit apple and pears.
Having returned to rotary I have been involved in 4 engine changes for mechanical reasons in 5 months, albeit none requiring an inflight shutdown.
In the past I have seen several helicopters return to base single engined from offshore. If singles they would all have gone for a swim.
One case was a 365C which not only suffered an engine failure just after takeoff from a rig but the second engine failed to wind up to 100% due to a dormant FCU problem. It was impossible to hover.
The pilot (John Carrol) went on to make a rather exciting run on landing at North Denes.
I also remember two cases of engine failure, a BO 105 and a 365c that made offshore helideck landings after an engine failure, again both candidates for a swim.
The reliability of the smaller harder working helicopter engines is a factor and comparisons with fixed wing are a bit apple and pears.
The original post on this is misleading and ill-informed. In the UK there is no restriction over congested areas - all helicopters must fly in accordance with rule 5 at 1000ft above the nearest highest object within 600m. Single, twin or triple.
Police have exceptions to that - and it is they who mandate twins. This policy deprives many areas of the UK from the taxpayer-funded benefit of police helicopters.
There is a restriction on CAT landing sites for singles - purely take-off distance related. This needs addressing because it appears to apply random outdated data to some singles.
And there is a restriction on SEH (and SEP) CAT at night.
Other than the ridiculous outdated "floats on singles" for ops through London, that's about it.
Yes - twins can get better Rule 5 exemptions. But the vast majority of CAT and private work onshore can be done by singles.
Doesn't please the twin operators. And doesn't fit into the brain of an ex-mil CAA regulator who's been taught that twins are safer.
Any SEH restrictive regulations are way overdue for examination - they are based on data that is some 40 years old.
Police have exceptions to that - and it is they who mandate twins. This policy deprives many areas of the UK from the taxpayer-funded benefit of police helicopters.
There is a restriction on CAT landing sites for singles - purely take-off distance related. This needs addressing because it appears to apply random outdated data to some singles.
And there is a restriction on SEH (and SEP) CAT at night.
Other than the ridiculous outdated "floats on singles" for ops through London, that's about it.
Yes - twins can get better Rule 5 exemptions. But the vast majority of CAT and private work onshore can be done by singles.
Doesn't please the twin operators. And doesn't fit into the brain of an ex-mil CAA regulator who's been taught that twins are safer.
Any SEH restrictive regulations are way overdue for examination - they are based on data that is some 40 years old.
Tightgit
Police have exceptions to that - and it is they who mandate twins. This policy deprives many areas of the UK from the taxpayer-funded benefit of police helicopters.
The CAA mandate that twins must be used (to take advantage of the exemptions to rule 5). Those exemptions are needed to enable the aircraft to be available as close to 24/7 as we can get, given the vagaries of our maritime climate!
Fair enough. Correction accepted. But if the CAA would allow the police to operate Aerial Work instead of CAT, then there wouldn't be a problem.
Old argument I know - but JAR OPS 3 has caught on. For instance, any flight before, during or after an aerial work flight is exempt from JAR OPS 3 and can carry up to six people in addition to the crew.
The UK police and HEMS are really doing aerial work. The rules of CAT were never designed for such tasking. However, the CAA designed their own "catch-all" by insisting that any "air transport undertaking" operating aerial work must fly those flights as CAT.
So - if you have an AOC you're stuffed.
Old argument I know - but JAR OPS 3 has caught on. For instance, any flight before, during or after an aerial work flight is exempt from JAR OPS 3 and can carry up to six people in addition to the crew.
The UK police and HEMS are really doing aerial work. The rules of CAT were never designed for such tasking. However, the CAA designed their own "catch-all" by insisting that any "air transport undertaking" operating aerial work must fly those flights as CAT.
So - if you have an AOC you're stuffed.
Tightgit
Fair enough. Correction accepted. But if the CAA would allow the police to operate Aerial Work instead of CAT, then there wouldn't be a problem.
).I would also be fairly happy if we ran a fleet of capable singles rather than one twin, but that's never going to happen! (as long as we're not operating with 250s, they need to be shut down in flight too often for my liking!)
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A topic close to my heart if you read the twin heli-which one thread. There are twins out there with a significant increase in safety, but it requires compromises on range and payload not always justified if altitude and temperature comes into play. Do we compromise missions for twins in the hope that the second engine will one day safe our butts or do we take the more controversial route of selecting a B3/B4 or even 407 depending on your preference? We just selected the B4 instead of a light twin due to altitude and temps and will test it at worse case scenarios for a 3 month period. According to the graphs it out performs it's twin mates greatly and it is only the B3 beating it in "safety margin" during power margin available in the take off/landing phase. Given, if the engine fails the power margin will not help, but if we do not require max N1/T4/5 every take off, preventative maintenance can go a long way on a already reliable Arriel 2 with 3 control systems? The B4 bought already operated it's young life as a VIP machine at 6500ft, 32-36 degrees C at one of the bases listed in the twin thread.
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ericferret
Here's a bit of offshore twins vs singles reading http://www.ogp.org.uk/pubs/300.pdf
It's only a snap shot for 1 year but it is worldwide
Of the 47 fatalities worldwide the figures were :
57% in medium twins
21% in light twins
17% in singles (none due to engine failure ??)
4% heavy twins.
Here's a bit of offshore twins vs singles reading http://www.ogp.org.uk/pubs/300.pdf
It's only a snap shot for 1 year but it is worldwide
Of the 47 fatalities worldwide the figures were :
57% in medium twins
21% in light twins
17% in singles (none due to engine failure ??)
4% heavy twins.
Handysnaks says : We would still need an exemtion from rule 5 and I feel sure it would only be issued for twin engine aircraft.
Why ? The latest HiDef cameras with long lenses, superscopes and IR can deliver their best work from 1500ft. What reason is there to go lower ?
A Met EC145 was in our neighbourhood this week and the only reason they needed to be low was to use their NiteSun to illuminate the ground for plods. In an area that has adequate street lights.
If the police could all use big lenses and sensitive equipment, they could stay higher and annoy less people. And they would get their live signals to travel further. Operating at 500ft and less in a congested area must compromise the microwave link.
Why ? The latest HiDef cameras with long lenses, superscopes and IR can deliver their best work from 1500ft. What reason is there to go lower ?
A Met EC145 was in our neighbourhood this week and the only reason they needed to be low was to use their NiteSun to illuminate the ground for plods. In an area that has adequate street lights.
If the police could all use big lenses and sensitive equipment, they could stay higher and annoy less people. And they would get their live signals to travel further. Operating at 500ft and less in a congested area must compromise the microwave link.
Purveyor of Egg Liqueur to Lucifer
A Met EC145 was in our neighbourhood this week and the only reason they needed to be low was to use their NiteSun to illuminate the ground for plods. In an area that has adequate street lights.
Only 6 months ago I asked the local council to put a shield on the lampost outside my house because of the light coming onto my property that I did not want. (which they did within 5 days!)
If it wasn't for people like me, Police units wouldn't have to spend thousands of tax payers pounds on silly nightsuns to find crims hiding in the shadows or other dark areas...street lighting is great for finding hidden crims!
Perhaps there could be a system, where in an area the local rozzers are looking for someone hiding in back gardens or in sheds, under trampolines or even in the dark alleyways, they could just turn up the intensity of the street lights!
Problems and money solved all round and no need to wake everyone up in the silly hours with a twin engined throbbing helichopter overhead!
I would have thought though, that with such an advanced machine, the Met could have been higher and on narrower beam!
What reason is there to go lower ?
In addition, it gets more eyes on the ground!!
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2leftskids
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99%
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In a year when 49% (23) of fatalities were caused by mid airs, this data doesn't really, IMHO, apply here.
Interesting to read Appendix C
If you like to throw figures around, notice the singles accident rates compared to all the twins put together!!!
Here's a bit of offshore twins vs singles reading http://www.ogp.org.uk/pubs/300.pdf
It's only a snap shot for 1 year but it is worldwide
Of the 47 fatalities worldwide the figures were :
57% in medium twins
21% in light twins
17% in singles (none due to engine failure ??)
4% heavy twins.
It's only a snap shot for 1 year but it is worldwide
Of the 47 fatalities worldwide the figures were :
57% in medium twins
21% in light twins
17% in singles (none due to engine failure ??)
4% heavy twins.
99%
----
In a year when 49% (23) of fatalities were caused by mid airs, this data doesn't really, IMHO, apply here.
Interesting to read Appendix C
If you like to throw figures around, notice the singles accident rates compared to all the twins put together!!!
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Interesting figures. Does anybody have recent HEMS, commercial ops figures? There are a lot of "old generation" aircraft listed which in my opinion can spoil the figures. There are no argument from my side regarding new generation vs old generation(single/twin). A very important point listed earlier is the experience level of the pilot. The question remains-where does a pilot gain sufficient experience in a good safety environment?
Regarding the police argument. Has any one made a comprehensive study prooving or disproofing that the current activities cut crime? That should surely settle it either way?
Regarding the police argument. Has any one made a comprehensive study prooving or disproofing that the current activities cut crime? That should surely settle it either way?
Tightgit
Handysnaks says : We would still need an exemtion from rule 5 and I feel sure it would only be issued for twin engine aircraft.
Why ? The latest HiDef cameras with long lenses, superscopes and IR can deliver their best work from 1500ft. What reason is there to go lower ?
Why ? The latest HiDef cameras with long lenses, superscopes and IR can deliver their best work from 1500ft. What reason is there to go lower ?