Where does the UK/JAR "twin only" mentality come from?
Having flown off and on since 1980 flying mainly singles until recently , now flying A109 , I don't think I have ever felt less safe in a turbine single than a twin . In the old days I was always expecting the donk to stop on my 47 G3B1 and the Hiller , but when I got onto turbines I have always looked at other things to catch me out !! Like most people I guess , I would prefer to fly long distance over water or extended time over cities , in a twin . That's just common sense to me . But for all other say " gentle" flying I think a single is every bit as safe . Just as somebody said earlier , I also agree that singles have now come of age , and should be ifr capable just like fixed wing . There is no real justification for encouraging all the single pilots to scud run when they could , if the suitable aircraft were out there , go up and be at a safe altitude ifr .
Maybe fixed wing pilots are inherently more clever than us .... They have managed an IMC system that has virtually eliminated all cfit accidents whilst we make zero progress and continue to send ill trained pilots out knowing that they will get perilously close , if not actually in , IIMC ..... With maybe an hour or two under a hood !!!
Maybe fixed wing pilots are inherently more clever than us .... They have managed an IMC system that has virtually eliminated all cfit accidents whilst we make zero progress and continue to send ill trained pilots out knowing that they will get perilously close , if not actually in , IIMC ..... With maybe an hour or two under a hood !!!
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lynx-effect:
Then I guess you didn't read the title?
"Where does the UK/JAR "twin only" mentality come from?"
As has been frequently stated, the answer being from the annexes to the ICAO 'Chicago Convention."
The Montreal address for ICAO is provided earlier in the thread. Please do tell us how you get on.
nigelh
Of course some contributing here are BOTH fixed and rotary wing ATPLs! Myself included. Does that make us stupid, clever, or somewhere in between? It certainly gives an insight, and arguably a valid opinion?
Your point about ill-trained pilots is very well made, and likely quite telling in the accident stats.
Twins offer an additional layer of safety. How significant a layer that is depends on the type of accident you are intending to have.
I can only wish fixed wing pilots had done as you say, and eliminated CFIT! It's a popular misconception that CFIT always involves impacting rising ground. It most certainly does not. Try looking at the number of FW that crash short of the runway. That's CFIT too!, and sadly accounts for the overwhelming majority of CFIT incidents!
I thought that this thread was about discussing why the CAA think that twin engine ops are safer than single.
"Where does the UK/JAR "twin only" mentality come from?"
As has been frequently stated, the answer being from the annexes to the ICAO 'Chicago Convention."
The Montreal address for ICAO is provided earlier in the thread. Please do tell us how you get on.
nigelh
Maybe fixed wing pilots are inherently more clever than us
Your point about ill-trained pilots is very well made, and likely quite telling in the accident stats.
Twins offer an additional layer of safety. How significant a layer that is depends on the type of accident you are intending to have.
I can only wish fixed wing pilots had done as you say, and eliminated CFIT! It's a popular misconception that CFIT always involves impacting rising ground. It most certainly does not. Try looking at the number of FW that crash short of the runway. That's CFIT too!, and sadly accounts for the overwhelming majority of CFIT incidents!
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There is no real justification for encouraging all the single pilots to scud run when they could , if the suitable aircraft were out there , go up and be at a safe altitude ifr .
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Well at least it is now accepted that the maths used to justify the twin concept is false, unchallenged because it is demonstrably rubbish. That is progress.
The next thing to be understood is that (obviously) there will be less enroute engine failure forced landings in the twin, but it must be weighed up against all the other (previously itemised) consequential accidents and the degree of accident that might result. (GBoxes, fuel systems etc etc etc)
There is no valid statistical case against the single when all factors are considered.
This is not to say there are not merits to the twin - just like the different types are better suited to different tasks.
Shyt I didn't mean to ignore your 2 engine failures (statistically amazing!) in twins during the reversing climb process before TDP. I would genuinely love to know the details. ?
The old Allison used to have a failure rate of something like 1 per 400 hours in the early days, it would not be suprising for that to cause people to feel a big attraction to the twin. The Scout used to have an absurd engine failure rate, but the Gazelle and the 1B1 really don't fail enough to justify the downsides of the twin. The weight spent on spare engines might be better spent having bigger power, tail rotor, fuel and other critical component margins
One factor, hard to pin down, is the proportion of time flown when 'exposed'. If the exposure time is only 10% of the flight time it may well work out to be not worhtwhile to have a twin, whereas if the proportion of time 'exposed' is 99% of the time it may be worth the other accidents. It would be worth having a handle on what reliability related to what %age of exposure time. It is most certainly not 'all or nothing'.
Thanks for the support or respect, from the fair minded, for some of my points.
The next thing to be understood is that (obviously) there will be less enroute engine failure forced landings in the twin, but it must be weighed up against all the other (previously itemised) consequential accidents and the degree of accident that might result. (GBoxes, fuel systems etc etc etc)
There is no valid statistical case against the single when all factors are considered.
This is not to say there are not merits to the twin - just like the different types are better suited to different tasks.
Shyt I didn't mean to ignore your 2 engine failures (statistically amazing!) in twins during the reversing climb process before TDP. I would genuinely love to know the details. ?
The old Allison used to have a failure rate of something like 1 per 400 hours in the early days, it would not be suprising for that to cause people to feel a big attraction to the twin. The Scout used to have an absurd engine failure rate, but the Gazelle and the 1B1 really don't fail enough to justify the downsides of the twin. The weight spent on spare engines might be better spent having bigger power, tail rotor, fuel and other critical component margins
One factor, hard to pin down, is the proportion of time flown when 'exposed'. If the exposure time is only 10% of the flight time it may well work out to be not worhtwhile to have a twin, whereas if the proportion of time 'exposed' is 99% of the time it may be worth the other accidents. It would be worth having a handle on what reliability related to what %age of exposure time. It is most certainly not 'all or nothing'.
Thanks for the support or respect, from the fair minded, for some of my points.
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FWIW, I fly offshore, so 99% of the time over hostile territory. Give me twins every time. I have not yet had an inflight shutdown, but have had the chip warning come on over the water in IMC and it is a very calming effect to know there is a second donk running independently.
I'm sure a case could be made to allow more SE, then again a case could and should be made for proper training all around, including twins. That would drastically reduce the accident rate in my not so humble opinion.
I'm sure a case could be made to allow more SE, then again a case could and should be made for proper training all around, including twins. That would drastically reduce the accident rate in my not so humble opinion.
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well almost completely "know there is a second donk running independently"
not totally independent surely? - don't you feel slightly nervous that the second engine has slightly more chance of an 'issue' given that one engine has already had an issue?
(Worth noting that a factor of 100 turns 10^7 into 10^-5)
not totally independent surely? - don't you feel slightly nervous that the second engine has slightly more chance of an 'issue' given that one engine has already had an issue?
(Worth noting that a factor of 100 turns 10^7 into 10^-5)
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Why can you not fly IFR in a Single Engine Helicopter?
Single Engine Airplanes do it all the time.
With the advent of reliable Turbine Engines even the FAA allows Part 135 Air Taxi Operators to use Turbine Singles.
The machine doesn't care.
http://www.flyera.com/about/fleet
Single Engine Airplanes do it all the time.
With the advent of reliable Turbine Engines even the FAA allows Part 135 Air Taxi Operators to use Turbine Singles.
The machine doesn't care.
http://www.flyera.com/about/fleet
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H500 - the UK run 'Scales of Equipment' in the AirNavigationOrder - they are at variance with EASA and I don't know if that is legally correct - anyone here know?
Are singles still allowed to be IFR in the USA? (used to be ok in USA and France etc).
(a very nice French man used to fly IFR legally (I believe) in his Gazelle, he bought a 109 and killed himself in bad wx. Approx the same no. of bad wx accidents in twin IFR machines as VMC machines, it seems. Exceeding it in that sample of 1 !)
and there used to be a distiction between flying IFR and IMC but that seems to have become lost in time and confused regs. Untill about a year ago anyone could fly IFR but not IMC (or in airsp....), adding to the general confusion amongst pilots about regs.
No. of engines should not be linked to IMC/VMC
Are singles still allowed to be IFR in the USA? (used to be ok in USA and France etc).
(a very nice French man used to fly IFR legally (I believe) in his Gazelle, he bought a 109 and killed himself in bad wx. Approx the same no. of bad wx accidents in twin IFR machines as VMC machines, it seems. Exceeding it in that sample of 1 !)
and there used to be a distiction between flying IFR and IMC but that seems to have become lost in time and confused regs. Untill about a year ago anyone could fly IFR but not IMC (or in airsp....), adding to the general confusion amongst pilots about regs.
No. of engines should not be linked to IMC/VMC
Last edited by AnFI; 28th Mar 2014 at 22:29. Reason: correction
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AnFI, the details of my engine malfunctions are personal. Publishing details here would give away my identity.......
You are still trying to prove your point by comparing apples with pears. You cannot logically use the statistics of accidents totally unrelated to engine failure, such as pilot LOC, to prove one engine is safer than two. It's utterly ridiculous.
You are still trying to prove your point by comparing apples with pears. You cannot logically use the statistics of accidents totally unrelated to engine failure, such as pilot LOC, to prove one engine is safer than two. It's utterly ridiculous.
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Hughes500
Shy
what is an IFR equipped helicopter ?
Shy
what is an IFR equipped helicopter ?
Hughes500/Bob,
To fly legally in IMC a helicopter should be certificated for such flight. Requirements are contained within Appendix B of Parts 27/29 (with the mass of 3,175 kg being the boundary between them).
These appendices describe the stability, equipment and miscellaneous requirements before certification can be granted for flight on instruments. In general (with the exception of the Bell 222 - certificated to an earlier standard) the handling qualities cannot be met without the assistance of stability augmentation systems.
Because these are the minimum standard, States have operational requirements that also have to be met - these describe instruments and additional equipment for flight in IMC.
ICAO Annex 6 Part III contains additional standards for single-engine flight in IMC - these are: reliability measures for the engine; some redundancy of equipment; and, minimum flight conditions and routing - to protect the passengers and third parties. States wishing to permit such flights over their territory, should show compliance with the ICAO SARPs.
Jim
To fly legally in IMC a helicopter should be certificated for such flight. Requirements are contained within Appendix B of Parts 27/29 (with the mass of 3,175 kg being the boundary between them).
These appendices describe the stability, equipment and miscellaneous requirements before certification can be granted for flight on instruments. In general (with the exception of the Bell 222 - certificated to an earlier standard) the handling qualities cannot be met without the assistance of stability augmentation systems.
Because these are the minimum standard, States have operational requirements that also have to be met - these describe instruments and additional equipment for flight in IMC.
ICAO Annex 6 Part III contains additional standards for single-engine flight in IMC - these are: reliability measures for the engine; some redundancy of equipment; and, minimum flight conditions and routing - to protect the passengers and third parties. States wishing to permit such flights over their territory, should show compliance with the ICAO SARPs.
Jim
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Jim, Thanks for posting that.
Jim / Shy
Just playing devils advocate I seem to remember ( along time ago) flying IFR in a mil 341 with nothing more than a standby ah and alternator and a mini tans that was useless. The only autopilot was me !!
Interestingly wonder if there are any comparable figures on mil crashes in single ifr that would not have happened if there had been 2 engines and autopilot etc etc. If there were such figures it would prove/disprove the point as you could compare apples to apples .
Just playing devils advocate I seem to remember ( along time ago) flying IFR in a mil 341 with nothing more than a standby ah and alternator and a mini tans that was useless. The only autopilot was me !!
Interestingly wonder if there are any comparable figures on mil crashes in single ifr that would not have happened if there had been 2 engines and autopilot etc etc. If there were such figures it would prove/disprove the point as you could compare apples to apples .
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All those years of US Army UH-1's flying all over Germany IFR and other places. Fort Rucker, the Army Aviation School, hosts whole fleets of UH-1's and TH-57's (Bell 206's) that were dedicated to IFR training. Back in the old days, Bell TH-13T's were the workhorse (Bell 47's).
I guess the UK and Europe know better and have valid reasons for all of the requirements they laid down about routes, proving reliability of engines, etc.
For sure, the best way to keep the Accident Rate down is not to fly at all.
However did the Bristow 206 ever survive all those years doing IFR Training for hundreds of Bristow's Pilots as has been described by several Senior Bristow Pilots here.
I guess the UK and Europe know better and have valid reasons for all of the requirements they laid down about routes, proving reliability of engines, etc.
For sure, the best way to keep the Accident Rate down is not to fly at all.
However did the Bristow 206 ever survive all those years doing IFR Training for hundreds of Bristow's Pilots as has been described by several Senior Bristow Pilots here.
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H500,
We used to be required to do likewise in the Whirlwind, prior to the Gazelle, albeit with Decca rather than MiniTANS. Those stats were probably never compiled and in any case, they would not really be directly comparable to the civilian world. As a military pilot you would have been given the benefit of recurrent instrument flying training (a minimum of 12 hours per year during my time).
If civilian RW were given carte blanche to fly in IMC, logic says that inexperienced pilots would begin to suffer LOC accidents in IMC due to their inexperience and lack of training.
Also, you don't need stats to realise that an unpowered helicopter won't fly too far, hence the requirement to be required to fly over notified routes in a SE aircraft, such as the London Helilanes. Twins are allowed to fly off route, singles are not.
There has been talk of the lack of duplication of tail rotors and driveshafts. In an ideal world, everything could be duplicated, but at high cost, in more than one sense. The regulatory requirement for duplication of power plants comes from the fact that engines can fail for a whole variety of mechanical reasons, as can tail rotors, but they can also fail because of lack of fuel, lack of oil, or from FOD ingestion, icing and so on.
If you clout your tail rotor or main rotor whilst manoeuvring near the ground or obstructions, it matters not a jot how many engines you have, the result will be similar. If you run out of fuel or lose control in the air or have a CFIT because your IF skills or planning and airborne situational awareness aren't up to the job, likewise.
But having more than one engine allows more redundancy and duplication of systems by design and an extra level of safety in those respects, at least helping mitigate some risks. Which is the way aviation should be heading, not backwards as some protagonists here seem to demand, mainly out of lack of experience or common sense.
We used to be required to do likewise in the Whirlwind, prior to the Gazelle, albeit with Decca rather than MiniTANS. Those stats were probably never compiled and in any case, they would not really be directly comparable to the civilian world. As a military pilot you would have been given the benefit of recurrent instrument flying training (a minimum of 12 hours per year during my time).
If civilian RW were given carte blanche to fly in IMC, logic says that inexperienced pilots would begin to suffer LOC accidents in IMC due to their inexperience and lack of training.
Also, you don't need stats to realise that an unpowered helicopter won't fly too far, hence the requirement to be required to fly over notified routes in a SE aircraft, such as the London Helilanes. Twins are allowed to fly off route, singles are not.
There has been talk of the lack of duplication of tail rotors and driveshafts. In an ideal world, everything could be duplicated, but at high cost, in more than one sense. The regulatory requirement for duplication of power plants comes from the fact that engines can fail for a whole variety of mechanical reasons, as can tail rotors, but they can also fail because of lack of fuel, lack of oil, or from FOD ingestion, icing and so on.
If you clout your tail rotor or main rotor whilst manoeuvring near the ground or obstructions, it matters not a jot how many engines you have, the result will be similar. If you run out of fuel or lose control in the air or have a CFIT because your IF skills or planning and airborne situational awareness aren't up to the job, likewise.
But having more than one engine allows more redundancy and duplication of systems by design and an extra level of safety in those respects, at least helping mitigate some risks. Which is the way aviation should be heading, not backwards as some protagonists here seem to demand, mainly out of lack of experience or common sense.
Shy
You old git in a whirlwind !!! Wonder how many actual single engine helicopters have actually had engine failures in the last say 5 years. I believe thatb90% of all accidents are pilot error that leaves 10 %. Of this how many are the donkey stopping due to mechanical failure, not running out of fuel. Coming back to mil training ones training has diddly squat to do with has it got 1 2 or 3 engines. So comes back to how many mil ac have flown ifr that then crashed due to engine failure . I don't disagree that. 2 is better than 1 when flying over hostile environment
You old git in a whirlwind !!! Wonder how many actual single engine helicopters have actually had engine failures in the last say 5 years. I believe thatb90% of all accidents are pilot error that leaves 10 %. Of this how many are the donkey stopping due to mechanical failure, not running out of fuel. Coming back to mil training ones training has diddly squat to do with has it got 1 2 or 3 engines. So comes back to how many mil ac have flown ifr that then crashed due to engine failure . I don't disagree that. 2 is better than 1 when flying over hostile environment
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There are operations that require twins due safety, IFR, hostile terrain etc. There are operations that require singles due no infrastructure of any form thus no tech support/hot and high where twins especially light and medium twins just do not have the payload of a single(ie 350B3) on single engine performance and thus becomes a expensive single/funnily enough due to extreme hostile terrain requiring high performance and range.
Helicopters are extremely versatile and so their application! The argument supporting twins for say SAR/IFR ops becomes the same argument supporting a AS350B3 in the middle of nowhere doing geosurvey at 6000ft. 38+ degree C with a 1.3 ton loop under her 8 hours a day 6 weeks in a row?
Helicopters are extremely versatile and so their application! The argument supporting twins for say SAR/IFR ops becomes the same argument supporting a AS350B3 in the middle of nowhere doing geosurvey at 6000ft. 38+ degree C with a 1.3 ton loop under her 8 hours a day 6 weeks in a row?
Bob,
I must say your outburst came as a complete surprise because nowhere in my post were Europe or the UK mentioned.
The standard of certification for flight in IMC (Appendix B) comes from US regulations - FAR 27/29 (written well before Europe adopted these regulations in 'preference' to their own - in the interest of commonality and cost). The ICAO Standard is one that we (world-wide) develop in harmony, and show compliance with, in accordance with the Chicago Convention.
Redundancy is usually called for when the failure rate of the component is reasonably probable:
Hughes500,
The engine failure rate has remained steady at 1 x 10**-5 (or above) per flying hour for several decades. This number is based upon engine manufacturer's data and shows no bias towards the installation number.
For Category A twins, independence of the engines is provided by the certification code (Appendix C of Part 27 and integral to Part 29) as far as is practical. Double engine failures have been caused by issues such as: simultaneous ingestion of (large amounts of) salt water; FOD events (bird ingestion); volcanic dust; and of course fuel exhaustion. These double failure events cannot be controlled by certification and are therefore addressed by the operational code and training - they are extremely rare.
Jim
I must say your outburst came as a complete surprise because nowhere in my post were Europe or the UK mentioned.
The standard of certification for flight in IMC (Appendix B) comes from US regulations - FAR 27/29 (written well before Europe adopted these regulations in 'preference' to their own - in the interest of commonality and cost). The ICAO Standard is one that we (world-wide) develop in harmony, and show compliance with, in accordance with the Chicago Convention.
Redundancy is usually called for when the failure rate of the component is reasonably probable:
Reasonably probable events...are based on a probability on the order of between 10**-3 to 10**-5.
and the outcome of any failure is likely to be hazardous/catastrophic.Hughes500,
The engine failure rate has remained steady at 1 x 10**-5 (or above) per flying hour for several decades. This number is based upon engine manufacturer's data and shows no bias towards the installation number.
For Category A twins, independence of the engines is provided by the certification code (Appendix C of Part 27 and integral to Part 29) as far as is practical. Double engine failures have been caused by issues such as: simultaneous ingestion of (large amounts of) salt water; FOD events (bird ingestion); volcanic dust; and of course fuel exhaustion. These double failure events cannot be controlled by certification and are therefore addressed by the operational code and training - they are extremely rare.
Jim