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Jullian

Good question....

The stats provided were not mine, but belong to a US organization called NASA.

National Aeronautics and Space Administration (NASA) performed a study of US Civil Rotorcraft Accidents over a 34 year period.

http://www3.verticalgateway.com/portals/54/industry_reports/NASA%20TP%20209597.pdf

The link above will provide you with the entire 300+ page report.

 

The previous post was to show that twin turbine helicopters may reduce the frequency of engine failures, but the increase in airframe/component failures offset any advantage to twin turbine.

 

Single turbine helicopters are the backbone of this great industry, so I would expect that they may be involved in more long line operations than twin engine helicopters. I do not have any data to confirm this though.

 

Helicopter accidents for 2010 were 1.64 accidents per 100,000 flight hours and 1.44 accidents per 100,000 flight hours.

These numbers hardly represent a significant safety advantage of twin over single or visa versa.

If you want to know which numbers belong to which class of helicopter, you can buy the copyrighted report, as I did, from Robert E Breiling Associates.

 

From a legal standpoint mentioned in the original post, you may want to do a Google search for “helicopter burn victim lawyers” I think they may have a much more persuasive argument to a jury rather than trying to prove negligence by operations in the H/V curve, which is not a limitation on most helicopters.

 

Wayne

 

If I understand your argument correctly, we should run our business according to what a big-nosed American lawyer might think of our operation. Is that right?

 

Jerry

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”Engine Material Failure (MF) initiated the crashes that caused 14.8 percent of the serious injuries to occupants of single-turbine helicopters, as compared to only 3.4 percent for the serious injuries to the occupants of twin-turbine helicopter accidents. If only this one piece of information is considered, the obvious conclusion is that two engines are better than one.

 

However, next consider only the cause factor of material failures other than engine (non-engine MF). In this case, only 11.0 percent of the seriously injured occupants were involved in single-turbine helicopter crashes initiated by non-engine material failures as compared with 31.0 percent of those in twin- turbine helicopter crashes. This is an indicator of the detrimental effects of complexity and more parts. If one were to consider only this last piece of information, the obvious approach should be that one engine is better than two – a reversal of the previous paragraph.

 

Actually, the total material failures, engine and non-engine, should be considered together, which yields percentages of seriously injured occupants due to all types of MF-caused accidents of 25.8 percent for occupants in single turbines and 34.4 percent for occupants in twins. This is consistent with more parts and complexities being present in twins. Because causes of death and injury cannot be limited only to those that are engine related, it is essential that all other factors be considered – both material failure and non-material failure (i.e., human error) “

 

The above excerpt is not from a dead 19th century British Prime Minister, but is from Mr. Roy G. Fox who is the Chief of Product Safety Engineering for Bell Helicopter Textron. It is based on over fifty million flight hours on the worldwide Bell civil fleet which numbers around 30,000 helicopters.

 

Vortex was very accurate in his post that 85% of all accidents are a result of human error. Bell puts the number at 84%.

 

Jerry – No, you did not understand my comments correctly. And to quote your friend Disraeli: “What we anticipate seldom occurs; but what we least expect generally happens”

 

Hope to see lots of operators at the BC Hydro “get-together” on the 23th and 25th of this month.

 

Wayne

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Wayne, I haven't dug through the entire thread, so you may have addressed this, but isn't it possible, even likely, that the greater percentage of injuries being attributed to twins is the result of them being much more a 'people carrier' than singles, especially considering the offshore and aeromedical markets?

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The above numbers in post #42 were based on Bell Helicopters Fleet.

Twin Engine machines are 212, 222, 230, 214ST, 412, 430.

Single Engine are 206, 206L/L3/L4, 204, 205, 407, 214.

 

I would expect that the higher percentage of injuries could be attributed partially to a slightly higher seat capacity in the Bell twin engine machines, although I have no numbers to confirm this.

 

NASA on the other hand, does identify a “disturbing trend” which identifies a higher fatality rate with larger helicopters which are capable of carrying more passengers.

 

NASA puts the fatality rate of single engine helicopter accidents at 0.42 fatalities per accident, and twin engine accidents at 1.06 per accident.

 

Despite the amount of serious injuries or fatalities from accidents, the overall accident rate per 100,000 flight hours is almost identical between single and twin engine helicopters.

 

As previously stated, twin turbine helicopters may reduce the frequency of engine failures, but the increase in airframe/component failures may offset any advantage to twin turbine.

 

Wayne

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The above numbers in post #42 were based on Bell Helicopters Fleet.

Twin Engine machines are 212, 222, 230, 214ST, 412, 430.

Single Engine are 206, 206L/L3/L4, 204, 205, 407, 214.

 

I would expect that the higher percentage of injuries could be attributed partially to a slightly higher seat capacity in the Bell twin engine machines, although I have no numbers to confirm this.

 

NASA on the other hand, does identify a “disturbing trend” which identifies a higher fatality rate with larger helicopters which are capable of carrying more passengers.

 

NASA puts the fatality rate of single engine helicopter accidents at 0.42 fatalities per accident, and twin engine accidents at 1.06 per accident.

 

Despite the amount of serious injuries or fatalities from accidents, the overall accident rate per 100,000 flight hours is almost identical between single and twin engine helicopters.

 

As previously stated, twin turbine helicopters may reduce the frequency of engine failures, but the increase in airframe/component failures may offset any advantage to twin turbine.

 

Wayne

 

I think there is a missing element of the stats reported that must be taken into account. All of your stats are based upon "accidents". It would make perfect sense that a single engine helicopter with an engine failure is going to have more first event "accidents" than a twin, but does that mean there are less engine failures in a twin, not necessarily, or at least not shown by your stats. It would also make sense that there are more injury realated accidents when a twin engine helicopter has an an event leading to an accident after an engine failure. This again does not mean the twin is more prone to injury it only means that the time of the failure leads to an injury more than the single. Why would that be? Could be the the utilization that the twin is used for at the time(ifr,over water, etc)may not be conducive to a landing sans injury if the aircraft is not able to fly away on one engine to a safe landing. Whereas the single engine aircraft with an engine failure may not be in such a bad spot if the engine failure happens and leads to an accident. Am I saying it is safer in a single after an engine failure, NO, but am just pointing out that the areas that twins are used is generally for a reason and that reason is valid, yet if the aircraft ends in an accident, it will probably be bad in a twin.

 

Would like to see stats which show the number of engine failures in twin vs single comparison. Am guessing this will show there are far more engine failures in a twin, this is one of the reasons which class D is allowed in Canada with a single engine helicopter, because a man named Claire Isrealson went to Transport Canada when the CARS were first instituted and lobbied this and was well armed with stats showing this. Had he not lobbied this, the operators who were doing and still are doing class D single engine rescues would have been legislated to use a twin engine helicopter which would be able to maintain hover with one engine operating, at the weight and altitude of intended operations. At the time, there were two light twin aircraft in the world capable of doing this in Banff Park and neither were certified in Canada at the time(355N and Agusta 109K2).

 

The idea of using a twin engine helicopter for longlineing is a great idea. Flying along while doing line patrols over unfriendly country with light load and speed,,,,only makes sense to use twin. Would I want to heliski in a 212 vs B2,,,B2 any day as the stress is much less. Would I rather be in the B2 heliskiing vs 212 with a light load in the 212,,,212. Problem is that too many think the twin is safer period, the twin is only safer in my opinion if flown as such. This subject is so complex as you have to take into account the realiability of the particular single vs realiability of the twin as well. Perhaps being in a clapped out old twin working its butt off is not as safe as a modern single ie:109A vs 119KE. Or perhaps some modern singles are not as safe as clapped out old twin ie: 120 vs 355(just my opinion, don't freak out),,, apples and apples.

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Once again, the stats are not mine, but belong to NASA and Bell.

 

If you base your safety only on an engine failure, you are missing the other 85% of the equation.

 

Safety decisions on any one aspect of helicopters should not be made without considering all the other safety aspects, as well as the human causes.

 

Fly safe in your "clapped out old twin".

 

Wayne

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Once again, the stats are not mine, but belong to NASA and Bell.

 

If you base your safety only on an engine failure, you are missing the other 85% of the equation.

 

Safety decisions on any one aspect of helicopters should not be made without considering all the other safety aspects, as well as the human causes.

 

Fly safe in your "clapped out old twin".

 

Wayne

 

Was not basing my safety on engine failures, that was exactly my point, that an engine failure in a twin does not necessarily lead to an accident whereas in a single it has a lot greater chance to end in one and that the stats you provided did not speak of such, only the accident rates. The fella who started the thread was trying to get opinions on the legalities and due diligence of using single on longline ops. Some twins are extremely simple and thus not a huge headache to deal with. Others have the redundancies of a twin engine lawn mower(ie one fuel filler neck to 5 tanks and two engines,,,,whatttt) It is these issues that good helicopter companies deal with in a logical fashion so they either have extremely experienced crews with excellant training on the funky old twin or they go with something more simple. Which is my point to the whole exercise, do not get caught up in the single vs twin argument but to try and match the operation with the "proper" aircraft and ensure that aircraft can be matched up with your crew, if the proper aircraft does not fit with your crew then perhaps it is not the right time or place to make that change, this type of learning curve can only be done with proper training and experience.

 

I think if they want safer operations these companies should develope a load rating of 75% of OGE available performance and THAT would be safer instantly. Then if they really wanted to be safe add the twin to the equation. Or they can use donkeys then none of us get hurt(least that is what my risk matrix says).

 

Flying safe in my prestine old single(not over water, night or ifr) with lots of power, simplicity and reliability(B2 and Lama).

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"I think if they want safer operations these companies should develope a load rating of 75% of OGE available performance and THAT would be safer instantly"

 

Hear hear! Especially when twins tend to cut the fuel flow when the engines get overtorqued - i.e. the RRPM drops right when you need the power. I teach my students that a twin is only safer when one engine fails, and that your flight planning is now on steroids.

 

Phil

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Was not basing my safety on engine failures, that was exactly my point, that an engine failure in a twin does not necessarily lead to an accident whereas in a single it has a lot greater chance to end in one and that the stats you provided did not speak of such, only the accident rates. The fella who started the thread was trying to get opinions on the legalities and due diligence of using single on longline ops. Some twins are extremely simple and thus not a huge headache to deal with. Others have the redundancies of a twin engine lawn mower(ie one fuel filler neck to 5 tanks and two engines,,,,whatttt) It is these issues that good helicopter companies deal with in a logical fashion so they either have extremely experienced crews with excellant training on the funky old twin or they go with something more simple. Which is my point to the whole exercise, do not get caught up in the single vs twin argument but to try and match the operation with the "proper" aircraft and ensure that aircraft can be matched up with your crew, if the proper aircraft does not fit with your crew then perhaps it is not the right time or place to make that change, this type of learning curve can only be done with proper training and experience.

 

I think if they want safer operations these companies should develope a load rating of 75% of OGE available performance and THAT would be safer instantly. Then if they really wanted to be safe add the twin to the equation. Or they can use donkeys then none of us get hurt(least that is what my risk matrix says).

 

Flying safe in my prestine old single(not over water, night or ifr) with lots of power, simplicity and reliability(B2 and Lama).

 

 

Actually, almost 60% of twin engine failures begin with total loss of power to both engines. (NASA)

 

My point was not that there are any more or less engine failures in a twin, but the fact that the possibility of a structural or component failure in a twin is almost identical to the possibility of an engine failure in a single.

 

So in regards to long lining in a twin or a single, are you better prepared for a structural/component failure or an engine failure? For a line patrol or heli-skiing, the same stats apply.

 

Training, experience, good engineering, SMS – all are key to safe operations, as you eluded to, whether you are flying a twin or a single.

 

You might want to revisit the claim regarding a 355N for longline rescue operations. With OEI, one pilot, one technician, one victim and minimum fuel, you would not (according to my old 355N OEI HOGE charts) even be able to lift off the ground in Canmore on a standard day, let alone try and perform any type of rescue at 6000’+.

Your B2 or Lama is much better suited for that type of operation.

 

Wayne

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