Single Engine Flights Over Cities
Hi AnFI
If you consider that a safe forced landing, we will have to agree to disagree. That is not to say she didn't do a bloody good job with the situation she found herself in but the description in the next piece of video describes her 'crashing into a car and sending white smoke billowing into the air' - that doesn't really demonstrate a 'safe forced landing'!
Further video here
Cheers
TeeS
If you consider that a safe forced landing, we will have to agree to disagree. That is not to say she didn't do a bloody good job with the situation she found herself in but the description in the next piece of video describes her 'crashing into a car and sending white smoke billowing into the air' - that doesn't really demonstrate a 'safe forced landing'!
Further video here
Cheers
TeeS
Like everything in life there is a risk, twin, single or whatever. There will always be examples of where things have gone wrong and everyone will say shouldn't have been doing that! Any helicopter crash is news worthy especially in a built up area ! Don't get the same press coverage in a road traffic accident and more than one person is killed on UK roads every day ! I am afraid this comes down to the subjective / objective question. There is no real right !
Hi Tees, not wanting to sound like a smart arse but at 3000ft over anything flying anything with a sudden loss of propulsion could you please advise what would be "safe" about any forced landing.
Join Date: Dec 2008
Location: N/A
Posts: 845
Likes: 0
Received 0 Likes
on
0 Posts
TeeS
You've raised a really interesting point, that is the basis of the twin engined logic.
Really for the maths (of twin helicopters) to work you need to be saving yourself from FATAL CONSEQUENCES (as JimL, (who is the (pro-twin) expert in this field) has previously explained).
People get really confused about what fatal consequences are.
They don't include 'getting wet', being late, having to camp etc
nor do they include minor mundane road traffic inconvenience.
If a safe forced landing was accomplished then it gives you the 20-20 hindsight to be able to say WITH CERTAINTY that a safe forced landing was possible (because it happened). Is it without risk? No. Is anything?
You've raised a really interesting point, that is the basis of the twin engined logic.
Really for the maths (of twin helicopters) to work you need to be saving yourself from FATAL CONSEQUENCES (as JimL, (who is the (pro-twin) expert in this field) has previously explained).
People get really confused about what fatal consequences are.
They don't include 'getting wet', being late, having to camp etc
nor do they include minor mundane road traffic inconvenience.
If a safe forced landing was accomplished then it gives you the 20-20 hindsight to be able to say WITH CERTAINTY that a safe forced landing was possible (because it happened). Is it without risk? No. Is anything?
AnFI,
I'm not sure I would characterise myself as pro-twin but as pro-passenger safety. Like most helicopter pilots, I have flown many more singles than twins and enjoyed doing so. If I have a preference for a helicopter, it is one that gets the job done the most efficiently. The satisfaction in having moved several hundred passengers in a shuttle is enduring.
I have no wish to prolong this thread as I see it as 'question asked', 'question answered'. The only reason I have returned to post is to correct a misconception that appears to be taxing some.
It is quite worrying when a group of professionals need to gather to discuss a phrase that permeates the ICAO Standard and European Regulations and is defined in both. When Tees introduced the phase 'safe forced landing' he was being precise in his use of language; it wasn't to start a debate about 'forced landing' or 'safe' or whether the pilot of the Robinson had done her best, it was to question whether she had met (or was likely to meet) the conditions set out in the definition (or the plain language construct used in most State's regulations).
The term, when used in the ICAO Standard, has a precise meaning - shown in the definition:
The implication is whether it was even possible to meet these conditions in the area in which she chose to fly, or whether a flight, under those conditions, was legal in the State in which the flight was undertaken.
No opinion is offered, judge for yourselves by looking up the references shown in my previous two posts and re-examining the video.
Jim
I'm not sure I would characterise myself as pro-twin but as pro-passenger safety. Like most helicopter pilots, I have flown many more singles than twins and enjoyed doing so. If I have a preference for a helicopter, it is one that gets the job done the most efficiently. The satisfaction in having moved several hundred passengers in a shuttle is enduring.
I have no wish to prolong this thread as I see it as 'question asked', 'question answered'. The only reason I have returned to post is to correct a misconception that appears to be taxing some.
It is quite worrying when a group of professionals need to gather to discuss a phrase that permeates the ICAO Standard and European Regulations and is defined in both. When Tees introduced the phase 'safe forced landing' he was being precise in his use of language; it wasn't to start a debate about 'forced landing' or 'safe' or whether the pilot of the Robinson had done her best, it was to question whether she had met (or was likely to meet) the conditions set out in the definition (or the plain language construct used in most State's regulations).
The term, when used in the ICAO Standard, has a precise meaning - shown in the definition:
Safe forced landing. Unavoidable landing or ditching with a reasonable expectancy of no injuries to persons in the aircraft or on the surface.
No opinion is offered, judge for yourselves by looking up the references shown in my previous two posts and re-examining the video.
Jim
Join Date: Dec 2008
Location: N/A
Posts: 845
Likes: 0
Received 0 Likes
on
0 Posts
JimL
Good balanced answer. Safety is the key. Engine accountability is something else completely not to be confused for safety.
When we look at the increased risk in other areas as a result of having 'engine accountability' this is quite obvious.
It would be a mistake not to take into account the additional risk factors that come with some degree of reduced risk from the specific cause of engines that multi engine should provide. Fuel system problems, many gearbox related incidents, additional tail rotor problems, reduced payload and pilot confusion etc etc
The overwhelming success of forced landings due to engine issues by singles in urban areas is overwhelming evidence of how successful they are, easily qualifiying as a reasonable expectancy. Especially obvious in contrast to the relative lack of success of multi engined helicopters.
Would anyone have a reasonable expectancy for the 300hr girl in Hawaii?
Probably not, shame, we're going to ban something that is not and has not been a problem?
Twins accountable takeoff profile with engine failure permits a crash, although there may well be a 'reasonable expectancy' of no injuries.
(has there just been an EH101 engine related accident?)
Good balanced answer. Safety is the key. Engine accountability is something else completely not to be confused for safety.
When we look at the increased risk in other areas as a result of having 'engine accountability' this is quite obvious.
It would be a mistake not to take into account the additional risk factors that come with some degree of reduced risk from the specific cause of engines that multi engine should provide. Fuel system problems, many gearbox related incidents, additional tail rotor problems, reduced payload and pilot confusion etc etc
The overwhelming success of forced landings due to engine issues by singles in urban areas is overwhelming evidence of how successful they are, easily qualifiying as a reasonable expectancy. Especially obvious in contrast to the relative lack of success of multi engined helicopters.
Would anyone have a reasonable expectancy for the 300hr girl in Hawaii?
Probably not, shame, we're going to ban something that is not and has not been a problem?
Twins accountable takeoff profile with engine failure permits a crash, although there may well be a 'reasonable expectancy' of no injuries.
(has there just been an EH101 engine related accident?)
So, fly a hundred single engine helicopters over congested areas for a thousand hours and give them all engine failures - how many will make a 'safe' forced landing and how many will result in fatal accidents?
Now do the same with twin engine helicopters and give them a single engine failure - what about those results???
Any clues there as to why some authorities might choose to limit singles over cities.
TR and gearbox failure will bring them all down so don't try and skew the stats with those.
Now do the same with twin engine helicopters and give them a single engine failure - what about those results???
Any clues there as to why some authorities might choose to limit singles over cities.
TR and gearbox failure will bring them all down so don't try and skew the stats with those.
Join Date: Nov 2008
Location: UK
Age: 66
Posts: 919
Likes: 0
Received 0 Likes
on
0 Posts
TR and gearbox failure will bring them all down so don't try and skew the stats with those.
Join Date: Dec 2008
Location: N/A
Posts: 845
Likes: 0
Received 0 Likes
on
0 Posts
Crab your answer helps greatly because it highlights with great clarity the point that I am trying to make.
The focus on engines specifically as the cause of the forced landing is a distortion. Just to take that causual factor in isolation is not acheiving the objective.
If the cost for twins of not having to land due to engine issues is a higher chance of other causes (of higher mass, more catestrophic arrivals into people's roofs) then the main objective will not have been acheived.
"TR and gearbox failure will bring them all down so don't try and skew the stats with those."
The risk assosciated with complex gearboxes, with extra freewheel, combining of different torque inputs many stages of speed reduction, many multiply non-redundant components (planetary gears, bearings etc), is clearly a higher inherent risk. If that is part of the cost then it must be factored in.
The same applies to the TR, for more subtle reasons. It also applies to the pilots, particularly in relation to more complex systems leading to greater chance of pilot error.
So it isn't skewing the stats, it is a directly linked 'price to pay'.
Thanks for engaging seriously this time.
100 helicopters for 1000hrs might result in 1 engine failure, the chance of that being 'successful' is 99 out of 100
So that's about 1 catastrophy per 10000 years approximately (for the engine cause). That beats the twin record easily. This legislation is counter productive and pointless.
The focus on engines specifically as the cause of the forced landing is a distortion. Just to take that causual factor in isolation is not acheiving the objective.
If the cost for twins of not having to land due to engine issues is a higher chance of other causes (of higher mass, more catestrophic arrivals into people's roofs) then the main objective will not have been acheived.
"TR and gearbox failure will bring them all down so don't try and skew the stats with those."
The risk assosciated with complex gearboxes, with extra freewheel, combining of different torque inputs many stages of speed reduction, many multiply non-redundant components (planetary gears, bearings etc), is clearly a higher inherent risk. If that is part of the cost then it must be factored in.
The same applies to the TR, for more subtle reasons. It also applies to the pilots, particularly in relation to more complex systems leading to greater chance of pilot error.
So it isn't skewing the stats, it is a directly linked 'price to pay'.
Thanks for engaging seriously this time.
100 helicopters for 1000hrs might result in 1 engine failure, the chance of that being 'successful' is 99 out of 100
So that's about 1 catastrophy per 10000 years approximately (for the engine cause). That beats the twin record easily. This legislation is counter productive and pointless.
AnFI - you are the one not engaging seriously because you can't get away from your own agenda.
It was simple question about engine failures not pilot error (if that is what you were alluding to with the remark about catastrophic arrivals into people's roofs) or any other cause (CFIT or IIMC for example)
The fact that present legislation (here at least) means that singles aren't allowed to operate over congested areas (for example in police or ambulance roles) means that you don't have legitimate stats to make your case.
You need to provide evidence from somewhere where singles spend as much time over congested areas as twins and compare the results of engine failures and the number of successful forced landings by singles in those cases.
The 'extra cost' or 'price to pay' you present as an argument against the added 'complexity' of a twin is just not valid - many singles have complex systems, stages of speed reduction and at least one freewheel which are just as likely to fail.
any actual data to back up that claim??? One engine failure in a single in 100,000 hours???That might be the case for gas turbines but I doubt it is valid for piston engines.
It was simple question about engine failures not pilot error (if that is what you were alluding to with the remark about catastrophic arrivals into people's roofs) or any other cause (CFIT or IIMC for example)
The fact that present legislation (here at least) means that singles aren't allowed to operate over congested areas (for example in police or ambulance roles) means that you don't have legitimate stats to make your case.
You need to provide evidence from somewhere where singles spend as much time over congested areas as twins and compare the results of engine failures and the number of successful forced landings by singles in those cases.
The 'extra cost' or 'price to pay' you present as an argument against the added 'complexity' of a twin is just not valid - many singles have complex systems, stages of speed reduction and at least one freewheel which are just as likely to fail.
100 helicopters for 1000hrs might result in 1 engine failure, the chance of that being 'successful' is 99 out of 100
Sorry Crab, whilst you are correct that fewer singles fly over congested areas, that doesnt prevent 'legitimate stats'
All we need to know is the number of times a single has to make 'an unavoidable landing or ditching' per unit hours flown and the number of times a twin has to do so.
If singles make more such landing in the same number of hours, then it is irrelevant whether the data has been taken from singles flying over cities or uninhabited fields - the aircraft doesnt know what it is flying above
The debate that then needs to follow, if the number of forced landings is less for twins, is whether the reduction in such landings justifies the increased cost and restrictions. That depends on the risk to life of such landings (not so easy to specify) and the willingness of society to balance that risk against benefit
All we need to know is the number of times a single has to make 'an unavoidable landing or ditching' per unit hours flown and the number of times a twin has to do so.
If singles make more such landing in the same number of hours, then it is irrelevant whether the data has been taken from singles flying over cities or uninhabited fields - the aircraft doesnt know what it is flying above
The debate that then needs to follow, if the number of forced landings is less for twins, is whether the reduction in such landings justifies the increased cost and restrictions. That depends on the risk to life of such landings (not so easy to specify) and the willingness of society to balance that risk against benefit
True, but for the issue that a forced landing in a congested area is far less likely to result in a good outcome.
If you want statistics to back up either side of this, you only have to look at the US which does permit single-engine flight over cities and has many single-engine aircraft in public safety roles.
Honestly I have no idea which side of the argument those statistics would support. But anecdotally I don't see a huge number of accidents due to single engine helis making unfortunate forced landings in congested areas and taking out primary schools / kitten farms / whatever, or even the crew.
Again anecdotally, the main cause of heli fatalities in the US seems to be flying in inappropriate conditions. You could have eight engines driving four independent rotor systems and it wouldn't help with that.
But the statistics are there if anyone can be bothered to analyse them.
Honestly I have no idea which side of the argument those statistics would support. But anecdotally I don't see a huge number of accidents due to single engine helis making unfortunate forced landings in congested areas and taking out primary schools / kitten farms / whatever, or even the crew.
Again anecdotally, the main cause of heli fatalities in the US seems to be flying in inappropriate conditions. You could have eight engines driving four independent rotor systems and it wouldn't help with that.
But the statistics are there if anyone can be bothered to analyse them.
... I don't see a huge number of accidents due to single engine helis making unfortunate forced landings in congested areas and taking out primary schools / kitten farms / whatever, or even the crew.
Again anecdotally, the main cause of heli fatalities in the US seems to be flying in inappropriate conditions. You could have eight engines driving four independent rotor systems and it wouldn't help with that.
Again anecdotally, the main cause of heli fatalities in the US seems to be flying in inappropriate conditions. You could have eight engines driving four independent rotor systems and it wouldn't help with that.
Originally Posted by crab
Any clues there as to why some authorities might choose to limit singles over cities.
For those who are posting on this thread, here are a couple of facts that should be well known to professional aviators:
ICAO Annex 2 - Rules of the Air (with which most states comply), Chapter 3.1.2:
FAR 91.119 - the rule for all aviators who have to comply with FARs:
Those who demand that arguments should be backed by statistics should be aware of two issues that would effect collection, collation and analysis of the data:
None of the rules that have been posted on this forum (perhaps with the exception of the Canadian CARs - which are in a revised form) are recent. The exclusion of singles over the congested area of cities is almost as old as the regulations themselves.
Jim
ICAO Annex 2 - Rules of the Air (with which most states comply), Chapter 3.1.2:
3.1.2 Minimum heights
Except when necessary for take-off or landing, or except by permission from the appropriate authority, aircraft shall not be flown over the congested areas of cities, towns or settlements or over an open-air assembly of persons, unless at such a height as will permit, in the event of an emergency arising, a landing to be made without undue hazard to persons or property on the surface.
Except when necessary for take-off or landing, or except by permission from the appropriate authority, aircraft shall not be flown over the congested areas of cities, towns or settlements or over an open-air assembly of persons, unless at such a height as will permit, in the event of an emergency arising, a landing to be made without undue hazard to persons or property on the surface.
§ 91.119 Minimum safe altitudes: General.
Except when necessary for takeoff or landing, no person may operate an aircraft below the following altitudes:
Except when necessary for takeoff or landing, no person may operate an aircraft below the following altitudes:
(a) Anywhere. An altitude allowing, if a power unit fails, an emergency landing without undue hazard to persons or property on the surface.
- Engine failures do not have to be reported under Annex 13 Standards
- The number of SE helicopters flying over cities in breach of the regulations is not known.
None of the rules that have been posted on this forum (perhaps with the exception of the Canadian CARs - which are in a revised form) are recent. The exclusion of singles over the congested area of cities is almost as old as the regulations themselves.
Jim
I would wager that a safe forced landing would be much more likely in most US cities than most European cities - perhaps not the city centres, but in the suburbs, certainly. European cities are generally denser with narrower bendier roads, fewer car parks... What might be reasonable in one jurisdiction might not be so straightforward in another.
That is quite obvious: The large manufacturers of twin helos successfully lobbying the authorities in order to get a bigger share of the public wallet.
Frankly 'Hot and Hi', your assertion about the manufacturers is somewhat simplistic. As Crab said, most of them have an interest in promoting all helicopter types.
'abgd', you are quite correct in your statement; the 'land clear' rule is just that (as can be seen in the US version shown above). Nothing in regulations (North America or Europe) prevents flight over those parts of cities where a safe forced landing could be carried out; that is more to do with the 'fly neighbourly' policy.
Some time ago the link to a paper on the application of exposure to flight over a 'non-congested hostile environment' was put on the HV thread. There was a suggestion that it was incomplete because it had not considered flight over a 'congested hostile environment' (the subject of this thread) and asked for it to be addressed.
The paper was amended with the addition of sections 4.5, 4.6, 4.6.1 and 4.6.2 (and their respective notes) and can be found here:
https://www.dropbox.com/s/pvrwu1jhpe...MS%29.pdf?dl=0
Jim
'abgd', you are quite correct in your statement; the 'land clear' rule is just that (as can be seen in the US version shown above). Nothing in regulations (North America or Europe) prevents flight over those parts of cities where a safe forced landing could be carried out; that is more to do with the 'fly neighbourly' policy.
Some time ago the link to a paper on the application of exposure to flight over a 'non-congested hostile environment' was put on the HV thread. There was a suggestion that it was incomplete because it had not considered flight over a 'congested hostile environment' (the subject of this thread) and asked for it to be addressed.
The paper was amended with the addition of sections 4.5, 4.6, 4.6.1 and 4.6.2 (and their respective notes) and can be found here:
https://www.dropbox.com/s/pvrwu1jhpe...MS%29.pdf?dl=0
Jim
The exclusion of singles over the congested area of cities is almost as old as the regulations themselves.
No consideration for the safety of those living and working in those congested areas who might suddenly find themselves wearing a helicopter (yes I know it happened in London but that was CFIT not and engine failure).
Since great deliberation has gone into protecting the passengers, crews and the population before deciding these rules, why should they be changed to suit a few selfish individuals?
Freedom
Because freedom is a value in itself, and any restriction of individual freedom has to be balanced against the benefits that other members of society gain from restricting the freedom of the former.
It is against the accepted principals of the 'free world' (albeit regrettably an increasing habit of bureaucrats around the world) to justify draconic restrictions of individual freedom with marginal, incremental benefits to the rest of society. If minimal reductions of third parties's exposure to statistical risk would be enforced at all cost, we all would have to be condemned to stay in bed and not to engage in any activity whatsoever.
The accepted principal is that there always is a trade-off, and generally that there are accepted residual risks of life. In aviation, this is what the ICAO rules (as well as FAR's, or South African CAR's) refer to with avoiding "undue" hazards. It implies that there are "due" risks that are acceptable to society.
It is against the accepted principals of the 'free world' (albeit regrettably an increasing habit of bureaucrats around the world) to justify draconic restrictions of individual freedom with marginal, incremental benefits to the rest of society. If minimal reductions of third parties's exposure to statistical risk would be enforced at all cost, we all would have to be condemned to stay in bed and not to engage in any activity whatsoever.
The accepted principal is that there always is a trade-off, and generally that there are accepted residual risks of life. In aviation, this is what the ICAO rules (as well as FAR's, or South African CAR's) refer to with avoiding "undue" hazards. It implies that there are "due" risks that are acceptable to society.