Elevated Helipads
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TC ... yer off yer trolly!
So to conclude no one knows of an engine failing during this period !
Sounds like classic "This is the way to do it" - pet theory of one pilot gone mad - someone said MACS invented this nonsense - true?
(TC : I'd try and look at the actual risk factors during t/o and optimise for those - it obviously would put this non-existant risk quite low down the list of influencing factors on a t/o profile)
Sounds like classic "This is the way to do it" - pet theory of one pilot gone mad - someone said MACS invented this nonsense - true?
(TC : I'd try and look at the actual risk factors during t/o and optimise for those - it obviously would put this non-existant risk quite low down the list of influencing factors on a t/o profile)
Q max
To help convince us of your argument why don't you list all these actual risk factors that you wish to optimise for and then tell us the profile you would use to negate them. I'm not talking about operating from a clear area such as an airfield because we don't usually fly these profiles then!
TeeS
To help convince us of your argument why don't you list all these actual risk factors that you wish to optimise for and then tell us the profile you would use to negate them. I'm not talking about operating from a clear area such as an airfield because we don't usually fly these profiles then!
TeeS
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up & back?
tees summed it up but i agree with deltafree, it sounds like an old wives tale!
sure you can see the helipad but do you need to? what about that tree (building or ariel) out the window? and if youve got room and power to back up downwind when towering, why not back up along the ground and tower foward reducing the power reqired,
when these cat A takoffs are used, do you need crewmen hanging out the window watching the tail? and why 100 feet, the less time spent towering the more safer i would think.
remember vortex ring state needs just a little airspeed and a quick decent, just the right mixture.
Shawn Coyle : can you explain the bell slide technique?
sure you can see the helipad but do you need to? what about that tree (building or ariel) out the window? and if youve got room and power to back up downwind when towering, why not back up along the ground and tower foward reducing the power reqired,
when these cat A takoffs are used, do you need crewmen hanging out the window watching the tail? and why 100 feet, the less time spent towering the more safer i would think.
remember vortex ring state needs just a little airspeed and a quick decent, just the right mixture.
Shawn Coyle : can you explain the bell slide technique?
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QMAX
Not quite the same as a helipad, but yes I have had an engine failure immediately after rotating during an offshore towering-type take-off, so it can happen and has.
During the 1970s Bristow used a verical take-off profile from the Wessex for use when taking off from helipads in the jungle/swamps. It had the advantage of getting you back on to a known safe area i.e. the solid wooden/concrete helipad from which you had just departed. I seem to remember that the procedure was to climb vertically to 200 feet and CDP was at the point of rotation. Provided you used a lateral reference for the (slow) descent the only problem was usually in the mind of the pilot involved, as before actually carrying out the procedure it seemed as if it might be a bit hairy. The Wessex had much worse downward visibility than most modern helicopters, so I guess that once the procedure has been practised a few times it may not seem as bad as it looks from just reading about it in the FM.
Not quite the same as a helipad, but yes I have had an engine failure immediately after rotating during an offshore towering-type take-off, so it can happen and has.
During the 1970s Bristow used a verical take-off profile from the Wessex for use when taking off from helipads in the jungle/swamps. It had the advantage of getting you back on to a known safe area i.e. the solid wooden/concrete helipad from which you had just departed. I seem to remember that the procedure was to climb vertically to 200 feet and CDP was at the point of rotation. Provided you used a lateral reference for the (slow) descent the only problem was usually in the mind of the pilot involved, as before actually carrying out the procedure it seemed as if it might be a bit hairy. The Wessex had much worse downward visibility than most modern helicopters, so I guess that once the procedure has been practised a few times it may not seem as bad as it looks from just reading about it in the FM.
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So that's no-one then !!
I guess the extra risks are being run just for the sake of theory then ?
Surely some one must know of an engine failure actually happening during this 'backward' climbing phase - anyone?
I'd expect there to be at least one freak occurance of this dogma actually being useful !
Soggy: after rotation right? Would you still have had a problem if you had been using the energy you 'wasted' by climbing (at such an inefficient speed) to accelerate to efficient translational lift state?
Surely some one must know of an engine failure actually happening during this 'backward' climbing phase - anyone?
I'd expect there to be at least one freak occurance of this dogma actually being useful !
Soggy: after rotation right? Would you still have had a problem if you had been using the energy you 'wasted' by climbing (at such an inefficient speed) to accelerate to efficient translational lift state?
O.K. Q max, you have finally convinced me. I have been doing it wrong all these years and will not be doing any more helipad profiles.
Please can I have the benefit of your experience, how should I go about departing from a helipad that is surrounded by houses, a hospital and an office block?
Thankyou in avid anticipation,
TeeS
Please can I have the benefit of your experience, how should I go about departing from a helipad that is surrounded by houses, a hospital and an office block?
Thankyou in avid anticipation,
TeeS
Qmax: you're not answering anyones questions. There is an overwhelming appreciation of these profiles. Where on earth did you hear that MASL designed these..do they have an international mandate on takeoff profiles? Do they supercede the manufacturers design criteria? These profiles have been around for years and are designed for I REPEAT: engine failure.
if you still refuse to accept that some people have had engine problems necessitating the use of this profile to get them back to earth safely, then shall we scrap them then because there are no engine failures during t/o any more and never will be
Please answer the question:
WHAT WOULD YOU SUGGEST WE USE QMAX....
Armchair judging again, methinks....always ready to criticise but nothing constructive to add to the conversation
if you still refuse to accept that some people have had engine problems necessitating the use of this profile to get them back to earth safely, then shall we scrap them then because there are no engine failures during t/o any more and never will be
Please answer the question:
WHAT WOULD YOU SUGGEST WE USE QMAX....
Armchair judging again, methinks....always ready to criticise but nothing constructive to add to the conversation
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My Answer
I asked if anyone could tell me of any advantages to this vertical profile. I guess for the pure flying side there are none, but it is clear that HEMs have a need for such a profile. I am sorry I do not have the rest of the FM as this profile was just shown to me by a mate, but I assume the vertical requirements will be harsher than an equivalent up and back. I guess none of us want a different profile for every conceivable departure so it is fair to replace the up and back for a towering one. Am I right?
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QMAX,
You're obviously not familiar with offshore towering take-offs. Yes, I'd have had a lot of problems as the immediate sink whilst I was trying to accelerate forward would undoubtedly resulted in my striking the deck edge with my tail and pitching nose forward into the sea before 'accelerating to an efficient translational lift state'.
All of these certificated vertical and rearward take-off profiles have considerable restrictions on the permitted take-off weight to allow for the performance deterioration whilst flying them and are intended for the many times in helicopters where space considerations do not permit acceleration with a safe single engine reject before CDP using ICAO Class One performance criteria (or Group A/Category A or whatever one is using) to ensure that it is possible to reject on to an area where a landing may be made without damage to the aircraft, its occupants or third parties.
Just because there may have been no recorded instances of an engine failure when these profiles are being flown does not mean there never will - Mr Murphy will always be around to guarantee that.
I think you are suffering from the Australian ostrich disease and burying your head in the sand when confronted with things with which you either do not agree or do not understand.
You're obviously not familiar with offshore towering take-offs. Yes, I'd have had a lot of problems as the immediate sink whilst I was trying to accelerate forward would undoubtedly resulted in my striking the deck edge with my tail and pitching nose forward into the sea before 'accelerating to an efficient translational lift state'.
All of these certificated vertical and rearward take-off profiles have considerable restrictions on the permitted take-off weight to allow for the performance deterioration whilst flying them and are intended for the many times in helicopters where space considerations do not permit acceleration with a safe single engine reject before CDP using ICAO Class One performance criteria (or Group A/Category A or whatever one is using) to ensure that it is possible to reject on to an area where a landing may be made without damage to the aircraft, its occupants or third parties.
Just because there may have been no recorded instances of an engine failure when these profiles are being flown does not mean there never will - Mr Murphy will always be around to guarantee that.
I think you are suffering from the Australian ostrich disease and burying your head in the sand when confronted with things with which you either do not agree or do not understand.
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Consider the same sort of thing in FW airplanes. The airlines schedule their performance, weight and so on to ensure they can always either stop safely on the remaining runway, or continue the takeoff and climb safely. They often take a performance hit either in weight or engine life (can't necessarily use a reduced performance takeoff and save engine life).
The Category A procedures are nothing less than the RW equivalent. If we think we can use something that is less safe for the fare-paying public, then I think we're fooling ourselves.
This is not to say that the procedures are perfect, or that we should not continually question why and how they are made, or the assumptions they are based on, but remember this is an attempt to make things safe.
Some of the issues that need to be considered are- exposure times on takeoff; better airspeed indicating systems so we can take best advantage of performance before the pitot system starts to work; better information for determining the decision points; ways to make the charts easier to use; weather reporting at the helipads; better guidance in and out of the helipad; and so on.
But let's not forget the aim - to improve the level of safety to something approaching that of the airlines.
The Category A procedures are nothing less than the RW equivalent. If we think we can use something that is less safe for the fare-paying public, then I think we're fooling ourselves.
This is not to say that the procedures are perfect, or that we should not continually question why and how they are made, or the assumptions they are based on, but remember this is an attempt to make things safe.
Some of the issues that need to be considered are- exposure times on takeoff; better airspeed indicating systems so we can take best advantage of performance before the pitot system starts to work; better information for determining the decision points; ways to make the charts easier to use; weather reporting at the helipads; better guidance in and out of the helipad; and so on.
But let's not forget the aim - to improve the level of safety to something approaching that of the airlines.
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soggyboxers
you said >Yes, I'd have had a lot of problems as the immediate sink whilst I was trying to accelerate forward would undoubtedly resulted in my striking the deck edge with my tail and pitching nose forward into the sea before 'accelerating to an efficient translational lift state'.
surely if you've got enough power to verticle up out of ground effect, you would have enough to stop you falling off the edge. you could even hover over the edge and accelerate from there.
and wouldnt there be enough hight off the edge of the pad to fly away even if one engine failed, rather than tempting vortex ring on the way back down?
surely if you've got enough power to verticle up out of ground effect, you would have enough to stop you falling off the edge. you could even hover over the edge and accelerate from there.
and wouldnt there be enough hight off the edge of the pad to fly away even if one engine failed, rather than tempting vortex ring on the way back down?
Last edited by vorticey; 31st Oct 2002 at 09:13.
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EMPEROR'S CLOTHING ...
... sometimes when there is an intrenched philosophy it is difficult for people who have been immersed in it to see the truth - people start whole 'religions' based on twisted ideas.
Reading the accident reports for twins it is clear that the utility of this profile is insignificant in comparison with the other risk factors (and may actually be counterproductive).
I am happy to start trying to collate them and will make a non exhaustive preliminary stab at it:
1 This profile exposes the helicoter to a high risk scenario for much greater time.
2 Uses the upper range of engine output for considerably longer.
3 Uses a higher relative power output than alternative.
4 The machine is vunerable to other failures, T/R malfunctions, crew coordination, collision.
5 Incresed exposure to control problems - having such a low energy state for such a long period makes the A/C vunerable to the random vagaries of the atmosphere with at least two major controls running near their limits (or potentially near their limits) (T/R and Collective).
6 The greatest mitigator for risk on takeoff is to have a deliberate 'extended hover phase' prior to T/O. During this period the probability of ANY catastrophic event drops rapidly with time.
7 The 'BIG IDEA' of twin engines is supposed to be that it 'doesn't matter' if one fails. If you fly a regime where you actually NEED two engines - then the risk is much higher since there is at least twice the chance that one of the two might let go.
8 Three or more hands required (throttle levers) for longer - reversing the benefits of two independant crew and making it two crew dependant.
9 Increased FOD risk - (look at the accidents)
Is it REALLY worth exposing the helicopter to these EXTRA risks for the return of it being THEORETICALLY possible to withstand an event of such unlikelyhood that as far as we can determine it has NEVER HAPPENED ?
Furthermore it is more amazing that this event does not occur more often since the very profile we are talking about ACTUALLY INCREASES (dramatically) the likelyhood of it occuring!
-----------
Soggy : of course HAD your 'engine event' occured at the critical point in a translating type profile then yes you may well have hit your tail. - BUT clearly the fact of the matter (which you side stepped) is that in your case since the engine let go "just after rotation" you would have had sufficient energy production (especially applied in a more energy efficient manner) to have been at an aerodynamically efficient velocity - such that it would not have been a factor - FURTHERMORE to what extent was the power failure you experienced ATTRIBUTABLE to the profile you were flying?
THEREFORE your case is still NOT an example of that profile being of ant ACTUAL use - only THEORETICAL.
------------
There have been NO EXAMPLES of an engine failing during the climbing up and back.
I asked the most a highly experienced (>40,000 hrs) Rotary pilot (that I know of) weather he ever used this profile in the military twin he flew : He said "certainly not!" and went on to explain why it is the most absurd concept - he though it had been 'invented' by a British operator (MACS or Bristow) to keep their Flight Ops Inspector happy - and avalanched from there.
Yes the twin has a place in risk reduction - but it's not always safer.
To make any true improvements to safety one must be honest to the factors and figures in a scientific way.
The discussion should be in terms of TIME EXPOSED to RISK EVENT (TE) and PROBABILITY per TIME of EVENT (PTE) occuring and PROBABILITY of UNSECESSFUL OUTCOME to event (PUO).
With this profile both TE and PTE increase (and are multiplicative) PUO might (theoretically) be reduced. At the moment only PUO is looked at - this is a major flaw.
I don't really expect anyone to start actually re-evaluating this.
REMEMBER THE STORY OF THE EMPEROR'S CLOTHING ?
Reading the accident reports for twins it is clear that the utility of this profile is insignificant in comparison with the other risk factors (and may actually be counterproductive).
I am happy to start trying to collate them and will make a non exhaustive preliminary stab at it:
1 This profile exposes the helicoter to a high risk scenario for much greater time.
2 Uses the upper range of engine output for considerably longer.
3 Uses a higher relative power output than alternative.
4 The machine is vunerable to other failures, T/R malfunctions, crew coordination, collision.
5 Incresed exposure to control problems - having such a low energy state for such a long period makes the A/C vunerable to the random vagaries of the atmosphere with at least two major controls running near their limits (or potentially near their limits) (T/R and Collective).
6 The greatest mitigator for risk on takeoff is to have a deliberate 'extended hover phase' prior to T/O. During this period the probability of ANY catastrophic event drops rapidly with time.
7 The 'BIG IDEA' of twin engines is supposed to be that it 'doesn't matter' if one fails. If you fly a regime where you actually NEED two engines - then the risk is much higher since there is at least twice the chance that one of the two might let go.
8 Three or more hands required (throttle levers) for longer - reversing the benefits of two independant crew and making it two crew dependant.
9 Increased FOD risk - (look at the accidents)
Is it REALLY worth exposing the helicopter to these EXTRA risks for the return of it being THEORETICALLY possible to withstand an event of such unlikelyhood that as far as we can determine it has NEVER HAPPENED ?
Furthermore it is more amazing that this event does not occur more often since the very profile we are talking about ACTUALLY INCREASES (dramatically) the likelyhood of it occuring!
-----------
Soggy : of course HAD your 'engine event' occured at the critical point in a translating type profile then yes you may well have hit your tail. - BUT clearly the fact of the matter (which you side stepped) is that in your case since the engine let go "just after rotation" you would have had sufficient energy production (especially applied in a more energy efficient manner) to have been at an aerodynamically efficient velocity - such that it would not have been a factor - FURTHERMORE to what extent was the power failure you experienced ATTRIBUTABLE to the profile you were flying?
THEREFORE your case is still NOT an example of that profile being of ant ACTUAL use - only THEORETICAL.
------------
There have been NO EXAMPLES of an engine failing during the climbing up and back.
I asked the most a highly experienced (>40,000 hrs) Rotary pilot (that I know of) weather he ever used this profile in the military twin he flew : He said "certainly not!" and went on to explain why it is the most absurd concept - he though it had been 'invented' by a British operator (MACS or Bristow) to keep their Flight Ops Inspector happy - and avalanched from there.
Yes the twin has a place in risk reduction - but it's not always safer.
To make any true improvements to safety one must be honest to the factors and figures in a scientific way.
The discussion should be in terms of TIME EXPOSED to RISK EVENT (TE) and PROBABILITY per TIME of EVENT (PTE) occuring and PROBABILITY of UNSECESSFUL OUTCOME to event (PUO).
With this profile both TE and PTE increase (and are multiplicative) PUO might (theoretically) be reduced. At the moment only PUO is looked at - this is a major flaw.
I don't really expect anyone to start actually re-evaluating this.
REMEMBER THE STORY OF THE EMPEROR'S CLOTHING ?
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Vorticey,
Sorry, but you've obviously never done an offshore helideck take off. The amount of power you're pulling in the hover (which is often at, or close to, the maximum allowable gross weight for the technique) normally gives a thrust margin of only 2 to 4 per cent. This is enough to allow a 'vertical' acceleration to just sufficient height for the tail to clear the deck in the event of an engine failure at rotation. The 'height' attained in this procedure is only 10-20 feet (dependant on aircraft type), so you're still in ground effect; is done close enough to the centre of the deck that none of the blades is overhanging the edge (to ensure no loss of ground effect); and is sufficiently low that there is no chance of vortex ring state developing. There's also not the slightest possibility of hovering on one engine at the take-off weight you're at, you're just going down. Hope that explains it a bit better.
QMAX
You sound more like a statistician than a pilot - difficult to know as you have nothing noted on your user profile, but it seems to me that you are the only one on this thread who has an .e ntrenched philosophy and you still have obviously not got the slightest idea of what an offshore helideck take-off is like (and from the sound of it no idea whatsoever of what an onshore restricted helideck take-off is like either).
in your case since the engine let go "just after rotation" you would have had sufficient energy production (especially applied in a more energy efficient manner) to have been at an aerodynamically efficient velocity - such that it would not have been a factor - FURTHERMORE to what extent was the power failure you experienced ATTRIBUTABLE to the profile you were flying?
Engines don't 'let go' - to we pilots, they fail. With only 5% torque in hand, I was pulling exactly the same amount of power as I would have in a forward transition type of take-off, and my engine failure was not related to the power I was pulling. Your talk of 'aerodynamically efficient velocity' is just nonsense - I was at a velocity of ZERO having just rotated the nose down from the hovering attitude.
The only vagaries associated with this thread seem to be your vague and uninformed ramblings.
Sorry, but you've obviously never done an offshore helideck take off. The amount of power you're pulling in the hover (which is often at, or close to, the maximum allowable gross weight for the technique) normally gives a thrust margin of only 2 to 4 per cent. This is enough to allow a 'vertical' acceleration to just sufficient height for the tail to clear the deck in the event of an engine failure at rotation. The 'height' attained in this procedure is only 10-20 feet (dependant on aircraft type), so you're still in ground effect; is done close enough to the centre of the deck that none of the blades is overhanging the edge (to ensure no loss of ground effect); and is sufficiently low that there is no chance of vortex ring state developing. There's also not the slightest possibility of hovering on one engine at the take-off weight you're at, you're just going down. Hope that explains it a bit better.
QMAX
You sound more like a statistician than a pilot - difficult to know as you have nothing noted on your user profile, but it seems to me that you are the only one on this thread who has an .e ntrenched philosophy and you still have obviously not got the slightest idea of what an offshore helideck take-off is like (and from the sound of it no idea whatsoever of what an onshore restricted helideck take-off is like either).
in your case since the engine let go "just after rotation" you would have had sufficient energy production (especially applied in a more energy efficient manner) to have been at an aerodynamically efficient velocity - such that it would not have been a factor - FURTHERMORE to what extent was the power failure you experienced ATTRIBUTABLE to the profile you were flying?
Engines don't 'let go' - to we pilots, they fail. With only 5% torque in hand, I was pulling exactly the same amount of power as I would have in a forward transition type of take-off, and my engine failure was not related to the power I was pulling. Your talk of 'aerodynamically efficient velocity' is just nonsense - I was at a velocity of ZERO having just rotated the nose down from the hovering attitude.
The only vagaries associated with this thread seem to be your vague and uninformed ramblings.
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Q Max and Vorticey
Wow......such attitude and ignorance can really hurt...........
Yes the CAT A profile does work....and work well..........a few years ago during a final handling test in a HP, the engine failed just at CDP.......well it was a real anti climax as the applicant put his nose down to 15 Deg and raised it up as VTOSS was passed......and the Rad Alt showed more than 35 ft at all stages..........we were loaded with sand and fuel and were at max CAT A weight..........so please talk about things that you have some knowledge about........or ask questions to gain that knowledge......but please don't preach on subjects in which your knowledge is lacking.
I guess your way of doing this would have been to lift and transit forward over the houses or schools or buildings.......then when you have a failure before VTOSS....guess where you are going......yes on the 6 O'clock news.
Offshore Approaches and Departures in every country that I have worked are never CAT A......and I don't think the Offshore Oil Industry anywhere would accept them at all..........A modified CAT B technique is used throughout the industry, and if done correctly will reduce the "exposed" flight time where flight may not be possible, down to a few nano seconds........statistically proven to be safe and acceptable......
Yes the CAT A profile does work....and work well..........a few years ago during a final handling test in a HP, the engine failed just at CDP.......well it was a real anti climax as the applicant put his nose down to 15 Deg and raised it up as VTOSS was passed......and the Rad Alt showed more than 35 ft at all stages..........we were loaded with sand and fuel and were at max CAT A weight..........so please talk about things that you have some knowledge about........or ask questions to gain that knowledge......but please don't preach on subjects in which your knowledge is lacking.
I guess your way of doing this would have been to lift and transit forward over the houses or schools or buildings.......then when you have a failure before VTOSS....guess where you are going......yes on the 6 O'clock news.
Offshore Approaches and Departures in every country that I have worked are never CAT A......and I don't think the Offshore Oil Industry anywhere would accept them at all..........A modified CAT B technique is used throughout the industry, and if done correctly will reduce the "exposed" flight time where flight may not be possible, down to a few nano seconds........statistically proven to be safe and acceptable......
Last edited by Old Man Rotor; 31st Oct 2002 at 14:24.
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Please ignore this long and boring post.....
As I said: "Yes the twin has a place in risk reduction - but it's not always safer. "
So, yes, under some circumstances twins can actually be safer - the extent and the circumstances are often exaggerated.
Soggy said: "Just because there may have been no recorded instances of an engine failure when these profiles are being flown does not mean there never will - Mr Murphy will always be around to guarantee that. " - sure but if they have never been used and they increase risk in other ways then isn't it fair to look at them again?
If you are exposed in an aircraft which needs two engines both working then the risk is greater than had you only had one.
Old Man: I did express my surprise that noone had benefitted from the use of these profiles - and none had. Obviously you are now a big fan of them. Do you maintain that that was actually a ZERO risk event for you? Hopefully not! - what were you thinking doing a test over "houses or schools or buildings" anyway - or where your "houses schools or buidings" theoretical ones which fortunately, since you made them up, were no taller than 35ft?
Mind you you probably wouldn't make the news by hitting a theoretical building !
Old Man: you said (while being mildly insulting ... but fair enough): "or ask questions to gain that knowledge" - I thought I was asking: Has anyone had an engine failure during the climbing upwards and backwards bit (ie after hover and before CDP (or is it TDP?)) - I guess that's still no-one is it?
But seriously thanks for the education - it's true I had actually forgotten the EXPOSURE time concepts of these CAT B profiles and yes of course the risk is minimal - the greater benefit being derived from the prolonged Exposure to a Hostile Landing Environment - It's a clear example of a single engined aircraft being safer for a short phase of the flight but the twin probably being superior in view of the prolonged exposure time. (mind you.....)
If you just run the calculations in accordance with the published regulations you can compute the exposure time required to make a CAT A twin safer. It is suprisingly long. Don't make me go and look it up again..... I can't be arsed....
The table of statistics (pointed out by Nick Lappos) published on the twins/singles thread clearly shows the higher risk of twins.
Is there a big problem in the Gulf of Mexico from running singles?
- I don't think so.
Finally - yes I am recieving something of an education - in a subject which I do know something (though not much)about - I have actually dabbled at flying a couple of times - but I have to say I am partially tounge in check while pulling the odd leg and seem to have hit a raw nerve.... and I don't really want to offend against anyones 'pet theories' even if they are a perverted bastardisation of the principals of aviating (tongue, cheek, leg, nerve)
If a statistician in a major regulatory authority were moved when 'caught' analysing these figures - would that be a scandal? ?
So, yes, under some circumstances twins can actually be safer - the extent and the circumstances are often exaggerated.
Soggy said: "Just because there may have been no recorded instances of an engine failure when these profiles are being flown does not mean there never will - Mr Murphy will always be around to guarantee that. " - sure but if they have never been used and they increase risk in other ways then isn't it fair to look at them again?
If you are exposed in an aircraft which needs two engines both working then the risk is greater than had you only had one.
Old Man: I did express my surprise that noone had benefitted from the use of these profiles - and none had. Obviously you are now a big fan of them. Do you maintain that that was actually a ZERO risk event for you? Hopefully not! - what were you thinking doing a test over "houses or schools or buildings" anyway - or where your "houses schools or buidings" theoretical ones which fortunately, since you made them up, were no taller than 35ft?
Mind you you probably wouldn't make the news by hitting a theoretical building !
Old Man: you said (while being mildly insulting ... but fair enough): "or ask questions to gain that knowledge" - I thought I was asking: Has anyone had an engine failure during the climbing upwards and backwards bit (ie after hover and before CDP (or is it TDP?)) - I guess that's still no-one is it?
But seriously thanks for the education - it's true I had actually forgotten the EXPOSURE time concepts of these CAT B profiles and yes of course the risk is minimal - the greater benefit being derived from the prolonged Exposure to a Hostile Landing Environment - It's a clear example of a single engined aircraft being safer for a short phase of the flight but the twin probably being superior in view of the prolonged exposure time. (mind you.....)
If you just run the calculations in accordance with the published regulations you can compute the exposure time required to make a CAT A twin safer. It is suprisingly long. Don't make me go and look it up again..... I can't be arsed....
The table of statistics (pointed out by Nick Lappos) published on the twins/singles thread clearly shows the higher risk of twins.
Is there a big problem in the Gulf of Mexico from running singles?
- I don't think so.
Finally - yes I am recieving something of an education - in a subject which I do know something (though not much)about - I have actually dabbled at flying a couple of times - but I have to say I am partially tounge in check while pulling the odd leg and seem to have hit a raw nerve.... and I don't really want to offend against anyones 'pet theories' even if they are a perverted bastardisation of the principals of aviating (tongue, cheek, leg, nerve)
If a statistician in a major regulatory authority were moved when 'caught' analysing these figures - would that be a scandal?
?
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QMAX,
Yet again. I think you'll find that OMR was not carrying out a test over houses or whatever. He was merely pointing out that during a check flight, with the aircraft ballasted to the maximum allowable weight for the profile in the prevailing conditions, ON AN UPWARD AND REARWARD HELIPAD TAKE-OFF HE ACTUALLY DID SUFFER A REAL ENGINE FAILURE AT CDP (correct phraseology as it is a Category A/Performance Class 1, or equivalent, take-off). The reference to 35 feet is just standard for this type of take-off as the certificated profile calls for a flyaway with an allowable descent, which must nevertheless clear all obstacles on the continued take-off flightpath by a minimum vertical separation of 35 feet.
Having had a couple of engine failures in twins, which have always resulted in my being able to return to a site at which I was able to make a safe landing; and always in circumstances which would have caused me to make a survivable, but unsafe landing had I been in a single, I still can't see how a single would have been safer. None of these aircraft needed 2 engines, they just had them - or by 'need' do you mean that the aircraft is incapable of flight at, or near max gross mass, on one of its engines?
Yet again. I think you'll find that OMR was not carrying out a test over houses or whatever. He was merely pointing out that during a check flight, with the aircraft ballasted to the maximum allowable weight for the profile in the prevailing conditions, ON AN UPWARD AND REARWARD HELIPAD TAKE-OFF HE ACTUALLY DID SUFFER A REAL ENGINE FAILURE AT CDP (correct phraseology as it is a Category A/Performance Class 1, or equivalent, take-off). The reference to 35 feet is just standard for this type of take-off as the certificated profile calls for a flyaway with an allowable descent, which must nevertheless clear all obstacles on the continued take-off flightpath by a minimum vertical separation of 35 feet.
Having had a couple of engine failures in twins, which have always resulted in my being able to return to a site at which I was able to make a safe landing; and always in circumstances which would have caused me to make a survivable, but unsafe landing had I been in a single, I still can't see how a single would have been safer. None of these aircraft needed 2 engines, they just had them - or by 'need' do you mean that the aircraft is incapable of flight at, or near max gross mass, on one of its engines?
Qmax: you're not a pilot, you don't understand these things, you never will. Stick to what you're good at, whatever it is and confine your comments to that regime.
Your contributions are becoming embarrassing.
Your contributions are becoming embarrassing.
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soggyboxers, thank's for the reality check. i was under the impression that every takeoff was done up to 100 feet backwards as mentioned earlier in the profiles from Thomas coupling and DeltaFree. is the takeoff you mentioned classed as a cat A?
Old Man Rotor, i was looking for sombody to pick my thoughts on the matter of backwardly rising 100 feet. somebody said that one engine will slow the decent enough for vortex ring not to be an issue with one engine failure. my main issue was going backwards.
you said: I guess your way of doing this would have been to lift and transit forward over the houses or schools or buildings. you forgot to mention roads, parks and ovals. which ones did you fly over at 35 feet? and if you just lifted and transited foward would the time taken for the engine to fail have let you be in a posible one engine configeration? do you know what happend to the engine?
you also said> Yes the CAT A profile does work....and work well,
and> Offshore Approaches and Departures in every country that I have worked are never CAT A. does this mean you dont believe in using them either?
Old Man Rotor, i was looking for sombody to pick my thoughts on the matter of backwardly rising 100 feet. somebody said that one engine will slow the decent enough for vortex ring not to be an issue with one engine failure. my main issue was going backwards.
you said: I guess your way of doing this would have been to lift and transit forward over the houses or schools or buildings. you forgot to mention roads, parks and ovals. which ones did you fly over at 35 feet? and if you just lifted and transited foward would the time taken for the engine to fail have let you be in a posible one engine configeration? do you know what happend to the engine?
you also said> Yes the CAT A profile does work....and work well,
and> Offshore Approaches and Departures in every country that I have worked are never CAT A. does this mean you dont believe in using them either?
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vorticey,
No the offshore helideck take-off is not Group A, as there is a very short risk exposure time between rotating the nose forward and the tail clearing the edge of the helideck. It is also possible if the helideck is low, the aircraft is very heavy and the wind is light, that the aircraft may have to be ditched if it cannot be accelerated to Vtoss before reaching the water.
This also refers to what OMR was talking about with regard to offshore approaches and departures not being Cat A. Many offshore helidecks are not of a diameter large enough to comply with the size required for a Cat A helipad departure and even if they were, the payload losses resulting from the restricted weights permitted by these profiles render them commercially unacceptable. As the Class B profiles flown reduce exposure times to a minimum, most oil companies and regulatory authorities allow them to be used. This may well change with the advent of newer helicopters which have true Cat A performance on a single engine. However, they also rely on the fact that after leaving the deck there is a clear path over the sea for the continued take-off. This is not the case overland in e.g. EMS work, where a helicopter may be operating from a rooftop or a small field and then the upward and backward Category technique has to be used. You are quite right in assuming that the rate of descent on the remaining engine is sufficiently low that there is no danger of vortex ring. The rearward climb also allows the helipad to be retained in the pilots view at all times, making rejecting back on to the take-off spot fairly easy. The angle of climb is also sufficiently steep that it can be performed in a relatively limited area. Hope that helps to explain it a bit more.
No the offshore helideck take-off is not Group A, as there is a very short risk exposure time between rotating the nose forward and the tail clearing the edge of the helideck. It is also possible if the helideck is low, the aircraft is very heavy and the wind is light, that the aircraft may have to be ditched if it cannot be accelerated to Vtoss before reaching the water.
This also refers to what OMR was talking about with regard to offshore approaches and departures not being Cat A. Many offshore helidecks are not of a diameter large enough to comply with the size required for a Cat A helipad departure and even if they were, the payload losses resulting from the restricted weights permitted by these profiles render them commercially unacceptable. As the Class B profiles flown reduce exposure times to a minimum, most oil companies and regulatory authorities allow them to be used. This may well change with the advent of newer helicopters which have true Cat A performance on a single engine. However, they also rely on the fact that after leaving the deck there is a clear path over the sea for the continued take-off. This is not the case overland in e.g. EMS work, where a helicopter may be operating from a rooftop or a small field and then the upward and backward Category technique has to be used. You are quite right in assuming that the rate of descent on the remaining engine is sufficiently low that there is no danger of vortex ring. The rearward climb also allows the helipad to be retained in the pilots view at all times, making rejecting back on to the take-off spot fairly easy. The angle of climb is also sufficiently steep that it can be performed in a relatively limited area. Hope that helps to explain it a bit more.