Helicopter Performance
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Helicopter Performance
Is it possible to design a helicopter which can land and take off from a helipad 5m * 5m. The helicopter should be able to take off and land upto an altitude of 23000 ft.
Do a Hover - it avoids G
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Yes.
Whether you could afford it or whether it would also do whatever job you want done (apart from the takeoff and landing that is) are other matters.
Whether you could afford it or whether it would also do whatever job you want done (apart from the takeoff and landing that is) are other matters.
I think you will find that there have been`rescues` carried out in the Himalayas at or about that altitude,probably by AS Llamas or Mils,and an AS350B3,landed atop Everest,briefly,a couple of years ago.However ,the problem is mainly the approach/departure paths to the helipad,and all the topographical wind effects.It would also depend whether you were intending to drop-off `stuff` or pick-up,whether it was an isolated pad,ie on a pinnacle,or just an aiming point in a cleared area,as this would determine hovering `outside/inside` ground effect power requirements.I`ve been to 20kft in a Gazelle a few times for certification,and you are in a `coffin corner`,in that if you slow down below(guessing) 20 kts,you will run into loss of tail rotor control,and lose height; if you go for more speed(guess again) say 50 kts ,the rotor can be suffering compressibility effects;if you still can apply power to climb ,that margin can become very narrow;then of course if the windscreen is icing up inside,and you turn the heater up,you rob the engine of power so you`ll descend;and of course you need oxygen as well...
All these effects are similar to fixed wing a/c at 60k+,but magnified in a helo
,and then you have the descent to consider,as you can`t just dump the collective,as the RRPM will be off the clock in a second,into compressibility,and instability......I haven`t `googled` the OGE perf. of the K-MAX,Chinook,or some of the Kamovs,but they may have an edge at altitude over conventional helos....Hope that raises your spirits ....Syc
Anyway,a Harrier couldn`t do it,eh,John...
All these effects are similar to fixed wing a/c at 60k+,but magnified in a helo
,and then you have the descent to consider,as you can`t just dump the collective,as the RRPM will be off the clock in a second,into compressibility,and instability......I haven`t `googled` the OGE perf. of the K-MAX,Chinook,or some of the Kamovs,but they may have an edge at altitude over conventional helos....Hope that raises your spirits ....Syc
Anyway,a Harrier couldn`t do it,eh,John...
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I have asked this question because most of the manufactures are unable to do the research on this issue. I and my pilots are landing everyday at an altitude of 21500-22000 ft (DA). Pressure altimeter readings during IGE are 19800 ft. We are searching for some helicopters who can land at thses altitudes. If anybody can provide some extrapolated performance graphs. !!!!
I'd have thought that any manufacturer can do research on the issue, but they may not wish to.
It may be a case of going back to some of the basic helicopter performance texts such as Prouty or Newman and deriving some approximate figures yourself.
Not, of course, that you can then use them, but it'll at-least give you an idea of what the question is.
G
It may be a case of going back to some of the basic helicopter performance texts such as Prouty or Newman and deriving some approximate figures yourself.
Not, of course, that you can then use them, but it'll at-least give you an idea of what the question is.
G
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Test sites?
The 'problem' may be that there are no test sites at those altitudes.
Development of the perf charts for a helo isn't a 2 minute job and requires special facilities in order to approach the limit cases safely.
In the western hemisphere most of the testing seems to be done at Leadville at just under 10000 ft and that's the highest airfield in North America, if there are other places that could be used I am sure they would be, but I have heard of some locations in the Andes being used.
DM
Development of the perf charts for a helo isn't a 2 minute job and requires special facilities in order to approach the limit cases safely.
In the western hemisphere most of the testing seems to be done at Leadville at just under 10000 ft and that's the highest airfield in North America, if there are other places that could be used I am sure they would be, but I have heard of some locations in the Andes being used.
DM
Gabroo,apologies for not having read your profile before posting,but you are obviously aware of all the problems.I have just looked at the Kaman K-Max site,and projecting the perf. graphs indicates some payload capability.However,manufacturers brochures should only be used as padding under helicopter seats;I would suggest however ,that there would be interest in approaching the Company,Kaman to see if they have any further performance data,or would be interested in your proposals/ideas.I only use the K-Max as an example,as it is very specialised,single pilot,big engine,no tail-rotor problems at lo-speed,no hydraulics,rugged construction;I`ve not flown one,but you may try `Rotorheads` to see if anyone has differing opinions/experience.
Alternatively,you could find an old Lama frame,get a g/box and rotor from a 355/365,find a big engine,split tail-rotor like an Apache,and Go-Fly !!!!
Alternatively,you could find an old Lama frame,get a g/box and rotor from a 355/365,find a big engine,split tail-rotor like an Apache,and Go-Fly !!!!
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Dear Gheghis
In my opinion it may not be as simple as it sounds. The helicopter design philoshy is based on its intended use (performance envelope). It has been observed in most of the helicopters which I had flown that there was sudden deterioration in the performance when reaching at the edge of its flight envelope. This was either because of the engine design(thermal/power margin) or because of some airframe related(Rudder/control margins).
regards and happy hovering
In my opinion it may not be as simple as it sounds. The helicopter design philoshy is based on its intended use (performance envelope). It has been observed in most of the helicopters which I had flown that there was sudden deterioration in the performance when reaching at the edge of its flight envelope. This was either because of the engine design(thermal/power margin) or because of some airframe related(Rudder/control margins).
regards and happy hovering
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Designing a helicopter that can land and takeoff from a 5 x 5 meter pad at an altitude of 23000 feet would pose no insurmountable engineering challenges. The design difficulty depends greatly on the desired performance (e.g. useful load, speed, endurance, environmental envelope) at that altitude; but that is true at any altitude. Helicopters cannot, at current levels of technology, be designed for excellent performance at all altitudes.
This is more an economic than an engineering problem. There is little demand to operate at those altitudes. Individual unit price for a helicopter meeting the altitude performance you have asked about would be greater than most governments would be willing to pay.
There is not a manufacturer in the world that has not been approached by the Indian government for a helicopter that can operate at high mission altitudes. Unfortunately the Indian government and/or business sector have not proposed a single, well defined performance criterion for the high altitude mission; nor has it demonstrated a willingness to pay for a helicopter designed for very high altitude performance.
This is more an economic than an engineering problem. There is little demand to operate at those altitudes. Individual unit price for a helicopter meeting the altitude performance you have asked about would be greater than most governments would be willing to pay.
There is not a manufacturer in the world that has not been approached by the Indian government for a helicopter that can operate at high mission altitudes. Unfortunately the Indian government and/or business sector have not proposed a single, well defined performance criterion for the high altitude mission; nor has it demonstrated a willingness to pay for a helicopter designed for very high altitude performance.
Dear Gheghis
In my opinion it may not be as simple as it sounds. The helicopter design philoshy is based on its intended use (performance envelope). It has been observed in most of the helicopters which I had flown that there was sudden deterioration in the performance when reaching at the edge of its flight envelope. This was either because of the engine design(thermal/power margin) or because of some airframe related(Rudder/control margins).
regards and happy hovering
In my opinion it may not be as simple as it sounds. The helicopter design philoshy is based on its intended use (performance envelope). It has been observed in most of the helicopters which I had flown that there was sudden deterioration in the performance when reaching at the edge of its flight envelope. This was either because of the engine design(thermal/power margin) or because of some airframe related(Rudder/control margins).
regards and happy hovering
G
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Dear aviators
I just wanted to learn whether it is really a challenge or just economics. I agree with Genghis and other professionals. I would like to add that most of the helicopters which have flown at test sites or anywhere at those altitudes (light Utility classs) have same capability, whether the helicopter was of 1960s or 2003.
I just wanted to learn whether it is really a challenge or just economics. I agree with Genghis and other professionals. I would like to add that most of the helicopters which have flown at test sites or anywhere at those altitudes (light Utility classs) have same capability, whether the helicopter was of 1960s or 2003.
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One of the issues with this is the certification criteria to claim hover performance - civil flight manual performance is not based solely on the ability to hover - it has to be a height from which you can transition into forward flight over a flat surface and when hitting the ground vortex roll up (for lack of a better word), you won't descend and hit the ground.
Also, controllability has to be demonstrated in all quadrants to 17 knots of wind.
The problem is to find a way to demonstrate / test for these conditions.
And a more practical problem, if you're coming in to land at this helipad at that altitude - you'll need more power to stop the rate of descent than you will to hover. Similarly, to takeoff without a level surface to fly over, you'll need more power than to hover over the small surface. But - how much more power???
tricky problem, and one where the certification criteria don't help much.
Also, controllability has to be demonstrated in all quadrants to 17 knots of wind.
The problem is to find a way to demonstrate / test for these conditions.
And a more practical problem, if you're coming in to land at this helipad at that altitude - you'll need more power to stop the rate of descent than you will to hover. Similarly, to takeoff without a level surface to fly over, you'll need more power than to hover over the small surface. But - how much more power???
tricky problem, and one where the certification criteria don't help much.
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High Alt landings
You haven;t specified the payload. Moreover, a helicopter designed for the conditions you mentioned would probably have poor performance at. say, sea level. There is always a pay off. Designing choppers for specific tasks is not an insurmountable problem. However, the more demanding the requirements, the more ad-hoc the design and the less likelihood of its finding a place in general commercial use.
The Heli-pad size would dictate the track of the bird, but what of the rotor disc? If you want a smaller rotor disc, the disc loading (with associated issues) would be high.
The Heli-pad size would dictate the track of the bird, but what of the rotor disc? If you want a smaller rotor disc, the disc loading (with associated issues) would be high.
