Offshore Helideck Ops
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Well, always better than : "Land at your own discretion"
or
"DECKCLEARFORLANDINGCREWSTANDINGBY!" in speed language with 5 other aircraft asking for their deck clearances
DJG
or
"DECKCLEARFORLANDINGCREWSTANDINGBY!" in speed language with 5 other aircraft asking for their deck clearances
DJG
Join Date: Dec 2002
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I agree with Hummingfrog. Who thought this up. It is obviously nobody who flies offshore. Why use a 4 syllable word when a one syllable word was more than adequate.
I thought that it was sensible not to use the same word in the question as the answer. We do not now call "ready for take off" but "ready for departure" at an airfield to stop someone thinking that a call for "take off" was their permission to take off.
Most off the N sea is divided into sectors with each rig in that sector on the same frequency. It is not unusual for 2 helicopters to be making their approaches to different rigs at the same time on the same frequency.
It will be possible for one helicopter to mistake the others request " Is the DECK AVAILABLE FOR LANDING" for the answer "affirm DECK AVAILABLE FOR LANDING"
Lets go for Hummingfrog's suggestion of "Deck clear" and "deck unavailable" two distinct phrases
332M
I thought that it was sensible not to use the same word in the question as the answer. We do not now call "ready for take off" but "ready for departure" at an airfield to stop someone thinking that a call for "take off" was their permission to take off.
Most off the N sea is divided into sectors with each rig in that sector on the same frequency. It is not unusual for 2 helicopters to be making their approaches to different rigs at the same time on the same frequency.
It will be possible for one helicopter to mistake the others request " Is the DECK AVAILABLE FOR LANDING" for the answer "affirm DECK AVAILABLE FOR LANDING"
Lets go for Hummingfrog's suggestion of "Deck clear" and "deck unavailable" two distinct phrases
332M
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This has irritated me no end . Its another imposed decision from on High....made without consultation of the people who fly in the North Sea. If it's not broke.......WHY? During shuttles there are often other aircraft in the same field on the the same freq. Short, sharp calls are the norm....not this long winded waffle!
We often do 25+ sectors in a day.
Another example of the "we know best" school of legislation.
We often do 25+ sectors in a day.
Another example of the "we know best" school of legislation.
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JimL, I read your other post regarding the HOMP report with interest and wanted to express my views:
HOMP is the latest version of the North Sea's 'Emperor's New Clothes'.
If you think an algorithm based on Cooper-Harper ratings can assess workload without the qualitative input of a calibrated human, it goes to show how little is understood about what is being done here. Give industry a fraction of what is being spent on this white elephant in the form of additional training hours and efforts training-the-trainer, and I assure you the rate of incidents will reduce.
This is another example of what the UK 'committee syndrome' spawns, regurgitating the same issues year after year achieving very little in real-world operational safety matters and when money is spent, it is misdirected.
Rig design for helicopter operations is not rocket science, and neither is landing a helicopter on a rig. Developing HOMP for turbulence assessment is nothing more than idle intellectual musings.
If HOMP has been recommended for inclusion in ICAO Annex 6 Part III (tell me it ain't so!), my bet is was done so by someone who knows little of operating outside of the North Sea. To put this forward for inclusion in an international document is waaaay too premature.
It isn't progress JimL, it's misidentification of the real issues. This whole subject is also a case-in-point of why the Americans have a helicopter manufacturing industry and the British don't.
Disregard the last sentence. I had the urge to finish on an inflammatory note.
HOMP is the latest version of the North Sea's 'Emperor's New Clothes'.
If you think an algorithm based on Cooper-Harper ratings can assess workload without the qualitative input of a calibrated human, it goes to show how little is understood about what is being done here. Give industry a fraction of what is being spent on this white elephant in the form of additional training hours and efforts training-the-trainer, and I assure you the rate of incidents will reduce.
This is another example of what the UK 'committee syndrome' spawns, regurgitating the same issues year after year achieving very little in real-world operational safety matters and when money is spent, it is misdirected.
Rig design for helicopter operations is not rocket science, and neither is landing a helicopter on a rig. Developing HOMP for turbulence assessment is nothing more than idle intellectual musings.
If HOMP has been recommended for inclusion in ICAO Annex 6 Part III (tell me it ain't so!), my bet is was done so by someone who knows little of operating outside of the North Sea. To put this forward for inclusion in an international document is waaaay too premature.
It isn't progress JimL, it's misidentification of the real issues. This whole subject is also a case-in-point of why the Americans have a helicopter manufacturing industry and the British don't.
Disregard the last sentence. I had the urge to finish on an inflammatory note.
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Helideck operations - variation in ground cushion with deck size??
Here's a question for all you budding theorists out there.
Looking at offshore operations to raised helidecks - can anybody provide me with a "simple" calculation to illustrate the variation in ground cushion effect with the reduction in helideck size? eg. starting off with a helideck size of 1.5D and reducing down to 0.75D or less.
Thanks in advance for any contributions and Seasons Greetings to one and all
Looking at offshore operations to raised helidecks - can anybody provide me with a "simple" calculation to illustrate the variation in ground cushion effect with the reduction in helideck size? eg. starting off with a helideck size of 1.5D and reducing down to 0.75D or less.
Thanks in advance for any contributions and Seasons Greetings to one and all
Last edited by flyer43; 24th Dec 2004 at 07:25.
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If you mean by operations then assuming it's commercial how small do you want to go and still remain legal and also be covered by insurance?
If it's a Cat A operation it will tell you the size in the RFM for each type and the deck may end up being bigger than 1.5D.
More details would help.
If it's a Cat A operation it will tell you the size in the RFM for each type and the deck may end up being bigger than 1.5D.
More details would help.
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It's not so much a question of legality - this is purely a question about helicopter aerodynamics. Maybe if I asked the question in a different way - Is there a simple way of expressing the reduction in ground cushion effect between a helicopter sitting nicely in the middle of a large helideck compared to one which is hovering with an increasing amount of rotor disc extending beyond the helideck edge. i.e. What is the difference in power required to maintain the same hover height with respect to the helideck?
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Helideck operations - variation in ground cushion with deck size
Rotor dia say 30 feet Diameter of pad (assuming round pad) say 30 feet. power required to hover at 15 feet is approx two thirds of that to hover out of ground effect. On the basis that only the outer half of your blades are producing significant lift, any reduction in the size of the pad from that of your rotor diameter will greatly reduce your lift and increase your induced power requirement. Look at it this way. If your rotor span is 30 feet and your pad is 25feet, at a 15 foot hover directly over the pad you now have the outer two feet six inches of each blade that are no longer in ground effect but are obviously providing the same lift as they do out of ground effect therefore when I am sober and not rambling on like a pratt I will produce a graph which you can pin on your windscreen which can be refered to whilst executing a 30feet dia helipad landing. You will need to carry out some mathematical work to evaluate the graph , this is best done by holding a 30inch pencil bitween ones teeth to allow unimpeded access to the graph stuck on the screen . Wishing you a happy and safe Christmas Bug.
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Nice question!
The max ground effect is about 20% (you reduce power by about 20% when in very low IGE vice OGE). For smaller decks, where the rotor is not fully IGE, the effect is rapidly reduced, I'll bet, but I have no data. If one is squarely over a 1D pad, the effect should be just about 100%, since the rotor wake contracts to a tighter diameter than the rotor.
As rotordevheli says, the max velocities are at the tips, so one would believe a half Diameter pad would produce very much less than half the IGE recovery (also, the area of a half diameter pad is only 25% of the total disk.)
I doubt that anyone has actually measured the effect, though.
The max ground effect is about 20% (you reduce power by about 20% when in very low IGE vice OGE). For smaller decks, where the rotor is not fully IGE, the effect is rapidly reduced, I'll bet, but I have no data. If one is squarely over a 1D pad, the effect should be just about 100%, since the rotor wake contracts to a tighter diameter than the rotor.
As rotordevheli says, the max velocities are at the tips, so one would believe a half Diameter pad would produce very much less than half the IGE recovery (also, the area of a half diameter pad is only 25% of the total disk.)
I doubt that anyone has actually measured the effect, though.
Last edited by NickLappos; 25th Dec 2004 at 02:30.
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It' s not very scientific but I've had students land on a narrow bank with steep drop off fore and aft. Naturally they are more worried about falling off the bank but it's interesting to note that the power requirement in a piston Enstrom is only about one to one and a half inches less MP than for OGE so it obviously affects greatly.
There is no noticeable pitch effect so I presume the (90 degree precessed) increased lift from the left and right sections of the disc cancel out.
Will a similar cancellation occur on a small square pad ? I supposed proximity to superstructure and wind will affect greatly also ?
There is no noticeable pitch effect so I presume the (90 degree precessed) increased lift from the left and right sections of the disc cancel out.
Will a similar cancellation occur on a small square pad ? I supposed proximity to superstructure and wind will affect greatly also ?
Working on a formula: how keen is that (who said sad?????)
Happy Christmas
Happy Christmas
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Thanks for the feedback so far. I know the practical answer to my question having spent many years flying to offshore installations and several years as a flying instructor at a cpl(h) school where sloping ground landings with students certainly made you more than aware of the difference in power requirements from working with a flat surface - albeit a much larger one than the average offshore platform.
If anybody is actually sad enough to work out even a very basic formula in response to my original question I would be very interested and very grateful.
BUG - I hope that your hangover is cured by now, although the big New Year one is imminent!! When you eventually recover next year I'd be interested in the graphs you were talking about - might be difficult to make the measurements with a pencil between my teeth while holding a stable hover over a moving helideck though....
Wishing you all the very best for 2005
If anybody is actually sad enough to work out even a very basic formula in response to my original question I would be very interested and very grateful.
BUG - I hope that your hangover is cured by now, although the big New Year one is imminent!! When you eventually recover next year I'd be interested in the graphs you were talking about - might be difficult to make the measurements with a pencil between my teeth while holding a stable hover over a moving helideck though....
Wishing you all the very best for 2005
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Big D sagas
Have noticed that with something like a 61 that just to confound your best estimates at performance on the offshore deck (twin engine HOGE weight) there are times when at zero wind you just can't make it. Reckon this is because some of the surrounding vertical structures are contributing a bit of recirculation on part of the disc. There were certainly many occasions in the (bad) old days when you just air taxied off the deck and converted height to speed. Anybody have similar experiences?
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Geoffersincornwall,
To understand your observation more clearly, can you tell us what you "just can't make" Is it an OGE hover, towering takeoff, or something else?
Thanks,
N
To understand your observation more clearly, can you tell us what you "just can't make" Is it an OGE hover, towering takeoff, or something else?
Thanks,
N
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This is totally anecdotal and probably worthless, but it made me scratch my head a bit. The popular theories may be wrong.
A long time ago when I first started flying offshore (GOM), I wondered about this very thing, i.e. how much ground cushion does the platform provide? I was flying a 206B while based on a tall, three-story, slab-sided quarters building that measured 50'X70'. The entire roof was the helideck, and the surrounding fence was bare chain link and therefore of no ground-cushion value.
In an experimental mood (and being dumber than a box of rocks), I decided to see if I could measure any torque difference or cyclic displacement change with the helicopter hovering half-on and half-off the deck. I chose a calm summer day - not hard to do.
With just me in the ship and with the disk dead-center over the deck, I was hovering right around 72%Q. I moved over to the edge and positioned the B-model exactly half-on/half-off. To my surprise, the torque stayed right at 72%. The cyclic *seemed* to be in the same place as far as I could tell (but then I couldn't accurately measure it). Puzzled, I moved back over the pad: 72%. Back to the half-off position: 72%.
Nervous as I was, flirting with disaster like that I did not experiment by moving too much further outward to see where the transition from IGE to OGE was noticed. In retrospect, I wish that I had quantified it, but my uniform shirt at the time did not have a nametag that said "N. Lappos." And I was afraid one of our "big ships" would be flying over with the guys looking down and going, "What the hell is that B-model doing hovering half-off the deck? Get the Chief Pilot on the phone!"
I was pretty confused, but what this seemed to tell me was that the effects of the ground cushion on takeoff probably extended out at least half-a-disk or so (genius!). Conversely, the same probably held true for landing, although I confess that this is an assumption (with all that entails).
Shortly afterward, I moved on to bigger aircraft and other (smaller) platforms, my "playing around" decreased and I stopped asking myself questions like, "What happens if you hover half-on and half-off a platform?"
A long time ago when I first started flying offshore (GOM), I wondered about this very thing, i.e. how much ground cushion does the platform provide? I was flying a 206B while based on a tall, three-story, slab-sided quarters building that measured 50'X70'. The entire roof was the helideck, and the surrounding fence was bare chain link and therefore of no ground-cushion value.
In an experimental mood (and being dumber than a box of rocks), I decided to see if I could measure any torque difference or cyclic displacement change with the helicopter hovering half-on and half-off the deck. I chose a calm summer day - not hard to do.
With just me in the ship and with the disk dead-center over the deck, I was hovering right around 72%Q. I moved over to the edge and positioned the B-model exactly half-on/half-off. To my surprise, the torque stayed right at 72%. The cyclic *seemed* to be in the same place as far as I could tell (but then I couldn't accurately measure it). Puzzled, I moved back over the pad: 72%. Back to the half-off position: 72%.
Nervous as I was, flirting with disaster like that I did not experiment by moving too much further outward to see where the transition from IGE to OGE was noticed. In retrospect, I wish that I had quantified it, but my uniform shirt at the time did not have a nametag that said "N. Lappos." And I was afraid one of our "big ships" would be flying over with the guys looking down and going, "What the hell is that B-model doing hovering half-off the deck? Get the Chief Pilot on the phone!"
I was pretty confused, but what this seemed to tell me was that the effects of the ground cushion on takeoff probably extended out at least half-a-disk or so (genius!). Conversely, the same probably held true for landing, although I confess that this is an assumption (with all that entails).
Shortly afterward, I moved on to bigger aircraft and other (smaller) platforms, my "playing around" decreased and I stopped asking myself questions like, "What happens if you hover half-on and half-off a platform?"
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Bravo73 seems like you just lost an opportunity to remain quiet.
I did notice that itīs been 6 years since the last post, Helideck Ops continue to be a relevant topic though, at least for anyone flying Offshore.
I did notice that itīs been 6 years since the last post, Helideck Ops continue to be a relevant topic though, at least for anyone flying Offshore.