North Sea Weather Considerations
Join Date: Jul 2005
Location: UK
Posts: 48
Likes: 0
Received 0 Likes
on
0 Posts
Jigsaw is a BP project, it covers some areas based from Sumburgh and the Miler Platform. Cover is provided for more than just BP platforms I thnk by arrangement but not necessarialy by default.
They will launch for any emergency as requested, but may not be providing standby cover for a specific platform. So if it is Bond flights going to nearby BP platforms then that may be a reason they have flights and others don't.
Although the Miller machine will be likely be in Aberdeen with strong winds offshore due to starting limitations, so that area may be without air cover during those times.
They will launch for any emergency as requested, but may not be providing standby cover for a specific platform. So if it is Bond flights going to nearby BP platforms then that may be a reason they have flights and others don't.
Although the Miller machine will be likely be in Aberdeen with strong winds offshore due to starting limitations, so that area may be without air cover during those times.
Join Date: Dec 2002
Location: UK
Posts: 18
Likes: 0
Received 0 Likes
on
0 Posts
Just to add to the subject,if your shut down limits are say 40 knots(I assume to stop damage if the rotors sail)how do you stand if wind speed is 55 knots and you have to shut down due to mechanical failure
If the wind was "clean" coming from the front of the helicopter without having got "chopped up" through a drilling derrick or other superstructure and not curling up over the edge of the helideck after "damming" against the side of the platform, then shutting down in very strong winds would probably be possible without damage. Even so, I would still feel like ducking my head when applying the rotor brake.
If the wind was very turbulent, but I was forced to stop the rotors in an emergency and time permitted, I might ask the deck crew to lash the helicopter to the deck with straps. Then I might get everyone including me to evacuate the helicopter and the helideck before the fuel ran out and the rotors stopped by themselves.
If I was forced to stop the rotors immediately in strong winds and turbulence, I would instruct the deck crew and all personnel, including my fellow pilot, to get clear of the helideck while I stopped the engines and applied the rotor brake. Then I would duck my head very low and hope.
It would surprise me if my statements don't trigger a torrent of different opinions from professional pilots and others, but nothing definite can be written for suggested actions in extreme circumstances. Bear in mind that such happenings are extremely rare.
If the wind was very turbulent, but I was forced to stop the rotors in an emergency and time permitted, I might ask the deck crew to lash the helicopter to the deck with straps. Then I might get everyone including me to evacuate the helicopter and the helideck before the fuel ran out and the rotors stopped by themselves.
If I was forced to stop the rotors immediately in strong winds and turbulence, I would instruct the deck crew and all personnel, including my fellow pilot, to get clear of the helideck while I stopped the engines and applied the rotor brake. Then I would duck my head very low and hope.
It would surprise me if my statements don't trigger a torrent of different opinions from professional pilots and others, but nothing definite can be written for suggested actions in extreme circumstances. Bear in mind that such happenings are extremely rare.
I have started and stopped a Wessex in a 70kt wind with absolutely no problem - very little blade sail. The wind was, however, completely laminar with very little gust differential. it is the gust differential that will cause the blades to sail. All the N Sea helicopters I have flown have had a 55kt max wind for shutdown (within a reasonable arc of the nose ie +/- 20 degs). In emergency some helicopter flight manuals advise putting the wind off the nose to try and arrange for the downward sailing blade to pass over the tail before it reaches its lowest point. Which side depends on US or French design.
If you have a mechanical failure then you are committed to shutting down though as one pilot I know can testify in a S61 you will have to duck and then find out how to shut down the engines as the HP cocks have disappeared
HF
If you have a mechanical failure then you are committed to shutting down though as one pilot I know can testify in a S61 you will have to duck and then find out how to shut down the engines as the HP cocks have disappeared
HF
S76 rotor brake
Max windspeed for releasing the rotor brake is steady 40kts, or gusting to 50kts. For normal operation the rotor brake should not be applied until the rotor speed decreases to between 50% and 60% Nr.
Join Date: Aug 2007
Location: uk
Posts: 70
Likes: 0
Received 0 Likes
on
0 Posts
Although it is easy to say 'what if'..
If you are flying ABZ to ESB and the destination rig is in 'wave rescue limits' but the majority of the 250 mile transit is out of limits with no 'Scoop' or anything to rescue you ( apart from SAR ) now what is your decision?
The thoughts on this thread seem to apply only to destination weather, where at least there is some capability - FRC , Scoop - (agreed useless ) 95% of the trip you will have nothing.
I intend to agree with Coatimundi - equal misery or happiness for all.
I am glad I retired.
If you are flying ABZ to ESB and the destination rig is in 'wave rescue limits' but the majority of the 250 mile transit is out of limits with no 'Scoop' or anything to rescue you ( apart from SAR ) now what is your decision?
The thoughts on this thread seem to apply only to destination weather, where at least there is some capability - FRC , Scoop - (agreed useless ) 95% of the trip you will have nothing.
I intend to agree with Coatimundi - equal misery or happiness for all.
I am glad I retired.
Join Date: Nov 2007
Location: Glasgow
Posts: 87
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Hummingfrog
In emergency some helicopter flight manuals advise putting the wind off the nose to try and arrange for the downward sailing blade to pass over the tail before it reaches its lowest point.
He said "off the nose" not "on the nose," and the stated which side would vary with US/French type. Much as you have described....
Join Date: Aug 2003
Location: Sale, Australia
Age: 80
Posts: 3,832
Likes: 0
Received 0 Likes
on
0 Posts
What are the limits for the S76,there blades look low all the time.?????
The risk of damage on Super Puma family is more to do with head damage or what happens after rotors have stopped - a rotor blade has been known to sail up to nearly 90 degrees in a gust after shutdown, then fall back down onto droop stop (coning stops having previously been trashed!) whilst pilots are still wondering how to secure the blades.
There have been plenty of cases of keeping the thing running on deck by pumping in fuel, pending an abatement of wind to allow shutdown. Lots of coffee and a shift system required by the pilots!
Interestingly a certain oil company would not allow departure with rotor brake inoperative (its allowed in MEL) in case a/c had to shut down offshore, but were quite happy to allow operation beyond the RFM shutdown limits.
On the subject of rescue, current thinking is that the highest probability of ending up in the water occurs in the vicinity of the destination. Perhaps due to engine failure, perhaps due to crew error, but anyway safety margin is probably less during arrival and departure phase. In the history of the N Sea Super Puma, there has never been a survivable ditching due to a failure en-route (TIGK lightning strike was pretty close to the offshore installation IIRC) so this thinking is borne out by experience, even if perhaps it doesn't seem that logical on first inspection.
HC
There have been plenty of cases of keeping the thing running on deck by pumping in fuel, pending an abatement of wind to allow shutdown. Lots of coffee and a shift system required by the pilots!
Interestingly a certain oil company would not allow departure with rotor brake inoperative (its allowed in MEL) in case a/c had to shut down offshore, but were quite happy to allow operation beyond the RFM shutdown limits.
On the subject of rescue, current thinking is that the highest probability of ending up in the water occurs in the vicinity of the destination. Perhaps due to engine failure, perhaps due to crew error, but anyway safety margin is probably less during arrival and departure phase. In the history of the N Sea Super Puma, there has never been a survivable ditching due to a failure en-route (TIGK lightning strike was pretty close to the offshore installation IIRC) so this thinking is borne out by experience, even if perhaps it doesn't seem that logical on first inspection.
HC
Join Date: Nov 2007
Location: Glasgow
Posts: 87
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by 212man
Much as you have described....
Originally Posted by Hummingfrog
arrange for the downward sailing blade to pass over the tail before it reaches its lowest point.
Shutting an AS332L down in gusting 65kts prior to the 105 rotor brake being fitted got your attention. At least the Aux Hyd pump allowed you to fly the blades past the cockpit. And then the rotor brake slips as you are trying to fit the last blade sock on which has been made a bit small width-wise.
Memories!
Join Date: Dec 2003
Location: Scotland
Posts: 261
Likes: 0
Received 0 Likes
on
0 Posts
Getting back to the thread subject...
As HC states, the current thinking is that an accident will occur near an installation. The PFEER regulations only cover the area around an installation up to 500m. Oil installation operators have to follow PFEER regs to provide a 'good chance of recovery' in the case of a ditching, getting all the survivors to a 'place of safety' within two hours.
There is nothing in current regulations covering the transit from onshore to an offshore installation. Perhaps this should be addressed! Reading the TSB of Canada report on the Cougar S92 accident in 2009, I feel the following recommendation to be rather pertinent!
4.2.2 Safe Ditching and Successful Evacuation
Overwater helicopter operations transporting passengers to and from offshore oil and gas installations occur with the knowledge that an emergency situation may arise requiring a forced landing or ditching. In such circumstances the first priority must be preservation of life and safety of the passengers and crew.
Most helicopters in use to support the global offshore oil and gas industry, including the S-92A, have an emergency flotation system (EFS) which provides adequate ditching stability in "reasonably probable water conditions" of at least sea state 4 WMO and is intended to keep the helicopter upright while occupants escape to the life rafts.
However, helicopters frequently operate over water where the conditions exceed sea state 4 WMO. For instance, in the waters off Newfoundland, statistics from Environment Canada indicate that sea state 4 is exceeded approximately 50% of the time over the course of the entire year, and 83% of the time between December and February. Sea state 6 WMO, by comparison, is exceeded much less frequently; 3.3% over the year and 8.9% between December and February.
Twin-engine helicopters typically have a high center of gravity because of the weight of the engines and the main rotor gearbox located on the cabin roof. Consequently, there is a strong likelihood that these helicopters will capsize after ditching unless they are equipped with an EFS which is appropriate for the prevailing sea state.
When EFS systems do not operate successfully, twin-engine helicopters invariably turn upside down, leading to complete flooding of the cabin and immersion of all doors and windows. Escape is very difficult because all escape routes are submerged and occupants who do not escape from the cabin within a matter of seconds will drown.
Although some steps have been taken in Newfoundland to ensure EFS capability for sea states beyond sea state 4, helicopter crews and passengers in Canada remain at risk where helicopters are operated over sea states exceeding the capability of the EFS.
Therefore, the Board recommends that
Transport Canada prohibit commercial operation of Category A transport helicopters over water when the sea state will not permit safe ditching and successful evacuation.
A11-03
As the 'demonstrated' limit of the floation equipment of the EC225 is 6m, should commercial offshore flights even be dispatched when the sea state is 6m or more? Discuss!!
bondu
As HC states, the current thinking is that an accident will occur near an installation. The PFEER regulations only cover the area around an installation up to 500m. Oil installation operators have to follow PFEER regs to provide a 'good chance of recovery' in the case of a ditching, getting all the survivors to a 'place of safety' within two hours.
There is nothing in current regulations covering the transit from onshore to an offshore installation. Perhaps this should be addressed! Reading the TSB of Canada report on the Cougar S92 accident in 2009, I feel the following recommendation to be rather pertinent!
4.2.2 Safe Ditching and Successful Evacuation
Overwater helicopter operations transporting passengers to and from offshore oil and gas installations occur with the knowledge that an emergency situation may arise requiring a forced landing or ditching. In such circumstances the first priority must be preservation of life and safety of the passengers and crew.
Most helicopters in use to support the global offshore oil and gas industry, including the S-92A, have an emergency flotation system (EFS) which provides adequate ditching stability in "reasonably probable water conditions" of at least sea state 4 WMO and is intended to keep the helicopter upright while occupants escape to the life rafts.
However, helicopters frequently operate over water where the conditions exceed sea state 4 WMO. For instance, in the waters off Newfoundland, statistics from Environment Canada indicate that sea state 4 is exceeded approximately 50% of the time over the course of the entire year, and 83% of the time between December and February. Sea state 6 WMO, by comparison, is exceeded much less frequently; 3.3% over the year and 8.9% between December and February.
Twin-engine helicopters typically have a high center of gravity because of the weight of the engines and the main rotor gearbox located on the cabin roof. Consequently, there is a strong likelihood that these helicopters will capsize after ditching unless they are equipped with an EFS which is appropriate for the prevailing sea state.
When EFS systems do not operate successfully, twin-engine helicopters invariably turn upside down, leading to complete flooding of the cabin and immersion of all doors and windows. Escape is very difficult because all escape routes are submerged and occupants who do not escape from the cabin within a matter of seconds will drown.
Although some steps have been taken in Newfoundland to ensure EFS capability for sea states beyond sea state 4, helicopter crews and passengers in Canada remain at risk where helicopters are operated over sea states exceeding the capability of the EFS.
Therefore, the Board recommends that
Transport Canada prohibit commercial operation of Category A transport helicopters over water when the sea state will not permit safe ditching and successful evacuation.
A11-03
As the 'demonstrated' limit of the floation equipment of the EC225 is 6m, should commercial offshore flights even be dispatched when the sea state is 6m or more? Discuss!!
bondu
should commercial offshore flights even be dispatched when the sea state is 6m or more? Discuss!!
Secondly its surely about probabilities not absolutes? Certification rules for critical items are based around 10^-8 so even the official rules don't guarantee absolute safety (how could they, unless we stayed in the hangar). If you have a look at the history of the industry and see how many survivable ditching there were en-route, then factor in that such a ditching has to happen with sea states out of limits to be catastrophic, I think it would be well within certification safety limits to fly on the odd day with >6m waves.
There is no point in being ultra safe in one particular element of the whole thing, when other areas are less safe (unless it can be done with little or no cost/impact on the operation).
HC
Join Date: Sep 2008
Location: Croydon
Posts: 285
Likes: 0
Received 0 Likes
on
0 Posts
I think it would be well within certification safety limits to fly on the odd day with >6m waves.
Join Date: Oct 2006
Location: US
Posts: 41
Likes: 0
Received 0 Likes
on
0 Posts
Sea State or Wave Metre Height?
Is 225 or S92 good for Sea State 6 or 6 metre waves? And if it is based on sea state; which scale Beaufort or Douglas? See table below
The World Meteorological Organization (WHO) sea state code largely adopts the 'wind sea' definition of the Douglas Sea Scale.
WMO Sea State Code Wave Height (meters) Characteristics
0 0 Calm (glassy)
1 0 to 0.1 Calm (rippled)
2 0.1 to 0.5 Smooth (wavelets)
3 0.5 to 1.25 Slight
4 1.25 to 2.5 Moderate
5 2.5 to 4 Rough
6* 4 to 6* Very rough
7 6 to 9 High
8 9 to 14 Very high
9 Over 14 Phenomenal
*Beaufort Scale Sea State 6 is only 3-4 metre Wave Heights.
The World Meteorological Organization (WHO) sea state code largely adopts the 'wind sea' definition of the Douglas Sea Scale.
WMO Sea State Code Wave Height (meters) Characteristics
0 0 Calm (glassy)
1 0 to 0.1 Calm (rippled)
2 0.1 to 0.5 Smooth (wavelets)
3 0.5 to 1.25 Slight
4 1.25 to 2.5 Moderate
5 2.5 to 4 Rough
6* 4 to 6* Very rough
7 6 to 9 High
8 9 to 14 Very high
9 Over 14 Phenomenal
*Beaufort Scale Sea State 6 is only 3-4 metre Wave Heights.
Join Date: Oct 2011
Location: YBBN
Age: 78
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
Why Things are Different from Field to Field
Sorry I’m a bit late on this thread but I’ve only just joined.
The intent of the PFEER, and other Regulations for Offshore Installations, is that you have to minimise the reasonably foreseeable risks to a level that is as low as is reasonably practicable (ALARP).
The identification of reasonably foreseeable risks is the easy part. Its reasonably foreseeable that a helicopter will ditch near a platform – it’s happened, and its reasonably foreseeable that a helicopter will have to shutdown on the deck in marginal weather – again it’s happened, although not as often as the previous scenario.
The difficult part is weighing up the probability and consequence of such events. That’s where, in my experience, you get the discussions and sometimes there are no absolutely correct answers.
One platform operator and its helicopter contractor could take the view that if the weather is such that the fast rescue craft can’t be launched or the wind over the helideck is such that shutting down or subsequently starting up a helicopter runs the risk of damage to the aircraft then no flying will take place.
Another installation operator and helicopter contractor could take the view that, in similar conditions, the probability of a ditching is so low that they continue to be ALARP due to the ability to use the Dacon Scoop.
Thus you will get diametrically opposite modes of operation in similar weather conditions: which is no great comfort if you are stuck offshore watching someone else’s crew change helicopter overfly you on the way to the beach!
The intent of the PFEER, and other Regulations for Offshore Installations, is that you have to minimise the reasonably foreseeable risks to a level that is as low as is reasonably practicable (ALARP).
The identification of reasonably foreseeable risks is the easy part. Its reasonably foreseeable that a helicopter will ditch near a platform – it’s happened, and its reasonably foreseeable that a helicopter will have to shutdown on the deck in marginal weather – again it’s happened, although not as often as the previous scenario.
The difficult part is weighing up the probability and consequence of such events. That’s where, in my experience, you get the discussions and sometimes there are no absolutely correct answers.
One platform operator and its helicopter contractor could take the view that if the weather is such that the fast rescue craft can’t be launched or the wind over the helideck is such that shutting down or subsequently starting up a helicopter runs the risk of damage to the aircraft then no flying will take place.
Another installation operator and helicopter contractor could take the view that, in similar conditions, the probability of a ditching is so low that they continue to be ALARP due to the ability to use the Dacon Scoop.
Thus you will get diametrically opposite modes of operation in similar weather conditions: which is no great comfort if you are stuck offshore watching someone else’s crew change helicopter overfly you on the way to the beach!
Join Date: Jan 2002
Location: Aberdeen
Posts: 1,234
Likes: 0
Received 0 Likes
on
0 Posts
The argument is certainly based around PFEER - but it is complicated by the agreement between the CAA and HSE over juristication. Essentially the HSE have agreed 'hands off' regarding helicopter operations - so there is no published 'good practice' from the HSE on matters like these - and these days it is the published good practice which really sets what ALARP is - not a quantified risk assessement (i.e the frequency or liklihood is very low so its OK).
Reg 17 of PFEER states that 'effective arrangements are made, which include such arrangements with suitable persons beyond the installation, for - ....(b) rescue of persons near the installation; ... etc
So once you start thinking that the Dacon is unlikely to do more than recover bodies - sitting on the platform waiting for slightly better weather seems like a really good idea!
Reg 17 of PFEER states that 'effective arrangements are made, which include such arrangements with suitable persons beyond the installation, for - ....(b) rescue of persons near the installation; ... etc
So once you start thinking that the Dacon is unlikely to do more than recover bodies - sitting on the platform waiting for slightly better weather seems like a really good idea!
Join Date: Jan 2001
Location: UK
Age: 71
Posts: 1,364
Likes: 0
Received 0 Likes
on
0 Posts
Just to emphasise a point that gasax made implicitly, the requirement for rescue and recovery is not qualified by ALARP. The reg (17) reads as follows:
"Arrangements for recovery and rescue
17. The duty holder shall ensure that effective arrangements are made, which include such arrangements with suitable persons beyond the installation, for—
(a)recovery of persons following their evacuation or escape from the installation; and
(b)rescue of persons near the installation; and
(c)taking such persons to a place of safety,and
for the purposes of this regulation arrangements shall be regarded as being effective if they secure a good prospect of those persons being recovered, rescued, and taken to a place of safety."
The arrangements have to be "effective" and "secure a good prospect" of success. That is very different from ALARP and a lower legal standard.
It is also certainly true that PFEER does not apply to any helicopter flight away from the installations. Of course, when the worst happens, all available resources would be used, but that is different from being committed to a given standard.
The CAA would not be pleased if the HSE tried to impose standards on their patch.
"Arrangements for recovery and rescue
17. The duty holder shall ensure that effective arrangements are made, which include such arrangements with suitable persons beyond the installation, for—
(a)recovery of persons following their evacuation or escape from the installation; and
(b)rescue of persons near the installation; and
(c)taking such persons to a place of safety,and
for the purposes of this regulation arrangements shall be regarded as being effective if they secure a good prospect of those persons being recovered, rescued, and taken to a place of safety."
The arrangements have to be "effective" and "secure a good prospect" of success. That is very different from ALARP and a lower legal standard.
It is also certainly true that PFEER does not apply to any helicopter flight away from the installations. Of course, when the worst happens, all available resources would be used, but that is different from being committed to a given standard.
The CAA would not be pleased if the HSE tried to impose standards on their patch.