Offshore Helideck Ops
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Offshore Rig/Elevated Deck Takeoffs in Bell 212/412's
Current coffee break discussions have revolved around the "preferred" method of departing an offshore helideck or elevated helideck in a twin engine helicopter. One school of thought suggests a level acceleration to best rate of climb airspeed then a climb to a safe altitude whereas the other school of thought is to accelerate at a level altitude until the best angle of climb airspeed is reached, then climb at that speed to a safe height and then accelerate to the aircraft's best rate of climb airspeed. The first method is described as being "better" because it shortens the amount of time the aircraft is within the shaded portion of the Height/Velocity or WAT curve, whereas the second method is thought better because it provides more height above the water sooner, so as to improve the chances of accelerating to best rate of climb airspeed without making contact with the surface following an engine failure.
Major concern for this discussion involves low-height decks (i.e. 50 feet above surface) and the possible contact with the surface which might result while trying to accelerate and fly out of an engine failure at the most critical point of the takeoff...assumed to be just at crossing of the deck edge.
Major concern for this discussion involves low-height decks (i.e. 50 feet above surface) and the possible contact with the surface which might result while trying to accelerate and fly out of an engine failure at the most critical point of the takeoff...assumed to be just at crossing of the deck edge.
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Hover yourself over to deck edge so the rotors are overhanging. Into as much wind as available. Check all limits OK. Pull power and head upwards, then rotate off the deck. It now depends on if you are day or night.
Day accelerate to 60 kts and climb. Night accelerate slower climbing and accelerating at the same time.
So I suppose both your answers are correct, one for day, the other night.
By pulling power over the deck if anything fails you'll come straight back down on it. Or after rotation if an engine fails just after you aren't going to hit the tail on it.
Most decks are over 100 feet for major platforms. Smaller platforms can be 50 feet. If something fails just after rotation pull maximum single engine, aim at the water and get some airspeed!!!
Day accelerate to 60 kts and climb. Night accelerate slower climbing and accelerating at the same time.
So I suppose both your answers are correct, one for day, the other night.
By pulling power over the deck if anything fails you'll come straight back down on it. Or after rotation if an engine fails just after you aren't going to hit the tail on it.
Most decks are over 100 feet for major platforms. Smaller platforms can be 50 feet. If something fails just after rotation pull maximum single engine, aim at the water and get some airspeed!!!
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Did you consider that the HV curve is a limitation and not to be flown into at all?
Check the flight manual for those two aircraft (unless you have a Flight Manual Supplement for a cofiguration with less than 9 passengers) - the HV curve is in the limitations section.
Second part of the question might be- why not follow the Category A profile?
Check the flight manual for those two aircraft (unless you have a Flight Manual Supplement for a cofiguration with less than 9 passengers) - the HV curve is in the limitations section.
Second part of the question might be- why not follow the Category A profile?
Thread Starter
Lessee here Shawn.....if I creep the thing up to the edge of the deck...or scoot off over the edge...if my memory is anywhere near correct....I am unfortunately in the shaded part of the WAT Chart no matter what I do...and if the aircraft has more than nine pax...or seats for more than nine....and even if I use Cat A as you suggest....me thinks we still have a problem....am I correct in assuming that? Now does the WAT chart only apply to takeoffs over firm, smooth, surfaces....which oceans are not....gosh...maybe there is no legal way to make an offshore takeoff.
Can you enlighten me just a bit more here , Shawn? But of course we must never violate the limitations section of the flight manual while aviating....got any suggestions, flight profiles, weights, airspeeds, or something that will advance this thread, Shawn?
Can you enlighten me just a bit more here , Shawn? But of course we must never violate the limitations section of the flight manual while aviating....got any suggestions, flight profiles, weights, airspeeds, or something that will advance this thread, Shawn?
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There is a difference between the WAT chart limits and the HV. Hopefully you are well clear of the WAT chart anyway - the HV is the one that's difficult.
And you are right, there isn't a lot of help in interpreting the charts.
The 9 passengers or less limitation is on the configuration, not the number of seats you have occupied. You can see this in the change in the HV location on the BK-117 when it goes to a high density seating configuration - the HV curve moves to the limitations section of the supplement. S-76 with the less than 9 pax supplement has the HV curve in the performance section.
The problem is that most of the helicopter community doesn't understand that Part 29 helicopters are supposed to offer the same level of safety as a Part 25 airplane- that's why they are in that category instead of Part 27.
Which brings me back to my original question - why not use the CAT A techniques and performance stuff- the profiles are pretty straightforward, not much of a performance hit, and guaranteed to be able to fly away or land back if the engine fails?
And you are right, there isn't a lot of help in interpreting the charts.
The 9 passengers or less limitation is on the configuration, not the number of seats you have occupied. You can see this in the change in the HV location on the BK-117 when it goes to a high density seating configuration - the HV curve moves to the limitations section of the supplement. S-76 with the less than 9 pax supplement has the HV curve in the performance section.
The problem is that most of the helicopter community doesn't understand that Part 29 helicopters are supposed to offer the same level of safety as a Part 25 airplane- that's why they are in that category instead of Part 27.
Which brings me back to my original question - why not use the CAT A techniques and performance stuff- the profiles are pretty straightforward, not much of a performance hit, and guaranteed to be able to fly away or land back if the engine fails?
Thread Starter
Shawn,
I think the basic response is that operators have to provide as many seats as possible....and Cat A vice non-Cat A translates into 1-2 paying seats less per takeoff. It is also probably fair to state that oil companies usually give mere lip service to safety and revert to the Risk management mode when calculating safety costs....as compared to operational costs.
An example, a rather well known oil company and a large helicopter operator agreed to compromise on reject areas after selecting Cat A standards for their Bell 212 operation. One of the compromises included the approval for the operator to use canals and rivers as an authorized rejected takeoff area following an engine failure on takeoff from land based helipads. The decision was predicated upon the cost of preparing long, smooth, firm, and even landing surfaces for the aircraft. The Cat A takeoff profile itself was altered to provide some semblence of a normal Cat A profile to fit the very short dirt reject areas available. No thought was given to reducing the takeoff weight (based upon seating) during this process. The good news is .....to date there has not been an engine failure on takeoff that required an intentional reject into the water on that operation. The modified Cat A takeoff profile placed the aircraft smack in the middle of the shaded area of the WAT Chart....and was merely an old style US Army confined area takeoff over barriers 150 feet high...that is ...up, up, and away on a nice angle to 150 feet with a reject area as short as 250 feet. The profile seemed to work...but the thought of landing in the water as an approved reject area sure seems unwise to me.
I think the basic response is that operators have to provide as many seats as possible....and Cat A vice non-Cat A translates into 1-2 paying seats less per takeoff. It is also probably fair to state that oil companies usually give mere lip service to safety and revert to the Risk management mode when calculating safety costs....as compared to operational costs.
An example, a rather well known oil company and a large helicopter operator agreed to compromise on reject areas after selecting Cat A standards for their Bell 212 operation. One of the compromises included the approval for the operator to use canals and rivers as an authorized rejected takeoff area following an engine failure on takeoff from land based helipads. The decision was predicated upon the cost of preparing long, smooth, firm, and even landing surfaces for the aircraft. The Cat A takeoff profile itself was altered to provide some semblence of a normal Cat A profile to fit the very short dirt reject areas available. No thought was given to reducing the takeoff weight (based upon seating) during this process. The good news is .....to date there has not been an engine failure on takeoff that required an intentional reject into the water on that operation. The modified Cat A takeoff profile placed the aircraft smack in the middle of the shaded area of the WAT Chart....and was merely an old style US Army confined area takeoff over barriers 150 feet high...that is ...up, up, and away on a nice angle to 150 feet with a reject area as short as 250 feet. The profile seemed to work...but the thought of landing in the water as an approved reject area sure seems unwise to me.
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Just out of curiosity, if a good amount of power would be available departing the rig, how much vertical distance should you take above the deck before rotating?
What's the common practice out there?
What's the common practice out there?
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"Back Up Departures"?
Any one using a variant of the approach/departure Point-in-space technique?
The departure profile, common in the States in the EMS market, would be to apply sufficent power increments to vertically clear any nearby obstacles.
Then with slight increases in power, and back pressure on the cyclic, work away and back from the touchdown zone, until you reach a height of 150' to 200' above the ground/deck. Upon completion of a power assurance check, gently accelerate the airframe, without losing altitude, until you reach Vy.
It offers an opportunity to execute a sinlge engine procedure back to your departure point with minium ammounts of control input, power changes, and pitch attitude changes.
Perhaps it has more relevance in the confined areas which most EMS types work within, and their lack of appropriate F/L options.
Kevin
The departure profile, common in the States in the EMS market, would be to apply sufficent power increments to vertically clear any nearby obstacles.
Then with slight increases in power, and back pressure on the cyclic, work away and back from the touchdown zone, until you reach a height of 150' to 200' above the ground/deck. Upon completion of a power assurance check, gently accelerate the airframe, without losing altitude, until you reach Vy.
It offers an opportunity to execute a sinlge engine procedure back to your departure point with minium ammounts of control input, power changes, and pitch attitude changes.
Perhaps it has more relevance in the confined areas which most EMS types work within, and their lack of appropriate F/L options.
Kevin
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Cat A for a 212 from a rather old manual I have in front of me takes you backward and upwards to 160 feet. Initially straight upwards to 40-60ft.
In reality on a good day, hot and heavy your 100% TQ will get you max. 30 feet (more likely 10) above the deck when fully loaded..... and without a wind straight back down on it.
Thats all within weight limits and offloading payload above 22 Celsius.
So as you leave your deck, your tail will clear the deck should an engine fail. Now you have 110-130 feet to get to an airspeed to climb away.
In reality on a good day, hot and heavy your 100% TQ will get you max. 30 feet (more likely 10) above the deck when fully loaded..... and without a wind straight back down on it.
Thats all within weight limits and offloading payload above 22 Celsius.
So as you leave your deck, your tail will clear the deck should an engine fail. Now you have 110-130 feet to get to an airspeed to climb away.
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I guess I'm a bit surprised by some of things coming out here. First of all the takeoff profiles on a modified Cat A procedure should have been approved by the operating authority not just the helicopter operator and the oil company. Anything less than authority approval will leave you wide open for some pretty damning lawsuits.
I'm also very surprised that a Bell 212 at maximum weight cannot hover more than 30' AGL at sea level in warm conditions. I'll have to consult some performance stuff I have buried elsewhere, but at first glance it appears to me that it should have plenty of power reserve in those cases. Has anyone checked the weight to ensure you are within limits? remember that if you overload the machine, you invalidate the Certificate of Airworthiness....
I'm also very surprised that a Bell 212 at maximum weight cannot hover more than 30' AGL at sea level in warm conditions. I'll have to consult some performance stuff I have buried elsewhere, but at first glance it appears to me that it should have plenty of power reserve in those cases. Has anyone checked the weight to ensure you are within limits? remember that if you overload the machine, you invalidate the Certificate of Airworthiness....
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Ahhh....land v. sea?
Perhaps the difference rests within the element of this technique that you are NOT seeking a flyaway speed with the CatA backup departure.
Once you've cleared the initial obstacles which may impede the capacity to alter the nose of the craft, you gain the ability to alter the direction of the nose of your craft in order to better utilize the relative wind speed available that day.
The wind speed, the more the merrier, actually allows you to better manage your power buffer and back away bit by bit. It is by NO means a rapid response technique.
Should the worst happen, mechanical or met, you have the capacity below 150'(approx.) to execute a single engine approach right back down onto the helideck or LZ dependent upon relative surfaces.
Sorry, not meant to be confrontational, just conversational....
hope this is a better job of restating the concept?
Kevin
Once you've cleared the initial obstacles which may impede the capacity to alter the nose of the craft, you gain the ability to alter the direction of the nose of your craft in order to better utilize the relative wind speed available that day.
The wind speed, the more the merrier, actually allows you to better manage your power buffer and back away bit by bit. It is by NO means a rapid response technique.
Should the worst happen, mechanical or met, you have the capacity below 150'(approx.) to execute a single engine approach right back down onto the helideck or LZ dependent upon relative surfaces.
Sorry, not meant to be confrontational, just conversational....
hope this is a better job of restating the concept?
Kevin
Shawn; I don't know if the 212 transmission limits are any different these days but I spent a lot of time in the mid-1980s in a rather hot and swampy place having to pedal turn on takeoff in nil wind simply to clear the deck, and we were pretty confident about the weight being at or just under maximum. 30 feet wasn't often an option!
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I'm a bit surprised at the various ideas put forward for this interesting question. Helicopter offshore operations have been in existence for many years and the 212 for over 25 at least. Nearly all companies I've flown for use this basic tecnique.
1. Low hover at front of deck with blades NOT overlapping to build up ground caushion. Position can vary due to deck design & the turbulence you're getting.
2. Apply full available power & climb vertically.
3. At 20 feet radalt (15 feet minimum )for most medium size helicopters, while you still have a POSITIVE rate of climb, rotate fairly positively to about 10 degrees nose down. ( Can vary slightly with c of g )
4. If you can't reach this height, you are too heavy.
5. CDP is the point of rotation. Engine failure before rotation, land back on. After rotation, maintain collective position for transient time if nessary, while looking for VToss, level off and accelerate to VBROC.
6. By having 10 degrees nose down, your tail should be well up and clear of the deck.
7. This works by day or night. In fact you can do this all with your head in the cockpit looking at the instruments and is not a bad method to demonstrate to an unbeliever.
8. This method has worked well for me for over 40 years both in the cold of the Antarctic and the heat of India.
9. Obviously if the helicopter is very light and you have a strong helpful wind, you can modify this. Never make rig work too black & white.
10. Tearing along the deck to gain airspeed is very much a no no.
11. Now watch me be blown to pieces!!
1. Low hover at front of deck with blades NOT overlapping to build up ground caushion. Position can vary due to deck design & the turbulence you're getting.
2. Apply full available power & climb vertically.
3. At 20 feet radalt (15 feet minimum )for most medium size helicopters, while you still have a POSITIVE rate of climb, rotate fairly positively to about 10 degrees nose down. ( Can vary slightly with c of g )
4. If you can't reach this height, you are too heavy.
5. CDP is the point of rotation. Engine failure before rotation, land back on. After rotation, maintain collective position for transient time if nessary, while looking for VToss, level off and accelerate to VBROC.
6. By having 10 degrees nose down, your tail should be well up and clear of the deck.
7. This works by day or night. In fact you can do this all with your head in the cockpit looking at the instruments and is not a bad method to demonstrate to an unbeliever.
8. This method has worked well for me for over 40 years both in the cold of the Antarctic and the heat of India.
9. Obviously if the helicopter is very light and you have a strong helpful wind, you can modify this. Never make rig work too black & white.
10. Tearing along the deck to gain airspeed is very much a no no.
11. Now watch me be blown to pieces!!
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for shawn coyle
What's a modified Cat A???
I was taught a Cat A is just that....anything else may be a company approved procedure or a pilots own choice, at his discretion.( Cat B?)
Thanks!
I was taught a Cat A is just that....anything else may be a company approved procedure or a pilots own choice, at his discretion.( Cat B?)
Thanks!
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Yeah, but what about....?
Being a theorist and not a pilot I open myself to some flack on this but I will repeat what I stated in a post I made a long time ago. This post is in response to the advice given about hovering the helicopter to the edge of the flight deck placing half of the disc in ground effect and the other half out of ground effect.
Many years ago a group of US Marine HRSs (S-55s) did just that only in this case the back ends of the helicopters were hanging over the ocean which was 80 some feet below. When they successively pulled collective they fell backwards one-by-one into the ocean below. A lot of people told me I was full of it and said it was impossible however it did happen and they lost several helicopters in the process. It is similar to hovering above a moving ship and letting the ship move out from under you. When the ground effect of the flight deck was no longer there the helicopter in which I was riding almost fell into the water until the pilot regained positive control.
Many years ago a group of US Marine HRSs (S-55s) did just that only in this case the back ends of the helicopters were hanging over the ocean which was 80 some feet below. When they successively pulled collective they fell backwards one-by-one into the ocean below. A lot of people told me I was full of it and said it was impossible however it did happen and they lost several helicopters in the process. It is similar to hovering above a moving ship and letting the ship move out from under you. When the ground effect of the flight deck was no longer there the helicopter in which I was riding almost fell into the water until the pilot regained positive control.
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Nigel
Well the technique used here is exactly as you described except we hang the rotors over the edge of the deck. I think you have just explained it better.
At night our preference is towards more level than 10 degrees nose down. Just preference for altitude over airspeed.
Shawn
Max Gross is 11,200 and start lowering from 22 Celsius upwards. From 25 degrees it's about 60-70lb per degree. 38 Celsius will allow you 10280. Temperature, higher of ground or 1000'
Lu
I can understand falling into the water backwards when pulling power with your tail over the edge of the deck but not if you are into wind. If into wind you normally will gain an updraft when at deck edge.
Retiring back behind my stone for cover........
Well the technique used here is exactly as you described except we hang the rotors over the edge of the deck. I think you have just explained it better.
At night our preference is towards more level than 10 degrees nose down. Just preference for altitude over airspeed.
Shawn
Max Gross is 11,200 and start lowering from 22 Celsius upwards. From 25 degrees it's about 60-70lb per degree. 38 Celsius will allow you 10280. Temperature, higher of ground or 1000'
Lu
I can understand falling into the water backwards when pulling power with your tail over the edge of the deck but not if you are into wind. If into wind you normally will gain an updraft when at deck edge.
Retiring back behind my stone for cover........
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Guys........get it right before your OEI in a critical phase occurs....!!!!..or it will hurt.
Good to see old Nigel has found the pump for his wheel chair tyres....
Remember the Oil Platform is a thing to avoid at all costs if you have anything except both engines running wide open..!!!
From a purest point of view,yes the HV curve is in the limitations section....however remember......BHT also tolerate, Winching, Slinging, Longlining and Oil Patform T/o and Landings......
Cat A......geee guys........There is NO place for Cat A is todays Oil Operations......remember what Cat A is designed for..???...
*To ensure a safe OEI reject or safe flyaway after an OEI event for a specific known take off distance.....and reduce the T/O Wt until that performance can be achieved.........and the relevance to Offshore..?.....not much.
A safe departure?.....as per old Nigel......however a 15 nose down or attitude change would be nicier........and there should be no difference for your night verses day technique...remember your Nr droop doesnt know the time of day....nose held down until your airspeed is alive then reduce your nose down attitude......remember its better to be closer with the surface [water] with a healthy Nr and close to Vtoss than at 150 ft with the low NR warning on and no IAS.......farewell indeed.
The suggestion of backing back off an Oil Platform is horrific....in the OEI configatation the oil rig is your bitter enemy....better the water than an impact on the deck [hovering auto excepted]......once CDP is reached at around 15 feet....15 nose down and get out of there.........
OEI before the commited point on approach.....get out of there...overshoot.
Keep your Nr UP.
PS.....Move to the deck edge.......Rotor tips inline with the edge.......not over it........
Good to see old Nigel has found the pump for his wheel chair tyres....
Remember the Oil Platform is a thing to avoid at all costs if you have anything except both engines running wide open..!!!
From a purest point of view,yes the HV curve is in the limitations section....however remember......BHT also tolerate, Winching, Slinging, Longlining and Oil Patform T/o and Landings......
Cat A......geee guys........There is NO place for Cat A is todays Oil Operations......remember what Cat A is designed for..???...
*To ensure a safe OEI reject or safe flyaway after an OEI event for a specific known take off distance.....and reduce the T/O Wt until that performance can be achieved.........and the relevance to Offshore..?.....not much.
A safe departure?.....as per old Nigel......however a 15 nose down or attitude change would be nicier........and there should be no difference for your night verses day technique...remember your Nr droop doesnt know the time of day....nose held down until your airspeed is alive then reduce your nose down attitude......remember its better to be closer with the surface [water] with a healthy Nr and close to Vtoss than at 150 ft with the low NR warning on and no IAS.......farewell indeed.
The suggestion of backing back off an Oil Platform is horrific....in the OEI configatation the oil rig is your bitter enemy....better the water than an impact on the deck [hovering auto excepted]......once CDP is reached at around 15 feet....15 nose down and get out of there.........
OEI before the commited point on approach.....get out of there...overshoot.
Keep your Nr UP.
PS.....Move to the deck edge.......Rotor tips inline with the edge.......not over it........
I agree with Nigel and red wine. Everything works fine with a deck at 100' or so above the drink. If the deck is lower, say 50' as previously mentioned or on a ship, then you have to ask the question: if I continue to climb vertically to gain enough height to fly away OEI after rotating, how hard might I hit the deck OEI if I abort prior to rotating. Depends on almost everything, and if OEI ditching or hard landings are not an option, pay the dough to load real light....
Iconoclast
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Mixed signals.
To: Rotorbike
Although not totally conversant with the entire situation I can only report the facts, as I know them. There had to be a strong relative wind flowing across the deck from stem to stern due to the ships' movement through the water. And, there may have been as you indicated a strong updraft, which may have caused a confusing, wind state with the updraft mixing with the longitudinal flow. This was coupled with the possible lift differential across the rotor disc caused by one side of the disc in the stable airflow while advancing and the other side of the disc in the confused airflow while retreating. If I could, I would place a very large ? at this point. Is it possible that it was due to a flap/blow back situation caused by the strong airflow across the deck (20-35 Knots)?
On the present helicopter carriers (LHA) the helicopters and the Harriers are aligned with the centerline of the ship however on the CH-53s a part of the rotor may be over the side but then again the CH-53s have more than adequate power where the HRSs only had 600-700 Horsepower availavle.
Although not totally conversant with the entire situation I can only report the facts, as I know them. There had to be a strong relative wind flowing across the deck from stem to stern due to the ships' movement through the water. And, there may have been as you indicated a strong updraft, which may have caused a confusing, wind state with the updraft mixing with the longitudinal flow. This was coupled with the possible lift differential across the rotor disc caused by one side of the disc in the stable airflow while advancing and the other side of the disc in the confused airflow while retreating. If I could, I would place a very large ? at this point. Is it possible that it was due to a flap/blow back situation caused by the strong airflow across the deck (20-35 Knots)?
On the present helicopter carriers (LHA) the helicopters and the Harriers are aligned with the centerline of the ship however on the CH-53s a part of the rotor may be over the side but then again the CH-53s have more than adequate power where the HRSs only had 600-700 Horsepower availavle.
Last edited by Lu Zuckerman; 23rd May 2002 at 14:44.