SUper Puma's Suffering from bad Press?
Discussion
I see North Sea Oil workers are planning to boycott CHC's Super Puma's as they don't feel "safe" using them. Looking at the Fleet in Scotland it seems they fly the majority of flights and there are a considerable number of flights per day. Hence any incident is liable to be a Super Puma due to the number of them up there. I suspect if they used any other type in that number they would "show" up in the stats as well. A lot of 737's crash as well but nobody stops using them.
A very emotive subject at the moment up here and the O&G industry is a very small community, from a statistical stance you are probably correct but personal perception is very strong. However, in reality the ratio of mechanical failures of fixed wing against helicopters in the air and the survivability after the event may show a I different statistic, I do not know but offer it for consideration.
Unfortunately there is no answer as to what is the correct course of action by anyone involved until the investigation has taken place but one must respect the concerns of those who fly on them. I spent 15 years offshore flying on the things, had a couple of mechanical issues on route and I always wondered how I would react if anything untoward happened. You look around you in a helicopter and at the time there were 19 of us crammed in. Research a number of years ago highlighted some of the highest stress levels ever monitored among the boarding offshore passengers, a trip offshore on a helicopter is no pleasure trip and can last many many hours over a very hostile environment.
Unfortunately there is no answer as to what is the correct course of action by anyone involved until the investigation has taken place but one must respect the concerns of those who fly on them. I spent 15 years offshore flying on the things, had a couple of mechanical issues on route and I always wondered how I would react if anything untoward happened. You look around you in a helicopter and at the time there were 19 of us crammed in. Research a number of years ago highlighted some of the highest stress levels ever monitored among the boarding offshore passengers, a trip offshore on a helicopter is no pleasure trip and can last many many hours over a very hostile environment.
They have a known problem with gearbox failures and this is not the first incident. There have been previous, fatality-free, ditchings.
Given this is a known fault (although the cause of the latest crash has not been determined), it is a reasonable assumption that any given Super Puma may fail at any given time and flying in a Super Puma is risky.
There are no known faults with the capacity to immediately down any other aircraft in service - because when such a fault is discovered, they get grounded.
Given this is a known fault (although the cause of the latest crash has not been determined), it is a reasonable assumption that any given Super Puma may fail at any given time and flying in a Super Puma is risky.
There are no known faults with the capacity to immediately down any other aircraft in service - because when such a fault is discovered, they get grounded.
Gearbox problems tend to be the major cause of Helicopter incidents and not only with the Super Puma. I suspect that it would be a maintenance issue. Looking at the Numbers carried on an individual flight and the kit required, (Life jacket etc), I think 18 per Puma may need to be cut down as where it is feasible to escape It could get a bit crowded at the exits? The Super Puma does seem to be an "ideal" size for the Platforms. The S92 for example does not seem to fly as many in the North Sea area.
So there are two issues here - the mechanical reliability, and the ability to ditch safely (which also depends on sea conditions)
In the event (1) fails, (2) is the back-up. I don't know much about these craft but can they not be fitted with flotation bags/collars like Apollo capsules? Or do they already have them?
In the event (1) fails, (2) is the back-up. I don't know much about these craft but can they not be fitted with flotation bags/collars like Apollo capsules? Or do they already have them?
theres a few versions of the Super Puma in use (think they make up in total about 45% of the north sea fleet.
This latest crash was a L2 version, the same version that Bond had crash a couple years ago killing all on board.
The two ditchings last year was the EC225 version which is the latest, and have only recently been cleared to fly.
One ditching was only due to the crew recieving a warning that the gearbox lube pump had no oil so they carried out a controlled ditching. Another ditching was due to the altimiter warning being set wrong and the pilots landed on the sea in fog thinking they were actually landing on the rig....
since the EC225 fleet was grounded, all other versions have had to carry the slack meaning they were flying 7 days a week, so this will obviously mean more flying hours on components etc..
theres a lot of emotion at work at the moment, which is understandable but until the cause of the latest crash is known, not much point in knee jerk reactions of banning perfectly good aircraft. you also dont want to rely on one single type either as if they are grounded, then nothing flys..
i dont work offshore now, but id still happily fly in a super puma if the alternative is boat transfers, being lifted down to a moving vessel from a crane isnt something id want to do in open water...
This latest crash was a L2 version, the same version that Bond had crash a couple years ago killing all on board.
The two ditchings last year was the EC225 version which is the latest, and have only recently been cleared to fly.
One ditching was only due to the crew recieving a warning that the gearbox lube pump had no oil so they carried out a controlled ditching. Another ditching was due to the altimiter warning being set wrong and the pilots landed on the sea in fog thinking they were actually landing on the rig....
since the EC225 fleet was grounded, all other versions have had to carry the slack meaning they were flying 7 days a week, so this will obviously mean more flying hours on components etc..
theres a lot of emotion at work at the moment, which is understandable but until the cause of the latest crash is known, not much point in knee jerk reactions of banning perfectly good aircraft. you also dont want to rely on one single type either as if they are grounded, then nothing flys..
i dont work offshore now, but id still happily fly in a super puma if the alternative is boat transfers, being lifted down to a moving vessel from a crane isnt something id want to do in open water...
Simpo Two said:
So there are two issues here - the mechanical reliability, and the ability to ditch safely (which also depends on sea conditions)
In the event (1) fails, (2) is the back-up. I don't know much about these craft but can they not be fitted with flotation bags/collars like Apollo capsules? Or do they already have them?
yes they have flotation bags, but with the engines being up high they are very top heavy and unstable, hence having to train to escape if they do flip..In the event (1) fails, (2) is the back-up. I don't know much about these craft but can they not be fitted with flotation bags/collars like Apollo capsules? Or do they already have them?
creampuff said:
They have a known problem with gearbox failures and this is not the first incident. There have been previous, fatality-free, ditchings.
Given this is a known fault (although the cause of the latest crash has not been determined), it is a reasonable assumption that any given Super Puma may fail at any given time and flying in a Super Puma is risky.
There are no known faults with the capacity to immediately down any other aircraft in service - because when such a fault is discovered, they get grounded.
Aren't you contradicting yourself a bit here? If what your saying is correct i.e. aircraft with known faults get grounded and the super puma was inherently unsafe, it too would also be grounded? Given this is a known fault (although the cause of the latest crash has not been determined), it is a reasonable assumption that any given Super Puma may fail at any given time and flying in a Super Puma is risky.
There are no known faults with the capacity to immediately down any other aircraft in service - because when such a fault is discovered, they get grounded.
Doesn't the fact that it hasn't been grounded then indicate that it is safe to fly on?
telecat said:
Gearbox problems tend to be the major cause of Helicopter incidents and not only with the Super Puma.
A Helicopter Safety Steering Group report landed on my desk about a month ago, on the EC225 Super Puma. There is a specific problem with the Super Puma. =======
In the last update in May 2013, the HSSG reported that Eurocopter had completed its
investigation into the causes of the EC225 Main Gearbox (MGB) shaft failures in May 2012
and October 2012, and had identified the root causes and interim and long-term measures
to return the EC225 to service over the North Sea.
Eurocopter attributed both MGB gear shaft
failures to fatigue cracks in the vicinity of
the electron beam weld joining the bevel
gear with the lower vertical shaft driving the
gearbox oil pumps. Eurocopter identified that
the fatigue life of the shafts was reduced
by manufacturing residual stress and stress
concentration in the weld area; then, due to
further weakening caused by corrosion pits,
and active corrosion attack from trapped
moisture in the weld area, small cracks
formed. With the high shaft rotation speed,
the shafts rapidly accumulate millions of
number of fatigue cycles, and the cracks grew
until the shafts failed, after about 20 hours of
flying since crack initiation.
Eurocopter replicated the failure mechanism by corroding metal test samples in the
laboratory then fatigue testing the samples on a test rig until small cracks formed in the
samples. Importantly, the active corrosion is similar to corrosion fatigue and only occurs
when the following three ingredients are present:
1. Stress due to flight loads,
2. Temperature (above ~80 0C) when gearbox is in operation, and
3. Moisture trapped against the shaft as described below.
The exact points at which the cracks started in the two ditching incidents were different,
but both started in the high stress area, near the weld. In the May-2012 incident, corrosion
was found at the weld stop hole, and the crack grew from this point. The hole is fitted with
a plug, and water was held in a gap between the plug and countersink drilled into the hole.
The gap was formed due to a detail change in the countersink on a particular batch of gear
shafts. This batch of shafts will be remanufactured to the correct specification.
The HSSG has secured full, independently verified assurance that the root causes of the two
EC225 gear box failures has been identified and Eurocopter’s proposed immediate and long
terms solutions are valid, enabling a safe return to flight;
• Prevent fatigue cracks forming by stopping active corrosion:
- Eliminate moisture traps by cleaning and removing the paste; also remove and
replace the weld hole plug.
- Modify the MGB oil jets to spray
oil further up inside the shaft,
keeping the weld zone clean to
prevent moisture traps, also to
improve lubrication of the gear
splines.
• Inspect the gear shafts regularly to
ensure early detection of very small
cracks pre-flight.
• Monitor vibration on the aircraft
using the HUMS system to detect
cracks in flight in time to allow safe
landing.
==
So you only get about 20 hours flying after crack initiation until failure of the gearbox, which will always send you down.
el stovey said:
Aren't you contradicting yourself a bit here? If what your saying is correct i.e. aircraft with known faults get grounded and the super puma was inherently unsafe, it too would also be grounded?
Doesn't the fact that it hasn't been grounded then indicate that it is safe to fly on?
The Super Pumas were withdrawn prior to this incident. Doesn't the fact that it hasn't been grounded then indicate that it is safe to fly on?
We still do not know the cause of this ditching... it may be related to the known gearbox problem which had been addressed or it may be something else.
creampuff said:
el stovey said:
Aren't you contradicting yourself a bit here? If what your saying is correct i.e. aircraft with known faults get grounded and the super puma was inherently unsafe, it too would also be grounded?
Doesn't the fact that it hasn't been grounded then indicate that it is safe to fly on?
The Super Pumas were withdrawn prior to this incident. Doesn't the fact that it hasn't been grounded then indicate that it is safe to fly on?
We still do not know the cause of this ditching... it may be related to the known gearbox problem which had been addressed or it may be something else.
I think they have a known problem with the gearbox which will mean gearbox failures will continue until fixed.
They HAVE provided both a temporary and permanent fix which is why Super Pumas are back in service at least until this crash. The temporary fix is:
• Prevent crack initiation by stopping active corrosion:
- Eliminate moisture traps by cleaning and removing oily paste; as well as improving the weld hole finish and fitting a modified plug.
- Modify oil jet to spray oil further up inside the shaft, keeping the weld zone clean to prevent moisture traps.
• Pre-flight inspect the gear shafts regularly, using Non-Destructive Inspection equipment, to ensure early detection of very small
cracks.
• In-flight, monitor vibration on the aircraft using the new, in-cockpit HUMS monitoring system, to detect cracks with sufficient time
to fly to a suitable landing site
While the existing shafts are safe with the measures described above, Eurocopter is manufacturing a new shaft to eliminate stress factors
and hot spots and prevent corrosion. This will take over a year to design, manufacture, test, certify and fit to the fleet
We don't know what caused this incident but it wouldn't surprise me if it is the same gearbox shaft fatigue failure problem.
They HAVE provided both a temporary and permanent fix which is why Super Pumas are back in service at least until this crash. The temporary fix is:
- ==
• Prevent crack initiation by stopping active corrosion:
- Eliminate moisture traps by cleaning and removing oily paste; as well as improving the weld hole finish and fitting a modified plug.
- Modify oil jet to spray oil further up inside the shaft, keeping the weld zone clean to prevent moisture traps.
• Pre-flight inspect the gear shafts regularly, using Non-Destructive Inspection equipment, to ensure early detection of very small
cracks.
• In-flight, monitor vibration on the aircraft using the new, in-cockpit HUMS monitoring system, to detect cracks with sufficient time
to fly to a suitable landing site
- ==
- ==
While the existing shafts are safe with the measures described above, Eurocopter is manufacturing a new shaft to eliminate stress factors
and hot spots and prevent corrosion. This will take over a year to design, manufacture, test, certify and fit to the fleet
- ==
We don't know what caused this incident but it wouldn't surprise me if it is the same gearbox shaft fatigue failure problem.
Unfortunately, due to the nature of the beast, it is helicopters themselves that are inherently "unsafe" compared to fixed wing aircraft.......
If you consider a fixed wing aircraft, broadly speaking the production of lift, the production of thrust, and the control of those two forces is separate. With a few redundant systems, a failure on one system does not lead to a catastrophic failure on any of the others. Added to which, the primary lift producing structure, the wing, is almost a "solid state" device. Ie it does not move and hence is inherently robust (i'll ignore bending stresses etc here for the moment)
Compare that to a rotary wing aircraft. Everything is interlinked, and all the power that keeps the aircraft flying must travel through those complex and rapidly moving systems. A failure of a single component is generally catastrophic and unrecoverable. It's not really surprising that the main gearhead geartrain is very often the point of failure. It's probably the highest loaded component, and is mechanically complex, yet needs to be lightweight, and vibration/fatigue resistant!
Then you get to the operating environment. Helicopters by their nature operate close to the ground for a much higher proportion of there airframe hrs. Any failure here simply gives the operators little or no time to react. It also brings the aircraft into the worst of the weather.
So, really, we are left with the fact that offshore rotary wing transport will never be as safe as commercial fixed wing flying, it can't be. Now i'm not saying that operators should ignore the risks, or not to try to improve safety where ever possible, of course not, but that the users of these machines understand and accept those risks.
If you consider a fixed wing aircraft, broadly speaking the production of lift, the production of thrust, and the control of those two forces is separate. With a few redundant systems, a failure on one system does not lead to a catastrophic failure on any of the others. Added to which, the primary lift producing structure, the wing, is almost a "solid state" device. Ie it does not move and hence is inherently robust (i'll ignore bending stresses etc here for the moment)
Compare that to a rotary wing aircraft. Everything is interlinked, and all the power that keeps the aircraft flying must travel through those complex and rapidly moving systems. A failure of a single component is generally catastrophic and unrecoverable. It's not really surprising that the main gearhead geartrain is very often the point of failure. It's probably the highest loaded component, and is mechanically complex, yet needs to be lightweight, and vibration/fatigue resistant!
Then you get to the operating environment. Helicopters by their nature operate close to the ground for a much higher proportion of there airframe hrs. Any failure here simply gives the operators little or no time to react. It also brings the aircraft into the worst of the weather.
So, really, we are left with the fact that offshore rotary wing transport will never be as safe as commercial fixed wing flying, it can't be. Now i'm not saying that operators should ignore the risks, or not to try to improve safety where ever possible, of course not, but that the users of these machines understand and accept those risks.
Surely you cannot compare a fixed wing aircraft with a rotary wing helicopter? After all the former cannot land on an oilrig!
The impression I get as a member of the public is that helicopters serving the North Sea rigs come down relatively regularly. However at the same time I suspect that North Sea operation is one of the most intensive use of helicopters in the country and then all tend to be full of passengers.
The very nature of the enviroment in the North Sea must make it a more difficult place to operate rather than over land and I guess the accident record rates you need to compare are those to the North Sea and those flown inland.
However I suspect that the intensive use of the North Sea fleet is likely to give rise to more accidents, although I wouldn't like to say if that is more accidents per mile flown. Once you know this figure one can then consider whether any differential is caused by the harsher enviroment in the North Sea.
Of course the alternative to a helicpoter transfer is boat, and that option may not be particlarly favoured by those in need of transport bearing in mind the extended journey times etc.
However I am slightly concerned about this idea of the fact that it is 20 hours flying time from identification of cracks to failure, as how long is a return flight to an oil rig? I would guess you don't get many return flights in 20 hours flying time.
Personally I can understand why workers may be reluctant to fly on them and I thought those serving the North Sea had been grounded?
The impression I get as a member of the public is that helicopters serving the North Sea rigs come down relatively regularly. However at the same time I suspect that North Sea operation is one of the most intensive use of helicopters in the country and then all tend to be full of passengers.
The very nature of the enviroment in the North Sea must make it a more difficult place to operate rather than over land and I guess the accident record rates you need to compare are those to the North Sea and those flown inland.
However I suspect that the intensive use of the North Sea fleet is likely to give rise to more accidents, although I wouldn't like to say if that is more accidents per mile flown. Once you know this figure one can then consider whether any differential is caused by the harsher enviroment in the North Sea.
Of course the alternative to a helicpoter transfer is boat, and that option may not be particlarly favoured by those in need of transport bearing in mind the extended journey times etc.
However I am slightly concerned about this idea of the fact that it is 20 hours flying time from identification of cracks to failure, as how long is a return flight to an oil rig? I would guess you don't get many return flights in 20 hours flying time.
Personally I can understand why workers may be reluctant to fly on them and I thought those serving the North Sea had been grounded?
Oh forgot to mention: The last incident was on a Super Puma AS332 L2. The previous withdrawal from service was the Super Puma EC225.
I don't know enough about the internals to say how different the gearbox is and if this particular fatigue problem is common to all types.
Meanwhile, all Super Pumas of all types have been voluntarily withdrawn from ferry flights in the UK North Sea.
I don't know enough about the internals to say how different the gearbox is and if this particular fatigue problem is common to all types.
Meanwhile, all Super Pumas of all types have been voluntarily withdrawn from ferry flights in the UK North Sea.
Chrisgr31 said:
Surely you cannot compare a fixed wing aircraft with a rotary wing helicopter? After all the former cannot land on an oilrig!
Perfectly valid comparison imo - we are comparing the safety under fatigue failure of both types of aircraft. Obviously a fixed-wing isn't suitable for flight to a rig, just as a rotary isn't much good at high-speed and long-distance flight.
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