Heli ditch North Sea G-REDL: NOT condolences
mckeg4
If you are asking "could it happen again" then in all honesty I think the answer has to be yes, since cracks in gearbox components are very difficult to find until you strip down the gearbox - they don't release significant chips and HUMS is not very good at detecting them.
However you also have to ask yourself the probability of that happening. Bearing in mind its the first such event on an AS332L/L2/225 that I am aware of, and the fleet hours runs to tens of millions of hours, you will almost certainly die another way, such as from a road accident, from cancer, from an injury offshore, from a stabbing on Union St on Saturday night etc.
16 people died in a tragic accident, but how many more people that have worked offshore are now dead - surely it must be thousands, many having died of that fatal disease called old age, and a good number from work injuries offshore (more than in all helicopter accidents)
Perhaps I am not being comforting, but life is dangerous and fragile and all we can do is to try to maximise safety and avoid taking unnecessary risks. You can be sure that those of us driving up front try to do just that. Despite the risk of an undetected gearbox crack, offshore helicopters including the L2 are very safe. Its just that there is no such thing as absolute safety.
HC
If you are asking "could it happen again" then in all honesty I think the answer has to be yes, since cracks in gearbox components are very difficult to find until you strip down the gearbox - they don't release significant chips and HUMS is not very good at detecting them.
However you also have to ask yourself the probability of that happening. Bearing in mind its the first such event on an AS332L/L2/225 that I am aware of, and the fleet hours runs to tens of millions of hours, you will almost certainly die another way, such as from a road accident, from cancer, from an injury offshore, from a stabbing on Union St on Saturday night etc.
16 people died in a tragic accident, but how many more people that have worked offshore are now dead - surely it must be thousands, many having died of that fatal disease called old age, and a good number from work injuries offshore (more than in all helicopter accidents)
Perhaps I am not being comforting, but life is dangerous and fragile and all we can do is to try to maximise safety and avoid taking unnecessary risks. You can be sure that those of us driving up front try to do just that. Despite the risk of an undetected gearbox crack, offshore helicopters including the L2 are very safe. Its just that there is no such thing as absolute safety.
HC
Flight risk vs driving risk
Wiz mentioned -
The most dangerous part of your trip will continue to be the drive to the airport.
The most dangerous part of your trip will continue to be the drive to the airport.
Hmmm - seems unlikely for this type of flying.
Searching the internet for random sources brings up:-
http://www.pprune.org/archive/index.php/t-331176.html
Presenting a paper at the Royal Aeronautical Society’s Maritime Operations of Rotorcraft conference on Wednesday, Stevens referred to air safety performance figures that put offshore transport in third place with 4.5 fatal per one million flying hours compared to 2.0 for commuter airlines and 0.6 for average commercial airlines.
Death rate: the number of road deaths per billion vehicle kilometres
1 fatality per 7 or 8 per billion vehicle kilometers for the UK.
So rounding the numbers slightly for arithmetic convenience, it seems that we would need about 2000km driving per hour flying.
8,000 / 4 (all millions).
7000 / 4.5 gives about 1,000 miles.
Of course quite a few offshore workers will indeed travel that far
but I think the average will be significantly less.
Luckily, driving a shorter distance to the airport does not
make the flight more (or less) hazardous
This is clearly not a rigorous analysis and the road numbers will be affected by multiple vehicle occupancy for one thing.
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I agree with you there LASTMINUTE, unless WAH has access to information not provided by the AAIB then the chip and not HUMS seems to be the starting point. They make no mention of a HUMS exceedence prior to the last flight. It also seems likely that the close monitoring 25 hours had also been concluded prior to the last flight. Normally a specified period is put in place for close monitoring and 25 hours would not be unusual.AAIB "HUMS data was downloaded and analysed each time the helicopter returned to it's base at Aberdeen for the next 25 flying hours. No further abnormalities were identified DURING this period."Just my interpretation of the AAIB statement
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well, if it makes anyone feel better, our epicyclic chip detectors were checked every 25hrs previous to this happening, so if it means doing it every 10 now, then its no great hassle to do this. it takes literally 10 seconds to check, so could be done on every turnround if that is what was mandated, without any impact on sheduling/operations.
i for one as an L2 engineer, amoungst other aircraft, would happily carry this task out after every flight if it helped to allay the fears of those flying on the A/C.
one other thing about the HUMS though, that i dont think anyone mentioned. when you fit a new component that has a threshhold, they often have to be re learned due to differences between the items fitted. no two are exactly the same.
pulling greaboxes in the circumstances laid out in the SB, thats going to put a lot of pressure on the Engineers, but alas is something we'll just have to get on with. sourcing gearboxes will be a nightmare. spares for overhaul arent easy to come by. It takes two years for an epicyclic ring gear to age harden so there is a massive lead time needed for spares support on them! same for a main rotor mast.
i for one as an L2 engineer, amoungst other aircraft, would happily carry this task out after every flight if it helped to allay the fears of those flying on the A/C.
one other thing about the HUMS though, that i dont think anyone mentioned. when you fit a new component that has a threshhold, they often have to be re learned due to differences between the items fitted. no two are exactly the same.
pulling greaboxes in the circumstances laid out in the SB, thats going to put a lot of pressure on the Engineers, but alas is something we'll just have to get on with. sourcing gearboxes will be a nightmare. spares for overhaul arent easy to come by. It takes two years for an epicyclic ring gear to age harden so there is a massive lead time needed for spares support on them! same for a main rotor mast.
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I remember reading in an earlier posting on this thread, a day or so after the accident that the helicopter was supposed to be having it's MGB changed the next day. Could anyone shed any more light on this?
You want what??
Modern helicopters (i.e. those designed since 1972 or so) have at a minimum multiple main transmission chip detectors which have indications on which one is tripping. Some of these are ganged into a single alert to the crew.
There is also this great new technology (again 30+ plus years ago) which has the ability to burn off nuisance fusz and leaves only substantial debris as an idication of the seriousness. They are called fuzz burnering chip detectors. The crew are aware when a chip is burned and this generally is treated just a little lower than a chip (i.e. Multiple burns is bad).
Later technology (20+ years ago) have quanity debris monitors which can tell the volume of material acruing on the detector.
History has shown crew annuciated chip detectors are "god's gift" to flight safety. HUMS vibration monitoring only adds to this, but never can replace it or provide even an equal level of eqivalent safety.
Striation counts and what debris is in the filter may be able to tell how much time elapsed between initiation and total failure on the Bond aircraft.
As to checking mag plugs, before every flight would be prudent.
The Sultan
Modern helicopters (i.e. those designed since 1972 or so) have at a minimum multiple main transmission chip detectors which have indications on which one is tripping. Some of these are ganged into a single alert to the crew.
There is also this great new technology (again 30+ plus years ago) which has the ability to burn off nuisance fusz and leaves only substantial debris as an idication of the seriousness. They are called fuzz burnering chip detectors. The crew are aware when a chip is burned and this generally is treated just a little lower than a chip (i.e. Multiple burns is bad).
Later technology (20+ years ago) have quanity debris monitors which can tell the volume of material acruing on the detector.
History has shown crew annuciated chip detectors are "god's gift" to flight safety. HUMS vibration monitoring only adds to this, but never can replace it or provide even an equal level of eqivalent safety.
Striation counts and what debris is in the filter may be able to tell how much time elapsed between initiation and total failure on the Bond aircraft.
As to checking mag plugs, before every flight would be prudent.
The Sultan
THE SULTAN
Not necessarily so. The Eurocopter SA365N series as standard have no indicating mag plugs or fuzz burners for the transmissions. They have a mag plug quick disconnect for the MRGB and the TRGB. A mag plug which requires tools to remove it for the mast.
I believe the BO105 had an indicating system for the MRGB but it was removed on UK aircraft because of the high number of spurious warnings!!!!
MITCHAA
I pull mag plugs on a daily basis and as part of a sceduled maintenance program. I've yet to pull one specifically as the result of a HUMS report.
In truth in this case it could be either. However there is no mention of a HUMS issue before the accident in the AAIB report. I would have thought it would get a mention.
Not necessarily so. The Eurocopter SA365N series as standard have no indicating mag plugs or fuzz burners for the transmissions. They have a mag plug quick disconnect for the MRGB and the TRGB. A mag plug which requires tools to remove it for the mast.
I believe the BO105 had an indicating system for the MRGB but it was removed on UK aircraft because of the high number of spurious warnings!!!!
MITCHAA
I pull mag plugs on a daily basis and as part of a sceduled maintenance program. I've yet to pull one specifically as the result of a HUMS report.
In truth in this case it could be either. However there is no mention of a HUMS issue before the accident in the AAIB report. I would have thought it would get a mention.
Last edited by ericferret; 11th Apr 2009 at 17:49.
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Sultan,
not really sure why the tech lesson was directed at me, i was only stating a fact as to what happens on the a/c i work on. i am type rated on L2 and other types, so am well aware of the chip detectors in the system.
L2 has Sump detector with "XMSN" caption on 10ww panel and Warnings
flared housing, manual detection on hourly based removal (19mm spanner)
epicyclic with HUMS detection,
IGB with HUMS detection,
TGB with HUMS detection,
Particle detector for TR input Bearing, checked on an hourly basis.
Also has an electrical chip detector and 5 mag plugs on each engine
as an engineering decision, checking plugs after every flight may not be mandated, but as i said, im happy to do that personally if it helps to ease the stress on those who have to fly on them.
not really sure why the tech lesson was directed at me, i was only stating a fact as to what happens on the a/c i work on. i am type rated on L2 and other types, so am well aware of the chip detectors in the system.
L2 has Sump detector with "XMSN" caption on 10ww panel and Warnings
flared housing, manual detection on hourly based removal (19mm spanner)
epicyclic with HUMS detection,
IGB with HUMS detection,
TGB with HUMS detection,
Particle detector for TR input Bearing, checked on an hourly basis.
Also has an electrical chip detector and 5 mag plugs on each engine
as an engineering decision, checking plugs after every flight may not be mandated, but as i said, im happy to do that personally if it helps to ease the stress on those who have to fly on them.
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2 + 2 = ???
If a 332 pilot now gets an MGB chip light 100 miles offshore does he:-
a) Abandon the flight and land on the nearest platform
b) Abandon the flight and ditch immediately
c) Continue flight to base
Would the answer be different for each model? (L1, L2 225)
G
a) Abandon the flight and land on the nearest platform
b) Abandon the flight and ditch immediately
c) Continue flight to base
Would the answer be different for each model? (L1, L2 225)
G
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i think i would go for A in todays climate. chip light isnt necessarily a warning of impending failure, so continuing to the nearest platform or land base might be prudent. easier to land it and get an engineer to go look at it that take the chance of continuing the flight as normal. im sure that the other engineers and dare i say it? the armchair engineers on this thread might disagree!!! but i suppose discussion is healthy is it not?
since failure of the epycyclic gearing is thought to be the cause, but how did the head separate when it is held to the gearbox by a ring of bolts, and also held to aircraft by three suspension bars? must have been an incredably violent torque to have ripped the lot off?
since failure of the epycyclic gearing is thought to be the cause, but how did the head separate when it is held to the gearbox by a ring of bolts, and also held to aircraft by three suspension bars? must have been an incredably violent torque to have ripped the lot off?
Last edited by you want what??; 11th Apr 2009 at 18:35.
Geoffers...
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For mckeg4's benefit I would ask how many main gear box failures have there been? And just think of how many flights there are on the North Sea and around the world. Yes there have been cases of gear boxes 'making metal', but catastrophic failures like this are extremely rare. The only one that comes to my mind at the moment is the Bristow's Puma 9M-SSC out of Lutong, Sarawak back in December 1980. There may have been others, but I can't think of any at the moment. Generally more frequent (but still rare) incidents are with tailrotor or other failures which are surviveable.
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Questions
Two questions:
What is the all up weight of a north sea puma?
What alt would this a/c have been at this stage of the flight?
I've a couple of laymans thoughts, but don't want to post them until I'm sure of my facts. wholly inappropriate to do otherwise.
What is the all up weight of a north sea puma?
What alt would this a/c have been at this stage of the flight?
I've a couple of laymans thoughts, but don't want to post them until I'm sure of my facts. wholly inappropriate to do otherwise.
With regards to the daily inspection of the epicyclic magnetic chip detectors were the the chip detectors tested at the same time? The PT6 engine and cgb magnetic detectors on the Bell 212 had to be checked at regular intervals by holding a certain weight of metal, I forget the actual weight but it was considerably above a few chips.
This problem may result in Eurocopter in supplying replacement MGB's equipped with tested epicyclic gearing hopefully free of charge.
This problem may result in Eurocopter in supplying replacement MGB's equipped with tested epicyclic gearing hopefully free of charge.
Standto
From the AAIB report.
http://www.aaib.gov.uk/cms_resources...B%20Report.pdf
Dave
Recorded radar information showed the aircraft flying inbound towards Aberdeen at 2,000 ft,
climbing momentarily to 2,200 ft and then turning right and descending rapidly.
Dave
I have had two MRGB chips offshore in Puma. One was shortly after the box produced some fine chips in a previous flight. Thankfully not too far offshore, turned around. Second was waaaaay offshore and out of the blue. Landed on a ship, where upon investigation, some decent chips were found. Hover checked and found some more. Left the machine there and picked up to gladly go back to shore.
Both of those boxes were replaced.
In my experience, and most importantly from what I have been told by olds-and-bolds, is that French machines don't produce chips unless there is something wrong (unlike Yank machines). If there is a chip-trend on a French machine (i.e. another indication after cleaning the plug), I wouldn't be taking it offshore. They can sack me, but there's no way I would do it. Call me a chicken, but that's just my policy (before the latest event).
Just sayin...
Both of those boxes were replaced.
In my experience, and most importantly from what I have been told by olds-and-bolds, is that French machines don't produce chips unless there is something wrong (unlike Yank machines). If there is a chip-trend on a French machine (i.e. another indication after cleaning the plug), I wouldn't be taking it offshore. They can sack me, but there's no way I would do it. Call me a chicken, but that's just my policy (before the latest event).
Just sayin...
What-ho
Early Bristow Pumas had an, then, Aerospat team on site changing transmissions daily due to chips.
In 2003 I was told by the OGP that the 155 transmission never made it pass about 1500 hours before removal. Why? Chips.
At a CAA meeting Helikopter Service reported bearing problems on the latest Pumas where chips from an accessory gearbox could contaminate the main xmsn. They were changing boxes every 130 hours or so. Kind of like Bristow experience with early Pumas.
Makes American transmissions look pretty good.
The Sultan
Early Bristow Pumas had an, then, Aerospat team on site changing transmissions daily due to chips.
In 2003 I was told by the OGP that the 155 transmission never made it pass about 1500 hours before removal. Why? Chips.
At a CAA meeting Helikopter Service reported bearing problems on the latest Pumas where chips from an accessory gearbox could contaminate the main xmsn. They were changing boxes every 130 hours or so. Kind of like Bristow experience with early Pumas.
Makes American transmissions look pretty good.
The Sultan
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You want what
As a fellow engineer, i have seen first hand, a gearbox complete with gearbox suspension bars,head and blades ripped out from the box structure Download report:
AS355F1, G-XCEL 07-06.pdf (888.58 kb) the forces involved are incredibly high.
It is only my supposition, looking from the photo's of the wreckage, that the head separated at the ring gear casing (conical housing) to main gearbox casing.
With regard to the inspection of the gearboxes would it not have been prudent of the authorities to ground these machines, until a visual inspection of the epicyclic gears has been carried out?
As a fellow engineer, i have seen first hand, a gearbox complete with gearbox suspension bars,head and blades ripped out from the box structure Download report:
AS355F1, G-XCEL 07-06.pdf (888.58 kb) the forces involved are incredibly high.It is only my supposition, looking from the photo's of the wreckage, that the head separated at the ring gear casing (conical housing) to main gearbox casing.
With regard to the inspection of the gearboxes would it not have been prudent of the authorities to ground these machines, until a visual inspection of the epicyclic gears has been carried out?
Last edited by rapman; 12th Apr 2009 at 02:30. Reason: spelling
...So much maligned JF was right after all.The tail did separate and the tail rotor was not under power when it hit the water.
That and the fact that the MRH had clearly separated from the MGB was pretty obvious to any layman with a basic knowledge of helicopters looking at the recovery pictures.
His mistake was saying so ?
That and the fact that the MRH had clearly separated from the MGB was pretty obvious to any layman with a basic knowledge of helicopters looking at the recovery pictures.
His mistake was saying so ?