North Sea heli ditching: Oct 2012
The work still continues but now under the auspices of EASA.
No, the intention is not to keep the aircraft in an upright position - with the high C of G that is almost impossible - but to ensure that it reaches a predictable position, with an air cavity, so that escape is possible for a reasonable period.
It can also be used in addition to conventional floatation bags should the sea conditions be benign enough to permit a dry escape.
I agree with the poster who said that there was a great deal of luck involved in these ditchings; had they occurred on the extensive period of time when the sea state is greater than SS 4 there might have been a different outcome.
Well done the crews in both incidents.
Jim
No, the intention is not to keep the aircraft in an upright position - with the high C of G that is almost impossible - but to ensure that it reaches a predictable position, with an air cavity, so that escape is possible for a reasonable period.
It can also be used in addition to conventional floatation bags should the sea conditions be benign enough to permit a dry escape.
I agree with the poster who said that there was a great deal of luck involved in these ditchings; had they occurred on the extensive period of time when the sea state is greater than SS 4 there might have been a different outcome.
Well done the crews in both incidents.
Jim
Last edited by JimL; 26th Nov 2012 at 18:34.
http://www.easa.europa.eu/rulemaking...inalreport.pdf
For those who like pretty pictures and loads of data.
Some thought about unintended consequences needs to be done.....for you Bell 212/412 Pilots....imagine getting out of one of them if it were laid nicely over on its side! For a well seat passenger on the bottom....bad news. For the Well seat passengers on the top...no problem. For the main cabin gang....where would you put the step ladder?
For those who like pretty pictures and loads of data.
Some thought about unintended consequences needs to be done.....for you Bell 212/412 Pilots....imagine getting out of one of them if it were laid nicely over on its side! For a well seat passenger on the bottom....bad news. For the Well seat passengers on the top...no problem. For the main cabin gang....where would you put the step ladder?
Last edited by SASless; 26th Nov 2012 at 21:04.
For the record, I have never been in favour of the side floating concept but CAA were determined to go ahead with the research anyway. Nothing wrong with research but as SAS says, the unintended consequences need to be carefully considered, such as unintentional inflation in flight and the decreased upright stability resulting from more mass high up, and increased windage.
Remind me, when did the last Super Puma family aircraft make a controlled ditching and go upside down before everyone got out? Of course there was the N Cormorant uncontrolled arrival in water, but not sure if the extent of water impact damage and g forces would have allowed a greater survival rate if cowling floats had been installed and had automatic inflation. That was 25 years ago of course.
Remind me, when did the last Super Puma family aircraft make a controlled ditching and go upside down before everyone got out? Of course there was the N Cormorant uncontrolled arrival in water, but not sure if the extent of water impact damage and g forces would have allowed a greater survival rate if cowling floats had been installed and had automatic inflation. That was 25 years ago of course.
Last edited by HeliComparator; 26th Nov 2012 at 21:29.
http://www.easa.europa.eu/rulemaking...inalreport.pdf
Some thought about unintended consequences needs to be done.....for you Bell 212/412 Pilots....imagine getting out of one of them if it were laid nicely over on its side! For a well seat passenger on the bottom....bad news. For the Well seat passengers on the top...no problem. For the main cabin gang....where would you put the step ladder?
Some thought about unintended consequences needs to be done.....for you Bell 212/412 Pilots....imagine getting out of one of them if it were laid nicely over on its side! For a well seat passenger on the bottom....bad news. For the Well seat passengers on the top...no problem. For the main cabin gang....where would you put the step ladder?
That was (supposedly) dealt with after the 1978 Bell 212 rollover on Nordraug in the Brent. The legs of the rear seat row are supposed to be marked and used as a ladder to climb up to the top door.
But maybe that bit of 'Corporate knowledge' has been lost in the mists of time?
Air Accidents Investigation: S7/2012 - EC225 LP Super Puma, G-CHCN
Summary:
This Special Bulletin contains information on the progress of the investigation into identifying the cause of the 360º circumferential crack in the bevel gear vertical shaft on G-CHCN (AAIB Special Bulletin S6/2012). It also compares the findings with those recorded previously on another EC225 LP accident involving a similar failure on G-REDW on 10 May 2012 (AAIB Special Bulletin S3/2012) and provides a further update on the investigation into both accidents.
The Chief Inspector of Air Accidents has ordered that the investigations into the accident to G-REDW on 10 May 2012 and to G-CHCN on 22 October 2012 be combined, and to publish an Inspector’s Investigation Report.
This Special Bulletin contains information on the progress of the investigation into identifying the cause of the 360º circumferential crack in the bevel gear vertical shaft on G-CHCN (AAIB Special Bulletin S6/2012). It also compares the findings with those recorded previously on another EC225 LP accident involving a similar failure on G-REDW on 10 May 2012 (AAIB Special Bulletin S3/2012) and provides a further update on the investigation into both accidents.
The Chief Inspector of Air Accidents has ordered that the investigations into the accident to G-REDW on 10 May 2012 and to G-CHCN on 22 October 2012 be combined, and to publish an Inspector’s Investigation Report.
Looking at the HUMS data anyone have an idea about the thresholds?
What I don't understand is how the EC defined maximum values have been calculated for the fleet. How can these be set so far away from the "real" learned thresholds (as you can see from the data of CHCN and REDW) - is the variance so marked across the whole fleet that you might see other EC225's operating and thus the need for such vast headroom?
The next query is around the actual learned amber threshold difference between CHCN and REDW for MOD45. REDW seems to have a threshold twice that of CHCN, now given these are "learned" what changed, because the data you can see plotted would not suggest the logic with these systems is the same.
Finally how do you reconcile the data you can see here with EC's recommendations post REDW?
What I don't understand is how the EC defined maximum values have been calculated for the fleet. How can these be set so far away from the "real" learned thresholds (as you can see from the data of CHCN and REDW) - is the variance so marked across the whole fleet that you might see other EC225's operating and thus the need for such vast headroom?
The next query is around the actual learned amber threshold difference between CHCN and REDW for MOD45. REDW seems to have a threshold twice that of CHCN, now given these are "learned" what changed, because the data you can see plotted would not suggest the logic with these systems is the same.
Finally how do you reconcile the data you can see here with EC's recommendations post REDW?
Last edited by Pittsextra; 29th Nov 2012 at 19:07.
John,
But then we also learned about the cabin floor mat that floats up as did the foam seat cushions
But then we also learned about the cabin floor mat that floats up as did the foam seat cushions
Join Date: Sep 2007
Location: USA
Posts: 601
Likes: 0
Received 0 Likes
on
0 Posts
Bravo73,
Thanks for the report link.
It was interesting to learn why the 4mm hole was drilled into the weld joint. With the circumferential EB/laser type weld used on the bevel gear shaft, even though the process is highly automated there can be a small metallurgically deficient area right where the weld starts/ends. The reason there can be problems at the start/end point of the weld is this point is subject to fairly rapid heating/cooling as energy input from the EB or laser starts/stops. The metallurgical deficiency can take the form of small cracks, hot tears, cold laps, seams, etc.
The report does not come to a conclusion about what caused the initiation of the cracks, but it does show a fair amount of surface corrosion around the ID of the shaft. It's a bit unusual to see surface corrosion on the internal components of MGB's any more. It is standard design practice to use desiccant breather systems on MGB's, which are very effective at removing moisture from the air volume inside the housing. However, I don't know if this particular MGB used such a breather system.
Lastly, it was also interesting to read that the design and material of this particular bevel gear was changed to use a nitride case hardening process instead of carburizing. It's unusual to use nitriding for a spiral bevel gear because the case thickness is typically far less than with carburizing. Also, the hardness of the nitrided case drops off rapidly away from the surface, so the hardness of the remaining surface after finish grinding can be less than optimum. Spiral bevel gears tend to have high flank contact stress, so case hardness and depth are important for fatigue life.
Sorry if my posts are boring to some of you, but I find the topic of gearbox design very interesting.
Thanks for the report link.
It was interesting to learn why the 4mm hole was drilled into the weld joint. With the circumferential EB/laser type weld used on the bevel gear shaft, even though the process is highly automated there can be a small metallurgically deficient area right where the weld starts/ends. The reason there can be problems at the start/end point of the weld is this point is subject to fairly rapid heating/cooling as energy input from the EB or laser starts/stops. The metallurgical deficiency can take the form of small cracks, hot tears, cold laps, seams, etc.
The report does not come to a conclusion about what caused the initiation of the cracks, but it does show a fair amount of surface corrosion around the ID of the shaft. It's a bit unusual to see surface corrosion on the internal components of MGB's any more. It is standard design practice to use desiccant breather systems on MGB's, which are very effective at removing moisture from the air volume inside the housing. However, I don't know if this particular MGB used such a breather system.
Lastly, it was also interesting to read that the design and material of this particular bevel gear was changed to use a nitride case hardening process instead of carburizing. It's unusual to use nitriding for a spiral bevel gear because the case thickness is typically far less than with carburizing. Also, the hardness of the nitrided case drops off rapidly away from the surface, so the hardness of the remaining surface after finish grinding can be less than optimum. Spiral bevel gears tend to have high flank contact stress, so case hardness and depth are important for fatigue life.
Sorry if my posts are boring to some of you, but I find the topic of gearbox design very interesting.
Join Date: Sep 2012
Location: Planet Earth
Age: 63
Posts: 9
Likes: 0
Received 0 Likes
on
0 Posts
Marine Transfer Workgroup established
Wed 21st November
Step Change in Safety has established a new workgroup, focusing on the safe transfer of personnel offshore by means other than helicopter.
Due to the exceptional circumstances with a number of Aberdeen-based helicopters still suspended and impacting on the logistics of getting people on and offshore, transferring workers by other means – such as frog and walk-to-work – remains an option when helicopters are unavailable.
The new group, co-chaired by Bibby Offshore’s David Forsyth and BP’s Colin Gay, will initially look at pulling together existing guidance and information. This will arm companies with the facts to help them safely plan transfers and will help the workforce better understand what is involved should they agree to be transferred this way.
Marine transfer is commonplace in many parts of the world. Many of the global companies which carry this out elsewhere in the world are also based in Aberdeen – therefore there is an existing base of expertise and knowledge, despite the practise being less common in the UKCS.
The group, which will run until the helicopter situation is resolved, is looking for involvement from elected safety representatives. Anyone interested in joining the group should contact Step Change in Safety at [email protected] or phone 01224 577268.
Join Date: Dec 2003
Location: Scotland
Posts: 261
Likes: 0
Received 0 Likes
on
0 Posts
terminus mos
Isn't that happening right now? The S92 is now the 'dominant type' on the North Sea.
bondu
Thirdly, industry will never again relay on having a dominating type of helicopter. EC225s will be swapped for S-92s to reduce the risk of business disruption such has occurred since the grounding.
bondu
riff raff......you just keep boring us please....as some of us need an education on topics you are an expert on!
Riff Raff,
To add some bits to your post:
- nitrided depth is smaller than carburized depth, thus preventing, usually, the final grinding of big spiral bevel teeth, as you posted
- however, nitriding steel has some benefit, because, for instance, the nitriding process causes less distortion during heat treatment respect to carburizing, thus it is a good choice for big ring and helical gears.
- 32CDV13, on the other hand, is a bit peculiar, because combines the advantages of high core strength and the capability for deeper nitriding depth respect to classic nitralloys. With higher case hardened depth, you could grind a big spiral bevel teeth without encountering the difficulties you highlighted in your post. I imagine this is the rationale behind this change of material on ec225.
Anyway, the gear teeth are not particularly in discussion, they didn't fail, the shaft failed!
To add some bits to your post:
- nitrided depth is smaller than carburized depth, thus preventing, usually, the final grinding of big spiral bevel teeth, as you posted
- however, nitriding steel has some benefit, because, for instance, the nitriding process causes less distortion during heat treatment respect to carburizing, thus it is a good choice for big ring and helical gears.
- 32CDV13, on the other hand, is a bit peculiar, because combines the advantages of high core strength and the capability for deeper nitriding depth respect to classic nitralloys. With higher case hardened depth, you could grind a big spiral bevel teeth without encountering the difficulties you highlighted in your post. I imagine this is the rationale behind this change of material on ec225.
Anyway, the gear teeth are not particularly in discussion, they didn't fail, the shaft failed!
Perhaps it is time for CHC to bring its 365N2s out of retirement. Boat the oil workers to within a couple of miles of their destination then shuttle them onto the rigs.
It worked in the 40s/Piper/ETAP for many years and gets round the tricky transfer from the boat to the rig.
Plenty of shuttle qualified pilots about who would be willing to help out in these difficult times!
When not on holiday of course
HF
It worked in the 40s/Piper/ETAP for many years and gets round the tricky transfer from the boat to the rig.
Plenty of shuttle qualified pilots about who would be willing to help out in these difficult times!
When not on holiday of course
HF
