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

Hi Jim, why do you say SS 4 as opposed to SS 6, which the EC225 floats are demonstrated at?

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 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.

HC, G TIGH 14th March 1992, more like 20 years.

Thanks II, for some reason I had it in my head it was 1987.

SAS,

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

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?

John,

But then we also learned about the cabin floor mat that floats up as did the foam seat cushions

What's happened to g-redw and chcn? Scrapped?

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.

Riff Raff: Your aeronautical and engineering perspectives are always much valued and provide welcome reading.

It seems the North Sea oil companies are planning for a shortage in helicopter capacity for quite a while. Hope their new transport arrangements don't become permanent :(

terminus mos

Isn't that happening right now? The S92 is now the 'dominant type' on the North Sea.

bondu

riff raff......you just keep boring us please....as some of us need an education on topics you are an expert on!

Seconded.

Si

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!

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

Riff Raff,

I love education bro, and ur posts are educational - keep the info coming :ok: