AS332L2 Ditching off Shetland: 23rd August 2013
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Oh dear, whatever caused the catastrophic loss of power also caused a catastrophic loss of confidence in the Super Puma family.
Offshore Oil workers start campaign against Super Puma helicopters.
Massive online support for Destroy The Super Pumas Facebook page | Scotland | News | STV
https://www.facebook.com/pages/Destr...49173595095243
Offshore Oil workers start campaign against Super Puma helicopters.
Massive online support for Destroy The Super Pumas Facebook page | Scotland | News | STV
https://www.facebook.com/pages/Destr...49173595095243
L2 engine fail towards idle
Lonewolf, you need to be familiar with the Norwegian Norne accident some years ago (that has been mentioned earlier in this thread) but basically, some damage was acruing in the high speed shaft caused by a loose nut (IIRC), this took out all N2 signals the engine ran up, then the damaged shaft failed and the turbine suffered a massive overspeed that caused fragments of the disc to sever the flight controls, take out the other engine, and kill some passengers before they hit the water.
As a result, the failure mode of the engine was made more benign - ie running to idle is better than an uncontained N2 overspeed especially in a twin.
The 332L and L2 have a manual emergency throttle so that, following such a run-down, the crew can advance the throttle to restore some (ungoverened) power on that engine.
I should add that its a pretty unlikely set of conditions that have to be met to make the engine run down, and its not something that happens often, if at all.
As a result, the failure mode of the engine was made more benign - ie running to idle is better than an uncontained N2 overspeed especially in a twin.
The 332L and L2 have a manual emergency throttle so that, following such a run-down, the crew can advance the throttle to restore some (ungoverened) power on that engine.
I should add that its a pretty unlikely set of conditions that have to be met to make the engine run down, and its not something that happens often, if at all.
Last edited by HeliComparator; 26th Aug 2013 at 17:20.
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Workers
Seems the pilots on here who have referred to the workers as 'Bears' and questioning their intelligence might get a few dirty looks at the hell-ports.
Most of them probably earn more than us and are highly skilled. Think you should watch how you refer to them in future, the link is public on their forums.
Most of them probably earn more than us and are highly skilled. Think you should watch how you refer to them in future, the link is public on their forums.
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Facebook: THAT page.
Shockingly inaccurate.
I was sure there were more than 31,548 idiots in the English-speaking world.
I was sure there were more than 31,548 idiots in the English-speaking world.
Last edited by jimf671; 26th Aug 2013 at 17:23.
A Default setting to Max Power in the event of a Engine Control system failure is fraught with peril.....especially if the aircraft has very strong engines.
I had one in an empty Chinook that was also low on Fuel.....it was amazing the Rotor Blades stayed with us! Sadly....when you raise the Lever to control the Nr.....the good engine followed and that gave us way...way....way too much Ooomph going to the Rotor System.
Shutting down the bad engine was the only answer in the failure I had.....and deciding which engine was the bad one was complicated by the screaming of the Gearboxes and Crew.
The giveaway was one Engine was way above Topping N-1.....and the other was at Topping N-1. Torques were close with the bad engine being higher than the good engine.
For you Wokka drivers....it was an N-2 Overspeed Drive Shaft Failure....before it was in the Checklist or Flight Manual.
I had one in an empty Chinook that was also low on Fuel.....it was amazing the Rotor Blades stayed with us! Sadly....when you raise the Lever to control the Nr.....the good engine followed and that gave us way...way....way too much Ooomph going to the Rotor System.
Shutting down the bad engine was the only answer in the failure I had.....and deciding which engine was the bad one was complicated by the screaming of the Gearboxes and Crew.
The giveaway was one Engine was way above Topping N-1.....and the other was at Topping N-1. Torques were close with the bad engine being higher than the good engine.
For you Wokka drivers....it was an N-2 Overspeed Drive Shaft Failure....before it was in the Checklist or Flight Manual.
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Thank you, UKPaxman, for your post 349, and the item that only three weeks ago, the Super Puma EC225, after "months of investigating, testing" flew again in service after the two previous ditchings. On this flight, which you say likely flew to Alwin North, the Chief Pilot and Senior Managers of the company did indeed fly as passengers. Respect.
Helicomparator mentions in post 301 that high level floats are still under consideration by EASA, more than a year ago. The performance of the floats saved everyone on board in the two previous ditchings, the surface of the sea did not seem so friendly this time.
Helicomparator mentions in post 301 that high level floats are still under consideration by EASA, more than a year ago. The performance of the floats saved everyone on board in the two previous ditchings, the surface of the sea did not seem so friendly this time.
Nomorehelosforme, The CVFDR is in the tail cone, or is on the 332L, so unless they have picked that up and it (the CVFDR) hasn't detached itself they haven't yet got there hands on it.
With the currents around there it could travel some distance but there's a 30 day pinger on it so they still should find it.
With the currents around there it could travel some distance but there's a 30 day pinger on it so they still should find it.
Last edited by Sevarg; 26th Aug 2013 at 18:05. Reason: To add (the CVFDR)
Reported on Radio Shetland that the search continues for the tail section 'containing the black box'. Certainly looks from the Marinetraffic plot that the Bibby Polaris is conducting a slow and thorough search close to the extended centreline of 09/27 and south of Garths Ness.
Last edited by Little cloud; 26th Aug 2013 at 18:59.
Mary, the effectiveness of the floats this time was more to do with the rapidity of arrival on the sea rather than the sea state. No flotation system can reasonably be designed to work following an unlimited energy arrival. So you could beef them up a bit such that they worked in a "minor crash" but at some point, the crash severity is going to be such that they don't remain intact. They are designed for ditching, not for crashing.
Data
Thanks, LC. Am I correct in thinking that the pilot statements will be kept private until the CVR/FDR data is examined?
Last edited by JohnDixson; 26th Aug 2013 at 18:46. Reason: Typo
HC,
Are the SP floats Pilot inflated or Pilot armed and auto inflate using "water" switches?
Are the SP floats Pilot inflated or Pilot armed and auto inflate using "water" switches?
fundamental aircraft fault
Moodyman, sorry missed your post.
You are correct that there was a flaw (or several!) in the backup to the backup lubrication system. Bearing in mind that this system gives you 30 mins at 80kts (40nm), I think at least one of those events was more than 40 nm from shore, so the outcome would have been the same. However most of us think that the best option, regardless of the EMLUBE indications, is to put down in the sea if the sea state is reasonably benign, especially following transmission indications that are not "textbook". So I question whether the outcome would have been different had the EMLUBE captions not come on. In any case, the system was designed to cope following total oil loss, not a broken shaft.
But the key point with those ditchings is that they resulted from the shafts developing a fault. All helicopters develop faults, its just the nature of the complex beast. What is important is to have means to detect the developing faults before they become critical, and for that we have various tools including HUMS.
The existing HUMS tools was quite capable of detecting the fault before it became critical, but unfortunately the tool was not used optimally and so the fault went undetected until the shaft broke.
You are correct that there was a flaw (or several!) in the backup to the backup lubrication system. Bearing in mind that this system gives you 30 mins at 80kts (40nm), I think at least one of those events was more than 40 nm from shore, so the outcome would have been the same. However most of us think that the best option, regardless of the EMLUBE indications, is to put down in the sea if the sea state is reasonably benign, especially following transmission indications that are not "textbook". So I question whether the outcome would have been different had the EMLUBE captions not come on. In any case, the system was designed to cope following total oil loss, not a broken shaft.
But the key point with those ditchings is that they resulted from the shafts developing a fault. All helicopters develop faults, its just the nature of the complex beast. What is important is to have means to detect the developing faults before they become critical, and for that we have various tools including HUMS.
The existing HUMS tools was quite capable of detecting the fault before it became critical, but unfortunately the tool was not used optimally and so the fault went undetected until the shaft broke.
Last edited by HeliComparator; 26th Aug 2013 at 19:10.
SAS, the floats have to be armed before anything can happen. Then, optimally they are inflated by the pilots at low speed before alighting on the water. If the pilots forget or don't have time, they are fired by float switches but only if they have been armed. There are airspeed limits for float inflation (the max speed that the test pilots dared to fly at with the floats inflated) and you can't have a system that could malfunction and inflate the floats when above that speed (which is 150 for a 225, 80 for a 92, and can't remember for an L2 but maybe 130?). That is why the pilots must slow down to below that speed prior to arming the floats.
Last edited by HeliComparator; 26th Aug 2013 at 19:08.
Those speeds are for fully inflated floats I assume.....and I wonder what effect "speed" would have on the float bags as they inflate as there would be quite a bit of flapping around in the wind stream until they were pressurized and "solid".
When the testing was being done on the High Side Floats.....was there any consideration given to using fewer low bags or smaller low bags to compensate for the extra flotation provided by the High Side Bags?
Also...forgot to ask....."Saltwater Immersion Switches" or will they activate automatically in fresh water as well?
When the testing was being done on the High Side Floats.....was there any consideration given to using fewer low bags or smaller low bags to compensate for the extra flotation provided by the High Side Bags?
Also...forgot to ask....."Saltwater Immersion Switches" or will they activate automatically in fresh water as well?
Last edited by SASless; 26th Aug 2013 at 19:13.
SAS, I think the criteria will be the ablity to inflate at high speed without damaging the aircraft's ability to continue flight, rather than necessarily no damage to the float bags themselves. But they do inflate pretty quickly, more of an explosion that an inflate.
Although there has been some debate about this, my opinion is that the high level floats should only come into play if the heli rolls over, therefore the normal floats should be unchanged. Experience (too much of it!) has shown that following a controlled ditching, the heli will stay upright in some surprisingly poor sea states. Personally I'd rather evacuate with my clothes dry if possible!
Float switches, that will work in any type of water.
Although there has been some debate about this, my opinion is that the high level floats should only come into play if the heli rolls over, therefore the normal floats should be unchanged. Experience (too much of it!) has shown that following a controlled ditching, the heli will stay upright in some surprisingly poor sea states. Personally I'd rather evacuate with my clothes dry if possible!
Float switches, that will work in any type of water.
Last edited by HeliComparator; 26th Aug 2013 at 19:19.
In the old days
In the early 80's we used to fly North Sea as pax on S-61s and on long night flights the stewardesses would serve drinks all round. Like a fixed wing a/c there were no survival suits worn. How this has changed.
The last time in 2012 I did the BOSIET refresher helicopter evacuation course I found the re-breather apparatus a great help and should allow you about 20 or so usable breaths under water.
It will interesting to see as to whether the survivors were able to prepare and don theirs before the rotors stopped rotating and the hull inverted and of course the evacuate command issued.
I just wonder if more could have been done to retrieve the poor trapped soul which didn't make it out. But judging by the frame photos, the hull didn't appear to suffer much damage so a descent rate of less 500'/m would seem likely which makes you wonder about press reports by pax of the craft 'falling rapidly'.
The last time in 2012 I did the BOSIET refresher helicopter evacuation course I found the re-breather apparatus a great help and should allow you about 20 or so usable breaths under water.
It will interesting to see as to whether the survivors were able to prepare and don theirs before the rotors stopped rotating and the hull inverted and of course the evacuate command issued.
I just wonder if more could have been done to retrieve the poor trapped soul which didn't make it out. But judging by the frame photos, the hull didn't appear to suffer much damage so a descent rate of less 500'/m would seem likely which makes you wonder about press reports by pax of the craft 'falling rapidly'.
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HC,
Maybe on the second 225 ditching, but the Bond G-REDW AAIB report quite clearly says that Bond picked up a trend on the day before the ditching, and again after first flight on the day itself, carried out the AMM actions in both cases, and put the ac on close monitoring, all completely in accordance with the AMM. Could they have looked more closely, maybe, I'm sure you'll tell us Bristow would have done, but to say they did not detect it because they were not using HUMS properly is untrue.
Page 7 if you're interested:
http://www.aaib.gov.uk/cms_resources...2%20G-REDW.pdf
The existing HUMS tools was quite capable of detecting the fault before it became critical, but unfortunately the tool was not used optimally and so the fault went undetected until the shaft broke.
Page 7 if you're interested:
http://www.aaib.gov.uk/cms_resources...2%20G-REDW.pdf