Heli 'collides with gas rig' 11-Mar-08
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AAIB Report Now Published
I wonder why some people on this thread wanted to dismiss this.
http://www.aaib.gov.uk/sites/aaib/cm...XD%2007-08.pdf
What news on the review on shuttling?
http://www.aaib.gov.uk/sites/aaib/cm...XD%2007-08.pdf
What news on the review on shuttling?
Helicopter performance
The helicopter was operating close to its maximum operating weight when it approached the helideck on the accident flight. The commander believed that the helicopter’s performance at that weight was such that it would not be possible for it to hover OGE with the power available. Changes in airflow around and through the rotor disc of a helicopter hovering close to the surface in ground effect (IGE) lead to increased rotor blade efficiency. Less power is therefore required to hover at a given weight when compared to a higher, OGE hover. In situations where performance is limited, the helicopter needs to make a continuous and steady approach to a landing site, so that it gains the benefits of ground effect before losing the extra lift that is a function of forward airspeed.
The helicopter was operating close to its maximum operating weight when it approached the helideck on the accident flight. The commander believed that the helicopter’s performance at that weight was such that it would not be possible for it to hover OGE with the power available. Changes in airflow around and through the rotor disc of a helicopter hovering close to the surface in ground effect (IGE) lead to increased rotor blade efficiency. Less power is therefore required to hover at a given weight when compared to a higher, OGE hover. In situations where performance is limited, the helicopter needs to make a continuous and steady approach to a landing site, so that it gains the benefits of ground effect before losing the extra lift that is a function of forward airspeed.
In addition, and as indicated (indirectly) by the accident investigator, taking the landing from the P2s side would also have added at least 10kts to the accountable wind (shown in the report as 12kts – 20kts), as the committal point - on that side - would have been achieved with at least 10kts more airspeed (one of the benefits of the dynamic over the offset procedure).
Jim
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Sad thing is, with the attitude of "Well its only a little thing" sadly I have found in life that Little things normally turn to
Farking Big Things pretty dam quickly, and far from posters being lambasted for saying so, certain people should be counting their blessings,.......... and really thats not how to be professional, blessings are for Priests, but accuracy is for CPL H pilots.
Vfrpilotpb/2
Farking Big Things pretty dam quickly, and far from posters being lambasted for saying so, certain people should be counting their blessings,.......... and really thats not how to be professional, blessings are for Priests, but accuracy is for CPL H pilots.
Vfrpilotpb/2
The Veloceraptor of Lounge Lizards
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JimL;
A quick scan of an old logbook shoes that you and I landed on the Alpha 11 times in one sortie in 1991, I've not bothered to count how many landings on that platform over a five year period, sadly it seems that the lessons learned on that operation over a considerable period of time have not been passed on.
With the benefit of hindsight a dynamic approach would have been better, I just wonder as well how much crew fatigue came into play. I always found that towards the end of a two week offshore stint I was utterly knackered.
VH
A quick scan of an old logbook shoes that you and I landed on the Alpha 11 times in one sortie in 1991, I've not bothered to count how many landings on that platform over a five year period, sadly it seems that the lessons learned on that operation over a considerable period of time have not been passed on.
With the benefit of hindsight a dynamic approach would have been better, I just wonder as well how much crew fatigue came into play. I always found that towards the end of a two week offshore stint I was utterly knackered.
VH
Now we have had a chance to read the accident report we can comment with rather more assurance on some of the issues.
The first thing to be said is that ‘manfromuncle’ was absolutely correct in referring to the ‘Brent Spa’ accident; the similarities are remarkable but, fortunately, the consequences were different. ‘Greeny9’, in castigating ‘manfromuncle’, was not familiar enough with the ‘Brent Spa’ to see those similarities (those of us who were around at the time of the Spa certainly could) and might now regret his outburst:
Clearly, no lesson learnt there.
It is unlikely that performance was an issue here (perceived performance may have been, hence the decision leading to an unsafe dynamic approach); however, this remains an unknown because is it unlikely that mass calculations were carried out for this sector. The fact is that a helicopter with perceived poor performance was probably saved by its unique design.
Recent discussions have indicated that performing complex mass calculations would not be welcomed by North Sea pilots. That does not mean that calculations should not be done, merely that the procedures should be made less complicated (or automated).
Having previously pointed out that limitations in operating mass have to be observed (still air AEO HOGE, second segment climb and en-route performance), it might be useful to point out that there have, recently, been improvements to manufacturer’s documentation which now permit a single, and simple, calculation.
After what seems like years of discussions, Bell has put into the RFM a helideck PC2 WAT graph that includes all but the en-route performance (it also incorporates deck-edge clearance) – wind accountability is provided but bounded so that the other limits are not broached. Another graph provides drop-down so we have the ability (at least for one helicopter) to produce Pure PC2 and PC2e take-off and landing masses.
‘verticalhold’ asks whether fatigue was an element; certainly it had been a long duty day (albeit split) and it is well known that decisions can be effected by fatigue – whether fatigue cause by loss of sleep or by length of time on duty.
Finally, we need to address the question of whether the nomination of the handling pilot for the sortie dictates who takes the landing or take-off for each sector. My view is (and always has been) that each landing or take-off in a multi-sector sortie should be dealt with individually, and on its merits. A compromise (in my day) was that the paperwork was always completed by the nominated PNH (to reduce the hand-over problems) but the landing, or take-off, was allocated to the best and safest side (give or take a couple of degrees).
This accident has provided an ideal opportunity to air a number of these issues. Fortunately, we need not be too conservative in our opinions because there is no need to take the feelings of bereaved relatives into consideration.
Jim
The first thing to be said is that ‘manfromuncle’ was absolutely correct in referring to the ‘Brent Spa’ accident; the similarities are remarkable but, fortunately, the consequences were different. ‘Greeny9’, in castigating ‘manfromuncle’, was not familiar enough with the ‘Brent Spa’ to see those similarities (those of us who were around at the time of the Spa certainly could) and might now regret his outburst:
Why are people comparing Brent Spa to Leman 27AD?
There is no comparison!
There is no comparison!
It is unlikely that performance was an issue here (perceived performance may have been, hence the decision leading to an unsafe dynamic approach); however, this remains an unknown because is it unlikely that mass calculations were carried out for this sector. The fact is that a helicopter with perceived poor performance was probably saved by its unique design.
Recent discussions have indicated that performing complex mass calculations would not be welcomed by North Sea pilots. That does not mean that calculations should not be done, merely that the procedures should be made less complicated (or automated).
Having previously pointed out that limitations in operating mass have to be observed (still air AEO HOGE, second segment climb and en-route performance), it might be useful to point out that there have, recently, been improvements to manufacturer’s documentation which now permit a single, and simple, calculation.
After what seems like years of discussions, Bell has put into the RFM a helideck PC2 WAT graph that includes all but the en-route performance (it also incorporates deck-edge clearance) – wind accountability is provided but bounded so that the other limits are not broached. Another graph provides drop-down so we have the ability (at least for one helicopter) to produce Pure PC2 and PC2e take-off and landing masses.
‘verticalhold’ asks whether fatigue was an element; certainly it had been a long duty day (albeit split) and it is well known that decisions can be effected by fatigue – whether fatigue cause by loss of sleep or by length of time on duty.
Finally, we need to address the question of whether the nomination of the handling pilot for the sortie dictates who takes the landing or take-off for each sector. My view is (and always has been) that each landing or take-off in a multi-sector sortie should be dealt with individually, and on its merits. A compromise (in my day) was that the paperwork was always completed by the nominated PNH (to reduce the hand-over problems) but the landing, or take-off, was allocated to the best and safest side (give or take a couple of degrees).
This accident has provided an ideal opportunity to air a number of these issues. Fortunately, we need not be too conservative in our opinions because there is no need to take the feelings of bereaved relatives into consideration.
Jim
Last edited by JimL; 11th Jul 2008 at 15:11. Reason: Change OEI to AEO
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The rumour over here is that Vancouver were not amused at what was being said on PPRuNe and ordered a quick internal investigation to offer up to AAIB fast in the hope that at least this incident would be 'cleared up' to keep First Reserve happy.
I repeat 'rumour' only.
I repeat 'rumour' only.
As the crew survived....hopefully in time an honest, frank, lessons learned statement might be forthcoming by the crew.
Rather than heaping blame and insult on the crew, perhaps we should be glad the accident turned out the way it did and thus it can be used to improve policy, procedure, and perhaps even mindset about offshore shuttle operations.
This a perfect situation for being turned into something useful if CHC, the Crew, CAA, and AAIB can find a way to do so. If I were to be involved as a crew member I would certainly prefer to see such a thing rather than being held up for a game of Pin the Tail on the Donkey.
The beauty of this event is no one got hurt and only some sheet metal and cast iron got bent thus no great liability to admitting to what one's role in the matter was.
In a perfect world, and a sincere safety culture, that is what would happen....a good analysis and published lessons learned.
Rather than heaping blame and insult on the crew, perhaps we should be glad the accident turned out the way it did and thus it can be used to improve policy, procedure, and perhaps even mindset about offshore shuttle operations.
This a perfect situation for being turned into something useful if CHC, the Crew, CAA, and AAIB can find a way to do so. If I were to be involved as a crew member I would certainly prefer to see such a thing rather than being held up for a game of Pin the Tail on the Donkey.
The beauty of this event is no one got hurt and only some sheet metal and cast iron got bent thus no great liability to admitting to what one's role in the matter was.
In a perfect world, and a sincere safety culture, that is what would happen....a good analysis and published lessons learned.
Well for a while anyway!
Who was the genius that elected NOT to change the tail rotor gearbox prior to the air test following repairs.
Seems the unchanged gearbox got smoking hot and showed ugly signs of not being serviceable and after it cooled down enough to be touched....was changed.
I wonder if the tail rotor drive shaft was changed?
Would the Eurocopter (Aerospatiale) tech manual set forth a "sudden stoppage" inspection procedure? Surely, the damage incurred during this incident would have justified such an inspection and component changes for everything involved.
Or am I being over cautious here?
Anyone in the loop that can explain just how that decision was arrived at?
Lt. Fubar in post number 61 of this thread posted the following.....
Who was the genius that elected NOT to change the tail rotor gearbox prior to the air test following repairs.
Seems the unchanged gearbox got smoking hot and showed ugly signs of not being serviceable and after it cooled down enough to be touched....was changed.
I wonder if the tail rotor drive shaft was changed?
Would the Eurocopter (Aerospatiale) tech manual set forth a "sudden stoppage" inspection procedure? Surely, the damage incurred during this incident would have justified such an inspection and component changes for everything involved.
Or am I being over cautious here?
Anyone in the loop that can explain just how that decision was arrived at?
Lt. Fubar in post number 61 of this thread posted the following.....
Well the fan was disaligned at the impact, so all of the blades will have to be replaced, the whole fenestron gearbox checked, repaired, or replaced, the duct will have to be replaced, so is the whole skin. Than the drive train, whole tail section checked for cracks, bends, material strains. Don't know where the tail fan drive train goes in the EC155, so that parts will have to be checked also.
Too cut it short - the while tail will have to striped down, checked and every component repaired/replaced. The whole thing is very serious - many fast-spinning, precise-machined, very important parts out there
Too cut it short - the while tail will have to striped down, checked and every component repaired/replaced. The whole thing is very serious - many fast-spinning, precise-machined, very important parts out there
it beggars belief!!
Hilico,
You have the makings of management at CHC it appears.....they arrived at the same conclusion after all the inspections were done.
Luckily it seems there were no injuries and the damage confined to the aircraft's TR.
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Hey, any time they want to give me a management position, with my years of experience in computer programming and local government, not to mention my 13 hours and 10 minutes PuT...
Actually the reason I started this thread is back in March I had just worked out how to surf the web on my new phone. I Googled the word 'helicopter' and this report was the first hit. Pure unbridled coincidence.
Actually the reason I started this thread is back in March I had just worked out how to surf the web on my new phone. I Googled the word 'helicopter' and this report was the first hit. Pure unbridled coincidence.
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I believe that the Huy engineers were also shocked that it wasn't changed.
"Boss, you'd think they'd tell us to change the gearbox or at least ask EC advice on an MGB that hasn't moved in 6 months...still what do we know.."
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It may have been fixed at EGNJ, but the engineers can only do what they can, given the materials supplied and carrying out orders from above.
Then let's hope that the same "above" will remember the decision not to change the MGB when it comes to the time to allocate the blame and act accordingly.
I still would not like to be in the guy who signed it off's shoes until then.
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Just to set the record straight:
The whole of the tail drive train was replaced.
The main gearbox did not overtemp.
A 15 minute hover check as required by the maintenance manual was carried out, and a decision to replace the gearbox was made following this.
All work carried out on this helicopter was done following a Eurocopter survey.
The whole of the tail drive train was replaced.
The main gearbox did not overtemp.
A 15 minute hover check as required by the maintenance manual was carried out, and a decision to replace the gearbox was made following this.
All work carried out on this helicopter was done following a Eurocopter survey.
Why was the gearbox changed?
What occurred in that fifteen minute hover check that prompted the change?
Whatever it was must have been convincing.....as fifteen minutes is not a very long time for "mortal" indications to exhibit themselves.
What occurred in that fifteen minute hover check that prompted the change?
Whatever it was must have been convincing.....as fifteen minutes is not a very long time for "mortal" indications to exhibit themselves.
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Don't get me wrong here, the engineers at NJ do a great job considering everything else.
Still must be worrying unless you know for sure that management will back you when the fan starts distributing the "stuff".
Air Test first....then heavy hover?
Perhaps it is my improving grasp of my own mortality....but would it not be more prudent to do the hover check prior to the air test in sequence. Cast iron failures at a hover would seem to be the more advantagous situation for such things to occur.
If a tranny is left setting without any attempt at preservation per recommended pickling practices....would not there be some concern for the integrity of the gearbox?
If the gearbox was in a climate controlled environment and secured properly from moisture....perhaps it would not be such a concern. Shoved over into a corner of the hangar while the reconstruction work was on-going for a period of six months....is another thing in my view.
Was someone trying to do this repair on the cheap at the expense of good sound engineering practices?
Perhaps it is my improving grasp of my own mortality....but would it not be more prudent to do the hover check prior to the air test in sequence. Cast iron failures at a hover would seem to be the more advantagous situation for such things to occur.
If a tranny is left setting without any attempt at preservation per recommended pickling practices....would not there be some concern for the integrity of the gearbox?
If the gearbox was in a climate controlled environment and secured properly from moisture....perhaps it would not be such a concern. Shoved over into a corner of the hangar while the reconstruction work was on-going for a period of six months....is another thing in my view.
Was someone trying to do this repair on the cheap at the expense of good sound engineering practices?
