North Sea heli ditching: Oct 2012
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It's in an EC bulletin (Safety information notice No. 2520-S-00)available to people who fly their products through the TIPI service and the text is:
So helicrazi are you standing in a corrected stance?
I'm off to bed, g'night.
Si
It has been established that all parts of the emergency lubrication system operated within their specifications.
During examination, glycol was found throughout the gearbox casing and on all the gears and bearings, which
remained in excellent condition.
This evidence indicates that the emergency lubrication system had activated and remained operational for the
duration of the flight. Therefore, the warning of system failure indicated to the flight crew was a false alarm and resulted in the crew making the decision to perform an immediate landing, as required by the Flight Manual.
During examination, glycol was found throughout the gearbox casing and on all the gears and bearings, which
remained in excellent condition.
This evidence indicates that the emergency lubrication system had activated and remained operational for the
duration of the flight. Therefore, the warning of system failure indicated to the flight crew was a false alarm and resulted in the crew making the decision to perform an immediate landing, as required by the Flight Manual.
Regarding the second ditching of an EC225 in October 2012:
An emergency lubrication warning light came on and resulted in the crew making the decision to perform a
controlled ditching, as required by the Flight Manual. The Main Gearbox has arrived at EUROCOPTER‘s
Marignane facility in order to launch a deeper investigation. As already indicated in the AAIB Special Bulletin
S6/2012, the initial visual examination has identified a 360° circumferential crack on the bevel gear vertical
shaft, in the vicinity of the weld that joins two sections of the shaft.
Additionally, the initial examinations performed in EUROCOPTER under the supervision of the AAIB have
shown that glycol was found throughout the gearbox casing and on all the gears and bearings. There appears to
be no visual evidence of heat distress or damage to any of the other components in the MGB, which seems to
indicate that the EMLUB system had operated.
An emergency lubrication warning light came on and resulted in the crew making the decision to perform a
controlled ditching, as required by the Flight Manual. The Main Gearbox has arrived at EUROCOPTER‘s
Marignane facility in order to launch a deeper investigation. As already indicated in the AAIB Special Bulletin
S6/2012, the initial visual examination has identified a 360° circumferential crack on the bevel gear vertical
shaft, in the vicinity of the weld that joins two sections of the shaft.
Additionally, the initial examinations performed in EUROCOPTER under the supervision of the AAIB have
shown that glycol was found throughout the gearbox casing and on all the gears and bearings. There appears to
be no visual evidence of heat distress or damage to any of the other components in the MGB, which seems to
indicate that the EMLUB system had operated.
I'm off to bed, g'night.
Si
Last edited by bigglesbutler; 16th Nov 2012 at 21:18.
Yes I am big enough and ugly enough to admit I stand corrected, that report states the rest of the gear box was in excellent condition, however, that was after a few minutes, I'm waiting to see if 30 mins would have the same outcome...
I'll leave my good colleague Biggles (Oh! I see that he's replied already) to continue our battle to gain your understanding, but I'll also reiterate something which seems to escape the attention of many.
There are two separate faults to be sorted out by EC, but neither one directly affects the other until the unthinkable and unpredictable events of May and October (perhaps slightly more predictable after May).
The external emlube system works just fine, except that a pressure switch (or switches) is probably set at the wrong value and tells the pilots falsely that the emlube system has failed.
The cracks which allowed the bevel shafts to drop off the bottom of the main shafts in both ditching scenarios have never manifested themselves before in over 4 million flying hours using the same shaft design.
Something got changed relating to factors affecting the shaft in the last 18 months or so and when the shafts failed, this exposed the latent problem in the pressure switches of the external emlube.
Two separate problems ! Both must be sorted out to everyone's satisfaction before the EC225 resumes normal operations.
There are two separate faults to be sorted out by EC, but neither one directly affects the other until the unthinkable and unpredictable events of May and October (perhaps slightly more predictable after May).
The external emlube system works just fine, except that a pressure switch (or switches) is probably set at the wrong value and tells the pilots falsely that the emlube system has failed.
The cracks which allowed the bevel shafts to drop off the bottom of the main shafts in both ditching scenarios have never manifested themselves before in over 4 million flying hours using the same shaft design.
Something got changed relating to factors affecting the shaft in the last 18 months or so and when the shafts failed, this exposed the latent problem in the pressure switches of the external emlube.
Two separate problems ! Both must be sorted out to everyone's satisfaction before the EC225 resumes normal operations.
Last edited by Colibri49; 16th Nov 2012 at 21:29.
Ok for my understanding, hopefully a simple yes/no answer:
If both oil pumps failed for a different reason, let's say 'sods law' and the shaft is in perfect working order, I am assuming the emlube would have been actived and functioning correctly as before, in this scenario would we have had the 'fail' indication? Or is the fail indiaction purely a symptom of the shaft failure?
If both oil pumps failed for a different reason, let's say 'sods law' and the shaft is in perfect working order, I am assuming the emlube would have been actived and functioning correctly as before, in this scenario would we have had the 'fail' indication? Or is the fail indiaction purely a symptom of the shaft failure?
"If both oil pumps failed for a different reason, let's say 'sods law' and the shaft is in perfect working order, I am assuming the emlube would have been actived and functioning correctly as before, in this scenario would we have had the 'fail' indication? Or is the fail indiaction purely a symptom of the shaft failure?"
My dear Sir. I'm struggling to answer your two questions with one word.
But to your "in this scenario would we have had the 'fail' indication?" my answer is "Yes" because the pressure switches are still faulty.
To your "is the fail indiaction purely a symptom of the shaft failure?" my answer is "No" because the shaft driving the pumps is inside the gearbox and has no connection with the external emlube system.
My dear Sir. I'm struggling to answer your two questions with one word.
But to your "in this scenario would we have had the 'fail' indication?" my answer is "Yes" because the pressure switches are still faulty.
To your "is the fail indiaction purely a symptom of the shaft failure?" my answer is "No" because the shaft driving the pumps is inside the gearbox and has no connection with the external emlube system.
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Bogus twin statistics
these are factors which are not correctly taken into account in the bogus calculations which support the twin engined philosophy .... AND ditching is not dangerous enough to risk the dangers of dodgy gearboxes which can be fatal..
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Helicrazy, the answer is no. As discussed the Emlube is a seperate system. There are 2 sensors on the emlube system. One for glycol pressure and one for p2.4 engine bleed air pressure. It was the p2.4 engine bleed air sensor that threw up the fail emlube caption. This system is in place for total loss of oil, not just loss of pressure due to pump failure. It is an add on and accounts for the mass of extra plumbing around the outside of the MGB. Hope this helps.
Helicrazi, the fail indication is simply that Emlube system has decided that it is not working correctly. It has nothing to do with the shaft, they are completely separate systems. In the event of indications of Total Loss of Oil Pressure, the Emlube is activated by the crew using a switch in the cockpit. If it works correctly, there will be no fail indication until the Glycol starts to run out about 30 minutes later. As far as the Emlube system is concerned, it does not matter what caused the loss of oil pressure, whether this is because ( as in these 2 cases) the shaft failed, or you may have a catastrophic oil leak, or 'Sods law' may have happened as you mentioned below.
However, your point about the balance of the MGB running without the big lump of metal welded to the bottom of the main shaft is, I think, important, and something EC needs to address in their testing.
However, your point about the balance of the MGB running without the big lump of metal welded to the bottom of the main shaft is, I think, important, and something EC needs to address in their testing.
Last edited by PlasticCabDriver; 16th Nov 2012 at 22:14. Reason: Others answered while I was typing!
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I think this may be the first time any Authority (in this case EASA), has predicated the safety of a helicopter based only on HUMS indications. There is no other inspection, visual or otherwise, required.
Does this mean that HUMS has finally come of age?
I know the oil companies and CAA have disregarded the AD but EASA are happy to let the 225 fly if HUMS is closely monitored. This is a big step forward.
Does this mean that HUMS has finally come of age?
I know the oil companies and CAA have disregarded the AD but EASA are happy to let the 225 fly if HUMS is closely monitored. This is a big step forward.
"However, your point about the balance of the MGB running without the big lump of metal welded to the bottom of the main shaft is, I think, important, and something EC needs to address in their testing."
If you look inside an actual gearbox at the relative size and mass of the main rotor shaft versus the bevel oil pump drive shaft, you will see that the analogy of "elephant vs mouse" would be apposite.
Furthermore, once the bevel shaft has dropped off the main shaft, there is no possibility of an imbalance arising, because the two shafts were centred on the same vertical axis before parting company.
It's about the same relationship in terms of vibrational consequences, as if a hub-cap dropped off your car wheel along the road. You wouldn't even notice it!
If you look inside an actual gearbox at the relative size and mass of the main rotor shaft versus the bevel oil pump drive shaft, you will see that the analogy of "elephant vs mouse" would be apposite.
Furthermore, once the bevel shaft has dropped off the main shaft, there is no possibility of an imbalance arising, because the two shafts were centred on the same vertical axis before parting company.
It's about the same relationship in terms of vibrational consequences, as if a hub-cap dropped off your car wheel along the road. You wouldn't even notice it!
Last edited by Colibri49; 16th Nov 2012 at 22:38.
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The shaft failures are just the final symptom. The root cause is more likely something else which changed in the last 18-24 months.
The nitrided steel shaft in question has 250,000 hours of flight time prior to May 2012 with no problems. EC is no longer looking at the shaft itself as being the root cause.
The nitrided steel shaft in question has 250,000 hours of flight time prior to May 2012 with no problems. EC is no longer looking at the shaft itself as being the root cause.
What is the 250k hours stat from? Its certainly not total hours from a fleet leader. In fact the gearbox that failed in October and May were very low hours.
In May the engineering analysis of G-REDW show that the broken components triggered the chip detectors in the sump I believe - which means bits of metal frag was in the oil.. That isn't good but for the fact the pumps aren't working so it goes nowhere unless of course you can suggest fragments travelled before the pumps fail totally (after all they got to the chip detectors).
Beyond that in the case of G-CHCN the HUMS data shows that the Red alarm threshold had been exceeded. So regardless of one pilot suggesting the vibration is insignificant it's significant enough to produce a red alarm.
The 30 min emergency lube is of course a safety net - but not in all circumstances. Given EC225 MGB issues since 2009 you would be almost crazy to continue flying for 30 mins knowing you had a MGB issue when you could have quickly ditched in flat sea alongside a ship. When bits of gearbox fire themselves out of the casing or you loose the main rotor parts being lubricated is irrelevant.
It is also wrong to say it's flown for millions of hours on the same design until 18 months ago. Were that the case you would find the fix to be simple.
This is a big mess - it's been poorly handled with very few on the same page. The worse situation is that there is conflicts between what best practice is and as we speak even EASA and the CAA can't agree how to deal with the EC225.
Seems EC have 'boxes on rigs and a helicopter about to start testing.
In May the engineering analysis of G-REDW show that the broken components triggered the chip detectors in the sump I believe - which means bits of metal frag was in the oil.. That isn't good but for the fact the pumps aren't working so it goes nowhere unless of course you can suggest fragments travelled before the pumps fail totally (after all they got to the chip detectors).
Beyond that in the case of G-CHCN the HUMS data shows that the Red alarm threshold had been exceeded. So regardless of one pilot suggesting the vibration is insignificant it's significant enough to produce a red alarm.
The 30 min emergency lube is of course a safety net - but not in all circumstances. Given EC225 MGB issues since 2009 you would be almost crazy to continue flying for 30 mins knowing you had a MGB issue when you could have quickly ditched in flat sea alongside a ship. When bits of gearbox fire themselves out of the casing or you loose the main rotor parts being lubricated is irrelevant.
It is also wrong to say it's flown for millions of hours on the same design until 18 months ago. Were that the case you would find the fix to be simple.
This is a big mess - it's been poorly handled with very few on the same page. The worse situation is that there is conflicts between what best practice is and as we speak even EASA and the CAA can't agree how to deal with the EC225.
Seems EC have 'boxes on rigs and a helicopter about to start testing.
Last edited by Pittsextra; 17th Nov 2012 at 08:28.
It is also wrong to say it's flown for millions of hours on the same design until 18 months ago. Were that the case you would find the fix to be simple.
All the bulletens are doing is trying to salvage some essential work out of the aircraft before that happens.
What is the 250k hours stat from? Its certainly not total hours from a fleet leader. In fact the gearbox that failed in October and May were very low hours.
Whoever stated that, presumably was taking a guess at the combined total hours of EC225 flying in the last approx 7years.
In May the engineering analysis of G-REDW show that the broken components triggered the chip detectors in the sump I believe - which means bits of metal frag was in the oil.. That isn't good but for the fact the pumps aren't working so it goes nowhere unless of course you can suggest fragments travelled before the pumps fail totally (after all they got to the chip detectors).
It might be possible that in the May ditching, the broken shaft could have fallen against the single chip detector in the sump and damaged it. As regards "bits of metal frag", when a weld breaks there arent any to speak of; perhaps minute particles which couldn't significantly damage other components.
Beyond that in the case of G-CHCN the HUMS data shows that the Red alarm threshold had been exceeded. So regardless of one pilot suggesting the vibration is insignificant it's significant enough to produce a red alarm.
The increased vibration thresholds to produce an amber or a red alarm are also minute, in order to give early warning of failure.
The 30 min emergency lube is of course a safety net - but not in all circumstances. Given EC225 MGB issues since 2009 you would be almost crazy to continue flying for 30 mins knowing you had a MGB issue when you could have quickly ditched in flat sea alongside a ship. When bits of gearbox fire themselves out of the casing or you loose the main rotor parts being lubricated is irrelevant.
Agreed completely. Calm sea and ship in sight which I've spoken to, or land half an hour away? It's a no-brainer.
It is also wrong to say it's flown for millions of hours on the same design until 18 months ago. Were that the case you would find the fix to be simple.
That's not exactly what was meant. There's no suggestion been made that the shaft design was changed 18 or more months ago.
The current lines of investigation by EC include any possible changes affecting the whole gearbox, which could affect the shaft adversely. One thought is that mods to the engine management system in the last 18 months or so, could have changed torque and vibration characteristics detrimentally for the pump drive bevel shaft.
Whoever stated that, presumably was taking a guess at the combined total hours of EC225 flying in the last approx 7years.
In May the engineering analysis of G-REDW show that the broken components triggered the chip detectors in the sump I believe - which means bits of metal frag was in the oil.. That isn't good but for the fact the pumps aren't working so it goes nowhere unless of course you can suggest fragments travelled before the pumps fail totally (after all they got to the chip detectors).
It might be possible that in the May ditching, the broken shaft could have fallen against the single chip detector in the sump and damaged it. As regards "bits of metal frag", when a weld breaks there arent any to speak of; perhaps minute particles which couldn't significantly damage other components.
Beyond that in the case of G-CHCN the HUMS data shows that the Red alarm threshold had been exceeded. So regardless of one pilot suggesting the vibration is insignificant it's significant enough to produce a red alarm.
The increased vibration thresholds to produce an amber or a red alarm are also minute, in order to give early warning of failure.
The 30 min emergency lube is of course a safety net - but not in all circumstances. Given EC225 MGB issues since 2009 you would be almost crazy to continue flying for 30 mins knowing you had a MGB issue when you could have quickly ditched in flat sea alongside a ship. When bits of gearbox fire themselves out of the casing or you loose the main rotor parts being lubricated is irrelevant.
Agreed completely. Calm sea and ship in sight which I've spoken to, or land half an hour away? It's a no-brainer.
It is also wrong to say it's flown for millions of hours on the same design until 18 months ago. Were that the case you would find the fix to be simple.
That's not exactly what was meant. There's no suggestion been made that the shaft design was changed 18 or more months ago.
The current lines of investigation by EC include any possible changes affecting the whole gearbox, which could affect the shaft adversely. One thought is that mods to the engine management system in the last 18 months or so, could have changed torque and vibration characteristics detrimentally for the pump drive bevel shaft.
Change of material spec, change of process it is all change of design to some degree - just depends how you use the word.
Any change untested is very silly and I think had I got my feet wet in G-REDW or G-CHC I'd be with my lawyer seeking damages as it's unforgivable to put onto service something untested.
As an aside since when did we start using total fleet hours as a benchmark for fitness for purpose?? 250k hours could just mean 1 million things lasting 15mins as much as 1 thing lasting 250k hours.. To exaggerate the point.
Any change untested is very silly and I think had I got my feet wet in G-REDW or G-CHC I'd be with my lawyer seeking damages as it's unforgivable to put onto service something untested.
As an aside since when did we start using total fleet hours as a benchmark for fitness for purpose?? 250k hours could just mean 1 million things lasting 15mins as much as 1 thing lasting 250k hours.. To exaggerate the point.
As an retired engineer I see 2 problems here, the main one being that the emerg lub system can't be tested on start up. The emerg lub system in the S61 took oil from a low point in the sump of the gear box, this low point was was part of a new sump that was part of the mod, I forget the amount of oil in it that could not be drawn on by the normal pump. The point is that it could be tested before flight. The 225 system can't as it uses glycol. To my mind the best fix (after fixing the shaft) would be to have a lub system that uses the same oil as the MGB so it can be tested.
The secondly the shaft hours might not be the same as the MGB. Some components, in the MGB, have longer ultimate hour than the MGB overhaul life. So the main shaft might be on it's second trip after O/H. I don't have a MM so I don't know the hours the shaft can do and though the MGB hours are said to be low nothing says the shaft is.
The secondly the shaft hours might not be the same as the MGB. Some components, in the MGB, have longer ultimate hour than the MGB overhaul life. So the main shaft might be on it's second trip after O/H. I don't have a MM so I don't know the hours the shaft can do and though the MGB hours are said to be low nothing says the shaft is.
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Pitts
Of course the fleet leader has not got 250k hours.....more like 10k hours! Its 250k fleet hours....
Pitts and Colibri
The 250k hours was quoted by EC in a customer briefing yesterday, their figures not mine. EC is not looking at the shaft or any changes between AS332L and EC225 from Carburised to Nitrided steel as being the primary cause of these failures.....there is something else happening, they think.
Of course the fleet leader has not got 250k hours.....more like 10k hours! Its 250k fleet hours....
Pitts and Colibri
The 250k hours was quoted by EC in a customer briefing yesterday, their figures not mine. EC is not looking at the shaft or any changes between AS332L and EC225 from Carburised to Nitrided steel as being the primary cause of these failures.....there is something else happening, they think.
Last edited by terminus mos; 17th Nov 2012 at 12:08.
Sevarg, people like to hark back to the S61 as if it were wonderful (and in truth it was not bad, in fact very good for its age!). On that old lady, the Emerg lube system as you say was an electric pump using oil from a low point in the sump. It is therefore similar in concept to the standby pump on the Super Puma family, the only difference being the method of pump drive. Of course with hindsight having 2 completely separate types of drive (mechanical and electric) seems a good thing. However neither of these systems meets the need for continued flight following complete loss of oil, the S61 would not be compliant with the current rules in this respect.
This is where the 225 Emerg lube comes in. Since you have to consider the worst location of the leak, it really has to be a total loss system. In order to keep the total fluid required down to a reasonable amount, EC decided to use it sprayed with a lot of air, hence the need for less than 12 litres to last over 30 mins and I suspect ordinary oil wouldn't atomise or do the same cooling trick as the glycol.
Otherwise, I quite agree with you that the system's downfall is the inability to excercise the valves and pump, or test the switches, prior to flight. The only trouble is that the more stuff you add to allow test, eg a means of pressuring the system without putting glycol into the gbx, the more complexity you add and therefore reduce the reliability. On the other hand, we are starting from a place of pretty low reliability!
All that said, the ability to fly 40 miles still air is not the be all and end all, I would rather not have it but have a MGB that didn't suffer from bits breaking off!
This is where the 225 Emerg lube comes in. Since you have to consider the worst location of the leak, it really has to be a total loss system. In order to keep the total fluid required down to a reasonable amount, EC decided to use it sprayed with a lot of air, hence the need for less than 12 litres to last over 30 mins and I suspect ordinary oil wouldn't atomise or do the same cooling trick as the glycol.
Otherwise, I quite agree with you that the system's downfall is the inability to excercise the valves and pump, or test the switches, prior to flight. The only trouble is that the more stuff you add to allow test, eg a means of pressuring the system without putting glycol into the gbx, the more complexity you add and therefore reduce the reliability. On the other hand, we are starting from a place of pretty low reliability!
All that said, the ability to fly 40 miles still air is not the be all and end all, I would rather not have it but have a MGB that didn't suffer from bits breaking off!
On the subject of 225 emlube, the problem seemed to be insuffient air pressure to activate the switch even with everything in-spec.
I just wonder if the group who designed the emlube system didn't talk to the MGB designers and so didn't realise that the crew would already have reduced to Vy and so didn't realise the engine would be running slowly hence low P2.4 air pressure.
An expeditious crew, faced with sudden double pump failure, would turn the IAS down to 80kts then the next action is to press the SHOT button to activate the emlube. 225 decel rate is 2kts/sec these days I think, so 150 to 80 is 35 secs plus a bit at each end, so after at the point where EMLUBE failure is being detected the engines are likely to be down around 20% total torque. I wonder if the EMLUBE failure is latched (once its on it stays on regardless) or momentary (would go out if pressure switches activate again.
Maybe the answer is to operate Training Idle switch #2 to get eng 1 working harder. I can just see that going into RFM section 3!
I just wonder if the group who designed the emlube system didn't talk to the MGB designers and so didn't realise that the crew would already have reduced to Vy and so didn't realise the engine would be running slowly hence low P2.4 air pressure.
An expeditious crew, faced with sudden double pump failure, would turn the IAS down to 80kts then the next action is to press the SHOT button to activate the emlube. 225 decel rate is 2kts/sec these days I think, so 150 to 80 is 35 secs plus a bit at each end, so after at the point where EMLUBE failure is being detected the engines are likely to be down around 20% total torque. I wonder if the EMLUBE failure is latched (once its on it stays on regardless) or momentary (would go out if pressure switches activate again.
Maybe the answer is to operate Training Idle switch #2 to get eng 1 working harder. I can just see that going into RFM section 3!