EC225
dessicant breather
rif-raff, as far as I know there isn't a dessicant breather on the Super Puma family gearboxes. You make a good point though, and it would seem a fairly straightforward way to improve the internal environment. There are of course strict rules about leaving the aircraft unused for any significant period in terms of need to protect the internals.
I suppose that with normal frequency of use, the gearbox internal surfaces are coated in oil and slight condensation doesn't actually get to the steel. However, as EC have now realised, when there is contamination from "wear dust" this can trap moisture and allow it intimate contact with the stressed surface.
I suppose that since this hadn't been a manifested problem for the last 30+ years of the Super Puma family, there was no motivation for EC to think about it, but perhaps they have now!
It is surprising how little thought sometimes goes into protection from the real world for systems designed by someone who never leaves an airconditioned office! For example, the FADECs (TM, not EC) not only live "outside" the airframe, but have a small hole in the casing so that an internal P0 backup sensor can measure static pressure. Obviously the internal circuit boards, connectors etc have some degree of protection, but when the helicopter goes flying up and down, inevitably air is exchanged in and out of the casing and with changes of temperature, some degree of condensation seems inevitable. Whilst I have to say that the FADECs have been very reliable in terms of never actually failing to govern, we have a fair turnover of them for minor faults, many of which turn out to be down to corrosion on the internal electronics.
If I were designing it, I would have the casing sealed and just mount the P0 sensor in a small ventilated cavity, or use a dessicator on the ventilation hole.
I suppose that with normal frequency of use, the gearbox internal surfaces are coated in oil and slight condensation doesn't actually get to the steel. However, as EC have now realised, when there is contamination from "wear dust" this can trap moisture and allow it intimate contact with the stressed surface.
I suppose that since this hadn't been a manifested problem for the last 30+ years of the Super Puma family, there was no motivation for EC to think about it, but perhaps they have now!
It is surprising how little thought sometimes goes into protection from the real world for systems designed by someone who never leaves an airconditioned office! For example, the FADECs (TM, not EC) not only live "outside" the airframe, but have a small hole in the casing so that an internal P0 backup sensor can measure static pressure. Obviously the internal circuit boards, connectors etc have some degree of protection, but when the helicopter goes flying up and down, inevitably air is exchanged in and out of the casing and with changes of temperature, some degree of condensation seems inevitable. Whilst I have to say that the FADECs have been very reliable in terms of never actually failing to govern, we have a fair turnover of them for minor faults, many of which turn out to be down to corrosion on the internal electronics.
If I were designing it, I would have the casing sealed and just mount the P0 sensor in a small ventilated cavity, or use a dessicator on the ventilation hole.
Last edited by HeliComparator; 11th Jul 2013 at 11:01.
HC.....can you tell us what the results of the latest EC and EU documents mean to Pilots and Engineers that have to fly and maintain the 225?
Did I read it right when I said it seemed to tell me every Eight Flight Hours the Shafts had to be given an Ultra-Sound Test?
What are the new Engineering procedures?
What restrictions are placed upon Pilots flying the 225?
Why is it....no one has stepped forward to explain to the "unknowing" what the new procedures are......too complicated for explanation?
Did I read it right when I said it seemed to tell me every Eight Flight Hours the Shafts had to be given an Ultra-Sound Test?
What are the new Engineering procedures?
What restrictions are placed upon Pilots flying the 225?
Why is it....no one has stepped forward to explain to the "unknowing" what the new procedures are......too complicated for explanation?
1. Reduced fatigue strength due to residual stress introduced during the shaft welding process
2. Reduced fatigue strength due to stress "hot spots" associated with the shaft geometry, in particular the surface roughness and the shaft shape
3. Very exceptional active corrosion in localised areas of the shaft.
2. Reduced fatigue strength due to stress "hot spots" associated with the shaft geometry, in particular the surface roughness and the shaft shape
3. Very exceptional active corrosion in localised areas of the shaft.
Blimey SAS, do you have trouble with reading? Oh- I forgot you are (were) a pilot and need to be spoon-fed!
No, in the AD para (2) (which includes the requirement for repetitive ultrasound) is terminated by para (4) when you complete para (3) (the MOD45 cockpit monitoring). AFAIK we won't be putting the a/c back into service until the MOD45 cockpit monitoring mod is done. This presumes the M'ARMS is servicable etc. Simples!
So not too complicated for explanation, too simple!
There are some changes to EOPs but no signicant normal operational changes.
For the L2, no need for ultrasound if you have the correct type of shaft.
Engineering-wise, need to change the oil jetting in the future, and clean the shaft of "wear dust" at 400 hr intervals.
No, in the AD para (2) (which includes the requirement for repetitive ultrasound) is terminated by para (4) when you complete para (3) (the MOD45 cockpit monitoring). AFAIK we won't be putting the a/c back into service until the MOD45 cockpit monitoring mod is done. This presumes the M'ARMS is servicable etc. Simples!
So not too complicated for explanation, too simple!
There are some changes to EOPs but no signicant normal operational changes.
For the L2, no need for ultrasound if you have the correct type of shaft.
Engineering-wise, need to change the oil jetting in the future, and clean the shaft of "wear dust" at 400 hr intervals.
Last edited by HeliComparator; 11th Jul 2013 at 12:30.
So....if Marms (sic) goes U/S....then what? Grounding condition or does all the other requirements kick in?
Its all in the AD! (paras 6 and 7). If M'ARMS goes U/S in theory you could still operate but you have to do the Ultrasonic inspection at rather frequent intervals (depending on your cruise power) if you want to operate offshore, but with the political sensitivity I doubt anyone will want to operate them thus. We will fix them instead! Fortunately the M'ARMS seems fairly reliable as a whole, failures seems to relate to the occasional issue with individual accelerometers / connectors
Last edited by HeliComparator; 11th Jul 2013 at 12:53.
One last question......upon installation of the "new" and "improved" shafts.....all the monitoring systems requirements go away?
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I think you might be wrong HC. I understand that Ultrasound is required after 8 or 11.5 hours (can't remember exactly) Its the combination of ultrasound and the Mod45 increased monitoring which when combined, gives the probability low enough for the CAA to lift the restrictions.
Since in their briefings to oil and gas industry, EC has admitted that the stresses on the shaft were found to be greater than those calculated during certification, we have less confidence than others in the interim solution. My company has decided not to accept the "fudge" approach. We will wait for the new shafts next year before we're introduce the 225.
It will give our passengers time to see the aircraft in service before we ask them to get back into it which they don't want to do.
Since in their briefings to oil and gas industry, EC has admitted that the stresses on the shaft were found to be greater than those calculated during certification, we have less confidence than others in the interim solution. My company has decided not to accept the "fudge" approach. We will wait for the new shafts next year before we're introduce the 225.
It will give our passengers time to see the aircraft in service before we ask them to get back into it which they don't want to do.
Last edited by terminus mos; 11th Jul 2013 at 13:19.
terminus - I am only going by what the AD says. It seems unlikely that with all teh discussion that have been going on between CAA and EASA, that a new AD would be published that doesn't satisfy the CAA. Where have you seen the information that makes you say what you do?
Perhaps the confusion is the difference between "increased MOD 45 monitoring" - by means of analysing the groundstation data at 3 hr intervals or whatever. This still require the ultrasound inspections.
Versus
The MOD45 cockpit monitoring. Once this is in place, the requirement for the ultrasound, which is contained in para 2 of the AD as I said, is removed. The relevant sentence in the AD para 4 is:
of this AD.
my bold
SAS, yes that is the intention, but that aspect is not yet covered in the AD. I guess they can't mention it in the AD until its certified.
Perhaps the confusion is the difference between "increased MOD 45 monitoring" - by means of analysing the groundstation data at 3 hr intervals or whatever. This still require the ultrasound inspections.
Versus
The MOD45 cockpit monitoring. Once this is in place, the requirement for the ultrasound, which is contained in para 2 of the AD as I said, is removed. The relevant sentence in the AD para 4 is:
(4) Modification of an EC 225 helicopter as required by paragraph (3) of this
AD constitutes terminating action for all the requirements of paragraph (2)
AD constitutes terminating action for all the requirements of paragraph (2)
of this AD.
my bold
SAS, yes that is the intention, but that aspect is not yet covered in the AD. I guess they can't mention it in the AD until its certified.
Last edited by HeliComparator; 11th Jul 2013 at 13:24.
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HC on re reading it, I agree with what you say. Why then is your company looking for battalions of NDT ultrasound testers to have one at each base?
Pitts, yes HC will be able to confirm that a failed sensor could give a false reading but there is a procedure for flying at certain parameters to check and see if the MARMS can re acquire the data.
Pitts, yes HC will be able to confirm that a failed sensor could give a false reading but there is a procedure for flying at certain parameters to check and see if the MARMS can re acquire the data.
Last edited by terminus mos; 11th Jul 2013 at 13:48.
terminus, if that is so then not sure (just a lowly pilot, me) but perhaps its either a hang up from before the AD was actually published when there was lots of rumour and speculation, or perhaps we have decided to gold plate the AD to keep the punters happy?
I am not necessarily saying you are wrong in saying that the CAA are putting more stringent requirements on it than the AD, but would like to see where that is published.
I am not necessarily saying you are wrong in saying that the CAA are putting more stringent requirements on it than the AD, but would like to see where that is published.
Pitts - yes, MOD45 was not invented to monitor the shaft for cracking. If I am honest I can't remember which one it is but there is MOD70 and MOD45, and one is the bevel gear, one is the oil pump drive gears. I think MOD45 is the bevel gear, so a degredation of the bevel gear teeth and/or bearings could trigger a MOD45 alarm. Whatever the cause in that area, I think you would want to follow the new EOP and find somewhere to land!
terminus, just been checking the rumour machine. It seems we may have decided to do the repetitive ultrasound anyway, even though its not required, to demonstrate that we are doing everying possible to maximise safety. Not sure though.
That would be a very wise move....despite the extra cost and redundancy.
As I recall there was a Poster that suggested BHL was caving to Commercial pressure and cutting corners.....which plainly is not the case it would appear....far from it in fact.
The thrust of that complaint had to do with some vacancies in Management positions that Poster felt very crucial to the Safety Operation.
Those concerns did not seem to hold water when made....and seem to be even less accurate in light of what HC is suggesting.
As I recall there was a Poster that suggested BHL was caving to Commercial pressure and cutting corners.....which plainly is not the case it would appear....far from it in fact.
The thrust of that complaint had to do with some vacancies in Management positions that Poster felt very crucial to the Safety Operation.
Those concerns did not seem to hold water when made....and seem to be even less accurate in light of what HC is suggesting.
If you take the wording of SIN 2600-S-00 there are several times when a two hour flight time is related to a MOD45 alarm. It suggests “the crew will therefore be informed of the propagation of any cracks, and will have 2 hours to proceed with a normal landing…”
It then goes on to say that “The flight manual requires the helicopter to land as soon as possible, without exceeding 2 hours”.
We also know the thresholds vary from aircraft to aircraft – hence the need for a learned threshold and an absolute limit.
If the MOD45 alarm could – for whatever reason –signal a failure that is beyond that already understood by recent events and since the grounding operators have managed to continue to provide service and a “proper” fix is due in 1 year. It therefore seems a huge gamble with the Eurocopter brand, for operators, crew and passengers to push on, MOD45 alarming for 2 hours??
Whilst it is very clear EC understand events in order to continue to flying they are making a huge assumption with the MOD45 alarm – especially since all the other measures would suggest if an EC225 has a MOD45 alarm now its likely NOT to be linked to current issues.
Oddly its even less clear where this pressure is coming from because if you take Bristow at their word they don’t see flights resuming even in the interim state until the end of the year.
It then goes on to say that “The flight manual requires the helicopter to land as soon as possible, without exceeding 2 hours”.
We also know the thresholds vary from aircraft to aircraft – hence the need for a learned threshold and an absolute limit.
If the MOD45 alarm could – for whatever reason –signal a failure that is beyond that already understood by recent events and since the grounding operators have managed to continue to provide service and a “proper” fix is due in 1 year. It therefore seems a huge gamble with the Eurocopter brand, for operators, crew and passengers to push on, MOD45 alarming for 2 hours??
Whilst it is very clear EC understand events in order to continue to flying they are making a huge assumption with the MOD45 alarm – especially since all the other measures would suggest if an EC225 has a MOD45 alarm now its likely NOT to be linked to current issues.
Oddly its even less clear where this pressure is coming from because if you take Bristow at their word they don’t see flights resuming even in the interim state until the end of the year.
Last edited by Pittsextra; 11th Jul 2013 at 15:31.
Pitts, set against Bristow's 100,000 hr trouble-free flight time in the EC225, and the detailed investigations culminating in the cleaning and checking for corrosion of the affected areas, and the cockpit MOD45 alarm, just how likely do you think we are to encounter another shaft failure resulting in ditching?
So a) it aint going to happen and b) if it did, why do you think there is another failure mode that has never manifested itself in the history of the fleet? Doom-mongering perhaps?
Prior to MOD45 cockpit warning, if there had been another failure mode affecting this parameter, it would only be known about on return to base, just like all the other M'ARMS parameters.
So yes, maybe the aircraft will blow into tiny smithereens with blood sprayed all over the airport when it first lifts into the hover, but its more likely that the crew will be beamed out of the cockpit by aliens to be experimented on in orbit whilst the helicopter carries on until it runs out of fuel.
By the way, regardless of what the SIN says, the SB and Flight Manual Supplement for the MOD45 cockpit monitoring says, in the even of a MOD45 exceed, "Limit duration of flight, maximum flight time in MOD45 exceed 2 hours" and fly at 65% torque.
Which is not the same as "land as soon as possible" since the latter puts you on a helideck somewhere in the N Sea - and then what do you do - whereas the former allows you to return to a land airport, hopefully a base with engineering support.
So a) it aint going to happen and b) if it did, why do you think there is another failure mode that has never manifested itself in the history of the fleet? Doom-mongering perhaps?
Prior to MOD45 cockpit warning, if there had been another failure mode affecting this parameter, it would only be known about on return to base, just like all the other M'ARMS parameters.
So yes, maybe the aircraft will blow into tiny smithereens with blood sprayed all over the airport when it first lifts into the hover, but its more likely that the crew will be beamed out of the cockpit by aliens to be experimented on in orbit whilst the helicopter carries on until it runs out of fuel.
By the way, regardless of what the SIN says, the SB and Flight Manual Supplement for the MOD45 cockpit monitoring says, in the even of a MOD45 exceed, "Limit duration of flight, maximum flight time in MOD45 exceed 2 hours" and fly at 65% torque.
Which is not the same as "land as soon as possible" since the latter puts you on a helideck somewhere in the N Sea - and then what do you do - whereas the former allows you to return to a land airport, hopefully a base with engineering support.
Last edited by HeliComparator; 11th Jul 2013 at 15:41.
HC.....you must really like it way out there on the end of that tree limb!
I would think you would have learned to temper your comments just a wee bit and leave yourself some wiggle room should the disproof to your statement ever happens.
Are the Odds with you on this....absolutely......but then were they not before the two Ditchings as well?
Helicopters have ways of pulling our pants down in public.....always did....always will!
I would think you would have learned to temper your comments just a wee bit and leave yourself some wiggle room should the disproof to your statement ever happens.
Are the Odds with you on this....absolutely......but then were they not before the two Ditchings as well?
Helicopters have ways of pulling our pants down in public.....always did....always will!
Hang on stop. I'm not doom mongering I just asked a question and gave what I think is a fairly logical view?
First of all lets stop with all the 100000hr, 300000hr Super Puma flight hour stats. As we can see from the 2 accidents you had one go in after 160ish hours the other after almost 4000 and both well before the life of the shaft.
Add to the fact even an interim fix is 9 months in the making and a final fix another year away this is clearly not a trivial matter.
However like I said EC have thrown the kitchen sink at it and like you said with all the other measures it is unlikely to happen so why therefore make the assumption with the MOD45 alarm?
I'm not trying to be sensationalist I'm just asking the question why and how can you make that assumption??
First of all lets stop with all the 100000hr, 300000hr Super Puma flight hour stats. As we can see from the 2 accidents you had one go in after 160ish hours the other after almost 4000 and both well before the life of the shaft.
Add to the fact even an interim fix is 9 months in the making and a final fix another year away this is clearly not a trivial matter.
However like I said EC have thrown the kitchen sink at it and like you said with all the other measures it is unlikely to happen so why therefore make the assumption with the MOD45 alarm?
I'm not trying to be sensationalist I'm just asking the question why and how can you make that assumption??
SAS - yeah, but I don't care any more!
Pitts, I think I have explained why it doesn't matter what the cause of the MOD45 alarm is.
Pitts, I think I have explained why it doesn't matter what the cause of the MOD45 alarm is.
Last edited by HeliComparator; 11th Jul 2013 at 15:42.