EC225
Pitts, are you sure you aren't a Daily Mail reporter in disguise?
Firstly, you say "...its very clear that there there is motivation to get the 225 flying..." - as if that is surprising or unreasonable. Surely the point of having a helicopter is to fly it. So try not to make it sound like a bad thing!
Secondly, on the subject of the MOD45 threshold, you are correct it has been significantly reduced. However, this relates to the point in a degradation process where the alert is triggered, not whether it is triggered or not. Once degradation starts, it is a continuous and worsening situation so it won't be the case that a MOD45 warning would be received by the new threshold and not by the old one, it will just happen sooner in the process.
If you are concerned that there may be spurious MOD45 warnings, that is a more reasonable position because I think that is certainly a possibility. EC have reprocessed a lot of HUMS data and we are assured that virtually no data would have exceeded the new thresholds. Virtually none, so in fact some would! However if you look at the consequences, the pilot has to reduce power a bit and land within 2 hours, not exactly a major crisis. An operational inconvenience, not a safety hazard.
Finally on the L2, had the HUMS data been properly regarded with the proper maintenance actions occuring, the accident would have been prevented. Adding a cockpit light would have been a "belt and braces" boost to flight safety by reducing the probability of a maintenance error leading to an accident, but its requrement is not really up to EC. Had EASA thought was merited, they would have mandated it but they did not. The L2 had of course managed to operate for the best part of 20 years without it anyway.
Firstly, you say "...its very clear that there there is motivation to get the 225 flying..." - as if that is surprising or unreasonable. Surely the point of having a helicopter is to fly it. So try not to make it sound like a bad thing!
Secondly, on the subject of the MOD45 threshold, you are correct it has been significantly reduced. However, this relates to the point in a degradation process where the alert is triggered, not whether it is triggered or not. Once degradation starts, it is a continuous and worsening situation so it won't be the case that a MOD45 warning would be received by the new threshold and not by the old one, it will just happen sooner in the process.
If you are concerned that there may be spurious MOD45 warnings, that is a more reasonable position because I think that is certainly a possibility. EC have reprocessed a lot of HUMS data and we are assured that virtually no data would have exceeded the new thresholds. Virtually none, so in fact some would! However if you look at the consequences, the pilot has to reduce power a bit and land within 2 hours, not exactly a major crisis. An operational inconvenience, not a safety hazard.
Finally on the L2, had the HUMS data been properly regarded with the proper maintenance actions occuring, the accident would have been prevented. Adding a cockpit light would have been a "belt and braces" boost to flight safety by reducing the probability of a maintenance error leading to an accident, but its requrement is not really up to EC. Had EASA thought was merited, they would have mandated it but they did not. The L2 had of course managed to operate for the best part of 20 years without it anyway.
Yes I take your point basically once it starts to trend upwards its not coming back and I guess the lower limit is more relevant when its being downloaded back at base as it needs to fly a long sector without further checks.
Join Date: Apr 2005
Location: Dubai
Posts: 348
Likes: 0
Received 0 Likes
on
0 Posts
HC, what's the next layer below 'Daily Mail'?
Sorry PE, you are now officially on my ignore list, I have not occasioned someone more prone to exceedances of nonsense. I might concede a point if the ET 787 had the same point of failure - i.e. the Li Battery, but since the scorch mark is safely above the rear galley on the pressurised side of the rear dome I am pretty confident that the failures do not have a common source expect perhaps some escaped electrons in the wrong place. The battery is in the pointy thing at the back next to what is called the 'APU'. To provide a link which says "Plane Catches Fire On Runway" from Sky News, when the aircraft was on a remote stand only amplifies your shaky grasp of the factual. On the same scale maybe you want to prolong the 225s loitering on the ground because the TR gearbox may leak it's lubricant and seize - it's all part of the same transmission - tell you what, lets make EC redesign the entire transmission prior to RTF.
Sorry PE, you are now officially on my ignore list, I have not occasioned someone more prone to exceedances of nonsense. I might concede a point if the ET 787 had the same point of failure - i.e. the Li Battery, but since the scorch mark is safely above the rear galley on the pressurised side of the rear dome I am pretty confident that the failures do not have a common source expect perhaps some escaped electrons in the wrong place. The battery is in the pointy thing at the back next to what is called the 'APU'. To provide a link which says "Plane Catches Fire On Runway" from Sky News, when the aircraft was on a remote stand only amplifies your shaky grasp of the factual. On the same scale maybe you want to prolong the 225s loitering on the ground because the TR gearbox may leak it's lubricant and seize - it's all part of the same transmission - tell you what, lets make EC redesign the entire transmission prior to RTF.
TOD you are the one drawing conclusions about whatever caused the 787 fire, my post was pretty minimal on the subject.
Whatever the cause of the fire as you can see making assumptions that you now have some Titanic of the air bites sooner or later.
If you do want to make a parallel to a fire on a 787 by another means then perhaps it might be that a MOD45 alarm is always related to the known vertical shaft issue......
Whatever the cause of the fire as you can see making assumptions that you now have some Titanic of the air bites sooner or later.
If you do want to make a parallel to a fire on a 787 by another means then perhaps it might be that a MOD45 alarm is always related to the known vertical shaft issue......
As a spectator and reading the reports -
The primary common denominator in the issue seems to be corrosion.
The crack propagated from the PTFE plug.
Fatigue life is not a factor so much when you look at the disparity between the fatigue cycles. 167 hours?
MOD 45 and MOD 70 trend happened within ~ 6 hours!
It would seem to me that the corrosion issue needs to be addressed first.
The change in material, higher power, 5 blades and subsequent change in cycle fatigue etc etc are the differences from a Super Puma which doesnt have a problem.
For me there is still a way to go to a conclusion to place the thing back in service.
The primary common denominator in the issue seems to be corrosion.
The crack propagated from the PTFE plug.
AAIB - During one of these tests a crack initiated and propagated from the 4.2 mm diameter hole after it had been deliberately corroded under laboratory conditions prior to the test.
MOD 45 and MOD 70 trend happened within ~ 6 hours!
It would seem to me that the corrosion issue needs to be addressed first.
The change in material, higher power, 5 blades and subsequent change in cycle fatigue etc etc are the differences from a Super Puma which doesnt have a problem.
For me there is still a way to go to a conclusion to place the thing back in service.
It would seem to me that the corrosion issue needs to be addressed first.
I find the hole and the plug to be the oddest aspects of this.
If it's OK to have a hole; and I am not sure that it is; then why plug it when this can result in crevice corrosion and the plug material is a quarter of the weight and therefore brings no benefit in rotational balance.
Then there is the question of "Hot spots". Are these related to the presence of the hole? One might expect them to be.
If there is moisture that can promote corrosion, and there is a hole, then surely the hole is a potential escape route for moisture (hone and polish?). The question that then arises is where would the moisture go after that. Is that the reason for the plug?
Not simple, whatever way you look at it.
If it's OK to have a hole; and I am not sure that it is; then why plug it when this can result in crevice corrosion and the plug material is a quarter of the weight and therefore brings no benefit in rotational balance.
Then there is the question of "Hot spots". Are these related to the presence of the hole? One might expect them to be.
If there is moisture that can promote corrosion, and there is a hole, then surely the hole is a potential escape route for moisture (hone and polish?). The question that then arises is where would the moisture go after that. Is that the reason for the plug?
Not simple, whatever way you look at it.
As we know, the hole is there to stress relief the end of the circumferential weld. As to the plug, good question but I think its just there to avoid excess oil escaping. The important point is to avoid containing any moisture. The inside of the shaft is ventilated elsewhere (oil for spline lubrication runs out at the bottom) and if the plug is a good fit, there is no cavity to trap moisture. That just leaves the moisture trapped in the sludge, which recurrent cleaning will eliminate.
Holes are normally used to stop the propagation of cracking. But in the Bond case, it was where the crack initiated, apparently caused by trapped moisture between the plug and the shamfer surface around the edge of the hole.
My problem is believing that the moisture had enough time to cause corrosion in the Bond gearbox after only 167 hours. Since the root causes seem to be twofold, corrosion AND residual stress, one wonders what proportion each root cause played in each shaft failure.
If EC explanations are to be believed, both failures have the same root cause(s) but originating in two separate areas of the shaft culminating in almost the same failure mode.
My problem is believing that the moisture had enough time to cause corrosion in the Bond gearbox after only 167 hours. Since the root causes seem to be twofold, corrosion AND residual stress, one wonders what proportion each root cause played in each shaft failure.
If EC explanations are to be believed, both failures have the same root cause(s) but originating in two separate areas of the shaft culminating in almost the same failure mode.
II - don't forget that it was 167 hrs flight time. We don't know how long it was sat on a shelf or in a heli under construction before that. Probably thousands of static hours. So lots of time for the corrosion to develop, just not very long for the consequential crack to develop!
Yes, two separate areas of the shaft and two different crack locations, but very close to each other so the net result was the same.
Yes, two separate areas of the shaft and two different crack locations, but very close to each other so the net result was the same.
don't forget that it was 167 hrs flight time
lets make EC redesign the entire transmission prior to RTF.
Join Date: Jul 2008
Location: Australia
Posts: 372
Likes: 0
Received 0 Likes
on
0 Posts
Type of cracking
Guys
I am only just looking at this thread, and I note the comments on cracks and corrosion. Be aware that there are essentially two types of cracks associated with corrosion. 1: fatigue initiated by the stress concentrations caused by corrosion pitting, and 2: stress corrosion cracking (SCC) caused by the combination of a corrosive environment, a residual stress and an alloy which is susceptible to stress-corrosion.
167 hours seems far too short for fatigue, even if corrosion was extant prior to service. I would be very suspicious of SCC and this is an alloy selection issue.
Regards
Blakmax
I am only just looking at this thread, and I note the comments on cracks and corrosion. Be aware that there are essentially two types of cracks associated with corrosion. 1: fatigue initiated by the stress concentrations caused by corrosion pitting, and 2: stress corrosion cracking (SCC) caused by the combination of a corrosive environment, a residual stress and an alloy which is susceptible to stress-corrosion.
167 hours seems far too short for fatigue, even if corrosion was extant prior to service. I would be very suspicious of SCC and this is an alloy selection issue.
Regards
Blakmax
Join Date: May 2012
Location: Aer
Posts: 431
Likes: 0
Received 0 Likes
on
0 Posts
It's the disparate flight hours (Bond = 167 CHC = 3800) and the fact that the Bond corrosion started from a hole and the CHC corrosion started from moisture trapped by sludge but both led to the same result that leaves me wondering. From day 1, these two failures have been treated as the same under the same investigation. I can't convince myself that approach was not conveniently expeditious.
On day one, they were, hence the time wasted looking for resonance issues etc. however it was eventually realised that the two events were not from the same cause, although from 2 very similar causes. The only thing I find surprising is how long it took to identify the corrosion from the wear sludge. You'd think you would extract the failed bits, wipe them clean and notice the corrosion, then check some other aircraft and find much less sludge and no corrosion, and voila!
We can all speculate all day (all year) on our pet theories (including conspiracy ones) but really we are all talking from positions of ignorance and personally I think its unlikely that AAIB, EASA and CAA would be acting as they are if the evidence wasn't convincing, and even EC must surely realise that they are in last chance saloon!
We can all speculate all day (all year) on our pet theories (including conspiracy ones) but really we are all talking from positions of ignorance and personally I think its unlikely that AAIB, EASA and CAA would be acting as they are if the evidence wasn't convincing, and even EC must surely realise that they are in last chance saloon!
Last edited by HeliComparator; 14th Jul 2013 at 13:37.
It took a while to figure out what was doing in Comets as I recall....and the 707 became the mainstay of jet passenger liners and the Comet became Nimrods or something like that.
Is that what is going on before our eyes today with the 225 and the 92?
Is that what is going on before our eyes today with the 225 and the 92?
Comet
No, I don't think so. The Comet killed lots, the 225 none. The comet had a fundamental airframe design issue, the 225 has a potential issue with 1 component ( I say "potential" because it only is an issue when a number of factors come together). Both the 92 and 225 had or have issues which make the passengers nervous. Ultimately when the dust has settled, the oil companies will remember they like the better range-payload of the 225 and even the passengers will like the "never bumped" aspect of the 225. Of course, the passengers will never like either the 92 or the 225 because by are both inherently uncomfortable and frightening, and take them out for 2 weeks of purgatory!
Join Date: Jun 2013
Location: Ogba
Age: 53
Posts: 137
Likes: 0
Received 0 Likes
on
0 Posts
HC,
Thanks for your knowledgeable and enlightening posts
. However, on those occasions when I've been SLF, I've loved the room and air conditioning, but hated the noise and air-stair door vibrations in the S92, and hated the claustrophobic cabin and lack of air conditioning in the EC225. I'm almost convinced that you're right, the EC225 is a better pilots' machine with an inherently safer and more modern design than the S92, but from a passenger perspective, the S92 wins (for now). I hope that eventually both will go on to be safe and successful, like the S61 and Super Puma eventually did in their day. The only real difference nowadays is instant opinions of others on the internet influencing the (mostly unreasoned) opinions and thinking of the herd 
Thanks for your knowledgeable and enlightening posts
. However, on those occasions when I've been SLF, I've loved the room and air conditioning, but hated the noise and air-stair door vibrations in the S92, and hated the claustrophobic cabin and lack of air conditioning in the EC225. I'm almost convinced that you're right, the EC225 is a better pilots' machine with an inherently safer and more modern design than the S92, but from a passenger perspective, the S92 wins (for now). I hope that eventually both will go on to be safe and successful, like the S61 and Super Puma eventually did in their day. The only real difference nowadays is instant opinions of others on the internet influencing the (mostly unreasoned) opinions and thinking of the herd