North Sea heli ditching: Oct 2012
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Colibri49
I don't like the "cut of your jib" Sir. As so often in life, it isn't necessarily so much what is being stated, but how it is presented. Try making your submissions in non-confrontational tones such as used by riff-raff, if you want to be more welcome.
Well said Sir, indeed!
Pitts, you PMd me and I have replied, but to save time I think I will paste my response to your PM below, since it covers some points you raised in your post:
I think you pehaps have a slightly false impression about what HUMS is all about. Firstly, it is not a primary means of assuring airworthiness. You can buy an EC225 that meets all the CS29 certification requirements, that doesn't have HUMS. HUMS is added as an extra layer of safety above and beyond that required for certification.
Secondly HUMS is by no means an exact black and white science, so since this shaft failure was the first time such a failure happened, it is not too surprising that HUMS thresholds etc are revised in light of "real" failure data.
On the point about the time to failure and the relevance of amber thresholds, what you say is correct for this particular component and failure mode. However there are plenty of other things that have a much slower failure progression rate where HUMS gives many 10s of hours warning.
Part of the reason for amber warnings is that false alarms continue to be an issue with any HUMS system. The sensors are all mounted externally to the transmission in the fairly "unfriendly" environment of heat, dirt, oil and airframe vibration. A common failure mode is that the sensor, or its connector or cabling, are not well attached (ie coming a bit loose) and so the amber threshold allows an attempt to rectify the alert by fixing the sensors, before having to take more serious action such as replacing the main gearbox. It is more appropriate for some parameters than others, for example the enhanced impulsiveness indicators (what used be called M6*) are better correlated to shaft rotation speed, so noise from a loose connection at airframe vibration frequency will have less effect than on say a bearing health indicator which just tends to work on rms and peak vibration level over a relatively wide frequency range, not correlated to the shaft rotation. There are something over 100 different parameters in a HUMS system.
So when you say the manufacturer could do better, I am sure that is true but EC is no worse in this area than any other manufacturer.
In summary, if HUMS was a tool for primary airworthiness I might be worried, but since it is just an optional extra layer over and above the basic certification, I am not worried. I flew helicopters for 10+ years before HUMS was ever invented!
I think you pehaps have a slightly false impression about what HUMS is all about. Firstly, it is not a primary means of assuring airworthiness. You can buy an EC225 that meets all the CS29 certification requirements, that doesn't have HUMS. HUMS is added as an extra layer of safety above and beyond that required for certification.
Secondly HUMS is by no means an exact black and white science, so since this shaft failure was the first time such a failure happened, it is not too surprising that HUMS thresholds etc are revised in light of "real" failure data.
On the point about the time to failure and the relevance of amber thresholds, what you say is correct for this particular component and failure mode. However there are plenty of other things that have a much slower failure progression rate where HUMS gives many 10s of hours warning.
Part of the reason for amber warnings is that false alarms continue to be an issue with any HUMS system. The sensors are all mounted externally to the transmission in the fairly "unfriendly" environment of heat, dirt, oil and airframe vibration. A common failure mode is that the sensor, or its connector or cabling, are not well attached (ie coming a bit loose) and so the amber threshold allows an attempt to rectify the alert by fixing the sensors, before having to take more serious action such as replacing the main gearbox. It is more appropriate for some parameters than others, for example the enhanced impulsiveness indicators (what used be called M6*) are better correlated to shaft rotation speed, so noise from a loose connection at airframe vibration frequency will have less effect than on say a bearing health indicator which just tends to work on rms and peak vibration level over a relatively wide frequency range, not correlated to the shaft rotation. There are something over 100 different parameters in a HUMS system.
So when you say the manufacturer could do better, I am sure that is true but EC is no worse in this area than any other manufacturer.
In summary, if HUMS was a tool for primary airworthiness I might be worried, but since it is just an optional extra layer over and above the basic certification, I am not worried. I flew helicopters for 10+ years before HUMS was ever invented!
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Just for info
Those pilots who were operating out of ABZ how often and during which months did you notice the reduction in NR as a result of the -6000ft 14hz mod?
What’s the typical start up to lift off time at ABZ?
On approach/departure from/ to a rig how much time is spent below 60 Kts.
Those pilots who were operating out of ABZ how often and during which months did you notice the reduction in NR as a result of the -6000ft 14hz mod?
What’s the typical start up to lift off time at ABZ?
On approach/departure from/ to a rig how much time is spent below 60 Kts.
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PITTS My reference to our livelihoods does not mean that any of us would fail to speak up to protect our incomes. This is about making sure we are safe and therefore our passengers are safe. No more, no less.
It upsets us when people like you, with limited understanding and knowledge, critise the system/process/manufacturer/us and in doing so create a poor impression of the system/process/manufacturer/us to our customers/passengers.
I am not sure why you feel so motivated to be interested in such detail.
It upsets us when people like you, with limited understanding and knowledge, critise the system/process/manufacturer/us and in doing so create a poor impression of the system/process/manufacturer/us to our customers/passengers.
I am not sure why you feel so motivated to be interested in such detail.
DB - I've got no interest in the back and forth fighting, after all i know nothing, although that might come back and bite in a few months from now.
You asked before why I was interested and I was told by someone else not to explain it. Rock and a hard place.
HC - thanks for the HUMS summary - I appreciate the failure was new and so absolute values for a failure might now be available for all sensors - although I wondered how the learned thresholds are devised given the spread between REDW and CNCN. Then how that fed into the decision making vis download times, thresholds in the period May to October.
You asked before why I was interested and I was told by someone else not to explain it. Rock and a hard place.
HC - thanks for the HUMS summary - I appreciate the failure was new and so absolute values for a failure might now be available for all sensors - although I wondered how the learned thresholds are devised given the spread between REDW and CNCN. Then how that fed into the decision making vis download times, thresholds in the period May to October.
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MARMS was once described as the greatest advancement in helicopter safety since the introduction of the second engine. And I believe that it is. However it is still relatively in its infancy. Learned thresholds are required to compensate for the fact that all components are not created equal. Minor variations during manufacture may result in difference of vibration exhibited by the component. This is taken into account during the learning process, ie whats unusual for this particular assembly.
It’s unfortunate in the current scenario that MARM can only detect a crack that is in its final stages before failure. It won’t detect the start of a crack.
It’s unfortunate in the current scenario that MARM can only detect a crack that is in its final stages before failure. It won’t detect the start of a crack.
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DB - I've got no interest in the back and forth fighting, after all i know nothing, although that might come back and bite in a few months from now.
See PITTS, there you go again!!!???
See PITTS, there you go again!!!???
Last edited by DOUBLE BOGEY; 6th Dec 2012 at 17:00.
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"MARMS was once described as the greatest advancement in helicopter safety since the introduction of the second engine"
OOOH Pablo - you are probably going to get all the SEH freaks squeaking about that second engine, especially SAS who probably flew in "Nam" with no engines at all, in a snowstorm, in the dead man's curve and never died once!!
DB
OOOH Pablo - you are probably going to get all the SEH freaks squeaking about that second engine, especially SAS who probably flew in "Nam" with no engines at all, in a snowstorm, in the dead man's curve and never died once!!
DB
Last edited by DOUBLE BOGEY; 6th Dec 2012 at 15:40.
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While I appreciate adding a second engine adds to the probability of having an engine failure by 50%. What’s your experience of operating the 225when it’s a bit cold.
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Wasn't quite sure 100% on the 50% bit but 100% may be laying it on a bit thick. Thread now diverges to accommodate statisticians. Any info out there on the NR info?
Edit this response was to a post that has disappeared?
Edit this response was to a post that has disappeared?
Last edited by Pablo332; 6th Dec 2012 at 17:08.
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Those pilots who were operating out of ABZ how often and during which months did you notice the reduction in NR as a result of the -6000ft 14hz mod?
What’s the typical start up to lift off time at ABZ?
On approach/departure from/ to a rig how much time is spent below 60 Kts.
Pitts, I concur with Colibri, it isn't WHAT your asking its how you are asking. You have slated people and companies, do you honestly expect no reaction?
Si
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During what months did you come close?
Feel free to go onto the met office website and look at the temperatures and pressures for the past year, then compare that to the NR laws for the EC225 then you will know when/if it went below 100%.
Si
Last edited by bigglesbutler; 6th Dec 2012 at 17:59.
We used to do all our OEI training in the aircraft, between 2005 and 2008. By the end of 2008 the Helisim 225 sim became available and each pilot made 1 visit per year, the other 6 monthly check including OEI was done in the aircraft. In the last couple of years nearly all training been done in the Sim. Only Sim To Aircraft adaptation for new pilots is done in the aircraft.
So the amount of OEI training decreased a lot over the past 2 years, compared to before.
On the subject of Nr / density altitude, the Nr is rarely below 100% with the APM engaged. Of course, after start and until APM is engaged, it can be down to as low as 98%. Offshore is usually warmer than onshore in the type of weather conditions giving very low density altitude, so I doubt the Nr is ever less than 100% offshore. With the latest software, Nr is more often up at 103.8% compared to the previous version, but versions before that were more like the current one, so it is difficult to see that as the issue. Only Nr <100% is new.
So the amount of OEI training decreased a lot over the past 2 years, compared to before.
On the subject of Nr / density altitude, the Nr is rarely below 100% with the APM engaged. Of course, after start and until APM is engaged, it can be down to as low as 98%. Offshore is usually warmer than onshore in the type of weather conditions giving very low density altitude, so I doubt the Nr is ever less than 100% offshore. With the latest software, Nr is more often up at 103.8% compared to the previous version, but versions before that were more like the current one, so it is difficult to see that as the issue. Only Nr <100% is new.
Last edited by HeliComparator; 6th Dec 2012 at 18:44.
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Heli Comparator
Thank you for the information. From what you say would it be fair to assume that most 225s on the north sea seldom have a reduction in NR due to density altitude issues?
Thank you for the information. From what you say would it be fair to assume that most 225s on the north sea seldom have a reduction in NR due to density altitude issues?
DB.....actually 99.9999 percent of my Vietnam flying was with two engines....there were some occasions it was with one....and yes there was one occasion where it was with none.
No snow and ice in Vietnam but well yes....there were lots of hours spent in the "Dead Man's Curve".....and I did think I had died several times but fortunately had not despite some golden opportunities.
For Snow and Ice....I did the Arctic....for the Dead Man's Curve I did lots of forestry and construction work.
So what is your point besides talking like a Prick?
No snow and ice in Vietnam but well yes....there were lots of hours spent in the "Dead Man's Curve".....and I did think I had died several times but fortunately had not despite some golden opportunities.
For Snow and Ice....I did the Arctic....for the Dead Man's Curve I did lots of forestry and construction work.
So what is your point besides talking like a Prick?
No, that's not quite what I said. I meant that Nr is rarely below 100%. It is more routinely below the nominal 103.8% at low airspeed. For example at the moment the density altitude is about -1100' which gives an Nr slightly reduced to 103%. But the pressure is quite low at the moment. With a high pressure winter scenario, say 1030 HPa which is not unusual in mid-winter, temperatures below 9degC results in Nr below 103.8% in hover / on ground. With 1030 HPa and -4 degC, Nr would be starting to go below 100% but because Aberdeen is near the sea, it doesn't often get that cold.
Pitts, I concur with Colibri, it isn't WHAT your asking its how you are asking. You have slated people and companies, do you honestly expect no reaction?
2 helicopters have ended in the North sea and a lot of people have been affected as a result, and currently neither the CAA or EASA agree on how safe this type is. Do YOU honestly expect no reaction?