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Hello, I am currently studying engineering at college and do not have any helicopter experiance. I have been set a question about Helicopter Health and Usage Monitoring Systems (HUMS). Which is:-
Q) The Helicopter Usage Monitoring System (HUMS) provides :-
a) Early warning of potential failure of components
b) Maintenance planning with a continuous update on component operating times
c) Vibration monitoring and analysis data
I have done a bit of internet research on this subject particularly read 'What is HUMS, and what are its benefits' which I found at the CAA web site http://www.caa.co.uk/docs/389/srg_ac...-01-300103.pdf
I was hoping I could get the views from people who have interaction with such a system as it appears to be from the question set that more than one answer could be correct. I look forward to your view, Thankyou Ben
Q) The Helicopter Usage Monitoring System (HUMS) provides :-
a) Early warning of potential failure of components
b) Maintenance planning with a continuous update on component operating times
c) Vibration monitoring and analysis data
I have done a bit of internet research on this subject particularly read 'What is HUMS, and what are its benefits' which I found at the CAA web site http://www.caa.co.uk/docs/389/srg_ac...-01-300103.pdf
I was hoping I could get the views from people who have interaction with such a system as it appears to be from the question set that more than one answer could be correct. I look forward to your view, Thankyou Ben
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Ben,
HUMS is a subject of much debate. On the whole I'm of the opinion that we need it in the helicopter world, and that it does go some way to achieving the tasks you mention.
It is not however perfect. Sometimes failures occur which, or one reason or another were either not detected by HUMS or the human factor kicks in, and warnings are not spotted. It can also generate false alerts, meaning a fault is indicated, but in reality it is the sensor or instrumentation which is at fault.
As I said its far from perfect, but its a whole lot better than your first indication of a problem being the North Sea gushing in your cabin window
E-mail me if you want some detailed info.
HUMS is a subject of much debate. On the whole I'm of the opinion that we need it in the helicopter world, and that it does go some way to achieving the tasks you mention.
It is not however perfect. Sometimes failures occur which, or one reason or another were either not detected by HUMS or the human factor kicks in, and warnings are not spotted. It can also generate false alerts, meaning a fault is indicated, but in reality it is the sensor or instrumentation which is at fault.
As I said its far from perfect, but its a whole lot better than your first indication of a problem being the North Sea gushing in your cabin window
E-mail me if you want some detailed info.
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HUMS normally stands for Health and Usage Monitoring System. However the question calls it Helicopter Usage Monitoring System - ie no Health.
Perhaps this is a mistake on the part of the question-setter, but on the other hand, looking at the 3 answers, 2 of them relate to the "Health" aspect and one relates to the "Usage" aspect of HUMS - so perhaps the Health is deliberately left out and the correct answer is b.
In other words, if the question is meant as it is exactly written, b is the answer. However it does seem a silly question to ask because everyone in the civil industry will tell you that it is answers a and c - and "Health" that is the main reason and benefit of having HUMS fitted. I seem to recall that is was the military that were pushing for the Usage aspect to be designed into HUMS - presumably because their existing methods of tracking component lives were inadequate at the time. Perhaps the questioner has a military background?
If the question had read "The Health & Usage Monitoring System (HUMS) provides " then the correct answer would certainly have been a - or at least that is the main justification for having HUMS in the eyes of civilian operators and the CAA.
Perhaps this is a mistake on the part of the question-setter, but on the other hand, looking at the 3 answers, 2 of them relate to the "Health" aspect and one relates to the "Usage" aspect of HUMS - so perhaps the Health is deliberately left out and the correct answer is b.
In other words, if the question is meant as it is exactly written, b is the answer. However it does seem a silly question to ask because everyone in the civil industry will tell you that it is answers a and c - and "Health" that is the main reason and benefit of having HUMS fitted. I seem to recall that is was the military that were pushing for the Usage aspect to be designed into HUMS - presumably because their existing methods of tracking component lives were inadequate at the time. Perhaps the questioner has a military background?
If the question had read "The Health & Usage Monitoring System (HUMS) provides " then the correct answer would certainly have been a - or at least that is the main justification for having HUMS in the eyes of civilian operators and the CAA.
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As currently conceived and implimented, a pure HUMS answers to your question as b and c, but certainly not a. there are systems that can help predict failure, but they need high software qualification standards, much input trending data, and lots of experience in the specific type of helo before they could be trusted. to my knowledge, and notwithstanding the assertions of some who have posted on pprune in the past, no current HUMS comes close to a reliable predictive capability.
None of this is to assert that such capabilities are not possible (they surely are). We must strive to make that predictive capability a reality.
None of this is to assert that such capabilities are not possible (they surely are). We must strive to make that predictive capability a reality.
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Nick,
You are correct in what you are saying, but as you well know, HUMS will detect IN SOME CIRCUMSTANCES a defect, which if left unattended will propagate into a failure, I assume the S-92 bearing monitor was designed with this very thought in mind??
As I said earlier, HUMS is certainly not failsafe, and will never be so until we develop intelligent monitoring, and even that will never be perfect, we just strive to produce the best and safest systems we can. I'm sure you guys over there follow the same philosophy.
"Early failure detection" is an old RAF phrase, which perhaps would have been better termed "Defect detection", but nevertheless, it does work to some degree.
On the subject of usage EuroChopper that was indeed a thing the military insisted upon, due to poor tracking of component lifing. The Navy in particular were disgraceful at tracking the usage and whereabouts of major assemblies, and sub assemblies.
In short badly worded question for you Ben
You are correct in what you are saying, but as you well know, HUMS will detect IN SOME CIRCUMSTANCES a defect, which if left unattended will propagate into a failure, I assume the S-92 bearing monitor was designed with this very thought in mind??
As I said earlier, HUMS is certainly not failsafe, and will never be so until we develop intelligent monitoring, and even that will never be perfect, we just strive to produce the best and safest systems we can. I'm sure you guys over there follow the same philosophy.
"Early failure detection" is an old RAF phrase, which perhaps would have been better termed "Defect detection", but nevertheless, it does work to some degree.
On the subject of usage EuroChopper that was indeed a thing the military insisted upon, due to poor tracking of component lifing. The Navy in particular were disgraceful at tracking the usage and whereabouts of major assemblies, and sub assemblies.
In short badly worded question for you Ben
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Flytest,
When we want to measure the aircraft to be sure it is airworthy, especially in flight, we don't use the HUMS. We use a level A software Bearing Monitor Unit, which has the redundancy, integrity and internal logic to be trusted with this critical info. A normal HUMS, like the kind mandated by the CAA, is not of the integrity to generate a pilot inflight warning, after all, that warning, if false, could actually cause a worse incident by alarming the crew to do something rash, like ditch.
We have gone round on this before. The typical HUMS is not of a level of airworthiness that allows us to trust it with real time warnings, it is useful as a keeper of times and conditions, a general guide for establishing trends, and a way to require post flight preventative maintenance to be performed.
When we want to measure the aircraft to be sure it is airworthy, especially in flight, we don't use the HUMS. We use a level A software Bearing Monitor Unit, which has the redundancy, integrity and internal logic to be trusted with this critical info. A normal HUMS, like the kind mandated by the CAA, is not of the integrity to generate a pilot inflight warning, after all, that warning, if false, could actually cause a worse incident by alarming the crew to do something rash, like ditch.
We have gone round on this before. The typical HUMS is not of a level of airworthiness that allows us to trust it with real time warnings, it is useful as a keeper of times and conditions, a general guide for establishing trends, and a way to require post flight preventative maintenance to be performed.
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We've had HUMS fitted for some time now. All in all, false warnings have been reduced to a very low level, and real alerts are now few and far between. We do get some problems with the fiddly connectors but all-in-all, I think that it is doing its job.
I agree that in-flight warnings are not a good idea using this system, in fact, they were originally designed-in for high eng vibes, but inhibited shortly afterwards.
The system does allow a complex series of measurements to be carried out during flight, and analysis carried out on the ground. As the system gets older the alert thresholds are 'polished up' and you end up with a system with years of experience available as an off the shelf product, with each aircraft fitted with the same level of monitoring.
Some of my workmates have not had training on this system (which is a shame) as they would find that it is a great diagnostic tool which supplements existing maintenance practices. I've heard that training is mandatory in the UK. The days of rotor track and balance (RTB) defects taking multiple test flights are over, with one or two shot adjustments giving engineers more crew room time. RTB adjustments are allowed without airtests in many cases.
The addition of the HOMP (Helicopter Operational Monitoring Programme) using CQAR data has been found to give engineers alerts to dormant defects automatically. I guess it tightens up pilot flying practices as well.
I was a dubious user of the system in the early days, but as you can see, now I've seen the light. If I was a helicopter pilot, I would be wondering why I've not got it fitted on my aircraft. If I was a fleet manager, I would be doing some serious sums as I'm sure that HUMS saves maintenance time and, of course, money.
I agree that in-flight warnings are not a good idea using this system, in fact, they were originally designed-in for high eng vibes, but inhibited shortly afterwards.
The system does allow a complex series of measurements to be carried out during flight, and analysis carried out on the ground. As the system gets older the alert thresholds are 'polished up' and you end up with a system with years of experience available as an off the shelf product, with each aircraft fitted with the same level of monitoring.
Some of my workmates have not had training on this system (which is a shame) as they would find that it is a great diagnostic tool which supplements existing maintenance practices. I've heard that training is mandatory in the UK. The days of rotor track and balance (RTB) defects taking multiple test flights are over, with one or two shot adjustments giving engineers more crew room time. RTB adjustments are allowed without airtests in many cases.
The addition of the HOMP (Helicopter Operational Monitoring Programme) using CQAR data has been found to give engineers alerts to dormant defects automatically. I guess it tightens up pilot flying practices as well.
I was a dubious user of the system in the early days, but as you can see, now I've seen the light. If I was a helicopter pilot, I would be wondering why I've not got it fitted on my aircraft. If I was a fleet manager, I would be doing some serious sums as I'm sure that HUMS saves maintenance time and, of course, money.
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Nick
I never have been a supporter of cockpit displays for HUMS, for the very reason you mention, however your example is a little strong, if I was flying along with all my T's & P's ok, then there is no way on the planet I would take rash actions like ditching on the strength of HUMS indication. I think you make a good point about airworthiness, which is something EVERYONE MUST understand, HUMS cannot be used to ascertain an aircrafts airworthiness alone, it is merely part of the bigger toolbox. That said, there will no doubt be people of the opinion that if HUMS draws a pilots attention to something, and through subsequent gauge indications / control feedback etc, he chooses to invoke precautionary / emergency procedures, then that is good.
Personally I don't think ANYONE has a system that is reliable enough as to warrant such a cockpit display / warning system, and I agree that HUMS should be used as a post flight diagnostic tool, for engineering use. Pilot involvement should not exceed airborne system activation and de-activation, as a general rule of thumb.
However, being an open minded type of guy, I shall come and see your BMU for myself with great interest at Helitech.
I never have been a supporter of cockpit displays for HUMS, for the very reason you mention, however your example is a little strong, if I was flying along with all my T's & P's ok, then there is no way on the planet I would take rash actions like ditching on the strength of HUMS indication. I think you make a good point about airworthiness, which is something EVERYONE MUST understand, HUMS cannot be used to ascertain an aircrafts airworthiness alone, it is merely part of the bigger toolbox. That said, there will no doubt be people of the opinion that if HUMS draws a pilots attention to something, and through subsequent gauge indications / control feedback etc, he chooses to invoke precautionary / emergency procedures, then that is good.
Personally I don't think ANYONE has a system that is reliable enough as to warrant such a cockpit display / warning system, and I agree that HUMS should be used as a post flight diagnostic tool, for engineering use. Pilot involvement should not exceed airborne system activation and de-activation, as a general rule of thumb.
However, being an open minded type of guy, I shall come and see your BMU for myself with great interest at Helitech.
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I’m amazed a thread about HUMS could get past 4 or 5 replies without the Sultan jumping in, but let me throw in some fodder.....
HUMS is a great idea – with a bad execution.... HUMS could cause the most significant change in the cost of operating a helicopter that has occurred in decades.... HUMS is a smoke detector in a concrete room where you can’t store flammable objects.... HUMS is aviation’s answer to the chicken and egg paradox... HUMS is the bastard step-child resulting from a drunken night spent between a dynamicist and an avionics engineer. (or was that the Sultan). Anyway... All this is true to a degree,
The HUMS concept is simple. Lifed components (those which are replaced based on hours) have their life expectancy determined by assuming a conservative-case operating spectrum in a worst-case certified environment, plus a safety factor. Lifed components are that way because they typically fail in a way that is not preceded by some other effect (ie: cracks or wear indications that would otherwise indicate it’s time for replacement.) When they go, it’s sudden and nasty. So there has to be a good margin built into the calculation of life expectancy. The resulting schedule of required replacements and inspections based on flight hours is a major factor in the current expense of operating a helicopter – and it’s nasty.
So the concept of HUMS comes along with the promise to change all that. HUMS has really two parts – the logging part and the predicting part. They are both intended to allow us to extend the life of these components.
For the logging part, the HUMS logs the flight “regime.” It uses the flight sensors to accurately record how the helicopter is being used and for how long in each regime: Altitude, temperatures, torque, accelerations, and other information is recorded. What is recorded depends on what factors drive the life of the component (Is it altitude, temperature, hard landings, accumulated vibrational stress, etc.) This data is used in order that we can get away from the worst case assumptions about the flight regime. And this then allows us to extend component lives accordingly.
The other part is vibration trend data. As noted, if component failures were preceded by a predictable property, and that property exhibits itself well in advance of the actual failure, then we can use detection of that to replace components, rather than just clocking hours. In engines, the relative relationship between parameters (temperature / Ng, etc.) in the context of the flight regime, will give early indications of engine wear and impending failure without the need for adding sensors – just software. Helicopters usually require the addition of sensors. For example, certain bearings show a temperature rise over ambient prior to failure, others show vibration. Vibration is the most typical thing used to detect something starting to go wrong. (For years the HUMS was a 6th sense embedded in the butt of an experienced pilot.)
So the engineer in us says “THIS IS GREAT!!!” I can extend the certified life on components based on actual usage data, and I can reduce the margins for manufacturing variations, since if the failure does occur prematurely, my HUMS will detect it. Costs will go down... sales will go up.... avionics and airframe manufacturers will rejoice.... overall safety will go up.... there will be world peace...... (And I get a free RT&B system at the same time.)
So now comes the chicken and egg stuff. Enter the business folks and regulatory agencies (plus the product liability lawyers and all their friends). The Avionics guy wants to sell the system and make money. The operator needs the extended life credit in order to justify the expense of the system. The Helicopter OEM – who typically doesn’t make money on avionics – can’t justify the expense of determining the credit to be given. There is a huge expense to determining exactly how much the life can be extended, and how dependable the HUMS prediction is. The cost of that engineering, and the HUMS is going to drive up the cost of the helicopter. For his trouble, he’s going to lose on support sales. So unless you can show HUMS as directly contributing to selling more helicopters, its hard to get the Helicopter OEM to play ball. Add to that the potential for product liability – what happens on the day you lose an aircraft because the HUMS failed to detect an impending failure? How do you explain HUMS to a jury. So you either have to get a lot of test data, or a lot of in field data. For the in-field data to be significant, it has to go beyond the standard life of components.
Quite frankly, the best way for HUMS to really fulfill its promise is for it to become standard equipment delivered by the OEM and be the basis for component replacements used in the certification basis. That way everyone gets what they want. But the OEM has to be convinced that this provides the helicopter with a significant advantage in the market.
What has actually happened has been a bit of a ruse. Avionics manufacturers – who have the most to gain initially - have campaigned to the operators to demand HUMs, even when there is no component credit. The argument used to promote HUMs is safety. It has been made successfully enough that HUMS is now included as required equipment for some operators. In examination – that is a very hollow argument, but one that still gets made.
Advocates argue that the HUMS vibration monitoring allows the prediction of impending failures..... but remember how this works: HUMs detects failures which follow a predictable pattern of failure. By definition, if its predictable, then it should have been factored into determining the certified life of the component, and with the current margins, you are sure to replace the component long before you get into the pattern the HUMS was designed for.
The only safety improvement occurs IF the engineers were wrong in their calculations about the life of a component (applicable more to new designs), or IF a component fails – due to manufacturing defect - before its time, and then IF that failure happens to follow the pattern the HUMS was designed to detect, and IF the failure progress is still slow enough to still allow safe flight and landing. Then, man! it is your lucky day. That’s a lot of IF’s for a system that typically runs in the 6 figures.
Personally, I am an advocate of HUMS - but not the way I see it used today. I think HUMS has great promise, but I think operators are being duped into demanding and buying HUMS in a way that provides them very little for their money. I already know of some big operators who have spent millions on HUMS equipment to find it of little more benefit than a rotor track and balance system. As a result, I see potential for backlash before HUMS gets fielded properly. When that sort of thing happens, it will poison the market for the real HUMS with real credit, and real safety improvement / cost reduction potential.
HUMS is a great idea – with a bad execution.... HUMS could cause the most significant change in the cost of operating a helicopter that has occurred in decades.... HUMS is a smoke detector in a concrete room where you can’t store flammable objects.... HUMS is aviation’s answer to the chicken and egg paradox... HUMS is the bastard step-child resulting from a drunken night spent between a dynamicist and an avionics engineer. (or was that the Sultan). Anyway... All this is true to a degree,
The HUMS concept is simple. Lifed components (those which are replaced based on hours) have their life expectancy determined by assuming a conservative-case operating spectrum in a worst-case certified environment, plus a safety factor. Lifed components are that way because they typically fail in a way that is not preceded by some other effect (ie: cracks or wear indications that would otherwise indicate it’s time for replacement.) When they go, it’s sudden and nasty. So there has to be a good margin built into the calculation of life expectancy. The resulting schedule of required replacements and inspections based on flight hours is a major factor in the current expense of operating a helicopter – and it’s nasty.
So the concept of HUMS comes along with the promise to change all that. HUMS has really two parts – the logging part and the predicting part. They are both intended to allow us to extend the life of these components.
For the logging part, the HUMS logs the flight “regime.” It uses the flight sensors to accurately record how the helicopter is being used and for how long in each regime: Altitude, temperatures, torque, accelerations, and other information is recorded. What is recorded depends on what factors drive the life of the component (Is it altitude, temperature, hard landings, accumulated vibrational stress, etc.) This data is used in order that we can get away from the worst case assumptions about the flight regime. And this then allows us to extend component lives accordingly.
The other part is vibration trend data. As noted, if component failures were preceded by a predictable property, and that property exhibits itself well in advance of the actual failure, then we can use detection of that to replace components, rather than just clocking hours. In engines, the relative relationship between parameters (temperature / Ng, etc.) in the context of the flight regime, will give early indications of engine wear and impending failure without the need for adding sensors – just software. Helicopters usually require the addition of sensors. For example, certain bearings show a temperature rise over ambient prior to failure, others show vibration. Vibration is the most typical thing used to detect something starting to go wrong. (For years the HUMS was a 6th sense embedded in the butt of an experienced pilot.)
So the engineer in us says “THIS IS GREAT!!!” I can extend the certified life on components based on actual usage data, and I can reduce the margins for manufacturing variations, since if the failure does occur prematurely, my HUMS will detect it. Costs will go down... sales will go up.... avionics and airframe manufacturers will rejoice.... overall safety will go up.... there will be world peace...... (And I get a free RT&B system at the same time.)
So now comes the chicken and egg stuff. Enter the business folks and regulatory agencies (plus the product liability lawyers and all their friends). The Avionics guy wants to sell the system and make money. The operator needs the extended life credit in order to justify the expense of the system. The Helicopter OEM – who typically doesn’t make money on avionics – can’t justify the expense of determining the credit to be given. There is a huge expense to determining exactly how much the life can be extended, and how dependable the HUMS prediction is. The cost of that engineering, and the HUMS is going to drive up the cost of the helicopter. For his trouble, he’s going to lose on support sales. So unless you can show HUMS as directly contributing to selling more helicopters, its hard to get the Helicopter OEM to play ball. Add to that the potential for product liability – what happens on the day you lose an aircraft because the HUMS failed to detect an impending failure? How do you explain HUMS to a jury. So you either have to get a lot of test data, or a lot of in field data. For the in-field data to be significant, it has to go beyond the standard life of components.
Quite frankly, the best way for HUMS to really fulfill its promise is for it to become standard equipment delivered by the OEM and be the basis for component replacements used in the certification basis. That way everyone gets what they want. But the OEM has to be convinced that this provides the helicopter with a significant advantage in the market.
What has actually happened has been a bit of a ruse. Avionics manufacturers – who have the most to gain initially - have campaigned to the operators to demand HUMs, even when there is no component credit. The argument used to promote HUMs is safety. It has been made successfully enough that HUMS is now included as required equipment for some operators. In examination – that is a very hollow argument, but one that still gets made.
Advocates argue that the HUMS vibration monitoring allows the prediction of impending failures..... but remember how this works: HUMs detects failures which follow a predictable pattern of failure. By definition, if its predictable, then it should have been factored into determining the certified life of the component, and with the current margins, you are sure to replace the component long before you get into the pattern the HUMS was designed for.
The only safety improvement occurs IF the engineers were wrong in their calculations about the life of a component (applicable more to new designs), or IF a component fails – due to manufacturing defect - before its time, and then IF that failure happens to follow the pattern the HUMS was designed to detect, and IF the failure progress is still slow enough to still allow safe flight and landing. Then, man! it is your lucky day. That’s a lot of IF’s for a system that typically runs in the 6 figures.
Personally, I am an advocate of HUMS - but not the way I see it used today. I think HUMS has great promise, but I think operators are being duped into demanding and buying HUMS in a way that provides them very little for their money. I already know of some big operators who have spent millions on HUMS equipment to find it of little more benefit than a rotor track and balance system. As a result, I see potential for backlash before HUMS gets fielded properly. When that sort of thing happens, it will poison the market for the real HUMS with real credit, and real safety improvement / cost reduction potential.
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Well Avnx EO, we really do agree! I think the promise of hums is vast, the actual delivered so far is too small (but still mostly worthwhile). Some additions to your thoughts, for comment:
1) The regime recognition is the way we do it now, where we determine what the aircraft is doing, and then try to guess what the loads the parts are subjected to. In a while, we will simply measure the loads the parts experience, cut out all the guess work, and be much closer to the actual stress the part has experienced. Why not, we can swallow a camera to photograph our insides, after all.
2) Linking component lives to this stress estimate is surely better than the guesswork we now use, where assumed spectra are applied per hour, as though all helos are operated identically. Actual life experience will always be better. getting CAA and FAA to agree will take a bit of work, however.
1) The regime recognition is the way we do it now, where we determine what the aircraft is doing, and then try to guess what the loads the parts are subjected to. In a while, we will simply measure the loads the parts experience, cut out all the guess work, and be much closer to the actual stress the part has experienced. Why not, we can swallow a camera to photograph our insides, after all.
2) Linking component lives to this stress estimate is surely better than the guesswork we now use, where assumed spectra are applied per hour, as though all helos are operated identically. Actual life experience will always be better. getting CAA and FAA to agree will take a bit of work, however.
Last edited by NickLappos; 6th Sep 2003 at 20:51.
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Avnx EO said,
"Advocates argue that the HUMS vibration monitoring allows the prediction of impending failures..... but remember how this works: HUMs detects failures which follow a predictable pattern of failure. By definition, if its predictable, then it should have been factored into determining the certified life of the component, and with the current margins, you are sure to replace the component long before you get into the pattern the HUMS was designed for. "
What about the human factor errors, like installation errors and misalignment? While these are not factors in certification, mistakes do happen when driveshaft clamps or shims are not properly put back in place. These type of failures can be effectively tracked.
A customer recently rejected an engine due to high turbine vibration. At teardown there were deposits on the wheel. Turns out that aircraft had been flying to a platform that was spewing effluents (sp?) bad enough that the pilots had to clean their winsheild prior to taking off. They thought nothing of it, but vibration analysis removed the engine prior to any catostrophic damage.
You also downplay the ability to know the vibration levels with respect to ride quality. Many pilots have a different perspective on how smooth their aircraft flies. I have seen a new crew come on hitch and immediately ground the aircraft due to high vibrations, yet the pilots that were flying the aircraft said it felt fine. Knowing these levels ahead of time and not waiting for someone to down the aircraft because the aircraft does not feel comfortable does offer quite a bit of payback as it allows you to schedule the maintenance. Quite a few aircraft have recurring vibe checks of different components. Reviewing the data from HUMS allows them to sign the check off without the need to install portable equipment and the associated ground run. This also saved a start cycle too.
On non bussed non FADEC aircraft, exceedance monitoring will offer one of the greatest paybacks. I've seen write ups where the pilot stated torque went to 105% and the copilot said it went to 95%. What would you do on a non HUMS aircraft? Most would perform an overtorque inspection, a costly endeavor. Yet when reviewing the data the aircraft only went to 99%. That one instance made a considerable payback on the acquistion cost of HUMS.
Aircraft parameter recording as used in Exceedance monitoring can also be an effective troubleshooting tool. Take the writeup that the engine starts hot... First question asked of the pilot is what was the battery voltage, he shrugs his shoulders and say, I am not sure, you look at the parameter data and see the battery bus voltage dropped to 15 volts during start. You now replace the battery instead of adjusting fuel controls. How about a write up that said, #1 engine failed power assurance due to high N1. A review of the parameter data shows the N1 lower than indicated on the gage. At next run up, real time viewing of the parameter data indicates that in fact the N1 gage is reading higher than actual. You change the N1 gage not the engine...
Safety does play an important factor, but HUMS also plays a large part in planning and logistics.
I too agree that in the beginning that HUMS was billed as the answer to all problems with Usage credits as the biggest selling point. However, Health monitoring plays an effective role too. Useage without credits also has paybacks, as in flight time tracking can save a considerable amount in actual usage, just from rounding errors alone.
HUMS without credits does offer payback, it just does not offer the magic bullet that usage credits offer in a distinct number that you can assign a cost per hour payback.
chuckolamofola
"Advocates argue that the HUMS vibration monitoring allows the prediction of impending failures..... but remember how this works: HUMs detects failures which follow a predictable pattern of failure. By definition, if its predictable, then it should have been factored into determining the certified life of the component, and with the current margins, you are sure to replace the component long before you get into the pattern the HUMS was designed for. "
What about the human factor errors, like installation errors and misalignment? While these are not factors in certification, mistakes do happen when driveshaft clamps or shims are not properly put back in place. These type of failures can be effectively tracked.
A customer recently rejected an engine due to high turbine vibration. At teardown there were deposits on the wheel. Turns out that aircraft had been flying to a platform that was spewing effluents (sp?) bad enough that the pilots had to clean their winsheild prior to taking off. They thought nothing of it, but vibration analysis removed the engine prior to any catostrophic damage.
You also downplay the ability to know the vibration levels with respect to ride quality. Many pilots have a different perspective on how smooth their aircraft flies. I have seen a new crew come on hitch and immediately ground the aircraft due to high vibrations, yet the pilots that were flying the aircraft said it felt fine. Knowing these levels ahead of time and not waiting for someone to down the aircraft because the aircraft does not feel comfortable does offer quite a bit of payback as it allows you to schedule the maintenance. Quite a few aircraft have recurring vibe checks of different components. Reviewing the data from HUMS allows them to sign the check off without the need to install portable equipment and the associated ground run. This also saved a start cycle too.
On non bussed non FADEC aircraft, exceedance monitoring will offer one of the greatest paybacks. I've seen write ups where the pilot stated torque went to 105% and the copilot said it went to 95%. What would you do on a non HUMS aircraft? Most would perform an overtorque inspection, a costly endeavor. Yet when reviewing the data the aircraft only went to 99%. That one instance made a considerable payback on the acquistion cost of HUMS.
Aircraft parameter recording as used in Exceedance monitoring can also be an effective troubleshooting tool. Take the writeup that the engine starts hot... First question asked of the pilot is what was the battery voltage, he shrugs his shoulders and say, I am not sure, you look at the parameter data and see the battery bus voltage dropped to 15 volts during start. You now replace the battery instead of adjusting fuel controls. How about a write up that said, #1 engine failed power assurance due to high N1. A review of the parameter data shows the N1 lower than indicated on the gage. At next run up, real time viewing of the parameter data indicates that in fact the N1 gage is reading higher than actual. You change the N1 gage not the engine...
Safety does play an important factor, but HUMS also plays a large part in planning and logistics.
I too agree that in the beginning that HUMS was billed as the answer to all problems with Usage credits as the biggest selling point. However, Health monitoring plays an effective role too. Useage without credits also has paybacks, as in flight time tracking can save a considerable amount in actual usage, just from rounding errors alone.
HUMS without credits does offer payback, it just does not offer the magic bullet that usage credits offer in a distinct number that you can assign a cost per hour payback.
chuckolamofola
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You make an important point about exceedance monitoring for non-FADEC engines. I admit I have been very spoiled since everthing I work on these days is FADEC or at least electronically controlled. I also don't deny that there are certain faults that HUMS will luckily catch. But that's not what HUMS was designed for (or priced for), and it's somewhat like using a sledge hammer to drive a thumb tack. There are cheaper systems that will do those things. (A low cost engine monitor for example.)
There will always be the odd anecdotal thing that happens to get caught by the HUMS. I'm sure the HUMS salespeople don't peddle the system as a tubine shi.. ingestor detector. But even there, you note that the problem was significant enough to be detected an reported by the pilot. You mention workmanship errors and some other odd problem conditions. I know everyone will jump on me for this - but it's still dumb luck. If we look at the spectrum of defects likely to escape the process already in place, there are very few of those which would likely be picked up by HUMS. I can find a lot of very tragic incidents in that same vein that wouldn't have been caught by HUMs.
As for Nick, he always goes me one further. (He's more spoiled than me) where it's easy to sensor everything. I'm still working enough on the lights and mediums where sensors and wire (lightning protected wire these days) adds up in dollars and pounds pretty fast. That regime recognition is still a really useful way to keep down the expense and make the technology accessible.
Fact remains that even with regime recognition, HUMS is a major intrusive system on a "conventionally instrumented" (steam gauge) aircraft. On a data-bussed aircraft, regime recognition-based HUMS can be added for next to nothing - and could be done as basic equipment. That's where I see HUMs finally being able to deliver on its promise.
On "regime recognition." Nick, who was that PhD at Sikorsky that coined the term. I recall him as the genuine stereotypical mad scientist, and I always consider him the father of HUMs. I was rivetted by his presentation at Sikorsky back in '81 or '82 was it? In a way, more of that concept has worked its way into how our cars deploy air bags than into our helicopters. shame.
I hope ben123 has gotten what he wanted out of this.
Later...
There will always be the odd anecdotal thing that happens to get caught by the HUMS. I'm sure the HUMS salespeople don't peddle the system as a tubine shi.. ingestor detector. But even there, you note that the problem was significant enough to be detected an reported by the pilot. You mention workmanship errors and some other odd problem conditions. I know everyone will jump on me for this - but it's still dumb luck. If we look at the spectrum of defects likely to escape the process already in place, there are very few of those which would likely be picked up by HUMS. I can find a lot of very tragic incidents in that same vein that wouldn't have been caught by HUMs.
As for Nick, he always goes me one further. (He's more spoiled than me) where it's easy to sensor everything. I'm still working enough on the lights and mediums where sensors and wire (lightning protected wire these days) adds up in dollars and pounds pretty fast. That regime recognition is still a really useful way to keep down the expense and make the technology accessible.
Fact remains that even with regime recognition, HUMS is a major intrusive system on a "conventionally instrumented" (steam gauge) aircraft. On a data-bussed aircraft, regime recognition-based HUMS can be added for next to nothing - and could be done as basic equipment. That's where I see HUMs finally being able to deliver on its promise.
On "regime recognition." Nick, who was that PhD at Sikorsky that coined the term. I recall him as the genuine stereotypical mad scientist, and I always consider him the father of HUMs. I was rivetted by his presentation at Sikorsky back in '81 or '82 was it? In a way, more of that concept has worked its way into how our cars deploy air bags than into our helicopters. shame.
I hope ben123 has gotten what he wanted out of this.
Later...
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"There are cheaper systems that will do those things. (A low cost engine monitor for example.)"
Cost are coming down, most all HUMS manufacturers today offer systems that target the tangible paybacks. Face it, the FAA software requirements make the idea of credits a reality in the far distant future bused or non bused aircraft. An engine monitor is just that an engine monitor. What about vibration analysis, are you still going to do that with portable equipment? Add up the cost of an engine monitor and the cost of a small vibe montioring system and you now have the price of one of the newer HUMS systems being developed.
"I'm sure the HUMS salespeople don't peddle the system as a tubine shi.. ingestor detector. But even there, you note that the problem was significant enough to be detected an reported by the pilot."
No the pilots did not report the high vibration situation, it was found via vibe monitoring. After teardown and the evidence of gunk on the turbine wheel and then after an investigation with the pilots, the cause of the gunk was found.
What's major intrusive on a steam gage driven aircraft? A box that for the most part reads the same signals as the engine instruments themselves? Yep, on a bussed aircraft you have a lot less wires to connect, but how does it effect regime recognition any differently than a HUMS equiped analog aircraft? Both aircraft types require one LRU and depending on the HUMS manufacturer bused or non bused can use the same LRU. Both have the same number of vibration sensors...
chuckolamofola
Cost are coming down, most all HUMS manufacturers today offer systems that target the tangible paybacks. Face it, the FAA software requirements make the idea of credits a reality in the far distant future bused or non bused aircraft. An engine monitor is just that an engine monitor. What about vibration analysis, are you still going to do that with portable equipment? Add up the cost of an engine monitor and the cost of a small vibe montioring system and you now have the price of one of the newer HUMS systems being developed.
"I'm sure the HUMS salespeople don't peddle the system as a tubine shi.. ingestor detector. But even there, you note that the problem was significant enough to be detected an reported by the pilot."
No the pilots did not report the high vibration situation, it was found via vibe monitoring. After teardown and the evidence of gunk on the turbine wheel and then after an investigation with the pilots, the cause of the gunk was found.
What's major intrusive on a steam gage driven aircraft? A box that for the most part reads the same signals as the engine instruments themselves? Yep, on a bussed aircraft you have a lot less wires to connect, but how does it effect regime recognition any differently than a HUMS equiped analog aircraft? Both aircraft types require one LRU and depending on the HUMS manufacturer bused or non bused can use the same LRU. Both have the same number of vibration sensors...
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Just a quick note.. everybody talking about engines, and cheap monitoring systems, anybody heard of a cheap monitoring system for a TRANSMISSION SYSTEM???? Do these cheap systems tell us much about what the aircraft was doing at the time of fault detection, like height, attitude, heading, Airspeed etc?? Granted all of the above are "nice to have" but...
HUMS can detect certain faults, I see it daily, and yes it generates false alerts too, its a learning process. Learn thresholds by aircraft type, learn from mistakes or missed faults new ways of detecting said faults. I admit its reactive at the moment, but isn't reactive better than inactive???
We are all quick (And sometimes justified) to put the boot into HUMS, but there are a few people out there trying to make it better, Nick and Chuck, you guys know that perfectly well.
HUMS is something which ought to be brought into the affordability range of anyone who wants it, and if through operator and manufacturer feedback we can make these systems what they should be, then maybe everybody would want them. Then again, affordable and reliable.. do I ask too much
HUMS can detect certain faults, I see it daily, and yes it generates false alerts too, its a learning process. Learn thresholds by aircraft type, learn from mistakes or missed faults new ways of detecting said faults. I admit its reactive at the moment, but isn't reactive better than inactive???
We are all quick (And sometimes justified) to put the boot into HUMS, but there are a few people out there trying to make it better, Nick and Chuck, you guys know that perfectly well.
HUMS is something which ought to be brought into the affordability range of anyone who wants it, and if through operator and manufacturer feedback we can make these systems what they should be, then maybe everybody would want them. Then again, affordable and reliable.. do I ask too much
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Hey, the engine monitor was just one example. There are also on-board RT&B and Low-cost vibe monitoring packages that don't profess to be complete HUMS. I didn't pretend to supply an exhaustive list, and I didn't want to pull out the litany of possibilities. It largely depends on what you've already got on-board.
The fact remains that I can provide everything a HUMS can currently provide embedded in other systems already in the aircraft, but unless you have a box called "HUMS" they won't believe you meet the requirement. (I don't know what a HUMS is, but by golly, I gotta have one, 'cause people say its safer.)
It also reminds me of an old joke we used to have: What's the difference between an "interface unit" with computing power, and a "misson computer" with interfacing capability..... about $150K US. HUMS is somewhat the same story.
Hey, the engine monitor was just one example. There are also on-board RT&B and Low-cost vibe monitoring packages that don't profess to be complete HUMS. I didn't pretend to supply an exhaustive list, and I didn't want to pull out the litany of possibilities. It largely depends on what you've already got on-board.
The fact remains that I can provide everything a HUMS can currently provide embedded in other systems already in the aircraft, but unless you have a box called "HUMS" they won't believe you meet the requirement. (I don't know what a HUMS is, but by golly, I gotta have one, 'cause people say its safer.)
It also reminds me of an old joke we used to have: What's the difference between an "interface unit" with computing power, and a "misson computer" with interfacing capability..... about $150K US. HUMS is somewhat the same story.
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AVNX EO
Does your system provide a full Groundstation, with data download, analysis, archiving, trend monitoring, tech support etc etc etc???
I know that a company from El Monte make a really top notch RTB system, but their reps claim it does everything HUMS does, which I can assure you is a wildly overstated claim.
A HUMS system in essence is any system which monitors and records health and usage data. It does not specify a number of sensors, or definate locations. However, the aim of the system is to prevent catastrophic loss of aircraft as far as is possible through the monitoring of systems with no built in redundancy.. that means the possible list of locations and number of sensors is limitless. Flogging hardware and calling it HUMS is easy, providing the technical back up to turn that data into useful information to the boys on the shop floor, without causing them unneccessary work, and providing third line engineering back up, to pinpoint faults that are otherwise missed, is the clever bit.
Providing an automated, and reliable data analysis system is clever too, none of us have quite perfected it..... yet
Does your system provide a full Groundstation, with data download, analysis, archiving, trend monitoring, tech support etc etc etc???
I know that a company from El Monte make a really top notch RTB system, but their reps claim it does everything HUMS does, which I can assure you is a wildly overstated claim.
A HUMS system in essence is any system which monitors and records health and usage data. It does not specify a number of sensors, or definate locations. However, the aim of the system is to prevent catastrophic loss of aircraft as far as is possible through the monitoring of systems with no built in redundancy.. that means the possible list of locations and number of sensors is limitless. Flogging hardware and calling it HUMS is easy, providing the technical back up to turn that data into useful information to the boys on the shop floor, without causing them unneccessary work, and providing third line engineering back up, to pinpoint faults that are otherwise missed, is the clever bit.
Providing an automated, and reliable data analysis system is clever too, none of us have quite perfected it..... yet
