A simpler daily-life example will help elucidate PDM (Predictive Maintenance for the benefit of first time readers).
Say your car has an oil temperature gauge, and an oil pressure gauge. For a while you’ve been noticing slightly higher-than-normal oil temperatures and lower-than-normal oil pressures. There is the more obvious likelihood that the oil quantity is insufficient. So you top up the oil quantity and take a general look-around and under the chassis to make sure there’s no visible signs of oil leakages. The gauges now indicate normal oil temperatures and pressures. However, after a while the problem recurs. What does that tell you? In simple terms, a trip to the mechanic is on the cards! You really don’t want to come to a situation where your car comes to a complete halt. For some strange reason the likelihood of this happening is highest when you most want to reach your destination! Or, worse, when you’re in the middle of evening rush hour!! I’ve heard all those stories from blokes complaining about their cars conspiring with them, right at the opportune moment! Nevertheless, conspiracies aside, what really prompted you to take your car to your mechanic? What prompted you to take preventive measures? The higher or lower than normal indications from the gauges in your car.
Predictive Maintenance is no different in that you are essentially taking preventive measures to rectify a component well before it’s complete failure, which in-turn could have an adverse affect on the entire system. In predictive maintenance you’re constantly gathering data on the functioning parameters of components and systems, and monitoring that data (active or discreet monitoring) at specific intervals to ensure smooth and correct operations.
If a small component of the system shows abnormal readings, through past experience with that component, we can tell approximately how many hours further before failure of that component. As an example, this ‘small’ component may actually have a larger role to play in the system than many others. Therefore, getting advance notice of it’s impending failure makes it very important to ensure the overall system continues to function normally and, if required, continuously.
This ability to pre-empt component performance over a wide range of operating parameters forms the core of Predictive Maintenance.
Tuesday, October 6, 2009
Friday, July 31, 2009
Diagnosing PDM
Let’s go over the example in the previous post with a fine tooth comb. This analysis should help us understand just how beneficial PDM can be. It will also highlight how in a world without PDM, the long term impact on safety, efficiency and economy(cost) can be adverse.
When the aircraft is enroute between Mumbai and Delhi, the slight increase in EGT was not noted by the pilot since it was within limits. In technical parlance, though, it is precisely these small and gradual changes that indicate to the engineer/mechanic of a developing trend, if not an impending failure. The machine is telling you something. Something that may not create a concern in the immediate future, but is an indication that a fault is in the early stages of development; or, there seems to be a trend in development that will lead to a possible sudden catastrophic failure. If arrested in the early stages, it can save the machinery from further deterioration, which in turn enhances safety besides reducing costs and major delays down the line.
Between Bhopal and Chennai, the EGT comes within the caution range. The pilot makes a note of it in the defect register. However by now, thanks to PDM, all the engineers in the loop are not only aware of the anomaly, but are also aware that the EGT of this particular engine has been showing an upward tend for sometime. So, in other words it doesn’t really come as a surprise to them when the pilot reports it to the AME on arrival. In fact, he’s also had the time (while the aircraft was still enroute to Chennai) to call the AME in Delhi to get some background about the condition and the two would have had a brief chat on what could be the problem.
This is valuable, valuable in terms of time, valuable in understanding the impact on safety, valuable in measuring the impact on operations and what delays might be incurred or saved. Had the AME been hit with the defect of ‘an EGT in the caution range’ straight from the pilot on arrival, without prior warning, his mind would have been racing between what might be the problem, and whether he would have to ground the aircraft for major checks, to what an operational delay might do to the airline and it’s customers. Not to mention he’d have to provide a detailed report to the management the next day on why he delayed a flight for a possibly minor fault.
Coming to Mumbai, which is the major base for the aircraft in terms of availability of special tools, equipment and specially trained manpower. With prior information about the condition of number 2 engine, while the aircraft is enroute between Chennai and Mumbai, the AME will draw out a plan of action. He will have the time and space to make a balanced decision (taking into account safety, reliability, costs, future sectors to be flown etc), call for the necessary equipment, make arrangements to have his team of trained mechanics available and be prepared for the arrival of a reasonably sick engine that somehow needs to be turned around for the flight next day.
And finally, if the AME in Mumbai realizes while working on the engine that it may not be ready for the flight early next morning, he can warn the operations department of the airline to have another aircraft scheduled for next day, or cancel the flight and warn the passengers well in advance.
The difference between having PDM and not, is the Time in(on) your hands!
When the aircraft is enroute between Mumbai and Delhi, the slight increase in EGT was not noted by the pilot since it was within limits. In technical parlance, though, it is precisely these small and gradual changes that indicate to the engineer/mechanic of a developing trend, if not an impending failure. The machine is telling you something. Something that may not create a concern in the immediate future, but is an indication that a fault is in the early stages of development; or, there seems to be a trend in development that will lead to a possible sudden catastrophic failure. If arrested in the early stages, it can save the machinery from further deterioration, which in turn enhances safety besides reducing costs and major delays down the line.
Between Bhopal and Chennai, the EGT comes within the caution range. The pilot makes a note of it in the defect register. However by now, thanks to PDM, all the engineers in the loop are not only aware of the anomaly, but are also aware that the EGT of this particular engine has been showing an upward tend for sometime. So, in other words it doesn’t really come as a surprise to them when the pilot reports it to the AME on arrival. In fact, he’s also had the time (while the aircraft was still enroute to Chennai) to call the AME in Delhi to get some background about the condition and the two would have had a brief chat on what could be the problem.
This is valuable, valuable in terms of time, valuable in understanding the impact on safety, valuable in measuring the impact on operations and what delays might be incurred or saved. Had the AME been hit with the defect of ‘an EGT in the caution range’ straight from the pilot on arrival, without prior warning, his mind would have been racing between what might be the problem, and whether he would have to ground the aircraft for major checks, to what an operational delay might do to the airline and it’s customers. Not to mention he’d have to provide a detailed report to the management the next day on why he delayed a flight for a possibly minor fault.
Coming to Mumbai, which is the major base for the aircraft in terms of availability of special tools, equipment and specially trained manpower. With prior information about the condition of number 2 engine, while the aircraft is enroute between Chennai and Mumbai, the AME will draw out a plan of action. He will have the time and space to make a balanced decision (taking into account safety, reliability, costs, future sectors to be flown etc), call for the necessary equipment, make arrangements to have his team of trained mechanics available and be prepared for the arrival of a reasonably sick engine that somehow needs to be turned around for the flight next day.
And finally, if the AME in Mumbai realizes while working on the engine that it may not be ready for the flight early next morning, he can warn the operations department of the airline to have another aircraft scheduled for next day, or cancel the flight and warn the passengers well in advance.
The difference between having PDM and not, is the Time in(on) your hands!
Friday, June 26, 2009
PDM at work...real time.
Ok, so we’ve seen it all, and content that PDM can be useful. But how it works, is maybe better explained with an example.
An aircraft is on a flight between say Mumbai and Delhi. The sector for that aircraft for the day is something like this – Bombay, Delhi, Jaipur, Bhopal, Chennai, Bombay. Now I agree that’s quite a sector, but I need it to be that long to emphasize how and where PDM comes in.
Between Mumbai and Delhi, the Number 2 engine shows a slightly higher EGT (Exhaust Gat Temperature) than the number 1 engine. It’s still within limits, and therefore the pilot does not pay too much heed to it. However, EGT sensors still attach a signal of this to the ACARS and the AME on the ground at Delhi, receives this information. He makes a note of this in his inspection pocketbook which he will refer to when he’s making an inspection of the aircraft before signing out the aircraft from Delhi to Jaipur.
When the Aircraft arrives at Delhi, he does a quick examination of the number 2 engine, checking externally for anything unusual, checking oil levels, maybe a chip detector check and other routine inspections that could be indicative of the high EGT condition. He finds nothing unusual, but just puts a ‘tag’ on the ACARS note he received, so that the situation does not go unnoticed by the AME’s at the next destination.
Between Delhi and Bhopal, the situation is unchanged. However, a little after take off from Bhopal for Chennai, the EGT comes within the caution range. The pilot notices this and makes an entry in the PDR (Pilot Defect Report). However, even while the aircraft is in the air, the AME at Chennai, notices this via the report obtained from the ACARS. He also notices the small tag left by the AME at Delhi. He gets on the phone with the AME at Delhi to get a quick briefing on preliminary findings and the probable cause. Armed with some information he takes a look at the engine when it arrives at Chennai. He also has a quick word with the pilot on his version.
He decides to do an in-field/brief boroscopic examination; quite similar to an endoscopic examination done on humans to make a visual check of the state of things inside the engine. Ok, he’s found the likely cause of the rising EGT. There seems to be an oil leak at a bearing compartment which is likely due to partial damage to an oil seal. He makes an assessment of the extent of damage, and concludes that there is some cause for concern, but not something which would require grounding the aircraft at Chennai. So, he makes an entry in the engine log book, replenishes the oil, signs out the aircraft, and briefs the AME in Bombay about the situation. Aircraft leaves for Bombay, and while the EGT continues to hover in the caution range, it does not exceed the limit.
Aircraft lands at Bombay at 10p.m and has completed it’s sectors for the day. It’s next flight is due next day at 7a.m. Overnight, the AME with his team of specialised technicians (whom he’s assembled even before the Aircraft arrived in Bombay, having had the information about the problem in advance), rectifies the problem, and completes an engine test run. The Aircraft is ready to go at 0700hrs next day!
Now, that’s an example…! Let’s analyze this further next time!
An aircraft is on a flight between say Mumbai and Delhi. The sector for that aircraft for the day is something like this – Bombay, Delhi, Jaipur, Bhopal, Chennai, Bombay. Now I agree that’s quite a sector, but I need it to be that long to emphasize how and where PDM comes in.
Between Mumbai and Delhi, the Number 2 engine shows a slightly higher EGT (Exhaust Gat Temperature) than the number 1 engine. It’s still within limits, and therefore the pilot does not pay too much heed to it. However, EGT sensors still attach a signal of this to the ACARS and the AME on the ground at Delhi, receives this information. He makes a note of this in his inspection pocketbook which he will refer to when he’s making an inspection of the aircraft before signing out the aircraft from Delhi to Jaipur.
When the Aircraft arrives at Delhi, he does a quick examination of the number 2 engine, checking externally for anything unusual, checking oil levels, maybe a chip detector check and other routine inspections that could be indicative of the high EGT condition. He finds nothing unusual, but just puts a ‘tag’ on the ACARS note he received, so that the situation does not go unnoticed by the AME’s at the next destination.
Between Delhi and Bhopal, the situation is unchanged. However, a little after take off from Bhopal for Chennai, the EGT comes within the caution range. The pilot notices this and makes an entry in the PDR (Pilot Defect Report). However, even while the aircraft is in the air, the AME at Chennai, notices this via the report obtained from the ACARS. He also notices the small tag left by the AME at Delhi. He gets on the phone with the AME at Delhi to get a quick briefing on preliminary findings and the probable cause. Armed with some information he takes a look at the engine when it arrives at Chennai. He also has a quick word with the pilot on his version.
He decides to do an in-field/brief boroscopic examination; quite similar to an endoscopic examination done on humans to make a visual check of the state of things inside the engine. Ok, he’s found the likely cause of the rising EGT. There seems to be an oil leak at a bearing compartment which is likely due to partial damage to an oil seal. He makes an assessment of the extent of damage, and concludes that there is some cause for concern, but not something which would require grounding the aircraft at Chennai. So, he makes an entry in the engine log book, replenishes the oil, signs out the aircraft, and briefs the AME in Bombay about the situation. Aircraft leaves for Bombay, and while the EGT continues to hover in the caution range, it does not exceed the limit.
Aircraft lands at Bombay at 10p.m and has completed it’s sectors for the day. It’s next flight is due next day at 7a.m. Overnight, the AME with his team of specialised technicians (whom he’s assembled even before the Aircraft arrived in Bombay, having had the information about the problem in advance), rectifies the problem, and completes an engine test run. The Aircraft is ready to go at 0700hrs next day!
Now, that’s an example…! Let’s analyze this further next time!
Monday, June 22, 2009
A world Without PDM....
From an Aircraft Maintenance engineer’s perspective, it’s like walking to an aircraft that just arrived, blind! Not a clue about even the existence of the snag let alone the system affected or the location. Pilot defect reports are a help but they can sometimes be cryptic, and sometimes non-specific to the mechanic. This in turn requires further discussion between the pilot and mechanic to put a finger on the exact nature and cause of the problem. All this while…you’re eating away into that precious commodity – TIME!
Given the shortage of time then, and, the pressure to get the flight going (waiting passengers can get very irksome, even dangerous!) the AME usually ‘defers’ the defective component/ item. That is, within the framework of safety, defer the maintenance task to be conducted at the next base, and release the flight for now.
In plain terms, we gather information about the defect at Base # 1, and have it rectified at Base # 2; that is, ofcourse if the maintenance on the defective component can be deferred. If the component is an absolute necessary for safe flight,…well, irksome passengers…aka screaming, a little crying, lots of demanding…!
A maintenance world without PDM, is a reactive one at best. One that potentially compromises safety, increases costs, and leaves a lingering thought in the mind of the AME, “I hope…..!”
Next up, an example of PDM.
Given the shortage of time then, and, the pressure to get the flight going (waiting passengers can get very irksome, even dangerous!) the AME usually ‘defers’ the defective component/ item. That is, within the framework of safety, defer the maintenance task to be conducted at the next base, and release the flight for now.
In plain terms, we gather information about the defect at Base # 1, and have it rectified at Base # 2; that is, ofcourse if the maintenance on the defective component can be deferred. If the component is an absolute necessary for safe flight,…well, irksome passengers…aka screaming, a little crying, lots of demanding…!
A maintenance world without PDM, is a reactive one at best. One that potentially compromises safety, increases costs, and leaves a lingering thought in the mind of the AME, “I hope…..!”
Next up, an example of PDM.
Thursday, June 18, 2009
Predicting Aircraft Maintenance..?
Going by the cue of my last post, time, or more fittingly the conservation of it, appears to be the primary motivation behind Predictive Maintenance (PDM). So what exactly is PDM?
Imagine an aircraft soaring at 36000ft develops a snag say in it’s hydraulic system. Essential items that are affected by it include Flight control systems, Landing gear systems, Brakes and Anti-skid etc. Now, there are independent standby hydraulic systems in most airliners today. So, you wouldn’t exactly plunge earthward; but, you still need to ensure that the snag is rectified at the next base. I.e., the aircraft cannot take-off to it’s next destination without snag rectification. PDM systems basically detect the snag (in flight) and transfer detailed descriptions and locations of the snag to base via ACARS (more on ACARS here). The mechanic on duty gets the details, studies the snag, prepares a rectification action plan and gets all necessary equipment and manpower ready. Just as the aircraft lands and rolls in to the gates, the mechanic trundles out, fully equipped, to the aircraft. While passengers unload/reload, he has rectified the snag and the Aircraft is ready to go!
Simple? Yes, but there are constraints here too. More on those later. Right now, we know what a predictive maintenance can do, and, that it can prove to be an important advantage. One that puts time…on your side.
Imagine an aircraft soaring at 36000ft develops a snag say in it’s hydraulic system. Essential items that are affected by it include Flight control systems, Landing gear systems, Brakes and Anti-skid etc. Now, there are independent standby hydraulic systems in most airliners today. So, you wouldn’t exactly plunge earthward; but, you still need to ensure that the snag is rectified at the next base. I.e., the aircraft cannot take-off to it’s next destination without snag rectification. PDM systems basically detect the snag (in flight) and transfer detailed descriptions and locations of the snag to base via ACARS (more on ACARS here). The mechanic on duty gets the details, studies the snag, prepares a rectification action plan and gets all necessary equipment and manpower ready. Just as the aircraft lands and rolls in to the gates, the mechanic trundles out, fully equipped, to the aircraft. While passengers unload/reload, he has rectified the snag and the Aircraft is ready to go!
Simple? Yes, but there are constraints here too. More on those later. Right now, we know what a predictive maintenance can do, and, that it can prove to be an important advantage. One that puts time…on your side.
Sunday, September 14, 2008
It’s all about the Time….
“Down the Camel Shed straight reaching three hundred kilometers per hour, braking down to 2nd gear sixty kilometers per hour….hohohoooo hard on the brakes, you can see the carbon dust flying as he hits the brakes for the chicane …now, accelerating out of the chicane on turn 11, getting on the power ….nice and early, around the last sequence of corners…bouncing over the curves….coming up to the start-finish line….is it going to be beat the time set by the Renault …lets keep an eye on the timing monitors…across the line,… …P1 ! for Lewis Hamilton… by nine thousandths of a second…!!”
Phew, exactly how fast is nine thousandths of a second…..!
That, was the race commentary I heard the other day on television…
The Formula 1 world championship is all about time! Hard core racing, car control, team work, mechanical reliability and technology from the simple drinking water bottle pump directing fluids into the driver’s helmet, to the complex aerodynamic wings on the front and rear of the car to generate down force. They all work towards one goal…to be the quickest…the fastest in every segment of the race. Time in Formula 1 is critical….
And so it is in many other areas. From a heart surgeons operating table to the business house dealing in cloth merchandise.
So where does technology fit into this quest for the race against time. The answer’s right there in the example above. A second is too long. Technology helps save time. Oh yes the ultimate reason driving people and businesses on the path to making the best of time, is the money! But let’s put that aside for another day….another Time !
Let’s see, I’m not going to waste a whole deal of time trying to showcase how over the years, man discovered that a fire could be started by rubbing stones together to the date when a turn of a knob gives us not only fire, but a far more economical, controlled, high calorific value, variable size… flame!
There are text books full of those and other ways in which technologies have been developed to make better use of time available.
Instead, lets get to an example that shows how existing technologies can be integrated toward the same goal. No new ‘state-of-the-art’ developments… No multi million dollar patents and years of research and experiments.
Just the simple no-nonsense approach of getting existing capabilities together, and creating a state-of-the-art ‘trend’!
Aircraft Maintenance will no longer be the same.!
Phew, exactly how fast is nine thousandths of a second…..!
That, was the race commentary I heard the other day on television…
The Formula 1 world championship is all about time! Hard core racing, car control, team work, mechanical reliability and technology from the simple drinking water bottle pump directing fluids into the driver’s helmet, to the complex aerodynamic wings on the front and rear of the car to generate down force. They all work towards one goal…to be the quickest…the fastest in every segment of the race. Time in Formula 1 is critical….
And so it is in many other areas. From a heart surgeons operating table to the business house dealing in cloth merchandise.
So where does technology fit into this quest for the race against time. The answer’s right there in the example above. A second is too long. Technology helps save time. Oh yes the ultimate reason driving people and businesses on the path to making the best of time, is the money! But let’s put that aside for another day….another Time !
Let’s see, I’m not going to waste a whole deal of time trying to showcase how over the years, man discovered that a fire could be started by rubbing stones together to the date when a turn of a knob gives us not only fire, but a far more economical, controlled, high calorific value, variable size… flame!
There are text books full of those and other ways in which technologies have been developed to make better use of time available.
Instead, lets get to an example that shows how existing technologies can be integrated toward the same goal. No new ‘state-of-the-art’ developments… No multi million dollar patents and years of research and experiments.
Just the simple no-nonsense approach of getting existing capabilities together, and creating a state-of-the-art ‘trend’!
Aircraft Maintenance will no longer be the same.!
Sunday, March 16, 2008
Aviation.....an introduction
From the time I really understood what a blog was all about (as I later found out a short for ‘weblog’ !), I’ve been trying to come up with ideas for my very own blog. It had to be associated with my obsession, it had to be uncomplicated (much as I am tempted to !), it had to be informative, and it had to be rich in clarity.
And so, after pondering stubbornly on how it would include all those, and allow me the patience to sit down and write, I came up with A&PTechnologies. Or Airframe and Powerplant technologies. Airframe and Powerplant happens to be my entry point to the aviation dream ….. Technologies is what causes all the pain! The need to learn, unlearn, relearn, only to unlearn all over again ! Technology is like that isn’t it….it ‘keeps you on your toes.’ The day you say “Enough!”, you WILL become redundant.
Before I get into the depths of technologies associated with Aviation, there’s a couple of thoughts on careers in aviation. The first career that comes to mind when dealing with aviation, is that of an Airline Pilot. He is no doubt at the forefront of any airliner you will see. There are those little less known heroes that put the aircraft up in the skies, keep the them flying safely, and other not-so-famous heroes who make aviation a Business to be run profitably!
So here I decided to attempt bridging the gap between a complicated but beautiful piece of machinery that uses state-of-the-art-technology - often lending itself to other industry’s, and our common understanding of it, in not-so-complicated terms.
Aviation……the Dream!
Somewhere in the process of growing up, most of us have looked up at the skies to that large airliner gliding effortlessly through and into our most vivid of dreams. “Ah ! I believe I can fly !!” No doubt it triggered a flood of emotion the first time you saw it. And, the little child in us blurts out – “ I want to be an Airline Pilot”
Over time, some of us grow up, others nurse that little dream somewhere deep down, and still others take that dream quite seriously embarking on the beautiful but complicated path that is Aviation. Like they say “looks can be deceptive” the glamour and glitz associated with aviation is just that. Having said that, it is also one tremendously satisfying career that will take you on a roller coaster of emotions, no different from what you perceived when you saw your fist “Jumbo in the sky!”
And so, after pondering stubbornly on how it would include all those, and allow me the patience to sit down and write, I came up with A&PTechnologies. Or Airframe and Powerplant technologies. Airframe and Powerplant happens to be my entry point to the aviation dream ….. Technologies is what causes all the pain! The need to learn, unlearn, relearn, only to unlearn all over again ! Technology is like that isn’t it….it ‘keeps you on your toes.’ The day you say “Enough!”, you WILL become redundant.
Before I get into the depths of technologies associated with Aviation, there’s a couple of thoughts on careers in aviation. The first career that comes to mind when dealing with aviation, is that of an Airline Pilot. He is no doubt at the forefront of any airliner you will see. There are those little less known heroes that put the aircraft up in the skies, keep the them flying safely, and other not-so-famous heroes who make aviation a Business to be run profitably!
So here I decided to attempt bridging the gap between a complicated but beautiful piece of machinery that uses state-of-the-art-technology - often lending itself to other industry’s, and our common understanding of it, in not-so-complicated terms.
Aviation……the Dream!
Somewhere in the process of growing up, most of us have looked up at the skies to that large airliner gliding effortlessly through and into our most vivid of dreams. “Ah ! I believe I can fly !!” No doubt it triggered a flood of emotion the first time you saw it. And, the little child in us blurts out – “ I want to be an Airline Pilot”
Over time, some of us grow up, others nurse that little dream somewhere deep down, and still others take that dream quite seriously embarking on the beautiful but complicated path that is Aviation. Like they say “looks can be deceptive” the glamour and glitz associated with aviation is just that. Having said that, it is also one tremendously satisfying career that will take you on a roller coaster of emotions, no different from what you perceived when you saw your fist “Jumbo in the sky!”
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