.

[Colonel Sanders]

.

[FenderManDan]

That is why my car does not go to the dealership anymore. They do it in the intervals programmed in the vehicle computer which are only beneficial to the dealership as the additional revenue source.

I do all my maintenance except oil changes and it is running perfectly. Key was to google the maint code reset procedure.

Just wish I could get the same done on the plane. Does anybody have an ac in owner maintenance category?

[crazy_aviator]

One of the more wasteful and asnine inspections is pulling out the interior in cessnas every 200 hrs ,,,every 500 hrs MAYBE but 200 hrs Thats like doing a complete run-up prior to every flight, of a 10 flight day!

[GA MX Trainer Dude]

Colonel


You left out this little tidbit:

Fast forward two decades to the 1960s, when a pair of gifted scientists who worked for United Airlines—aeronautical engineer Stanley Nowlan and mathematician Howard Heap—independently rediscovered these principles in their pioneering research on optimizing maintenance that revolutionized the way maintenance is done in air transport, military aviation, high-end bizjets and many non-aviation industrial applications.

So for the last 50 plus years the industry has adopted newer ways of doing things. Typical 200 hour and up inspection schedules for turbine powered aircraft are common. Even TC recognizes the changes and went to "On Condition" for certain things on private aircraft.

FYI - the issue of maintenance error contributing to damage has been around for a number of years - in the industry it is referred to as MID - Maintenance Induced Damage.

Reliability centered maintenance recognizes one very important thing missing from the article and that is "Early Component Failures". This would be what happens when you replace a unit on scheduled maintenance that is still working to an acceptable level but experience has show to have a high failure rate if left until the next scheduled check and the replacement unit fails in a short time frame. So yes it is going to show up as a failure shortly after the maintenance check. Since I don't have access to the original data I cannot know for sure that this effect was removed and also if the data was compiled over years of service rather than just months.

I do agree that unnecessary maintenance is not a good thing - both for reliability and for the pocketbook. 50 hour inspections on most aircraft is too short of an interval to be meaningful.

I was in charge of a fleet of aircraft a number of years ago and we tracked component failures. If I remember correctly we found about the following results as rounded off for percentages"

Components that made full time plus 10% - 80%
Components that made full time but not in a condition to go another 10% = 92%
Components that made more than 50% but did not make full time = 4%
Components that made less than 10% = 4%
Components with "out of box failures" that never saw service = 23%


These numbers were approximate but you can see that about 80% of the components were good up to a 10% increase in service life without failures.

So out of 123 units - 23 never saw service due to failures caught on installation - 4 crapped out within 10% of full time - another 4 made more than 50% but less than 100% - 92 made it to the 100% time - and 80 went on to a 110% time frame. The 10% is used because that is what TC used to allow for time trials.

The components included engines - piston in this case.

So based on the above in the case of a piston engine you would think that with an inspection completed at 100% time and what you could determine by a general inspection - and by the records that the case could be put forward to extending the basic Time Between Overhaul of this engine series another 10% - and TC would allow you to do this as a time trial process. There were some rules about this - like not time trialing 2 engines at the same time on the same aircraft etc.

So we did - we added the 10% - did the time trials and successfully upped the TBO life for our operation. Not much changed in regards to MTBF - Mean Time Between Failures - so with some serious urging from the finance department that if we got 10% more flying out of this process that we should go for another 10%.

So we did - our failure rate rose a bit and we were running at about 78% - so really only lost a couple out of the 100 or so we started with. So you would think that this would be a good thing - leave it on for 20% more than the manufacturers recommendations for TBO. We ran this process for about 18 months and then dropped back to the 110% figure with a #1 Cylinder change done between 80% - 90% as service records indicated that most of our engine failures were a result of the #1 cylinder failing and causing the entire engine to be removed due to that specific failure mode. On this engine P&W R1830 - the #1 cylinder sits behind the Propeller Governor and does not get the cooling that the other cylinders got and as a result failed most often. Preventative "Evil" maintenance allowed us to fly the engine right up to the 120% for 78% of the engines. But this preventative "Evil" maintenance was not scheduled - whoops - yes it was in our organization as a result of service experience.

So why did we reduce the TBO to 110% rather than going all the way to the 120%???

Simple - our overhaul costs doubled in the last 10% run. At 110% we would for example change all the bearings and bushings in the accessory gearbox - at 120% we had to replace the bearings, bushings, all the gears, the oil pumps, and the drive shafts due to the accelerated wear that came from excessively worn bearings and bushings. It wasn't long before we heard from finance regarding what the extra time was costing us. There is no way of doing accessory gearbox maintenance on this engine without removing it from the aircraft and it needed to be done in the engine shop - so there was no economic means to mitigate the accelerated wear problem. Thus the engines came out at 110% - not because they wouldn't go to 120% but because it was not economical to do so.

Maintenance is a tricky business to get it right - and yes there are lots of shysters out there.

Please don't lump us all together in the "EVIL NECESSARY" bin. Some of us can actually save you money!!!


Stay safe,

Mx

[Colonel Sanders]

.

[SeptRepair]

I had an old boss, when I was a young apprentice, who would say sarcastically after an aircraft came back with a snag fresh after an inspection " nothing like a little maintenance to make the aircraft serviceable" How true it is/was.

[GA MX Trainer Dude]

Colonel

Ok, but if that's the case, why does TC insist upon
50 hour checks for training aircraft? And why do
they have to have the interiors torn out three times
a year?!

Well that would be because Transport Canada a long time ago decided that the manufacturer of the aeronautical device who had specific maintenance instructions that they had in place to provide continued airworthiness were in fact the ones "In the know" and that they would mandate those standards as the MINIMUM standards to be maintained.

This is why you will still see 50 hour inspections for small aircraft as that is what the system looks at.

Sorry if this bothers you - but don't blame me for something TC does. Blame the manufacturers for what they do!!!

I think you are asserting that no one at TC has industry
experience from the last 50 years, which confuses me.

I know you are easily confused - but you really need to work on your reading comprehension.

At no point in time have I ever mentioned that TC folks don't have experience - in fact I even made reference to a simple change that TC did a while back with regards to "On Condition" maintenance for private aircraft.

What part of the following is not clear??

Even TC recognizes the changes and went to "On Condition" for certain things on private aircraft.

Stay safe

Mx

[YYCAME]

It is hard to imagine 'howls from the maintenance personal' over having to do less checks and being able to get rid of unnecessary maintenance. Now howls from the producers of products like Icex I can believe

But seriously, everyone knows there always defects that can be found, at least in commercial aviation. But the degree to which you go looking for them depends greatly on the time available for the check, hanger space availability, etc and while a cargo pit might really need 3 days of work it is highly unlikely the 'defects' will be discovered until heavy check. So you could say that heavy checks cause a large number of furnishings defects or more likely people are naturally lazy and happy to postpone a defect until it is necessary to actually sign for it.

[Bede]

for the last 50 plus years the industry has adopted newer ways of doing things

Ok, but if that's the case, why does TC insist upon
50 hour checks for training aircraft? And why do
they have to have the interiors torn out three times
a year?!

I think you are asserting that no one at TC has industry
experience from the last 50 years, which confuses me.

I think they insist on that because that is what the manufacturer recommends. TC will give you approval for another maintenance schedule though if you can justify it. You have to be in their good books of course.

I used to run a small FTU as the CFI and PRM. I got in the habit of submitting a revised maintenance schedule to TC every 6 months or so. I was able to get most of the 50hr stuff checked on the 100hr, most of the out of phase items on an annual basis. I almost got approval to do the "rip the plane interior apart" on an annual basis but it got kiboshed at the last minute. My eventual goal was to have everything checked annually and deal with the rest as it comes.

Originally, we did Cessna's progressive maintenance plan, but that is a huge amount of wasted maintenance. AME's generally can't predict that something will fail soon, so you still have off sched maintenance. Plus you're paying for a guy to pull crap apart every 50 hours instead of every 200 hours.

[Bede]

GA MX Trainer Dude,

Excellent post. Can you tell me what type of operation and aircraft types and fleet size you were running?

[torquey401]

+1 what Bede said. Excellent post GMTD.

[GA MX Trainer Dude]

Bede

Sorry for the delay.

The 1830 engine analysis was with a fleet of 5 DC-3s - sked runs, charter, and a couple of dedicated cargo tramp freighters and later with a fleet of PBY5 and 6 aircraft - 6 or 7 of those - fire suppression and charter.

The component analysis was with a mixed fleet of PA31-300, 310, 350 and Cessna 401 aircraft - about 20 aircraft for different customers. Mostly charter other than the 401s that were mostly sked.

I have actually had 2 P&W 1830 pack up on the install test run and another on the initial test flight. To be fair they were both from a rather crappy overhaul shop that used to be in the Peg - but thankfully is no more. All of their engines leaked from the day they were installed until the day they came off. The bean counters had to learn the lesson on "Cheaper is not always better"!!

The other fleet of small aircraft had a mixed bag of overhaul shops providing components - one in YVR and another in YEG were so bad that we had a troubleshooting chart made up that the first step was to verify if the component was from either of these 2 organizations and if so - the next step was "Replace with serviceable unit from a reputable company".

It really doesn't make the maintenance department look very good when a newly installed turbocharger packs it in on the runup because it was never balanced in the overhaul shop. I as the DOM would get chewed out regularly by owners when things like this happened - even though they bought the damn thing to begin with.

And of course the other side of the coin when something is running well - giving good service - yet has a requirement to be removed, and you just know the replacement will not even be close to the same quality.

So like the Colonel I also think that "Too Much" maintenance can be detrimental to reliability and safety.

The key activity here has to be "Appropriate Maintenance".

Stay safe,

Mx

[david_351]

I agree that snags often arise immiedietly following an inspection, where I work we have many different aircraft types from King Airs to transport category planes, and often after a scheduled check there will be a few snags the next flight day, and often related to systems that needed to be disturbed for the check. But at the end of the day, some of the things we have found during these checks, that needed immediate attention are worth finding for the minor snags it induces the next flight day. Manufacturers and regulatory bodies put out inspection limits because things needed to be inspected. Sometimes you don't find anything, and sometimes you find a heavily corroded main spar on a wet wing commuter aircraft.

That being said, perhaps for the private owner the inspection criteria may be a little overboard, but at the end of the day, if I owned an aircraft that I flew family and friends around in, I would like the piece of mind that everything is Tyne way it should be.

[Colonel Sanders]

.

[Pop n Fresh]

I would like the peace of mind

Buy an aircraft with 10TT and sell it when it has 1000TT.

More expensive to lease or buy?

There are parts you don't mess with but there are consumables that you would be better off to replace more often that required. The trick is knowing what is what.

[david_351]

I would like the peace of mind

Buy an aircraft with 100TT and sell it when it has 1000TT.

I guess, but the average private owner likely doesn't have the budget for such a new aircraft. At the end of the day, there are always going to be private aircraft owners, and the planes they own are always going to need maintenance, some of which will require a logbook entry by an AME.

Granted there is the Owner Maintenance category, which is a good option for mechanically inclined owners, as long as they never intend to sell there plane, as it's quite hard to sell a plane in the owner maintenance category. I noticed a post about owner maintenance above. If your interested in learning about it feel free to pm me. I teach a few classes a year to local owners who wish to go that route. I charge $100/ person for a 3 day course, where I cover things like navigating your way threw the maintenance manual, I provide a list of basic tools to buy, and where to get stuff cheap(aircraft spruce) for specialized tools and hardware. I go over the pro's and con's of operating in that category, and I show owners how to do things like check compressions, I wrote a 125 page manual covering troubleshooting techniques from everything from power plant, to simple 12V dc troubleshooting, to flight controls, corrosion prevention, when and brakes, fuel systems etc. I show people how to make sense of wiring diagrams and the like. I also cover a few other things.

You can PM me if you have any questions about the owner maintenance program. I personally think it's a decent option for mechanically inclined people like Colonel, as long as you don't intend to re-sell the aircraft for anywhere near what a similar aircraft would sell for that is not owner maintained.

[GA MX Trainer Dude]

Buy an aircraft with 100TT and sell it when it has 1000TT.

Even then you are not 100% positive that you don't have problems.

I did the first 100hr inspection on a brand new Cessna 185 - both upper strut bolts had no washers or nuts!!!

Of course if I believed that since it was brand new that I didn't have to even look at it then the outcome down the road might have been very different.

For what it is worth - the bolts had not migrated in that period and since they are in shear there would have been no danger until they did.

I also did an inspection on a Cessna 172 that had just been rebuilt after a crash into a swamp in Saskaskabush. Found fouled controls - 1 full wrap - so the controls still operated correctly and the center rudder attach bracket broken - so much for the credibility of that organization and individuals.

When the CARs and the Airworthiness manual first came out I ended up in Ottawa for a national conference. During this conference Transport Canada announced they were doing away with the independent inspection requirement. When announced you could hear a pin drop in the lecture hall. Transport guy then explained "Even with the process - aircraft are still crashing due to miss-rigged and cross control issues". A stunned group of us sat there for a second and then a lone voice from one of the helicopter operators in the back of the room said "What about all the ones it catches"?

Long and the short of it all came down to the fact that legal had an issue with how to attach blame/fault/negligence when there was more than one person involved. They were willing to "Throw out the baby with the bathwater" just to make it easy for legal to apply blame. They worked around it with the wording for the inspection and the person doing the work/initial certification is the one who is responsible - the independent is just a part of that process.

Maintenance is not infallible - and when people are involved - mistakes and errors will occur. The end result of not having any maintenance is not something that we would be very comfortable with - although I have worked with a few operators that would have liked to try it.

Like it or not - maintenance needs to be done.

Stay safe,

Mx

[Colonel Sanders]

.

[GyvAir]

Some degree of preventative maintenance is good for just about every machine ever made. Unfortunately, it takes years to figure out how much maintenance that is, especially as the goalposts tend to keep moving.
First off, it can take years for a mechanic to get a general feel for what is reasonable and beneficial maintenance and how to perform it with minimum wear and tear to the aircraft. Some never get it.
It can take years again at a company or individual level to determine what degree of preventative maintenance all the different parts of a particular aircraft model in the fleet actually require.
Then, when that aircraft is put into a different environment, on a different mission, ages for a few decades, or even gets a different crew, the requirements are going to change again. There are no cut and dried answers to what appropriate maintenance intervals, requirements and methods should be. Lots of what the manufacturers and TC ask for is just plain silly - most of the time it's gross overkill for a given airframe, yet occasionally it doesn't go far enough.

I agree that the 100-1000 hours of the life of an aircraft is probably about the safest and trouble free it’s going be. So long as it’s been through a decent hundred hour check by someone who wasn’t part of the assembly or post assembly inspection team. A brand new aircraft has just gone through the most intensive maintenance (assembly) that it likely ever will. Hopefully 100 hours of shake down followed by a good independent inspection will result in a good aircraft for some time to come.

[david_351]

maintenance needs to be done

Sure - for stuff that is broken.

Serviceable stuff does not need to be unnecessarily
taken apart - and possibly put together incorrectly.

Even if it is put together correctly, maintenance still
wears stuff out.

Old hardware gets more and more maintenance until
it's eventually totally worn out and is discarded and
needs to be replaced with new.

The aircraft manufacturer makes the maintenance schedule for a reason. I know you hate maintenance, I've read your posts. We all know you can repair your own lawnmower, good for you by the way, your family is probably very proud, but in the aviation world, like it or hate it maintenance schedules are here to stay.

[brownbear]

Any extension to a maintenance interval or change isn't always about increasing reliability. Its spending less money. Everything is about money.

On large aircraft they are constantly pushing the limits and seeing what they can get away with to reduce costs. Sure and not affect safety negatively.

Taking apart large amounts of components/wires/structure to access maintenance points is going to have implications. Doing complete and thorough testing after is the prevention of inflight failures after. Small planes aside, following all and complete maintenance manual instructions is supposed to limit exposure to these failures. They are onerous to comply with. If you work for anyone less than the military you will find yourself on a deadline without all the "specialty" tools listed and what appears to be a simple task, but requires a month of reading and should have had a production plan. Even the most simple task of filling oil, might have 10 pages or more of MM reading to follow.

Maintenance on smaller planes like Cessna's is set to the lowest common denominator. The hardest used, most likely to fail scenario. Overkill for many, required for some.

It should also be noted some planes are just too damm old. You can't even move a connector to the side without a subsequent failure. But you still got to look at the structure for cracks and the cables for frays..

[iflyforpie]

The aircraft manufacturer makes the maintenance schedule for a reason.

Yes.... a couple of them in fact. To reduce their liabilities and to make their older aircraft uneconomical to maintain.

It's a good thing that based on operator experience we can extend intervals if we have demonstrated it will not incur greater risk.

Also, we can reduce risk by not doing maintenance as much.... not leaving opportunities for tools to be misplaced, fasteners to be forgotten, or something that needs to be kludged back together because it was torn apart 5000 times and the manufacturer wants $1000 for a replacement.

[CID]

Wow...talk about conspiracy theories! Aircraft maintenance isn't just dreamed up in a board room. Maintenance procedures and intervals are subject to a well defined process. The regulator(s) sometimes mandates a more conservative schedule before F and R testing can allow for changes to inspection times. And yes, that sometimes comes from in-service experience. Keep in mind that just because one operator manages to extend overhaul times or adjust the maintenance schedule, it's not automatically available for other operators.

Maintenance schedules are made to account for a wide range of maintenance skill. If an operator can prove they are competent they can get all sorts of breaks. Consider ETOPS. Different levels are granted only to operators that can demonstrate the prescribe reliability through operations and maintenance.

If you are experiencing issues following an inspection, its much more productive to concentrate on the facility that did the maintenance, not the OEM and the prescribed inspections. You have a shitty AME.

[brownbear]

one thing people are forgetting here is a large part of maintenance is "inspection". without it cable come apart, electrical fires happen from chaffed wires and so on.

A few snags caused by inspection is the price for the greater good of the inspection. Can things be over inspected sure.

Like CID said above, it is up to the AME to ensure the least impact occurs. And they follow the MM to ensure the tests are done so the faults are not found in flight.

[david_351]

I understand maintenance is a pain in the ass for owners, and I feel for them because they put alot of there hard earned money into getting there flying lisence, buying there aircraft etc, and thats why when I perform maintenance for private owners, I do it at a very reasonable price, which I wont advertise or Ill get flamed. I have no problem with owners wanting to help out on an annual or engine change or whatever, and Ill deduct there work from the total cost.

The way I would look at maintenance schedules is sort of like auto/home insurance. You can do inspections the entire life of the aircraft and never find anything. Just like I could pay insurance on all my cars and my two homes for my whole life and, knock on wood, nothing ever happens. If nothing happens I would have spent 100s of thousands on nothing. However if, say my renters somehow burn my rental home down, and I dont have insurance, Im out 300 Gs. Same with your airplane, if once, someone finds something on a scheduled inspection that has the potential to bring down the aircraft, then I guess its worth it. Thats how I see it.