Light Aircraft Costs Schedule 5 v.s. Manufacturer Maintenance Schedules etc.

[Creampuff]

Final post on this thread.

I'm struck by the irony that I'm advocating for evidence-based maintenance requirements, using data from the single largest piston fleet on the planet, rather than robotic compliance with asinine law, and some people are arguing against that. It's depressing to say it, but I'm completely unsurprised that GA in Australia is in the state it's in.

For those who consider manufacturers' manuals to be the collected wisdom of lessons learnt by people who know best, I note this from CASA's Discussion Paper on ageing aircraft management.

[S]ome Manufacturer’s Schedules are documents which are frozen in time from when the aircraft was first actually produced. In some cases these schedules have not been legally required to be updated to reflect the aircraft ageing well beyond its original design life assumptions, even though these assumptions may have been reached many decades ago.

And you know what they say about assumptions...

stevo200: Find an engineer with a deep understanding and long experience in the maintenance of the type and model of aircraft you have/are considering buying. Get him or her to explain what's actually involved in maintaining the aircraft properly. Good luck.

[stevo200]

I'm probably the furthest thing from an expert in this field, being still a uni student and not knowing much about the industry until a few months ago before starting some research on it all.

But after reading all your comments I can see both sides of the story from an objective view. I think both sides have their fair points they are bringing across and in a way you are both right.

Creampuff, your argument seems to be that although there are these regulations saying you need to replace these components, in actual fact most of these components will last much longer than the manufacturers recommendation, and that the over-servicing of some areas, such as the injectors, can "potentially" introduce more problems than the it solves.

That is perfectly understandable and correct. But I think the point you are arguing about is yes this may be correct mechanically, but what yr right is trying to say is that is it really acceptable from a safety and liability point of view. Yes, a component may last 5 times its recommended replacement time 9 times out of 10. Yes 90% of vac pumps will last over 1000hrs. Yes injectors dont need inspection/cleaning as regularly with modern engines. But what happens when that 1 out of 10 times something fails? Who is responsible for the deaths that could occur from a failure mid flight? The manufacturer does not want that responsibility and it is there duty to ensure that does not occur.

That is why they appear to"over-maintain" certain areas, is to ensure that the 1 in 10 chance of failure does not occur. They do not want any failure rates, they do not want any accidents involving their aircraft and they do not want any lives lost due to a failure of a component they designed. Therefore their servicing intervals have a large factor of safety included to ensure the least liability towards them in the event a failure.

Yes this may increase costs at the expense of the consumer, but at the end of the day that is what they feel is necessary to ensure they have covered themselves from a mechanical failure. It is all a part of risk management, with a very conservative approach being taken. Replacement of parts may be completed much earlier than required but the risk of a failure is dramatically minimised than running the component close to the average failure time.

Running a component beyond its service life may be alright, it may not. There may be an issue, there may not. You may be over-servicing, you may not. It seems like a lot of the maintenance issues within the industry are based on maybes. Something may be able to operate for much longer than its replacement interval, but is it able to operate safely with the lowest possible chance of failure. And is running the risk that something "should" be alright to operate past its service life really an acceptable chance to take when you have other peoples lives in your hands? Fair enough if you are flying only yourself and you can take that chance with your own life, but can you really risk other peoples lives and take responsibility for that 1% chance that something might fail for operating past its service life?

With respect to the cleaning of injectors introducing more problems than it solves, it again is down to the manufacturer both taking responsibility for their designed aircraft, and also shedding responsibility as the component is now within their calculated acceptable factor of safety limits and the responsibility is now on the mechanic to ensure he takes responsibility for completing the work correctly without any issues. The inspection removes the liability of they "should" be alright. Cleaning the injectors every 500 hours means you know they were fully operational 500 hours ago, not they were fine last overhaul which is 2000 hours ago. There could be a 2% chance they could fail within 2000 hours compared to a 0.02% chance they could fail within 500 hours and these regular inspections remove the liability associated with the unknowns of when a component will actually fail from the manufacturer.

So after all that, I think the main thing im trying to get at is yes Creampuff you are 100% right in the fact that a lot of things can operate for much longer than specified, but someone needs to take responsibility for those few times that something fails early, and these early service intervals are the manufacturer taking responsibility to ensure there is no mechanical failure leading to potential accidents from there design and recommendation point.

Thats just how I see it anyway.

[Perspective]

As with any argument Creamie, it is an injustice to only quote figures or statistics selectively so as to try to prove your point.
I have changed Vac pumps below the 1000Hr mark due to sheared drive shafts, worn Vanes. That doesn't mean they all will and Vice Versa.
Why did it fail? Environment, Cleaning agents or over zealous use of degreasers in the vicinity, FOD, turning backwards...
Would it have been good to change the Drive at 6 years as recommended?
would it have made a difference.
You and I know mag timing can change by a degree or Two in 100Hrs of use.
Was it a new mag bedding in,
Is the capacitor flogged out creating heat down the arm melting the cam lifter?
Also saying every time something is changed it will introduce a fault is not correct, and the Data will tell you that.


Human Factors is a reality of course. Aircraft Maintenance is preventative Maintenance, and by default so is probably most things that get any level of maintenance, just focused on more with aircraft.


I understand perfectly where you are coming from, and you are not human if you don't make mistakes.


But there are too many variables in operating environments, Machine operation, FOD, Engineer experience level's, Knowledge, and component operating life expectancy to simply say, well I have seen this or that run for a lot longer than the book allows me to operate it, so I will,
because for every example you give me of extended operations, Several people out there will have the opposite example.


The focus seems to be toward Vac pumps and Injectors. But what about something of a more critical nature.
Would you be happy to let a Governor run well past its Overhaul period,
as I have seen these fail also,
How about a Fuel injection unit, a propeller, does the tendency to leave something to continue operating relate to the perceived risk of failure?


The equipment available to the cockpit these days is vastly improved on when the aircraft was built in most cases.
You have access to a lot of information in regards to engine parameters now, which is great for trouble shooting and engine monitoring.


But that wont stop a failure of a component past its TBO, with all your vast experience you must have had many trouble free hours of maintenance carried out on your aircraft, and carried out by your self.


So let it be, intrusion does not have to equal fault. Components should not be allowed to run until failure.
I cant maintain to your experiences, which may differ greatly from someone else's, in regards to components the limits are clearly defined,
I can evaluate many other facets of aircraft defects and wear, using my experience and wear limits provided.


Other than that you follow the Reg's, regardless of how silly you may think they are, because ultimately, and this is quite important, I cant use you or your experiences as my reference to the Regulator!
Yes shocking, I know, but if I have to justify myself to someone as to why I let something run on, I can's say AMM CreamPuff R1.

[yr right]

I've stated my what I've done on this site enough. I'm
Happy to stand by my qualifications and record. You can read into that what ever you like.
You see I don't really care what people on this site may or may not think of myself. I have enough people that know me personally and what my commitment to safety and engineering I have. I have been in a court by casa try to make me out to be not a good lame only to have them walk out with egg on there face and me make them look like fools.

I stand by I won't give someone an aircraft I will not fly in myself. However there a lot of pilots I would not

[stevo200]

And the other thing, im not saying the manufactures schedules are right at all, im just trying to see it from their point of view.

I think the manufactures schedules are well overdone and require more than is necessary, but Schedule 5 is the exact opposite offering too much flexibility for people to do the wrong thing by it.

Both I think are not really meeting the needs for real word good servicing requirements as they are both too far in each direction from what actually should be done in reality. A combination of both seems to me like the best option or possibly the introduction of new system at an intermediate of the two.

[yr right]

What people have lost is aviation works on preventive maintence and not reactive maintenance. And when you first get your lic and have to sign a document that will remain with you for up to 12 months and your reasonability you can't imagine till you have to do it.

[yr right]

Anyone that thinks there is a lot of difference between a shed 5 and manufactures is deluding them selfs. You still have to do Ads sb time limited components I. Both systems. Shed 5 is just work sheet that mention everything with out being exact That's all the difference is. A good engineer knows where what and when to look regardless of ever system. This all change though with more complex aircraft but. Then aanufactures system comes to it own. As I've said before most people in GA can't afford to own and maintain there aircraft. Cost should not be considered in maintaining your aircraft to an acceptable level. That's the sad truth.
And now with lidication less and less maintence frims are willing to let things go as in the past.

[yr right]

Casa dose NOT won't GA. It's to hard to regulate. That was told to me some 15 odd years ago from an awi in Wagga

But then who wears the coat of blame if it goes wrong.

[Eddie Dean]

A combination of both seems to me like the best option or possibly the introduction of new system at an intermediate of the two.

Steve200 read the AWB (Airworthiness Bulletin) All will be revealed. It is exactly as you said.

Perspective and Yr Right have the right perspective on maintenance I would say.
Interesting that you mention the CSU issue Perspective, that was covered in the Brazier case that Creampuff alludes to. Massive over runs, but with no apparent detriment, although he was lucky to get away with the amount of items he had on over run. Read about it here if interested. Brazier and Civil Aviation Authority [2004] AATA 313 (26 March 2004)

[yr right]

And if you actually know the whole story it was what creamie wonts us to do. Go figure.
And yes I actually know the whole story not just what is in the AAT. That's not to pass any judgement on what occurred to fly boy. But to say that was the only thing that was the story would be in correct

[Perspective]

Many Thanks for the Link Eddie,
Cheers

[Eddie Dean]

Heard a little about the saga a couple of years ago, he was up against it alright, his major client owing him over 100K, 80 in the AAT transcription and no way out but to keep him flying.

[yr right]

Plus plus plus a vindictive casa awi just new to casa and making a mark. As I've said before the hardest word in aviation is NO. And who was doing the maintenance control. !!!!!

[yr right]

As i recall and if I get a chance tomo I'll check. Under the beech system afyer you do your 1st component checks you then have the option of when you do them next if they where ok at the 1at check