Should we follow everything on the Maintenance Schedule?

[Tom Baker]

1 hour ago, gogogo888 said:

Nothing cheap about going above and beyond to follow all the TBO and maintenance schedule and STILL have a midflight engine failure. One would think is this cause by maintenance induced failure? 

Not a maintenance induce failure! What was the serial number of the failed engine?

[gogogo888]

1 hour ago, Tom Baker said:

Not a maintenance induce failure! What was the serial number of the failed engine?

S/N of failed engine is 5647326

[gogogo888]

3 hours ago, Jim Meade said:

I attended one of Mike Busch's weekend seminars in Rapid City, SD a dozen or so years ago.  I talked with him there and several times since, and I've followed many of his webinars and sat-in on several of his Oshkosh presentations, so to me, Mike Busch is not some unknown guy on the internet.  I've meet Tom Baker, the Gutmans, Adrain Foldan and Tom Peghiny, and Brian and Carol Carpenter and perhaps because of that have a pretty high confidence level in the competence of these people.  Other internet gurus not so much.  So, saying internet guru may be a question of perspective.

Mike Busch spends a considerable amount of his time explaining how engines work and how mechanics misunderstand that and develop ideas and shop practices that are not substantiated either by science or the regs, but rather by the mechanic's own preferences and comfort zone.

The lean-of-peak practices are one example of where engine manufacturers take a position that is not consistent with known, demonstrable facts.  Charles Lindbergh can teach how to get more range from a P-38 by LOP and be a hero, while George Braly can show how to get better engine performance and life using the same methods and be sneered at by Lycoming.

As Roger points out, liability seems to be a big issue with manufacturers and mechanics.  It is reasonable to assume that some positions taken by both have one eye on liability as well as one on airworthiness.   That can make the owner wonder if there is a conflict of interest on the part of the "expert".

As Busch points out, airlines and the military maintain airplanes based on a different set of premises than time.  Those institutions appear to use a philosophy based more on condition.  It is strange that what is the rule for airlines and the military is frowned on in general aviation.

Rotax has a rotten reputation for standing behind warranty and for the ways they distance themselves from US courts and legal remedies.  Maybe now that the Chinese are building a copy-cat engine Rotax will have to face competition for the first time and may be less rigid in their policies.

AMST and the FAA have different approaches to maintenance.  Tom Baker will correct me if I'm wrong, but my understanding is an oil hose on a Taylorcraft can be inspected on condition while the identical hose on a Rotax sold on a European LSA is maintained on a time line.

Bottom line - the main reason my airplanes are all ELSA is that I can legally, and I believe competently, maintain them with considerable more flexibility than if they were SLSA.

 

 

 

You sum it up much much better than I can.

In addition to Mike Busch. Professor Shuch in AVSport is another specialist with the Rotax 912 engine, he is a CFII and LSRM who just received a FAA Master Mechanic Award for 50 years of service to aviation safety.

Professor Shuch also says less maintenance is more. In his website he wrote:

(10) Acknowledgment:  Much of what I know about condition inspections I learned from Mike Busch, A&P/AI, founder and CEO of Savvy Aviation Inc.. I have incorporated many of Mike's recommendations into AvSport's maintenance policies. I am grateful to Mike for so willingly sharing his extensive knowledge and experience with his fellow EAA members.  

 

These people are not just some "internet expert" who doesnt want to pay for maintenance. These are credibly people saying follow exactly what the Maintenance Schedule says is a BAD IDEA!

Much like most people in here saying changing oil at 100 hour interval is a bad idea!

 

[Roger Lee]

Yes anyone can still have a failure, but you did your due diligence to properly maintain it and then you won't have to battle the FAA, the insurance company and have some defence in case their is legal litigation which there easily could be. Your only defence is doing things right and above average documentation. That is your best protection against the authorities and legal litigation. A good plaintive attorney will pull in 5 people like me and my documentation and then proceed to eat the mechanic and pilot alive for failing best practice maint. and documentation. Remember the courts basically say if it isn't documented you didn't do it.

 

Plus you can get help from Rotax if it was an engine failure. My 2006 CYSW had a 6 year 833 hour engine failure do to a bad lifter. I was way out of warranty. I was told to fill out a CSIR and send in my logbook. I was told it could take 1-2 months before anything was heard. In 48 hours I had a phone call and they said we never see logbook's like this. We'll pay for the engine. That was $18.K  back in my pocket. Is better than average documentation worth it????????? Worth every penny of $18.5K.

[procharger]

Where is the black gooey stuff coming from, never seen anything in mine since new.

removed a bunch of times to check for stuff never seen anything.

[procharger]

You can write anything in a log book doesn't mean it was done, hope that's not the

case. I don't trust very many people to work on my plane. To many horror stories. I think if you

do carbs. change oil 50 hrs keep an eye on everything else, hose change you should be

good to go. and BRS which is the only reason I own CT.

[Warmi]

I feel your pain , I had  3 relatively major maintenance induced failures :

• Carb fuel line leaking fuel due to a badly installed clamp. This happened a few months after 2017 5 year rubber replacement. Detected during takeoff due to strong fuel smell - was lucky nothing happened.
• Debris in the carb bowl a few flight hours after basic carb maintenance - engine would not go past 4000 rpm on the takeoff roll. Happened on the ground, right after applying full power - lucky again.
• Quick oil drain valve installed with minimal clearance over the muffler. It would end up hitting the muffler on engine start - eventually it failed, thankfully gradually with progressive oil leak so I was able to catch it on time and on the ground.

I had one failure related to lack of maintenance , namely the front gear leg eventually failed at the weld point due to vibration at take off  - there was a bolt that was supposed to be checked at every annual and adjusted to make sure that there was no vertical play in the front leg....

All in all it ended up costing me , I think , something like $2k total to cover for all these issues but I was extremely lucky in all these cases  -  nothing was damaged or bent and nobody was hurt..

Still, even with all these maintenance induced issues , the solution was not to stop maintaining the plane but rather find a more competent/dedicated maintenance professional...

[gogogo888]

1 minute ago, WmInce said:

Do you subscribe to the practice of "preventative maintenance?"

The following was what I wrote on the original post. So, the answer is YES!

The most important maintenance we should do for our Rotax 912 engine is 50 hour oil change, 100 hour spark plug replacement, annual inspection and the 1000 hour gear box inspection(Kerry in Lockwood is the expert, he does nothing but gearboxes 40 hours a week) 

[Jim Meade]

Preventive maintenance includes the concept of condition based maintenance.  Condition based maintenance is not part of corrective maintenance.  Corrective maintenance means fixing something that is defective and none of us proposes letting a component become defective before repairing it.  Corrective maintenance includes the concept that the risk of failure is acceptable and the consequences  manageable.  That is seldom the case in aviation.

One does not wait for an oil hose to fail, rather, one notes that it is getting soft, discolored, distended, collapsing or has other indication which shows the  hose is less able to perform it's function than deemed acceptable and the risk of failure is increasing and at some point the risk is deemed unacceptable.

This is the same concept where a person changes tires not based on time but based on the tread reaching the wear bars.  You don't have to change tires then but most of us would agree it is prudent.  I have wagon tires that are 25 years old.  We might also change tires based on checking, uneven wear, out-of-balance or other indications of condition even though tire is still working.

I have a glider that called for the tires to be changed at 250 operating hours although the tires appeared to be brand new.  This is an example of where tire wear has little to do with how many hours the glider flew.  Many gliders fly for 3-6 hours on one flight. Some fly 250 hours in 2 years and some may take 10 years.   Some may land on grass.  It's difficult for me to understand how operating hours has anything to do with tire safety.  There was no reference to the number of landings or to the total life of the tire.

Preventative maintenance includes condition based maintenance and does not include the concept of operating until failure or until an unacceptable risk of failure.

[Jim Meade]

BTW, top the OP, I think everything on the maintenance schedule should be given due consideration.  I do not advocate ignoring the existence of an entry.  That does not mean I believe it is necessary or appropriate to do everything on the maintenance schedule as written.  I also believe we should, as considerations indicate, include more items than are on the maintenance schedule or at an earlier or more frequent time than scheduled.  This is based on the same reasoning that has us changing oil and air filters more often if we drive our Jeep in dusty conditions often.

[FastEddieB]

About NGK spark plug gaskets...

I did not know they were technically one use items.

That would seem to lead to going through a lot of plugs. I mean, any time you want to do a compression check “mid plug” as it were, that would mean buying at least 4. And another one every time you pull #1 to find TDC if needed. Not the end of the world at $3 a plug, but these plugs are used for many applications and I’ve never heard of automatically tossing them every time they’re removed. 

I’m aware other crush washers are also technically one use items, but legions of folks do reuse them regularly on oil drain plugs and the like without obvious disastrous results. I also can’t envision any effect on plug torque between a fresh and a used gasket.

Can the gaskets be purchased separately? I know on the massive electrode plugs used in Continentals and Lycomings one can purchase a whole bag of gaskets for a reasonable price, and back then I did most often replace them during annuals.

[Tom Baker]

51 minutes ago, FastEddieB said:

About NGK spark plug gaskets...

I did not know they were technically one use items.

That would seem to lead to going through a lot of plugs. I mean, any time you want to do a compression check “mid plug” as it were, that would mean buying at least 4. And another one every time you pull #1 to find TDC if needed. Not the end of the world at $3 a plug, but these plugs are used for many applications and I’ve never heard of automatically tossing them every time they’re removed. 

I’m aware other crush washers are also technically one use items, but legions of folks do reuse them regularly on oil drain plugs and the like without obvious disastrous results. I also can’t envision any effect on plug torque between a fresh and a used gasket.

Can the gaskets be purchased separately? I know on the massive electrode plugs used in Continentals and Lycomings one can purchase a whole bag of gaskets for a reasonable price, and back then I did most often replace them during annuals.

I am not aware of being able to buy replacement gaskets for the NGK plugs. While it may not effect the actual torque of the plug it will effect the effectiveness of the gasket. With new plugs once the gasket comes in contact with the cylinder it takes about 5/8 of a turn to get torque. During this time the gasket is compressing and forming to the cylinder to make the seal. Once the gasket is compressed it may not make a proper seal the next time. When I do maintenance where I will be running the engine and doing checks I will reuse the plugs, and then change them out last thing when I'm done. I normally replace plugs at a condition inspection regardless of time on the plugs.

For traditional aircraft engines the sparkplug gaskets are supposed to be annealed every time they are removed. I think this is a carry over from the radial engine days. It is easier to just replace the gaskets.

[Tom Baker]

14 hours ago, procharger said:

Where is the black gooey stuff coming from, never seen anything in mine since new.

removed a bunch of times to check for stuff never seen anything.

The residue is in the top part of the carb where the piston moves up and down. It comes from fuel residue and the aluminum part rubbing together. Also it you are running 100LL the dye from the fuel can become sticky.

[GrassStripFlyBoy]

On the topic of retorquing plugs, this came up during the 16hr class with Rainbow, as well as topic around someone using CHT leads on plugs with questions around placement as well as how do these impact gaskets situation.

Regarding using plugs again, it was stated a study (who and when - don't recall) was performed on torques and removal forces.  In this study it was observed that the plug is clocked further on each reinstall, and if proper torque is applied it is acceptable to reuse them ~ 3 times before the dynamic of crush / deformation / resulting anti-torque becomes less predictable.  That seems like a fair idea to me.  Thankfully plugs are cheap and this is an easy decision coupled with my flying ~ 100 hours year, just change them with compression check being time to swap anyways.

Doubt many people are using CHT probes under plugs, that answer was retain the spark plug gasket and slip these on, torque the same as normal.

 

[gogogo888]

1 hour ago, GrassStripFlyBoy said:

On the topic of retorquing plugs, this came up during the 16hr class with Rainbow, as well as topic around someone using CHT leads on plugs with questions around placement as well as how do these impact gaskets situation.

Regarding using plugs again, it was stated a study (who and when - don't recall) was performed on torques and removal forces.  In this study it was observed that the plug is clocked further on each reinstall, and if proper torque is applied it is acceptable to reuse them ~ 3 times before the dynamic of crush / deformation / resulting anti-torque becomes less predictable.  That seems like a fair idea to me.  Thankfully plugs are cheap and this is an easy decision coupled with my flying ~ 100 hours year, just change them with compression check being time to swap anyways.

Doubt many people are using CHT probes under plugs, that answer was retain the spark plug gasket and slip these on, torque the same as normal.

 

I took the plugs off to do a borescope few days ago, was thinking about replacing them because of what Tom said.

I will keep them in the engine until they are timed out.

This just show how much confusions are out there:

Assuming the plane uses auto gas 100%

1) - Rotax says to take the plugs out to clean them at 100 hours and put them back in and replace them at 200 hours.

(People in here says to replace them at 100 hour, if you take them out before 100 hr, replace them because the gasket won’t fit. Rotax never said this)

2) - Rotax says to change oil every 100 hour

(People in here says to change it at 50 hours, Rotax never said this)

3) - Rotax says cruising at 4,300 RPM is completely ok.

(People in here says cruising at 4,300 RPM will damage the crankshaft, you must cruise at 5,000 RPM, again, Rotax never said this)

4) - People says, if we don’t follow the Rotax maintenance manual and engine shut down mid flight, you won’t get reimbursed from Rotax. But according to the last 3 points, we are NOT following the maintenance manual. 

Even worst, the previous owner of my plane follow all the recommendations and have spent tens of thousands of dollar doing all these maintenance and STILL had an mid air engine failure and they were NOT reimbursed for the engine.

[Roger Lee]

Go to a Rotax school. Learn tried and true best maint. practices on a Rotax engine since 1990 from real people who have been there and done that. 

Some of these things are like one pilot told me and was proud of it that he left oil in an engine for 20 years and it was okay. 

There are several things no Rotax service center does. The 200 hr. plug comment in the manual has been there for a a decade or two, but I have never seen anyone follow that and it isn't taught in school. Letting to oil go to 100 hrs. I haven't seen either, but I'm sure there are some people out there that do this somewhere. Syncing the carbs at 2500 rpm has been in the manuals too forever, but few do that. The manuals get an update only once a year. For instance if you use the new manit. checklist they forgot to include the gearbox friction torque check. Another oops that needs to be corrected.

None of this is hard. Just do the right thing and if you do anything else just make sure it's a step above and not below. I have never understood why people spend so much time and effort to get out of things or try to justify their action or inaction. It's just as easy to do the right thing instead of screwing it up and having to pay later.

 

[Tom Baker]

1 hour ago, gogogo888 said:

This just show how much confusions are out there:

Assuming the plane uses auto gas 100%

1) - Rotax says to take the plugs out to clean them at 100 hours and put them back in and replace them at 200 hours.

(People in here says to replace them at 100 hour, if you take them out before 100 hr, replace them because the gasket won’t fit. Rotax never said this)

The plug gaskets being a one time use, and to just replace the sparkplug was taught to me during my Rotax training, with a Rotax certified instructor. Now you do have to realize things do change. For example Rotax uses a different plug now on newer engines. It cost about 7 times more than the old NGK plugs. I will not be swapping these out every time they are removed. Also you are not supposed to change the gap on the new plugs.  Did you ever happen to think that the manual may have been updated to reflect the new sparkplugs?

[procharger]

Spark plugs I have replaced 1000's use to race bikes, check plugs for right jet and

color many times over same gasket same plug put it back in and go racing over and

over. Same with Ct pull plugs check for color and compression and reinstall keep on

flying. Color of plugs can tell you a lot if you know what to look for. As for carb. sync.

I focus on idle mainly I will do run up and see where it is at 5000 if its real close

i move on. My engine is smooth as glass at idle 1700 and below even at lower

rpms still purrs like a kitten. I don't change it unless engine tells me to which is rare.

[gogogo888]

23 hours ago, Tom Baker said:

The plug gaskets being a one time use, and to just replace the sparkplug was taught to me during my Rotax training, with a Rotax certified instructor. Now you do have to realize things do change. For example Rotax uses a different plug now on newer engines. It cost about 7 times more than the old NGK plugs. I will not be swapping these out every time they are removed. Also you are not supposed to change the gap on the new plugs.  Did you ever happen to think that the manual may have been updated to reflect the new sparkplugs?

 

On 10/20/2020 at 2:22 PM, Roger Lee said:

The 200 hr. plug comment in the manual has been there for a a decade or two

 

[gogogo888]

Thanks for everyone that have contributed to this discussion. 

 

This is what I've learned.

A lot of the recommendations(ex. 50 hr oil change(auto gas), 100 hr spark plug change(auto gas)) are based on personal preference, anecdotal evidence and what was taught by other people. Which is valid and it makes you feel better about your airplane not falling out of the sky.

On 10/20/2020 at 2:22 PM, Roger Lee said:

Go to a Rotax school. Learn tried and true best maint. practices on a Rotax engine since 1990 from real people who have been there and done that. 

23 hours ago, Tom Baker said:

The plug gaskets being a one time use, and to just replace the sparkplug was taught to me during my Rotax training,

 

 

On the other hand, the real scientific fact and engineering data comes from Rotax's own maintenance manual, which calls for 100 hr oil change(auto gas), 50 hr oil change (100LL) and 200 hr spark plug change(auto gas) 100 hr spark plug change(100LL)

On 10/19/2020 at 1:34 AM, Roger Lee said:

With more than 50K engines and almost 5.5 million run hours I think these Mfg's are far and ahead of anyone here.

 

If it makes you feel better to change oil at 50 hr(auto gas), feel free to do it, but understand that, there is no real scientific fact behind it, it is all based on anecdotal evidence.

If you want to protect yourself and your mechanic from law suit, feel free to follow the scientific fact on the Rotax maintenance manual and change your oil at 100 hr(auto), 50 hr(100LL).

On 10/19/2020 at 5:48 PM, Roger Lee said:

Yes anyone can still have a failure, but you did your due diligence to properly maintain it and then you won't have to battle the FAA, the insurance company and have some defence in case their is legal litigation which there easily could be.

 

Also understand that, doing all the extra maintenance does not protect you from engine failure, as Roger himself have had engine failure before, all those extra effort he puts in does not prevent the engine from failing.

On 10/19/2020 at 5:48 PM, Roger Lee said:

My 2006 CYSW had a 6 year 833 hour engine failure do to a bad lifter.

 

Isnt the whole point of preventative maintenance is to prevent the engine from failing? If doing extra maintenance does not prevent the engine from failing but increase the chances of maintenance induced accident. Why do it?

So, my personal conclusion is, if it makes me feel better, I will change oil at 50 hours(auto gas). If I want to follow scientific fact and also protect myself and my mechanic from lawsuit, I will follow what the Rotax maintenance manual says and change my oil at 100 hours(auto gas).

 

 

 

 

 

[Roger Lee]

The oil in your engine is like the blood in your body. Disease it (failure to change the oil) and the body dies prematurely. Once diseased then there is no oops do overs.

The electrical system is like your nervous system in your body. Mistreat it and suffer many year and premature issues as you get older.

 

And the less is more in maint. comment is extremely subjective. Where and when does the average individual that knows little about the engine make that call where to draw the line. Hec half the A&P's on Rotax engine don't do the right thing or even know where a checklist is. Things may sound good on paper, but in real life fall short especially when you let a human make the decision. 

[gogogo888]

1 hour ago, Roger Lee said:

The oil in your engine is like the blood in your body. Disease it (failure to change the oil) and the body dies prematurely. Once diseased then there is no oops do overs.

The electrical system is like your nervous system in your body. Mistreat it and suffer many year and premature issues as you get older.

You are 100% correct and I completely agree, so I follow the most updated scientific fact on the Rotax's maintenance manual(Jan 2020) and change oil at 100 hour interval and spark plugs at 200 hour interval.

I’m not saying to change oil every 28 years. I’m saying to follow the latest and greatest scientific fact on the Rotax maintenance manual.

Please share any links or report that says otherwise.

[FlyingMonkey]

Maintenance-induced failures are a thing, for sure.  However, let's compare the incidence of failures caused by maintenance to those caused by lack of maintenance.  I think you'll find the latter outnumber the former about 10:1 if not more.  Don't throw the baby out with the bath water.

Is there some reasonable room for "interpretation" or possibly changing intervals based on observation and experience?  Sure.  But good or bad, if you have an SLSA you are largely constrained to what the manufacturer (of the airframe, not components) dictates.  If they have a required maintenance interval associated with a component you are pretty much bound to it.  If you want to play around with maintenance intervals and develop your own schedules, that is what ELSA excels at.

Since I converted to ELSA there are a (very) few things I have changed in my maintenance.  For example, The fuel filter behind the instrument panel now gets disassembled and inspected every other annual instead of every annual.  This is based on my observation and experience over six years that the fuel filter never has more than a sand grain or two in it on inspection.  I've concluded that messing with it every 12 months is probably worse than letting it be for 24 months.

But things like that are the exception rather than the rule.  I still do oil changes religiously every 50hrs, more often if I burn significant 100LL.  I still pull the wings, inspect the spars, and replace the sight tubes every other annual.  My airplane is running like a top, but I still plan to pull my gearbox at the suggested interval 190hrs from now when it hits 1000hrs.  The cost of the inspection is not worth risking the cost of a gearbox failure, and I don't have the experience to know the pros and cons of deferring it. 

The factory maintenance intervals are designed to be conservative.  That's not a bad thing and IMO they should be heeded unless you have a lot of information to make a conclusion based on real information and data and not just "but it's just such a pain in my butt to do it."

 

 

[Tom Baker]

Gogogo, you also have to understand that the advice Roger, myself, and others are giving is based on how the average owner uses their airplane. Also remember that the 100 hour section on the inspection checklist is also to be used for the annual condition inspection, so how much a person flies their airplane annually will effect the maintenance schedule. If you only fly 20 hours in a year you still have to change the oil.

On sparkplugs why not run them for 400 hours, because that is what the checklist calls for? I suspect that number is for the new Rotax plugs, and not the NGK plugs.

[GlennM]

There is nothing wrong with following the current Rotax maintance manual for life limitations and maintenance periods. 

Replacing earlier than their limit is opening yourself up to maintenance-induced failure, as you mention.  But, people do this for other reasons like expediency; "while they are at it", or costs.  It is probably cheaper to replace the spark plug than inspect and clean it if you are paying someone to inspect and clean.

Replacing later than their limit would be running an experiment for how much later. Which brings up condition-based maintenance:

To be safe about condition-based maintenance you need a specification and limitations to determine condition.  Rotax does not provide this, so making up your own limits is, again, experimenting.  If you like to experiment,  you are welcome in the E-LSA category.

The previous engine failure, you mention, obviously had something going wrong that could not be seen and had nothing to do with spark plug or oil changes. Most maintenance or condition inspections do not get inside the engine to inspect for damage, wear, or fatigue.

From a purely anecdotal perspective on the oil change, 100 hours at 112 knots typical cruise is almost 13k miles.  Many cars are set up for 10k to 12k miles per oil change, which takes between 150 and 300 hours to accomplish, typically. I don't see that being outside convention.  For years, everyone said you had to change your oil at 3k miles.  This was good advertising by the oil change places and the oil companies to get you to spend money.  You will still find people doing it, but there is no technical basis for doing so.

Mike Busch mentions most of the aircraft engines fail to make TBO due to corrosion (just sitting).  You fly so much, I would not worry about it or going to the Rotax limits.