Wing Pull

[GrassStripFlyBoy]

I'll be doing my first wing pulls in coming months, was wondering - for all of the focus on this being a two year ordeal, what is happening over the fleet historically that drives this frequency of inspection?

Have any repairs or concerns noted during inspection developed as part of doing these checks?

I ask this not looking to get out of doing it, I want the skill and plan to abide by the MM plan.  But I also know how companies identify failure modes, construct manuals, and things go from there - and with nearly 20 years of history now - wonder how significant this inspection is becoming from a real world risk standpoint.

The one good thing about the automotive world I come from is failure modes are classified in RPN's (risk priority numbers), which takes the Severity of defect, multiplies it by Occurrence rate, and again multiplies it by Detection potential.  This helps one to focus inspection plans on what is the most critical.  I suspect this would be a real high number on Severity, but a very low number on Occurrence.  We now have the luxury of the fleet in service time, so what's the word on the street here?

[Tom Baker]

Besides the inspection of the structure, and changing the sight tube, the other big thing is lubrication. You have steel pins in aluminum bushings. The pins and bushings need to be cleaned and re-greased. You also have the flap connection that needs greased. Then you have two stainless pins. One goes into a aluminum bushing, the other into a spherical bearing. these need cleaned and lubricated. All of these dissimilar metals need protected, and leaving them together to long can be problematic. If you would like any guidance before pulling the wing feel free to reach out.

[Jacques]

while the wings are removed, you may want to change the short fuel hoses that goes from  the wings.....

 

[Tom Baker]

31 minutes ago, Jacques said:

while the wings are removed, you may want to change the short fuel hoses that goes from  the wings.....

 

I think I am going to start doing that every other wing pull, so you don't have to pull them a year early while doing the rubber replacement. I ran into a 2006 CTSW that had never had them changed last fall.

[GrassStripFlyBoy]

46 minutes ago, Tom Baker said:

I ran into a 2006 CTSW that had never had them changed last fall.

I did some maintenance on my lawn mower this past year, an 18 year old Simplicity that is USA made premium grade, it has a fuel hose that runs about 4' from rear through the frame up to engine area.  It was so degraded the fuel was leaking through it like a sponge, the rubber was crazy soft and gummy.  This gave me new appreciation for rubber hoses and why they need to be replaced.

[GrassStripFlyBoy]

And Tom, thanks for the offer on any guidance.  As I'm planning on keeping the airplane some time, I may fabricate a cradle or sort of sling to suspend wing as well as support the flaps & ailerons, to simply side the units out of fuselage.  I'll toss whatever concoction that idea becomes up here for critique, and then share the process when time comes.

You also answered all the reasons on why this should be done, lube / corrosion protection, and I knew the hoses would be in the mix.  This is exactly why GA shops without knowledge have issues, reading the MM one would think it's the "cracks and debonding" trail to run down, and there is so much more that is not mentioned.

 

[Runtoeat]

Hi Darrell.  Phil and I have developed a "system" for wing removal.  Give Phil or me a call when you're going to do your wings and we will try to stop by your field to give you some help if you would like.

[Roger Lee]

It says at 2 years OR the first 100 hrs. after that. For most that would mean 3 years.

Wing pulls are fairly easy and one person can do it, but two make it a little easier. If anyone has any questions on how you're welcome to give me a call

[Tom Baker]

8 hours ago, Roger Lee said:

It says at 2 years OR the first 100 hrs. after that. For most that would mean 3 years.

Wing pulls are fairly easy and one person can do it, but two make it a little easier. If anyone has any questions on how you're welcome to give me a call

Roger, I remember when you thought it was just every 600 hours and I pointed out that it was also every two years. Your quote on what it says in the MM is not quite right. What it says is, "Check each 600 hours or at the next 100 hrs inspection after 2 years, whichever occurs first.". We don't do 100 hour inspections like they do in Germany, we do condition inspections. The manual is set up the way it is because of how they tax aircraft in Germany. It would have been nice if we had a condition inspection checklist just for the US market. Since we don't do 100 hour inspections I take it as either 600 hours or two years. If you are using the airplane commercially more than 100 hours a year, then the next inspection after two years could come into play.

[Roger Lee]

But FD and Rotax both want 100 hr. inspections and in my logbook it always says I'm doing both to make sure ALL bases are covered for both inspections. Plus who says you can't do 100 hr. inspections and like you said if the plane is for hirer then they do 100 hr. inspections. And if you use the the FD checklist it list 100 hr. inspections. The FD maint. checklist doesn't say 100 hr. inspections aren't for the US and only for Germany. That might be assuming too much. The whole philosophy is to cover yourself and your client in case there is any type of incident or litigation.

[Tom Baker]

I will go through myself doing a wing pull on a CTSW. I have a buddy who comes and helps me with doing a wing pull. When he shows up he knows exactly whet we need to use, and where it needs to be located for the pull.

1. Drain the fuel. This is a good time to check the flow rate. You can do this by pinching off the line from one tank then the other. My jugs are not translucent, so I set a timer on my phone to help prevent a fuel spill. I drain from the gas collator, and turn the fuel on and off with the shut off valve.

2. Prepping for the pull. I use Gorilla tape to hold the Ailerons and flaps up. I tear off a piece about a foot long and place it perpendicular across the hinge line on top of the wing. Each aileron get one piece, and the flaps get two. In the little access panel in the wing root where the bell crank is you will need to remove the nut, washer, and bolt. Don't drop them, because they can be hard to fish back out, especially if they are stainless steel. Once the fuel has been drained you can disconnect the fuel line. Try twisting it before pulling it off. You can remove the caps from the wing pins, but do not remove the main pins!

3. Pulling the wings. I use two step ladders for wing pulls. One is a fiberglass ladder, and it was just the right height. The other is a 6' wooden ladder, and I cut it off for it to work. I have thought about making something that I could use to do the pull by myself, but I haven't tackled that job yet. I have an assortment of 1/2" and 1" pink foam blocks that go on top of the ladders to protect the wings. I place the ladders under the wing so that the edge of the top rung is under the spar and it extends aft towards the training edge of the wing. Place one under each wing. I adjust the amount of foam blocks so that there is a slight lifting force under the wing, but not to tight. With everything in place you should be able to remove the pins. If the ladders and foam is correct they should slide right out without any problems. With both pins removed you can now slide the first wing out. My helper normally has the tip and will move it fore and aft slightly while I support the root and try to slide the wing out. Once it come free slide it out about 6" and disconnect the nav light and remote compass wires for the left wing, and the pitot, AoA, and nav light wires for the right side. You can do the inspection without completely removing the wings, but I prefer to remove them and sit them on sawhorses. To do this lift the end of the wing and remove the sawhorse, then walk the wing out. Make sure the sawhorses are padded.

4. Inspection and replacement. I now change the sight tubes. If you old sight tube was kinked any at all it was to long. If it was not kinked cut you new sight tube to the exact same length. This is not one of these places where a little longer is better. Inspect the fuel bulkhead for leaks. Clean all of the pins, bushings, and the two bearings and re lubricate. Don't overdue the lubrication. Inspect the structure. While the wings are off I also lube the rollers for the aileron push pull tube. To do this remove the tape that is keeping the flap from flopping down, and find the plastic plug in the flap well. Remove the plug. I use a AA Maglite wit ha string tied onto the bottom cap. This can be placed in the wing through the small hole so you can see what's going on. The string is so you don't lose it in the wing. Using Inox wit ha long straw guided with a lone wire I direct the Inox onto the rollers. If you didn't destroy the plastic plug put it back in place, otherwise you can cover the hole with Bowles tape.

Hint: While the wings are removed you can flip them over clean and wax the bottom of the wings. It is much easier than while they are installed.

5. Re-installing the wings. Once your inspection and lubrication are completed you can reinstall the wings. Lift the wings and walk the spar stubs back inside the fuselage, until they are about 6" away. Reconnect the wires, pitot, and AoA. Make sure the pitot and AoA tubes do not interfere with the aileron push tube on the right side. Once everything is hooked up slide the first wing back into place. You will have to support the wing root and guide the two small pins back into the fuselage. Make sure the spherical bearing is turned correctly for the pin to go in. Make sure you don't pinch any wires, because this can cause issues when trying to insert the main pins. Adjust the ladders and foam blocks so the main pin holes are lined up. You can stick your finger in and feel or look from the front of the airplane. If the holes are lined up the pins should slide in easily. The left wing tip lines up the right hole and vice versa. Once the pins are slid back in place you can relax. 

6. Reconnect everything. Reinstall the caps on the wing pins. They are torqued to 17 foot pounds. Replace the aileron bolt, washer, and install a new nut. They should torque to 90 inch pounds, but it is hard to get a torque wrench in there. You can move the control stick from side to side to aid with getting the rods back in place. Once the first aileron is connected remove the tape from that aileron, otherwise you wont be able to get the other side connected. Once the second side is connected you can go ahead and remove all of the tape. Reconnect the fuel lines. When putting fuel back in the airplane I normally mark the sight tubes at 5 gallons. Check for fuel leaks as soon as you start adding fuel.

7. Record the inspection in the aircraft records.

Notes, on some early CTSW's a few airplanes and some slight fore and aft movement on the wingtips because the pins in the end of the wings were not firmly seated against the bushing and bearing in the fuselage. If you have this there should be a shim, most likely the front pins. Sometimes they can fall off when you remove the wing. I have had to make some before, hand lapped to the exact thickness.

If anyone has any questions post then up. If anybody sees a mistake in my description please let me know.

[Tom Baker]

11 minutes ago, Roger Lee said:

But FD and Rotax both want 100 hr. inspections and in my logbook it always says I'm doing both to make sure ALL bases are covered for both inspections. Plus who says you can't do 100 hr. inspections and like you said if the plane is for hirer then they do 100 hr. inspections. And if you use the the FD checklist it list 100 hr. inspections. The FD maint. checklist doesn't say 100 hr. inspections aren't for the US and only for Germany. That might be assuming too much. The whole philosophy is to cover yourself and your client in case there is any type of incident or litigation.

Roger, Flight Design and Rotax are not the ones who govern our aircraft, that duty falls on the FAA. For a SLSA aircraft there is only one inspection, and that is a condition inspection. I use the complete Flight design 100 hour/annual inspection checklist for every inspection, and sign it off as a condition inspection. For Rotax I use the 100 hr/ annual inspection checklist. I sign the engine logbook that the engine has been inspected in accordance with the Rotax 100 hour/annual inspection checklist as part of the aircraft condition inspection. If a private owner flies more than 100 hours a year they are still only required by regulation to do the condition inspection every 12 calendar months. If the airplane is flown commercially more than 100 hours a year it gets a condition inspection at 100 hours, following the same checklist. The only difference between this and a standard category airplane is the condition inspection that is done because of 100 hours of operation also resets the 12 calendar months.

Regarding the checklist, I used to help in the Flight Design booth at Sebring and Oshkosh, so I had opportunities to visit with the engineers from time to time. Since the US only has condition inspections I ask why both 100 hour and annual inspections were listed in the manual, and wouldn't it be simpler to just have one inspection since they are basically the same anyway. That is when they explained the taxing issue in Germany, and that the manual was likely not going to be re-written. They said to use both columns of the checklist for a condition inspection, and that is what I do 

[GrassStripFlyBoy]

22 hours ago, Runtoeat said:

we will try to stop by your field to give you some help if you would like.

Thanks much Dick, likewise I'm only a hop away if you you need an extra hand (or eye) on something.

Tom - really appreciate the detailed process and tips, another nugget in the Forum data base here.

On the 2 years / or within 100 hours after two years topic - I think one can argue that both ways.  It does not state every two years, then period.  And we don't have to do 100 hour "inspections".  If you asked 10 lawyers there would probably be two camps and not a definitive answer.   My take is focused on doing whatever this maintenance is correctly process wise, as it more PM on corrosion / lube, and not "oh my gosh - the wing is about to fall off", I don't think it really matters.  And the aspect of hose change is a biggie, fortunately my sight tubes look dandy.

What if one does 100 hour inspections?  I'm clear we don't have to, but nothing stating we can't do them.  I did one last year, had my fresh cert from FAA and worked the MM checklist.  My plane had never flown 100+ hours a year prior to me, so the log book got the first 100 hour entry.  I doubt I'll keep to doing them, but as I've not hit 200 hours (winter slows me down a lot), I can claim I'm in the 100 inspection window and compliment to MM.   

This is the take why I say a lawyer might argue within 100 hours is legit.  At time of 2 years punting this to 100 hour window, the 100 hour inspection is not due yet, so one could "intend" to do one, but then never hit the 100 hour mark having to complete it, and then hey - we're now due at the 3 year annual mark.  I would not stake much on this argument, if the airplane flew over 100 hours a year any point in the past, and didn't get the 100 hour checklist completed, and the same mechanic is doing all of them - that argument is shot.  As I'm the mechanic, the owner, and the pilot - all three of us agree! 

[Roger Lee]

Tom:

"both 100 hour and annual inspections were listed in the manual, and wouldn't it be simpler to just have one inspection since they are basically the same anyway.".

Exactly and this is why my opening logbook entry is like this. I cover all bases for any argument legal, FD or other aircraft company, FAA or insurance company. I did a research project back in 2007. It got the FAA and other organizations involved and it was about documentation and job completeness. It was an eye opener for what these people thought of most mechanic's works. I sent a couple dozen logbook entries including mine and mechanic's ideas on how they work on LSA to these people. Many logbook entries and work was deemed very disappointing to the group.

"In accordance with the Flight Design and Rotax maintenance manuals this aircraft was inspected for its 100 hr. and annual condition inspection".

This is why I also use the Rotax and FD checklist and annotate anything I touch, tweak, torque fix or change in the margins and give both checklist to the owners. After 30 years of going to court and watching many people get burned to the ground, get suspended or lose their jobs by lawyers you only have one defence. Good documentation that COVERS ALL AVENUES of your procedures. I never once got toasted and many cases got won or dismissed on my documentation. The things pilots and mechanics should fear the most is not crashing, but lawyers, court, FAA and insurance companies.

Cover all your bases and everyone else's and not just what you perceive, but what all other agencies perceive. What we perceive at times is below average. Many times I do things they say inspect at the 200 hr. inspection, but I do it every annual. Like a compression test. I want to see if there is a trend or I want the next mechanic to see if there is a trend before a problem gets totally out of hand. I tell all my students to strive to be a cut above average. Way too many average running around already. Look at Flying Monkey's comment on his current logbook entry. It was a great job. When I lost my engine with 833 hrs. and 6 years old (way out of warranty) I filed a CSIR with Rotax. I had to send a copy of my logbook to them.  It usually takes a month or more to get a reply. Within 48 hrs. they called my and said you never see logbooks like this. We will replace your engine. Being a cut above and complete pays off at times.

Tom you said it: The 100 hr. and annual condition are almost the same so just adding the words "100 hr." with the annual condition is just two words and doing the extra 2-3 things on the checklist puts you a cut above. Why skimp or be lulled into a false sense of security. Lawyers, FAA and insurance companies will love you.

 

[Tom Baker]

2 minutes ago, Roger Lee said:

Tom:

"both 100 hour and annual inspections were listed in the manual, and wouldn't it be simpler to just have one inspection since they are basically the same anyway.".

Exactly and this is why my opening logbook entry is like this. I cover all bases for any argument legal, FD or other aircraft company, FAA or insurance company. I did a research project back in 2007. It got the FAA and other organizations involved and it was about documentation and job completeness. It was an eye opener for what these people thought of most mechanic's works. I sent a couple dozen logbook entries including mine and mechanic's ideas on how they work on LSA to these people. Many logbook entries and work was deemed very disappointing to the group.

"In accordance with the Flight Design and Rotax maintenance manuals this aircraft was inspected for its 100 hr. and annual condition inspection".

This is why I also use the Rotax and FD checklist and annotate anything I touch, tweak, torque fix or change in the margins and give both checklist to the owners. After 30 years of going to court and watching many people get burned to the ground, get suspended or lose their jobs by lawyers you only have one defence. Good documentation that COVERS ALL AVENUES of your procedures. I never once got toasted and many cases got won or dismissed on my documentation. The things pilots and mechanics should fear the most is not crashing, but lawyers, court, FAA and insurance companies.

Cover all your bases and everyone else's and not just what you perceive, but what all other agencies perceive. What we perceive at times is below average. Many times I do things they say inspect at the 200 hr. inspection, but I do it every annual. Like a compression test. I want to see if there is a trend or I want the next mechanic to see if there is a trend before a problem gets totally out of hand. I tell all my students to strive to be a cut above average. Way too many average running around already. Look at Flying Monkey's comment on his current logbook entry. It was a great job. When I lost my engine with 833 hrs. and 6 years old (way out of warranty) I filed a CSIR with Rotax. I had to send a copy of my logbook to them.  It usually takes a month or more to get a reply. Within 48 hrs. they called my and said you never see logbooks like this. We will replace your engine. Being a cut above and complete pays off at times.

Tom you said it: The 100 hr. and annual condition are almost the same so just adding the words "100 hr." with the annual condition is just two words and doing the extra 2-3 things on the checklist puts you a cut above. Why skimp or be lulled into a false sense of security. Lawyers, FAA and insurance companies will love you.

 

Roger, are you saying that doing the wing inspection every two year instead of pushing it out to three years is not a cut above average? Is doing the wing inspection every two years instead of pushing it out skimping? I have a question for you, you had a CTSW in the shop for a condition inspection and wing pull on April 1, 2019, a year later the airplane was in and you did a condition inspection on April 14, 2020, and you have it in the shop for a condition inspection today, is the wing pull due?

[Roger Lee]

"Roger, are you saying that doing the wing inspection every two year instead of pushing it out to three years is not a cut above average?"

Not at all. Do it either way. I'm just talking about 100 hr., annuals and language and interpretations of all that.

" you had a CTSW in the shop for a condition inspection and wing pull on April 1, 2019, a year later the airplane was in and you did a condition inspection on April 14, 2020, and you have it in the shop for a condition inspection today, is the wing pull due?"

It's whatever you're comfortable with because of the language and interpretations of such. Not even the authorities seem to agree. That said if I thought the wings needed some attention I'd pull them anytime. It isn't hard and doesn't even take that long.

 

Just like TBO. Some shops and FD want engines replaced or overhauled at 2K hrs. or they won't work on it, but there are two letters and the last sentence in the FAR's out that say otherwise.

Which one do you go with? Up to you. Just like you said Rotax or FD doesn't set the rules the FAA does, but some shops and Mfg's want the TBO done.

You get to choose.

[Tom Baker]

59 minutes ago, Roger Lee said:

" you had a CTSW in the shop for a condition inspection and wing pull on April 1, 2019, a year later the airplane was in and you did a condition inspection on April 14, 2020, and you have it in the shop for a condition inspection today, is the wing pull due?"

It's whatever you're comfortable with because of the language and interpretations of such. Not even the authorities seem to agree. That said if I thought the wings needed some attention I'd pull them anytime. It isn't hard and doesn't even take that long.

It's a simple yes or no question. Is the wing pull due? You are the one who talks about litigation and being on the witness stand. pretend I am a lawyer, and you are on the stand. I ask the question and want a yes or no answer.

[Roger Lee]

Does this mean he also only put 10 hrs. on it in two years?  

Personally and according to FAA when they looked at it I have no issue with the third annual, but I will  involve the owner in the decision. The more you take things apart that are awkward, heavy and cumbersome the more tolerances you may cause. There is nothing in writing that we don't of can't do 100 hr. inspections and so long as FD has it on the maint. checklist then who's to say we don't do them. FD never has. If you can show me a document from FD that says we do not have to do 100 hr. inspections and have them remove from their checklist to follow Rotax maint. then I may swing more one way of the other, but no document exist because that means FD takes on liability for themselves and overrides what Rotax wants too. In the FD Maint. manual on the checklist section 3.4 second paragraph it says: Inspect all systems as required in the maint. manual for Rotax engine type 912. AND it stars and singles out the 100 hr. inspection. So FD believes in 100 hr. inspections so they don't get to pick and choose which one to follow in each checklist. They say check the fuel filter every 200 hrs. They believe in 100 hr. inspections. If they want a 100 hr. in one checklist for their plane then the 100 hr. that is mentioned in the other checklist is good.

[Jim Meade]

Couple of observations from my owner's perspective.

1.  Maintenance induced failure is (MIF) real and has been verified ever since the famous WWII Waddington study.  Conclusion - doing maintenance that is not required or indicated is  increasing the probability of maintenance induced failure and is therefore irresponsible. 

https://blog.aopa.org/aopa/2014/01/14/the-waddington-effect/

https://cmapspublic.ihmc.us/rid=1HTKPYHY3-10D9MZ0-11ML/

2.  Maintenance consumes time and materials.  Performing maintenance that is not necessary is a  waste of time and money.  It is highly unlikely the mechanic is going to eat the extra time and materials, so that cost is almost certainly pushed on to the owner or operator who is responsible for seeing the maintenance done.  Would you tolerate taking your car in for an oil change and having the shop charge you for tire rotation that you did not order just because they think it's a good idea (and enjoy the extra profit)? 

3.  A mechanic's paranoia about liability is not an excuse for charging the owner for unnecessary maintenance as far as I, an owner, am concerned, especially since it increased the probability of MIF, which the owner will have to rectify probably at his expense and certainly wasting his time.  It makes one wonder where the mechanic's real emphasis lies.

The owner or operator is responsible for maintenance and the more knowledgeable they are the more likely they can give good direction to and understand the mechanic's recommendations.

 

[Tom Baker]

14 hours ago, Roger Lee said:

Does this mean he also only put 10 hrs. on it in two years?  

Personally and according to FAA when they looked at it I have no issue with the third annual, but I will  involve the owner in the decision. The more you take things apart that are awkward, heavy and cumbersome the more tolerances you may cause. There is nothing in writing that we don't of can't do 100 hr. inspections and so long as FD has it on the maint. checklist then who's to say we don't do them. FD never has. If you can show me a document from FD that says we do not have to do 100 hr. inspections and have them remove from their checklist to follow Rotax maint. then I may swing more one way of the other, but no document exist because that means FD takes on liability for themselves and overrides what Rotax wants too. In the FD Maint. manual on the checklist section 3.4 second paragraph it says: Inspect all systems as required in the maint. manual for Rotax engine type 912. AND it stars and singles out the 100 hr. inspection. So FD believes in 100 hr. inspections so they don't get to pick and choose which one to follow in each checklist. They say check the fuel filter every 200 hrs. They believe in 100 hr. inspections. If they want a 100 hr. in one checklist for their plane then the 100 hr. that is mentioned in the other checklist is good.

Roger,  You are dodging the question by trying to turn the discussion into something it is not. You are certainly welcome to do 100 hour inspection and log them as such, but for a SLSA they are not recognized by the FAA. CFR 91.327 calls for a condition inspection for a SLSA. If you are flying commercially and fly more than 100 hours in a year you are required to do an inspection every 100 hours. 91.327 and the aircraft operation limitations say this inspection must be developed by the manufacture, and approved by the FAA. I have never seen anything in writing from the FAA that they have approved any other inspection for a SLSA than a condition inspection. Besides unless you are flying more than 200 hours a year it would be an injustice to the owner by signing it off as anything other than a condition inspection since the checklist are the credentials required by the mechanic are the same. To address another comment you made, Flight Design puts an asterisk next to the engine inspections, because regardless of the frequency of regulatory inspection maintenance of the engine at these intervals are critical to the engines health and safety. 

Now back to the original question that you seem to be dodging. You are putting to much emphasis on the 100 hours. It says "100 hrs inspection". That does mean you can go 100 hour after two years, it means you need to do the wing inspection at the first inspection after two years. Since you are using the 100 hour/annual inspection checklist for the condition inspection, and as you have stated you sign it off as a 100 hour/condition inspection. In the scenario I set forth if you were signing the airplane off today and the last wing inspection was April 1, 2019 the it would be the first 100 hour inspection after two years.

[Roger Lee]

I just typed a full page response which included times and the GD thing disappeared. Not going to retype a whole page.

Bottom line I'm not dodging and you failed to give any hours in between annuals.

[Tom Baker]

2 hours ago, Roger Lee said:

I just typed a full page response which included times and the GD thing disappeared. Not going to retype a whole page.

Bottom line I'm not dodging and you failed to give any hours in between annuals.

Let's say between 40 and 60 hours, but it really doesn't matter. 

[Jim Meade]

10 hours ago, Roger Lee said:

I just typed a full page response which included times and the GD thing disappeared. Not going to retype a whole page.

Bottom line I'm not dodging and you failed to give any hours in between annuals.

We're all missing a chance to read Roger's perspective on something that could affect our wallet and our safety because the pacman ate Roger's bytes.  Our loss.  C'mon, Roger, just give us the Cliff's Notes version.  You have us on the edge of our seats, like the Carly Simon song, "Anticipation".  (My god!  Was that 40 years ago?!!  I don't know whether to smile or cry at that thought.)  Don't make us wait 40 years, Roger.  

[Tom Baker]

On 4/24/2021 at 9:01 PM, Jim Meade said:

Couple of observations from my owner's perspective.

1.  Maintenance induced failure is (MIF) real and has been verified ever since the famous WWII Waddington study.  Conclusion - doing maintenance that is not required or indicated is  increasing the probability of maintenance induced failure and is therefore irresponsible. 

https://blog.aopa.org/aopa/2014/01/14/the-waddington-effect/

https://cmapspublic.ihmc.us/rid=1HTKPYHY3-10D9MZ0-11ML/

2.  Maintenance consumes time and materials.  Performing maintenance that is not necessary is a  waste of time and money.  It is highly unlikely the mechanic is going to eat the extra time and materials, so that cost is almost certainly pushed on to the owner or operator who is responsible for seeing the maintenance done.  Would you tolerate taking your car in for an oil change and having the shop charge you for tire rotation that you did not order just because they think it's a good idea (and enjoy the extra profit)? 

3.  A mechanic's paranoia about liability is not an excuse for charging the owner for unnecessary maintenance as far as I, an owner, am concerned, especially since it increased the probability of MIF, which the owner will have to rectify probably at his expense and certainly wasting his time.  It makes one wonder where the mechanic's real emphasis lies.

The owner or operator is responsible for maintenance and the more knowledgeable they are the more likely they can give good direction to and understand the mechanic's recommendations.

 

Jim, I understand about maintenance induced failures. You may find it hard to believe, but as a mechanic I hate it it when a customer has a big bill at the end of maintenance regardless of the type airplane they are flying. 

With standard category aircraft and also experimental aircraft a mechanic has some latitude with how in-depth they need to go on an inspection. For standard category airplanes their maintenance manuals are full of extra inspections and parts replacements that they want accomplished. If an airplane is flying part 125 they are often bound to follow all of those inspections and parts replacements, but part 91 airplanes are not.

With a SLSA the way the regulations are written a mechanic does not have the same latitude. The regulations say that SLSA aircraft are to be maintained in accordance with the manufacture's maintenance manual. If the manufacture says to do a certain inspection it must be done. If they say to replace a part at xx number of hours it must be replaced. And just to be clear when I am talking about the manufacture I am talking about the aircraft manufacture, and not the manufacture of the individual components installed on the aircraft.

[Jim Meade]

Tom,

I hear what you are saying.  I guess I'm living so much in the ELSA world I was biased to that perspective when I wrote.  You are right in the SLSA world and all should heed your advice, but in my ELSA world I'm not wrong.  I stand by my comment that executing maintenance that is not called for or indicated is inappropriate.  As we know, the operating instructions (OL) templates have changed recently, thus newer ELSA are likely to have different OL than ELSA converted in the past,  so the mechanic has to read OL first to know what is required and what is not on each ELSA.  My CTSW OL does not have the "do as the manufacturer says" verbiage because it was converted over 10 years ago.  I should have been more explicit that I was talking about certain ELSA.