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doing things that don't need to be done

scsmith

scsmith

Well Known Member
I'm most of the way through my condition inspection. This is the fifth one (flying six years). So I thought I would be extra thorough.

I pulled the wheels and cleaned and re-greased the wheel bearings. This was a waste of time. The bearings look like new. Compared to typical service exposure of auto hubs, our wheels are hardly ever used, hardly ever exposed to unpleasant environments. Wish I had not bothered.

Completely anecdotal, but I remember hearing of a study that was done by Greyhound Bus on whether it was better to periodically clean and re-grease wheel bearings, or just leave them be. The ones that were regularly cleaned and regreased had a higher failure rate. Suspected damage to grease from residue of cleaning solvents.

I pulled out my conical K&N air filter (it is in a ram-air housing similar to the Bower system but my own design, gets filtered air from the cooling inlet)
It looks like new. It is still pink from the oil saturation. I looked up on the K&N website for guidance on when we should be cleaning and re-oiling them. Some graphic pictures show when it is dirty enough to need cleaning. Mine was way cleaner than the 'clean' picture. Like I said, looks like new. Again, compared to automotive, very small environmental exposure. I even operate off of dry dirt fields occasionally. Wish I had not bothered.
 
Sometimes it's the piece of mind that makes a difference and whole heartedly, extends into each and very flight.
 
scsmith said:
I pulled the wheels and cleaned and re-greased the wheel bearings. This was a waste of time. The bearings look like new. Compared to typical service exposure of auto hubs, our wheels are hardly ever used, hardly ever exposed to unpleasant environments. Wish I had not bothered.
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I was reading a maintenance document recently which recommended re-packing wheel bearings at least every 500 taxi/runway miles. I figure that is probably 2-3 years conservatively for me.
 
re-packing= good cleaning = bad!

in today's throw-away world, few have the equipment to service things.

a proper press for 'repacking' bearings that I used in an old garage had two discs that sandwiched the bearing. grease was slowly injected from the top centre of the bearing, and the old grease & contaminants were forced out.
no solvents involved, and thus no 'de-greasing' occurs....just MORE greasing!
We often slapped a different brand or better grade of grease in the gun, and you could see the new colour oozing out of the bearing cage, so you knew you'd gotten the job done!
I agree that much of the recommended maintenance intervals need to be considered vs needless disassembly.
obviously if you get your wheels wet, dirty, and run them for hundreds of miles annually, you want to thoroughly inspect and service as needed.
 
flyboy1963 said:
obviously if you get your wheels wet, dirty, and run them for hundreds of miles annually, you want to thoroughly inspect and service as needed.
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So Vlad should repack 'em every two weeks? :D:D

It seems to me that with lighter use, hangar protection, warmer temps, no salt water exposure, etc. that a repack every 2-3 years would be sufficient. I plan on at least jacking up the wheel, making sure it rotates freely and has no play at every inspection.
 
Again an anecdotal reference... I recently pulled the wheels on a certificated aircraft, ostensibly to change the tires but also to repack the bearings. It's a good thing I did as one of the seals had cocked off to the side and was starting to get chewed up. It wasn't visible until I had the wheel completely removed. Sometimes the repacking of wheel bearings is incidental to their inspection. So far I've found that in light service like that which most of our aircraft see, every couple of years isn't a bad frequency of inspection. If a problem is once detected and corrected, the inspection frequency needs to bump up in order to provide increased vigilance to limit the possibility of recurrence.
 
Wheel bearings

I regrease only when I remove the tires to flip them or replace them. Works out to every 18 months or so. I don't clean them, just wipe off the dirty grease and add new by packing. They don't look like they need servicing but since they are out anyway I do it.

-Andy
 
simpkinsona said:
I regrease only when I remove the tires to flip them or replace them. Works out to every 18 months or so. I don't clean them, just wipe off the dirty grease and add new by packing. They don't look like they need servicing but since they are out anyway I do it.

-Andy
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me too, I just add new. no solvents.
 
"doing things that don't need to be done" WHAT!!!!!

This has to be one of the most uneducated post that I have read on this website! The one reason that we do a condition inspection on our airplanes once a year is to find something wrong! If you don't find something wrong then you are not looking hard enough! To suggest that something does not to be inspected is a complete failure on the owners part! How do you know that the wheel bearing is a condition safe for operation without pulling it? This is a total disrespect for your own and public safety. And to make the comparision of an RV to a Greyhound bus is the most ridicoulous thing that i have ever heard. What else did you just bypass on the inspection? Maybe you should hire a qualified A&P to inspect you airplane next time. I know that he or she will find something wrong with it, that will need to be corrected! I know doing wheels and brakes and repacking wheel bearings is a dirty time-consuming job. but lets move forward in aviation not backwards. Learn from other peoples mistakes and don't repeat problems that have happened in the past. And BTW! You should always, and I mean every year be "extra thorough"!!! You and your passengers life depends on it! Good day sir! :eek:
 
Working/Living Smarter

n700jl said:
This has to be one of the most uneducated post that I have read on this website! The one reason that we do a condition inspection on our airplanes once a year is to find something wrong! If you don't find something wrong then you are not looking hard enough! To suggest that something does not to be inspected is a complete failure on the owners part! How do you know that the wheel bearing is a condition safe for operation without pulling it? This is a total disrespect for your own and public safety. And to make the comparision of an RV to a Greyhound bus is the most ridicoulous thing that i have ever heard. What else did you just bypass on the inspection? Maybe you should hire a qualified A&P to inspect you airplane next time. I know that he or she will find something wrong with it, that will need to be corrected! I know doing wheels and brakes and repacking wheel bearings is a dirty time-consuming job. but lets move forward in aviation not backwards. Learn from other peoples mistakes and don't repeat problems that have happened in the past. And BTW! You should always, and I mean every year be "extra thorough"!!! You and your passengers life depends on it! Good day sir! :eek:
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Now Now, Jon,

You know Steve was not saying NOT to pack bearings, he was musing about the deeper understanding of field maintenance that sometimes works against the primary goal.

There is a deeper level of understanding and knowledge seeking of which we should all be aware.

I did a field study of rod bearing failures as the Pb/Sn (lead/tin) overlay wore through the Ni bond layer. I found that preventative bearing replacement resulted in a 5X higher bearing failure rate than leaving the suspect bearings in place. Knowing these kind of things helps us make more informed decisions. The devil is in the details.
 
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n700jl said:
This has to be one of the most uneducated post that I have read on this website! The one reason that we do a condition inspection on our airplanes once a year is to find something wrong! If you don't find something wrong then you are not looking hard enough! To suggest that something does not to be inspected is a complete failure on the owners part! How do you know that the wheel bearing is a condition safe for operation without pulling it? This is a total disrespect for your own and public safety. And to make the comparision of an RV to a Greyhound bus is the most ridicoulous thing that i have ever heard. What else did you just bypass on the inspection? Maybe you should hire a qualified A&P to inspect you airplane next time. I know that he or she will find something wrong with it, that will need to be corrected! I know doing wheels and brakes and repacking wheel bearings is a dirty time-consuming job. but lets move forward in aviation not backwards. Learn from other peoples mistakes and don't repeat problems that have happened in the past. And BTW! You should always, and I mean every year be "extra thorough"!!! You and your passengers life depends on it! Good day sir! :eek:
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lol_he_mad_486735.jpg


The notion of too much inspection resulting in early problems is well documented in numerous cases going back to WWII ... maybe further. It is something to think about.
 
ChiefPilot said:
lol_he_mad_486735.jpg


The notion of too much inspection resulting in early problems is well documented in numerous cases going back to WWII ... maybe further. It is something to think about.
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Read up on the Waddington effect!

I'm with Steve Smith on this one, less can be more!
 
Ain't the internet/forums fun?

firstly, I admit to being totally uneducated.
...part of the reason I am reading this thread to be sure!
probably 90% of the gang building and maintaining their A/B aircraft have no formal education as an A&P.

the OP, Mr. Smith clearly states......"I'm most of the way through my condition inspection. This is the fifth one (flying six years). So I thought I would be extra thorough.
I pulled the wheels and cleaned and re-greased the wheel bearings."
...so there is no 'lack of inspection' going on, more like the time proven method of SERVICING elements on a time or use basis. We change oil at 25 or 50 hours, but replace seatbelts when Annual Inspection shows wear.
What can be learned here, in my opinion, is that 'un-educated' people detaching parts and/or improperly servicing them is not without risk.
100% true that it needs to be done properly, or it IS worse than NOT doing it.
 
Waddington effect

Some clean their canopy every time before flight. I wait until it is covered with bugs before cleaning, and that goes for the wings too. My canopy is still very clear and scratch free. I believe that one can easily destroy a nice canopy by too much cleaning.
I only wash my aircraft once per year and then I wax it. We all know that water trapped in between the metal parts causes corrosion, why give corrosion extra opportunities to destroy our metal. The leading edges are cleaned when I clean the canopy.
As far as the wheel bearings, I believe the wheels need to be jacked off the ground and checked for any extra looseness, wobble, grinding noises, etc. at each annual. My first annual I found the right wheel a little loose so I did re-pack the bearings as long as I had the wheel off. I removed the left wheel and repacked it as well, I was mostly curious to see how it was holding up. I do like the peace of mind that I have new grease in the bearings and all the dirty grease pushed out. I don't like the mess on my hands so I wear rubber gloves.
 
Please read more carefully before departing the handle

Jon,
Mr. Smith is a frequent poster on this site. Having some familiarity with his thoughtful contributions over the last few years allows me to suggest that perhaps you have misread his post. He did not say anywhere that his plane doesn't need inspecting. He was simply stating that in his opinion, and from his previous experience with his plane, that the maintenance interval for the wheel bearings and air filter may be too short.

Problem solved: You don't ride with him and he won't fly over your house :)
 
Waddington effect is very interesting and give food for thought on what and when to inspect and replace.
In a nutshell, there is a failure rate for every new part that may initially be worse than the failure rate for the undisterbed part. in addition things get brocken during replacement or maintance.
On a statistical basis this would be very hard to evaluate on the small production runs of our experimental aircraft.
Proceed at your own risk.
http://livingstingy.blogspot.com/2011/03/waddington-effect.html
 
Greg Arehart said:
Bill,

What is this? Do you mean the lead/tin plating on some parts? Did you mean to use Sn (chemical symbol for tin), not Tn? Or is this a completely different part?

Greg
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Sorry Greg, you are correct, I must be losing my mind. It is tin, Sn. I'll go back and correct the post.

As you probably know, lead will migrate into the aluminum bearing material and the nickel or copper bond layer is for a barrier to prevent that migration. Fatigue strength of the aluminum is greatly reduced if the lead migrates, and the bearing will fail. Nickel was prone to skuffing with marginal lubrication i.e. during starting. After passing through the nickel layer the bearings would go a million miles. It was a 1% failure rate issue.

Thanks for the correction.
 
flyboy1963 said:
<snip> We change oil at 25 or 50 hours, but replace seatbelts when Annual Inspection shows wear.
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I am not trying to open a can of primer here, but in heavy equipment, 3 years is the life seat belts, and then they should be replaced! They have a label affixed with an expiration date. reference

Something to think about, more than bearing grease.
 
Aside from the various specifics in this thread, I for one am ECSTATIC to see the discussion. I was in the facility maintenance business for 38 yrs and saw many examples of the Waddington Effect. I have modified the annuals on my RV accordingly, but been loathe to mention it in the Forums for fear I would be castigated unmercifully. This discussion is healthy as long as folks don't get their shorts in a knot simply 'cause they disagree.
As Mike Busch has pointed out, there is a responsible level of preventive/predictive maintenance, beyond which taking stuff apart and reassembling accomplishes little - and can add risk when we think we're trying to reduce same.
Thanks to the OP for raising the topic!!
 
BillL said:
I am not trying to open a can of primer here, but in heavy equipment, 3 years is the life seat belts, and then they should be replaced! They have a label affixed with an expiration date. reference
Click to expand...
If my plane got used every day like a piece of construction equipment and was never parked inside, I'd replace the seat belts every three years too.
 
Rupester said:
Aside from the various specifics in this thread, I for one am ECSTATIC to see the discussion. I was in the facility maintenance business for 38 yrs and saw many examples of the Waddington Effect. I have modified the annuals on my RV accordingly, but been loathe to mention it in the Forums for fear I would be castigated unmercifully. This discussion is healthy as long as folks don't get their shorts in a knot simply 'cause they disagree.
As Mike Busch has pointed out, there is a responsible level of preventive/predictive maintenance, beyond which taking stuff apart and reassembling accomplishes little - and can add risk when we think we're trying to reduce same.
Thanks to the OP for raising the topic!!
Click to expand...

My feelings, exactly! After all, there are some condition inspection items that I inspect more often than annually, because after seven years and 850 hours, I have learned that they need to be looked at more often. Get to know your airplane and use common sense.
 
I'm curious on the thoughts of the individuals posting about seat belt replacement and how they treat the seat belts in their daily driver? Considering the seat belt has the exact same purpose in both your car and airplane, keep you in your seat during an accident or incident.

Given we spend a whole lot more time in our cars the odds are higher we will need to rely on those seat belts more often.

I'm believe in the visual inspection for wear, discoloration, cuts, etc. as the basis for replacement.
 
Appropriate service intervals

Wow! First time I've been flamed on VAF:eek:
Thank you to everyone else chiming in.

To my original post, of COURSE I know why I bothered!

For my wheels, like others have described here, every year I jack them up and give them a spin, make sure there is nothing unusual, too much play, a noise, roughness or drag. I do this while I inspect the brake pads and clean the brake caliper sliding pins.

Why I bothered this year to repack the bearings is that collectively, we don't have very much data on the service life of wheel bearings in airplanes, and what an appropriate service interval should be. (I know in cars, wheel bearings often last 500,000 miles with no service). So it was worthwhile to take a look after 6 years, 360 hours, about 650 t/o-landing cycles.

My conclusion after inspection/repacking is that this was too soon. But that's OK. Good data point, and it is obviously better to do it too soon than too late.

One poster suggested an interval of 500 miles of ground roll. While my engineering judgement would say that is probably more conservative than needed, this is the KIND of service interval guidance that is most useful and beneficial to all of us.

For my air filter, again, collectively we really don't have much data on what an appropriate service interval should be. And of course this item in particular is strongly affected by the operating environment and installation details. Mine is in the hangar when not flying. But I do occasionally operate off of dusty dirt strips. So it was worthwhile to take a look after six years. I was actually thinking that I probably should have looked at this sooner. Heck, there could be a bird's nest in there!
My conclusion after inspection is that this was too soon. For my specific air filter installation, and my particular operating environment, 360 hours and 650 t/o-landing cycles and the filter looks like new. But that's OK. Good data point.

Most all of us agree that needlessly taking things apart and putting them back together is not a good practice. The problem for us, collectively, is to accumulate enough data so we have an indication of what appropriate service intervals should be.

That was the purpose of the post.
 
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curtis said:
I'm curious on the thoughts of the individuals posting about seat belt replacement and how they treat the seat belts in their daily driver? Considering the seat belt has the exact same purpose in both your car and airplane, keep you in your seat during an accident or incident.

Given we spend a whole lot more time in our cars the odds are higher we will need to rely on those seat belts more often.

I'm believe in the visual inspection for wear, discoloration, cuts, etc. as the basis for replacement.
Click to expand...

I do the same visual inspection and replaced my belts sometime between 12 and 14 years of service. I believe they were still good and safe but at time of removal they were starting to discolor and had some wear. While the airplane is down for maintenance, there was no excuse not to send the belt out to be re-webbed.
 
With a few notable exceptions ;) in the post department, this has been great discussion. Thanks, Steve, for starting the thread!

I only check and repack wheel bearings when I flip tires or install new ones. I pulled my K&N cone-style air filter at 200 hrs and it looked like the day I installed it. It will likely be another 200hrs before I pull it again.
 
Rupester said:
I only check and repack wheel bearings when I flip tires or install new ones.
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This is a fantastic suggestion. When you pull the wheels and split the rims open, you risk exposing the bearings to contaminants anyway, so that is a great time to repack them.

I probably have another 75 hrs on my current (original) tires. I'll repack then.

Thanks!
 
Correct me if I'm wrong but I do believe everyone has a operating limitations attached to their airworthiness certificates that require the aircraft be inspected in accordance with the scope and detail of 14 CFR Part 43 appendix "D". This includes "(7) Wheels?for cracks, defects, and condition of bearings." It's hard to inspect bearings without removing and cleaning them first. Obviously you'll have to re-grease them. If you don't hold a mechanics certificate (A&P), what makes you think you know more than 100 years of aircraft maintenance experience. I've been a A&P with IA for more than 20 years and I would never sign off a condition inspection or annual inspection without completing the entire inspection. I owe that to myself and the passengers that rely on my expertise. Oh yea, you don't have that 20 years of experience...stick to the checklist....inspect your aircraft whether it's type certificated or amateur built.
 
Interesting discussion of the Waddington effect and I appreciated the link to the article provided by the earlier poster. I noted in particular that when the RAF began extending the time between scheduled maintenance it was despite the "howls of protest" from the maintenance folks. I noted that the same thing took place in this thread.

Here is a link to a spreadsheet that can be used to schedule checklist items based upon hourly limits (or limits on days) between inspections. Essentially it crosses things off the list if the limits have not been met within a certain "cushion"

Of course, you'd be a fool to use something like this. . .and the idiot who came up with those limits certainly doesn't understand anything about airplane maintenance.

Revised_Annual_Checklist_RevB.xlsx
 
I was told that even Cessna inadvertently exposed themselves to the Waddington effect when they initially had the fuel injector nozzles cleaned and re inspection-lacquered at every annual. As I understand it they found that there were an alarming number of instances of problems after annuals that were traced to small pieces of inspection lacquer in the fuel injection port as a direct result of breaking the lacquer and removing the nozzle to inspect it. Small chunks would just fall in and that cylinder would run very lean, sometimes with damaging results. I believe they removed the item on the annual inspection checklist and basically went with some version of "if there is an egt indication of possible contamination or blockage, carefully remove clean and inspect", but it was only as necessary.
 
n700jl said:
This has to be one of the most uneducated post that I have read on this website! ...
Click to expand...

Not to be dogpiling Mr. Hubbell, but this post is a good jumping-off place for a couple of comments.

First off, that "uneducated" post was made by one _Dr._ Smith, who has a PhD in aeronautic engineering from Stanford, who has owned and operated at least six aircraft that I know of. Mr. Hubbell might also be interested to know that it was Steve who developed the wing profile used on his RV-10.

Second, I've assisted Steve on two prior annual condition inspections on this very same RV-8, where I removed the wheel bearings and found them in basically the same condition as when we originally assembled and installed them. But in order to discover that, we had to remove the wheel pants, the outboard brake pad, the axle nut, and also jack up the airplane. Oh, and we had to do all that stuff twice. That is a lot of wear and tear on fasteners and assemblies, and a lot of relatively risky futzing around.

I've discussed this general issue with Steve on several occasions in the past; and I addressed it to some degree in the inspection guidelines I wrote for HP-series homebuilt sailplanes many years ago:

Getting off-topic, there?s always the possibility of an inspection actually making an aircraft less safe than it was before, by damaging or disrupting parts or systems that were happy and functional before the inspection intruded upon them. So you must seek balance between functional inspection and disruptive intrusion.
Click to expand...

http://soaridaho.com/Schreder/Construction/Inspections/HP-RS_Annual_Inspection.htm

Thanks, Bob K.
 
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