[RV7A Flyer]

Just received and read Mike Busch's Manifesto, an short interesting read recapping much of what he's written on-line. I look forward to the follow-on volumes.

And it did make me think about some things, so here go a couple of questions...

IF one were to apply the Reliability-Centered Maintenance (RCM) approach, what sorts of things would one do differently right off the bat? A couple of examples come to mind, tell me if I'm thinking wrongly or missing some key thing to consider:

Fuel injectors. I followed the manufacturer's instructions last year at annual, removed them (kept as sets) soaked in Hoppe's #9, etc., reinstalled/torqued to spec. What did that accomplish? GAMI spreads over the previous year never changed (about 0.1), and haven't changed since. Fuel flows at various power settings have been consistent over the entire time (which would indicate that the remote possibility of all 4 injectors getting plugged a similar amount is probably not happening). Seems to me that this might be one of those things that should *not* be done unless a GAMI sweep shows the spread changing or some other indication crops up. Right? Wrong?

Wheel bearings. I get that you should clean and repack them when changing tires and tubes, but last year when I took them out to "flip" the tires on the rims, they looked as new as the day they came out of the box, the grease was as red as it was new, no galling, etc. If one deferred this maintenance until a) changing tires or b) some indication of a bearing failing (noise, resistance, etc.), what would be incorrect about that? i.e., does cleaning and repacking them every year whether they need it or not fall into the non-RCM thinking, complete with increased failures post-PM? Just thinking out loud...

I'm not advocating one way or the other, just trying to wrap my head around what RCM *might* mean for light aircraft, and which "preventive maintenance" items might be better treated as run-to-failure or on-condition maintenance items.

Ideas welcome!

 

[az_gila]

...Wheel bearings. I get that you should clean and repack them when changing tires and tubes, but last year when I took them out to "flip" the tires on the rims, they looked as new as the day they came out of the box, the grease was as red as it was new, no galling, etc. If one deferred this maintenance until a) changing tires or b) some indication of a bearing failing (noise, resistance, etc.), what would be incorrect about that? i.e., does cleaning and repacking them every year whether they need it or not fall into the non-RCM thinking, complete with increased failures post-PM? Just thinking out loud...
.....
Ideas welcome!

Re-packing wheel bearings annually may be common practice, but not required.

My certified Tiger Maintenance Manual gets into much more detail -

1. Re-pack at 100 hours and every 500 hours after that.

2. Each annual, inspect grease for contamination and solidification.

3. Repack every 100 hours in dusty of high humidity areas.

In your case, when you saw good clean grease, these instructions would say to leave it alone...


I think a lot of the RCM stuff may be better met with using time in service as a basis, but with annual visual inspections.

 

[RV7A Flyer]

I guess I'm wondering, on the list of things that get "preventively" maintained (either at annual or on some time-based cycle), which ones might be better done on a condition basis? Obviously:

Brakes (replace when worn)
Bearings (I like the schedule you gave)

Others might include:

Fuel injectors
Magnetos (perhaps at the recommended 500 hours, but with no intervening IRAN...I know some people disassemble and inspect them at each annual? perhaps longer? or stick to opening them up every annual, for example, and checking brushes, etc.?)
Flexible hoses? (Usually what, a 7-10 year service life is recommended? Perhaps, with a few exceptions like fuel lines FF, replace only as condition indicates, say brake lines?)
Prop overhaul (who here sends theirs in at 6 years? who doesn't?)

Might there be others?

 

[Mike S]

Add me to the list of folks who have trouble with the concept of removing and cleaning/greasing bearings based on solely calendar time.

I check for lateral movement, bearing noise/roughness, and side play.

If all above is good, leave it alone IMHO.

If I ever get the extra $$ I plan to do the Anti Splat bearing mod-------bring the bearings up to current century technology.

 

[RVDan]

It think the injectors might be a good example. Since the airplane is equipped such that you can monitor GAMI spread, and assuming you do so, cleaning the injectors might not be needed until the spread was observed to increase.

On wheel bearings, I took away an interesting note from a 1970's study on auto wheel bearing failures. Nearly all failures were due either dirt introduced during repacking or inproper torque and occurred shortly after repacking. The only difference for us is that we have to disturb the bearings when changing tires and that the seals aren't as good as even older autos.