Owner Maintenance Philosophy

Owner Maintenance Philosophy

  • Replace Components "On Condition"

    Votes: 30 85.7%

  • Replace Components "On Time"

    Votes: 5 14.3%
  • Total voters
    35
flight2000

flight2000

Pre-takeoff checklist
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Oct 4, 2009
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Toledo, OH
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flight2000
Okay, so I've recently been engaged in a back and forth discussion on aircraft maintenance and the thought process on when to change out major components (i.e. starts, alternators, etc.). This is strictly for part 91 Ops.

From what I've seen there appears to be two camps:
1. Change out "on Condition"
2. Change out/Overhaul based on time/hours
​
I fall into the change out "on condition" crowd and I use a spreadsheet to track the last time something was changed and continually update my spreadsheet with the current tach time, which updates the component times. When something gets to be old (based on calendar time or tach time), I just monitor it for any unusual signs pointing towards the time to make the call for overhaul or replacement.

Some owners have said they replace strictly on time and have no issues throwing out a part that is operating perfectly in the name of reliability. The ones that have opposed my theory are usually also the type that gives a "blank check" to the FBO and thinks that new parts equates to better dispatch reliability. :dunno:

My argument is that even new parts can suffer from infant mortality, so why throw out something that is still working perfectly just because it's old.

Just curious what some other owners out there think.

Brian
 
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It depends. If the part is cheap and easy to replace on a time schedule, then I'll probably do that.

On my car I have a habit of replacing belts and hoses at the 4 or 5 year mark, and saving those belts and hoses. Having a belt or hose fail while on a trip is kind of annoying, especially if the part has to be shipped in. By replacing the belt/hoses on such a schedule (at my convenience) I reduce the probably of a failure while driving and also have a ready spare in the vehicle.
 
I am in the "on condition" camp. This doesn't necessarily mean waiting until failure to replace a part, but it does mean waiting until you have good reason to replace it. For me, it comes down to building enough redundancy into the aircraft I fly that a single failure doesn't present a big problem, and saving money.

Most of the "on time" people I know do as you describe - effectively write a blank check. I'm not convinced they have better dispatch reliability. It seems they do spend more money on their aircraft, but still have problems.
 
I'm an "on condition" guy, but I do know folks who have a split philosophy -- most things are changed "on condition," but some are changed "on time," particularly vacuum pumps in planes with vacuum AI/HI and no backup system (other than an electric T&B/TC) flown hard IFR.
 
Part of this involves understanding which components are truly critical and which you can surivive if they fail, as well as knowing which components give adequate warning of failure.

For example, dry vacuum pumps don't give you any warning signs -- they just suddenly fail (sheared shaft or vane disintegration). However, vacuum pump failure isn't going to kill you VFR, and shouldn't kill you IFR, so even for an IFR pilot if you maintain your skills and/or have adequate backups, you don't need to change the vacuum pump until it fails. Nevertheless, some pilots with no backups still change them at the manufacturer-recommended 500 hours anyway, viewing the $200 or so for the job as "cheap insurance." In that case, an "on time" replacement may make sense for those individuals.

OTOH, engines, for the most part, do give you warning signs in the form of changes in temperatures, power output, oil analysis, metal in the filter, etc., so you usually have adequate warning of impending trouble and can take appropriate action. The failures which come without warning (like a manufacturing flaw in the crankshaft) usually happen early, anyway, so there's not much you can do to prevent that -- the new engine is more likely to fail that way than the old one which has served you well for 2000 hours (if it was going to fail like that, it would have done so long ago). Since replacing an engine is two orders of magnitude more expensive than changing a vacuum pump, "on condition" engine overhauls usually make more sense than "on time."
 
wabower said:
Do you follow the stuff that Mike Busch lectures and writes about?
Click to expand...

Who....never heard of him... :rofl:

That is the spark that ignited the debate... ;) It got so bad (mostly from one arrogant individual), Mike showed up and registered on the forum to help clear up the misinformation this dude was arguing.

Brian
 
Ron Levy said:
I'm an "on condition" guy, but I do know folks who have a split philosophy -- most things are changed "on condition," but some are changed "on time," particularly vacuum pumps in planes with vacuum AI/HI and no backup system (other than an electric T&B/TC) flown hard IFR.
Click to expand...

Yep, I just had a working vacuum pump replaced. It had over 800 hours, and I didn't feel comfortable flying blind behind it. I will overhaul or replace anything that is critical to IFR safety by time.
Other things are on condition only. Belts, hoses, tires, engine, etc.
 
Right now, considering how I earn my living, it is a money based decision when the issue comes up. I try to keep my airplane current and in compliance with all the regs., but that is not always possible. If it is something that is going to effect airworthiness at a time when I can't afford to solve the problem correctly, my airplane sits until I can.

I guess I am in both camps now.

John
 
I'm firmly in the 'it depends' camp. Replacing an alternator belt every couple of years at annual when thre prop is off beats unexpected failure in flight.

But I wouldn't OH, say, gear retract cylinders except on condition.

via Tapatalk
 
I agree on the belts and hoses. Those will have a time limit due to dry rotting, but probably would also qualify as an on condition replacement based on what they look like at teh time of inspection. Some climates are nicer than others when it comes to gaskets and hoses.

Has anyone ever redone all of the electrical wiring in order to check that it conforms to 2011 standards? I had a harness (if you could call it that) fray and caused a break in the current being sent to my battery. Took awhile to find it, but made me wonder what the rest of the wiring looks like. Some is new after obvious upgrades to the avionics, but just how much of the rest is original is a question that just might scare the crap out of me if we start digging... :hairraise:

Brian
 
As a mechanic I always list what recommended replacements are due or coming up soon on the aircraft I'm inspecting or when performing a pre-purchase. My wife has a lot of input into the maintenance program for our aircraft ( everything is done). Another reason I list the recommended items is in the case of an accident. The courts feel that we need to let the owner know and decide what will be done. With the PA-46 aircraft, due items can really bite you at the time of sale too. Believe me the buyer will bring it up and want to bring the price down.

Infant mortality is a problem on new and overhauled parts. I do have to agree with my wife on changing the parts on schedule on my planes to reduce the chances of getting stuck somewhere.

Kevin
 
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