Interesting Video on Approaches to Troubleshooting

[Administrator]

[YOUTUBE]ic5R4C5HRUg[/YOUTUBE]

[Al Schober]

I'd say step #1 is knowing how something is 'supposed' to work, then you can get into why it doesn't work that way.
Oh yeah, nice lathe!

[Administrator]

Personally, I like Rule # 1. Example: When the engine is sputtering and losing power, take 15 seconds to loosen the cap on the deck fill, to see if you're fighting a vacuum.

Regarding knowing how things work before you start, I think that's covered somewhat in Rule # 3, which I loosely translate as RTFM. More knowledge is always better, I guess, but I think you can do an awful lot of good work on coil-related problems without understanding the principles of induction.

Just my personal two cents. YMMV.

Bill

[Al Schober]

Re: the coil. I spent hours trying to figure out how coil systems work - which was NOT the way I thought they did. I knew the primary coil went from + to -, but the secondary (high voltage side) had me stumped. I thought it went from the post to the case, then grounded to the block. Only continuity I could get from the post was to the - connection (higher resistance to the + connection). Then I learned that the return path for the spark was through the points (and the condenser). Eureka!

[joe_db]

My number 1 rule: Don't fix more than one thing at once.
"I replaced the distributor, carb, exhaust, and manifold and the engine still acts up" Well now you possibly screwed up 4 more things along with the original problem

Number 2 rule: Don't guess, measure. I went absolutely nuts with a fuel feed issue and I *never* would have found it without vacuum gauges on both sides of the filter.

[Administrator]

This has the beginnings of an excellent thread.

More thoughts?

Bill

[Administrator]

I wish I had the smarts to develop a model which integrates the probability of something happening with the effort required to identify and remediate.

Tom/Joe: Do pilots have something akin to this?

Bill

[joe_db]

The Zen Method of A4 Maintenance:
I had an odd issue with intermittent roughness and stumbling. I just could not figure it out.
I decided to just watch the engine run and pass my hands over and around it, feeling for anything like a leak or hot spot. Back near the aft starboard side I got quite a shock
After I recovered I moved my hand back there and got another bad shock while not touching anything
Turned out a pinhole leak in the water hose leading from the pump was spraying a very fine mist that was hitting the coil high tension lead that had a crack and the whole cloud of mist was charged with 20,000 volts!

[joe_db]

Originally Posted by Administrator

I wish I had the smarts to develop a model which integrates the probability of something happening with the effort required to identify and remediate.

Tom/Joe: Do pilots have something akin to this?

Bill

All kinds of pilot humor along these lines, but keep in mind unless the airplane in question is experimental we are not legally allowed to go fixing it. A big issue is communications between the pilot and mechanics.
Log entries:
Number one engine missing.
Number one engine found
Autoland extremely rough.
Autoland not installed on this aircraft

Here is a real life example:
Left Dallas after dinner for Tampa. I lost the left alternator after about 20 minutes and I can't do night-IFR with just one on our MEL. I turned around and called in for the mechanic to come out with a new alternator. He replaced it and off I went. 20 minutes later the brand new alternator failed so I turned around again
This time I told the mechanic that maybe there was a reason this kept happening and maybe we needed to check the wiring before we used up the entire storeroom's worth of alternators. Turned out a wire had chafed and was shorting out the alternator in flight, but not making contact on the ground.