Always carry some rags and a few litres of oil...engineers are not always around to get you home..
Not always?!?
Unless things have changed significantly, in my experience, not at all unless at a home base between the hours of 7am and 4pm (which is the time you hear the tires screeching out the front gate of the airport, not the tools down time)...
As for writing up anything that is unservicable on an aircraft - CAR50 is pretty clear on that, but the lines can become a tad blurred when stuck at a remote airstrip with naught but the shade of your wing and a 250ml bottle of water to last you the next 4 hours while an engineer comes to change your busted nav light... common sense (not overly common, I know) must prevail in these circumstances - could it have broken on the way home? Certainly not if its a serious defect - Nil Comms across the desert, alternator etc...
It is essential also, to remain cognisant of the different motivations each party has in deciding an aircraft is taskworthy:
- Pilot - although it would seem obvious (complete the task, get home safe), it is amazing how often the "I have to get to the pub to catch up with the boys" type of motivation gets in the way... don't be a fool.
- Operations - are there to achieve the endstate of the client and make money for the Company. Don't begrudge them for this, but be aware that they may not see the "minor" defect in the same light as you - rather just an embuggerance that is ruining their plan...
- Engineers - although we would all like to think that "no engineer worth his salt would release an aircraft to line that wasn't taskworthy", the filter for what does and does not meet the taskworthy list may often become blurred as the day draws towards "knock off" time...
- Customer - I had many passengers in the past ask me how serious the issue was - especially if they had been paxing in GA aircraft for years prior - chances are they've seen it all before; good and bad. The adage don't die for a deadline comes to mind here...
A sound tech knowledge will save a lot of hassle in many instances as you will have a better understanding of what has gone wrong and the implications. Morale of the story is therefore (its been said many times before, but is certainly worth repeating) - pull the flight manual and read it cover to cover. Then read it again. Until you can draw every diagram and schematic and explain every system in detail from memory, you don't know enough about your machine!