The tools I use most are a small ratchet screwdriver with PH and flat bits, three open ended spanners and a 1/4 drive set from 5/16 to 9/16 SAE and a small adjustable or Knipex. Plus a rechargeable LED head torch and some rags. Maybe 2 kg in total.
If I need any other tools away from home, I’ll beg, buy or borrow them.
I just carry the tools for the repairs where I also carry the spare parts with me. E.g. I don’t carry spark plugs so I don’t carry a nut for them – because I assume if I find someone to provide me with a spark plug I would also find one (the same person probably) who has the tools.
I used to think exactly that – until I got stuck at San Sebastian and found that an aviation spark plug driver is not available from any motoring store.
It was a bunged-up spark plug. Bottom one, of course. 2005. It happened only once again, and I departed with it. But I did an airborne mag check soon afterwards… was ok (of course 
). I used to know a pilot who departed with at least one bunged-up plug on every flight, but that was a twin.
I carry a couple of spark plugs, only.
Ultranomad wrote:
Not all of them are created equal, but fortunately, there is a clear champion, Knipex 86 03 series (several sizes available):
Ultranomad made a great suggestion. I did buy the 3 smaller sizes and now came the real test. I had to undo the fitting from the oxygen bottle and it did work very well. It took me a few seconds longer than a traditional spanner but I would not have dared to mess up the precious fitting with any cheap adjustable tool. The 8603 did the work and made no damage at all.
The ultimate aircraft owner gift: a set of titanium spanners
About £200 for a set of five.
The harder bit will be finding a titanium torque wrench, titanium wirelocking pliers, etc.
Wow 
I only carry along a combined screw driver, that has lots of bits inside the grip, which comes as a rubber-and-plastic shell. It’s enough to open or tighten normal screws. I even quit to carry my litre of oil with me, because I never ever had to refill on tour. You can fill 12 Quarts of oil into the engine, and it would still be totally happy on 2.8 Quarts. I use about 0.1 quart per hour.
I don’t carry anything more, but am astouned about this thread. I was in need of tools once, it was in Biarritz. A very friendly police officer came to check what I’m doing, and he was in fact interested to see it with open cowling. And when I explained in broken french that a screw came loose and I need to fix it, he took me to the local shop, asked for the two spanners I needed and I could fix my problem on the apron. We only had to delay the flight plan to continue into Spain for 30 minutes
I just don’t see the point of taking along a lot of weight. And in addition, on tour I never have less than 4 POB plus baggage.
Never had a problem with spark plugs, but maybe that’s because I run LOP? Anyway, after a bit of thinking, one spark plug could be an item worthwhile to take it along on tour.
And I will also check the Knipex variants. Haven’t seen it before, but that could get handy.
But I never go without my dip stick!!!
The harder bit will be finding a titanium torque wrench, titanium wirelocking pliers, etc.
Well, and not destroying the precious titanium tools by contaminating them with the hundreds of things that destroy titanium – cadmium, car body polish, looking at them the wrong way, etc.
You mean tightening a cadmium plated nut with a titanium spanner destroys the spanner?
I haven’t actually tried it but I guess so. The inverse problem (using cadmium plated tools on titanium) was a big problem for the SR-71. They had a special plant for removing the plating from off-the-shelf wrenches etc. In the same book is the story of a crew-chief who decided to smarten up “his” SR-71 by polishing the leading edges with some car polish product. They had to replace the leading edges, at an expense you can imagine.
I doubt these tools are pure Ti. It will be some alloy.
Cadmium is banned in Europe by Brussels but a) there are lots of exemptions e.g. aviation and b) these spanners (Motion Pro mostly on the Ebay ones) are US made.
Funnily enough all those I can see are metric. They are aimed at the motorcycle market.
Most of this stuff is really expensive – example. £3500 for a big spanner set
