In the Taylorcraft, where excess weight was a bigger issue, I carried a couple of hand-made tools that made heavier and larger standard tools (like a three pound Crescent wrench) unnecessary. These special tools included a large spanner for the axle nut made from sheet aluminum (not a lot of torque needed), and a cut down end wrench for the spark plugs.
For standard tools, I had a light weight 1/4" drive ratchet and sockets, and one of the GearWrench quad wrenches that had 3/8, 7/16, 1/2, and 9/16 all on one ratcheting box end wrench. Realizing that the other end of the fastener needs to be held, I also carried three or four combination wrenches. A screwdriver with interchangeable hex bits and a hex to 1/4 socket adapter. Small safety wire pliers, a small plastic retractable razor knife.
A really neat little tool I found that weighed three ounces and cost $2.00 was a small low-tech ratcheting screwdriver handle with a 1/4" hex (screwdriver bit) socket on one side and a 1/4" square ratchet drive on the other. If it weren't for the fact that this cheapie tool needed 8 or 9 degrees of movement to click over, this could have replaced my nicer (and heavier) 72 tooth ratchet handle.
For non-tool repair stuff, a small bunch of Ty-Raps (zip ties), safety wire, , a small can of WD-40 spray, a small (crack cocaine sized) Ziploc bag with Lubriplate grease. A small roll of self-fusing tape(I understand this is known in the military as "F-4 Tape"), a small plastic bowl (for cleaning parts in avgas, or not losing small hardware),and a small plastic container with castle nuts and lock nuts, Cotter pins, washers, a Schrader valve and the little tool to install it, some small machine screws and P-K (sheet metal) screws, and even a couple of small AN-3 and-4 bolts.
All of this was painstakingly packed into a standard 11 or 12 inch olive green military mechanic's tool bag. I realize full well that this kit was far more than just "minimalist". But it goes without saying that if you're stuck somewhere trying to fix something, having the ability to choose between wrenches and drivers to find the right combination is worthwhile. I believe that highly experienced mechanics will agree that when you're making an emergency field repair, that's the time when you need all the help you can get, and the little things (like 72 teeth on your 1/4" ratchet) become make-or-break items.
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