Wrench Report

A well-maintained general aviation airplane is a reliable beast, able to soldier on hour after hour without complaint. Problems can and do arise, however, and a conscientious pilot should anticipate minor systems failures and other glitches that might result in a grounding far from home—perhaps even in a remote area. Carrying a basic assortment of hand tools, spare parts, and other critical supplies falls into the common sense category.

Just what to bring along remains a point of contention, however. Some pilots—you know who you are—are comfortable with nothing but a giddy optimism and a wallet full of credit cards. Others believe that a random handful of throwaway wrenches, a quart of oil, and a rusty tow bar will see them through. And then there are those who seem to lug around enough equipment to rebuild an airplane around a data plate.

The answer, of course, is a compromise. Preparing for every eventuality is an unrealistic goal, but you probably have room for the essentials needed to deal with the small fix-it jobs, temporary repairs, and safety precautions that your piston single or light twin is most likely to require on a cross-country flight. (Note: Wilderness survival gear is another topic entirely, worthy of a separate article.)

What’s that you say? You can’t touch anything because you’re not a certificated Airframe & Powerplant (A&P) mechanic? This is a popular fallacy. As a private pilot and aircraft owner, you are authorized to perform a multitude of minor repairs and other tasks; a detailed listing of these can be found under “preventative maintenance” in the federal aviation regulations (Part 43, Appendix A). And even if you have no interest in dirtying your hands, the tools and supplies you carry in the airplane will be available for a third party to use on your behalf should the need arise.

Hand tools—the basics

Professional mechanics typically buy the best tools they can afford, and so should you. What’s the difference between a good tool and piece of junk? Tools of the best brands are built to precise tolerances, resulting in a tight fit that does not mar or otherwise damage expensive, aviation-grade fasteners. They are also resistant to corrosion, heat, cold, impact, and other forms of abuse.

In the United States, a limited number of vendors dominate the high-end professional tool market. Snap-on, Mac, and Matco are all held in the highest esteem; their products are generally available through a network of independent dealers operating from their own truck-based franchises, and through the mail. Most offer Internet sales as well. It’s a good idea to inspect truck-bought tools carefully, though, as they often stay on the vehicle for months prior to sale, and are subject to significant wear and tear. Proto (Stanley) and SK tools—other top brands—are often available in auto parts stores.

A second tier of less expensive tools is easily bought retail; the most popular examples are probably the Craftsman (Sears) and Husky (Home Depot) tool lines. Availability could be their greatest attribute—these stores are just about everywhere and, in a crunch, a Craftsman socket or extension fits a Snap-on ratchet just fine. Or vice versa. Steve Ells, our other A&P-qualified editor, points out that Craftsman has broadened and fine-tuned its product line in recent years, making it suitable for virtually all aviation applications.

“This expanded line, their no-questions-asked replacement guarantee, and their affordability—especially when compared with Snap-on—make Craftsman tools an excellent choice for most,” he says.

Europe is another source of quality hand tools; Germany in particular is the home of several well-respected manufacturers. Of these, it appears that only Stahlwille has attempted to crack the U.S. aerospace market with any real enthusiasm—its representatives are regular attendees at aviation trade shows. Stahlwille combination and open-ended wrenches are significantly lighter than their U.S. equivalents, which could be an advantage where weight is critical.

Speaking of weight—try to keep your tool kit under 30 or 40 pounds unless you need it to serve as ballast. A soft-sided tool bag or plastic box is better than a metal toolbox, as it will do less damage if it gets loose in turbulence or during an incident. For years I carried a small canvas tool bag that weighed around 13 pounds fully loaded. Ells—who carries a cartilage-tearing 60 pounds of tools in his Comanche—recently shamed me into switching to a slightly larger nylon bag I bought at Home Depot. Not only does it carry more tools (20 pounds plus)—it helps keep my Husky’s tail down during three-point landings!

Choosing wisely

Plan your tool kit with specific tasks in mind, such as tire and tube replacements, oil changes, and spark plug maintenance, and you’ll be covered for most routine repairs away from your home field. Fill it with items you are likely to need and are comfortable using. A good hammer is essential. It has many uses to include driving tie-down stakes. Eight- or 12-ounce ball peen hammers are both adequate. Take along a couple of pin punches of different sizes as well: 1/8 and 3/32 sizes are small but effective.

A complete combination wrench assortment might seem essential but really isn’t, unless you’re planning a field engine overhaul. Sets of these wrenches can be extremely heavy and I’ve found that sockets (and a six-inch adjustable wrench) will suffice most of the time. Still, I carry a pair of combination wrenches—in 3/4-inch and 7/16-inch sizes—for removing and tightening spark plug leads and the small barrel nuts that go with them. The wrench sizes your particular airplane need for this application might be different, so be sure to check.

Ells prefers to carry a full set of long combination wrenches, plus a set of 30/60 open-ended wrenches. The latter have a set of jaws at 30 degrees to the centerline of the handle and the other at 60 degrees to the handle. We learned in A&P school that these “angle” wrenches are sometimes the only way to reach certain fasteners on piston engines. That theory was never tested, however. Evidently, Ells has found multiple uses for them—he describes them as the most valuable wrenches he owns.

As for sockets, 1/4-inch drive is fine for most GA applications; adapters and individual tools make a lot more sense than lugging around complete sets of 3/8-inch and (huge) 1/2-inch drive sockets. I carry two complete sets of 1/4-inch drive sockets, along with two ratchets and extensions of various sizes. This way I can anchor a nut with one set while removing a bolt with the other, as required when loosening and then refastening wheel halves during replacement of a leaky tire tube.

Sockets come in 6-point or 12-point styles; in shallow, semi-deep, and deep sizes. I prefer shallow or semi-deep 12-pointers because they’re easier to get onto a nut when clearances are tight—with airplanes they usually are. I haven’t had much use for all the deep sockets I’ve bought, although some mechanics will use them instead of a shallow socket and an extension. Universal sockets are the only way to reach some remote fasteners: I typically carry a set of six, 12-point universals (1/4 to 9/16) on a rail. A single universal adapter can work as well, provided you have enough space available at the working end. The big challenge here is not finding a tool that will fit the fastener—it’s finding a tool that will fit the fastener within the tiny workspace allotted.

Your most important socket is probably a deep 7/8-inch for removing spark plugs for cleaning or replacement. There are purpose-built spark plug sockets but any deep 7/8 works just fine. No deep 7/8-socket links directly to a 1/4-inch ratchet, however, so your best bet might be to bring along a 3/8 ratchet for the spark plug socket, along with an adapter to drive 1/4-inch sockets just in case you need the additional leverage.

A torque wrench might be considered a luxury in the field, but it’s a welcome addition if you have the room. (I once asked a mechanic how often he used a torque wrench. “Every time” was his politically correct response.) I prefer the click-type with a ratcheting head, 1/4-inch drive, 40-to-200 inch-pounds. This one is too small for spark plugs; at a minimum you’ll need a 3/8-inch drive torque wrench for those; 20-to-100 foot-pounds is a good size. A new generation of digital torque wrenches is available; these can double as spare ratchets, hammers, or pry bars after the batteries die.

Screwdrivers are another essential, and the ratcheting, removable-bit variety eliminates the need to carry a whole bag full in assorted sizes. Even so, it’s a good idea to carry medium and small-tip Phillips and flat-tip screwdrivers. The physics elude me, but a regular screwdriver will hold and turn a worn fastener when your super-cool ratcheting tool just spins in place. Some of the better screwdrivers have a 1/4-inch square drive at the base of the shank, so you can attach a wrench to help coax a reluctant machine screw into movement. Also, don’t forget to pack a 90-degree offset screwdriver. When you need this little S-shape tool, nothing else will do.

On the pliers front, you should have at least one set of quality needle-nose pliers, a set of standard six-inch pliers, duckbill pliers for twisting safety wire, a set of diagonal cutters, a set of small vice grips, and a safety wire twister that turns both left and right. At A&P school, we were instructed to fill the blade cavities of our diagonal cutters and safety wire twisters with Silicone sealant, to grip and retain errant bits of safety wire, and thus prevent foreign object damage. You don’t have to do this, but doing so is virtually guaranteed to impress the [other] tool nuts in your circle.

Odds and ends

Pack a good flashlight, preferably one with a flexible, fiber-optic extension. I picked up a Streamlight 4AA at a trade show some years ago that works well, tastes good, and lasts a long time between battery changes. A telescoping inspection mirror is good for peering into tight spots, and a magnetic pickup tool is essential for retrieving hardware that rattles to a stop somewhere deep within the darkest recesses of your lower engine compartment.

I also carry a six-inch awl for lining up fastener holes, a folding hex wrench set for pulling radios and a valve core removal tool for deflating tires. All of these tools are small and light, and irreplaceable if needed. Buy a quality tire-inflation gauge as well; I use an Accu-Gage I found at a truck stop—it’s much more precise than the movable stick variety and enables you to bleed off excess pressure with precision.

Other essentials: An oil filter/strap wrench if your airplane has an oil filter (a one-inch combo wrench works here if you have room to swing it), a razor-sharp utility knife, a roll of .032 safety wire, a six-inch steel rule, a spark plug-cleaning tool, a spare spark plug (and a tube of anti-seize compound), a spare air filter, a spare tire tube, and a plastic pill bottle full of machine screws and washers that fit your airplane. Dow Corning DC-4 is good for lubing oil filter gaskets, and a small quantity of RTV silicone and gap-filling super glue can help out in many ways. Tie wraps, rags, and hand cleaner can also come in handy, and don’t leave out what could be the most valuable aviation tool of all—duct tape.

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