As I write this, my arm is bloody, my neck tweaked. My patience—tested to the point of failure—is returning. Although the cause of my current condition was a car repair, the root cause of the problem translates to anything that requires maintenance, airplanes included.
Whoever installed the hose clamp on the lower radiator hose of my Triumph TR6 gave no thought to its future access. Perhaps they were working from underneath, with the car on a lift. At any rate, the slotted hex head for tightening and loosening a hose clamp proved inaccessible to me; I don’t have a lift. Had the clamp been rotated 180° on the hose, the screw would have been an easy reach from above for anyone. In the event, I cut the hose, as the radiator was coming out anyway.
Ease of future maintenance can be, and should be, built into your aircraft. Granted, there may be things baked into a design for which you have no control (I’m aware of a design that requires removal of the fuel tank to perform a routine fuel filter inspection and replacement. My 1996 Jeep required removal of the grille to replace side marker bulbs. Both are examples of poor design), but you will have control over aspects of the build that can make ongoing maintenance easier. The easier maintenance is, the more likely it is to be done. Win-win.
Hose Clamps and Adel Clamps
The good news on clamps is they are usually, accidentally, installed in the most convenient manner, which means they are accessible in the future. Yet, when building new, it’s easy to lose sight of the future. Plumbing an oil and fuel system before the engine shrouds, carburetor heat, and cabin heat systems are in place may leave a clamp’s hardware inaccessible. Pause during the installation to envision the clamp’s future accessibility.
(As an aside, I avoided hose clamps in my fuel and oil systems at all costs, favoring AN hose fittings.)
Firewall Through-Fasteners
When building an airplane, it’s easy to bolt a voltage regulator, oil cooler, or “black box” to a firewall before the engine is installed and the back side of the firewall rendered inaccessible by a cockpit glareshield, instrument panel, and rudder pedals. Once those items are in place, access to the interior hardware becomes—well, it becomes the dark, hot, sweaty environment—the primordial soup, if you will—in which new, unpleasant words and phrases evolve. Using nut plates, instead of locknuts, on the inside of the firewall makes future removal and replacement of life-limited components much easier.
Electrical Connections
Electrical connections deserve your long-term thought as well. Installing the nervous system of your airframe is easy when done while building, but it’s another task that requires thinking ahead to servicing the finished aircraft. Can the tail position light be removed and replaced without drilling off a tail tip? Can a multi-pin connector be reached in the crowded confines between the engine and firewall? Have you left enough wire (a service loop) in the electronic flight instrument system (EFIS) loom to pull it away from the panel without having to first reach under the panel into a tangle of wires to disconnect it? Every moment spent thinking ahead during construction can save untold minutes and frustration in the future.
Routine Maintenance
Every engine and airframe requires routine maintenance. Planning for it during construction and installation will help ensure it gets accomplished. As I mentioned earlier, I know of a design that requires the fuel tank be removed—through the cockpit!—just to replace the fuel filter. What are the odds every one of those airframes gets the fuel filter inspected during each condition inspection? Engines that require routine head torquing and valve adjustments should be shrouded in a way that makes removal of the cooling baffles easy, so they don’t become an impediment to performing timely maintenance. Oil dipsticks should be accessible during a walkaround inspection. Tire pressure valves should be accessible without having to involve more than a single tool, preferably a screwdriver. And so it goes …
I think there is a side benefit to planning ahead for easy maintenance. Those who put thought into future maintenance while building, I believe, are also less likely to need to perform unscheduled maintenance. Of course, there’s no getting around routine maintenance, but the need to fix wiring problems or replace damaged fuel, oil, and coolant lines, or fix a binding mixture cable, is reduced when thought goes into a good-and-proper initial installation.
So true!! I spent about a half hour trying to remove a nut on the cockpit side of the firewall. It sure went on easily before the skins were on! Another thing I have done is use socket screws (for Allen wrenches) in place of Philips head screws. Great if you have to remove the screw when you can’t easily access the head. Of course these are not structural screws, mostly behind and under the instrument panel. Good article, thanks Kerry.
Thanks for reading and commenting!
For years I’ve been wishing AN hardware was made with a hex socket! What a great replacement they’d be for screws. Care, and a crisp phillips head screwdriver are needed to tighten elastic stop nuts on Phillips head screws.
Listen to Kerry all you builders; never truer words were spoken by an aviation writer — in the history of aviation! Adel clamps you can’t reach with both hands are the enemy, you will rue the day you trimmed wiring that was “too long”, nut plates (plate nuts?) are your best friend, every.single.item you install in your EAB will need to be replaced at some point, everything can crack…I could go on.
Regarding tools, you can invest in flush cutters to trim off zip ties, or a large box of band aids if you choose to use ordinary snips; your choice. Plate nut jigs? Hell yes. Quality multi-meter from Fluke? Oh yeah.
Keep the best notes you can, and faithfully record every detail of your electrical system. Do all these things and you may be able to retain a measure of sanity as you and your airplane accumulate years of life.
I’m flattered. 😊
You add great points! Thanks you for reading and commenting.
I spent four hours sweating and cursing the person who clocked the clamps on the cylinder oil return lines on my IO-360 when I replaced those lines this year. When I put new clamps on, I did so with the thought, “I will likely be doing this again one day, make it easy on myself.”
Exactly! What should be easy can be made so difficult without a bit of consideration for future maintenance. Thank you for reading and commenting.
Good stuff, and too easy to brush off in the rush to completion.
One aspect is access. We talk about “closing out” structures, but there are certainly times when one is going to need back INTO the structure for maintenance. Generous inspection panels, etc. are the key here.
Access to the bottom of the cockpits of single-seat airplanes is usually very difficult. The picture shows a modification I made to my Fly Baby… an inspection panel that fit across the lower stringers on the fuselage. Combined with existing panels just behind the firewall, it lets me expose the entire lower cockpit area, from the firewall to behind the pilot seat. Easy enough on a fabric airplane; aluminum airplanes might need more thought.
Eventually, I painted a fake cockpit on this panel, just like Canada does with its F/A-18s.