A Handle on Repairs

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Owner-driven maintenance can mean swinging a wrench, but thorough inspections and involvement with the shop are often enough, as shown in this article from Aviation Safety.

This article appeared in the February 2002 edition of Aviation Safety and is reprinted here by permission.


Advice: $50
Good Advice: $100
Questions Answered: $50
Dumb Questions Answered: $100
Service: $50/hr
Service if you participate: $100/hr

For most owners, airplane maintenance is a pit of quicksand. If you plunge in, it's easy to get in over your head. But if you stay out, mechanical problems can accumulate until dispatch reliability and safety are severely compromised.

The question owners have to ask is how involved in maintenance they want to be. The question has many answers, and the road to answering it depends upon first determining your objectives. Is the goal to save money? Improve reliability? Log hours toward the A&P requirement?

Next, you have to ask yourself how serious you are. The days of "point and shoot" maintenance are long gone. Not even the military can afford to summarily replace everything that doesn't work.

Minimal involvement means maintenance will be reactive only. You'll fix what breaks, without trying to anticipate something needing repair or replacement before it breaks. The minimalist pays only for what the IA demands to get the airplane's annual inspection signed off. Of course, there is no free lunch, and while this approach may reduce the cost of annual inspections, the price can be measured by reduced dispatch reliability and wholesale replacement of failed assemblies.

To be more involved, owners can adopt several strategies: proactive inspection, proactive replacement of items nearing their end-of-service life, owner-assisted interval maintenance (all logged under supervision), and owner-assisted annuals.

Personally, I don't participate in my annuals other than to show up during the inspection phase and have stuff pointed out to me. But I do spend considerable time doing the first three because I want to avoid in-flight part failures.

Clearly each owner's answer to the question of how involved they want to be depends on several factors. It depends on the availability of the owner's time, of the mechanic's time, of your need for reliable dispatch, of your tolerance for downtime and your budget.

Until a few years ago, I did not regularly do my own oil changes, when my base shop was so busy that I was in danger of running beyond 50 hours. That prompted me to purchase a filter cutter and learn from the base mechanic what to look for in the filter. I had seen his accordion cuts of my filters and those of other airplanes before, but nothing beats doing your own. For me, the process also helped lead to a better understanding of what to look for while in the engine compartment.

Each owner will eventually develop his own routine for participating in the airplane's maintenance. For some new owners that routine may develop by happenstance. Others may take a more aggressive approach in defining what they want to learn how to do, and going about accumulating the skills and tools. This strategy doesn't mean you have to spend your weekends in the hangar bedecked in grease up to your elbows. It can be as simple as 50-hour phase checks by the maintenance shop, with IRAN (Inspect and Replace As Necessary) for critical things on an agreed list. Your mechanic can help develop the list, which you can amend over time as you get more familiar with the needs of the airplane.

I've developed an inspection program for my Seneca II that includes a few items that are checked every time I use the airplane. It adds a few minutes to each flight, but that's nothing compared with the inconvenience of having something break at an inopportune time.

Rules of Thumb

There are several rules of thumb for dealing with maintenance. Primary among them is to treat your mechanic well. Generally, the way to convince your mechanic you're serious about maintenance boils down to: "Show interest, be accessible, pay attention, never stint on the funds, and pay promptly."

If you show interest and are accessible, the mechanic will know that he can finish the job and go on to the next. If he cannot get a prompt response from you when he wants to advise you as to a part failure or an extraordinary expense, he will be forced to move on to another aircraft. The shop cannot sit idle, as there are very slender margins.

If work continues, he knows you may be very, very miffed by a surprising bill. In addition, by not showing up or calling, you miss an opportunity for systems education -- and this is priceless. I always show up. The education is the dessert and I want dessert. His number on my pager gets a high-priority response.

Depending on your relationship with the shop, you might want to develop a routine so the mechanic knows how you would like to proceed. For example: You may want to give the go-ahead in advance for any repair the shop deems to be safety-related and to notify you by telephone, voice mail, fax or e-mail. You may want to set a benchmark, say $1,000, below which they have the authority to make the repair, but above which they need to check first. But if you make these kinds of arrangements, always honor them. Once they're in place, the mechanic will have no reason to stop work on your airplane, thereby delaying its completion.

In the course of your inspections as owner, don't fix anything that's not on the Part 43 list of pilot-approved repairs without advising the mechanic and requesting supervision. Otherwise your repair will constitute "unapproved in accordance with no data."

When your IA signs off on the aircraft, he's also putting his stamp of approval on the work you've done. He will not be able to do so if he didn't see what was done. For example, some owners may be tempted to replace worn-out-looking vacuum tubing with unapproved tygon tubing, a recipe for disaster. Do that and any mechanic worth his salt will demand that it be replaced with proper stuff.

Advise in advance what you intend to do and the mechanic will tell you (or sell you) the proper materials to use in the repair, and you'll get a logbook entry documenting the event.

The list of maintenance rules is long, indeed.

The Highlights

  • Don't leave a tire on until you can see the air. That's penny-wise and pound-foolish. I use certified retreads to make tire replacement economical, but be careful because some retracts leave marginal room in the wheel wells. If you think tires are expensive, compare it to how you'll feel after the airplane hydroplanes, or when it ground loops away from the flat tire, or when it strands you at a remote airport on a weekend.

  • If you see it, fix it or get it fixed. A slightly low landing gear oleo strut can result in oval rivet holes if your next landing isn't perfect. Bad baffling can cause your cylinders to run hot. There's no point to looking if you aren't going to act. Recently, after shooting approaches in IMC, I noted a "click-thud" coming from behind the panel when I was holding near-full up elevator. It turned out a strap tie had broken and a vacuum hose was brushing the top of the chain wheel apparatus behind the panel. A beefier strap tie fixed that and prevented the hose from abrading -- with resultant loss of vacuum, or worse, loss of control.

  • Transient stuff deserves your attention, too. An intermittent alternator light could be as serious as an impending brush failure or as simple as moisture in the regulator. A drippy fuel drain could mean debris in the tank that will probably lodge again, eventually destroying the gasket. An excessive magneto drop that "corrects" itself through leaning could be as simple as carbon fouling, as tough as lead fouling, a plug in one of the cylinders near failure -- or you're about to have catastrophic magneto failure due to flooding of the oil seal.

  • Anticipating failures costs less than suffering through the failure. Rather than wait for the complete assembly to fail, fix the suspect component. For example, a fuel pump with a leaky shaft seal can be sent out for pump head overhaul, rather than waiting for the whole unit to flood and be trashed. Check out the price of parts and you will see this strategy really pays off. Check out the wait for parts, and you'll see it really makes a difference.

  • Sometimes a specialty shop does a better job and is a better value. My current shop used to groan when they saw me taxi up in the turbocharged Mooney. Yes, the mechanics take care of four Mooneys -- and they really did their best to help me out -- but in the end the trips to a distant maintenance shop that specialized in Mooneys made the difference. The part was always in stock and they had always seen this type of failure before.

    The downside is that you don't get the same education because you're not there. So, there's a corollary: First-timers, don't buy an exotic bird. How are you going to get your education from afar?


Learn the quirks of your bird from the type-specific club. Virtually every model of airplane has one, from popular Cessnas and Cherokees to clip-wing Cubs and Beech Staggerwings. Read the FAA's Service Difficulty Report summaries and, if you're concerned, conduct an inspection.

Buy the maintenance and parts manuals for your aircraft so you'll know what your mechanic is talking about when he refers to a bad part number. The Service Difficulty Reports also usually refer to part numbers. It'll help a lot if the mechanic can phone you with news that you need "part 19 on page 1G18" and it's on his microfiche and your computer screen at the same time.

A maintenance manual will give you insight into what to look for, ranging from (clockwise from top center) the main wheel assembly, wing inspection panels, muffler welds and yoke linkages.

Don't even think of presenting your mechanic with unapproved parts. This is like having an illegal aircraft for the check ride. He's risking getting his ticket pulled if he accepts. If you want to obtain FAA-PMA or factory parts on your own through discount mail-order sources, better ask first.

Some mechanics welcome the reduced workload in tracking down and ordering the part. Others are accustomed to marking up the part to improve the shop's bottom line and are reluctant to lose the revenue stream. Some don't want to take the chance that a counterfeit part will be foisted on them. Ask first.

In many places, the FBO shop rates are less than the local Dodge dealership. Parts are what cost, so make sure you and your mechanic are on the same page.

Many aircraft owners worry about how to select a mechanic. There's also another side to the equation. You need to make the mechanic select you as well. When you need help and the shop is busy, they're going to give priority to the customers who are reliable, easy to deal with and who pay their bills promptly. You want to be one of them.

Choose your mechanic by reputation. Ask other aircraft owners and you'll quickly get a sense of who deserves a shot. Temper that decision by what kinds of airplanes the mechanic already takes care of. You don't want to finance a learning curve by owning the shop's most exotic bird, nor do you want to be left in the dust by trotting a Skyhawk into a shop that makes its living off Gulfstreams. Choose by facility. A repair station may use a teenage apprentice to actually do the repair; the old salt may only see your bird at critical times. Sometimes a one-man shop is a better option.

If you think you are getting ripped off, it might be true. But you also need to consider that you may be the one who needs an education. Could you have avoided the problem by being more proactive? Are you financing a learning curve? Should you have gone to the specialty shop?

You know you have a good relationship when, after eight hours of work, your mechanic calls you up and says "I spent about eight hours chasing it and it was something really, really, simple that I should've checked first. I can't bill you for all that."

Finally -- and most important -- the best preventive maintenance is operating your machinery properly.

  • Though your POH is loaded with data for operating at 75 percent power, remember that the airplane is marketed for speed, so the manufacturer has pushed it to the limit for a competitive advantage. Immense amounts of wear and tear can be avoided simply by operating at 65 percent power. The difference in cruise speed is generally small, typically on the order of six to eight knots. Want to go faster? Buy something faster and run it at 65 percent.

  • Want to run lean of peak? Some airplanes thrive on it, some don't do as well. Just remember that all economies are false if you work your way to an early overhaul, so do it right. Make sure the aircraft is equipped with the engine-monitoring equipment so you know what's happening up there.

  • Do you really need to fly when the forecast is for temperatures far below zero? That cold is just hard on everything that flexes.

  • If you're not going to fly for three months, pickle the engine in accordance with the factory procedure. It doesn't cost much and it will avoid lifter corrosion.

  • Cold out? Preheat the engine and the cabin. Most of the engine and gyro wear occurs during startup. Preheat strategies vary, but be sure the engine is warm to the touch before you crank so that the oil actually runs. Putting a 1500-watt bathroom heater in the cabin for a couple of hours prior to departure also makes your passengers happy.

  • If you have fuel bladders, top the tanks before you put the airplane away. Bladders last longer without oxygen contact.

  • Reduce manifold pressure at a maximum of 3 inches per minute. When one of my turbo-single students went from 65 percent to idle power in one pull, I had to ask, "Can't you hear the turbo groaning?"

  • If you're flying over hostile terrain, remember you'll lose all economies if you are forced to land off-airport. That'll cost lots of parts and lots of labor. Plan your route and altitude in a manner compatible with survivable low-damage emergency options.

  • By the way, when's the last time you checked tire pressures during your preflight?

Remember, your aircraft is only as good as you make it. That requires contributions of time, money, education and effort.

Diary of Meticulous Maintenance

Over the years, my maintenance diary has led to the following measures for my Seneca II. A simpler aircraft will omit some of these items; a more complicated airplane will have more. An experienced mechanic or another long-operating private owner will be very helpful making out your list. B.C.


Key visual inspection points include the gear locks (top), the fuel drains (middle), and the drag braces (bottom). Problems in these spots often begin as intermittent defects, but don't expect them to heal themselves.

  • Anything that leaks gets fixed, regardless of whether it's water, oil or fuel. Leaks don't fix themselves and only get worse.

  • Any wet landing is followed by a wipe down of the brake calipers. Moisture accumulates on the edges of the brake cylinder bores and causes pitting, so the next time your linings get thin, the o-rings will extend toward the edge and encounter the pits. You'll lose fluid -- maybe even brake function.

Every Postflight

  • Wipe your finger in the exhaust stack. Anything but a dry light gray residue means a change in oil disposition. Clock oil consumption in a log.

  • Magneto check. If your magnetos are going to prevent a trip you want to know about it in advance so that it can be repaired in advance.

  • Inspect landing gear. Check out the gear down-locks. Look at the tires as the aircraft is being pushed back with the tug. Order replacements three months before you expect the tires to wear out.

Six Months After Annual

  • Remove wing inspection panels. Search for fuel hose leaks, bad-looking stuff in the gascolator/strainer, chafing wires. I've saved a strobe generator unit from a short. Do a dental-mirror exam of fuel selector linkages, visual inspection for play in any control surface.

  • Mirror magneto inspection. Pressurized magnetos retain moisture.

  • Inspection of the combustion heater. This is the Achilles' heel of most multiengine aircraft and it will terminate a trip. Had I been doing this I might have saved $800 by replacing a capacitor instead of the whole switch.

At Specific Intervals

  • De-cowl at 25 hours. Search for anything wet, loose, chafing or bent, or any carbon plume. A problem that might have compromised my right mixture-control cable was picked up early because of this.

  • Change oil at or before 50 hours. If you don't fly weekly you should change at shorter intervals. Inspect each plug and re-gap. Cut the filter and inspect.

  • In the autumn, climb into the flight levels and check de-ice gear completely. That way, parts can be obtained in time for the icing season.


  • Scan for proposed ADs. They almost all become real ADs, but even if they don't it'll alert you to a potential problem. If it does become an AD, you'll want to get the parts before everyone else tries to get them. Frequently I know about them before my mechanic, and we obtain the part and do the service early. The most recent example was the solenoid fuel valve for the cabin heater.

  • Any transient anomaly gets logged in a separate book, so I have an accurate history. Include all indications, altitude, temperature, instrument readings, etc.

  • Carry fuel drain spares and the appropriate wrench. This is a no-go item if it refuses to seat. Yes, you can change them even with fuel in the tank.

  • Keep appropriate light bulb spares in the hangar or aircraft. Flashlights taste terrible. Fix it on the spot or you'll likely tolerate it for a long time.