Deferring Airplane Maintenance

Making the right fix it or fly it decision depends on whats broken and how you want to use the airplane.


My grandmother loved an adage. “Never put off until tomorrow what you can do today.” “A stitch in time saves nine.” “If you dont find time to do it now, when will you find time to do it later?” All fine words to live by, but my grandmother never paid for an aircrafts annual inspection.

With the base price of a straight-leg single-engine airplane annual at some shops hovering around $1500-thats the price if nothing is actually wrong with the airplane-some of the adages heard around the shop are “It flew in, itll fly out.”

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“You said it was fine that way last year: why is this year different?” and the most common, “I cant afford that-just sign it off now and well get it on the next annual.”

To fix or not. What will it cost now versus the price later? Does it affect airworthiness? What does the FAA say about it? Whats the worst that can happen?

Legal Stuff

The decision to perform or defer maintenance is a dance performed every day by pilots, owners and mechanics. The pilot wants most things operational. The owner wants the most value for his maintenance dollar and not to spend any more money than necessary. The mechanic must weigh his responsibilities to safety, the risk to his certificates and insurance, his common sense and fairness to his customers. Just as in any dance someone has to lead and someone must follow; there are elements of trust, some folks are bolder than others and some toes may even get stepped on. If you are an owner/pilot/mechanic you dance alone.

The FAA is fairly straightforward on the issue of deferring maintenance. Federal Aviation Regulation 91.213 discusses inoperative instruments and equipment. Essentially, it says if something on the airplane is broken, you cant fly. The actual quote is: No person may take off an aircraft with inoperative instruments or equipment installed…” with a standard, FAA-approved “except” following it.

The two main exceptions are if an airplane operates with a minimum equipment list (MEL) or the operator complies with paragraph (d) of the regulation. This paragraph gives most of general aviation some relief, but has a devil hiding in the details. Notice how the regulation prohibits you only from taking off with inoperative equipment. If you are in flight you can continue, although another FAR, 91.7, states the pilot “shall discontinue the flight when unairworthy mechanical, electrical, or structural conditions occur.” Sort of a silly regulation-it could be argued that anything that renders the aircraft unairworthy would, in itself, cause the craft to seek earth dramatically and automatically. The FAA is referring here to their legal definition of airworthy (See the sidebar on page 9).


If your aircraft or operation is big enough to have an MEL program, you will find it is a lovely thing. Mostly the domain of airlines and other commercial operators of large aircraft, the MEL is a list of items that can be inoperative while the machine can still be legally operated. Time limits for how long before the discrepancy must be dealt with and any operating limitations that apply are also included.

For example, a landing gear door can be missing (removed) for a certain number of days or flight hours or cycles before it must be re-installed and a maximum operating speed limit or a weight reduction is specified to make sure structural or performance problems are addressed. Minimum equipment lists are how airlines are able to fly complex machines with small discrepancies while still maintaining a consistent, acceptable level of safety.

A by-the-book mechanic in New York doesnt cancel a flight for a broken windshield wiper and a daredevil pilot doesnt take a full load of people out of Seattle with inoperative flaps. Both refer to the MEL, where the decision has been pre-made for them. The MEL can be viewed as a pre-approved, “floating STC” allowing an aircraft to undergo various changes yet still retain its airworthiness. If you have an MEL, you can sit out the dance.

While an MEL program is theoretically available for an operator of a single engine airplane, the FAA isnt keen on going through the exercise to get it approved. Each list is tailor-made and approved for a specific aircraft. It is derived from an existing master minimum equipment list or the aircrafts basic equipment list included with the rest of your aircrafts paperwork. It is not a simple matter to have approved-for most general aviation operations, an MEL program is not worth the effort.

The Exception

Meanwhile FAR 91.213(d) says you can fly rotorcraft, non-turbine-powered airplanes, lighter-than-air, powered parachute or weight-shift aircraft with an inoperative piece of equipment if you disable (or remove) it and placard it “inoperative.”

Sounds pretty simple, eh? Of course you would make sure the inoperative items wouldnt impact the safety of flight; such as lights on a night flight or de-ice boots in icing conditions. That assumption almost goes without saying, although the regulation makes sure to mention it. In FAR 91.213(d)(2), the FAA says you also must determine if the inoperative equipment is a required component. Not too tough, right? You can look in the aircrafts flight manual to see if it is required by the equipment list or operating limitations section. You also need to make sure an AD doesnt require it.

Then you have to look in 91.205 where it lists equipment and instruments required for VFR day, night and IFR. A lot of things to check but still doable. Remember how I mentioned earlier a devil in the details? Here it is: You must further ensure the instrument or equipment is not “part of the VFR-day type certification instruments and equipment prescribed in the applicable airworthiness regulations under which the aircraft was type certificated.” Who knows the regulations that governed the manufacturer when their airplane was type certificated? Not me. I checked around and this part of the regulation seems to lead us down a dead-end road.

Bottom line: You can try to use this exemption to legally operate an aircraft with inoperative or removed equipment, but be aware of the potential gotcha.

Real World Stuff

For the rest of us, we have to make some decisions. If you interpret FAR 91.213 literally, the plane must be in as good a condition as the day it left the factory. If a wingtip nav light bulb is burned out, the airplane is not airworthy, even for a day VFR flight. Luckily, the FAA is not an ogre who enforces this rule with an iron fist, although you need to be aware that you are in “interpretation territory.”

For an annual inspection most maintenance shops will list discrepancies found during the inspection and assign a value to them. One place I know of uses the letters M, R, and O. “M” is mandatory-they will not sign off the plane as airworthy unless that item is fixed. “R” is recommended, either because it would be cost-effective to fix now while the plane is opened up, or because it will have to be fixed later and could cause a bigger problem if left alone. “O” is optional: nice to fix, but purely up to the owners discretion. And so the dance begins.

On some issues, the mechanics lead by putting their foot down and not budging on “M” items. The owner has to trust the inspection authority (IA) holders judgment and go along. On “R” items, the owner is allowed to call some moves, and the mechanics trust him if he promises to fix it later and to not step on the mechanics toes. If these people have moved across this floor together before, things go more smoothly and more trust is extended to each partner. So how do you and your mechanic decide?

Interviews with IAs showed me how experience and judgment play a part. Lets take a best-case scenario. The owner/pilot is a regular customer who feels safety is more important than dollars. The mechanics have worked on this plane for years and know the machine and the owner well. They have watched certain things age and wear, are familiar with the pilots techniques and usage habits.

“We have been watching this alternator bracket for a couple of years now,” said one IA as he showed me a Bonanza. “We put in new bushings last year but knew it was not a permanent fix. We checked it a month or so before annual, ordered the

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part and replaced it this year.” The owner knew what was coming, the shop knew he would not go anywhere else for maintenance during the course of the year, and everyone trusted that the right thing would be done.

Contrast this with the owner who goes to a different shop each year for an annual. The same IA told me, “These one-time guys say Just make it pass annual, Ill fix it next year but they never come back and then some other shop thinks we do sloppy work. We wont defer much for those kinds of owners.”

Sometimes its not the customer but the factory that must be overridden. On a Cirrus recently one of the landing gear legs had a noticeable amount of slop in its mounting bracket. The factory said it was within limits but the mechanic looked at the options. He and the owner disregarded the factory recommendations and replaced a $160 bracket that will likely prevent the purchase of that same bracket and a $5000 gear leg in a few years. An example of the value of judgment based on experience.

This mechanic also has some general guidelines. He said corrosion limits are fairly well defined by the FAA and he uses that data to decide. He will not defer anything having to do with flight controls-too important, in his mind, to take a chance. He doesnt worry much about cosmetics but he also knows his customers-some will not tolerate even a small paint chip so he just goes ahead and fixes little items and includes it in the price. Other folks dont want to pay $85 per hour for something they can do themselves, so he works with them to give them the best value. His pet peeve is folks who are penny wise but pound foolish.

“During an engine change some people want only the engine changed. Its an expensive proposition and I understand that. But the baffling, accessories, motor mounts, hoses-they all wear out at about the same time. After a year on the new engine we usually have to replace those things at a greater cost than if we had done it at engine overhaul.”

The COST of Deferring

I can relate to that. I recently purchased and refurbished a Cessna turbo 182 RG. A year previously a new carburetor had been installed but nothing else associated with it. The throttle had been stiff since I bought the plane, and at annual we found the bushings in the throttle/turbo mixing plates to be worn to the point that they broke into pieces. The pieces had jammed in their slots, causing the stiff throttle which bent the control cable and wallowed out its attach point. This was not wear that occurred in the 50 hours since carburetor replacement. We found three imminent failures of the throttle system, any of which could have been a killer. We had to replace the bushings, throttle control cable and attach bracket. A few dollars worth of bushings a year ago would have saved us hundreds of dollars and a potentially deadly situation.

That brings up the adage, Pay me now or pay me more later. On a plane that flies 20 hours per year, a worn tire can last many months but on a flight school plane it would make no sense not to change it when the chance presents itself. My local maintenance shop charges half an hour of labor for a tire change during an annual but one-and-a-half hours otherwise. By waiting to use up the last few dollars of rubber it can cost more than the new tire is worth. The same applies to brakes, oil changes or any maintenance done regularly.

One owner discovered the costs of deferred maintenance. He operated a small fleet of banner tow airplanes that worked hard during the summer. When he first went to my friends shop a lot of little things that had been deferred for years were taken care of, and the price of the annual reflected the extra work. In his words, “The cost of those first couple inspections hurt, but in the end I saved money-I was accustomed to some down time but didnt have any this last season.”

When asked about the strictly legal aspects of deferred maintenance, my IA friend says he is hesitant to document deferred items in the aircraft logs. “I dont think of it as signing an annual. Im signing a blame sheet.”

He keeps a separate set of notes on what is deferred-what he calls his watch list. For steady customers this works much like having a family doctor who knows you well and monitors your health. For other planes he may never see again he knows if he doesnt fix it now, it will probably never get done. “I use common sense,” he says, “but one thing I ask myself is how will I explain it to the judge?”

If you are the owner and help make these decisions, you should consider it too.

With over 15,000 hours and 10 years experience as a bush pilot, Mike Gugeler operates MT Air, based in Erie, Colo.


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