“Pay me now, or pay me later.”
(Fram oil filter slogan, Circa 1971)
DMI (Deferred Maintenance Item) – postponing
maintenance activities in order to save costs, maintain a schedule or to meet budget
constraints. The failure to perform such repairs could lead to higher long-term costs, component deterioration and ultimately, component failure.
Lately, the Duke has been enjoying some fixes and upgrades: new boots, overhauls on the mags and props, avionics upgrades including a nav/comm, WAAS GPS and an ADS-B. But the air conditioning compressor blew a gasket (literally), the 48-year-old KWX-50 black-and-white weather radar only receives The Dick Van Dyke Show and the engines are nearing TBO. With just 300 hours to go, I’m staring at $160,000 for two overhauled TIO-541’s and $25,000 for a new color radar. Everything is relative and we have readers who regularly spend much more than this; I get that. But to carry four people and luggage, at 20,000 feet and 220 kts, on an airline pilot’s salary, the Duke suits me.
A Budget Far, Far Away
Many readers have written describing their experiences and difficulties maintaining, upgrading and even sustaining, their airplanes. When our receivables under-fly the payables, difficult decisions must be made. We often purchase a little bit more airplane than we can afford, forgetting that component issues, new technologies, regulations, insurance, training and other owner-pilot needs and whims will prompt unforeseen spending. I’m not immune to this forgetfulness and whimsical spending because the Duke and I are sometimes far apart on a budget. As described above, my $250,000 airplane currently “needs” yet another $185,000 worth of stuff in addition to the regular items that break. But asking your shop to defer maintenance items to massage the budget can put your AMT (Aviation Maintenance Technician) in an uncomfortable position of not only liability, but morality. The maintenance shop I use has encountered many owners experiencing this conundrum and asked me to write an article emphasizing the importance and long-term value in keeping up with both large and small maintenance needs. Maybe they were trying to tell me something.
You Can’t Make Me
While some shops may require that service bulletins (SB’s) are met and recommended overhaul times for components are not exceeded, only AD’s (Airworthiness Directives) and mandatory inspections, whether accomplished every 100 hours, on a progressive schedule, or as an annual inspection, are required by the FAR’s. Company flight departments or insurance companies may impose additional compliance conditions.
However, even if found during a mandatory inspection, the FAA allows us to defer some of the non-airworthy items our shop may uncover. Title 14 CFR section 91.205 lists the aircraft equipment and instruments that must be installed and requires the instruments and equipment to be in an operable condition. For example, if you don’t have an MEL and CDL (Minimum Equipment List and Configuration Deviation List, discussed shortly), you may only fly with certain instruments inoperative, provided that:
The inoperative instruments are not basic VFR-day instruments that were required to get the aircraft certified in the first place;
The inoperative instruments are not listed in the aircraft’s equipment list, such as stall warning horns or other items listed in the type certificate or items required for the type of flying you’re about to do (such as lighting for night flying);
The required instruments are not required by an AD;
The inoperative instruments are deactivated, clearly marked as inop and are recorded in the maintenance records.
Give Me A Break
Outside of the above conditions, section 91.213 addresses inoperative equipment and provides relief from section 91.205 through the use of an FAA approved MEL. The MEL allows flight with components either inoperative or degraded. It’s aircraft-specific and spells out which equipment may be inoperative along with procedures required to operate under very specific conditions while maintaining airworthiness. If a component is not listed in the MEL, the item should be considered as required: the wings, landing gear and motors are obvious examples. The MEL will list actions and procedures that must be accomplished by the Operator “(O),” Maintenance “(M)” and Dispatch “(D)” to use the relief provided by the MEL.
Another avenue in which we may continue to fly with missing pieces-parts is the CDL (Configuration Deviation List). Examples of CDL items are missing vortex generators, static discharge wicks or fairings and panels. For large aircraft, a separate NEF list (Nonessential Equipment Furnishings) may include things like window shades or galley equipment. However, when multiple operators discover an operational issue or defect with a critical component, a notice may come to you in the mail.
A Letter from the IRS
Receiving a SB (Service Bulletin) or AD (Airworthiness Directive) in the mail is right up there with a letter from the IRS. An SB is a notice from a manufacturer informing operators of a product improvement or problem. Having realized that there are distinct levels of seriousness, manufacturers may categorize them as informational, optional, recommended, alert or mandatory. It may be something minor like replacing the original metal chains on the fuel caps with plastic retaining lanyards, or something severe like a crankshaft inspection. The first thing to do is read the section that describes to whom the AD or SB applies. Affected users are normally identified by the component manufacturers name and serial numbers or part numbers for the affected component. Although a service bulletin may be listed as mandatory, compliance isn’t necessarily required unless accompanied by an AD. I’ll add a caveat here: a recent “mandatory” SB (that is not yet an AD) for a piston-engine component described failure to comply with the SB as possibly resulting in “a sudden and catastrophic failure of the engine.” Try justifying non-compliance with that one when someone prosecutes you for crashing into their pre-school. An Airworthiness Directive (AD) is issued when the FAA believes that a perilous condition exists in a product (engine, airframe, appliance or propeller) and the potentially unsafe condition needs special inspection, alteration or repair. An AD will often reference a service bulletin as a method of complying with the AD. An example of an AD is the wing attach bolts on many Beechcraft and the pressure decay test on many combustion heaters for the cabin. AD’s are legally enforceable regulations, and if you own or operate the listed item, compliance is mandatory.
Don’t put off until tomorrow, what you can do today.
– Benjamin Franklin (and your AMT)
We can agree that the following are critical components for keeping the airplane in the air: The wings, empennage, fuselage and flight controls. If any of these are missing or severely damaged, we will have an aircraft control, weight and balance or life support issue. Those components are followed very closely by the propulsion system that may include propellers or turbine components and a fuel storage and delivery system. We won’t necessarily die without a propulsion system, but an off-airport landing in a twin-and-turbine style airplane would be interesting. A landing gear system is next on our list of priorities so that we may land on a nice surface of our choosing. Again, this system isn’t needed for survival, but it should increase our odds during the landing. With the above axioms in mind, consider the following list of squawks that owners (myself included) most often ask AMT’s to defer, and my experience with some of them:
I once had a slow drip from a wing-tank. The fuel bladder quick-drain eventually gave way and the entire right system leaked out. Only the crossfeed kept the motor running.
Metal in an Oil Filter
We found three bad lifters and cam lobes on the right motor. Repairs were made.
Brake Discs and Pads
A fellow Duke owner’s brakes failed and he went off the end of the runway.
Flight Controls with Corrosion
Haven’t seen this one yet, but I did have an autopilot trim issue because the tension on the elevator cable was wrong.
Worn Fluid Hoses
A very small engine-oil leak eventually (two years) exposed itself when the fitting became loose enough to cause a large drop in oil pressure. I shut it down and landed single engine to LPV minimums.
Overhaul of Old or High-
My left prop once went into feather on landing roll.
Overhaul of Prop Governors
No experience with this one yet but we don’t want the prop to run away on us.
Low Compression on Cylinders
(can’t we go another year?)
Guilty as charged. I pushed my last set of motors 300 hours past TBO by replacing cylinders as necessary. But this technique could allow a catastrophic failure of one cylinder to trash the rest of the motor.
It’s Not Whimsical Spending
Like me, you may have asked your shop to defer some items. Let’s do our AMT’s and ourselves a favor by limiting DMI’s and by keeping up with AD’s, SB’s and recommended TBO’s. Don’t blow a gasket over the expense or downtime. It’s not whimsical spending; we can pay now, or pay more later. Besides, no one wants an anxious AMT, an unresolved AD/SB or to watch “I Dream Of Jeannie” on a black-and-