Maintenance Matters

November 2008 Issue

Ailing Instruments: Replace Them If You Can

Repairing steam-gauge instruments looks like a bargain but can cost you more in the long haul.

Despite the hoopla that has surrounded modern glass cockpits, round dial steam gauge instruments still represent the majority of the fleet. Plus, they’re still required for backing up glass panels. Eventually, the costly prospect of dealing with failed flight instruments must be addressed. The common question is this: Should the instrument be repaired or simply replaced with a new or newly overhauled unit? The short answer is that it depends on the instrument's vintage, its complexity and what you expect for its longevity. There are a few factors that should help make the decision: your expectations for aesthetics, the shop's warranty period and whether the instrument is primary and critical or used as a backup. Consider that primary instruments could be worth your life. Here’s a look at some of the tricky details that come into play when instruments need service. Be forewarned that quality repairs won’t come cheaply. The old saw of getting what you pay for certainly applies to instrument work. In fact, if an instrument repair or replacement cost seems excessively low, quality is likely being sacrificed somewhere in the process. For once, the FAA can actually be accused of offering a level of leniency when it comes to instrument overhaul—at least according to practice versus manufacturer’s definition. A shop can legally represent an instrument as overhauled (abbreviated OHC for "overhauled condition") even if none of the internal components are actually replaced. One shop told us that a simple inspection of the instrument's internal components might be enough to stamp the instrument as overhauled. But when it comes to satisfying the criteria spelled out in a given instrument's maintenance and overhaul manual, this practice won’t cut the mustard.

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