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Cockpit Accessories Maintenance

Ailing Instruments: Replace Them If You Can

Despite the hoopla that has surrounded modern glass cockpits, round dial steam gauge instruments still represent the majority of the fleet. Plus, theyre 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. Heres a look at some of the tricky details that come into play when instruments need service. Be forewarned that quality repairs wont 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 manufacturers 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 wont cut the mustard.

Larry Anglisano
Verified

Despite the hoopla that has surrounded modern glass cockpits, round dial steam gauge instruments still represent the majority of the fleet. Plus, theyre 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

Cockpit Panel Replacements

primary instruments could be worth your life. Heres a look at some of the tricky details that come into play when instruments need service. Be forewarned that quality repairs wont come cheaply.

Overhaul is a Relative Term

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 manufacturers 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 wont cut the mustard.

A true instrument overhaul should include removing and replacing major components, including bearings, gimbals, rotors and gaskets. Quality work often includes reworking the instrument’s faded face and markings, repainting the case and even replacing the bezel glass. Were talking a true teardown and rebuild here. A quality overhaul should be as good as a new instrument. True overhauls deserve and often carry a full-year warranty, which is the same as most factory-new instruments. Basic repairs to an instrument wont come close to this standard.

When talking budget instrument overhauls, owners might not understand that theyre getting a basic repair thats being represented as an overhaul. Low overhaul pricing is tempting and sometimes it works out in the customer’s favor. Other times its a set-up for hassle. Even a quality overhaul with a high price tag might cause some grief as some gyros are just picky and not all techs are perfect every day. Premature failures can also come from worn instrument panel shock mounts, misadjusted vacuum regulators or contaminated vacuum lines and be no fault of the overhauler.

Its how the shop handles the rework that separates a good instrument shop from a bad one, so our advice is to establish a relationship with reputable, well-established instrument facilities that have large inventories on hand. You pay a premium for this but its worth it when they have a loaner unit to eliminate down time or quickly send a replacement.

Chuck the Museum Pieces

Some instruments are too far out of production or parts are simply not available to do a true overhaul. Some instruments just arent worthy of exchange. For ancient models, shops wont have a healthy supply of workable core units in their pool to rebuild, so repairing your unit is the only thing they can do. For the repair, most shops structure pricing on a parts and labor basis, based on what it takes to repair the instrument to a level where they can sign it off.

Larry Anglisano

Editor in Chief Larry Anglisano has been a staple at Aviation Consumer since 1995. An active land, sea and glider pilot, Larry has over 30 years’ experience as an avionics repairman and flight test pilot. He’s the editorial director overseeing sister publications Aviation Safety magazine, IFR magazine and is a regular contributor to KITPLANES magazine with his Avionics Bootcamp column.