Steam-to-digital swaps prove popular
Glass cockpit capabilities in round-dial form factors
Owners of older aircraft have in recent years gained a number of affordable and modern avionics retrofit options. The arrival of new products and recent increases in used aircraft value have combined to make replacing six-pack steam gauges with digital instruments (of roughly the same size and shape) more appealing to many legacy aircraft owners. Digitizing steam gauges does more than replace an instrument—it also adds modern features and functionality, and improves reliability without requiring major instrument panel changes. At least one producer of digital drop-in replacements for round-dial instruments reports an order backlog.
Five years after Garmin led the way to lower-cost round-dial instrument replacements with the G5 electronic attitude indicator for certified aircraft, which was installed in the AOPA Sweepstakes Cessna 172 and helped AOPA promote broader development of affordable avionics upgrades with powerful features, options available now include Garmin’s rounder and more capable GI 275.
Unlike the G5 instrument that preceded it, the GI 275 fits neatly in an instrument panel hole previously occupied by a legacy six-pack instrument. (The G5 could be installed in such a slot, though it had a square housing that extended a bit beyond, and that could complicate some installations where space is tight; some might also consider it an aesthetic compromise to have a square instrument housing among otherwise round dials.) The GI 275 fits more neatly within a relatively new class of instrument retrofits that appeal to aircraft owners of more modest means, or those who don’t think it makes much sense to upgrade an aging aircraft with fully fledged glass panel solutions that can cost tens of thousands of dollars, in some cases as much as the aircraft is worth, or more.
Retrofit economics shifted during the coronavirus pandemic, and the resurgence of demand for flight training aircraft is likely to maintain a trend that has seen many single-engine piston airplanes, including the most popular training aircraft of all time, appreciate in value—dramatically, in some cases. A recent price check on a 1986 Cessna 172P with 5,640 airframe hours in Vref (AOPA’s aircraft valuation service) returned an eye-popping estimate of $100,000 for this 35-year-old airplane that originally sold for $75,000. Many older models have increased by an even greater percentage of their original retail prices, and resourceful entrepreneurs are buying older Cessna 172s (in some cases sight-unseen) to refurbish and resell to flight schools clamoring for airframes.
For individual owners eyeing leaseback arrangements with a local flight school, or those just looking to upgrade their avionics to benefit from the many new features and functions made possible in recent years, digital drop-in instrument replacements are worth a look. They can deliver capabilities and features once reserved for large rectangular screen displays in a form factor that fits the panel you have, and that can lead to very significant savings on installation.
Simplicity is beautiful
Cutting square holes in round-dial instrument panels made for steam gauges adds significant time and expense to the installation process, to say nothing of the other complexities involved with antenna compatibility, available space, and wiring. So, let’s focus on what you can do with the round holes you already have.
Garmin’s GI 275 is factory configured to be one of many instruments. The attitude indicator version is listed online at $3,995 for piston aircraft that weigh up to 6,000 pounds. The HSI version is a bit more: $4,295. In both cases, the price listed online does not include installation.
The cost and complexity (time required) for installation depends on many aircraft-specific factors, and owners who consult their avionics installer before purchasing any instrument are likely to have a better and less expensive experience.
While Garmin’s digital round-dial solution can be much less expensive than a glass panel retrofit, uAvionix offers similar capabilities at an even lower price with the AV-30-C, first approved for installation in certified aircraft in 2020. The company based in Bigfork, Montana, founded and run by general aviation pilots, has been selling the $1,995 AV-30-C faster than it can make them, according to uAvionix Director of Sales Shane Woodson, who owns a 1968 Cessna 172.
“We’re building them as fast as we can get the parts and ship them,” Woodson said in a telephone interview. The company is working hard to reduce the lead time and current order backlog. “Right now, we’re several months out on deliveries … it’s been well-received.”
Simplicity is a key selling point of the AV-30-C, which is also available in an experimental aircraft version priced at $1,595. In each case, the instrument leaves the factory with flexibility to become many instruments in one. If used to replace one of the primary flight instruments (the attitude indicator, directional gyro, or turn-and-slip indicator), the primary function of the instrument is set and locked during installation. Additional information can then be overlaid on the screen, and that secondary information can be toggled by the pilot through many options, though the instrument’s primary function is maintained by the “function lock” performed during installation.
Installation ease is a significant selling point of the AV-30 models, even the certified version of which needs only four inputs: power, ground, pitot system, and static system. An inertial measurement unit (IMU) handles much of the rest; connection to a GPS source is an option, though not essential to supporting most of the instrument’s potential functions. Woodson said many AV-30 customers buy two and replace both attitude indicator and directional gyro with electronic versions, allowing removal of the vacuum system. The weight savings realized by ditching the vacuum system may be marginal, often around 20 pounds, but anyone who has ever had to repair or replace a mechanical vacuum system will appreciate that an electronic instrument without the moving parts can save significant cost while enhancing reliability.
Woodson said a typical AV-30-C installation requires marginally more shop time and expense than replacing the clock in an IFR airplane, and roughly one-third or less of the time required to install Garmin’s GI 275, the primary competitor. While the GI 275 installed as a directional gyro also needs external magnetometers, the AV-30-C does not, Woodson said.
“We’re driven to make products for the aircraft owners and the pilots to make it affordable … to make it easy to install,” Woodson said. “The shops don’t really love us as much,” he added, referring to the company's line of ADS-B transponders that often take even less time to install, but he counters that the lower revenue generated for the shop on each tailBeaconX or skyBeacon installation should be offset by volume. “The pure numbers and the turn of how many they get to do, by far makes up for it.”
Installed as a secondary instrument, the AV-30-C needs no function lock, and a long list of indications can be cycled for full-screen display, including probeless angle of attack. The pitot-static system combined with the internal IMU allows the AV-30 to calculate that. This instrument can also control the popular tailBeaconX ADS-B Out Mode S transponder, and that is also a certified GPS position source that can be used as the slaved true-heading source for DG and GPS HSI indications on the AV-30-C under an STC expected in the third quarter this year, uAvionix announced in May.
Additional functionality is now available for experimental aircraft (with STC approval expected to follow) in the form of the Wi-Fi module also announced in May. This AV-Link module attaches to the rear of the AV-30, allowing the instrument to connect to additional data sources and devices. Wireless firmware updates are one benefit; displaying a traffic overlay on the AV-30 is another. Enabling wireless connections will also allow the AV-30 to feed information to ForeFlight. “You could get pitot static data out of the panel into the iPad,” Woodson noted.
The company’s conversation with the FAA about AV-Link certification is still in a very early stage, Woodson said.
RC Allen options
Not every pilot wants to mix airspeed with attitude, and there’s another low-cost option to replace legacy steam gauges with digital versions of basically the same instrument, and even remove that vacuum system: RC Allen instrument options made by Kelly Manufacturing Co. are available for prices somewhat higher than the uAvionix AV-30 line, but with matching installation simplicity in reach for many. The FAA technical standard order RCA 2610-3 series digital attitude indicators start at $2,582 on the Aircraft Spruce website, ranging up to $2,945 for a version with pitot-static inputs, turn and slip indication, battery backup, and a pitch synch feature that allows the pilot to instantly synchronize the airplane symbol to the horizon line when flying in a pitch-up or pitch-down attitude.
The RCA 1510 series digital heading indicator is listed at $2,595 for the custom tilt version that can be factory-set at zero to 90 degrees. The RCA 1510 has an internal magnetometer but relies on an external GPS source, though it can continue to work if the GPS signal is lost, according to the online product description.
Beyond the six-pack
Avionics makers have digitized just about every instrument you can put in an aircraft, and many options are now available for the smaller holes (two-inch, or 2.25-inch) typically found in a legacy panel. These smaller round holes can accommodate a range of useful retrofits that turn single-function gauges into multifunction workhorses. Another uAvionix product, the AV-20-S, is among these. Announced in February, this $895 instrument can display a trove of data, including G-forces, angle of attack, attitude, temperature, voltage, density altitude, true airspeed, and time. Unlike its analog ancestors, the AV-20-S is also compatible with the tailBeaconX ADS-B transponder, and is FAA-approved as Non-Required Safety Enhancing Equipment.
Mid-Continent Instruments and Avionics released another 2.25-inch round digital instrument in February, aiming for a somewhat different market. The Flex MD23 Series is billed as the first “custom function display” available for both factory installation and retrofit, a single instrument that can become many things.
Unlike the Garmin GI 275 or the uAvionix AV-30, however, the Flex MD23 was not made with service in the six-pack in mind. It has no internal gyro, explained Ryan Reid, Mid-Continent’s chief pilot and manager of supplemental type certification and distribution.
“We’re kind of filling all the gaps around the attitude (indicator) and DG right now,” Reid said. The “custom” in “custom function display” requires a “custom interface definition” (CID) file that is created for a customer’s particular specification. There is currently no off-the-shelf version of this instrument, and those definition files can cost thousands of dollars. Once the CID is created, a process that can be completed in 30 to 45 days, the resulting instrument can then replace a broad range of “legacy gauges that you either wish you had, or want to enhance,” Reid said.
This bespoke instrumentation solution lends itself to aircraft makers as well as operators of relatively large fleets. Once created, the CID file can be replicated across a fleet, reducing the unit cost substantially. (The hardware retails for $2,000 to $4,000 per unit.)
Mid-Continent does offer one off-the-shelf option that may interest individual owners of legacy aircraft: the Chronos digital clock announced in May displays time (in local or Zulu), with integrated flight timing and stopwatch functions, as well as voltage monitor, outside air temperature, and secondary air temperature. It also comes with a pair of USB charging ports, fits in a two-inch panel cutout, and retails starting at $499.
