Ken Lince & Louis Wang
9 June 2020
From £2,754
Garmin recently released the GI 275, a line-up of retrofit EFIS instruments designed for standard 3-⅛in round gauge cutouts. Compared to the Garmin G5, the 275 has full US TSO certification and can be configured to display an array of ‘steam gauge’ functions. It has a capacitive touch screen, built-in WiFi and Bluetooth for easy system updates and upgrades with expected compatibility with the Garmin Pilot EFB application. The 275 is an extremely flexible unit as it can be configured as a simple attitude indicator or as a 4-in-1 flight instrument displaying tapes for airspeed, attitude, altitude and heading.
The GI 275 comes in several variants to support all of these functions. The GI 275 base variant can be utilised as a dedicated EIS or CDI/MFD, with features such as traffic, weather, terrain, SafeTaxi® airport diagrams and more. The GI 275 ADAHRS includes a built-in ADAHRS and back-up battery, making it capable for use as a dedicated 3-in-1 flight instrument with attitude, airspeed and altitude. When connected with an optional magnetometer, this variant can serve as a dedicated HSI or 4-in-1 flight instrument with attitude, airspeed, altitude and heading information.
The GI 275 ADAHRS+AP is also available, which includes the capabilities of the ADAHRS unit, and adds the ability to interface with a wide range of legacy autopilots, including those that require an attitude source like King and Century. With native support for the digital GFC-600 autopilot and expected support later in 2020 for the GFC 500, the 275 offers an incremental upgrade path to fit different needs and budgets.
As a horizontal situation indicator (HSI) you have the option to overlay a moving map with traffic and weather information. As a multi-function display (MFD), high-value information is at your fingertips, including a moving map, weather and traffic. As an engine information system (EIS) it can consolidate your engine gauges and collect data for later analysis. When installed as a back-up device it can function as a VFR navigator – a great feature if you’re upgrading a VFR-only aircraft. Lastly, the GI 275 can be configured as a simple CDI.
When installed as a CDI or HSI, the GI 275 is designed to accept a variety of GPS or navigation inputs, allowing up to two GPS sources and two VHF navigation sources. The GI 275 features an Omni Bearing Resolver that allows the flight instrument to interface to a variety of legacy navigators on the market without the need for an expensive adapter. With an optional magnetometer, it is also capable of providing magnetic-based HSI guidance. Vertical and lateral GPS, VOR/LOC and glide slope deviation can be viewed on the GI 275.
Another great feature is Synthetic Vision. It’s not included as a standard feature in any of the GI 275 variants. However, as soon as the device gets installed, you will get 10 flight hours of free Synthetic Vision. Once they expire, if you wish to continue having Synthetic Vision enabled, there is a feature enablement that must be purchased through an authorised Garmin Dealer, or at https://fly.garmin.com/fly-garmin.
In our Mooney M20K, we set out to replace the attitude indicator and HSI while keeping the Century 31 autopilot. Our vacuum attitude indicator was failing, which also caused the otherwise functional autopilot to perform erratically. Several options were considered – from replacing the AI only, to a new glass panel with a new autopilot. In the end, we decided to keep the Century 31 and install dual GI 275s. It was the best balance between our priorities – budget and future upgradeability. Because the 275 was able to drive the autopilot, the vacuum system was no longer required and could be removed – a big plus when flying an IFR machine. If we decide to upgrade to a glass panel at some point in the future, then the GI 275 could be repurposed to display other information.
Our primary attitude indicator is configured to be the primary airspeed, altitude (including vertical speed) and heading indication. The second unit is configured as a primary HSI and back-up attitude indicator. The optional GTP 59 OAT probe enables ‘standard rate turn’ markers on the ADI, allowing us to replace the electrically driven turn coordinator as well. The dual GI 275’s consolidated six flight instruments down to two – each with its own 60-minute back-up battery. Since the back-up battery drives all of the GI 275 probes the only other required flight instrument for IFR flight is a magnetic compass.
Navigating through the menus of the GI 275 can be performed using the single knob, with an outer collar and inner knob and push-button functions. Most of the menus are touch enabled, and familiar gestures such as swiping and pinch-and-stretch are recognised. If you’re familiar with the GTN 650 or 750, then you’ll feel right at home.
One very exciting feature provided by the GI 275 with the autopilot integration is GPSS Heading Emulation – or roll steering. GPSS steering allows the legacy autopilots to track GPS courses precisely, including the ability to fly arcs, procedure turns, course reversals and holds. While we’ve found that GPSS emulation performs well, one criticism we have with the implementation is that the option to change from standard HDG mode to GPSS mode is buried three layers deep in the menu. When GPSS mode is enabled the autopilots HDG mode is unavailable. This means that if you are using GPSS mode and need to deviate quickly from course to avoid traffic or weather, you need to hold the button down for a few seconds to bring the menu system up, then touch the screen three more times to switch back to HDG mode so you can use the HDG bug in the traditional way to turn the aeroplane to a vectored heading. We’ve found in practical flying that it’s not really a big deal. Ideally, in the terminal area you are in HDG mode for vectors and then once en route you switch to GPSS mode and let the autopilot fly the turns for you. It’s worth noting that we’ve brought this to Garmin’s attention. There are 70+ pins on the back of these units – our hope is they allow installers to use a pin or two and give them the option to install a simple push button on the panel that quickly switches between GPSS and HDG mode. It would be an ideal solution. It’s all software, so we’ll see how Garmin responds.
The only required maintenance for the GI 275 is a battery check each year, ideally at annual, and a navigation database update is required at least once every five years to correct for magnetic deviation. The navigation will be more accurate if the database is updated periodically – and like all Garmin products a subscription is required – but it’s not required for continued airworthiness.
The extensive features of the GI 275 give new life to older avionics, offering real improvements to flight safety, while reducing IFR workload. Paired with its classic looks, plus the amazingly sharp, and glare-resistant, screen, it makes for a compelling upgrade for a wide range of aircraft – from a Piper Cub to a warbird and others in between.
Base price for the GI 275 starts at $2,995, with the EFIS starting at $3,995, and EHSI from $4,295.
Our dual configuration installation in our Mooney with autopilot integration, Garmin 430W integration, audio panel for aural alerts integration, GTP 59 OAT probe and magnetometer was around $16k, including labour costs.
