Sound of Ten Thousand "D'ohs!"

NORCAL: Cessna 123, verify you're direct ALTAM at this time?
Cessna 123: Not yet, we're still wrestling with our GPS ...

Never shy to point out the shortcomings in Garmin's 430/530/G1000 user interfaces, I'll admit I'm all excited to see the announcement of the GTN 650 (MSRP $11,495) and GTN 750 (MSRP $16,995) products. The 430/530/G1000 were, in a sense, a victim of their own success. So many units were sold that the user interface, as bad as it was, became something of a standard. Not unlike Microsoft Word, many of us got used to the dance of cursor-mode-big-knob-little-knob-enter and tended to forget how bad the user interface (UI) really was. To their credit, Garmin has done the sensible thing: Confronted with a bad UI that suffers from the Tyranny of the Installed Base, they started over from scratch with a touch-screen interface. While I've yet to actually handle one of these units, a lot can be gleaned from the videos that have been released and the information at Garmin's website.

Same Market, New Interface

The GTN 750 and 650 clearly target the aging GNS 530W and 430W, both in size and features. The new units provide the same basic stuff for aircraft owners and operators who want to freshen up their panels: Communication transceiver along with a WAAS GPS and VOR receiver as well as a moving map with some additional features.

Both units can provide an interface to remotely control a Garmin GTX mode C or mode S transponder. The GTN 750 can also control a remote audio panel. These interfaces to remote devices have the advantage of reducing the panel footprint, but the downside is that they can increase the complexity of the user interface. When a GTN unit becomes the single lens through which you access other important functions, the advantage of a smaller panel footprint doesn't look quite as attractive.

Why a different keypad? Why not one style of keypad with the 8 & 9 disabled for transponder use?

Out with the Old

A recurring problem with avionics designs is that, in an effort to reduce production costs, manufacturers are motivated to limit the number of buttons and knobs. With fewer knob and buttons, the UI designers must overload the function of those knobs and buttons: Depending on the state of the device (which is not always obvious), a knob or button will do different things. Overloading creates user interface complexity because the user must be cognizant of the device's state (which is not always obvious). One only has to witness a 100 different pilots experience the same UI frustration at high workload moments to know that overloading and convoluted, deep menu structures are B A D.

Manufacturers next tried to overcome the shortcomings in overloading by using softkeys - physical buttons whose displayed function changed depending on state of the device. The success of this was limited in the G1000, as an example, because different modes take control of different softkeys and the precedence is seldom clear. Try adjusting the flight plan on the MFD while the other pilot is using the lean-assist function and you'll get the feeling that there were different groups of programmers working on the different G1000 areas: They don't seem to have worked that closely with one another.

No Place like HOME


At the center of the new GTN units is a capacitive, touch-sensitive screen. There are just two knobs, two physical buttons, and an SD card slot (presumably for terrain and aviation databases). Grip points are provided on the sides and bottom of each unit so you can steady your hand in turbulence. And there are suggestions (but no details yet) on voice control features in the future, but for now the UI flexibility comes from having a touch-screen.

Both units clearly display the com and nav frequencies at the top of the screen. The active frequencies are at the top with the standby frequencies underneath. From the demonstrations it appears you swap the active and standby frequencies by tapping on the active frequency, which seems a bit counter-intuitive. Tapping on either standby frequency causes a pop-up a keypad to appear in the middle of the screen and you just tap in the new frequency. I hope there's an option for eliminating having to enter the leading "1" since all VHF nav and com frequencies are in the 1##.### range.

Different number keypad than for the transponder. Why?

The HOME button allows you to return to the main screen which is the starting point for a refreshingly simple and relatively flat menu structure. Unlike the subtle context indications in the 430/530/G1000, the HOME screen gives you a clear idea of the top level of functions. To access a function, just tap on the icon.


A dedicated Direct-To button is provided and this is a really, really good design choice because pilots, depending on your perspective, become creatures of habit or slaves to their devices.  In a high workload moment, there are few things worse than having an important button buried in a row of not-so-important buttons.

The knob in the upper left corner adjusts the volume and squelch for the com radio while the knob at the bottom allows you to change either the Nav or Com frequency. This a shame because the location of the bottom knob violates a basic UI concept: Whenever possible, physical knobs and buttons should be located directly adjacent to the display item they affect. If you need proof, witness someone trying to adjust the barometric pressure setting on a G1000 at a high workload moment.

Having a physical frequency selection knob means there are multiple ways to change frequencies. Alternate ways to accomplish the same task isn't necessarily bad, but it is something that earlier Garmin interfaces suffered from because some of the methods were Easter Eggs. Examples in Garmin's older interface designs? Pressing Direct-To once provides one feature while pressing it twice provides another feature. Or being transported into a hidden set of options when turning the small knob counter-clockwise (instead of clockwise) while in insert mode. If describing a user interface in words is this complicated, something in the design isn't right.

At the bottom of the screen are some icons for displaying system messages as well as a relatively small status line that tells you the GPS course sensitivity as well as which NAV source (GPS or VOR) is being displayed on the CDI or HSI.

Map View

The map view is similar to what we've become used to with the G1000 and one suspects it will offer similar options for North- or Track-Up, a compass rose ring around the aircraft, a fuel endurance ring. In one of the demonstration videos, the refresh rate of the map looked a bit slow. Not sure if this was an issue of the screen refresh rate interacting with the video camera's sampling rate or a limitation of the GTN's processor speed. I hope it's the former and not the latter.

Terrain, Traffic, Weather, Music, Intercom

The terrain features look pretty nice. And with the appropriate remote hardware installed, both units give you access to traffic and XM weather. Presumably TIS traffic data is available from a mode S transponder (for as long as the FAA radar sites continue to support it), from a dedicated transponder-based TAS system, or from the much vaunted (but yet-to-be-widespread) ADS-B facility that NextGen is supposed to have. If you choose the XM subscription that includes entertainment radio, you can access that, too.

One of the shortcomings of using the GTN 750 to provide an audio panel or other interface is that you lose the moving map when you access one of these features. The simple act of adjusting the pilot or co-pilot intercom volume will temporarily hide other features, like the moving map display with traffic, weather, or terrain data. It also appears to be a single point of failure: Lose the touch screen and you'll be hard pressed to change your transponder code, adjust your intercom volume, and so on.

One assumes that if there's an imminent traffic or terrain threat, that display will override any trivial function you might be performing. Hard to say without actually handling one of these units in flight.

Terminal Procedures and Taxiway Diagrams

Aeronav and Jeppesen charts can be displayed on the GTN 750, but the size is pretty small and requires scrolling around. Geo-referencing is offered, though the subscription costs tend to be high and much more cost-effective options are available on the iPad or other off-the-shelf consumer devices.

Crux of the Matter

With all GPS designs, the ease with which one can enter and modify a flight plan is what makes or breaks a user interface design. While there are many pilots out there who just fly VFR and only use Direct-To, there are IFR pilots who'll need to enter a sequence of waypoints that match the clearance they just got from ATC.

Assuming you have a steady flight path, the GTN 750 lets you enter waypoints into your flight plan by simply tapping on their representation on the moving map. You can also enter waypoint using a pop-up keypad. No more singing the alphabet as you scroll through adding a waypoint with the big-knob-small-knob interface. Last but not least, you can drag an existing flight plan course line on the map to add a new waypoint to the flight plan. I'll have to use this in person before I can say whether it rocks or is just more usable than the old big-knob-little-knob interface, but these flight plan features alone may be worth the price of admission.

With the GTN 650's small screen, there's an odd kludgey selection process. Bummer about that ...

Grace Under Pressure?

My initial research hasn't turned up any examples of  loading procedures and I'm particularly curious to see if the vectors-to-final behavior has been improved.

Simulator, Please!

One of the really smart things that Garmin did with the 430/530 was they made a PC-based simulator available to download at no charge. It is my contention that having a simulator to practice with was one of the driving forces behind pilots' and aircraft owners' widespread acceptance of the 430/530 series. As of this writing there is no such simulator available for the GTN series. Surely Garmin will see that it is in everyone's best interest to provide one. Soon.

A New Leaf

As to whether or not these units are a good deal or attractively priced, I'll leave that assessment to the aircraft owners and other pundits out there. After all, I'm but a humble, professional flight instructor and freelance writer who rarely has more than a couple of coins to rub together and the mere prospect of owning an aircraft is beyond my ken. Garmin doesn't invite me to their media events, so I've taken an academic yet honest approach in this review because I hope this is what my readers have come to expect. I'd certainly like to fly one of these units in the near future, perhaps even train the next wave of instrument pilots to use them. Who knows, maybe the introduction of the GTN series will transform the sound of 10,000 pilots crying D'oh! to the sound of a single Ommmmm ...