My plane will be all electric. There will be no vacuum system whatsoever. This is turning out to be a common choice in homebuilts because of the complexity and unreliability of vacuum systems. It does, however, put additional importance on having a reliable electrical system. I will be following the design ideas of Bob Nuckolls, author of "The Aeroelectric Connection" to build a reliable and redundant electrical system which is also simple and lightweight. The basic concept of the system is to assure that no single failure will keep me from reaching my destination. I will write more about this later.
I will not have any mechanical gyros on my plane. In production planes you typically have two gyro-stabilized instruments, the attitude indicator and the gyro compass. These are typically powered by the vacuum system, but can also be electric. They are heavy and expensive. They are also inflexible and outdated. In the 21st century there are better options.
When it comes to the design of the instrument panel, I want flight information quickly and easily readable. I want integration as much as possible with the PFD, the radio, the GPS, the engine monitor, and the autopilot. I also want the panel to be clean and uncluttered. Finally, I want to take a redundant systems approach where it is practical.
* I want a VFR "Plus" panel
* The panel should be optimized for cross-country flying
* I want as few instruments/components as possible
* I want as few switches as possible
* I want to be able to enhance the panel over time
* I want to be able to adjust the altimeter in only one place
* I want to take advantage of interoperability between components when possible
Because I am not using a mechanical attitude indicator, I decided long ago that my panel will include some type of electronic primary flight display, or EFIS. I have come to trust electronic components much more than I do mechanical ones, and I really like the way a good EFIS can make you a safer pilot. Currently I am investigating three options:
Initially I had planned on using the Dynon D10. It is lightweight, inexpensive, simple, and reliable. As I researched, however, I found that there are some things that I can't do with the Dynon that I really think are important. The Dynon doesn't interface with other components, other than supplying encoded altitude to the transponder. I want more integration. I want a certain level of synergy in the cockpit, rather than a big collection of individual instruments.
When I was looking at using the Dynon, I envisioned my panel having a D-10 centered in front of me with two or three backup instruments around it for redundancy. I planned to have a separate engine monitor provide secondary flight data in addition to engine information. When Dynon announced their upcoming engine monitor product, I was naturally interested, since the two units allegedly work together in some way, and could possibly reduce my need for the redundant instruments.
One thing I learned about the Dynon is that it bases all of it's flight information on pitot/static and magnetometers. While this is great compared to, say, an expensive collection of mechanical gyro instruments, it lacks the accuracy of the GPS-stabilized information presented in some of the more expensive systems. It also can't, for example, calculate wind direction and speed for you, and it obviously cannot integrate GPS navigation information into the display.
A less important issue is the interface. I like to be able to turn knobs to adjust things like barometric pressure, etc. The Dynon uses pushbuttons. I guess I could get used to it if I had to, but I would prefer a knob.
Grand Rapids Technologies EFIS Horizon Series 1
My exposure to Grand Rapids Technologies has been through a friend who has installed their EIS4000 engine monitor on his Sonex. It is a simple and reliable device which accurately displays and monitors engine information. Recently this company has expanded their product offering to include an EFIS, and I had a chance to check it out at Oshkosh back in August.
While the GRT unit is more expensive than the Dynon, it offers several advantages. The most important being the level of integration between a wide variety of cockpit components, including engine monitor, radio, gps, transponder, and autopilot. This interconnectivity can provide a level of synergy which makes the whole greater than the sum of it's parts. I'll explain more in a moment.
The GRT unit has a much larger display than the Dynon. The unit can display in several modes, and can even be split, allowing two screens to be displayed at once. The four display modes are: Primary Flight Display, Moving Map, Engine Monitor, or Split Screen. The PFD can be configured to always display a set of important engine information, such as RPM and Manifold Pressure, but it is also nice to be able to see a graphical display of engine information at the touch of a button.
I am a big fan of analog depictions of data whenever possible. To me a bar graph or analog meter is much more readable than a digital number. That's one of the things I didn't like about the EIS4000 engine monitor. Just about everything is displayed as a digital readout. That limitation is addressed very nicely on the GRT EFIS. The engine monitor information is displayed in a nicely formatted analog display. This information can occupy the entire screen, or it can be one half of any split screen. Very flexible.
The GRT EFIS is a 2D display. Depth lines are used to indicate a vanishing point on the horizon. There is no terrain information currently available. Although I don't know this for a fact, I would expect that the processor in this unit is probably not capable of displaying a 3D terrain even if it became available in the future.
The moving map is probably the weakest of the display options. I have a Garmin 196 handheld gps, and it's display is more functional and readable than the moving map on the GRT EFIS. They use a public domain database for their map, and the visual representation is limited to lines and circles. It reminds me of the early GPS displays on some old panel mount Garmin radios. They may be working on this, but at this point it is a limitation. It is a nice backup to an external GPS, however.
One really nice feature of the PFD is that it overlays navigation information on top of the artificial horizon, either as a set of HSI needles, or as a highway in the sky. I think this could be really advantageous. The navigation information can come from either the GPS or from a Nav radio. A glideslope from a localizer can be displayed as well, I believe.
This illustrates an important feature of the GRT unit. It can communicate with the Garmin SL-30 in two directions. In addition to being able to set frequencies on the SL-30, it can display information from the SL-30. Integration is good.
GRT has announced that their unit will display traffic information from a Mode-S transponder, like the GTX-330. They have also indicated that they will be adding Satellite Weather display. It is nice to know that the system is expandable.
Finally, GRT recommends using a TruTrak autopilot, which their unit can control.
Blue Mountain Avionics - EFIS/Sport
Blue Mountain has a full-blown, all-in-one, big screen EFIS that does everything. I like it a lot, but it is expensive, so I haven't really considered it for my plane. Maybe in my "next" plane!
At Oshkosh they demonstrated a smaller version of their EFIS which seems like it might fit my needs. It is less than half the price of their big product, and it does most of the functionality, except for engine monitoring.
The BM EFIS is a robust system that, like the GRT product uses an AHRS for navigation accuracy. The new, smaller unit uses the same stuff, so technically it should be the same.
There are, however, some limitations to the amount of integration this smaller unit is capable of. It only has one serial port, so you must decide which "thing" you want to communicate with. Fortunately, the unit has it's own built-in GPS receiver, and the BM autopilot connects through a different interface, so I believe the decision would come down to whether you want to connect to the radio or the transponder.
As I said before, there is no engine monitor functionality on the Sport unit, so a separate engine monitor is required.
The technology inside the BM product is certainly impressive. It is capable of displaying a synthetic vision display of terrain ahead of the plane. The moving map display is also high-resolution, and displays terrain. This unit also includes an HSI display which lets you fly IFR approaches. I am not instrument qualified, so I can't tell you anything about this feature, other than it's there.
Actual features of the Sport seem to be in a state of flux at this time, and documentation on their website is out of date, so I think I will wait and see what pans out with this unit. It definitely looks impressive, but I'm not sure of it's limitations with regards to communicating with other devices. Also, having a separate engine monitor adds to the cost of the overall system.