Cheap glass-not the kind you look through but the stuff that occupies the high-rent district in the panel of modern bizjets-is the recurring dream of many an airplane owner.
Unfortunately, if youve spent your way to avionics nirvana with affordable navigators, comms and instruments, the path to true EFIS enlightenment is likely to cost several times the value of your entire airframe, if you can even find a suitable system for a tight panel.
Sooner or later, that had to change and a modest start-up California company-Sandel Avionics-appears to have crossed the boundary into truly affordable glass with a terrific electronic HSI/multifunction display called the Sandel SN3308, which was recently TSOd and is now shipping.
The big breakthrough: Unlike traditional big iron systems which use heavy, multi-tube CRTs-hence the term glass-the Sandel instrument uses a clever and compact light projection design that allows it to fit into a chassis not much larger than a conventional HSI and to sell for $7895, a price tag thats competitive with a conventional electromechanical HSI
We had a look at the Sandel instrument in a Bonanza used as a test bed. Although we werent able to fly the unit, Sandels marketing manager, Steve Bennett, demod the unit in full. Here are our impressions.
In a sense, Sandel is playing Monopoly with the standard T-panel, focusing on two hot properties, Broadway and Park Place. Broadway is the top of the T in your scan-the attitude indicator or the flight director. Park Place is where youll find a DG in most airplanes and an HSI in high-performance aircraft. Sandel aims to fill that space with SN3308s.
In a nutshell, the SN3308 combines data from various sources into one highly customizable screen. Its not really an HSI because instead of relying on a gyro floating in gimbals, the display is electronically projected based on data from remote sources. Many remote sources.
While an HSI is limited to heading, course and vertical guidance from glideslope flags, the Sandel can superimpose those basics plus a lot more.
Nor is it like supplemental systems from Argus and Avidyne, because the Sandel was specifically designed to fit into the main panel and to legally replace a required DG or HSI.
The SN3308 accepts heading data from a flux gate or DG, nav data from VOR, GPS, loran, ADF, RMI, DME and marker beacons, message flags from GPS and if you want, it will even display weather data from a remote Stormscope WX-500 sensor and radar altimeter data.
Thats a lot of stuff and its all combined on a tiny color LCD at the back of the unit, then projected-using a small but very bright halogen bulb-towards a flat black screen through a prism and a series of mirrors and color splitters. The principle is similar to one of those large projection televisions. What you see from the front is a full nine square inches of multi-color display-twice the display area of an Argus 3000 but with the graphics quality of an Argus CE color map.
Whats behind the screen? Nothing. At least not in the middle. Since this thing is like a little rear projection movie screen in your panel, Sandel had to keep the light path clear, thus the circuit boards that process the data line the perimeter of the unit. The two control knobs connect viauniversal joints and metal rods to pots at the back of the box. Just as on an HSI, the left knob adjusts the D-bar/course line and the right sets the heading bug.
But unlike a conventional HSI, there are nine control pushbuttons that line the perimeter and connect via translucent tubes to microswitches on the sides of the circuit boards.
The daytime white-on-green letters automatically reverse to black-on-white at night. Theres also a separate brightness control that mounts on the panel near the instrument.
The brightness control may be every bit as important as all those buttons. Reducing the brightness dramatically extends the life of the projector bulb and therein lies this instruments potential Achilles heel.
Other than the knobs and buttons, the only other moving part is a cooling fan and it had better keep moving because its there to keep the bulb from frying. Lose the bulb and there goes your HSI and everything else youve tied into the gadget. Theres no redundancy.
Sandel has gone to extraordinary lengths to protect the bulb from premature burn out. Sandels Bennett told us that most bulbs fail at power up because of the thermal shock of instant filament heating.
Sandel designed the SN3308s power system to slowly ramp up the voltage on the bulb to full brightness. (Slowly is a relative term here. It still happens in the blink of an eye, but its slow to a cold filament.)
Sandel expects bulbs to last more than 400 hours at full brightness. But just to give the pilot a heads up, the instrument monitors its bulb life with a little gauge, like a battery-life-remaining gauge on a laptop computer which indicates how much is left. So if you were planning to leave for a two-week trip, you could replace it before you departed. How hard is that? Not a major operation but the device does have to be removed from the panel to get at the bulb through a small topside access panel. Not a two-hour job, but not five minutes, either.
If the fan fails, the SN3308 would know it and would ration the bulbs brightness to keep it from overheating. Sandel says they know of only one bulb failure incident and they attribute it to a botched installation in a helicopter. The unit was re-installed properly and has worked fine since.
Even though they expect to get 400 hours at full brightness, Sandel is initially recommending bulb replacement at 200 hours or annually, whichever comes first. And, like an engine TBO, favorable operation experience may increase the TBO as units in the field establish a service history. Initially, Sandel pledges to provide free bulbs for TBO-replacement but the bulbs themselves are cheap.
Its All There
Sandel has managed to combine an astonishing amount of data onto a single screen that still serves as a basic HSI. That said, our impression is that its both well organized and selectable in such a way that the instrument face can be de-cluttered at will. Data from each source has its own color and display area. VOR 1, for example, is always green and shows up on the bottom left of the instrument while VOR 2 and ADF is always yellow and shows up on the bottom right. (What you see is the navaid ident and bearing TO or FROM.) GPS information is blue and displays across the top, to include the basics such as bearing, track, distance-to-go and groundspeed.
DME and ADF info is yellow and appears at bottom right. Bearing pointers from each source are color-coded to match. The heading bug is orange and like any bug, it shows up where you put it. The instrument offers several views. The so-called 360 view puts the airplane icon in the center of the screen and lets you see whats behind you. Its the view were most accustomed to on GPS moving maps.
Jabbing the VUE key switches to what Sandel calls the ARC view, sliding the airplane to the bottom of the screen with a 90-degree-wide window looking ahead. Turn the airplane and the 90-degree window turns with it, repositioning the moving map features-navaids, airports, weather display-as it goes.
The HSI compass card is superimposed over the map features. This is the view youd be used to if you wear shirts with stripes when you fly, since its very similar to a typical airliner glass cockpit display.
A dedicated A-B key swaps between two of the SN3308s snapshot memories. This is a convenient way to switch between two complete sets of display settings. Any changes in VUE setting, map range, or bearing pointer selection are automatically saved when A-B is pressed and are restored when A-B is pressed again, meaning you can set-up and toggle between your favorite configurations.
A pair of UP-DOWN arrow keys toggle the map scale from 1 mile to 1000 miles, with a dozen discrete values in between, plus an auto-scale. The unit is customizable in flight by pressing the SHFT button and accessing a set of sub-menus, to include soft keys for setting up GPS functions, to name a few additional capabilities. Operationally, we found it no more difficult to use and set-up than any panel-mount GPS and probably a little simpler, since the A-B function allows storing and quick retrieval of often-used displays.
Sandel included a DME hold feature to accommodate the fact that many high-end DMEs let you channel from the nav receiver, then change nav frequencies while still showing the first DME. The SN3308 receives that signal from the DME and depicts the H when the DME is in hold.
For typical en route flying, youd probably use a blue (cyan) display of your course line, imposed over a white-on-black moving map containing your flightplan waypoints, with lightning strikes showing up as green plus symbols on the map. (Sandel thought crosses registered better than dots so the crosses will remain. We wouldnt be surprised to see other weather display features, such as color coding for strike intensity.)
One other neat feature: The marker beacon uses the same space-just above the right knob-for all three signals. Why not? The software can make it flash whichever color and letters are appropriate for the location. Pretty slick.
Source selection can be done in two ways. The 3308 can function in master or slave mode. In master mode, pressing the NAV button cycles through NAV 1, NAV 2, GPS (or loran), depending on whats installed. You describe the installed equipment in the set-up pages. The SN3308 outputs a discrete logic signal for each source when its selected. These outputs are used to control an external relay or a series of cascaded relays if switching between more than two sources.
In slave mode, the NAV button does nothing. An external switch (usually pre-existing) does the source selection and the SN3308 reads the state of that switch to depict the correct source label. So if you switch externally between VOR 1 and VOR 2, the SN3308 will annunciate the source and change colors correctly.
Interesting technical issues arise when combining data from sources that were never designed to handshake. For instance, depicting a VOR radial on a GPS-generated map means correcting for the magnetic variation of one and the station declination of the other. Theyre working on solutions for such idiosyncrasies.
With all this data available, its easy to clutter the screen to a state of uselessness, so Sandel includes some filters. These buttons let you select which data you want to appear on the screen. There are four basic map settings for data gathered from the GPS: Current waypoint only, current waypoint, flightplan and nearby waypoints, current waypoint, flightplan, nearby waypoints and fixes and everything off, in which case the instrument functions as a plain HSI, but with basic numerical nav data in digital form.
There are two levels of detail for GPS outputs: All GPSs with an RS-232 output send the current waypoint and flightplan data at 9600 baud. GPSs with ARINC 429 output (King KLN 90B, Trimble 2101 and the entire Garmin family) use a high speed datalink that adds additional nearby waypoint information which can be displayed, if desired.
Its at this juncture that the type of equipment you already have begins to matter. Especially with regard to current database information. Like every other piece of new gear it seems, the Sandel has an appetite for data. If youre flying a GPS with RS-232 output, the moving map detail will be limited by the GPS output. If you want additional detail, youll have to buy a database from Sandel. (Current models are shipping without databases and no prices have yet been established for data revisions.)
Owners with ARINC 429 output might prefer to let the SN3308 repeat that nearby waypoint information and not buy yet another database, which would otherwise be required. Owners who file IFR often and who dont care about special use airspace, might prefer to buy NOS data, when and if it becomes available for the Sandel instrument. But if you want the unit to display SUA, youll have to buy Sandels database.
Since removal of the unit every 60 days is impractical, the Sandel installation kit includes a phonejack dataport in the panel to allow data revisions from the pilot seat.
To get the most out of the Sandel, you have to be able to send it all that data in the first place. Lets start with the SN3308, which lists for $7895. Expect to pay another $1500 to $2000 for installation and field approval. (Lots of wiring involved here.) Call it under $10,000 for many installations.
With new electromechanical HSIs installing for about $7000 and up-way up for the Bendix/King system-we have to say that a five-color EFIS system in a 3-inch box for under ten grand is highly competitive. And this one will be able to add new features through software, which no HSI can match.
Sandel designed the SN3308 as a direct replacement for the Bendix/King KCS 55A, but it accepts remote gyro and flux gate compass info from any source. If you dont already have an HSI or compass info to send to the SN3308, add another $4000 for a remote gyro and another $500 for the flux gate to keep the HSI snuffed up and on course. In that case, the total nut will run close to $15,000.
The Sandel will display whatever data the GPS can send it, so ARINC 429 models (listed above) will give you more to look at on the moving map. But even the lowly RS-232 models will send enough data to be useful when blended with the other inputs. That little GPS message flag can tend to get lost during a busy approach, so having the repeater light on the SN3308 is a plus.
Owners who have already plunked down the dough for a big-screen Stormscope might be unwilling to duplicate that screen only inches away. But the ability to overlay lightning dots against waypoints and course lines might be too enticing to resist so switching to a WX-500 may be both economical and smart. It will also open up some panel space.
The radar altimeter wasnt implemented in the unit we examined but heres how it will be integrated: When the altimeter becomes active-usually below 2500 AGL-a sliding tape display will appear on the left side of the HSI, opposite the glide-slope with a DH annunciation on the screen. The DH will be set using the SHFT function.
The unit operates on 11 to 33 volts and with no gyros or gimbals, it weighs a scant two pounds. It draws less than 5 amps and needs 10.65 inches of clearance behind the panel.
Frankly, we found the Sandel SN3308 to be one of the most well-designed pieces of equipment weve seen in quite some time and at around $10,000 installed, its a fair value. Not bargain basement, but very competitive with a new HSI installation, yet offering considerably more capability and upgradeability as new software becomes available.
The fact that its certified to replace a legally required instrument gives it a real leg up, value wise, over pricey systems such as the Avidyne, Argus or ARNAV multi-function display.
Our only reservation is durability. Only a year or two of operational experience will confirm whether the bulb/projector design is suitable for the rigors of the average GA cockpit. This is by no means a showstopper, but we are somewhat concerned about surprise failures that would darken the instrument in the blink of an eye. A back-up conventional DG wouldnt be a bad idea.
The bottom line here may just be the bottom line. Is $10,000 a reasonable expenditure for a glass HSI? We think it is. Compared to developing display options for the small GA cockpit, the Sandel is available now and is TSOd for replacement of required instruments. Unlike the multi-function displays, its not wait-and-see technonology
In our view, Sandel has a winner.
Contact- Sandel Avionics, 2401 Dogwood Way, Vista, CA 92083; 760-727-4900; http://sandelavionics.com.
by Joe Godfrey
Joe Godfrey is a writer, musician and aircraft owner. He lives in Leucadia, California.