Avionics: A New Class of Glass

When it comes to glass, not everyone is in the same class. New-aircraft manufacturers offer customers several different varieties of glass cockpits, and new glass cockpit retrofit options are becoming available for older piston airplanes. But those flying legacy jets and turboprops find fewer options. Garmin and Avidyne offer all-up, slash-and-burn complete panel upgrades for a few models of older turbines, but your average Cessna Citation II or Piper Cheyenne or Falcon 100 pilot is still staring at 1970s-era, mechanical displays.

These older airplanes still offer plenty of performance and good values, but their complex panels, systems, and autopilots make complete retrofits a difficult and expensive proposition. In fact, the cost of a complete panel remake may equal the hull value of some of those Jurassic jets.

With the intent to do in the turbine world what he did in the piston world a dozen years ago, Gerry Block went to work on a solution. Block formed Sandel Avionics in 1996 to market his original SN3308, an electronic horizontal situation indicator meant to replace mechanical HSIs. For about the same price as a conventional instrument, the SN3308 offered a number of new features, including airspace, traffic, and weather depictions; route overlays; and other moving map capabilities. An unusual light-projection system powered the display. The three-inch unit was a plug-and-play replacement for several popular mechanical HSIs.

Today’s version of the product is the SN3500. The bulb is gone, replaced with an LED projection system. In addition, Sandel has enjoyed turbine market success with its ST3400 terrain awareness and warning system (TAWS)—a low-cost Class A and Class B TAWS brought to market just as larger turbine airplanes were required to equip with TAWS.

With that market niche filled, Block, a classic inventor and tinkerer, found his next challenge right in front of him. The complicated HSI and attitude gyros in his Citation II panel seemed always in need of maintenance and they didn’t provide much information.

Block’s solution is the SA4550 primary attitude display and SN4500 primary navigation display. The displays are pin- and plug-compatible replacements for a number of Sperry and Collins systems found on turbine airplanes produced in the 1970s and 1980s. Last fall, Sandel released an FAA-approved model list (AML) covering installation of the displays in dozens of Sperry-equipped turbine airplanes from Gulfstream IIIs to most King Airs. The company expects to release an expanded AML covering many Collins installations this spring.

Bright light of innovation

In an effort to keep costs down, Block employed recent advances in LED projection systems found on high-end televisions. The resulting cockpit displays are highly readable in all lighting and across wide viewing angles. Sandel claims they are viewable 180 degrees both horizontally and vertically. The patented displays boast an estimated mean time between failure (MTBF) rate of 10,000 hours and a two-year warranty. Our flight in Sandel’s Citation II showed excellent resolution, readability, and viewing angle.

Whereas the original mechanical AI shows the usual blue sky and brown earth with chevron flight director command bars, the Sandel system brings several new features to the panel. Pilots have a choice of flight director command bars or cross pointers. Annunciators show various autopilot mode settings. A skypointer helps orient the pilot. A localizer deviation indicator is depicted across the bottom of the display and glideslope indications down the side whenever an ILS is tuned. The bottom left corner houses a selectable minimums window; the bottom right corner is the radar altimeter display. When tied to an angle of attack system, the display shows a Fast/Slow scale on the left side. If the airplane is too fast on the approach, a magenta circle moves up the scale toward the F, for fast. If the circle moves toward the slow indication, the airplane is going too slowly.

A series of magenta chevrons point up whenever downward pitch attitude exceeds 20 degrees; downward-pointing chevrons appear when pitch-up attitude exceeds 30 degrees.

Both the 4550 and 4500 come in a standard 4 ATI size common on such airplanes, providing a four-inch display. A 5 ATI format is available for those wanting a five-inch display.

Like the three-inch 3500, the 4500 ND can be configured to show a variety of nav data, including flight plan routes and waypoints. The display accepts information from most popular traffic detection systems. Weather overlays can be created using Stormscope information or satellite datalink weather from WSI and XM Satellite. Next waypoint identification and bearing and track to it, as well as distance, can be displayed along with groundspeed.

Dedicated bezel buttons control the traffic and weather overlays as well as the bearing pointers, map settings, and navigation information. One touch of a button reduces screen clutter.

The SA4550 attitude display and the SN4500 navigation display each sell for $20,950.

Next up

Sandel started shipping another new product in mid-February, the SG102 solid-state attitude heading reference system. Certified for use as a primary heading reference, it can be used in conjunction with the SN4500 for heading input or to upgrade conventional mechanical directional gyros, such as the Bendix/King KG102A. The SG102’s pitch and roll output can be used for stabilization of radar antennas, FLIR cameras, and other such equipment. Like the displays, the SG102 has a MTBF of 10,000 hours, providing a much greater level of reliability than mechanical gyros. The SG102 sells for $4,495 for piston airplanes; the model for turbine airplanes and helicopters lists for $5,495.

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