Story ID: 
S-tec, Avidyne team on glass panel
By: Matt Thurber
Caption: A partnership between S-Tec and Avidyne offers King Air 200 operators a large-display glass cockpit/autopilot upgrade, with FAA supplemental type certifica
Word Count: 1334
A partnership between S-Tec and Avidyne offers King Air 200 operators a large-display glass cockpit/autopilot upgrade, with FAA supplemental type certification expected shortly and deliveries to dealers beginning this quarter. The Alliant package should be the first large-display King Air system to receive an STC, althoughUniversal Avionics developed the first certified retrofit modern King Air LCD system.

The Alliant partners bought a 1980 King Air 200 and began installing the Avidyne primary flight displays and multifunction display and S-Tec autopilot in May, finishing in time to fly the upgraded King Air to the NBAA static display. S-Tec technicians installed the Alliant system at S-Tec’s Mineral Wells, Texas headquarters, removing as much as a net 150 pounds of original avionics and autopilot equipment. 

The Alliant package includes S-Tec’s IntelliFlight 2100 digital flight control system coupled with two Avidyne 10.4-inch Envision EXP5000 PFDs with integrated ADAHRS (air-data and attitude heading reference systems). It also includes one Avidyne 5.5-inch EX500 MFD, two magnetometers and Mid-Continent Instruments’ two-inch standby attitude, airspeed and altitude indicators. Price is $170,107, plus about $65,000 to $80,000 for installation. Radios are not included; the Alliant King Air had dual Garmin GNS530s, and many buyers of the King Air package already have compatible radios like GNS430s, according to S-Tec director of sales Greg Plantz.

Two hearts beat inside the Alliant package–the S-Tec 2100 digital autopilot and dual independent solid-state ADAHRS. The ADAHRS are built by Avidyne and communicate over the ByteFlight open standards databus developed by the FlexRay Consortium for automotive and aerospace applications. Except for the two magnetometers installed in the tail section, the cockpit system is fully contained in the MFDs and PFD installed in the panel. The MFDs are nine inches deep.

In the King Air 200, the Alliant installation puts the big Envision MFDs in front of each pilot. The King Air’s original engine instrumentation remains in place, just to the right of the pilot’s PFD. “It’s a much more streamlined installation,” Plantz said. Adding engine data and sensors to the avionics package would have made the STC much more complex and costly. In the right center of the panel are the two GNS530s topped with a Garmin audio panel, then immediately adjacent is the IntelliFlight 2100 autopilot, the 5.5-inch EX500 MFD and dual Garmin transponders. The standby instruments are mounted in the left side of the panel, next to the pilot’s PFD. The Alliant package includes Avidyne’s CMax electronic charts and MultiLink datalink system, which supports an XM WX satellite weather display. The EX500 can accept input from 19 radar systems as well as lighting, traffic, TAWS and EGPWS.

S-Tec is owned by Meggitt, which has developed its own glass cockpit displays and ADAHRS, but Meggitt equipment is not used for the Alliant package. The Avidyne/S-Tec partnership takes advantage of the core competencies of both companies, Plantz explained, marrying S-Tec’s digital autopilot expertise with Avidyne’s maturing large glass panel and ADAHRS know-how. S-Tec is an autopilot company and didn’t want to try to grow its own display technology, he added, even with Meggitt’s backing, but preferred to take advantage of Avidyne’s maturing large-display expertise.

During an NBAA-eve demo flight in the Alliant King Air 200 with former Raytheon test pilot Dwayne Clemens, the Alliant team showed off the system’s capabilities. Just a few days before NBAA, Clemens learned how to use the system, mostly during the flight from Mineral Wells to Orlando, which illustrates the system’s ease of use, Clemens said. Avidyne’s design philosophy is to minimize the number of buttons and choices, so that pilots don’t have to page through multiple menu layers to accomplish simple tasks. For example, after using a softkey on the side of the EXP5000 to change something on the display, the selection knob reverts after 10 seconds to the heading-select mode. Each of the functions that correspond to softkeys is available only when surrounded by a green outline, which signals that the adjuster knob can be used to change that parameter. There are no submenus like those on a Garmin G1000. A useful feature for a single-pilot airplane is the pilot priority switch, which locks out softkey control on the right seat PFD to prevent a rogue passenger from messing with the PFD controls.

The PFDs are used only to display instrumentation information, which is not combined with data available on the MFD. Traffic, radar, TAWS, airspace, weather, datalink messages and charts can be seen only on the MFD. While this simplifies the installation and makes for a much cleaner PFD, the smaller MFD makes viewing important data a little more difficult. To view an approach chart, for example, the pilot can either zoom in on the portion showing on the display or page through the four main sections of the chart one at a time. Another drawback to the CMax chart system is that charts are displayed only in north-up orientation, and there is no option to change to track-up. This should be something that pilots can select, especially for airport charts, which show an excellent view of the airplane on the airport but don’t allow track-up so the pilot has to do some mental gymnastics to interpret the view on the EX500. 

Avidyne eventually will offer its own radio system, but until then, having to look at the Garmin GNS radios sitting right next to the Avidyne displays introduces a little avionic-cognitive dissonance because the two manufacturers’ approach to cockpit displays is so different. It probably wouldn’t take long to get used to the Garmin/Avidyne adjacency effect, but this does add some level of non-integrative feel to the Alliant package.

Where the Alliant system shines is the autopilot integration. The S-Tec 2100 relies on two sources of ADAHRS input. If the autopilot sees that the two ADAHRS don’t agree with each other, it will shut off to prevent a “slowover” where the autopilot follows a slowly failing attitude input until the airplane is dangerously off course or in an unsafe attitude.

All autopilot annunciations are duplicated across the top of the PFDs so the pilot doesn’t have to look away from the PFD to check autopilot status. Adjustments to target altitudes have to be made using the knob on the autopilot, and this can’t be done with any controls on the PFDs. There is a slight delay between when the altitude is selected on the autopilot and when it shows up on the PFD. 

The 2100 autopilot includes airspeed and vertical speed hold modes, control wheel steering, GPS roll steering, yaw damper and normal autopilot functions. The altitude capture mode is especially smooth. At 1,000 feet above or below the selected altitude, a female voice announces the remaining feet and the autopilot gradually slows the rate of descent or climb. The voice announces again at 200 feet, and then the capture occurs with uncanny smoothness.

Clemens demonstrated the 2100’s capability by twice shutting down the King Air’s right engine, first in cruise to show how the system maintained heading perfectly during the shutdown, tilting into the good engine about 3 deg, then during a coupled ILS approach, when the autopilot again stayed exactly on the localizer and glideslope without a hiccup, then smoothly adapted as Clemons brought the engine back online. “Other autopilots you’d rock back and forth,” said Clemens.

S-Tec’s Plantz figures there are about 800 King Air 200s that qualify for the Alliant installation. The first customer installation began October 2, at S-Tec’s facility. Some dealers are already signed up, and Plantz hopes to have about 40 dealers worldwide for the Alliant program. The next target for the Alliant package is the King Air 90 series.