With FAA mandate looming, L-3 introduces a class-B TAWS

 - October 8, 2007, 9:10 AM

L-3 Avionics Systems, the former Goodrich subsidiary that produces the well known Stormscope and Skywatch lines of cockpit safety systems, last month introduced a new class-B terrain awareness and warning system (TAWS) that the company said will have a list price of $12,500.

The Landmark TAWS 8100 hits the market just in time for next spring’s requirement for most turbine-powered airplanes to start carrying approved terrain alerting avionics. The TAWS 8100 includes a graphics adapter that allows the unit to be used with a variety of EFIS and radar displays and an external GPS receiver. L-3 Avionics Systems plans to unveil the new product later this month at the NBAA Convention in Las Vegas.

According to the manufacturer, the TAWS 8100 can be purchased with a database covering North America (the U.S., Canada and Latin America) or the entire world. The database includes all airports with runways 2,000 feet or longer. Terrain alerts and algorithms are the same as those for the previous class-B TAWS 8000 system, with a major difference being the TAWS 8100’s WAAS GPS receiver, used to determine location as well as altitude. In the North America database, the TAWS 8100 system includes all man-made obstructions taller than 100 feet. Jeppesen supplies the terrain, obstruction and airport information.

The TAWS 8100 remote processor measures 7 inches tall, 2.25 inches wide and 9 inches deep and weighs less than four pounds. It connects to aircraft sensors and systems and cockpit annunciators and the audio system. The processor also contains the TAWS database, which is output to the graphics computer for display in the cockpit. Also included is the FreeFlight Systems GPS receiver and antenna. Unlike the TAWS 8000 system, the 8100 relies on altitude information from this GPS receiver rather than baro-corrected altitude.

The system includes all the standard terrain alerts and callouts and can operate at speeds up to 900 knots. It looks far ahead of the aircraft along a narrow, 0.25-nm-wide track, but opens its look-ahead aperture in turns based on the rate of turn. The system issues a caution 60 seconds from possible impact with terrain or obstacles and a warning 30 seconds from impact. It automatically desensitizes near airports to reduce nuisance alerts and also includes pilot-selectable audio inhibit and obstacle inhibit switches.

The FAA’s TAWS mandate means that all U.S.-registered, turbine-powered aircraft with six seats or more must install TAWS by March 29. The mandate covers Part 91, 135 and 121, and is split into class-A and class-B systems, depending on the number of passenger seats and the type of operation.

All Part 121 and Part 135 operations with aircraft configured for 10 or more passenger seats must have class-A systems, which include standard terrain warning system functions with a visual display. Part 91 aircraft with six or more passenger seats and Part 135 aircraft with six to nine passenger seats must have at least a class-B system. Class-B TAWS units do not require a display of terrain, but many operators are choosing to include this option.

In basic terms, TAWS is the newer “enhanced” technology that replaces the original ground proximity warning system (GPWS) developed in the 1970s. Standard GPWS capabilities provide warning for excessive rate of descent, excessive closure rate to terrain, altitude loss after takeoff, negative climb rate, flight into terrain when not in landing configuration and excessive downward deviation from glideslope.

TAWS adds two important enhancements to GPWS: forward-looking terrain avoidance and premature descent alerts, both of which have been identified as showing a measurable reduction in the fatal CFIT accident rate. In fact, since the first TAWS units were introduced in the mid-1990s, there have been no reported cases of a TAWS-equipped airplane being involved in a CFIT accident, a fact that has contributed to the FAA and other government bodies’ decision to mandate the equipment.