Within a decade, more Americans may leave their car in the driveway and opt to fly a small aircraft on their next 3-hour business trip.

That is the goal of a new NASA program which strives to deliver doorstep-to-destination travel at four times highway speeds to 25% of the nation's suburban, rural, and remote communities.

Easy-to-operate personal aircraft will cut travel costs by allowing direct access to many areas, cutting the odds of travel delays found with the current hub-and-spoke airline structure. NASA and its 70 partner companies are working together to push forward general aviation technologies. The hope is that widespread use of such improved aircraft will curb accidents, yet boost the number of small aircraft able to fly in our skies. Called the Advanced General Aviation and Transportation Experiments (AGATE), the consortium is developing new avionics, airframes, engines, and pilot training systems.

One part of the AGATE program, the "Highway in the Sky" (Design News, 9/7/98, p. 88), is designed to create new display systems. Another portion of AGATE develops on-board flight controls and on-ground communication technologies to relieve the current overburdened hub-and-spoke system. The ambitious new program looks to allow more people to access small aircraft flights.

In the last year the program has made great strides successfully flight testing a flight control and display system last May at Beech Field in Wichita, KS on a single-engine, 4-seater Raytheon (Beech) F-33 Bonanza. The new cockpit displays would replace traditional circular "steam gauges" with advanced displays of graphically intuitive depictions of the flight path.

"This test flight demonstrated that the open architecture we developed for the entire cockpit works in flight," says Bruce Holmes, NASA general aviation program manager and director of the AGATE alliance.

The precision navigation system couples airborne equipment, such as a global positioning system (GPS), display systems and architecture, with ground equipment, including local-area augmentation systems, which provide differential GPS correction for more precise aircraft navigation.

A benefit of GPS technology is that operating capability will increase during difficult weather conditions. Holmes attributes the technology leap to the revolution in digital bandwidth, which has provided swift processing speed at reduced cost of memory.

The cockpit displays are driven by an on-board computer, which operates at 1,000 times the level of reliability of analog/mechanical steam gauge systems and at a fraction of the cost, says Holmes. The main reason for the boost in reliability is that a solid-state attitude heading reference system, which uses GPS technology for updates, replaces older spinning-mass iron gyros. The new system requires less power to run, thus there are fewer heat-damage-related failures according to NASA Langley Research Center (Hampton, VA).

Such reliable systems will enable 4- to 6-seat aircraft to fly from smaller airports closer to their passenger's homes boosting total air traffic capacity to 5 times current levels. This technology will make air transportation accessible to a vastly increased number of communities, especially small towns of 20,000 to 50,000 people without airline service, by allowing small aircraft to fly into these towns at cost-competitive rates.

Natural flight. "We also want to make aircraft avionics more intuitive so pilots require less training to stay safe," says Noel Duerksen, a senior technical specialist in preliminary design with Raytheon. "The new system makes instrument flying as easy as visual flight," says Duerksen.

Single engine aircraft today use radio-beacon receivers to tell pilots where they are relative to a ground station. The Highway in the Sky uses GPS technology instead to generate a graphical map from the craft's current location to its destination. Pilots will then create a route by simply plugging in latitude, longitude, or city name, and then fly their small craft by viewing a visual graphic on a cockpit flat-panel display.

Most general aviation piloting today uses a stick or wheel connected via mechanical linkages to control surfaces elevator, rudder and ailerons that produce forces and moments on the airplane. The Bonanza also flight tested a new decoupled flight controller, which allows a pilot to control flight path directly. The airplane does not have a direct engine throttle, but instead uses an airspeed command lever, which tells the aircraft's computer what speed to fly, eliminating the guesswork and constant adjustment of different flight and engine controls today's systems require.

In a simulator experiment, NASA demonstrated the Highway in Sky display and decoupled flight controller, building a flight path, and having a mix of experienced pilots and novices fly a runway takeoff, racetrack course, and landing approach. "Seven individuals with no flying experience were able to successfully fly the racetrack pattern and land the aircraft on first attempt," says Duerksen. "Yet with conventional controls and displays, none of the novices could complete the first turn after takeoff."

Weather information provided in graphical display format and digital versus voice communications between ground and the cockpit were also demonstrated on the Bonanza. Both features boost safety through more intuitive operation.

"Our next step is to perform human factors experiments and develop standards to take advantage of reduced pilot workloads that an intuitive control system affords," says Duerksen.

As acquisition and training costs go down with the implementation of these new technologies, small aircraft will become a viable transportation option for more people.

"Today's hub-and-spoke system is saturated just like our highways with doorstep to destination speeds slowing down," says Holmes. "This new system will move air transportation system forward after hub lock."

What neural-network-based flight controls mean to industry:

Engineering roadblocks along the Highway in the Sky

Other uses for neural-network-based controls

Intelligent flight controls help pilots land safely

Breakthroughs in flight control technology from NASA may soon make it easier for pilots to fly aircraft despite hostile weather, equipment malfunctions, or severe damage. NASA launched the program in 1994, after an F-15 accident in which the aircraft's right wing was sheared off but the pilot managed to safely maneuver the aircraft.

Researchers, baffled by the pilot's ability to land, probed for principles they could extract from the incident and apply to making commercial aircraft more survivable. An unusual finding resulted: aircraft have more flight capability than pilots can actually use.

"We realized that if we could make the process more biological," says NASA Ames scientist Chuck Jorgensen, "training the flight controller to adapt just as an injured bird makes adjustments rather than freezing and dropping out of sky we can perform flight operations and keep damaged aircraft controllable."

Today's flight controllers are a medley of electromechanical systems, which signal aerodynamic control surfaces in response to pilot commands.

The intelligent flight control system employs experimental neural network software developed by NASA scientists at Moffett Field, CA and Boeing Company's Phantom Works Division (St. Louis, MO). Engineers at Dryden Flight Research Center in Edwards, CA are testing it on a modified F-15.

The "smart software," when fully developed, should increase safety, helping NASA reach its goal of reducing commercial aircraft accident rates by a factor of five over the next 10 years.

When the first F-15 was designed in the late 1960s, control software development took 1.7 million hours, with over 100 different iterations and 500 test flights to perfect. The neural network software cuts the amount of code required by a factor of 20. The neural network learns the aircraft's current operational status, checking it six times per second, sensing differences in response and adjusting control commands to keep the craft flying properly.

A neural network is pattern-matching software, which learns by example, not by reading line after line of code. Much as a child learns the difference between a dog and a cat through experience, the software learns to differentiate between what the pilot is commanding the aircraft to do and what the plane actually does, storing the information away, and providing the response and result the pilot needs.

In the flight controls, the neural net software program takes data from the aircraft's air data sensors airspeed, direction, pressure, and force and continuously computes 26 stability derivatives to compare the pattern of how the aircraft is actually flying with the pattern of how it should fly. These patterns are based on a series of pre-programmed aeronautical equations or control laws, which use the derivatives and define how the airplane flies. If there is a mismatch due to equipment failure, the aircraft's flight control computer uses the new neural network programming to "relearn" to fly the plane.

NASA used the F-15's front canards and gimbaling thrust engines to demonstrate how a flight control system would respond to severe damage. The demonstration flights proved that the "learning controller" can fly at top performance, with elaborate pilot maneuvering, while producing good handling qualities.

"Intelligent flight controls adapt and compensate for malfunctions, sensing changes in the aircraft's performance and rebalancing the system to fit the new flight characteristics," says Jim Urnes, Engineering Manager with Boeing Phantom Works.

Boeing has a decade of experience in researching and developing damage adaptive reconfigurable cockpit controls. The organization's engineers co-developed the intelligent flight controller with NASA and integrated the system into the F-15 test vehicle.

Future versions of the software may be retrofitted on new aircraft with digital fly-by-wire controls, such as the Boeing 777, the U.S. Air Force C-17 transport, and the F-22 fighter.

"We think that the intelligent flight control system has application to transport reusable launch vehicles, unmanned drones and commercial aircraft," says Jim Urnes. The system can also reduce development costs by eliminating the number of test flights required."

Building next-generation light aircraft

With composite construction and advanced aerodynamics, the Cirrus Design SR20 embodies the future of personal transportation aircraft. The 4-passenger craft incorporates flat-panel, multi-function display technology and state-of-the-art safety innovations, including an airframe parachute.

Dean Vogel, Vice President of Research and Technology, with Cirrus Design (Duluth, MN), talks about CR20 aircraft and what it means to the general aviation marketplace.

Design News: What is the status of the Cirrus SR20?

Vogel: The aircraft was certified in October 1998 and is in production. We delivered the first aircraft in July -- for a customer who placed an order in July 1994 -- and have backorders of over 300 aircraft.

DN:What makes Cirrus SR20 a unique entry in the light aircraft market?

Vogel: Cirrus spent considerable time identifying the customer and designed the SR20 from the ground up to serve that customer best. Our customers' expectations are driven by the automotive industry - they want safety, comfort, and a smooth, quiet ride. This is why we simplified the cockpit arrangement and instrument panel on the SR20 - to make them more ergonomic and similar to a car.

Safety is key to revitalizing general aviation. We need to get information to the pilot in the most intuitive way possible vs. forcing the pilot to collect information from a number of discrete locations and integrate that information him or herself. We can let computers do the integration and present the result graphically.

The composite construction of aircraft, particularly the fuselage, does a better job of protecting occupant space. The SR20 is the first general aviation airplane to incorporate a rocket-deployed parachute system as produced by Ballistic Recovery Systems (St. Paul, MN). The pilot can deploy the system to bring the occupants safely to the ground when he has gotten into significant trouble.

DN: What top three technologies are critical to development of new next generation light aircraft?

Vogel: First, integration of new computer technology in aircraft electronics is probably the most significant technology advancement. Next is the industry's ability to develop new manufacturing technologies to increase volume and reduce prices. Why does a Dodge Intrepid cost just about 20% of an SR20 when it is so much more complex? Manufacturing capability and production volume. Thirdly, communications technologies - up to and back from an airplane. They are all voice right now, but we need to enable digital information exchange to simplify the task of piloting an aircraft.