NASA’s Synthetic Vision Looks to a Safer Future

by Chris Bergin

A team of research engineers, pilots, technicians and air traffic control specialists have completed approximately 94 hours of airborne flight testing of NASA’s Synthetic Vision System (SVS) during an Equivalent Safety evaluation.

The testing used the Langley Research Center’s Cessna 206 Stationair fitted with the experimental Synthetic Vision navigation system.
Flight research operations were conducted at the Roanoke Regional Airport, Virginia – a site favored because of its close proximity to Langley, generous runway facilities, and surrounding terrain that can be used to put the SVS and pilots through challenging tests.

NASA has been tasked to meet the national goal of reducing fatal aircraft accidents by 80 per cent in 10 years, as part of the Aviation Safety and Security Program. Synthetic Vision is a significant part of the effort to meet this goal by reducing low visibility induced accidents, such as controlled flight into terrain and loss of control accidents.

“NASA is working towards the future of aviation to facilitate the development of avionics systems that will be out there in 5 to 10 years, and then develop advanced operational procedures that take advantage of the new capabilities that will work in that environment,” according to Lou Glaab, the principal investigator for the SVS-ES flight test experiment.

SVS works to present an electronic “out-the-window” and “God’s eye” view to a pilot in all weather conditions by combining Global Positioning System (GPS) positional data – an inertial navigation system – and digital terrain database information to determine aircraft location, heading, speed and other critical flight data. GPS and inertial navigation systems are not new to aviation, but a digital terrain database – presented to the pilot in a perspective field of view and integrated with advanced guidance symbology in an aircraft – is.

When asked how large a database would be required to operate SVS in an aircraft, Lou Glaab responded: “The database required to duplicate the surface terrain of the world would be in the terabyte range.”

SVS provides navigation guidance cues to allow the pilot to follow a “highway in the sky” to a runway approach under restricted/zero visibility conditions. The system also provides information about other nearby airborne traffic and aircraft on the ground in an airport setting. SVS provides critical information to pilots in a manner that is much easier to mentally assimilate than present day navigation systems, providing a significant increase in situational awareness, with a significant decrease in workload that will greatly increase flight safety.

During a briefing last year, LaRC research engineer Tony Bartolone noted: “SVS also promises to increase air traffic control system efficiency by providing new instrument approach flight paths that reduce aircraft spacing requirement during commercial airline operations.” This increased efficiency will result in lower fuel costs to airline operators and fewer delays to the air traveling public.  Overall, SVS displays can provide the safety and operational flexibility of clear-day visual meteorological conditions.

However, the SVS program is more that just producing pretty pictures for pilots in the cockpit. The research team is also working with the Federal Aviation Administration (FAA) to develop a new quantitative measure of flight safety that SVS will provide.
It’s one thing to produce and integrate hardware and software navigation systems for an aircraft. It’s quite another to be able to demonstrate a safety benefit and certify the system to meet FAA regulatory requirements.

The other part of this program seeks to quantitatively measure pilot performance and workload, comparing these parameters between present day “baseline round dial” (BRD) aircraft navigation instruments and SVS.
During the pilot orientation briefing, Lou explained: “While pilots are flying, we will measure things like pilot control entropy – how much the pilot has to work to move the controls – airspeed error, flight path error, and other established pilot workload metrics . We will measure pilot responses and performance while using the conventional “baseline round dials” and compare those responses while using SVS displays. 
By including both clear-day Visual Meteorological Conditions (VMC) approaches as well as simulated Instrument Meteorological Conditions (IMC) approaches in the research matrix, NASA is able to begin to establish the degree that SVS displays can change IMC flight”

This research effort will lead to a new “Equivalent Safety Metric” that can be used to help certify SVS for safe “real world flight” in the future.

A group of 24 general aviation pilots were selected to participate in the simulation phase of this Synthetic Vision System – General Aviation (SVS-GA) research program.
Eight pilots were highly experienced Instrument Flight Rule (IFR) pilots, eight pilots were relatively inexperienced IFR pilots and the last eight pilots were those that were not qualified to fly in IFR conditions with less than 400 hours total flight time. Each pilot was tasked to fly twelve approaches using SVS and BRD displays in the LaRC Integrated Flight Deck (IFD) B-757 fixed base simulator that had been modified to fly like a Cessna 206 general aviation aircraft.

It was observed that four of the eight non-IFR qualified pilots became disoriented during the simulations and ‘crashed’ while attempting to navigate the aircraft to the runway using current “round dial” display instruments. Subsequently all eight non-instrument rated pilots were able to successfully fly the aircraft to the runway using SVS, rivaling the performance of the high-time pilots flying with conventional displays.

This writer has flown approximately two dozen approaches in the LaRC IFD fixed base simulator and the LaRC Cessna 206 in actual flight at the Roanoke Airport using the SVS and BRD systems.  SVS delivers a quantum improvement in situational awareness that has to be experienced to be truly appreciated.

After flying an aircraft equipped with SVS, a pilot will feel like they are flying blind when reverting to present day 60 year old BRD technology. In addition, the pilot will have to work significantly harder to scan a multitude of instruments, rapidly absorb and assimilate the information and then act to safely control the aircraft.  This adds a significant amount of stress during potentially hazardous situations.

The SVS Equivalent Safety flight test team is composed of a group of managers, research engineers, pilots, maintenance technicians and air traffic control specialists. At times they live out of hotels and suitcases, pulling 12 hour shifts, working through weekends, hundreds of miles from home for weeks at a time.

During the airborne phase of the test program, Flight Operations Lead Eric Roback was constantly juggling travel arrangements, aircraft maintenance, subject pilot availability, crew work schedules and weather constraints to keep the test program moving ahead, while facing a program funding deadline at the end the fiscal year.

Safety pilot Chris Pali splits his work and family life, shuttling between Roanoke, Virginia; Langley Research Center and Saulsbury, Maryland . But when the time comes, Pali flies the Cessna with uncanny precision to an invisible three dimensional point in the sky, at the exact airspeed and heading required to start an experiment run.  He then turns the aircraft over to a harried subject pilot, who knows every word, movement and deviation is being observed and recorded, but will nonetheless try his best to make yet another precision approach for the day.

There have been over 270 fatal air accidents in the last decade caused by pilots becoming disorientated because they lost their reference to the horizon for any reason.  The Federal Aviation Administration lists this as the top reason for causing fatal general aviation accidents. SVS has the potential to significantly reduce those kinds of accidents – and save hundreds of lives.

For more images and questions, visit the SVS thread at:

Robert Winger can be reached at [email protected]

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