NASA's plan to make general aviation a mode of transport rivalling airlines is gathering pace - and gaining support

Graham Warwick/WASHINGTON DC

This month, NASA takes delivery of its latest experimental aircraft - a Cirrus SR22. The all-composite light aircraft will join a similar Lancair Columbia 300 delivered in January. The aircraft will become testbeds for NASA's Small Aircraft Transportation System (SATS) programme.

SATS is a five-year effort to demonstrate technology enabling small aircraft to use virtually any small airport in nearly all weather conditions. NASA's long-term vision is to create a new mode of transport that will relieve pressure on the USA's congested interstate highways and major airports.

Work towards this goal has begun at NASA Langley Research Center in Virginia, where the newly arrived Cirrus and Lancair light aircraft will be flight tested to develop detailed flight simulation models before being modified to allow rapid prototyping of cockpit technologies to be demonstrated under SATS.

"We want to be able to replace the cockpit from one experiment to the next," says acting deputy SATS programme manager Jim Burley. "We want to be able to take a panel, plug it into the simulator to check the hardware and software, then fly it." Cockpit technology is at the heart of the programme, which aims to make flying a small aircraft an easier, safer and more reliable mode of transportation.

NASA's near-term goals for SATS are to expand the capacity of the US air transport system by enabling higher-volume operations in the abundant non-radar airspace and at the thousands of non-tower airports; to reduce the cost of that expansion by lowering landing minimums at minimally equipped airports without making expensive improvements; and to exploit the expansion through increased use of small aircraft by making single-pilot flying at least as safe as two-pilot commercial operations.

These operational capabilities are supported by enabling technologies arrayed under projects including high-density operations and virtual visual meteorological conditions (VVMC). Together, they require the integration of many technologies into aircraft aimed at a market sector that is extremely price sensitive.

Industry alliance

NASA has budgeted $69 million over five years for SATS, a sum which it hopes will be matched by a general aviation industry alliance called the "single public-private programme interface" (SPPI). Bringing together aircraft manufacturers, system suppliers, airport operators, service providers and user communities, as well as financial investors and insurance underwriters, this is expected to be in place by August.

The SPPI will act as NASA's single collaborative business partner for the development and dissemination of SATS technologies. It is modelled on the industry alliance formed to support the forerunner to SATS, NASA's Advanced General Aviation Transportation Experiments (AGATE) programme. The Cirrus SR22 and Lancair Columbia 300 to be used as SATS testbeds are products of AGATE.

With the SATS programme NASA is looking further ahead, up to 25 years into the future, but some operational capabilities could emerge earlier to help with the USA's airspace problems - technology for high-density operations in unmanaged airspace, for example.

"Airspace is not the problem, it's the rules used to separate aircraft," argues Burley. "We separate small aircraft by three to five miles because that's the best air traffic controllers can do. Computers do not have the same constraints. If we can reduce the separation required we can increase the the number of aircraft operating in the airspace."

The high-density operations part of the SATS programme will demonstrate onboard algorithms and an "airborne internet" that will allow aircraft to collaborate on separation and negotiate approach sequencing with minimal human intervention. "This technology could benefit the big guys, it's just easier to prove it on a smaller aircraft first," he says.

The airborne internet will use network protocols being developed by the telecommunications industry, and SATS will focus on defining how the navigation, communication and surveillance information necessary for aircraft operations will be allocated between clients and servers. The network is likely to use satellite communications, with radio and mobile phone links as back-ups, says Burley.

In addition to enabling aircraft to self-separate, detect and resolve conflicts and self-sequence in uncontrolled airspace, the onboard technology will allow precise four-dimensional approach paths to be generated dynamically based on traffic, local weather, terrain and airspace restrictions, says NASA.

Increased cockpit automation is an important feature of the SATS concept. NASA's goal is to reduce the training required to fly a small aircraft, particularly for the low-time private pilot. Cockpit workload will be reduced so that a single pilot - private or professional - can fly as safely as a two-person crew in instrument meteorological conditions (IMC).

Key enabling technologies include the "highway-in-the-sky" flightpath guidance display developed under AGATE. When overlaid on a synthetic vision display (SVS) generated by an onboard terrain database, this promises to allow the pilot to land at a minimally equipped airport in Category I or lower visibility. "With SVS you can lower minimums to almost zero visibility and improve operational reliability in all but the most severe weather," Burley says.

The VVMC project is wider than developing operational procedures that are independent of visibility conditions, says NASA. It includes developing flight controls that simplify aircraft handling and limit the flight envelope as well as integrating autopilot functions and propulsion controls. "It's time to consider fly-by-wire for small aircraft," says Burley.

Software protected

Software-based flight controls that eliminate unwanted responses to inputs and simplified manual flying techniques such as velocity-vector control promise to make aircraft easier to fly. Flight envelope protection such as stall prevention and bank angle limiting will make them safer to fly. "You can augment a low-time pilot's skill in software with envelope protection and prevent him losing control," says Burley. "If he inadvertently enters IMC and loses situational awareness, the system can take control of the aircraft and turn it around." Emergency autoland in the event of pilot incapacitation will be one of the enabling technologies demonstrated by the SATS programme.

Also included within VVMC is the ability to generate active and alternative four-dimensional flight plans on board the aircraft using the cockpit flat-panel displays. For safer single-pilot operations, a decision support system or "virtual copilot" will fuse data from sensors, databases and datalinks to present the pilot with a prioritised assessment of flight status, including emerging hazards.

NASA plans to conduct high density operations and integrated flightdeck proof-of-concept experiments in 2003. In 2005, the SATS technologies will be integrated for showcase demonstrations. Already, Florida and Virginia have formed "SATSLabs" in a bid to host these events. How quickly the concept is deployed operationally will then depend on the market, says Burley. "I think an air-taxi-like capability will come first. It's a logical step down from the business jet market."

Source: Flight International