The first certificated synthetic-vision flight displays face the ultimate test with general aviation operators plying the mountains and fjords of south-east Alaska

Alaska is a tough testing ground for aviation technology. But the US state's challenging and isolated flying environment makes it an ideal laboratory for the operational evaluation of avionics advances intended to improve general aviation safety. Given the atmospheric and topographic hazards routinely faced by Alaskan operators, any technology that improves their safety record should benefit general aviation in more benign environments, where weather and terrain continue to be major causes of accidents.

Alaskan pilots are the first to gain operational experience with a new generation of electronic flight instrument system (EFIS) designed to improve situational awareness and help avoid controlled flight into terrain and inadvertent entry into instrument meteorological conditions (IMC) - two perennial causes of GA accidents. The FlightLogic display suite developed by Chelton Flight Systems is the first "synthetic vision" EFIS to receive certification, and features three-dimensional terrain and "highway-in-the-sky" flight guidance.

Chelton won the contract to supply avionics for up to 200 Alaskan aircraft under Phase II of the US Federal Aviation Administration's Capstone programme to accelerate the deployment and evaluation of emerging technologies to reduce aircraft accidents. Capstone Phase I, involving 200 aircraft in the Yukon-Kuskokwim delta, is the first major operational use of automatic dependent surveillance - broadcast (ADS-B). Now Phase II has been launched in south-east Alaska with the intent of creating a satellite-based infrastructure for instrument flight rules (IFR) operations in a region of mountains and fjords where ground-based navigation aids are unusable.

Terrain is the major change from Phase I to Phase II, says Jim Call, FAA aviation safety inspector at the Capstone programme office in Anchorage. While the area of western Alaska around Bethel is fairly flat, the terrain around Juneau in the south-east in exactly the opposite. "The conditions are very challenging," he says.

Because of the mountains, existing airways are too high to be usable by aircraft plying the fjords and they incur the danger of icing. The goal of Capstone Phase II is to use satellite navigation, datalink and the terrain awareness warning system (TAWS) to lower the minimum en route altitudes and create a useable IFR route structure.

Avionics advance

The other major change from Phase I to Phase II is in the avionics. Aircraft involved in the first phase are equipped with a UPS Aviation Technologies-supplied avionics suite consisting of a GPS receiver, multifunction display (MFD) and datalink. The system selected for the second phase is more extensive and more integrated and consists of two Chelton flat-panel displays, Shadin digital air-data computer, Crossbow solid-state attitude and heading reference system (AHARS), and a wide-area augmentation system (WAAS)-compatible GPS supplied by Free Flight Systems. UPS Aviation Technologies is providing an improved version of its UAT(universal access transceiver) datalink, which will also be retrofitted into Phase I aircraft when it becomes available early next year.

Boise, Idaho-based Chelton, part of the UK's Cobham group, received an innovative supplemental type certificate (STC) for the FlightLogic EFIS in March, approving the system for installation on 600 different general aviation fixed-wing aircraft models. The company is anticipating a similar "blanket" certification for multiple helicopter types to support Capstone. Under Phase II of the programme, the FAA plans to pay for the equipment and its installation on 200 aircraft operating in southeast Alaska - 150 fixed-wing and 50 rotary-wing.

As with Phase I, the evaluation will run for three years initially, after which participating operators will be able to buy the equipment or have it removed from their aircraft. The latter option is considered unlikely given the success of Phase I, which has seen accident rates reduced by 40% for equipped versus non-equipped aircraft, according to Leonard Kirk, Capstone co-ordinator for the University of Alaska's Aviation Technology Center in Anchorage (UAA). "Everybody in Phase I wants to keep the equipment, and they would like the Phase II avionics," he says.

The UAA is collecting and analysing Capstone data for the FAA. The university operates a Cessna 172RG that has been used for certification of the Phase II avionics, and is responsible for training pilots to use the Chelton synthetic-vision EFIS. The programme is still in its early stages, with only five aircraft equipped so far, including UAA's Cessna, but initial experience with the system is positive, says Kirk.

The other aircraft are a Cessna 180 floatplane operated by Alaska Seaplane Service, a Piper Chieftain air ambulance flown by Harris Aircraft Services, a Piper Seneca operated by LAB Flying Service, and a Yakutat Coastal Airlines' Cessna 206. Two more aircraft will joint the equipped fleet this week.

The bulk of installations is expected to begin after the Alaskan tourist season ends in September. Installation contractor Helipro International is likely to equip the majority of the aircraft between October and April. Three levels of installation are envisaged, the basic level involving just the UAT transceiver and providing ADS-B, flight following and enhanced crash rescue. For aircraft with limited panel space, mainly helicopters, the second level combines the UAT with the navigation display (ND) and provides terrain and traffic awareness. Most aircraft are expected to equip with the full dual-screen system, says Call.

Emerging technologies

A goal of Capstone is to look for emerging technologies and accelerate their certification, and a synthetic vision EFIS was specified after the programme evaluated NASA work on highway-in-the-sky (HITS) symbology. "We decided HITS was within a year of being mature enough to certificate so we went out with a request for proposals asking for synthetic vision," says Call. As a result, Alaskan pilots are the first to gain operational experience with a technology that is a significant step ahead of any other EFIS is use today.

Chelton's solution draws heavily on military head-up display (HUD) experience. The biggest departure from a conventional attitude director indicator is the use of a flightpath vector symbol, which shows where the aircraft is going rather than where the nose is pointed. There is a HUD-style pitch ladder, as well as airspeed and altitude tapes, but the most visually striking feature of the primary flight display (PFD) is the use of 3D terrain and perspective sky, stretching the full width of the display, in place of the traditional artificial-horizon "ball". Overlaid on the wireframe terrain are conformal perspective runway and obstruction presentations, drawn from the same digital database used for the navigation display.

When following an IFR flightplan or flying an instrument approach, highway-in-the-sky navigation guidance is provided by a series of boxes on the PFD. The boxes are 400ft (120m) wide and 320ft high and spaced 2,000ft apart out to 3.7km (2nm) ahead of the aircraft. In essence, a flightplan or approach is flown by keeping the flightpath vector inside the boxes, all the way down to the runway if necessary.

Despite its departure from tradition, the first pilots to use the Chelton system operationally, some of which have never flown an EFIS-equipped aircraft, describe the synthetic vision display as intuitive. To prepare pilots, UAA runs an intensive two-day classroom course using training devices that have actual avionics displays driven by Microsoft Flight Simulator software. "These unique training devices allow the aircraft to be a useful tool from the pilot's first flight," says Kirk.

"Ground training was rough," says Jim Wright, director of operations for Alaska Seaplane Services, "There was so much stuff to learn my head was spinning. There are lots of buttons - eight on each display - and they all do something. But then I got in the aircraft, started playing with the system and it was a piece of cake." He describes the system as well designed and easy to use, and recently flew his first instrument approaches in 10 years. "I shot them with no problem," he says. "It's very intuitive and flows nicely."

Because it flies floatplanes up and down the narrow fjords, Alaska Seaplane Services operates visual flight rules (VFR) only. While Capstone Phase II is aimed mainly at IFR operators, Wright sees benefits of the system for VFR operations. "The GPS is pretty accurate, so we know where we are all the time, and [the TAWS] shows where the hills are," he says. Wright is experimenting with producing and storing flightplans the VFR pilot could activate after inadvertently entering IMC to safely fly out of bad weather.

Harris Aircraft Services is an IFR operator, flying air ambulance missions to 20 communities of south-east Alaska. "The system is very user-friendly when it comes to setting up and modifying flight plans," says Mark Hackett, director of operations. "The difficult part is transitioning from analogue instruments to EFIS. It takes a bit of getting used to, but it's simple even though there is a lot of information in front of you." He describes the system as user friendly, and in anxious for additional features, such as traffic, to be available.

Operator input has already resulted in one software upgrade, and others are expected. "This is similar to Phase I, where we have had four or five changes." Call says. Initial installations have resulted in some lessons learned, particularly about location of the micro-electromechanical system-based AHARS, which has proved "very sensitive", he says.

But overall, initial pilot and operator reaction to the Chelton synthetic vision EFIS has been "outstanding, they really like the system", Call says.

Source: Flight International