Business & GA, Military

MiniJets: Maxi Avionics Performance

By Callan James | May 1, 2004

Neither the local area augmentation system (LAAS) nor microwave landing system (MLS—for European operators) is specified for the minijets. Full, fail-passive automatic flight control systems will be supported by advanced, dual attitude heading reference systems (AHRS) and air data computers. The air data computers also will provide a wide range of onboard functions, including reduced vertical separation minimum (RVSM) performance. The new minijets will accommodate autothrottles, full authority digital engine controls (FADEC) and health, performance and maintenance monitoring systems, as well.

Currently, dual Mode S transponders are specified on some of the minijets. But DME is offered only as an option—in part, to accommodate a possible European requirement.

ADS-B also is offered as a future option, but whether this will be FAA's domestic Universal Access Transponder (UAT) or the international 1090ES format, or both, is not clear. But the related Flight Information Service and Traffic Information Service (FIS and TIS) would certainly be part of a minijet's ADS-B installation. A traffic alert collision avoidance system (TCAS) or lower-powered traffic advisory system (TAS) may be offered as an option.

Weather Data

Currently, Avidyne and Garmin provide in-flight weather data from the National Weather Service (NWS) NEXRAD and commercial services via satellite links through Orbcomm and XM Radio, respectively. But in the new minijets, these will be supplemented by conventional weather radar. Garmin will offer an updated version of the earlier Bendix/ King KWX-58 X-Band system with a 10-inch (25-cm) plate antenna along with, reportedly, a quite remarkable maximum range claim of 320 nautical miles. Eclipse officials are not yet ready to announce their choice of radar. The Avidyne system can interface with up to 19 weather radars, according to Harper.

In the minijet installations, the redundant computers that integrate the avionics suite through high-speed data buses also will control a wide range of applications not normally linked to avionics services. In the Eclipse 500 (which the company calls an "electronic aircraft"), for example, the processing system has an open architecture design that, among many other tasks, embraces operation of the control surfaces and onboard environmental systems. The status of those systems is displayed on the PFD.

"We have a mechanically controlled aircraft and not fly-by-wire," an Eclipse spokesman clarifies. "But we used electronic actuators instead of hydraulics for the trim tabs, flaps and landing gear. Our only hydraulics is for the master brake cylinder." The electronics saves in weight and corrosion, since hydraulic fluid is really corrosive.

Are We Ready for Minijets?

A dozen or more minijet ventures are in various stages of development, or have been announced (the chart on page 18 does not include all minijets in development). It seems likely that over the next 10 years literally thousands of these aircraft could be flying. Cessna alone estimates it will sell 1,000 copies of its Mustang personal jet by 2010. It has been suggested that eventually, the number of small private jets operating in U.S. airspace will exceed that of all the nation's commercial passenger aircraft.

Though they will operate in the same high-altitude airspace, the minijets cruise slower than the airliners. The Eclipse 500's maximum cruise speed, for example, is slightly over 350 knots, while the Boeing 737's is about 520 knots. This and other factors, such as the significantly increased number of aircraft flying, will inevitably impact air traffic control (ATC), which also is attempting to come to grips with the question of handling even slower, unmanned air vehicles (UAVs) flying at those same heights.

A different concern touches on the rather sensitive question of what qualifications and training should be required of minijet pilots. They will face the difficult task of operating simultaneously in multiple demanding environments—in relatively high-performance machines, using advanced technology control systems at high altitudes. In many cases, the pilot may have little or no experience in any of those environments.

The TAA safety study covered the pilot training issue extensively and highlighted the special training needs with regard to operating new, more sophisticated avionics. It states: "The traditional GA training system has inadequate methods [and] does not specifically include training to exploit the additional safety opportunities of new technologies or to operate within the limitations of those technologies." The study suggests training should "rely greatly on various levels of simulation," including "CDs for home use on personal computers."

'Basics' Still Essential

In addition, the TAA safety study emphasizes that the technically advanced aircraft such as minijets "do not currently provide sufficient pilot assistance or automation to eliminate any traditional pilot knowledge, skill or judgement requirements." In other words, though the new avionics make flying easier, they don't negate the need for pilots to firmly understand the basics of flying.

FAA's initiative on pilot training for technically advanced aircraft probably will introduce a new level of pilot license, coupled with mandatory periodic recurrent training analogous to airline practice. The aircraft hull insurance industry probably will impose its own additional requirements, as well.

There is, however, little doubt that from the technical support side, the avionics providers are prepared. Avidyne and Garmin, plus the other major companies gearing up to enter the minijet market, are fielding a wide service network both here and overseas.

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