Garmin this year plans to begin offering a G1000 integrated avionics retrofit package for the King Air 200 with the option for an electronic stability and protection system (ESP) to boost safety for hand-flying operations.

The product of more than two years of internal development, ESP uses the flight attitude and airspeed information largely available in the G1000 integrated avionics package along with the Garmin autopilot servo actuators to provide linear self-righting force feedback to the control column when certain programmable pitch, roll, airspeed and angle-of-attack limits are exceeded when the autopilot is turned off.

Garmin already holds a supplemental type certification to upgrade the Beechcraft King Air 200 and C90 with the G1000 system, which integrates all primary flight, navigation, weather, terrain, traffic, radio frequency, engine and fuel data readouts on two 10in (26cm) primary flight displays and a 15in multifunction display. The retrofit also includes Garmin's three-axis GFC 700 automatic flight control system autopilot. ESP, which requires additional software and Garmin's most recent autopilot servo actuators, will initially be offered as an option to the G1000 upgrade on the King Air 200 only.

A move into loss-of-control preventatives is a new direction for Garmin, which in the recent past has focused on an increasingly complex array of situational awareness tools for its various avionics systems, including terrain awareness and synthetic vision. "What can we do if people lose those situational awareness tools or if they become disoriented or incapacitated," says Ben Kowalski, Garmin director of OEM sales, of the company's logic in developing ESP.

Strictly speaking, ESP is not a true envelope protection system as the pilot can override the self-righting stick forces, either by mechanical force or by disabling the system if there is a need or desire - perhaps in flight training - to exceed the "soft" limits. All limits are selectable by the operator. By contrast, a traditional envelope protection system has "hard" limits that a flight-control computer will not allow the pilot to exceed.

For roll control, ESP activates when the roll angle exceeds 45°, the restorative force increasing linearly to a maximum torque at 60° of bank. If the pilot overpowers the actuator and continues banking past 75°, the roll correction ceases. "The assumption is that if you go that far, you're doing it for a reason," says Kowalski.

If the pilot allows the roll correction to right the aircraft, the system will continue applying the restorative force through 30° of bank. Kowalski notes that the ESP does not attempt to make the aircraft fly straight and level, although if the system detects that ESP is activated for more than 10s in any 20s period, it assumes the pilot is incapacitated and it activates the autopilot using a zero roll angle and zero vertical speed command.

Restorative control column forces in pitch begin at 17° nose up or nose down, increasing linearly to a maximum force at 22°. In nose-low situations below the pitch-up threshold but in which the aircraft is approaching its maximum operating speed, ESP will inject a pitch up control force that slows the aircraft with 2g or less vertical acceleration. On the low end of airspeed control, ESP, using information from an angle-of-attack sensor, will introduce a pitch-down force simultaneous with the sounding of the aircraft's stall warning indicator as the aircraft approaches its stall angle of attack.

Pilots can permanently disable ESP by inhibiting the process in the G1000 before flight, or temporarily by holding down the control wheel steering or autopilot disconnect switches.

Kowalski says Garmin is seeing "great interest" from King Air operators on the ESP option, which is currently in the "middle" of its flight-testing programme. Garmin has also announced that it will be offering ESP for the Cirrus SR22 single.

Source: Flight International