Pilot's Guide

190-00663-03 Rev. A
Garmin G1000 Pilot’s Guide for the Beechcraft C90A/GT/GTi
417
AUTOMATIC FLIGHT CONTROL SYSTEM
UNDERSPEED PROTECTION
Underspeed Protection is available when the optional Electronic Stability and Protection (ESP) system is
installed and the autopilot is on. It is designed to discourage aircraft operation below minimum established
airspeeds.
When aircraft airspeed reaches 100 knots IAS, a yellow MINSPD annunciation (Figure 7-7) will appear above
the airspeed indicator. When the airspeed trend vector (specific to each flap setting) reaches a predetermined
airspeed, a single aural “AIRSPEED” will sound, alerting the pilot to the impending underspeed condition.
Airspeed
Indicator
Figure 7-7 MINSPD Annunciation
If the aircraft continues to decelerate, Underspeed Protection functionality depends on which vertical flight
director mode is selected. For the purpose of this discussion, the vertical flight director modes can be divided
into two categories: Those in which it is important to maintain altitude for as long as possible (altitude-critical
modes), and those in which maintaining altitude is less crucial (non-altitude critical modes).
ALTITUDE-CRITICAL MODES (ALT, GS, GP, TO, GA, FLC)
If the aircraft declerates to stall warning, the lateral and vertical flight director modes will change from
active to armed (Figure 7-8), and the autopilot will provide input causing the aircraft to pitch down and the
wings to level.
Lateral and
Vertical FD
Modes Armed
Figure 7-8 Lateral and Vertical Flight Director Modes Armed
An aural “AIRSPEED” alert will sound every five seconds and a red “UNDERSPEED PROTECT ACTIVE”
annunciation (Figure 7-9) will appear to the right of the vertical speed indicator. The pitch down force will
continue until the aircraft reaches a pitch attitude at which IAS equals the IAS at which stall warning turns
off, plus two knots.
Figure 7-9 Underspeed Protect Active Annunciation