Automatic Emergency Descent Mode
This is a work in progress
Conditions Required for EDM / EDM at Top of Descent
Photo: G500 Pressurization system EDM, PAS, p. 15-22
Click photo for a larger image
[PAS, p. 15-22]
- Conditions Required for EDM: Cabin Pressure Low, Aircraft altitude > FL400, Autopilot engaged.
- Description of EDM at Top of Descent
- Autothrottles → Will engage if disengaged, throttles retard to idle to facilitate rapid descent, FMA Power display on PFD → FLCH.
- GP LATERAL mode → Deselected, FMA Lateral display on PFD → EDM, Commands 90° left turn, New heading displayed in LATERAL window.
- GP VERTICAL mode → FLCH, FMA Vertical display on PFD → IAS with ASEL armed.
- GP Speed mode → MAN, VMO displays in SPEED window, High Speed Protection n/a with AP engaged.
- Altitude → 15,000' set in preselect window.
- Speed brakes deploy to provide max drag, Approximately 20 kts above VMO, Handle doesn't move.
EDM at Level Off
Photo: G500 Pressurization system EDM at level off, PAS, p. 15-23
Click photo for a larger image
[PAS, p. 15-23]
- The following occurs automatically:
- ASEL captures altitude set in preselect window, FMA Vertical display on PFD → ASEL, Once altitude captures → ALT.
- 1000' above level off altitude the speed target changes to 250 kts, FMA Power display on PFD → IAS and target speed maintained as long as AT engaged.
- Speed brakes retract at approximately 270 kts.
- Cancel EDM anytime by disengaging AP on the GP or pressing AP Disconnect button on sidestick. Until then, the Guidance Panel buttons / knobs are locked out and the AP force sensor disconnect logic is bypassed.
The Autopilot has an automatic Emergency Descent Mode (EDM) that is armed anytime airplane altitude is at or above 40,000 feet with autopilot selected on. If the Cabin Pressure Low (warning) CAS message is displayed with EDM armed the following occurs:
- The SPEED target on flight guidance panel changes to 340 KCAS in MANUAL mode.
- The ALTITUDE preselect is set to 15,000 feet.
- The AP commands a left turn with a 90° heading change in the HEADING HOLD mode.
- The A/T decreases engine power levers to idle. If the A/T is not engaged, A/T automatically engages and decreases engine power levers to idle.
- The airplane descends at MMO / VMO to 15,000 feet.
- Speed brakes extend automatically as airspeed increases above 0.91M / 315 KCAS.
- Speed brake extension will stop if AOA increases above 0.7. Once AOA reduces below 0.7 Speed brake extension will continue.
- Speed brakes auto retract with altitude less than 16,000 feet and airspeed less than 275 KCAS.
- At 15,000 feet, the SPEED target changes to 250 KCAS.
- Aircrew may override EDM by disconnecting the AP.
- Crew Oxygen Masks . . . Don
- MIC (COMM JACKS) . . . MASK
- Passenger Oxygen Masks . . . Deploy manually and verify deployed
- Emergency Power . . . ON (if required)
- Guidance Panel . . . Verify speed, heading, and altitude targets are set
- SEAT BELT / NO SMOKE PASSENGER WARNING . . . ON
- Transponder Code . . . Set 7700
- ATC . . . Notify
Emergency lighting should be considered for cabin occupants.
Gulfstream GVII-G500 Airplane Flight Manual, Revision 3, July 16, 2019
Gulstream GVII-G500 Production Aircraft Systems, Revision 1, Oct 1, 2018