Crj-200 flight crew reported a taxiway excursion while holding for takeoff.

Attributes
ACN	1651055
Time
Date	201906
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Regional Jet 200 ER/LR (CRJ200)
Operating Under FAR Part	Part 121
Flight Phase	Taxi
Flight Plan	IFR
Component
Aircraft Component	Hydraulic System
Person 1
Function	Pilot Flying Captain
Qualification	Flight Crew Multiengine Flight Crew Instrument Flight Crew Air Transport Pilot (ATP)
Person 2
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Instrument Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Procedural Published Material / Policy Ground Event / Encounter Other / Unknown Ground Excursion Taxiway

Narrative:

There was ground delay program and ground stop into ord. The crew stayed at the gate as much as possible to minimize the time for the passengers on the aircraft sitting outside the runway. Right before the first tier of ground stop was about to expire at 00:00Z; passengers began to board and crew prepared for the flight. After block out from the gate and while taxiing to the runway for departure; ATC (air traffic control) updated estimated departure clearance time to 00:30Z. Crew decided to hold short of runway 36 on the taxiway D with the slope and had permission from ATC to shutdown engines. Parking brake was set and APU (auxiliary power unit) was still running; but turned hydraulic pump 3A off; leading to the situation that parking brake lost pressure and airplane started to roll back outside taxiway and both right and left main gears fall into the grass area. While rolling back into the grass; crew attempted to restart the engines to prevent rolling back but it was too late to stop the airplane. No damage on airplane was found except the right main gear door was bent. Ord ground stop and delay program led the crew to shutdown engines; and crew made a mistake to turn the hydraulic pump 3A off.always keep the hydraulic pump 3A on when shutting down the engines anywhere besides gate or chocks are in.

Original NASA ASRS Text

Title: CRJ-200 flight crew reported a taxiway excursion while holding for takeoff.

Narrative: There was ground delay program and ground stop into ORD. The crew stayed at the gate as much as possible to minimize the time for the passengers on the aircraft sitting outside the runway. Right before the first tier of ground stop was about to expire at 00:00Z; passengers began to board and crew prepared for the flight. After block out from the gate and while taxiing to the runway for departure; ATC (Air Traffic Control) updated estimated departure clearance time to 00:30Z. Crew decided to hold short of runway 36 on the taxiway D with the slope and had permission from ATC to shutdown engines. Parking brake was set and APU (Auxiliary Power Unit) was still running; but turned hydraulic pump 3A off; leading to the situation that parking brake lost pressure and airplane started to roll back outside taxiway and both right and left main gears fall into the grass area. While rolling back into the grass; crew attempted to restart the engines to prevent rolling back but it was too late to stop the airplane. No damage on airplane was found except the right main gear door was bent. ORD ground stop and delay program led the crew to shutdown engines; and crew made a mistake to turn the hydraulic pump 3A off.Always keep the hydraulic pump 3A on when shutting down the engines anywhere besides gate or chocks are in.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.