HS25B flight crew reported loss of number 2 hydraulic system in the initial descent phase of flight.

Attributes
ACN	1396224
Time
Date	201610
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	HS 125 Series 700
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Route In Use	Direct
Flight Plan	IFR
Component
Aircraft Component	Hydraulic Main System
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Multiengine Flight Crew Instrument Flight Crew Commercial Flight Crew Flight Instructor
Experience	Flight Crew Last 90 Days 100 Flight Crew Total 13313 Flight Crew Type 317
Person 2
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Flight Instructor Flight Crew Instrument Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 55 Flight Crew Total 5400 Flight Crew Type 500
Events
Anomaly	Aircraft Equipment Problem Critical

Narrative:

I performed a walk around the aircraft and didn't notice anything abnormal during the preflight. Engine start; taxi; takeoff; and cruise were conducted in VMC conditions and all phases were uneventful. Just as we began our descent from our cruising altitude of FL270; the hydraulic 2 lo press annunciator illuminated. The hydraulic pressure gauge initially showed normal operating pressure of 3;000 psi; but about 20 seconds later; system pressure fell to 2;300 psi; indicating that neither hydraulic pump was operating and that the emergency accumulator had trapped 2;300 psi. We executed the main hydraulic failure checklist to evaluate which systems were still operative. We advised center that we had a complete hydraulic failure; which would require manually gear and flap extension and that we would need to be towed from the runway since nose wheel steering would be inoperative. We then completed the flaps 15 approach and landing checklist; reviewed the main hydraulics failure checklist; and performed the normal approach and landing checklists. We briefed the ILS approach and completed the approach and landing uneventfully. Emergency responders and a tug were waiting for our arrival. After landing; emergency crews walked around the aircraft to ensure there weren't any fires or fire hazards. [First officer] exited the aircraft to pin the landing gear and a tug towed us to the [ramp]. Hydraulic fluid was dripping from the left engine cowling. The airport emergency responders collected the crew names and flight plan route. He said that was all that was all he needed. After briefing maintenance personnel; we transferred the aircraft ownership to the mechanics.

Original NASA ASRS Text

Title: HS25B flight crew reported loss of Number 2 hydraulic system in the initial descent phase of flight.

Narrative: I performed a walk around the aircraft and didn't notice anything abnormal during the preflight. Engine start; taxi; takeoff; and cruise were conducted in VMC conditions and all phases were uneventful. Just as we began our descent from our cruising altitude of FL270; the HYD 2 LO PRESS annunciator illuminated. The hydraulic pressure gauge initially showed normal operating pressure of 3;000 psi; but about 20 seconds later; system pressure fell to 2;300 psi; indicating that neither hydraulic pump was operating and that the emergency accumulator had trapped 2;300 psi. We executed the Main Hydraulic Failure checklist to evaluate which systems were still operative. We advised Center that we had a complete hydraulic failure; which would require manually gear and flap extension and that we would need to be towed from the runway since nose wheel steering would be inoperative. We then completed the Flaps 15 Approach and landing checklist; reviewed the Main Hydraulics Failure checklist; and performed the normal approach and landing checklists. We briefed the ILS approach and completed the approach and landing uneventfully. Emergency responders and a tug were waiting for our arrival. After landing; emergency crews walked around the aircraft to ensure there weren't any fires or fire hazards. [F/O] exited the aircraft to pin the landing gear and a tug towed us to the [ramp]. Hydraulic fluid was dripping from the left engine cowling. The airport emergency responders collected the crew names and flight plan route. He said that was all that was all he needed. After briefing maintenance personnel; we transferred the aircraft ownership to the mechanics.

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.