Date: 201710
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Night
Aircraft: Learjet 35
Operator: Air Taxi
Operating under: Part 135
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Initial Approach
Airspace: Class E ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Hydraulic Main System
Component problem: Failed
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Anomaly: Aircraft Equipment Problem Less Severe
Detector: Person Flight Crew
When detected: In-flight
Result: Aircraft Aircraft Damaged; Flight Crew Landed in Emergency Condition; Flight Crew Overcame Equipment Problem; Flight Crew Diverted
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: Terminal airport area on base to final crew completed all checklist items. On the before landing check the problem was noted. I; pilot flying; called for gear down and flaps 8 degrees; before landing check. At this point co-pilot; PM; noted flaps were not extending after he had extended the gear. We had a 3 green light indication on the landing gear but no reaction on the flap inputs. As co-pilot completed the before landing check; the hydraulic pressure check showed that we had 0 hydraulic pressure remaining. We were on short final; at this point I commenced a go-around and gained altitude. Climbed to 5000 feet and advised co-pilot to commence the abnormal procedure for loss of hydraulic pressure. I asked co-pilot about distances to ZZZ and ZZZ1 and lengths of runways at which point ZZZ became best option with emergency equipment; runway lengths and time to destination. As we headed in the general direction we re-contacted center; [advised] them; and got clearance direct to ZZZ. I was working radios and co-pilot was working the checklist. We took our time and talked about the issue in hand; discuss fuel available and determined who was responsible for each input on aircraft configuration.While the airplane was flying under autopilot I verified check list items while co-pilot monitored and spoke on the radios. We determined that in the terminal vicinity of ZZZ we would actuate the Auxiliary Hydraulic pump according to checklist to gain as many flap degrees as possible. We were able to attain a positive 1250 PSI hydraulic pressure that allowed for a flap 13-15 degree setting and briefed the higher Ref speed and landing distance for the said configuration. At this point I disengaged the autopilot and we were cleared for the visual approach. Approach to landing was non-eventful and last second before touchdown I engaged the Auxiliary Hydraulic pump for braking while I was on standby with the emergency air brake system and co-pilot was on standby with the drag chute. On touchdown I sensed brake pressure and applied the brakes while deploying the thrust reversers at which point we noticed a good braking rate and no need for the emergency air brake. I advised ATC that we may need a tug at the end but with positive hydraulic pressure and positive braking we were able to taxi to parking while on standby by with the emergency brake. Upon exiting the airplane we notice a hydraulic leak on the underside of the airplane; predominately the right main gear-well.




Synopsis: Learjet 35 Captain reported they lost all hydraulic pressure on initial descent.