Gulfstream G100/G150 (IAI 1125 Astra)
Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor; Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 75; Flight Crew Total 9000; Flight Crew Type 3000
Aircraft Equipment Problem Critical
Flight Crew Overcame Equipment Problem; General Maintenance Action
Aircraft
On descent; while getting vectored for ILS Runway XX (airport in sight); at approximately 6;000 feet; the PIC selected flight air brakes. I then noticed the HYD LEVEL light illuminate on the master caution panel. The PIC retracted the flight air brakes; slowed to gear extension speed; and selected gear down. The gear came down and indicated down and locked. The HYD LEVEL light extinguished; and normal main system pressure and auxiliary hydraulic pressures were indicated. Normal checklists were completed; and the crew discussed going missed and diverting to a more suitable airport with longer runways if indications of a main hydraulic failure presented. For the duration of the approach; all indications were normal until at least the second half of the landing roll; when HYD level light began to flicker and the main system pressure began fluctuating. The PIC was able to use normal braking for the first half; and then they faded and he selected Emergency braking. Nose wheel steering was intermittent; but sufficient to get the airplane into the chocks at the FBO. We advised ground that we were experiencing intermittent steering issues and would keep them advised if we needed assistance (tug). Post flight inspection showed hydraulic fluid coming out from the bottom of the right wing under the airbrakes.
G100 First Officer noted a hydraulic low level light when the Captain selected flight air brakes. The light extinguished when the airbrakes were retracted and the approach was continued to landing. Normal wheel brakes were used during the first half of the ground roll then they fail and emergency brakes are used. A large leak was noted under the right wing after parking.