What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
(-23) N876CS, a LR-60, departed hickory, NC, enroute to Omaha, NE. The pilot stated that approximately 55 miles into the trip at FL400 the right hydraulic (hyd) pressure light came on. Seconds later the left hyd pressure light came on for 3 seconds then went out. They heard a thump. The right hyd light stayed on and they went thru the check list which states to monitor the system when one light is on. They descended to FL380, in the event of a hyd failure. They noticed after minutes, that the hyd pressure was starting to decrease to 1400PSI. It stayed that way for 10 minutes. The left light then came on again for 10 seconds. When the left light extinguished, they heard a thump and the pressure went back to 1500PSI. Descending through FL180 the right light extinguished, and they noticed the hydraulic pressure was showing red line at 2000 PSI. The light stayed off for 1 minute then came on and pressure fell to 1800 PSI. They put the gear down. There was a quick drop in pressure, then it returned to 1500PSI. They were able to use flaps, tr's, and brakes. The crew discovered the pneumatic pressure line disconnected from the reducer which connects to the hyd reservoir. Maintenance confirmed the problem.
As the FAA filed it
(-23) N876CS, A LR-60, DEPARTED HICKORY, NC, ENROUTE TO OMAHA, NE. THE PILOT STATED THAT APPROXIMATELY 55 MILES INTO THE TRIP AT FL400 THE RIGHT HYDRAULIC (HYD) PRESSURE LIGHT CAME ON. SECONDS LATER THE LEFT HYD PRESSURE LIGHT CAME ON FOR 3 SECONDS THEN WENT OUT. THEY HEARD A THUMP. THE RIGHT HYD LIGHT STAYED ON AND THEY WENT THRU THE CHECK LIST WHICH STATES TO MONITOR THE SYSTEM WHEN ONE LIGHT IS ON. THEY DESCENDED TO FL380, IN THE EVENT OF A HYD FAILURE. THEY NOTICED AFTER MINUTES, THAT THE HYD PRESSURE WAS STARTING TO DECREASE TO 1400PSI. IT STAYED THAT WAY FOR 10 MINUTES. THE LEFT LIGHT THEN CAME ON AGAIN FOR 10 SECONDS. WHEN THE LEFT LIGHT EXTINGUISHED, THEY HEARD A THUMP AND THE PRESSURE WENT BACK TO 1500PSI. DESCENDING THROUGH FL180 THE RIGHT LIGHT EXTINGUISHED, AND THEY NOTICED THE HYDRAULIC PRESSURE WAS SHOWING RED LINE AT 2000 PSI. THE LIGHT STAYED OFF FOR 1 MINUTE THEN CAME ON AND PRESSURE FELL TO 1800 PSI. THEY PUT THE GEAR DOWN. THERE WAS A QUICK DROP IN PRESSURE, THEN IT RETURNED TO 1500PSI. THEY WERE ABLE TO USE FLAPS, TR'S, AND BRAKES. THE CREW DISCOVERED THE PNEUMATIC PRESSURE LINE DISCONNECTED FROM THE REDUCER WHICH CONNECTS TO THE HYD RESERVOIR. MAINTENANCE CONFIRMED THE PROBLEM.