Gulfstream IV / G350 / G450
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew FLC Overrode Automation
Aircraft
Approach Control vectored our flight to a high right downwind for a visual approach. For additional guidance we selected the FMS RNAV approach. We were vectored approximately 5 nm west of the airport on a heading of 350 degrees. The autopilot was OFF and autothrottles ON. After passing abeam the runway at 9;000 feet and 200 KIAS; we were cleared to 8;000 feet and turned to heading 080 degrees. I turned to heading 080; disconnected the autothrottles; manually idled the throttles; requested flaps 10; selected FLCH and began descent to 8;000 ft. Prior to roll out on heading 080 degrees and before reaching 8;000 ft; we called 'Field in sight' and Approach Control cleared us for the visual approach and instructed us to contact the tower. The tower cleared us to land. Selected altitude alert to field elevation; selected flaps 20 and slowed to approximately 180 KIAS. Turned right and intercepted final approach course and V Path approximately 2 nm north of FAF of the RNAV approach. Attempted to engage autothrottles; but they would not engage. Continued with manual throttles. Approaching FAF and descending; selected gear DOWN with three green indication and attempted to advance throttles to stabilize approach. Throttles would not move from idle. Pressed DOWN on thrust reverser handle to ensure they were stowed; then applied heavy forward pressure on throttles in order to advance them from idle advance throttles. The throttles would not advance. Depressed autothrottle disconnect on front of throttles. Throttles were still at idle. We were sinking below V PATH and speed decreasing to flap 20 Vref +10. I don't recall actual KIAS. Called for LANDING GEAR UP to increase glide ratio/lower rate of descent and maintained speed. It was obvious that in this configuration we could not make it to the airport and houses were in all directions. The nonflying pilot (NFP/captain) [advised ATC]. I told the NFP do everything he could to free the throttles from idle and I would fly the aircraft. We had just crossed over a reservoir and it or the open area on the south were the only places to land. Just as I was about to turn back to the reservoir area to land; the NFP took the heel of his left hand palm and slammed it into the throttles hard and freed them. I took control of the throttles; accelerated them to make a shallow climb to the V path; selected gear down and flap 39. The NFP notified the tower that we would now make a normal landing and we were cleared to land. We made a normal landing and throttles operated normally all the way to the ramp and shut down. I have no idea what was wrong with the aircraft except I could not move the throttles from idle. In retrospect; I could have selected TOGA in an attempt to advance the throttles and/or turn the master autothrottle switch to OFF. I know from experience that only light pressure is required to overpower the autothrottles when they are engaged.
Reporter indicated that no defect was discovered post flight.
G-IV Captain reported the throttles would not come out of the idle position while on final approach. The First Officer was able to get the throttles unstuck by slamming them violently with his palm.