Gulfstream IV / G350 / G450
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Flight Crew Last 90 Days 87; Flight Crew Total 7265; Flight Crew Type 160
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Overcame Equipment Problem
Aircraft
We departed in a Gulfstream IV-SP. It was a clear day with visibility 10 miles. We were on an IFR flight plan to our maintenance facility for scheduled routine maintenance. The occurrence happened on initial climb out; from Runway 27R. Upon verification of positive climb rate the [landing] gear was selected in the up position and the main gear became unlocked (unsafe - no green lights); but the nose remained green in the down position; with the gear handle in the up position and illuminated red. We were told to transfer to departure control and upon doing so we reported a gear malfunction and request a continued climb to 2;000 feet and to remain in a west heading taking us out away from residential communities and people.We then began to recycle the gear to the down position to see if we could get them down and locked for safe landing; but recycling it down and up with 30 seconds interval just confirmed to us even more that the landing gear was malfunctioning and not going up or down to locked position. So we then asked ATC to grant us a climb to 3;000 feet with a block altitude of 3;000 to 5;000 feet so that we can do series of G maneuvers to see if can get the mains to a down and locked position. After approximately 5 or 6 turns with about 2G climb the left main became down and locked. Performed a few more to try to lock the right mains; but it was unsuccessful.After reading the landing gear malfunctioning checklist; we did one more maneuver stated on checklist which is the yawing of the aircraft to that corresponding side and see if airflow brings the gear to a down and locked position. It did not. So after about 15 mins of troubleshooting we asked ATC to be vectored back to [departure airport] for a low flyby for visual confirmation of the position of our gear. We were told by ATC that all 3 gear seemed to be in the down position; while the cockpit indication was showing left main and nose down and locked with right main unlit and gear handle lever lit red. So we proceeded back to the west to remain outside of residential [area] to perform an emergency gear blow down maneuver as per checklist. ATC asked us if we were [requesting priority handling] and we stated negative and not yet until we finalize our troubleshooting and determine the outcome.We asked ATC to contact our [maintenance] since our satellite phone was unserviceable at time of event; to ask and verify if there was another maneuvers we could perform for this particular event before we actually used the last resort of blowing down the landing gear per emergency checklist procedure. Once determining that the only solution would be to blow down the gear we began performing the emergency gear blow down procedure. We got to the third part of the checklist where it stated to pull the emergency D ring valve for clearing of lines and releasing of uplocks for 10 seconds then restowing. About 4 seconds into it the airplane vibrated slightly corresponding to a gear down movement and gear indication showed 3 green and an unlit gear handle. So we actually didn't have to complete the emergency checklist which calls for the actual blowing of the nitrogen bottle since we had proper cockpit indication and an aircraft vibrating feel corresponding to the gears going down.After that we decided to do one last flyby for a visual confirmation from ground personnel. It was verified by ATC that all gear were down and inner gear doors in their appropriate position. Since we had visual confirmation from the ground and most importantly visual confirmation in the cockpit and all proper indication that the gears were in a safe; down and locked position we decided to continue the remaining [short] flight to [original destination] where we had maintenance support on the ground awaiting our arrival.The determination to continue for a safe landing was done by me; the Captain of the flight with the following considerations: airplane was in complete controllability and not showing a malfunction anymore; enough fuel to fly in excess of 45 minutes after reaching [destination]; safety of flight not compromised; maintenance facility support; and according to checklist it does not state land as soon as possible. We proceeded to the airport and requested ATC to roll the fire trucks as a caution in the event that anything goes unplanned we would have support on standby and advised them we would like to stay at end of just slightly off runway and be towed out. After safely touching down and coming to safe stop; we had airplane towed to facility with the pinning of the gears for added safety and since engines were off at that point and no hydraulic pressure for support.
[Report narrative contained no additional information.]
GIV-SP flight crew reported they were unable to extend the landing gear to a down and locked condition following abnormal indications that were received after takeoff.