What happened
On May 27, 2011, an Israel Aircraft Industries Gulfstream 200, registration N749QS, was performing an instrument flight rules flight from Greenville Spartanburg International Airport to Westchester County Airport. During the approach to Westchester, the crew attempted to extend the landing gear, but the cockpit indications showed three red lights instead of the expected green lights.
While the crew entered a holding pattern to address the gear indication, a "R HYD OVERHEAT" message appeared on the Engine Indicating and Crew Alerting System (EICAS). The hydraulic pressure dropped to approximately 1500 psi, well below the normal 3000 psi. The crew then performed the emergency gear extension checklist using the emergency gear blow-down bottle. This procedure resulted in the nosegear showing a green indication, but the left and right main landing gear remained red.
Due to the gear issues, the crew declared an emergency and diverted to Stewart International Airport (SWF) for a longer runway. Although tower personnel at Westchester reported seeing all three gears in the extended position, the crew proceeded with the diversion. Upon landing on runway 2/7 at SWF, the aircraft remained level for a few seconds before tilting to the right. The right main landing gear collapsed, causing the aircraft to settle on its right wing and slide along the runway. There were no injuries to the two pilots or the single passenger.
The investigation
Investigators found that the landing gear selector handle was positioned approximately 1/8 to 1/4 inch short of the full down position. Ground testing demonstrated that when the handle was moved to the full down position, the gear cycled successfully. However, when the handle was placed in the intermediate position where it was found during the accident, a hydraulic bypass occurred, causing a rise in temperature and a drop in pressure. This bypass prevented the main landing gear from locking.
While the landing gear selector valve arm was found to be 2 degrees beyond the specified rigging limits, this was not determined to be a contributing factor. Testing of the landing gear components, including the selector valve and the emergency blow-down valve, did not reveal mechanical malfunctions.