History of Flight
On May 27, 2011, at 0928 eastern daylight time, an Israel Aircraft Industries Gulfstream 200, registration N749QS, managed by NetJets Inc., sustained minor damage when the right main landing gear collapsed during an emergency landing at Stewart International Airport (SWF), Newburgh, New York. The two airline transport pilots and one passenger were not injured. The personal flight, conducted under 14 CFR Part 91K, departed Greenville Spartanburg International Airport (GSP), Greer, South Carolina, around 0730, destined for Westchester County Airport (HPN), White Plains, New York. Visual meteorological conditions prevailed, and an instrument flight rules flight plan was filed.
During approach to HPN, the pilot-in-command (PIC) selected the landing gear lever down. Sounds of gear transit were heard, but cockpit indications showed three red lights. The approach was aborted for a holding pattern. About 20 to 40 seconds later, a "R HYD OVERHEAT" message appeared on the engine indicating and crew alerting system (EICAS), with hydraulic pressure at 1500 psi (normal 3000 psi). The flightcrew completed the right hydraulic overheat checklist. They then performed the emergency gear extension checklist using the emergency blow-down bottle. Cockpit indications showed the nosegear green, but both main landing gear remained red. An emergency was declared, and the flight diverted to SWF due to longer runway and less traffic. HPN tower personnel reported all three landing gear appeared extended. During landing on runway 27, the airplane remained level for 2 to 3 seconds, then tilted right and settled on its right wing, sliding to a stop.
Personnel Information
The PIC, aged 45, held an airline transport pilot certificate with multiengine land rating, a commercial pilot certificate with single-engine land rating, and a Gulfstream 200 type rating. He reported 10,013 total flight hours, including 3,244 in type, with 105 hours in the previous 90 days and 25 in the previous 30 days. His most recent FAA first-class medical was issued January 6, 2011.
The second-in-command (SIC), aged 41, held an airline transport pilot certificate with multiengine land rating, a commercial pilot certificate with single-engine land, rotorcraft helicopter, and instrument helicopter ratings, and a Gulfstream 200 type rating. He reported 5,800 total hours, including 604 in type, with 65 hours in the previous 90 days and 37 in the previous 30 days. His most recent FAA first-class medical was issued December 30, 2010.
Aircraft Information
The 11-seat airplane, serial number 165, was manufactured in 2007. It was powered by two Pratt & Whitney Canada PW306A engines, each producing 6,040 pounds of thrust. The airplane was maintained under an approved inspection program; its most recent inspection was completed on May 14, 2011, at 2,982 total hours, with an additional 23 hours since. Maintenance from May 22 to May 26, 2011 included inspection of the nosegear uplock actuator, cleaning the emergency gear blow-down valve mounting hardware, and replacing the landing gear selector valve rod end. Following maintenance, the landing gear was cycled twenty times with no anomalies. On the incident day, a repositioning flight from Savannah, Georgia to GSP was uneventful.
Meteorological Information
At 0930, Stewart International Airport reported wind calm, visibility 15 miles, few clouds at 15,000 feet, temperature 24°C, dew point 17°C, and altimeter 30.01 inches of mercury.
Flight Recorders
The cockpit voice recorder (CVR) was read out at the NTSB Vehicle Recorders Laboratory. A summary report of the last 30 minutes was prepared. At 0902, the flightcrew (PIC flying left seat, SIC monitoring right seat) initiated landing gear extension. Sounds of gear travel were heard, but three green lights did not illuminate; a master warning "GEAR NOT DOWN" and gear warning horn activated. They entered a hold. At 0903, the SIC began the Landing Gear Down Lock Indication Failure checklist. Item No. 3 noted a right hydraulic pressure problem. Before cycling the gear, a master caution "R HYD OVERHEAT" activated, and seconds later a burning smell was noted. At 0905, the SIC suspended that checklist to perform the Hydraulic System Overheat checklist, reducing right engine thrust to idle. At 0907, the SIC returned to the Landing Gear Down Lock Indication Failure checklist, noting hydraulic pressure was not normal, and proceeded to emergency gear extension. At 0908, the PIC read the Emergency Landing Gear Extension checklist, performed the emergency extension handle release, turn, and lift, but only the nosegear indicated down and locked. The checklist had no instructions for that situation. At 0911, the flightcrew decided to divert to SWF and declared an emergency. At 0912, HPN tower advised all three gear appeared extended. At 0919, the SIC began the Right Main Hydraulic System Failure checklist but the crew agreed the system had not failed. At 0922, they were cleared for the visual approach to runway 27. At 0928, about 3 seconds after touchdown, the right main landing gear collapsed.
Wreckage and Impact Information
Initial examination revealed minor damage to the right wing from ground contact. The landing gear selector handle was found approximately 1/8 to 1/4 inch from the full down position. The airplane was jacked and supplied with ground electrical and hydraulic power. With the handle placed full up then full down, the gear cycled successfully. No tactile detent feel was noted, as detents were on the selector valve, not the handle. An emergency gear extension test (blow-down) locked all three gear. Hydraulic system examination showed no failures. When the selector handle was positioned to its as-found position, a hydraulic bypass hissing sound occurred, with temperature rise and pressure drop; main gear extended but did not lock, and nosegear did not extend. However, activating the emergency extension then locked all three gear. The selector valve rigging was visually inspected with no anomalies noted. The selector valve, emergency blow-down valve, and right main side brace actuator were sent for testing and teardown at manufacturer facilities; no mechanical malfunctions were found. A manufacturer representative noted that the Gulfstream 200 (formerly Israel Aircraft Industries Galaxy) had detents on the valve, not the handle. Hydraulic bypass from an intermediate valve position could prevent down lock engagement due to back pressure. Examinations could not determine why the emergency blow-down worked during ground test but not in flight; one possibility was the use of a hydraulic mule on the ground versus the aircraft's own system in flight.
Additional Information
Following the incident, the airplane manufacturer revised several checklists: replaced terms like "normal" and "low" with numerical values; added guidance to ensure the landing gear handle was at full down travel in the Landing Gear Down Lock Indication Failure and Emergency Landing Gear Extension procedures; and expanded the Emergency Landing Gear Extension procedure to cover a failed blow-down. Review of manufacturing drawings showed that the landing gear selector valve arm must be rigged within +10° to -5° from zero reference to prevent hydraulic bypass. Teardown testing of the incident valve indicated a design margin of +20° to -5°. Comparison of photographs to drawings revealed that when the selector handle was in full down position, the valve arm was approximately +12° from zero reference.