Overview
On April 15, 2008, about 1350 eastern daylight time, a Cessna 560XL, registration N613QS, was substantially damaged during a landing at Westchester County Airport (HPN) in White Plains, New York. The aircraft was operated under Title 14 Code of Federal Regulations Part 91, Subpart K as a fractional ownership flight. The two airline transport pilots and two passengers were not injured. Visual meteorological conditions prevailed and the flight had operated under an instrument flight rules flight plan.
Sequence of Events
The aircraft departed Palm Beach International Airport (PBI) in West Palm Beach, Florida, at about 1115. The flight was uneventful, and the crew conducted a normal visual approach to runway 34, which is 6,548 feet long and 150 feet wide. The landing gear was extended and both pilots confirmed that cockpit indications showed the gear was down and locked. After a normal touchdown, the copilot deployed the speed brakes and the captain deployed the thrust reversers. At that moment, the landing gear warning horn sounded, followed by the collapse of the left main landing gear, then the nose gear, and finally the right main landing gear.
The airplane left a ground scar approximately 960 feet long on the runway between taxiways H and G. It slid to a stop near taxiway C. All occupants exited via the right over-wing emergency exit because the main cabin door could not be opened due to the fuselage resting on the ground. The aircraft was not required to be equipped with a crash-axe, and Cessna stated that crash axes are not standard equipment.
Post-Accident Examination
An FAA inspector conducted an initial examination. The left wing sustained scraping damage resulting in a fuel leak; two ribs and a stringer were damaged, and a communications antenna was pushed through the pressure vessel. The cockpit landing gear handle was found in the down position. When the aircraft was lifted, both the right main and nose gear were fully retracted and engaged in their uplocks. The left main gear was also fully retracted but its uplock was damaged. The gear was manually extended and pneumatically blown down before towing. The hydraulic fluid level was within normal range.
The cockpit voice recorder (CVR), enhanced ground proximity warning system (EGPWS), and Altair Aircraft Data Acquisition System (ADAS) data were analyzed. The CVR revealed no unsafe gear warnings before touchdown. ADAS data showed the gear was down and locked from about 5 minutes before touchdown until about 3 seconds after touchdown. The weight-on-wheels signal switched from ground to air about 11 seconds after touchdown.
Further testing of hydraulic and electrical components found no malfunctions that would cause uncommanded gear retraction. However, the landing gear extend hydraulic line in the left wing between the control valve and the left main gear actuator showed evidence of an overpressure burst. This line was also common to the nose and right main gear actuators. The design working pressure was 1,500 psi and proof pressure 2,250 psi. According to Cessna, if the gear control valve had been commanding extend, all hydraulic fluid would have been expelled through the compromised line.
Additional Findings
Airport surveillance video showed the gear extended before landing but could not confirm if it was fully locked. Wiring schematics showed the landing gear and speedbrake systems were independent, but wiring bundles shared five common connectors; no electrical faults were found. The aircraft, serial number 560-5599, was manufactured in 2005 and had about 2,496 hours and 1,932 cycles. The captain had 8,660 total hours with 1,651 in type; the copilot had 23,000 hours with 43 in type.
The weather at 1356 was winds 290° at 11 knots, visibility 10 miles, clear skies.