Incident Overview
On November 6, 2015, about 1710 eastern standard time, a Cessna P210N, registration N731LT, was substantially damaged during landing at DeKalb-Peachtree Airport (PDK) in Atlanta, Georgia. The private pilot and one passenger were not injured. The airplane was registered to Horst Aviation, LLC, but operated by an individual under 14 Code of Federal Regulations Part 91 as a business flight. Visual meteorological conditions prevailed, and the flight was operating on an instrument flight rules flight plan. The flight originated from Smoketown Airport (S37) in Smoketown, Pennsylvania, about 1330, and was destined for PDK.
Pilot's Account
The pilot stated that he expected and was set up for an RNAV approach but was cleared for the ILS approach to runway 21L. He continued inbound to PDK, and upon reaching the final approach fix, he recalled lowering the landing gear. However, due to the approach distraction, he did not verify that the landing gear was down and locked. He continued the approach and reported breaking out of the clouds at 2,000 feet. When the airplane was at 200 feet above ground level, he reduced power and did not hear any warning horn. He indicated the landing was normal and very smooth. After rolling about 400 feet, he heard a "snap" and felt the airplane drop and veer to the left. The airplane rolled off the runway onto grass and came to rest with the nose landing gear down and locked but both main landing gear collapsed. The airplane was raised, and both main landing gear were extended for towing to the ramp.
Post-Accident Examination
Following recovery, examination of both main landing gear actuators revealed no evidence of leaks or hydraulic residue. A test gauge plumbed into the aircraft's landing gear hydraulic system held pressure (1,500+ psi) in the up and down position for more than 10 minutes. The airplane was placed on jacks and several fault-free gear cycles were performed, including an emergency extension. The single landing gear down and locked light functioned normally, and a left main landing gear down limit switch, which felt "a little sticky," was replaced. No damage was reported to either main landing gear downlock hook assembly.
A check of the landing gear warning horn revealed it was set 0.3 inch above the flight idle gate, while the specified setting is 0.6 inch above the flight idle gate. It was adjusted to the specified amount. Although a flight check of the landing gear warning system was not performed during a postaccident maintenance flight check, the repair facility reported it was performed by the owner on the first flight after completion of repairs, and no discrepancy was reported.
Landing Gear Design
A representative of the airplane manufacturer reported that during landing gear extension, the nose landing gear locks into place followed by the main landing gear. This occurs because the nose landing gear extends aft and is assisted by airloads, while the main landing gear extend forward against airloads. During retraction of the main landing gear, the wheel assembly drops about 12 inches below the position when fully extended. Fully locking down of the main landing gear actuator occurs with a downlock hook assembly installed on each main landing gear.
Maintenance History
The airplane's last annual inspection was completed on February 26, 2015. No discrepancies were reported during cycling of the gear performed during the inspection. The airplane had accrued about 66 hours since the inspection was performed.