Occurrence
On 5 May 2024, a pilot and three passengers departed Landfontein Private Airstrip near Smithfield, Free State, in a Cessna T210L (registration ZS-NVM) on a private flight to Welkom Aerodrome. The flight was conducted under visual meteorological conditions and in accordance with Part 91 of the Civil Aviation Regulations. The pilot reported that after selecting the landing gear lever to the down position upon arrival at Welkom, an unusual click was heard and the gear-down indicator light did not illuminate. The hydraulic pump continued running. Attempts to extend the landing gear using the emergency hand pump were unsuccessful due to a lack of pressure.
The pilot diverted to New Tempe Aerodrome, where an aircraft maintenance engineer (AME) was contacted. Together, they attempted various troubleshooting procedures, including adding one litre of engine oil from the aircraft to the hydraulic system. This resulted in the nose landing gear extending and locking, but the main landing gear remained retracted. After burning fuel to reduce weight, the pilot performed a wheels-up landing on Runway 01 at 0910Z. The aircraft touched down on its underbelly with full flaps and the nose gear extended, at a speed of 65 knots, and skidded approximately 400 metres before veering left onto grass and stopping. The occupants were not injured and disembarked unassisted.
The aircraft sustained substantial damage to the main landing gear doors, bottom aft fuselage, left horizontal stabiliser, and left elevator.
Post-occurrence Inspection
After recovery, the hydraulic system was inspected and found to have an almost empty reservoir. The system was flushed to remove the engine oil residue that had been added during the flight. Further inspection revealed that the left main landing gear door actuator gland retaining ring had separated from the actuator assembly, allowing the cylinder rod to become adrift. This allowed hydraulic fluid to escape. It could not be determined with certainty whether the separation occurred before landing or as a result of the aircraft's weight coming to rest on the door; however, all components were still attached, suggesting the separation did not occur in flight. After reassembly and refilling with correct fluid, the system functioned satisfactorily when tested on jacks, with no leaks detected.
Findings
The pilot held a valid Commercial Pilot Licence and a Class 1 medical certificate. The aircraft had a valid Certificate of Airworthiness and had accumulated 4,243 airframe hours, with the last mandatory periodic inspection performed 24.54 hours earlier. The left main landing gear door actuator gland retaining ring separated, and hydraulic fluid leaked from the system, rendering the landing gear inoperative.
Probable Cause
The landing gear system failed to extend due to a lack of hydraulic fluid.