Hydraulic System Leak During Landing-Gear Retraction
A twin-engine turboprop has just taken off from a 1,800-m runway. During gear retraction, the landing-gear indicator shows the left main gear still in transit. System A hydraulic pressure drops from 3,000 psi to 1,600 psi, and the reservoir quantity indication falls by 0.5 qt. The crew smells Skydrol in the wheel-well area, and the gear-up-and-locked light does not illuminate. The aircraft is at 4,000 ft and 8 nm from the departure airport. System B is showing normal pressure and quantity. The flight manual says that with a hydraulic leak in a primary system, do not cycle the affected system and plan to land at the nearest suitable airport. The crew wants to continue to a maintenance base 45 minutes away.
1. State the immediate crew actions and the reasoning for not continuing to the distant maintenance base.
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The crew should treat the situation as a hydraulic leak in a primary system and stop cycling the affected gear system. The pressure drop, fluid loss, and Skydrol smell in the wheel well indicate an active leak, not a sensor fault. Continuing for 45 minutes risks further fluid loss, possible loss of gear-down locking, and contamination or fire hazard in the wheel well. The flight manual guidance to land at the nearest suitable airport is directly applicable. The crew should declare the situation to ATC, plan a return to the departure airport or the nearest suitable airport, and prepare for a possible manual or gravity gear extension. System B should not be used to cycle System A components unless the flight manual specifically permits it. The objective is to land before the affected system loses the ability to lock the gear down.
2. Describe the troubleshooting and inspection sequence after landing.
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After landing and shutdown, secure hydraulic power and relieve pressure before inspecting. Check the wheel well, gear actuator lines, flare fittings, and the gear-up line for wetness and dye evidence. A 0.5-qt loss over a short retraction cycle is significant and should be traced, not topped up and ignored. Inspect the affected actuator and hose for chafing, and check the flare fitting torque and cone condition. If the leak is at a flare fitting, the fitting may need replacement rather than simple tightening; over-torque can crack the flare. Pressure-test the repaired system per the maintenance manual and check for leaks at operating pressure. Also inspect the wheel well for hydraulic-fluid contamination of insulation, wiring, and structure, because Skydrol can damage some materials. Verify gear retraction and down-lock indication before return to service.
3. What structural and system checks are needed before the aircraft is released after the leak repair?
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The repair must restore the system to its approved configuration: correct hose part number, fitting type, torque, and clearance. After repair, perform a functional test of gear retraction and extension, including down-lock and up-lock indication, and verify reservoir quantity and pressure. Inspect the wheel well for hydraulic-fluid damage to wiring, connectors, and composite or painted surfaces. Check that no line is chafing against structure or another line, and install clamps or stand-offs as required. Because the gear did not lock up, inspect the affected gear actuator and locking mechanism for damage from the incomplete cycle. Record the fluid loss and repair in the maintenance records. Release only after the system holds pressure, the leak is eliminated, and the gear indications are correct.