What provides gust lock protection on the ground?

• A. Residual hydraulic pressure trapped by checkvalves in the PCUs
• B. Electric gust locks actuated by the pilots
• C. Hydraulic pressure from the main pumps
• D. Mechanical pin locks on the control surfaces

Answer: (A)

Residual hydraulic pressure trapped by check valves in the PCUs provides gust lock protection on the ground. When the aircraft is parked, the hydraulic system is isolated but small amounts of pressure remain trapped in the power control units because their check valves prevent leakage. This residual pressure holds the flight-control surfaces in place, preventing movement from wind gusts and protecting the airplane while it’s on the ground.

Electric gust locks would require active electrical power and aren’t the mechanism used here. Hydraulic pressure from the main pumps isn’t relied upon once systems are isolated or off, and mechanical pin locks are not how the CRJ-550 achieves gust protection on the ground.