In the drift test, after placing the aerial device at 60 degrees elevation at full extension with hydraulic fluid at ambient temperature, which action should be performed next?

• A. Immediately operate the device to check drift
• B. Close manually operated valves and allow the device to stand for 1 hour with the engine off
• C. Increase elevation to 75 degrees and monitor
• D. Verify results against manufacturer specifications

Answer: (B)

During a drift test you want to observe how the device behaves under stable, static conditions, without hydraulic pressure or heat from running the system. After you’ve elevated the boom to 60 degrees and extended it fully, closing the manually operated valves isolates the hydraulic circuit, so there’s no pump output affecting the motion. Letting the system stand for about an hour with the engine off allows the hydraulic oil to remain at ambient temperature and the components to settle, revealing any leaks or real drift as a true, zero-loaded movement. This setup yields a drift reading that you can compare to manufacturer specifications. Moving the boom, increasing elevation, or testing while the system is pressurized would introduce variables (pump pressure, temperature changes) that distort the drift measurement, and checking results against specs is something you do after this stable observation.