How can you recognize a hydraulic system leak on an aircraft?

• A. Loss of hydraulic pressure is the only sign.
• B. Visible fluid traces are the only sign to look for.
• C. Loss of hydraulic pressure, dripping or seepage, visible fluid traces, or dye in the system.
• D. Audible pump noise alone indicates a leak.

Answer: (C)

Recognizing a hydraulic system leak relies on looking for multiple indicators, not just one. Leaks can show up as a loss of hydraulic pressure, dripping or seepage of fluid, visible fluid traces on components or in the surrounding area, and the use of dye in the fluid to highlight the leak. The dye helps confirm a leak by making tiny seepage visible that wouldn’t be obvious otherwise. Relying on a single sign is unreliable—pressure can drop for other reasons, dripping alone may not reveal the extent, and audible pump noise does not prove a leak. So noticing a combination of these signs provides the most reliable indication of a hydraulic leak.