Which of the following is NOT listed as a type of oxygen deployment?

• A. Automatically
• B. Electronically
• C. Manually
• D. Hydraulically

Answer: (D)

Oxygen deployment is categorized by how the system is actuated. The common methods are automatic, electronic, and manual. Automatic deployment means the system releases you’re oxygen masks without crew action, typically triggered by cabin pressure or altitude changes. Electronic deployment uses electrical signals to release the masks, often tied to the aircraft’s control systems. Manual deployment requires the crew to initiate the release themselves by pulling a handle or operating a control.

Hydraulically isn’t a standard method used for oxygen mask deployment. Hydraulic actuation would add unnecessary complexity and weight for this function, so it isn’t listed among the typical deployment types. That’s why hydraulically is the appropriate choice as not belonging in the standard list.