When shall radar and radio transmitting equipment not be operated on aircraft?

• A. During preflight checks
• B. Fueling, defueling, tank repair operations
• C. During taxiing
• D. In flight

Answer: (B)

Fueling operations create a risk of ignition from flammable fuel vapors. Radio and radar transmitting equipment can act as ignition sources through arcing, sparks, or the energy they emit, which could ignite vapors in the vicinity. To minimize this danger, transmitting gear is not operated during fueling, defueling, or tank repair operations. Outside of those fueling-related activities, radios and radar are used as part of normal aircraft operations (during preflight, taxi, and in flight) because the need for communication and navigation takes precedence and the ignition risk is not present to the same extent.