A weather radar is required for IMC operations if thunderstorms are expected to develop.

• A. Yes, always
• B. Yes, but only if thunderstorms have developed already
• C. No, unless it is part of the MEL
• D. No, if the cruise level is planned over FL410

Answer: (B)

The key idea is that weather radar is used to detect and assess convective activity in IMC so you can avoid thunderstorms. It’s not required merely because thunderstorms are forecast to develop; the need for radar becomes critical when thunderstorm cells have actually formed because you must have real‑time information about their location, movement, and intensity to navigate safely. That’s why the best answer is that a weather radar is required for IMC operations if thunderstorms have developed already.

If thunderstorms are only expected to develop but haven’t formed, you can rely on forecasts and other planning tools to route around potential convection, so radar isn’t mandated by that state of development. The other options imply blanket or condition-based requirements (always, only if part of MEL, or at high cruise levels) that don’t align with the practical use of radar for detecting active convective weather in IMC.