Which situation requires an immediate notification according to NTSB Part 830?

The correct answer pertains to situations that may constitute an emergency or have significant safety implications. When a required flight crew member is unable to perform their duties because of illness, it necessitates immediate notification as this directly impacts the flight's safety and operational capability. If a crucial member of the flight crew is incapacitated due to illness, it raises concerns regarding the ability to safely conduct the flight, manage emergencies, or carry out essential tasks. Reporting this is critical for ensuring that an adequate and qualified crew is present for flight operations, in line with regulations aimed at promoting safety in aviation.

In contrast, while issues like fatigue, malfunctioning landing gear, or technical problems noted during pre-flight checks are certainly important, they do not necessarily demand the same level of immediate notification specified in NTSB Part 830. Fatigue may lead to operational considerations, but it's not as immediate as the direct impact of illness on crew capability. Malfunctions may need to be addressed, but they do not trigger immediate notification unless they affect the safe operation of the flight. Technical issues can often be resolved before the flight without the need for immediate outside reporting.