Final answer:
To operate a small UA within 30 minutes after official sunset as per 14 CFR part 107, anti-collision lights visible for at least 3 miles are required.
Step-by-step explanation:
According to 14 CFR part 107, a regulation set by the Federal Aviation Administration (FAA), to operate a small unmanned aircraft (UA) within 30 minutes after official sunset, the operator is required to have anti-collision lights that are capable of being visible for at least 3 statute miles. The lights must have a flash rate sufficient to avoid a collision, and they must be operational and used during the flight within this designated time period. This requirement ensures that the small UA can be seen by other airspace users during the period known as civil twilight, which can be more challenging for visibility due to decreasing light.