When should communications be transferred at airports not served by control towers or FSS?

The appropriate time for transferring communications at airports not served by control towers or flight service stations (FSS) is when you do not require direct communications anymore after approving a change to advisory. This process ensures that the pilot is aware that they can now proceed without needing continuous communication with air traffic services and can operate under advisory guidelines, which are suitable for these types of airports.

This fosters a more efficient communication protocol, as once the pilot understands the change in advisory status, they can conduct their operations based on that guidance without the necessity of ongoing conversation with controllers. In non-towered environments, smooth handoffs are crucial for maintaining workflow and safety.

The other choices suggest scenarios that are not aligned with proper communication protocols. For instance, transferring communications upon a pilot's request may lead to misunderstandings about the state of advisories, while transferring communications when the aircraft is on final approach could lead to a lack of critical information sharing at a crucial point in their operation. Closing a flight plan does not necessitate a communication transfer since it primarily pertains to administrative procedures rather than operational communication requirements.