What is the DME to be maintained during the Portland Low departure before turning to fly direct to PT Silver?

The question pertains to maintaining a specific distance measuring equipment (DME) reading during the Portland Low departure procedure before the turn to PT Silver. The correct answer, which indicates that 5 DME should be maintained, is based on standardized departure procedures that dictate when an aircraft can safely begin a turn while ensuring separation from terrain and obstacles.

In this particular procedure, 5 DME signifies a point at which it is safe to initiate the turn to PT Silver based on the established air traffic protocols and guidelines. This distance is typically determined through a combination of navigation performance, obstacle clearance requirements, and expected route trajectories.

By maintaining 5 DME, pilots ensure that they adhere to the published departure procedures, which are designed to optimize safety and efficiency in the airspace surrounding an airport. This specification also reflects a consensus in aviation standards about appropriate clearances for departures from the Portland area.

The other distances listed are incorrect as they do not align with the established requirements for the Portland Low departure procedure, where clearly defined DME distances have been set for safety reasons, making option C the only accurate choice.