If an altimeter setting is unavailable, what should a pilot do first?

When an altimeter setting is unavailable, the pilot should adjust the altimeter to the field elevation of the departure airport first. This action ensures that the aircraft's altitude readings are accurate relative to the terrain and obstacle clearance around the airport. By setting the altimeter to the field elevation, the pilot can maintain awareness of the aircraft’s position concerning the ground level, which is crucial for safe operations during takeoff and landing phases.

Using the field elevation allows the pilot to operate with a baseline that reflects the actual height of the airport, which is especially important in situations where visibility is poor or when flying in mountainous areas. This technique helps in avoiding obstructions and ensures that the aircraft does not inadvertently enter potentially hazardous situations due to incorrect altitude readings.

While consulting airline ground control or using standard altimeter settings from nearby airports could be helpful steps, they are not the immediate priorities. Adjusting the altimeter to field elevation directly addresses the need for accurate altitude awareness. Proceeding without making any adjustments could lead to dangerous discrepancies in altitude, especially during critical phases of flight.