What is the expected compass and heading indicator reading for takeoff on runway 4?

For a takeoff on runway 4, the expected compass and heading indicator reading would indeed be 050°. This is because runway designations are based on the magnetic heading that corresponds to the runway's alignment.

Runway 4 indicates a heading of 040°, since runway numbers are determined by rounding the runway's magnetic heading to the nearest 10 degrees. Therefore, a runway labeled as 4 aligns closely with this heading, but for navigational purposes, pilots take off facing the runway's direction. In practice, the compass and heading indicator would reflect a reading of 050°, allowing for the slight difference between the runway number and the actual magnetic heading due to wind and other navigational factors.

This understanding of runway headings is essential for pilots to ensure accurate navigation and safe operations during takeoff and landing.