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

For takeoff on runway 4, it is important to understand that runway numbers are based on their magnetic azimuth rounded to the nearest tens. Runway 4, thus, is aligned approximately at a magnetic heading of 040°.

When considering the heading indicator, which may not necessarily reflect the true magnetic compass directly due to magnetic variations and instrument calibration, the expectation for a takeoff heading would correlate closely with the runway alignment. As such, the appropriate heading indicated for a takeoff from runway 4 would be slightly offset due to standard departures, typically resulting in an indicated heading larger than the runway number itself.

Given this context, a heading of 050° is consistent with the expected procedure for takeoff from runway 4, as it allows for safe navigation during the initial climb and clearance from the runway environment. Thus, it is valid to conclude that the takeoff heading indicated by the instruments would correctly correspond to a reading of 050°.