What must a pilot in command be familiar with before beginning a flight under IFR?

A pilot in command must be thoroughly familiar with runway lengths at both the intended airport and any alternatives before beginning a flight under Instrument Flight Rules (IFR). This knowledge is critical for ensuring that the aircraft can safely take off and land at the airports in use, considering factors such as aircraft weight, performance characteristics, and environmental conditions. Knowing the runway lengths helps in evaluating whether the available runways can accommodate the aircraft safely regarding takeoff and landing requirements.

While information about weather conditions, communication procedures, and entertainment options may be relevant in certain contexts, they are not as crucial as understanding the physical capabilities and limitations of the runways. Safe flight operations hinge significantly on the pilot's competence in managing these factors, particularly in complex IFR scenarios. Thus, being informed about runway lengths directly contributes to operational safety and efficiency.