Which of the following is least likely to impact altitude coordination between fixed and rotary-wing aircraft?

The least likely factor to impact altitude coordination between fixed and rotary-wing aircraft is the type of fuel used. While fuel type affects various operational aspects, such as engine performance and efficiency, it does not directly influence how altitude is coordinated between different aircraft types.

In aviation, altitude coordination is primarily influenced by traffic patterns, aircraft type, and the experience of the flight crew. Traffic patterns dictate the vertical and horizontal spacing of aircraft in the airspace, thus impacting how both fixed and rotary-wing aircraft maintain safe altitude separation. The aircraft type also plays a critical role, as different aircraft have varying capabilities and performance characteristics that could affect altitude maneuvers. Furthermore, the experience of the flight crew is vital in making decisions based on situational awareness, understanding of airspace structure, and effective communication with air traffic control, which are all essential for maintaining safe altitude coordination.

In contrast, while fuel considerations are important for the overall operation of an aircraft, they do not directly relate to the specific coordination of altitude between different aircraft types within airspace, making them the least impactful factor in this context.