April 1, 2020
We like to think at a non-towered airport, choosing the best runway for takeoff/landing is a simple matter of picking the runway best aligned with the wind. However, for many pilots a multitude of additional factors influence their decision.
Runway length is perhaps the most obvious reason for choosing a runway not favored by the wind.
High performance aircraft often need more runway to meet their takeoff performance requirements and are more likely to accept a crosswind than be limited by runway length.
Traffic flow at uncontrolled airports may not be as methodical as tower directed traffic. The complexity of your mental map of traffic in the pattern will intensify as more aircraft join in. In deciding which runway to use, contemplation of what the other traffic is doing is paramount. If the runway in use is not what we may prefer, choosing a runway that is in conflict with the prevailing traffic may heighten the risk level. Adding complexity, IFR arrivals will often make a straight in approach.
During calm wind, at an uncontrolled airport with multiple runways, the risk of collision is increased if pilots are using more than one runway.
Some airports are one-way in and one-way out because of terrain. Nearby rising terrain may cause a pilot to choose a runway that offers lower terrain over which to make that initial climb, especially on a hot day. Similarly, a pilot may choose a departure runway based on the options available in the event of an engine failure after takeoff, that includes choosing a runway that avoids flight over water to minimize the potential for a ditching.
There are many other reasons to choose a runway not aligned with the wind including: selecting a grass runway for tail wheel aircraft; runways contaminated with snow and ice make a wise pilot chose a runway with a cleaner surface, even if that means accepting a crosswind; arriving at night pilots might favor a runway with good lighting and PAPI; for better lateral guidance, a runway served by a straight-in instrument approach may preferred, especially in diminished visibility.
Occasionally, pilots will choose a runway strictly on convenience such as a short taxi or one aligned with their direction of departure. Something as simple as not looking at a setting sun may influence runway choice. Sky condition and visibility (think localized fog and low clouds) can also play into the decision of which runway to use. Crosswind practice may put a pilot at odds with other traffic using the airfield.
The take-home message is that choosing a runway is often more than a matter of wind direction. With that understanding, we can recognize the need for enhanced vigilance and communication to ensure we avoid conflicts at uncontrolled airports.