For safe operations, aircraft should land and take off against the wind. The runway center line should not deviate from the prevailing wind direction by more than what angle?

Introduction:
Runway orientation aims to maximize wind coverage and minimize crosswind components for typical operations. Excessive angular deviation between runway center line and prevailing wind direction increases crosswind, reducing safety and operational availability.

Given Data / Assumptions:

• Standard practice: take-off and landing into the wind.
• Acceptable deviation is subject to crosswind limits and planning criteria.

Concept / Approach:

Many design guidelines use a practical limit that the runway alignment should not differ from the dominant wind direction by more than about 20°, which controls the crosswind component to acceptable values for most aircraft fleets considered in basic planning.

Step-by-Step Solution:

Verification / Alternative check:

Wind-rose analysis often targets 95% wind coverage under allowable crosswind limits. A 20° alignment tolerance corresponds well with these thresholds for general planning.

Why Other Options Are Wrong:

• 10°: Overly restrictive; may force unnecessary additional runways.
• 30° or 40°: Too permissive; crosswind components would often exceed limits.
• 15°: Not the common benchmark used in many introductory design problems.

Common Pitfalls:

• Confusing angular deviation criteria with crosswind speed limits (e.g., 25–37 km/h thresholds).

Final Answer:

20°