One assumption of obstacle departure procedures is crossing the runway threshold at how many feet AGL?

• A. 800 ft AGL
• B. 400 ft AGL
• C. 200 ft AGL
• D. 1000 ft AGL

Answer: (B)

Obstacle departure procedures are built to guarantee obstacle clearance from the moment you reach the runway end by using a fixed crossing height above the surface. The standard crossing height for these procedures is 400 feet AGL, which provides a reliable margin for the initial climb and any required turns without needing ATC guidance. If the local environment has higher obstacles, the procedure will note a different crossing height or path.

Why 400 ft AGL works well: it gives you enough climb performance and room to accelerate and ascend away from obstacles right after takeoff, while keeping the procedure practical for typical aircraft performance. The other numbers would either understate or overstate the necessary clearance and are not the usual assumed value for standard ODPs.

Remember that AGL means height above the ground at the runway, not above sea level, and field elevation affects your actual altitude above mean sea level.