When obstacles are in the approach or departure routes on a ___ to __ ratio must be used to lay out the landing site (___ to ___ at night).

When obstacles are in the approach or departure routes on a ___ to __ ratio must be used to lay out the landing site (___ to ___ at night).

• A. 14:1 during day, 10:1 during night
• B. 10:1 during day, 14:1 during night
• C. 8:1 during day, 8:1 during night
• D. 12:1 during day, 12:1 during night

Answer: (B)

When obstacles are in the approach or departure routes, you plan the landing site using a horizontal-to-vertical clearance ratio. This ratio tells you how far out from the landing site you must keep obstacles of a given height, forming a safe corridor for the approach or departure. The reason the night rule uses a larger ratio is that visibility and depth perception are worse after dark, so you need more buffer to avoid hazards. The best answer uses 10:1 during the day and 14:1 at night. That means for every unit of obstacle height, you require ten units of horizontal clearance in daylight, and fourteen units at night, to lay out a safe landing area. For example, an obstacle 10 feet tall would require about 100 feet of horizontal clearance during the day and about 140 feet at night. The other options don’t reflect the increased clearance needed at night, or they swap or keep the same ratio regardless of lighting, which wouldn’t align with the safety margin needed after dark.

When obstacles are in the approach or departure routes, you plan the landing site using a horizontal-to-vertical clearance ratio. This ratio tells you how far out from the landing site you must keep obstacles of a given height, forming a safe corridor for the approach or departure. The reason the night rule uses a larger ratio is that visibility and depth perception are worse after dark, so you need more buffer to avoid hazards.

The best answer uses 10:1 during the day and 14:1 at night. That means for every unit of obstacle height, you require ten units of horizontal clearance in daylight, and fourteen units at night, to lay out a safe landing area. For example, an obstacle 10 feet tall would require about 100 feet of horizontal clearance during the day and about 140 feet at night.

The other options don’t reflect the increased clearance needed at night, or they swap or keep the same ratio regardless of lighting, which wouldn’t align with the safety margin needed after dark.