A runway is considered contaminated when more than 25% of the surface area is covered by which conditions?

• A. Water/slush more than 3 mm deep; loose snow more than 20 mm deep; compacted snow or ice
• B. Water only
• C. Mud only
• D. Ice with visible cracks

Answer: (A)

Runway contamination is judged by how much of the surface is covered by certain substances, and by specific depths for those substances. The intention is to flag surfaces where the friction and drainage could be seriously affected, not just minor dampness. The best choice lists the actual contaminants that count (water or slush, loose snow, and snow that’s compacted or ice) and gives clear depth thresholds that matter: water or slush deeper than 3 mm, loose snow deeper than 20 mm, or any depth of compacted snow or ice. When more than a quarter of the runway surface shows any of these conditions, the surface is considered contaminated, which is the scenario the question is testing.

The other options don’t fit because they don’t reflect the full range of counted contaminants or the depth criteria. Water alone doesn’t capture the other substances that can contaminate a surface, mud isn’t part of the standard thresholds, and ice with cracks doesn’t specify coverage or depth thresholds, which are essential to determining contamination.