DME accuracy requirements are which of the following?

DME accuracy requirements are which of the following?

• A. 5% of total distance, or 1.0, whichever is greater
• B. 3% of total distance, or 0.5, whichever is greater
• C. 2% of total distance, or 0.25, whichever is greater
• D. 4% of total distance, or 0.75, whichever is greater

Answer: (B)

DME accuracy is defined by how close the measured distance can be to the true distance, and the standard uses both a percentage and a fixed floor to cover different ranges. The allowable error is 3% of the distance, or 0.5 nautical miles, whichever is greater. This means at short ranges the 0.5 NM floor dominates to avoid insisting on unrealistically small errors, while at longer ranges the percentage dominates so the error scales with distance. For example, at 20 NM, 3% is 0.60 NM, which is greater than 0.5 NM, so the allowable error is 0.60 NM. At 5 NM, 3% is 0.15 NM, which is less than 0.5 NM, so the allowable error is 0.5 NM. This combination provides consistent performance across the flight envelope. Other options don’t match this established specification, which is why this choice best describes the DME accuracy requirement.

DME accuracy is defined by how close the measured distance can be to the true distance, and the standard uses both a percentage and a fixed floor to cover different ranges. The allowable error is 3% of the distance, or 0.5 nautical miles, whichever is greater. This means at short ranges the 0.5 NM floor dominates to avoid insisting on unrealistically small errors, while at longer ranges the percentage dominates so the error scales with distance.

For example, at 20 NM, 3% is 0.60 NM, which is greater than 0.5 NM, so the allowable error is 0.60 NM. At 5 NM, 3% is 0.15 NM, which is less than 0.5 NM, so the allowable error is 0.5 NM. This combination provides consistent performance across the flight envelope.

Other options don’t match this established specification, which is why this choice best describes the DME accuracy requirement.