What is the maximum permissible difference between designated radial and aircraft equipment?

What is the maximum permissible difference between designated radial and aircraft equipment?

• A. 1 degree
• B. 2 degrees
• C. 4 degrees
• D. 6 degrees

Answer: (C)

In VOR navigation, the line you intend to fly is a radial from a navigation aid, and your aircraft’s navigation instruments must show you are aligned with that radial within a small angular tolerance. The maximum permissible difference between the designated radial and what the aircraft indicates is four degrees. This allowance accounts for inevitable instrument and signal limitations, such as receiver tolerance and signal quality, so you can reliably identify and stay on the intended radial. Think of it in practical terms: at 10 nautical miles from the VOR, a 4-degree deviation translates to about 0.7 nautical miles of cross-track error. That balance keeps you on course without being so strict that normal equipment errors would push you off the line, nor so loose that you drift substantially off track. Smaller tolerances (like 1 or 2 degrees) would be unrealistically tight given typical VOR accuracy, while a larger tolerance (such as 6 degrees) would allow a larger off-course deviation than is acceptable for precise navigation.

In VOR navigation, the line you intend to fly is a radial from a navigation aid, and your aircraft’s navigation instruments must show you are aligned with that radial within a small angular tolerance. The maximum permissible difference between the designated radial and what the aircraft indicates is four degrees. This allowance accounts for inevitable instrument and signal limitations, such as receiver tolerance and signal quality, so you can reliably identify and stay on the intended radial.

Think of it in practical terms: at 10 nautical miles from the VOR, a 4-degree deviation translates to about 0.7 nautical miles of cross-track error. That balance keeps you on course without being so strict that normal equipment errors would push you off the line, nor so loose that you drift substantially off track. Smaller tolerances (like 1 or 2 degrees) would be unrealistically tight given typical VOR accuracy, while a larger tolerance (such as 6 degrees) would allow a larger off-course deviation than is acceptable for precise navigation.