FAA Aircraft Dispatcher (ADX)Navigation and ATCMedium
During a periodic VOR accuracy check using a VOT (VOR Test Facility), the CDI centers with a 358° radial displayed with a FROM indication. What is the maximum allowable error for this check to be considered satisfactory?
- A±2 degrees
- B±10 degrees
- C±6 degrees
- D±4 degrees
Show answer & explanationAnswer & explanation
Correct answer: D. ±4 degrees
Per 14 CFR 91.171, a VOT check requires the CDI to center with a TO/FROM indication of 000° radial (or 180° reciprocal), within ±4 degrees. The pilot recorded 358°, only 2 degrees off, which is within the ±4 degree tolerance.
Why the other options are wrong
- A. ±2 degrees is tighter than the regulatory allowance for a VOT check.
- B. ±10 degrees is not a recognized tolerance for any VOR operational check.
- C. ±6 degrees applies to airborne checks using a designated ground checkpoint, not VOT.
VOR Operational Checks
14 CFR 91.171 specifies tolerances for VOR accuracy checks including VOT, ground checkpoint, airborne checkpoint, and dual VOR comparison.
- VOT check: ±4°
- Ground/airborne checkpoint: ±4° ground, ±6° airborne
- Dual VOR check: 4° max difference between receivers
- Checks must be logged with date, place, error, and signature
Memory trick: VOT is 4, Air is 6, Dual is 4 between two