FAA Instrument Flight Instructor (FII)IFR Procedures and ApproachesMedium
A pilot is performing a VOR receiver accuracy check using a VOR test facility (VOT). The aircraft's CDI indicates a 10-degree deflection to the left with a 'TO' indication when tuned to the VOT frequency. What is the status of the VOR receiver?
- AThe VOR receiver is indicating a false 'TO' flag, rendering it unreliable.
- BThe VOR receiver requires recalibration, but is serviceable for VFR flight.
- CThe VOR receiver is within acceptable limits.
- DThe VOR receiver is unserviceable and cannot be used for IFR flight.
Show answer & explanationAnswer & explanation
Correct answer: D. The VOR receiver is unserviceable and cannot be used for IFR flight.
According to 14 CFR 91.171, a VOR receiver check using a VOT must indicate a 0-degree deflection (or within +/- 4 degrees) with a 'FROM' indication for 180 degrees, or a 'TO' indication for 360 degrees. A 10-degree deflection exceeds the allowable tolerance of +/- 4 degrees for a VOT check, making the receiver unserviceable for IFR flight.
Why the other options are wrong
- A. The 'TO' flag is likely correct for a 360-degree radial, but the deflection is the issue.
- B. The receiver is unserviceable for IFR; VFR use is not explicitly covered by IFR VOR check standards.
- C. A 10-degree deflection is outside the +/- 4-degree tolerance for a VOT check.
VOT Accuracy Check Indications
A VOR receiver check using a VOT must indicate 0 degrees with a 'FROM' indication for 180 degrees, or 0 degrees with a 'TO' indication for 360 degrees, with a maximum allowable error of ±4 degrees.
- VOT transmits a 360-degree radial in all directions.
- CDI should indicate 0 degrees with a 'TO' flag for 360 radial.
- Maximum allowable error is ±4 degrees for VOT check.
- Required within 30 days before IFR flight.
Memory trick: Verify Our Radios: Four Degrees or More, No IFR Door!