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PilotSchool Knowledge Base

Interpreting ADF and VOR Indications

Introduction

This section is designed to help aspiring pilots understand and interpret indications from Automatic Direction Finder (ADF) and VHF Omnidirectional Range (VOR) navigation aids. These skills are vital for accurately determining when an aircraft is passing abeam a NDB or VOR site and ensuring that the aircraft remains on track. Mastery of these radio navigation tools is crucial for obtaining the CASA PPL pilot license.

Automatic Direction Finder (ADF)

Functionality of ADF

The ADF is used to tune into Non-Directional Beacons (NDBs) on the AM band. The ADF needle always points toward the NDB, providing pilots with a simple, intuitive tool for navigation.

Identifying Passing Abeam of NDB

  • Relative Bearings: The key to recognizing when you are passing abeam an NDB is by observing the ADF needle’s position. When the needle points directly to the side, typically at 90 degrees to the aircraft’s heading, the aircraft is abeam the NDB station.

  • Verification Process:

    • Tune: Set the ADF to the correct NDB frequency.
    • Identify: Confirm the NDB signal using Morse code ident.
    • Maintain Track: Utilize the needle’s position to adjust heading, ensuring lateral alignment with the intended flight path.

ADF Practical Use

  • Knowing when you are passing the NDB site is essential for position reports and ensuring that correcting measures can be taken to remain on course.

VHF Omnidirectional Range (VOR)

Functionality of VOR

VOR stations provide 360-degree radials which help aircraft determine their position relative to the station through radials and the Course Deviation Indicator (CDI).

Recognizing Passing Abeam of VOR

  • Course Deviation Indicator (CDI): The CDI shows how far you are from the selected radial. A center-disc CDI indicates that your aircraft is on the selected radial.

  • Station Passage: There are no direct visual cues on the VOR for passing directly overhead the station, but pilots can typically confirm passage when noting a loss in significant directional command, evidenced by a rapid change in CDI readings.

Verifying On-Track with VOR

  • CDI Centering: When the CDI is centered with the ‘TO/FROM’ indicator demonstrating stability in the chosen radial, the aircraft is on track.

  • Drift Compensation and Adjustments:

    • Recognizing CDI deviations employ the 1-in-60 rule, where pilots can calculate off-track distances and make necessary heading adjustments.

Practical Techniques for ADF and VOR Navigation

TITS Method

  • Tune: Correctly dial into the navaid.
  • Identify: Verify using the ident signal.
  • Test: Ensure the instrument’s reliable performance.
  • Select: Choose the appropriate course or bearing.

Simulation and Practice

  • Use simulators like Microsoft Flight Simulator or other practice tools to simulate navigation scenarios, helping prepare for real-world conditions.

  • Engaging in practical exercises enhances situational awareness and aids in mastering navigation techniques.

Combining ADF and VOR

  • Integration: Use ADF for directional cues and VOR for confirming position with radial alignment. Understanding, calculating, and correcting off-track distances using both ADF and VOR will ensure effective navigation.

  • Distance Assessment: Pilot proficiency in handling these readings allows for quick, accurate corrections when passing abeam navigation aids, essential for maintaining or regaining a correct flight path.

Conclusion

Understanding how to identify and interpret ADF and VOR indications is crucial for trajectory management and efficient navigation, particularly when knowing when you are passing abeam an NDB or a VOR station. Combining these skills with effective practice methods will prepare pilots for successful navigation during both training and practical flight experiences.

Learning Resources