VOR & Tacan Radial Intercept & Tracking
Operating aircraft with more than one engine introduces additional performance considerations and system management responsibilities. Understanding multiengine operations helps pilots recognize how asymmetric thrust, engine-out performance, and procedural discipline influence safety.
Introduction to VOR & Tacan Radial Intercept & Tracking
- Radial intercepts and tracking for both VORs and TACANs are flown identically
- Their purpose is to establish the airplane on a predetermine radial and to track it to a location, thereby aiding in navigation
- once established, pilots must then be able to make necessary corrections for the effects of wind
VOR & TACAN Radial Intercept Procedure
- Tune the station frequency and verify the station's Morse Code identifier
- Check the heading indicator with the magnetic compass
- Reset as necessary
- Turn the airplane to a heading to parallel the desired course, in the sae direction as the course to be flown
- With the Omni Bearing Selector (OBS), center the Course Deviation Indicator (CDI) with a TO flag indication (inbound), or a FROM flag indication (outbound) as appropriate
- Determine the difference between the radial to be intercepted and the radial presently on
- Double the difference to determine the interception angle
- May not be less than 20°, nor more than 90°
- Since the distance between radials varies with distance from the station (at 60 NM 1° between radials = 1 nm, 30 NM, 1° = 0.5 NM, etc.), the amount of intercept heading used must vary accordingly to prevent overshooting the desired course
- Rotate the OBS to select the desired radial ("FROM" Flag), or the course ("TO" Flag)
- Turn to the intercept heading determined and hold the heading constant until the CDI begins to center
- As the CDI begins to center, begin turning to the heading corresponding to the radial or course selected
- Track the radial (outbound) or course (inbound), as appropriate
- As proficiency increases, steps 3 and 4 may be eliminated
- Once the radial has been intercepted, proceed with VOR/TACAN Radial Tracking procedures
VOR & TACAN Radial Tracking Procedure
- After the course has been intercepted, maintain the heading that corresponds to the course selected
- If the CDI should move off center, re-intercept by beginning with a 20° change (intercept angle) in heading (intercept heading) toward the deflection of the CDI
- Maintain the intercept heading until the CDI re-centers, and then turn back to a new course heading by taking out 1/2 of the intercept angle
- For example, the airplane has drifted to the right of the 090° radial (outbound). To re-intercept the radial, a left turn is made to a heading of 070°. When the CDI re-centers, a right turn is made to maintain a new Course Heading of 080° (10° Wind Correction Angle)
- If the CDI should move off center, re-intercept by beginning with a 10° change in heading (intercept heading) toward the deflection of the CDI
- Maintain the intercept heading until the CDI re-centers, and then turn back to a new course heading by taking out 1/2 of the intercept angle
- For example, The airplane has drifted again to the right of the 090° radial (outbound). To re-intercept the radial, a left turn is made to a heading of 070° (10° change). When the CDI re-centers, a right turn is made to maintain a new Course Heading of 075° (5° change, 15° Wind Correction Angle now total)
- Wind conditions may require the use of intercept angles greater than 20° to change the direction of the CDI deflection however, the "bracketing" procedures above are still applicable
- Consider setting the heading bug to the heading to be flown so as to maintain the wind correction angle and therefore track
- Deviations:
- Consider what full-scale deflection means in terms of distance for the mode of flight the aircraft is in (enroute, terminal, etc.) or sensitivity relative to distance from a navigation station to understand how far off you are before inputting too much or too little of a correct
- Referencing a cross-track error (XTK) from the avionics or EFB, if available, to better guage your deviation
Airman Certification Standards
Conclusion
- Distinguishing the meaning of FROM and TO is important to avoid reverse sensing
- We fly a course TO, and intercept radials FROM
- Although these procedures are largely written for radio frequency NAVAIDs, GPS procedures are very similar
- Consider actual versus realized performance when doing any performance calculations
- Consider practicing maneuvers on a flight simulator to introduce yourself to maneuvers or knock off rust
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References
- Federal Aviation Administration - Pilot/Controller Glossary
- Instrument Flying Handbook