Intercepting and Tracking Navigational Systems and DME Arcs

Objective

By the end of this lesson, the student will demonstrate proficiency in intercepting and tracking navigational systems and DME arcs in simulated or actual instrument meteorological conditions. The student will tune, identify, and utilize both ground-based (VOR/DME) and satellite-based (GPS/RNAV) navigation systems to intercept and maintain courses and arcs within ACS standards. Performance will meet the requirements of FAA-S-ACS-14, Area of Operation V, Task A (IH.V.A), maintaining airspeed ±10 knots, altitude ±100 feet, selected headings ±5°, and CDI deflection no greater than ¾-scale (or DME arc ±1 NM).

Content

Ground-Based Navigation Systems (IH.V.A.K1)

VOR (VHF Omnidirectional Range) Fundamentals

VOR stations transmit 360 radials in all directions, providing magnetic course guidance to equipped aircraft. Unlike airplane operations where VOR tracking is routine, helicopter IFR operations require heightened scan discipline due to higher single-pilot workload and the absence of autopilot in most training helicopters.

VOR Components and Operation:

• VOR transmits on frequencies between 108.0 and 117.95 MHz
• Each station has a three-letter Morse code identifier that must be positively identified before use (14 CFR 91.171)
• Radials are defined as courses FROM the station
• The VOR receiver displays the selected course (OBS setting) and whether the aircraft is left or right of that course via the CDI
• TO/FROM indicator shows relationship to station based on selected radial

Course Orientation and Determination:

When intercepting a VOR radial, think of the radial as a spoke on a wheel radiating from the station. If you want to track TO the station on the 360 radial (magnetic north), you would fly a heading of approximately 360° with wind correction. If tracking FROM the station on the 180 radial, you would fly approximately 180° with wind correction—but in both cases, you select the inbound course (360°) in your OBS.

The key concept for helicopter pilots: VOR tracking requires constant attention to small heading corrections. Unlike airplanes with autopilots or higher speeds that smooth out oscillations, helicopters at slower speeds (80-90 knots typical) require more frequent, smaller corrections to maintain centerline.

VOR Equipment Tests and Regulations (14 CFR 91.171):

Before using VOR for IFR operations, the system must be checked within the preceding 30 days using one of these methods:

• VOT (VOR Test Facility): CDI centers with OBS at 0° (±4° tolerance) with FROM indication, or 180° (±4°) with TO indication
• Certified Airborne Checkpoint: ±4° of published radial
• Certified Ground Checkpoint: ±4° of published radial
• Airborne Checkpoint (dual VOR check): Two VOR systems must agree within 4° of each other
• Selected Radial Over Known Ground Point: ±6° of published radial

The pilot or authorized technician must record the date, place, bearing error, and signature in the aircraft logbook or other permanent record. This is a common gotcha—you cannot legally use VOR for IFR without a current check, regardless of how well it appears to be working.

VOR Intercepting Procedures:

1. Tune and Identify: Select the frequency and confirm the Morse code identifier (never trust frequency alone—stations can be off the air for maintenance)
2. Determine Position: Rotate the OBS until the CDI centers with a FROM indication—this is the radial you are currently on
3. Select Desired Course: Rotate OBS to the desired radial or course
4. Choose Intercept Angle: Use 30° for intercepts less than 20° from current heading; use 45° for intercepts 20-70° from current heading; use 90° for intercepts greater than 70° or when cleared “direct”
5. Fly Intercept Heading: Maintain heading until CDI begins to center
6. Turn to Track: When CDI is one dot from center, turn to the desired course and apply wind correction
7. Bracket the Course: Make small heading corrections (5-10° initially) to determine wind correction angle; narrow corrections as you refine the wind

DME (Distance Measuring Equipment):

DME provides slant-range distance in nautical miles from the aircraft to the ground station. DME operates on UHF frequencies (962-1213 MHz) and is often co-located with VOR or ILS facilities.

DME Characteristics:

• Displays slant-range distance (not horizontal distance)—at high altitudes close to the station, DME reads higher than actual ground distance
• Groundspeed and time-to-station readouts available on most units
• DME channels are automatically paired with VOR/ILS frequencies—tune the VOR, get the DME automatically
• DME accuracy: ±0.5 NM or ±3% of distance, whichever is greater

DME Arc Procedures:

A DME arc is a curved path maintaining constant distance from a DME station. Common uses include transitioning from enroute to approach phases or as part of instrument approach procedures.

Arc Flying Technique (10° Reference Method):

1. Lead the Turn: Begin turn to intercept the arc approximately 0.5 NM before reaching arc distance
2. Initial Turn: Turn to place the station 90° off the nose (referenced to the tail or 90° relative bearing)
3. Fly Reference Arc: Turn 10° toward the station—fly this heading until DME decreases and station bearing changes by 10°
4. Adjust: Turn another 10° toward station; repeat the process
5. Monitor Distance: If inside the arc (DME decreasing), turn toward the station; if outside the arc (DME increasing), turn away from the station
6. ACS Standard: Maintain arc ±1.0 NM

For helicopters, DME arcs present unique challenges. At typical helicopter approach speeds (60-90 knots), the turn radius is smaller and corrections happen more rapidly than in airplanes. The pilot must maintain an aggressive scan between the heading indicator, DME, and CDI (if tracking to a radial). Single-pilot workload is high—practice is essential.

Arc-to-Radial Transition:

When intercepting a radial from a DME arc:

1. Lead the Radial: Begin turn 5° prior to desired radial (10° for helicopters turning at slower speeds to accommodate turn radius)
2. Select Course: Set OBS to inbound course
3. Roll Out: Intercept radial and track inbound using standard bracketing technique
4. Confirm Position: Cross-check DME distance decreasing to station

Regulations for Ground-Based Navigation (14 CFR 91.171, 91.205):

• IFR operations require VOR system to be checked within preceding 30 days (14 CFR 91.171)
• DME is required for IFR flight at FL240 and above (14 CFR 91.205(d))
• DME required if procedure specifically requires it (e.g., “DME REQUIRED” on approach plate)
• ATC may assign DME arcs—helicopter must be equipped and proficient

Satellite-Based Navigation Systems (IH.V.A.K2)

GPS/RNAV Fundamentals:

GPS (Global Positioning System) revolutionized aviation navigation by providing accurate three-dimensional position anywhere on earth. Modern IFR GPS systems are certified for enroute, terminal, and approach operations under TSO-C129, TSO-C145, or TSO-C146 standards.

GPS System Components:

• Space Segment: 24+ satellites in six orbital planes transmitting timing signals
• Control Segment: Ground stations monitoring satellite health and orbit accuracy
• User Segment: Aircraft GPS receiver processing satellite signals to compute position

GPS determines position by measuring distance to multiple satellites (trilateration). The receiver needs signals from at least four satellites: three for position (latitude, longitude, altitude) and one for time correction.

RAIM (Receiver Autonomous Integrity Monitoring):

RAIM is a critical safety feature for GPS navigation. Because GPS signals can be degraded, interrupted, or corrupted, RAIM uses redundant satellite signals to detect when the position solution is unreliable.

RAIM Requirements:

• Minimum 5 satellites required for RAIM (6 for fault detection and exclusion)
• RAIM availability must be checked before IFR flight (via Flight Service, Garmin, ForeFlight, etc.)
• RAIM failure annunciated by “LOI” (Loss of Integrity), “UNABLE RNP,” or similar message
• Pilot Action on RAIM Loss: Immediately transition to another form of navigation (VOR, ADF if available) and advise ATC

RAIM Prediction: Before departure, pilots must verify RAIM availability for the ETA at destination ±15 minutes. If RAIM is unavailable, the flight cannot be conducted under GPS guidance unless alternate means of navigation are available and flight-planned.

WAAS (Wide Area Augmentation System):

WAAS enhances GPS accuracy and integrity by using ground reference stations to detect GPS signal errors and broadcast corrections via geostationary satellites.

WAAS Benefits:

• Position accuracy improves from ±100 meters to ±1-3 meters
• Provides lateral and vertical guidance for precision-like approaches (LPV)
• Continuous integrity monitoring—no RAIM prediction required for WAAS approach operations
• WAAS receivers revert to non-WAAS mode if augmentation lost—monitor annunciations

Caution for Helicopters: Most training helicopters use panel-mount GPS (e.g., Garmin GNS 430W/530W or GTN 650/750). These are certificated for IFR but require thorough database and preflight checks. Portable GPS (e.g., iPad with ForeFlight) is not approved as primary navigation for IFR flight under 14 CFR 91.205.

GPS Navigation Database (14 CFR 91.511):

GPS databases must be current for IFR operations. The navigation database includes waypoints, airways, instrument procedures, and obstacle data.

Database Currency Requirements:

• Database expires every 28 days (AIRAC cycle)
• Expired database may be used for enroute and terminal operations if pilot verifies each selected waypoint for accuracy (impractical and not recommended)
• Expired database cannot be used for approach operations
• Verify database currency during preflight—most units display expiration date on startup

GPS Interference and Limitations:

GPS signals are relatively weak and susceptible to interference:

• Military GPS Testing: NOTAMs issued for GPS testing—may degrade or eliminate service in large geographic areas
• Solar Activity: Severe space weather can disrupt GPS signals
• Terrain Masking: Mountains or steep terrain can block satellite signals (rare but possible in confined areas)
• Receiver Limitations: Older non-WAAS units have limitations for certain approach types

Pilot Responsibility: Check NOTAMs for GPS interference testing. AIM 1-1-17 provides guidance. If GPS is primary means of navigation and NOTAM indicates outage, file using alternative navigation (VOR, airways) or cancel IFR.

GPS Intercepting and Tracking Procedures:

Modern GPS systems simplify course intercepts through automation, but the pilot must understand underlying logic and maintain situational awareness.

Basic GPS Intercept (Direct-To Function):

1. Select Waypoint: Use Direct-To function (usually “D→” button) and enter waypoint identifier
2. Activate: GPS computes direct course and provides steering guidance via CDI
3. Monitor Track: CDI deflection shows deviation from desired track (not radial as in VOR—track is direct ground path)
4. Fly Heading: Establish intercept heading toward CDI needle
5. Wind Correction: GPS automatically updates ground track; pilot adjusts heading to maintain CDI centered

RNAV Course Intercepts:

When ATC assigns “proceed direct” to a waypoint on your flight plan or approach:

1. Verify Waypoint: Confirm correct waypoint in GPS database (look at map page, confirm identifier)
2. Activate: Use Direct-To or activate leg of flight plan
3. Intercept: Turn to intercept course at appropriate angle (30-45°)
4. CDI Sensitivity: Be aware of CDI scaling—enroute (±5 NM full scale), terminal (±1 NM full scale), approach (±0.3 NM full scale for LNAV/VNAV and LPV)

GPS Arc Procedures:

GPS-based arcs (RF legs—Radius to Fix) are computed by the navigator and require minimal pilot input. The GPS steers the aircraft along the curved path.

1. Verify Arc in Flight Plan: Confirm arc is part of active procedure
2. Monitor Track: Follow CDI steering—GPS computes turn radius and steering commands
3. Airspeed Control: Maintain consistent airspeed—fluctuations cause CDI oscillations
4. Roll Coordination: Use coordinated turns (no slip/skid)—GPS relies on consistent ground track

Regulations for GPS/RNAV Navigation:

• GPS equipment must be IFR-certified (TSO-C129 or higher) and installed per STC or TC (14 CFR 91.205)
• GPS substitution for ADF and DME allowed per AIM 1-2-3 (for most operations)
• GPS may not replace VOR for VOR operational checks (14 CFR 91.171)
• GPS approach requires approach procedure loaded from current database—cannot use vectors-to-final with outdated data
• Helicopter-specific GPS approaches require helicopter eligibility statement in AFM supplement

Risk Management (IH.V.A.R1, R2, R3)

IH.V.A.R1: Management of Automated Navigation and Autoflight Systems

Modern GPS navigators reduce workload but introduce automation risks:

Mode Awareness: Always know what mode the GPS is in—enroute, terminal, approach, OBS mode, etc. Mode transitions happen automatically based on position, and unexpected mode changes can confuse pilots. For example, GPS may sequence to next waypoint when you intended to hold at current waypoint—verify active leg and suspend auto-sequencing if needed.

Automation Complacency: “Children and Magenta Line syndrome.” Pilots over-rely on GPS steering and stop cross-checking with VOR, pilotage, or ATC radar. Develop habit: verbally state your position every 5-10 minutes (“10 miles west of XYZ VOR, tracking direct ABC”). This forces situational awareness.

Buttonology Under Pressure: In IMC with high workload, pilots fumble with GPS interfaces. Know your GPS cold—chair-fly menu structures, Direct-To shortcuts, flight plan modifications. If task-saturated, tell ATC: “Need a minute to reprogram GPS, request heading to fly.” Controllers respect honest communication.

Autopilot Management (if installed): Few training helicopters have autopilots, but higher-end IFR helicopters (e.g., Robinson R66, Airbus H125) may have them. Autopilot coupled to GPS can mask navigation errors. If autopilot is tracking a wrong course, it will do so flawlessly until you notice. Always verify autopilot is tracking the correct course/waypoint before engaging. Disengage and hand-fly if any doubt.

Risk Mitigation:

• Brief GPS setup before departure (flight plan loaded, waypoints verified, database current)
• Use “WIRE” check before approach: Waypoint verified, Instruments set, Radios tuned, Everything briefed
• Cross-check GPS against VOR or ATC radar when possible
• If GPS fails or RAIM lost, immediately transition to VOR or request vectors—do not attempt to troubleshoot in IMC at low altitude

IH.V.A.R2: Distractions, Task Prioritization, Loss of Situational Awareness, or Disorientation

Instrument navigation in helicopters is a high-workload environment. Unlike fixed-wing, helicopters lack stability augmentation in most training aircraft. Every control input requires constant correction. Add navigation, communication, and systems management, and task saturation looms.

Common Distractions:

• Programming GPS while maneuvering or during critical phases
• ATC frequency changes or amended clearances during intercepts
• Passenger questions or needs (if applicable—minimize during IMC)
• Equipment malfunctions (e.g., radios, vacuum pump, GPS failure)

Task Prioritization (Aviate, Navigate, Communicate):

1. Aviate: Maintain aircraft control—altitude, airspeed, heading. If you lose the bubble (unusual attitude or disorientation), refer to attitude indicator and recovery procedures first. Do not attempt navigation until aircraft is stable.
2. Navigate: Once aircraft is stable, establish position and track. Use available navigation aids (GPS, VOR, ATC radar).
3. Communicate: Inform ATC of your status. If you need help, ask: “Request vectors” or “Unable current clearance, request heading.”

Loss of Situational Awareness:

Situational awareness is the mental picture of where you are, where you’re going, and what’s happening around you. It degrades rapidly during high workload.

Symptoms:

• Uncertainty about aircraft position (“Where am I?”)
• Confusion about ATC clearance (“What did they say?”)
• Fixation on one instrument or task
• Failure to anticipate next action (e.g., surprised by course intercept)

Mitigation:

• Verbalize position and intentions aloud: “I am 5 miles north of XYZ, intercepting the 180 radial inbound, expect clearance for approach in 10 miles.”
• Use approach plate or enroute chart as visual reference—mark your position with finger or pencil
• Request clarification from ATC without hesitation: “Verify clearance” or “Say again”
• If disoriented, confess to ATC: “Request vectors, having trouble with navigation.” Controllers are trained to help.

Spatial Disorientation:

Disorientation is a leading cause of helicopter IMC accidents. Vestibular illusions (somatogravic, leans, Coriolis) make you feel like you’re in a bank when wings are level, or climbing when descending.

Prevention:

• Trust your instruments completely—ignore body sensations
• Maintain strict instrument scan (attitude, altitude, heading, airspeed, turn coordinator, VSI)
• Avoid unnecessary head movements (Coriolis effect)
• If you feel disoriented, increase focus on attitude indicator—stabilize pitch and bank first

Recovery: If you enter unusual attitude (nose-low or nose-high with high bank), use standard recovery procedures from FAA-H-8083-15B Chapter 8. Do not attempt to navigate until recovered.

IH.V.A.R3: Limitations of the Navigation System in Use

Every navigation system has limitations. Pilots must understand and respect these.

VOR/DME Limitations:

• Line-of-Sight: VOR signals are VHF and blocked by terrain. At low altitudes (typical for helicopters), VOR range is limited. Use formula: Range (NM) ≈ 1.23 × √(altitude in feet). At 2,000 feet AGL, expect 55 NM range; at 5,000 feet, 87 NM.
• Station Passage: VOR becomes unreliable within 1-2 NM of station (cone of confusion). CDI oscillates; TO/FROM flips erratically. Maintain last known heading until clear of station.
• DME Slant Range Error: At high altitudes close to station, DME reads higher than actual horizontal distance. At 6,000 feet AGL and 1 NM horizontal from station, DME reads 1.2 NM. Not significant in most helicopter operations (we fly low), but be aware.
• Service Volume: VOR service volumes are classified (Terminal: 25 NM up to 12,000 feet; Low Altitude: 40 NM up to 18,000 feet; High Altitude: 100 NM). Check Chart Supplement for specific station limitations.

GPS Limitations:

• Satellite Geometry: Poor satellite geometry (Position Dilution of Precision—PDOP) degrades accuracy. GPS will annunciate if PDOP exceeds limits.
• RAIM Unavailability: As discussed, if fewer than 5 satellites visible, RAIM is lost, and GPS cannot guarantee integrity. Immediately revert to VOR or request vectors.
• GPS Outages: Military GPS testing or interference can make GPS unusable in entire regions—check NOTAMs.
• Database Limitations: GPS database may not include all obstacles, especially wires and towers below 200 feet AGL. Never rely solely on GPS for obstacle clearance in low-level helicopter operations.
• CDI Scaling: GPS CDI sensitivity changes automatically (enroute: ±5 NM, terminal: ±1 NM, approach: ±0.3 NM). Same needle deflection means vastly different lateral error depending on phase of flight. In approach mode, ¾-scale deflection is only 750 feet off course—respond immediately.

Autopilot Limitations (if installed):

• Most training helicopters (R22, R44, Schweizer 300) have no autopilot
• Higher-performance helicopters may have single-axis (heading hold) or two-axis (heading and altitude hold) autopilots
• Autopilots do not sense weather, traffic, or obstacle hazards—pilot must remain vigilant
• Autopilot may disengage unexpectedly due to control forces, turbulence, or system faults—be ready to hand-fly immediately

Mitigation:

• Always have backup navigation plan (second VOR, GPS, or ATC radar vectors)
• Brief limitations before flight: “If GPS fails after XYZ, I will use ABC VOR; if that fails, I will request vectors”
• Do not accept clearances you cannot navigate—speak up to ATC: “Unable DME arc, request alternate routing”
• Practice raw data navigation (VOR only, no GPS) regularly to maintain proficiency

Summary of Key Regulatory References

• 14 CFR 91.171: VOR check requirements (every 30 days for IFR)
• 14 CFR 91.205(d): IFR equipment requirements (VOR, DME at FL240+, GPS if used as primary)
• 14 CFR 91.511: GPS database currency (28-day AIRAC cycle)
• AIM Chapter 1-1-17: GPS/WAAS guidance and RAIM
• AIM Chapter 1-2-3: GPS substitution for ADF and DME
• FAA-H-8083-15B Chapter 9: Navigation systems for helicopters
• FAA-H-8083-21B Chapter 3: Risk management and human factors
• FAA-S-ACS-14 IH.V.A: Intercepting and Tracking Navigational Systems and DME Arcs

Schedule

Total Time: 3.0 hours (0.5 ground, 1.75 flight, 0.25 debrief)

Equipment

Required References

• FAA-S-ACS-14: Instrument Rating Airplane Airman Certification Standards (current edition)
• FAA-H-8083-15B: Instrument Flying Handbook
• FAA-H-8083-21B: Helicopter Flying Handbook
• 14 CFR Part 91: General Operating and Flight Rules
• AIM: Aeronautical Information Manual (current edition)
• Chart Supplement (formerly A/FD) for local VOR/DME station information
• IFR Enroute Low Altitude Chart (appropriate region)
• Terminal Procedures Publication (approach plates)

Materials and Visual Aids

• IFR-certified helicopter with VOR/DME and IFR-approved GPS (e.g., Garmin GNS 430W/530W, GTN 650/750, or equivalent)
• View-limiting device (hood or foggles) for simulated IMC
• VOR receiver test record (logbook or separate form) showing currency
• GPS database expiration date documentation
• RAIM prediction tool or printout (via ForeFlight, Garmin Pilot, FSS, or fltplan.com)
• NOTAMs for GPS outages in planned area
• Whiteboard or tablet for drawing VOR radials, DME arcs, intercept angles
• Navigation log or flight plan form
• Kneeboard with IFR enroute chart and approach plates
• Stopwatch or timer for time-based tracking exercises

Optional Visual Aids

• VOR navigation demonstration tool (physical or iPad app showing radials and aircraft position)
• GPS simulator or desktop trainer (Garmin Trainer software)
• Video demonstration of DME arc procedures
• Chart with pre-marked DME arc and radials for visual briefing
• Ryan Dale’s ASA Helicopter Oral Exam Guide (Instrument chapter for additional study)

Safety Equipment

• Functional attitude indicator and backup instruments (per 14 CFR 91.205(d))
• Functional communication and navigation equipment (dual comm radios recommended)
• Current charts and approach plates (paper or approved EFB)
• Flashlight with red lens (for night operations if applicable)

Instructor Actions

1. Begin with Targeted Questioning: Ask student to explain the difference between a VOR radial and a GPS track. Clarify misconceptions. Ask: “If you’re on the 090 radial of a VOR, which direction is the station from you?” (Answer: West—radials are FROM the station.) This sets the foundation for spatial awareness.

2. Demonstrate VOR Tuning and Identification: In the helicopter, tune a nearby VOR frequency, turn up audio, and identify the three-letter Morse code. Show student how to reference the Chart Supplement or approach plate for identifier and frequency. Emphasize: “Never use a VOR without positive identification—frequency alone is not enough. Stations can be off the air, and you might be tuned to something else.”

3. Demonstrate Position Determination Using VOR: Rotate the OBS while monitoring the CDI. Explain: “When the needle centers with a FROM indication, you’re on that radial. Right now, we’re on the 135 radial, meaning the station is northwest of us.” Have student verify on chart.

4. Demonstrate Intercept Angles: Explain the “30-45-90 rule.” Draw on whiteboard: “If you’re 10° off course, use 30° intercept. If you’re 40° off, use 45°. If you’re 90° or more off, turn direct (90° intercept).” Show example: “We’re tracking 270 to the VOR, but we want to intercept the 360 radial inbound (course 180°). That’s 90° difference, so we’ll turn to 270° heading to intercept, then turn inbound to 180° as the CDI centers.”

5. Demonstrate VOR Course Bracketing: Fly a VOR radial and talk aloud: “I’m drifting right—needle is one dot left. I’ll add 10° left (now heading 170°). Wait for needle to center. Now centered—wind correction is 10° left, so I’ll fly 170° instead of 180°. If drift continues, I’ll adjust to 165°. Bracketing narrows the wind correction until we find the exact heading to track centerline.”

6. Demonstrate DME Arc Setup: Brief the student before flight: “We’ll intercept the 15 DME arc at the 090 radial. I’ll lead the turn by 0.5 NM—so at 14.5 DME, I’ll turn left to place the station 90° to the right (heading 360° if station is at 090° relative bearing). Then I’ll fly 10° toward the station—350°—until the station moves aft by 10°, then turn another 10° toward it.” Show this visually on the chart with pencil marks.

7. Demonstrate DME Arc Flight (10° Reference Method): Fly the arc and verbalize: “Station is at 090 relative, DME is 15.2—good. Now turning 10° toward station to heading 350°. Watch the DME…14.8…turning back to 340°. DME is 15.1—good, back to 350°.” Let student observe the continuous adjustment cycle. Emphasize: “Small corrections, don’t chase the needle. If DME goes to 16, turn 20° toward the station. If it drops to 14, turn 20° away.”

8. Demonstrate Arc-to-Radial Transition: As the aircraft approaches the inbound radial (e.g., 180° radial inbound, course 360°), call out: “We’re at 175 radial, 5° from course. I’m rolling out to intercept. OBS is set to 360°. CDI is coming alive—one dot left—turning to 360° and bracketing.” Show smooth transition from arc to inbound tracking.

9. Demonstrate GPS Direct-To Function: In flight (or on ground during preflight), press the GPS Direct-To button. Enter waypoint identifier (e.g., KELP for El Paso). Show student the course line on map page. Activate the waypoint. Explain: “GPS now gives us a direct course of 125° magnetic to KELP. CDI shows our deviation from that course. If I fly heading 125°, we should track direct—assuming no wind. But watch: wind is pushing us right, so I’ll correct left to 120°. GPS automatically updates the ground track. I don’t rotate an OBS like VOR—the computer does it.”

10. Demonstrate GPS Flight Plan Entry and Activation: Load a flight plan from scratch: Departure point → Enroute waypoint → Destination. Show student each step: Enter waypoint, verify on map, add next waypoint, activate flight plan. Emphasize: “Always verify your waypoints on the map page. I once saw a student load ‘RIVRR’ instead of ‘RIVER’ and fly 40 miles off course. Don’t trust spelling—verify visually.”

11. Demonstrate GPS CDI Sensitivity Transition: As helicopter transitions from enroute to terminal area (typically 30 NM from destination), point out CDI scaling change: “Notice the annunciation changed from ENR to TERM. Full-scale deflection just dropped from 5 miles to 1 mile. Same needle movement now means I’m much farther off course. Stay alert—corrections need to be quicker and smaller.”

12. Demonstrate RAIM Prediction Check: Before flight, show student how to check RAIM on ForeFlight, Garmin Pilot, or via Flight Service: “Enter destination airport, ETA, and duration. System calculates satellite availability. If RAIM is unavailable, we cannot legally use GPS as primary navigation for that approach. We’d need to file alternate means—VOR or ADF—or choose a different destination.”

13. Demonstrate GPS Database Currency Check: On the ground, power up GPS and show database expiration date (usually on startup screen or in System Status page): “Today is October 15, and database expires October 19. We’re good. If database were expired, we could still use it enroute if we verify each waypoint manually—but we cannot use it for approaches. Easier to just update the database.”

14. Demonstrate GPS Failure Recognition and Transition: In flight, simulate GPS failure by pulling the GPS circuit breaker (if safe and briefed). Announce: “GPS failed—see the red X or ‘LOI’ message. I’m immediately switching to VOR navigation. I’m tuning ABC VOR on 115.3…identified…setting OBS to 180°…tracking inbound. I’ll advise ATC: ‘Approach, November 123, GPS failure, navigating via VOR, request vectors if needed.’”

15. Demonstrate Autopilot Engagement (if installed): If helicopter is equipped with autopilot, show engagement procedure: “I’ve verified GPS is tracking the correct course—direct to XYZ. Autopilot is in heading mode. I’ll press NAV to couple to GPS. Watch the autopilot track the course automatically. My job now is to monitor—verify altitude, airspeed, and that autopilot is tracking the correct magenta line. If anything looks wrong, I disengage immediately and hand-fly.”

16. Demonstrate Situational Awareness Verbalization: Throughout the flight, model aloud thinking: “We’re 12 miles west of ABC VOR, tracking direct to XYZ waypoint, 23 miles ahead. Altitude is 4,000 feet, airspeed 85 knots, on course. Next action: in 10 miles, I’ll start descent for the approach.” Encourage student to adopt this habit.

17. Demonstrate Distraction Management: During a navigation task, simulate a distraction (e.g., request frequency change from ATC). Show prioritization: “I’m in the middle of intercepting this radial—let me stabilize first. [Pause to center CDI.] Now I’ll switch frequencies.” Demonstrate that aircraft control comes before administrative tasks.

18. Demonstrate Chart Cross-Reference: While tracking a VOR radial, hold the enroute chart and point to current position: “We’re here—on the 270 radial of ABC, about 15 DME. Next waypoint is here, 20 miles ahead. I see a mountain range here at 6,500 feet, so I’m staying at 7,000 feet for obstacle clearance.” Show integration of navigation with chart reading.

19. Demonstrate Lost Comms Procedures During Navigation: Brief scenario: “If we lose comms while being vectored, we’ll continue last assigned heading and altitude for the time period specified, then proceed via last assigned route. If cleared direct XYZ and we lose comms, we continue direct XYZ. If on a DME arc and we lose comms, we continue the arc to the next fix or radial.” Have student verbalize the plan.

20. Debrief Performance Against ACS Standards: After flight, review specific performance: “On the first VOR intercept, you maintained altitude within 50 feet and heading within 3°—excellent. On the DME arc, you let the distance drift to 16.2 NM, which is outside the ±1 NM standard. Let’s discuss why that happened—you were distracted by the radio call and stopped scanning the DME. Next time, acknowledge ATC but keep your scan going.”

Student Actions

1. Pre-Flight Preparation: Student completes VOR check within 30 days if required (14 CFR 91.171), documents check in aircraft logbook or approved record. Student verifies GPS database is current (within 28-day AIRAC cycle) and checks RAIM prediction for planned route and ETA ±15 minutes. Student reviews NOTAMs for GPS outages or VOR station outages in planned area. Student prepares navigation log with frequencies, identifiers, courses, and distances.

2. Cockpit Familiarization: Student demonstrates ability to tune VOR receiver, adjust volume, identify Morse code, and cross-check identifier against chart or approach plate. Student demonstrates GPS power-up sequence, database currency check, and Direct-To function entry. Student verbalizes location of VOR/GPS controls, CDI, OBS, and DME readout.

3. VOR Tuning and Identification: Student tunes assigned VOR frequency using instructor’s cue (e.g., “Tune ABC VOR on 115.3”). Student listens to Morse code identifier and confirms verbally: “Identified Alpha Bravo Charlie.” Student cross-checks frequency and identifier on chart. Student practices tuning multiple VORs and identifying each correctly without prompting.

4. Determine Aircraft Position Using VOR: Student rotates OBS until CDI centers with FROM indication. Student states current radial: “We are on the 135 radial of ABC VOR.” Student verifies position on chart by drawing line from VOR along 135° radial and estimating distance using DME or pilotage. Student repeats exercise with different VORs until proficient.

5. Set Course to Intercept: Student is assigned a course to intercept (e.g., “Intercept the 360 radial of ABC VOR inbound”). Student rotates OBS to 360° (inbound course is shown as TO). Student determines current heading and calculates intercept angle using 30-45-90 rule. Student verbalizes plan: “We’re on 135 radial, need to intercept 360 radial inbound. That’s 45° difference, so I’ll use a 45° intercept—heading 315°.”

6. Execute VOR Intercept: Student turns to calculated intercept heading (e.g., 315°) and maintains heading ±5°. Student monitors CDI needle movement toward center. When CDI reaches one dot from center, student rolls out onto inbound course (360°). Student immediately assesses wind drift and brackets course: “Needle drifting right, turning left to 355°.” Student makes small corrections (5-10°) until finding heading that holds CDI centered.

7. Maintain VOR Tracking Tolerances: Student maintains airspeed ±10 knots (typically 80-90 knots in training helicopter), altitude ±100 feet, and CDI deflection no greater than ¾-scale. Student verbalizes any deviations: “Airspeed 78 knots, correcting back to 85.” Student demonstrates smooth control inputs—no overcontrolling. Student anticipates station passage and maintains last known heading through cone of confusion.

8. Intercept and Fly DME Arc: Student is assigned a DME arc (e.g., “Intercept and maintain the 15 DME arc from ABC VOR”). Student calculates lead point (0.5 NM before arc distance) and begins turn at 14.5 DME. Student rolls out with VOR station 90° off the nose (checks heading indicator and VOR bearing). Student applies 10° reference method: turns 10° toward station, flies until station bearing changes by 10°, then turns another 10° toward station. Student repeats cycle while monitoring DME: if inside arc (DME decreasing), turns toward station; if outside arc (DME increasing), turns away from station. Student maintains DME ±1.0 NM.

9. Transition from DME Arc to Radial: Student is assigned to intercept a radial from the arc (e.g., “Intercept the 180 radial inbound from the arc”). Student monitors radial indicator and leads the turn by 5-10° (e.g., begins turn at 175° radial). Student rolls out on inbound course (360° OBS setting) and centers CDI. Student applies bracketing to maintain course and confirms DME is decreasing toward station.

10. Use GPS Direct-To Function: Student is assigned a waypoint (e.g., “Proceed direct KHND”). Student presses Direct-To button on GPS, enters waypoint identifier using knobs or keypad, verifies waypoint on map page, and activates. Student notes direct course displayed (e.g., 125°). Student turns to intercept course at 30-45° angle, monitors CDI, and adjusts heading for wind correction. Student verbalizes: “GPS is showing 125° to KHND, I’m turning to 130° to intercept.”

11. Track GPS Course: Student maintains GPS course by keeping CDI centered (±¾-scale deflection). Student monitors map page for ground track and uses multi-function display (MFD) to monitor wind drift. Student makes heading corrections to maintain track: “Wind is pushing me right, correcting left to 120°.” Student maintains airspeed ±10 knots, altitude ±100 feet, and heading ±5°.

12. Load and Activate GPS Flight Plan: Student is assigned a flight plan (e.g., “Load flight plan: KELP direct RIVRR direct KDMA”). Student accesses flight plan page, enters each waypoint sequentially, verifies waypoints on map page, and activates flight plan. Student confirms active leg and direct course to first waypoint. Student demonstrates ability to modify flight plan: insert waypoint, delete waypoint, or activate a different leg.

13. Monitor GPS CDI Sensitivity: Student monitors annunciator as helicopter transitions from enroute to terminal area (within 30 NM of destination). Student verbalizes: “CDI scaling changed from ENR to TERM—full-scale deflection is now 1 NM instead of 5 NM. I need to tighten my tracking.” Student adjusts scan rate and correction magnitude accordingly.

14. Recognize GPS Failure: Instructor simulates GPS failure (e.g., pulls circuit breaker or covers GPS screen). Student recognizes failure immediately: “GPS is showing red X—I’ve lost navigation.” Student transitions to backup navigation system (VOR), tunes and identifies VOR, sets course, and continues navigation without delay. Student advises instructor (simulating ATC): “GPS failure, navigating via VOR, request vectors if needed.”

15. Perform RAIM Prediction Check: During preflight planning, student uses RAIM prediction tool (ForeFlight, Garmin Pilot, FSS, or online tool). Student enters destination airport, ETA, and flight duration. Student interprets result: “RAIM is available throughout the flight window” or “RAIM is unavailable from 1400Z to 1430Z—I need to plan VOR navigation during that period or delay departure.”

16. Check GPS Database Currency: Student powers up GPS and verifies database expiration date on startup screen or system status page. Student verbalizes: “Database expires on [date]—we are within the 28-day cycle, so we’re legal for IFR.” If database is expired, student states: “Database is expired—we cannot use GPS for approach operations. I’ll plan this flight using VOR or request alternate approach.”

17. Use Autopilot for Course Intercept (if installed): If helicopter is equipped with autopilot, student verifies GPS is tracking correct course, engages autopilot in heading mode, then selects NAV mode to couple to GPS. Student monitors autopilot performance, verifies altitude and airspeed, and cross-checks CDI. If autopilot behaves unexpectedly, student disengages immediately and hand-flies. Student verbalizes: “Autopilot is tracking GPS course—I’m monitoring altitude, airspeed, and lateral tracking.”

18. Maintain Situational Awareness Under High Workload: During complex navigation (e.g., DME arc with frequency change and descent), student verbalizes position and intentions: “I’m on the 15 DME arc, tracking to intercept the 180 radial. I’ll switch frequency after I stabilize on the arc.” Student demonstrates ability to prioritize: aircraft control first, navigation second, communication third.

19. Manage Distractions: Instructor introduces distractions (e.g., requests frequency change during course intercept). Student acknowledges but delays action until aircraft is stabilized: “Copy frequency change, I’ll switch in a moment.” Student completes navigation task, then changes frequency. Student avoids fixation on GPS or VOR during programming or tuning—maintains instrument scan.

20. Debrief Own Performance: After flight, student self-assesses performance: “On the VOR intercept, I maintained altitude and heading within standards, but I let the CDI drift to ¾-scale twice. I need to scan the CDI more frequently. On the DME arc, I was initially 1.5 NM outside the arc—I corrected by turning 20° toward the station. Next time, I’ll lead the turn earlier.” Student asks clarifying questions about any maneuvers that were unclear or difficult.

Completion Standards

The student demonstrates proficiency in intercepting and tracking navigational systems and DME arcs in accordance with FAA-S-ACS-14, Area of Operation V, Task A (IH.V.A). The student meets the following performance criteria:

Knowledge (IH.V.A.K1, K2):

• Explains principles of ground-based navigation (VOR/DME) including orientation, course determination, equipment limitations, test requirements per 14 CFR 91.171, and regulations governing use
• Describes VOR test methods (VOT ±4°, ground checkpoint ±4°, airborne checkpoint ±4°, dual VOR check ±4°, selected radial ±6°) and documentation requirements
• Explains DME operation, slant-range distance, and DME arc procedures including 10° reference method
• Describes satellite-based navigation (GPS/RNAV) including system components (space, control, user segments), RAIM requirements (minimum 5 satellites), WAAS functionality, and database currency (28-day AIRAC cycle per 14 CFR 91.511)
• Explains GPS interference sources (military testing, solar activity, terrain masking), NOTAM checking procedures, and limitations of GPS in IFR operations
• Describes GPS CDI scaling transitions (enroute ±5 NM, terminal ±1 NM, approach ±0.3 NM) and operational implications
• Identifies procedures for intercepting and tracking VOR radials and GPS courses using 30-45-90° intercept angle rule and bracketing technique

Risk Management (IH.V.A.R1, R2, R3):

• Demonstrates management of automated navigation systems by verifying waypoints, monitoring GPS mode transitions, cross-checking navigation sources, and maintaining mode awareness throughout flight
• Demonstrates ability to manage distractions and prioritize tasks using “Aviate, Navigate, Communicate” hierarchy—maintains aircraft control during navigation reprogramming, frequency changes, or clearance amendments
• Identifies strategies to prevent loss of situational awareness including position verbalization, chart cross-referencing, and requesting ATC vectors when task-saturated
• Recognizes symptoms of spatial disorientation and demonstrates trust in instruments over body sensations
• Articulates limitations of VOR (line-of-sight, cone of confusion, service volume), DME (slant-range error), and GPS (RAIM availability, database currency, interference potential, CDI scaling) and plans backup navigation accordingly
• Demonstrates autopilot management (if installed) by verifying correct course engagement, monitoring performance, and immediately disengaging if autopilot behavior is unexpected

Skills (IH.V.A.S1–S9):

• IH.V.A.S1: Tunes and identifies VOR navigation facility using correct frequency and positive Morse code identification. Verifies identifier against chart or approach plate. Programs GPS navigation system by entering waypoints correctly, verifying on map page, and activating flight plan. Verifies GPS database is current (within 28-day cycle) and RAIM is available for planned flight. System accuracy verified by cross-checking GPS against VOR or ATC radar position, and by completing VOR check within 30 days per 14 CFR 91.171.

• IH.V.A.S2: Determines aircraft position relative to navigational facility or waypoint by rotating VOR OBS until CDI centers with FROM indication (indicating current radial) or by reading GPS map page showing direct distance and bearing to waypoint. Verbalizes position accurately: “On the 135 radial, 12 DME from ABC VOR” or “8 miles northwest of XYZ waypoint.”

• IH.V.A.S3: Sets and orients to the course to be intercepted by rotating VOR OBS to desired inbound or outbound course (with proper TO/FROM indication) or by activating GPS Direct-To or flight plan leg showing desired course. Verifies course setting matches clearance or flight plan.

• IH.V.A.S4: Intercepts specified course at appropriate angle (30° for intercepts <20° off course, 45° for intercepts 20-70° off, 90° for intercepts >70° off). Maintains intercept heading ±5° until CDI approaches center, then turns smoothly to desired course. Intercepts are executed inbound to or outbound from navigational facility or waypoint as assigned.

• IH.V.A.S5: Maintains airspeed ±10 knots (e.g., 85 knots ±10 = 75-95 knots), altitude ±100 feet (e.g., 4,000 feet ±100 = 3,900-4,100 feet), and selected headings ±5° (e.g., 180° heading ±5° = 175-185°) throughout all navigation maneuvers. Corrections are made promptly when deviations are detected—does not allow deviations to accumulate.

• IH.V.A.S6: Applies proper wind correction to maintain course, allowing no more than ¾-scale deflection of CDI (VOR or GPS mode). If ¾-scale deflection occurs, immediately corrects with increased intercept angle to recenter needle. On DME arcs, maintains arc distance ±1.0 nautical mile (e.g., 15 DME arc maintained between 14.0 and 16.0 NM). Uses 10° reference method on DME arcs: turns 10° toward station, flies until station bearing changes by 10°, repeats. Corrects for distance deviations by turning toward station if inside arc or away from station if outside arc.

• IH.V.A.S7: Recognizes navigational system failure immediately—VOR flag appears, GPS displays “LOI” or “UNABLE RNP,” CDI freezes, or TO/FROM indicator becomes unreliable. When failure is detected, transitions to backup navigation system (second VOR, GPS if VOR failed, or requests ATC vectors). Reports failure to ATC using phraseology: “Approach, November 123, GPS failure, request vectors” or “Center, November 123, VOR receiver failure, navigating via GPS.” Does not attempt to troubleshoot navigation failure while in IMC at low altitude—transitions to backup first, troubleshoot when workload permits.

• IH.V.A.S8: Uses multi-function display (MFD) and graphical navigation displays (if installed) to monitor aircraft position relative to course, track wind drift angle, and maintain situational awareness. Student references moving map, checks cross-track error, and verifies ground track matches desired course ±5°. Uses MFD to anticipate upcoming waypoints, course changes, or terrain. Does not fixate on MFD—balances use of graphical displays with primary flight instruments and CDI.

• IH.V.A.S9: At evaluator’s discretion, uses autopilot (if installed) to make appropriate course intercepts by engaging heading mode, intercepting course, then engaging NAV mode to couple to GPS or VOR. Verifies autopilot is tracking correct course before and after engagement. Monitors autopilot performance continuously and disengages immediately if unexpected behavior occurs. Demonstrates ability to hand-fly all maneuvers if autopilot is not installed or not used.

Overall Completion Standard:

The lesson is complete when the student can consistently intercept and track VOR radials, GPS courses, and DME arcs within ACS tolerances (airspeed ±10 knots, altitude ±100 feet, heading ±5°, CDI ≤¾-scale, DME arc ±1 NM) while maintaining situational awareness, managing distractions, recognizing system limitations, and transitioning to backup navigation when required. The student demonstrates thorough knowledge of ground-based and satellite-based navigation systems, regulations (14 CFR 91.171, 91.511), and risk management strategies appropriate for single-pilot IFR helicopter operations. Performance meets or exceeds all elements of FAA-S-ACS-14 IH.V.A.