Private pilot · ACS PA.VI.B · lesson pack

Navigation Systems and Radar Services

Why this one matters

Modern avionics make navigation easier, and they also make it easy to stop thinking. Pilots have flown into airspace, terrain and weather because they trusted a moving map they did not cross-check, or did not notice a lost signal. Knowing how each system works, what it can’t do and how to catch its failures keeps the box working for you.

1 · Know these cold

•Identify every VOR by its Morse code before using it. No ident, or a test signal, means don’t use it.(AIM, Chapter 1, Air Navigation (navigation aids and GPS))
•Set the course selector to the direction you’re flying; then the needle points toward the course and the TO/FROM flag flips at station passage.(PHAK (FAA-H-8083-25C), Navigation)
•GPS integrity: RAIM fault detection needs five satellites (or four plus baro-aiding); detecting and excluding a fault needs six (or five plus baro-aiding). A WAAS receiver gets integrity from WAAS instead while WAAS is available. If integrity is lost, cross-check with other navigation.(AIM, Chapter 1, Air Navigation (navigation aids and GPS))
•Basic radar service (flight following) gives safety alerts, traffic advisories, limited vectoring on request, and sequencing where established, all workload permitting. You are still responsible for seeing and avoiding traffic, terrain and weather.(AIM, Chapter 4, Air Traffic Control (radar services for VFR aircraft); 14 CFR 91.113)
•Squawk 1200 for VFR, 7700 for an emergency, 7600 for lost communications, 7500 for hijacking.(AIM, Chapter 4, Air Traffic Control (radar services for VFR aircraft))
•Altitude-reporting transponder (91.215) and ADS-B Out (91.225) are required in Class A, B and C; within 30 nm of a Class B primary airport from the surface to 10,000 MSL; above the ceiling and within the lateral limits of Class B or C up to 10,000 MSL; and in Class E at or above 10,000 MSL excluding at or below 2,500 AGL. ADS-B Out is also required in Class E over the Gulf of Mexico at or above 3,000 MSL within 12 nm of the coast.(14 CFR 91.215; 91.225)
•Data-link weather (FIS-B) is not real time: the age shown is when the mosaic was made, and the weather in it can be 15 to 20 minutes older. Use it for strategic planning, never to pick a way through thunderstorms.(AIM, Chapter 7, Safety of Flight (in-flight weather and FIS-B); NTSB Safety Alert SA-017)

2 · The lesson

VOR

A VOR transmits radials on 108.00-117.95 MHz. Reception is line of sight, so range grows with altitude.(AIM, Chapter 1, Air Navigation (navigation aids and GPS))
Tune and identify by Morse code. A missing ident, or a test signal, means the station is under maintenance and may be unreliable.(AIM, Chapter 1, Air Navigation (navigation aids and GPS))
The course deviation indicator shows where the course is relative to you, not your heading. Full-scale deflection is about 10° off the selected radial.(PHAK (FAA-H-8083-25C), Navigation)
Finding where you are: tune and identify, then turn the course selector until the needle centers. With a FROM flag, that's the radial you're on; with a TO flag, it's the course to the station. The needle doesn't point at the station, and TO/FROM depends on the selected course and your position, not where the nose points.(PHAK (FAA-H-8083-25C), Navigation)
Sensing is normal when your heading is roughly the same as the selected course, and reversed when your heading is roughly opposite it.(PHAK (FAA-H-8083-25C), Navigation; Instrument Flying Handbook (FAA-H-8083-15B))
Intercept and track: set the course with normal sensing, intercept at about 30-45° (steeper when far off, shallower when close), turn onto the course as the needle centers, then bracket a wind correction until the needle stays centered. Near the station the needle gets more sensitive: make smaller corrections and don't chase it. Hold altitude ±200 feet and heading ±15°.(PHAK (FAA-H-8083-25C), Navigation; Private Pilot ACS (FAA-S-ACS-6C), PA.VI.B.S3, S7)
Over the station, in the cone of confusion, the needle swings and the TO/FROM flag flickers or shows OFF. Hold your heading, don't chase the needle, and count station passage at the first steady TO-to-FROM flip.(PHAK (FAA-H-8083-25C), Navigation; AIM 1-1-3)
DME, usually paired with a VOR (a VORTAC), gives slant-range distance in nautical miles; it reaches its minimum (your height above the station) at station passage, so close in it reads more than the ground distance.(AIM 1-1-7)
For IFR, the VOR must have been checked within the last 30 days (VOT or ground checkpoint ±4°, airborne checkpoint ±6°, dual VORs within 4° of each other, or an airborne check over a prominent ground point on an airway radial, preferably more than 20 nm from the station, ±6°). Record the date, place, bearing error and your signature in the aircraft log or another record. It is a good habit for VFR too.(14 CFR 91.171(b), (d))

GPS and the database

GPS position comes from satellite ranging. RAIM checks the integrity of the solution: detecting a fault needs five satellites (or four with baro-aiding), excluding it needs six (or five with baro-aiding). A WAAS (SBAS) receiver doesn't rely on RAIM while WAAS is available; know which kind your airplane has.(AIM, Chapter 1, Air Navigation (navigation aids and GPS))
Know whether your unit is approved for the use you’re making of it, and check the database date. An expired database can have missing or moved airspace, frequencies and airports.(AIM, Chapter 1, Air Navigation (navigation aids and GPS))
GPS can be jammed or interfered with; NOTAMs announce GPS testing. Signs include integrity alerts, a jumping position or a sudden loss of navigation.(AIM, Chapter 1, Air Navigation (navigation aids and GPS))

Transponder, ADS-B and radar services

Mode A sends a code; Mode C adds pressure altitude; Mode S adds a unique address and data link. ADS-B Out broadcasts your GPS position, altitude and velocity.(AIM, Chapter 4, Air Traffic Control (radar services for VFR aircraft))
ADS-B In can show traffic (TIS-B) and weather (FIS-B). The traffic picture is incomplete: TIS-B depends on ground-station and radar coverage, and only aircraft that are transponder- or ADS-B-equipped and within coverage appear. So keep looking outside.(AIM, Chapter 4, Air Traffic Control (radar services for VFR aircraft))
For VFR flight following, call the approach or center frequency with the facility, your call sign and type, position, altitude, destination and the request: "Approach, Cessna 12345, VFR, 10 miles southwest of [airport] at 4,500, request flight following to [destination]." Traffic calls are given by clock position relative to your track, so correct for any wind correction angle.(AIM, Chapter 4, Air Traffic Control (radar services for VFR aircraft))
Answer a traffic call with "traffic in sight" or "looking". Radar service doesn’t relieve you of see-and-avoid, terrain clearance or weather avoidance.(AIM, Chapter 4, Air Traffic Control (radar services for VFR aircraft))

Automation and the EFB

Know what mode the autopilot and navigator are in and what they will do next. If you don’t understand what the automation is doing, reduce to a level you do, or hand-fly.(Risk Management Handbook (FAA-H-8083-2A))
An electronic flight bag is only as good as its battery, its data and your skill. Keep it charged and current, keep a backup, and watch for overheating in the sun.(AC 91-78, Use of Electronic Flight Bags)

When things go wrong

Programming a navigator can take your eyes inside for a long time. Plan and load the route on the ground, and keep inputs short in flight.(AC 90-48, Pilots' Role in Collision Avoidance)
On a lost signal or an integrity alert, fly the airplane, then switch to another source: the VOR, pilotage from the chart, or ATC.(PHAK (FAA-H-8083-25C), Navigation)

Want it all on one page, with scenarios? Read the full lesson.

On the flight

ACS standards

Intercept and track a given course, radial or bearing, and recognize station or waypoint passage.(Private Pilot ACS (FAA-S-ACS-6C), PA.VI.B.S3-S4)
Altitude ±200 feet and heading ±15°.(Private Pilot ACS (FAA-S-ACS-6C), Area VI)

What your instructor is watching for

Your instructor watches whether you identify the station, set up the navigator before you need it, cross-check the box against the chart, keep looking outside while using radar services, and handle a lost signal calmly.

3 · Say it out loud

Answer each one out loud, then check yourself and mark how it went.

Remember Recall it
“What transponder code do you squawk for VFR, and for an emergency?”
Understand Explain why
“Why do you have to identify a VOR before you use it?”
Apply Use it on a flight
“Your GPS shows an integrity alert halfway to your destination. What do you do?”

4 · Common mistakes

Flying with reverse sensing.
When your heading is roughly opposite the selected course, the needle sends you the wrong way.
Instead: Set the course you’re actually flying so your heading and the selected course agree, and check the TO/FROM flag.
Treating flight following as a traffic guarantee.
Controllers call traffic when workload permits, and not every airplane shows on radar.
Instead: Keep scanning outside, and use the calls as extra help.
Heads-down programming.
Long navigator inputs in flight cause altitude and heading errors and missed traffic.
Instead: Load the route before takeoff; in flight, short inputs and look outside between them.

5 · Quick check

Answer, then reveal. Flag anything you want to see again.

1. What is the VOR frequency band?
2. How many satellites does RAIM need to detect an integrity problem?
3. What does flight following provide, and what does it not change?
4. Where is an altitude-reporting transponder required?
5. How old can FIS-B weather be?
Scenario6. Your VOR needle swings full scale and the ident disappears. What do you do?

Trained it? Now prove it: practice navigation systems and radar services out loud with our examiner.

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Connect it

One situation that runs across this lesson and its neighbors in the same ACS area. Decide first, then check.

Connect it · Navigation

Halfway through a cross-country, the clouds ahead are lowering and pushing you down. You turn toward an airport off to your right, and ten minutes later you can't match the ground to the chart.

How do the diversion and the lost procedure connect? Decide, then see the worked answer

Divert early, while you still have altitude and options, and to a suitable airport, not just the nearest: terrain and weather on the way, runway length and surface, and fuel to get there with your reserve. As you turn, note the time and your heading, estimate the new heading, time and fuel, then refine. Hold an altitude that keeps you clear of terrain and meets the 91.155 cloud clearances. That note at the turn is what the lost procedure starts from: dead-reckon from the turn point, and the elapsed time multiplied by your groundspeed bounds how far you can be from it, your circle of uncertainty. Then the five Cs, in order. Climb, if the clouds allow, for a better view and radio reception. Communicate: ATC for radar assistance, flight following or vectors; Flight Service for communications and direction-finding help (Flight Service doesn't provide flight following). Confess that you're unsure of your position. Comply with the help you get, but keep the controller advised that you're VFR and not instrument rated: radar assistance doesn't authorize you to break the regulations or the VFR cloud clearances, so declare an emergency rather than accept a vector into cloud. Conserve fuel with an endurance power setting. Cross-check with a VOR cross-fix or GPS. Declare an emergency early, on 121.5 or by squawking 7700, if you can't stay VFR or the help isn't resolving it.

PHAK (FAA-H-8083-25C), Navigation; AIM 6-2; 14 CFR 91.155

Brings together: Pilotage and Dead Reckoning · Navigation Systems and Radar Services · Diversion · Lost Procedures

Teaching this? The instructor lesson plan →

Study aid, not FAA guidance. Sources: Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C); Aeronautical Information Manual (AIM); 14 CFR Part 91; AC 90-48; Private Pilot ACS (FAA-S-ACS-6C); VFR sectional chart and Chart Supplement. Checked against current sources 2026-11-12.