Stage 2 Lesson 11

What are the basic radio principles?

Radio waves are EM waves that travel long distances with limited loss. Antennas convert electrical energy to radio waves and receivers convert them back. Propagation depends on frequency, the environment, and equipment design.

What are radio waves and how do antennas interact with them?

What are Ground Wave?

They travel along Earths surface, constainted between Earth and ionsophere

What are Sky waves?

They are refracted by ionosphere and returned to Earth for long-distance comms (HF). Used for long-range aircraft communications (oceans) with low power (50–100 W). Not used for navigation

What are some P-static symptoms/warning signs:

• Loss of VHF comms

• Erroneous magnetic compass

• Autopilot causing “one wing low”

• High-pitched squeal

• “Motorboat” audio noise

• Loss of all avionics

• Inoperative VLF navigation

• Erratic instrument indications

• Weak transmissions / poor reception

• St. Elmo’s Fire on aircraft surfaces

What is Nondirectional Radio Beacon (NDB)?

Ground-based radio transmitter that transmits radio energy in all directions.

When an ADF is used with an NDB what can it determine? 

The bearing from the aircraft to the transmitting station. The ADF needle points to the NDB ground station to determine the relative bearing (RB) to the transmitting station.

What is magnetic bearing (MB)?

the direction to or from a radio transmitting station measured relative to magnetic north

What are the NDB components?

• Can transmit voice; often used for AWOS.

• Aircraft must be in range; coverage depends on station strength.

• Always identify station via Morse code before using ADF.

what is Automatic Direction Finder (ADF)?

Helps pilots determine the direction to or from an NDB.

• Function: Receives signals from NDBs and displays the relative bearing on the cockpit instrument.

• Output: Shows the direction to the station, allowing the pilot to navigate toward or away from it.

What are the ADF airborne equipment?

• Components: Receiver + indicator instrument

• Sense antenna: Non-directional; receives equally from all directions

• Loop antenna: Directional; receives best from two directions (bidirectional)

What are the Four different types of ADF Indicators?

• Fixed-card ADF – card stays fixed

• Rotatable-card ADF – card can rotate

• RMI (Radio Magnetic Indicator) – one or two needles

Explain the Fixed-card ADF

Also known as the relative bearing indicator (RBI), always indicates zero at the top of the instrument, with the needle indicating the relative bearing (RB) to the station.

Explain the movable-card ADF

Allows the pilot to rotate the aircraft’s present heading to the top of the instrument so that the head of the needle indicates MB to the station and the tail indicates MB from the station. 

Explain the RMI?

Differs from the movable-card ADF in that it automatically rotates the azimuth card (compass card), remotely controlled by a gyrocompass, to represent aircraft heading. 

• When a needle is being driven by the ADF, the head of the needle indicates the MB TO the station tuned on the ADF receiver.

• When a needle of the RMI is driven by a VOR receiver, the needle indicates where the aircraft is radially with respect to the VOR station. 

What can ADFs be used for?

To plot your position, track inbound and outbound, and intercept a bearing. 

What are the Operational errors of an ADF?

• Heading indicator not synced with compass → CFIT risk

• Wrong tuning or station ID → tracking wrong station

• Ignoring RMI malfunctions or warning flags

• Homing only → don’t track properly

• Poor orientation / skipping proper tracking steps

• Careless interception angles → errors in course

• Overshooting / undershooting MBs → forgot interception angles

• Not maintaining selected headings → misread needle changes

• Ignoring ADF limitations / factors affecting use

• Overcontrolling near station (“chasing needle”)

What is Range VOR? How does it work in relations to ground stations?

The primary navigational aid (NAVAID) used by civil aviation in the National Airspace System (NAS). 

• The VOR ground station is oriented to magnetic north and transmits azimuth information to the aircraft, providing 360 courses TO or FROM the VOR station. 

Explain what DME with VOR is

Referred to as VOR/DME and provides both azimuth and distance information

Explain what Military tactical air navigations is with VOR. 

Referred to as VORTAC and provides both azimuth and distance information

What is a radial?

Courses oriented FROM a station

What is the typical coverage of a VOR?

Typically at least 40 miles at normal minimum instrument flight rules (IFR) altitudes

What are the ground components of a VOR?

The ground equipment consists of a VOR ground station, which is a small, low building topped with a flat white disc, upon which are located the VOR antennas and a fiberglass cone-shaped tower

What are the airborne equipment included in VOR?

An antenna, a receiver, and the indicator instrument. 

How is an Omnibearing Selector (OBS) used?

The desired course is selected by turning the omnibearing selector (OBS) knob until the course is aligned with the course index mark or displayed in the course window.

Explain the Course Deviation Indicator (CDI) and how it is used?

composed of an instrument face and a needle hinged to move laterally across the instrument face. 

• The needle centers when the aircraft is on the selected radial or its reciprocal. 

What is the Zone of Confusion? 

Caused by lack of adequate signal directly above the station due to the radiation pattern of the station’s antenna, and because the resultant of the opposing reference and variable signals is small and constantly changing.

Also known as Cone of Confusion

What are some of the VOR Operational Errors

• Careless tuning / wrong station ID

• Not checking receiver accuracy/sensitivity

• Turning wrong way before position visualization

• Ignoring TO/FROM indicator → reverse sensing

• Not paralleling desired radial on intercept

• Overshoot / undershoot radials

• Overcontrolling near station

• Misinterpreting station passage (watch TO/FROM, CDI, OBS)

• Chasing CDI → homing, not tracking

How often does a VOR accuracy check need to be preformed?

Within 30 days prior to flight under IFR

part 91

What are some ways to perform a VOR accuracy check?

VOT: VOR Test Facility / radio repair signal

Certified checkpoints: on airport surface

Certified airborne checkpoints

What does Distance Measuring Equipment (DME) make possible?

DME makes it possible for pilots to determine an accurate geographic position of the aircraft, including the bearing and distance TO or FROM the station. 

How does DME work?

• Aircraft sends radio frequency pulses → received by ground station

• Ground station replies to aircraft signal

• Airborne DME measures elapsed time

• Converts time into distance (NM) to station

What are VOR/DME, VORTAC, ILS/DME, and LOC/DME all ment for?

Navigation facilities established by the FAA provide course and distance information from collocated components under a frequency pairing plan. 

What are some DME errors?

Line of sight, and slant range

What is the Slant Range DME error?

Refers to the distance from the aircraft’s antenna to the ground station. It is greatest when the aircraft is closer to the facility, at which time the DME receiver displays altitude (in NM) above the facility. 

What Equipment are included in area navigation (RNAV)?

VOR/DME, LORAN, GPS, and inertial navigation systems (INS). 

What can RNAV equipment do?

Capable of computing the aircraft position, VOR/DME RNAV actual track, groundspeed, and then presenting meaningful VOR RNAV is based on information generated by the present information to the pilot. 

What are the VOR/DME RNAV systems airborne controls?

• OFF/ON/Volume: select station frequency

• MODE:

  • VOR/DME: angular course ± standard VOR

  • RNAV: direct-to WP, ±5 NM linear deviation

  • RNAV/APPR: ±1.25 NM deviation

• WP Select: choose stored waypoint

• Data Input: enter WP number/ID, VOR/LOC freq, radial & distance

What is the advantage of RNAV compared to DME in relation to groundspeed?

DME groundspeed readout is accurate only when tracking directly to or from the station in VOR/DME mode, in RNAV mode the DME groundspeed readout is accurate on any track.

What are the different type of airways for RNAV?

Low IFR routes: Tango in aviation blue

• Flight levels below FL245 (24,500msl)

high IFR routes: Quebec 

• flight level between FL245 and FL600

What is the Global Navigation Satellite System (GNSS)?

A constellation of satellites providing a high-frequency signal that contains time and distance that is picked up by a receiver 

• Has at least 24 satellites in orbit

Depending on the amount of satellites that have our aircraft insight will depend on the type of positioning we will receive what are the amount of satellites and the types of positionings?

• 3 satellites for 2d position

• 4 for 3d: latitude longitude and altitude

• 5: RAIM with fault detection or 4 with one have an baro-aided (altimeter input) 

• 6: RAIM with fault detection and exclusion (5 with one having a baro-aided altimeter input)

What is RAIM?

Receiver Autonomous Integrity Monitoring, Acts like a built in watch dog that will make sure the satellites are accurate and correct. 

What is GPS?

Satellite-based radio navigation system that broadcasts a signal that is used by receivers to determine precise position anywhere in the world. 

• The receiver tracks multiple satellites and determines a measurement that is then used to determine the user location

What are the three components for GPS?

Space, control, and user

What are some GPS Errors?

Signal Loss (valleys or high terrain), GPS error sources (satellite clock errors, ionospheric and tropospheric delays), Satellite System status (health of the satellite), RAIM, Selective Availability

What is WAAS?

Wide Area Augmentation System, is designed to improve the accuracy, integrity, and availability of GPS signals. WAAS allows GPS to be used as the aviation navigation system from takeoff through Category I precision approaches. 

Explain how a WAAS works?

1. GPS Signals → WAAS Reference Stations

• GPS satellites send signals to Wide Area Reference Stations (WRS) on the ground.

• WRS detect errors in the raw GPS signals.

2. Reference Stations → WAAS Master Stations

• WRS forward the data to WAAS Master Stations.

• Master Stations analyze the errors.

3. Master Stations Create Corrected Signal

• Master Stations compute corrections for:

  • satellite position

  • clock errors

  • ionospheric delay

• They generate a corrected (augmented) message.

4. Corrections → Uplink → GEO Satellites → Aircraft

• Corrections are sent to a WAAS uplink station, which transmits them to:

  • Geostationary WAAS satellites (GEOs)

• The GEO satellites broadcast the corrected WAAS signal back down to aircraft receivers.

What is a LAAS?

Local Area Augmentation System, is a ground-based augmentation system that uses a GPS-reference facility located on or in the vicinity of the airport being serviced. Aircraft landing at LAAS-equipped airports are able to conduct approaches to Category I level and above for properly equipped aircraft. 

Local airport corrections

What is GBAS?

Ground-Based Augmentation System
It’s the modern system that replaced what was originally called LAAS. 

1. GPS signals come in
   Multiple GPS antennas on the airport receive GPS signals.

2. A ground station calculates the errors
   The GBAS base station knows its exact surveyed position, so it can detect GPS errors very precisely.

3. It creates a correction signal
   The system generates corrections to fix GPS errors for that specific airport environment.

4. Corrections are broadcast to aircraft via VHF
   Aircraft near the airport receive the corrected signal.

5. Aircraft compute a precise approach path (GLS)
   Pilots fly a GLS approach (GPS Landing System), which is equivalent to an ILS but more flexible.

What is ILS?

Instrument landing system, provides both course and altitude guidance to a specific runway. Used to execute a precision instrument approach procedure or precision approach.

What does an ILS Consist of?

1. A localizer providing horizontal (left/right) guidance along the extended centerline of the runway.

2. A glideslope (GS) providing vertical (up/down) guidance toward the runway touchdown point, usually at a 3° slope.

3. Marker beacons providing range information along the approach path.

4. Approach lights assisting in the transition from instrument to visual flight.

What are the different Categories for ILS approaches?

• Category I approaches provide for approach height above touchdown of not less than 200 feet.

• Category II approaches provide for approach to a height above touchdown of not less than 100 feet. 

• Category III approaches provide lower minimums for approaches without a decision height minimum. 

Where can you find Approach light Systems diagrams?

Aim 2-1-1 or TPP

The type at an airport will be shown on the approach plate

What are the airborne equipment for the ILS?

Receivers for the localizer, GS, marker beacons, ADF, DME, and the respective indicator instruments.

What are the ILS errors?

Refraction: the bending or distortion of the localizer or glideslope radio signal.

False Courses: unwanted additional glideslope signals created by the antenna’s geometry.

What are the types of Marker Beacons?

Outer Maker (OM): Usually indicates the FAF on a precision approach. Typically 4–7 NM from the runway

Color: Blue light

• Tone: Low-frequency “dashes” (–––)

Middle Marker (MM): Indicates you are at decision altitude/height (DA/DH). Middle Marker = Amber = “Make a decision.”

• Color: Amber light

• Tone: Dot–dash pattern (• – • –)

Inner Marker (IM): Used on CAT II / CAT III ILS, Very close to threshold Indicates you are at very low DA (100 ft or lower)

What is a Simplified Directional Facility (SDF)

The simplified directional facility (SDF) provides a final approach course similar to the ILS localizer. 

• A little wider and not as precision

What is Localizer Type Directional Aid (LDA)?

Similar accuracy and utility to a localizer,
but NOT part of a full ILS.

Course Width, 3° to 6°, Narrower/more precise than an SDF (Simplified Directional Facility).

Glide Slope: Some LDA approaches include a glideslope, making them fly like an ILS, but they remain LDA because they are not runway-aligned.

Runway Alignment: LDA is not aligned with the runway centerline.

• Straight-in minimums may be published if the course is ≤ 30° off runway heading.

  • If more than 30°, you get circling-only minimums.

What is MLS?

Microwave landing system (MLS) provides precision navigation guidance for exact alignment and descent of aircraft on approach to a runway. 

• It provides azimuth, elevation, and distance. 

What is RNP?

Required Navigation Performance,  is a navigation system that provides a specified level of accuracy defined by a lateral area of confined airspace in which an RNP-certified aircraft operates. 

What is a precision Approach?

an approach that provides both lateral and vertical guidance

such as ILS

What are non precision approaches?

Provide only the lateral guidance, pilots must determine appropriate rate of descent for the appropriate approach profile

Such as NDB, VOR, RNAV/LNAV, LDA (Localizer Directional Aid), LOC (Localizer only)

For RNAV to be considered RNP what requirements must be met?

1. RNP must include onboard performance monitoring and alerting capability (i.e. RAIM)

2. RNP must meet a specified accuracy at least 95% of the flight time

What are the 3 differnt types of RNP levels and what they can do?

RNP Value	Accuracy	Typical Use	Why
RNP 0.3	±0.3 NM	Approach	High precision near runway
RNP 1.0	±1.0 NM	Departure / Terminal	Terrain & traffic avoidance
RNP 2.0	±2.0 NM	En route	Wider space available

What is FMS?

A flight management system (FMS) is not a navigation system in itself. Rather, it is a system that automates the tasks of managing the onboard navigation systems. 

an interface between flight crews and flightdeck systems.

• can be thought of as a computer with a large database of airport and NAVAID locations and associated data, aircraft performance data, airways, intersections, DPs, and STARs. 

What can the FMS do for Pilots?

Define a desired route from the aircraft’s current position to any point in the world, perform flight plan computations, and display the total picture of the flight route to the crew.

• Radar sends a pulse of RF energy in a specific direction.

• The pulse bounces off a target and returns to the radar.

• The time it takes for the pulse to return is measured.

• What it tells you:

  • Distance to the target (range)

  • Direction / bearing to the target

• Display:

  • Shown on a radar screen so distance and bearing are instantly visible.

 Think: “Send pulse → bounce → measure time → know where it is.”

What are radar limitations?

• Not all aircraft are visible

• Radar waves can be blocked or bent

• Primary radar limitations

• Altitude info depends on equipment

What is the difference between DA and MDA

Decision Altitude (DA)

• Used for: Precision approaches (ILS, LPV, some RNAV (GPS) approaches with glidepath).

• The altitude at which you must decide immediately:

  • If runway environment is in sight → continue landing

  • If not in sight → initiate missed approach

• Key: You are descending on a continuous glidepath; decision is made as you reach the DA.

Minimum Descent Altitude (MDA)

• Used for: Non-precision approaches (VOR, NDB, LNAV, some RNAV (GPS) approaches without glidepath).

• Definition: The lowest altitude you can descend to before you must level off and wait until reaching the missed approach point (MAP).

• Decision:

  • If you see the runway at or before MAP → continue landing

  • If not → missed approach

• Key: You cannot descend below MDA until reaching minimum approach point (MAP); no glidepath is provided.

What are the three types of radio Waves?

Ground wave, Sky Wave, and Space Wave

What are ground Waves?

Travels along Earth’s surface; constrained between Earth and ionosphere. Good for short range

What are Sky waves?

 refracted by ionosphere and returned to Earth for long-distance comms. Good for longer rang distances

What are Space Waves?

Pass through ionosphere, uses line of sight

Where do you find the type of VOR services?

• On IFR chart next to VOR communication box, (VH or VL) and the second right after it indicates DME (D

• A/Fd

explain the VOR Frequency’s

• Frequency range: 108.0 – 117.95 MHz

• Channel spacing: Even tenths (108.0, 108.2, 108.4, …) for VOR

• Why even tenths?

  • Avoid conflict with ILS localizers, which use odd tenths (108.1, 108.3, …) in 108–112 MHz range

 Think: “VOR = even, ILS localizer = odd”

WHat are VOR operational Errors?

Reverse Sensing, Line of sight, and cone of confusion

Why are VORs still used?

• Backup navigation if GPS fails

• Traditional approaches (VOR, VOR/DME approaches)

• Airways and en route navigation in case of system outages

• They provide a reliable, independent ground-based navigation system.

What is an MON

Minimal Operational Network: A reduced network of VORs that ensures:

• You can always fly a safe VOR approach to land if GPS is unavailable.

• Coverage is maintained so no area is completely “dead” for navigation.

How do you Identify a MON VOR?

• Check the FAA VOR MON chart: shows which VORs are part of the MON network.

• Characteristics:

  • Often highlighted in the FAA VOR/Airway Supplement or on charts.

What are the ways to check the VOR in your aircraft?

“GAD V” → Ground, Airborne, Dual, VOT — the four ways to check a VOR.

explain the Airborne check:

• Tune and identify the VOR.

• Fly over or abeam the checkpoint radial.

• Check the CDI reading.

  • within 6 degrees form the indicated radial

How do you perform the Dual VOR cross-check?

• Tune both VORs.

• Compare the radials at a known location.

• Ensure they agree within tolerance.

  • with 4 degrees of each other

How do you perform a Ground check?

Performance on a checkpoint or VOT

• tune VOR to the test facility frequency.

• Align OBS to the specified radial.

• Ensure the CDI indicates properly.

  • within 4 degrees

What do yo need to record after you check the VOR equipment?

DEPS

date, Errors, Position (type of check or where it was done), Signature

How do you tell if DME is avialbe?

in the communcaiton bos (VOR bos) it will have a channel “Ch ##”

On A published DME arc what doe LR-### mean?

Lead radial for where you start your turn to inbound radial