Navigation System and Radar Services
Cross Country Flight Planning
Navigation Systems and Radar Services
Objective: the student will be introduced to navigation systems such as VORs and GPS along with radar services.
Completion Standards: the student will be able to explain how a VOR works and what the cons are. The student will also be able to explain the basics of GPS.
References: AIM Ch 1, PHAK Ch 16
Equipment: White Board and markers, iPad/ computer
IP’s Actions:
Assess student
State the objective and completion standards
Writes down references
Provide attention getter
Present content
Assessment
Assign Homework
SP’s Actions:
Take notes
Ask Questions
Introduction:
(Attention Getter) : Have you gotten lost and yuse your phone’s GPS to find where you are?
Motivation: (this is what we will be talking about today…
Overview:
ground-based navigational system
VOR Classifications
Using the VOR
Tracking
Reverse sensing
Satellite-based navigation
GPS
RAIM
WAAS
LAAS
Content:
One ground-based navigational system (VOR/VORTAC, NDB, and DME).
VOR
The VOR by itself, providing magnetic bearing information to and from the station
VOR/DME
When Distance Measuring Equipment (DME) is also installed with the VOR.
VORTAC
When military tactical air navigation (TACAN) equipment is installed with the VOR. DME is always an integral part of a VORTAC.
VHF Omnidirectional range
VHF-radio-transmitting ground station
Projects straight line courses (radials) from the station in all directions.
Radials projected with reference to the magnetic north.
Radial
a line of magnetic bearing extending outward from the VOR station. Accuracy of course alignment with radials considered to be excellent (within ±1°).
Projection distance depends on power output of the transmitter.
VOR ground stations transmit within a VHF frequency band of 108.0-117.95 MHz.
Signal transmitted is subject to line-of-sight restrictions.
Range varies in direct proportion to altitude of receiving equipment.
VOR Classifications
Classified according to operational use—three classes with varying normal useful ranges.
T — terminal
L — low altitude
H — high altitude
ClassAltitudesRadius (Miles)T12,000’ and Below25LBelow 18,000’40HBelow 14,500’40H14,500 — 17,999’100H18,000’ — FL 450130HFL 450 — 60,000’100
VOR checks
Periodic checks and calibrations
Not required for VFR flight, but the best assurance of maintaining an accurate VOR receiver.
Verifies that the VOR radials the equipment receives are aligned with the radials the station transmits. Checkpoints are listed in the Chart Supplement.
FAA VOR test facility (VOT)
Certified airborne checkpoints
Certified ground checkpoints located on airport surfaces
Dual VOR check
IFR tolerances required are ±4° for ground checks and ±6° for airborne checks.
Using the VOR
The VOR is a radio receiver
Is tuned to the frequency of the VOR station to be used.
The station can be identified by a Morse code identifier, or a voice telling the name of the station.
If the VOR is out of service, the identifier is removed, and the absence of an identifier means that the station should not be used for navigation.
Can have an alarm flag to indicate when the signal strength is too weak (because the aircraft is too low, or two far away, or is out of the line-of-sight of the station) and should not be used for navigation.
Finally, even if a Morse code is detected it should be confirmed that the VOR is not broadcasting the Morse for "test", as this is sometimes also done. If in testing a VOR should not, obviously, be used for navigation.
Components
Ground transmitter
The ground station is at a specific known location on the surface, and it transmits on an assigned frequency.
Airborne receiver
The receiver in the aircraft can tune that frequency and has a means to display information from that signal.
Show picture
Tracking
Tune the VOR frequency and check the identifiers to verify you are receiving the desired VOR.
Rotate OBS to center CDI to a “TO” indication. If centered with a “FROM” indication, rotate another 180°.
Turn to the heading indicated on the VOR azimuth dial or course selector, to track directly to the station in a no wind situation.
If there is a crosswind, and the heading is maintained, the aircraft will drift off course. Alter the heading to return to the desired radial, and once the CDI is centered and the aircraft is back on the radial, crab into the wind to establish wind correction. Trial and error will establish the necessary heading to maintain the desired track.
Upon arriving and passing the VOR station, the “TO” indication will change to a “FROM” indication.
Reverse sensing
If flying toward a VOR with a “FROM” indication, the CDI will indicate opposite the direction it should. If the plane drifts right of course, the needle will move right. The same applies when flying from a station with a “TO” indication.
VOR Tips
One is to always identify the station positively by its code or voice ID.
When tracking to a station determine the inbound course and use it.
Don’t succumb to the temptation to just twist the OBS to re-center the VOR.
If done too much the aircraft will describe a spiral path to the station until the winds are directly in line with the course being flown, which is very sloppy flying.
When flying TO a station always use a TO indication, and the reverse when flying away, thus avoiding the possible confusion of reverse sensing.
Satellite-based navigation
Satellite-based navigation systems include:
GPS — Global Positioning System
RAIM — Receiver Autonomous Integrity Monitoring
WAAS — Wide Area Augmentation System
LAAS — Local Area Augmentation System
Global positioning system (GPS)
Over the last few decades GPS technology has started to pervade our live, including our flying. Satellite based navigation have a number of components which include the GPS satellite system itself, the Wide Area Augmentation System (WAAS), — Receiver Autonomous Integrity Monitoring(RAIM) and the Local Area Augmentation System (LASS).
The broader GPS system is composed of three major elements. The Space Segment, the Control Segment, and the User Segment.
Space Segment
This segment is currently composed of 31 satellites each approximately 12,000 nm above the earth.
The US is committed to maintain 24 operational satellites 95% of the time arranged
so that at any time 5 are in view to any receiver (with 4 being the minimum necessary for operation).
Each satellite orbits the earth in approximately 12 hours and are equipped with extremely stable atomic clocks each transmitting a unique code/nav message.
These satellites broadcast in the UHF frequency range which reduces the impact of weather on the signals.
These signals are line-of-sight, so a satellite must be above the horizon to be "visible" to the GPS receiver.
Control Segment
This segment consists of a master control station
five monitoring stations,
three ground antennas.
The monitoring stations and ground antennas are distributed around the globe to allow continual monitoring and communications with the satellites. Updates and corrections to the nav message broadcast are uplinked as the satellites pass over the ground antennas.
User Segment
This consists of all components associated with the GPS receiver. These can range from simple portable hand-held receivers to those permanently mounted in the aircraft. The receiver uses the signals from the satellites to calculate position, velocity, and precise timing to the user.
To solve for a location the GPS receiver uses the calculated distance and position information from the satellite from at least four satellites to yield a 3-D fix. This fix includes latitude, longitude, and altitude. VFR navigation with GPS can be a simple as selecting a destination and tracking the course (i.e. the Magenta Line). With GPS the course deviation is linear so that there is no increase in sensitivity when approaching a waypoint. It can be extremely tempting to rely exclusively on GPS, but never rely on one means of navigation.
RAIM
Receiver Autonomous Integrity Monitoring
Is the capability of a GPS receiver to perform integrity monitoring on itself by ensuring available satellite signals meet the integrity requirements for a given phase of flight.
Minimum of 5 satellites
FDE (Fault Detection Exclusion) requires 6 minimum
Excludes a failed satellite from the position solution
Without RAIM, the pilot has no assurance of the GPS position integrity. RAIM provides immediate feedback to the pilot
WAAS
to improve the accuracy, integrity, and availability of GPS signals. WAAS will allow GPS to be used, as the aviation navigation system, from takeoff through approach when it is complete.
installation of 3 GEO satellite, 2 operational control centers
Signals from the GPS satellite constellation are monitored by WAAS ground-based stations, to determine satellite clock and position corrections.
Two master stations, located on either coast, collect data from the reference stations and create a GPS correction message.
The correction message is prepared and uplinked to a geostationary satellite via a ground uplink station. This correction accounts for GPS satellite orbit and clock drift, plus signal delays caused by the atmosphere and ionosphere.
The corrected differential message is broadcast through 1 of 2 geostationary satellites, or satellites with a fixed position over the equator. The information is compatible with the basic GPS signal structure, which means any WAAS-enabled GPS receiver can read the signal.
The Wide Area Augmentation System (WAAS) and Local Area Augmentation System (LAAS) were deployed to achieve a higher degree of position precision for the GPS system. This improves the position calculation enough such that the GPS can be used for precision approaches. In the worst case WAAS precision is accurate to 25 feet 95% of the time. Like GPS the WAAS includes Space, Control, and User segments.
The LAAS is very similar to WAAS, but relies more on ground stations for signal correction and improvement. However, it is considered to be less cost effective than WAAS, but is also considered to be capable of handling Category III approaches.
Conclusion
ground-based navigational system
VOR Classifications
Using the VOR
Tracking
Reverse sensing
Satellite-based navigation
GPS
RAIM
WAAS
LAAS
(Questions to assess student)
How does a VOR work?
What is reverses sensing?
What are the altitudes and distances for a terminal VOR?
How many satellites are required for flight?
What is WAAS and how can it be useful?
HW:
Look over AIM ch1 about GPS and VORs.