What frequency range is the NBD and in what direction does it propagate?
- Transmits on the range of 200-400 kHz (Low to Medium Frequency)
- Propogates in all directions
How does the pilot use the ADF to position themselves in relation to the NBD?
1) The pilot tunes the appropriate NBD frequency using the ADF control panel.
2) Identifies the Morse code of the station
3) Pilot can use the compass bearing pointer to determine the position of the NBD relative to the aircraft.
What is the max range of an NBD?
- ## 30 NM to 400 NM but range of each NBD USA published in ERSA for each NBD.
What is the usable range for NBD?
40 to 120 NM
Is rated coverage of NBd reduced at night?
What are the errors associated with NBD?
M = mountain effect I = Interference N = Night Effect T = Thunderstorm Interference Q = Quadrangle error C = Coastal Effects
What does VOR stand for?
Very High Frequency Omni Directional Radio Range.
What are the two signals transmitted by the VOR?
1) Reference Phase signal (which is omnidirectional)
2) Variable phase signal (which rotates uniformly at a rate of 1800 RPM , with its phase varying at a constant rate throughout the 360)
What frequency band do VORs operate in?
112 MHz to 117.95 MHz
What are the rates coverages for VOR used for planning purposes?
Below 5,000 feet = 60 NM 5000 feet to 10,000 feet = 90 miles 10,000 to 15 000 feet = 120 miles 15,000 feet to below 20,000 feet = 150 miles 20,000 and above = 180 miles
Where can actual ranges be found?
What does one dot on the course deviation indicator equate to on the PC-21?
Half scale deflection or 5 degrees.
Is the VOR more accurate that the NDB?
What are the errors that affect VOR?
A = airborne equipment error V = Vertical Polarisation error G = ground station error A = aggregate error S = site effect error
What does Distance Measuring Equipment (DME) measure?
Slant distance to a ground station
What frequency range does the DME operate in?
962 MHz to 1213 MHz
How does the the DME equipment work?
Secondary radar principle
- Aircraft DME equipment transmits an interrogation signal which includes a pair of radio pulses in all directions.
- A ground based transponder receives the signal , amplifies it and after a 50 second microsecond delay, re transmits it.
- airborne equipment then calculates distance based on time to receive response pulse
What is the DME often colocated with?
VOR or ILS
What is the general rule of thumb regarding accuracy of the DME?
Accurate outside a distance from the station Walton the aircrafts altitude in thousands of feet.
- if aircraft is at 6000 feet, aircraft can be considered accurate outside 6 NM
What is formula for max range of DME?
D = 1.25 x sqrt( H1) + 1.25 sqrt ( H2)
What is the main limitation of the DME?
Line of sight (LOS)
What does TACAN stand for and what is it?
Tactical Air Navigation
- it’s a military version of the VOR/DME
What is the frequency range of the TACAN?
962 to 1213 MHz.
Is TACAn info more accurate than VOR?
Which stations use the X and Y beacons?
X beacons are used by ground stations, Y beacons are used by aircraft.
What is the accuracy of the TAcAn?
Distance accurate to +- 0.1 NM and +- 0.5 degrees
What is the rates coverage ?
Same as VOR and DME
What is the cone of confusion?
The area directly above the TACAN where is becomes unreliable.
- Usually about 70 degrees across
What are the two main TACAN errors?
1) Forty degree lock off error
2) co channel interference
What is the ILS system?
Provides aircraft with both glide and tracking guidance for a precision approach to a specified runway.
What are the two sub systems that the ILS consists of?
What does the localiser provide the pilot?
Provides lateral steering indications to assist the pilot to align the aircraft to the centreline of the runway
What does the glideslope provide the pilot
Provides vertical steering indications to assist the pilot in maintaining correct runway descent path.
How can the correct ILS frequency be identified?
By its Morse IDENT
What are the ILS frequencies?
Localiser :108 MHz to 112 MHz
Glideslope: 329 to 335 MHz
Marker Beacon 75 MHz
How does the localiser work?
Sends out a 90 Hz signal love and a 150 Hz signal lobe.
- when Frequency from the two loves is the same, the A/C is on path for runway centreline.
How does glideslope work?
Similar to localiser but in the Vertical direction.
When 90 HZ and 150 Hz lines are equal , the aircraft is on centreline.
What do the markers provide the pilots
Distance to the runway.
What does the outer and middle marker distance signify?
Located approx 4 NM from the airfield
Middle marker is 5000 feet from the airfield.
What are the different categories of ILS approaches?
Decision height not lower than 200 feet
Runway visual range not less than 550m
What is the ILS accuracy?
- At 2000 ft AGL = 25 NM
- Below 5,000 ft = 30 NM
- 5000 and above = 50 NM
What are some errors associated with the ILS errors?
1) False glideslope which is formed at 12.5 degrees from the horizontal
2) reflected signals such as scalloping and beam bend.
3) FM transmission interference
How does the inertial reference system (IRS) work?
It is an application of Newton’s first law
- Uses accelerometers and gyros to sense the movement of the A/C to determine position, ground speed , attitude and flight path vector information.
How does the IRS determine position from the beginning of the flight?
- Starts with known latitude and longitude.
- Uses gyros and accelerometers to determine position after that.
What is the error associated with IRS over time? What must be done to correct this?
- Must be regularly updated by either GPS or use of a ground based aid.
What does the IRS do once he position has been corrected?
The IRS determines its drift error and will apply that correction to further complications.
What are the two alignment options for the IRS?
1) Fast Alignment
2) Complete Alignment
What is the fast alignment for an IRS system?
- This takes 30 seconds and resets the IRS to calculate ground speed to zero.
- Any drift corrections registered from a previous flight are kept and applied.
What is a complete alignment?
- Can take from 5-20 mins
- Drift corrections are cleared and the IRS recalculated it’s heading, altitude and position using data from external sources
What is a strapdown IRS?
Comprises a CPU, optics and solid state technology.
What type of gyroscope is used in a strap down IRS?
Laser ring gyro (LRG)
How many accelerometers and gyros are used in a strap down IRS?
Three accelerometers and three gyros.
What types of errors do IRS systems experience? Gimballed systems versus strap down IRS systems?
- Gimballed systems suffer from gimbal lock and mechanical defects.
- Strapdown IRS suffer from advanced electronics errors.
What is IRS drift?
IRS are subject to inaccuracies in sensor information which lead to inaccurate position computations.
What are the three basic portions of the GPS system?
1) Space Portion: Satellites that orbit the Earth
2) Control Portion: Ground stations
3) Receiver Portion: Receiver inside the aircraft that identifies each satellite.
What are the two levels of service for GPS?
1) Link 1(L1) - Non Précision GPS accurate to 8 m
2) Link 2 (L2) - Accurate GPS , accurate to 4 m
What are some GPS errors?
GPS interference caused by :
- Ionosphere effect
- External Interference
- Multipath effects
What are considered the navigation brains for an aircraft?
The mission computer and the FMS
What sensors does the MC use to calculate position?
1) Hybrid = mixed IRS and GPS
2) GPS only
3) IRS only
Is the PC-21 used for civilian IFR operations?
What does the FMS use to calculate the FMS position?
Hybrid GPS/IRS position.
What is the estimated position uncertainty (EPU)?
Represents the radius of a circle around the FMS computer position in which the aircraft lies 95% of the time.
What is the EPU compared against ?
The Required Navigation Performance (RNP)
- Should it exceed these values the aircraft is unable to meet the particular RNP requirements
What should be done if the GPS fails or is deselected ?
FMS position will be calculated using IRS or ground based navigation aids.
What must IFR aircraft navigate with to meet Australian Performance Based Navigation requirements?
IFR aircraft GPS.