Non-Directional Beacons (NDB) - Ch 3 Flashcards
NDB
A ground based station
Omnidirectional
Transmits to ADF (in AC)
2 Types: - Locator - Enroute
NBD Frequency
190kHz - 1750kHz
NBD Class
B: +/- 5 degrees
ADF Made up of
- Loop antenna - which has two null points
- Sense Antenna - Added to take away null position - carotid pattern which deletes the wrong one
- ADF receiver (onboard the AC)
- Indicator
Buttons:
Inner/Outer Knob - Used to tune the STDBY
Double Arrow Button - Swaps use freq. - standby freq.
ADF - Selects the equipment
BFO - Unmute button
Test Button - Knocks beacon over to 90 degrees
Cone of Confusion/Silence
Directly overhead NBD signal
It becomes disturbed or even totally disappears
Diameter of Cone of Silence
(Height above NDB)(tan40)(2) / (6080ft/nm)
A1A Beacons
BFO / Tune button must be selected on to listen to it
Fixed Card ADF
Radio Compass - Indicates relative bearing
Moving Card ADF
Indicates Magnetic bearing (QDM/QDR)
Radio Magnetic Indicator (RMI)
RMI
Electronic Nav
Display symbols
EFIS ND
Relative Bearing =
= Magnetic Bearing - Magnetic Heading
= QMD - Mag. HDG
If moving card breaks
It effectively becomes a fixed card
HDG becomes 000
RMI
AFD - Double Ended - single head:QDR - Double Head:QDM (large)
Easier to use
Class B: +/- 5 degrees
Left Wind =
Right drift : compass will decrease
Right Wind =
= Left Drift : Compass will increase
NBD Limited by Power
Varies with square root of power
To double the range you must increase the power by 4, to triple the range you must increase the power by 9
NBD consists of
Surface waves and sky waves
Limitations for NDBs
Lack of failure flags
Errors
Static Interference Night Effect Coastal Refraction Multipath Propogation Quadrantal Error Bank Angle Error
Static Interference
TS - Can render the ADF completely unreliable
Night Effect
Due to changes in air density
Worst at sunset and sunrise
Coastal Refraction
Waves travel slower over land and faster over the sea
When on coast, no refraction
When abeam, (90) no refraction
Multipath Propagation (Mountain Effect)
Waves reflect / bounce off terrain
Leading to multiple paths
Bank Angle Error
Design of the loop error
Referred to as Dip
Needle points into the turn
Quadrantal Error
AC structure bends the incoming wave
Max: 45 degrees
Min: 90 degrees
