Nav aids Flashcards
What’s an NDB’s use?
Show the direction of the NDB in the cockpit on the ADF needle.
What are the 5 classes of VDF and their accuracy?
- Class A +/- 2 degrees
- Class B +/- 5 degrees
- Class C +/- 10 degrees
- Class D > 10 degrees
- Digital resolution direction finding (DRDF) +/- 1 degree
What is GPS?
Global positioning system is a precision 3D area navigation aid. It obtains multiple fixes from orbiting satellites. Its accuracy is 100m for civil and 1-3m for military and is range is global. If GPS satellites are u/s NOTAMS are issued.
What are the 3 limitations of VOR?
- Provides no distance info
- Large site required
- Expensive to build and maintain
What does DME stand for?
Distance measuring equipment
What are the 7 limitations of NDBs?
- Static effect
- Night effect
- Station interference
- Coastal refraction
- Mountain effect
- Quadrantal error
- Absence of failure warning
What does VOR stand for?
VHF omni-directional range
What des NDB stand for?
Non-directional beacon
What does ILS stand for?
Instrument landing system
How does and NDB work?
A radio transmits in all directs and can be picked up by the a/c and shown by the ADF needle. Runs on MF and has a max range of 50nm in the UK (more power = more range).
What does a DME do?
Provides an accurate measure of distance from the a/c to the beacon by interrogating the transponder. Not usually stand alone often added to VORs, ILS or NDBs. They’re a secondary radar system as they can differentiate a/c.
What is a limitation of DME?
Inaccuracy caused by slant range.
What is the arrival segment of an instrument approach?
The a/c routes from the en-route phase to an initial approach fix.
What does a VOR do?
Shows the direction to or from the VOR.
What are the 5 ILS categories, their RVR and decision heights?
- CAT I 550m 200ft
- CAT II 250m 100ft
- CAT III a 200m Nil
- CAT III b 50m Nil
- CAT III c 0m Nil
What does VDF stand for?
VHF direction finding
What is height in reference to?
The height above a fixed point on land e.g. the runway.
What is altitude in reference to?
The altitude above mean sea level (MSL)
What are the 5 segments of an instrument approach?
- Arrival
- Initial
- Intermediate
- Final approach
- Missed approach
What is an FMS?
A fight management system takes information from nav aids, GPS, INS, engine data and route information to formulate routing and control autopilot. They vary is complexity from controlling heading to full autopilot.
What is an INS?
The Inertial navigation system provides self contained van abilities. It must have pre-programmed, accurate location data. The IRS can update itself using other Nav aids to increase accuracy. The accuracy decays by 0.6nm/hr. (GIGO)
What are the instrument approach fixes?
- Initial approach fix (IAF)
- Intermediate approach fix (IF)
- Final approach fix (FAF)
- Final approach point (FAP)
- Missed approach point (MAP)
How does VDF work?
Uses a ground based array of receiving aerials to measure the phase difference between radio signals received by the outer circular and single central aerials. Displays unit in the tower. Civil uses VHF, military uses UHF.
How does a VOR work?
VOR gorund station sends out an omni-directional master signal then sends out a highly directional second signal and measures the phase difference. They rotate clockwise 30 times per second and have accuracy of +/- 1 degree. Range is line of sight.