12.50.2. Describe the function and operation of an aircraft ELT.Section 2 Aeroplane Technical Knowledge Ancillary Systems 

12.46. TAWS Systems

12.46.2. Briefly describe the basic function and operation of TAWS (Terrain Awarenessand Warning System). 

12.42. GNSS Instruments

12.42.4. Describe the limitations and failure indications of a GNSS system.

– smaller GPS units can have reduced performance by the loss of signals when the view to the satellites is shielded by parts of the aircraft structure
– may have limited channels
– apparent error can be caused by trying to locate positions on a “non WGS 84 ” map

12.42.2. Describe the basic principles and operation of a GNSS (Global NavigationSatellite System). 

The owner and controlling authority of the GPS system is the US Department of Defence
– consists of a space segmnt of at least 24 solar powered satellites orbiting the earth at 20,200km altitude
– 4 satellites orbit in each of 6 circular orbital planes
– there are 3 satlellites as operational spares
– each of the 6 orbital planes is inclined at an angle of 55 degrees to the equator and each satellite takes approx 12 hours to complete an orbit
– the orbital planes are fixed in space – earth rotates at its normal rate within the constellation
– each satellite sends a signal wich contains a navigational message and a unique coded signal – repeats itself every millisecond

12.44. TCAS

12.44.2. Briefly describe the basic function and operation of TCAS.

12.40. Gyroscopic Instruments

12.40.16. Describe the indications of toppling.