Microwave Landing System - Ch 7

Question 1

Precision Instruments

Answer 1

Needs Azimuth (lateral), Elevation, Range

Question 2

Non - Precision

Answer 2

Azimuth and Range

Question 3

Issues with ILS

Answer 3

Multi-Path Propogation
Interference - Radio (fm)
False Localiser/Glide Path 
Only 40 channels 
No special Procedures for slow/light AoC 
Cannot be hilly - site specific 
Long straight in final approach

Question 4

MLS Advantages

Answer 4

200 channels
Not limited to straight in approaches 
Correct back course
Operate in hilly/not prepared sites 
No multipath interference 
Built in DME
Compatible with ILS, Area Nav, Autopilot

Question 5

Operation

Answer 5

MLS is Time Devision Multiplexing (TDM)

Information is time shared between angle and data functions and transmitter in combined packages

Question 6

TRSB

Answer 6

Time referenced scanning beams - scans area of coverage right/left up/down

Hits AC, starts timer, Stops timer, when beam comes back

Determines azimuth + vertically

Question 7

Coverage

Answer 7

40 degrees either side of extended CL

0.9 degrees low 20 degrees high out to 20nm

Question 8

Range Info

Answer 8

Derived from precision DME (v.accurate) - 22nm from transponder

Question 9

Frequency and Indentifying

Answer 9

S-Band: 5031-5091MHz at 300kHz spacing (4 letter morse code 6 times/sec)

Digital Frequency

Elevation signal Tx signal on same frequency TRSB

Question 10

Accuracy

Answer 10

95% lat and vertically accuracy within 20nm - 60ft above MLS datum point

Cat III accuracy: 20 ft azimuth and 2 ft elevation

Question 11

Display

Answer 11

Multi-Mode Receiver fitted (MMR)
DME/P Installed - curved approach possible
If not installed, ILS like approach