RADIO ALTIMETER

Question 1

Up to what height does a radio altimeter work?

Answer 1

Up to 2’500 ft

Question 2

To what systems are Radio altimeter info sent to?

Answer 2

1. GPWS
2. Auto-pilot and Auto-land
3. EFIS
4. FMC

Question 3

How does a Radio altimeter measure height?

Answer 3

It measures frequency change which is a measurement of the time taken for the radio wave to travel to and from the surface
The greater the frequency change the greater the distance

Question 4

What frequencies does a Radio altimeter use?

Answer 4

Uses SHF 4250 - 4350 MHz

Question 5

What is the accuracy of a Radio altimeter?

Answer 5

At 0 - 500ft it’s 3% or +- 3ft

Above 500ft it’s 5% of the height

Question 6

What errors are associated with a Radio altimeter?

Answer 6

1. Leakage error: TX and RX antennas are to close and interference can occur
2. Mushing: If antennas are too far apart and aircraft is close to the ground. The actual distance traveled by the
   wave can become greater than twice the vertical height between the surface and the a/c