WX RADAR Flashcards
Principle of operation of WX radar?
Sends out pulses in the form of a beam that gets wider with increasing range
Pulses travel at speed of light
Dist to target is the time for the pulse to travel out and being received. Bearing is the received bearing when the pulse is reflected back
What are good reflectors for a WX radar?
Raindrops are good
Snowflakes are not
How wide does the beam scan?
90 degrees either side
What’s the problem with looking at targets too far away?
They might appear as one as the beam width is wider with increasing distance
You might also be scanning the higher parts of a storm which are less refelctive
What kind of antennas give small beamwidth?
Large antennas
What erroneous readings can occur with a stabilized WX radar?
Ground returns can be present over 45 degrees combined pitch and roll
Aircrafts with normal gyros (not laser gyros) can have ground returns due to precession caused by acceleration or shallow banks below 7 degrees
What is the function of gain?
Is used to adjust the sensitivity of the Radars receiver
Is used to reduce the echos strength so they can be resolved on the display. You can then determine the relative intensity of 2 or more strong thunderstorms
What amount of rainfall does the different colors represent on WX radar display?
BLACK: Very light or no rain GREEN: 0,7 - 3 mm/h YELLOW: 3 - 12 mm/h RED: 12 mm/h or higher MAGENTA: Indicates turbulence
What does it mean if there’s a short distance between the colors on the display?
Steep rainfall gradients
The greater the gradient the worse the associated turbulence
What is radio shadows caused by?
Too many raindrops and the energy might scatter and be lost. Will show black space on the screen where there might be lots of rain
Ice on radome can cause this kind of problem
Where should a WX radar beam be pointed for max efficiency and why?
Should be pointed to the lower 18’000 ft
Above 18’000 ft you run the risk of having ice in the precipitaion which doesn’t reflect the pulses as well
If you get returns from a long distance how should you treat these storms?
As large severe ones
How do you set up the WX radar for T/O?
Scan for WX by tilting up to about 10 degrees at differnt ranges
Leave range for 40nm and +7 deg tilt up for conventioal gyros. This compensates for the acceleration error
Reduce tilt 1 deg per 10’000 ft until ground returns are shown in the outer parts of the screen
At 20’000ft set range to about 80 nm and tilt 10 deg down. Tilt up until ground returns are seen in the outer parts
What can be the problem with having too short range?
May display the protruding sides of a storm but not the inwards bulging middle part of the storm. It might look like you have a corridor in the middle when you actuall don’t
What kind of TS avoidance is advisable?
Above 20’000 ft use 20 nm
10’000 - 20’000 ft use 10 - 15 nm
Below 10’000 ft use 10 nm
In terminal areas at low alt use 3 nm
