AS 07 - Radar Theory 2 & Weather Avoidance Flashcards
Review Questions
Name the basic radar components
A - Antenna P - Power Supply R - Receiver I - Indicator S - Synchronizer M - Modulator T - Transmitter
What are some radar reception factors?
Think target, pulse and radar
Target range, size, shape, reflectivity characteristics
Pulse shape, width and repetition frequency (PRF)
Radar power output and receiver sensitivity
Why do smooth seas appear black on the scope?
Very little energy returns to the radar, most is lost due to reflection
As seas become rougher, waves produce small reflecting surfaces that return _____ radar energy to the receiver and the scope becomes brighter. How does this effect small targets on the radar?
More
Small targets may be hard to identify.
To overcome sea return interference, an operator can:
Reduce_____
Reduce _____
_____ antenna tilt
Select _____ mode
Reduce gain
Reduce altitude
Raise antenna tilt
Select sea mode
Surface vessels resemble what land mass?
Islands
Metal or concrete boats will provide what when compared to wooden boats?
Stronger radar returns
If rivers are wide, they show up dark. The far shore of a river or lake will appear much _______ than the far shore.
Brighter
A narrow river may be identified solely by what on radar?
A bright return from the far bank
WRT aspect, a river will give more returns if you are __________ to river
Perpendicular
Mountains block off the radar echoes and cause what?
A mountain shadow
True or false
As the aircraft passes over a mountain, the near edge of a mountain appears brighter than the far edge.
True
If no returns are shown from behind the bright mountain, its possible the aircraft may be _____ the peak.
Below
If returns do show up behind the bright mountain return, the AC may be above the peak or what?
There may be another mountain peak beyond the first
What topo/ geographical features may be mistaken for rivers on a radar?
Valleys or canyons
Do urban areas provide good or bad radar returns, why?
Good radar returns because buildings are very good reflectors due to shape and materials.
The layout of urban areas creates what kind of effect?
A cardinal effect, towns often lined up N-S / E-W
What are the Variable Limiting Factors?
Target size and shape Target composition (reflectivity)
Order the following from strongest to weakest return:
Wood, concrete, water, metal, earth, rock and ice
- Metal
- Concrete
- Rock
- Wood
- Earth
- Water
- Ice
What are the Constant Limiting Factors?
Radar Power PRF Spot Size (the resolution of your display) Pulse Width (range resolution) Beam Width (azimuth resolution) Combined Errors
On the Hercules and Cyclone, the ACSO is primarily responsible for operating what? As well, the ACSO is responsible for _______ avoidance when operating IFR conditions or at night.
The radar & weather avoidance
What does the Weather Radar System present and display?
It presents an accurate and continuous picture of the weather ahead of the AC
It displays range and azimuth, enabling the operator to give heading changes to avoid severe weather.
The radar “sees” water droplets. What affects the strength of radar return regarding water droplets?
The intensity of the return depends on the size of droplets and their concentration.
The close relationship between turbulence and rain gradient explains what exactly?
The greater the change (increase) in water content, the more severe the turbulence.
True or false
The primary aim is to avoid areas of heavy rain.
False, The primary aim is to avoid areas of heavy turbulence, hail rather and areas of heavy rain
Which stage of a thunderstorm has the greatest turbulence?
Mature stage, this is when up and down drafts occur with rapid changes in direction and velocity
How are up and down drafts depicted on the radar?
A sharp edged echo due to high rain gradient
What level of relfectivity does snow have?
Light, even moderate - heavy snowfall can appear light in intesnsity
Hail and ice pellets can appear as which type of precipitation?
Heavy precipitation
Which side of the thunderstorm anvil is the most dangerous? Why?
The downwind side (under the anvil) because hail may be encountered several miles from the strongest radar returns while underneath.
Which factors make hail difficult to detect?
The shape, density and intensity may give varying levels of returns
Radar returns that resemble pointed fingers or hook indicate what?
(review this question, I think TS is an answer)
The potential for hail, and in some cases, tornadoes
A rapidly developing storm is indicated on a radar by?
Scalloped lines or rapidly changes edges. Avoid at greater distances
True or false
Whenever possible you should maintain your track to fly through the heaviest radar returns.
False, avoid these areas by altering course to fly between or around.
What are the weather avoidance distances for the different levels?
5 NM when flying below freezing level
10 NM when flying above freezing level
20 NM when flying above 30 000’
What are the weather options for the AN/APS 504 (V) 3?
Weather (WX) and Weather Contour (CTR)
Briefly describe WX and CTR modes.
WX mode provides signal processing to show areas of strongest returns within a cell.
CTR mode suppresses areas of high precipitation in the display to give a brightly outlined weather display. The strongest parts of the storm cloud appear as black holes in the cloud returns.
For the best results with Weather Mode, how should antenna tilt be adjusted?
Adjusted to a point just above the ground clutter returns to avoid confusing ground and weather returns.
Review Questions
Why are urban areas good radar targets?
Buildings are very good reflectors due to their shape.
Towns often lined up N-S / E-W creating a cardinal effect.
Review Questions
Why doesn’t hail show on the radar?
It is made out of ice which is a poor reflector unless coated in liquid water.
Review Questions
What are the distance rules for avoiding storm clouds?
5 NM below freezing level
10 NM above freezing level
20 NM above 30 000’
