Airborn Weather Radar Flashcards
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What are the two different types of weather radars in the nose of the plane?
Flat (longer range, higher resolution)
Parabolic (curved, shorter range, lower resolution ((cant always identify two weather systems as being separate)
What is a potential problem with weather radars?
Attenuation. This is when the signal from the radar doesn’t make it all the way through a weather cell that has intense rain and so reports that all is clear on the other side when it might not be
How are turbulence and rainfall related on a weather radar display?
Turbulence is proportional to the rate of rainfall. So if the rainfall gradient is steep, the turbulence will be worse.
How many feet per second is destructive turbelence?
50 fps
Weather radar can see water best. What will it pick up from most to least ease?
- Rain (the size of the drop is what matters most) and wet snow gets a strong echo
- Wet hail appears to be a giant raindrop and so has the highest reflectivity
- Dry snow is a poor reflector
- Water vapour, clouds, fog, ice crystals, and small dry hail will not produce an echo at all
More info on Attenuation:
What does hail look like on radar?
- Fingers or protrusions
- Hooks (often indicates tornado activity)
- Scalloped edges on the cloud outline
Hail activity appears on the radar quite suddenly along any edge of the storm outline. They also can change in shape and intensity in a matter or seconds. Remember hail is associated with very strong thunderstorms.
Note that weak or fuzzy projections are not normally associated with hail but should be watched closely
Generally how high and wide is a radar beam?
8° high and sweeps 45° either side of your 12 o’clock
The beam is also stabilized, which means it should stay at the same angle in relation to the earth, no matter what angle the AC is at. Unfortunately stabilizing systems have many errors so the angles printed on the tilt controller are not always accurate
What is the rule of thumb for converting degrees to feet at a particular distance?
Distance x 100 = Feet per degree
(At 10NM, 1° is 1000feet)
What is the standard for setting the TIP angle on the radar beam?
If the beam is 8° and the zero position is accurate, just tilt to 4°
(This is literally the only explanation that gave, there was no context or explanation about what any of the above actually is. What is the zero position? Dunno, they didn’t say. If the beam is 8° relative to what? A mystery They followed this up by saying most radar tilts are not calibrated accurately, so the above rule is useless.)
Because aviation is ridiculous, radar tilts are not often calibrated correctly, so the rule of thumb of tilting it to 4° probably wont work. What’s the other way to do it that is, supposedly, more accurate?
Aim it at the ground then tilt up by half your altitude (example if you’re at 30,000ft, tilt up by 15°
General rules of thumb for storm avoidance:
What are the three types of weather detection systems?
- Lightning Detection (oldest, simplest one)
- Airborn weather radar (most complex)
- DataLink (subscription based)
Info on Lightning Detection system:
- Sometimes called Spheric Devices
- Can detect lightning all around in a 360° view and up to 200NM away
- Becoming less common and being replaced by DataLink systems
What are the advantages and disadvantages of Lightning Detection Systems
Pros:
* Less expensive ($7K vs $30K for a radar)
* Simple to maintain (no moving parts)
* 360° detection
* Can detect cells and storms hidden behind other cells and storms
* Provides real-time (no lag, info coming back is instant) info about electrical discharges as well as pretty accurate data on the azimuth and distance of those charges
Cons:
* Does not give as much detail as radar
* Cannot detect rain, which is where the turbulence is often worst due to downdrafts
* Lightning can occure many miles (up to 20NM) from an active cell
