Lecture 6 RADAR Part II

Introduction Recall Back RADAR Part 1 What are the three types of RADAR? What are the differences between PSR and SSR? How PSR works? How SSR works?

why ‘Stealth’ aircraft can be invisible ?? An F-117 Nighthawk stealth strike aircraft B-2 Spirit stealth bomber of the U.S Air Force

Most conventional aircraft have a rounded shape Most conventional aircraft have a rounded shape. This shape creates a very efficient radar reflector. Means that no matter where the radar signal hits the plane, some of the signal gets reflected back

An F-117 Nighthawk stealth strike aircraft B-2 Spirit stealth bomber of the U.S Air Force However, some military aircraft are designed and constructed to be non-reflective - the so-called “stealth aircraft”.

A stealth aircraft is made up of completely flat surfaces and very sharp edges. When a radar signal hits a stealth plane, the signal reflects away at an angle. Surfaces on a stealth aircraft also can absorb radar energy as well. So, this aircraft become invisible. A stealth aircraft is made up of completely flat surfaces and very sharp edges. When a radar signal hits a stealth plane, the signal reflects away at an angle, like this:

2. Airborne Weather RADAR (AWR)

Introduction Airborne Weather Radar (AWR) is used to provide the pilots about weather ahead. The installation include weather radar antenna located in the nose of the aircraft and weather radar display inside the cockpit. The radar information can be displayed in combination with the aircraft route on the EFIS Navigation Display (ND) Weather radar is used for severe weather avoidance Bands: 5350-5470 MHz, 8750-8850 MHz, 9.3-9.5 GHz, 13.25-13.4 GHz

The antenna is housed in a radar made of composite materials located in the nose of the aircraft.

How Airborne Weather Radar Works An antenna which sweeps side to side transmits Super High Frequency (SHF) signals which is 9Ghz When hit the reflective objects (precipitation), the signals is reflected back to the antenna receiver. The returns (echo) are displayed to the pilot on the aircrafts radar screen.

Precipitation Weather radar is function to detect, locate, and measure the amount of precipitation. Precipitation is within or falling from cloud. It includes rain, snow, ice & hail. Different precipitation has different refractive and reflective levels. A weather radar is used to To locate precipitation To calculate its motion, To estimate its type (rain, snow or hail) To forecast its future position and int

Airborne Weather Radar Works The goal of weather radar is to display areas of heavy precipitation, which generally indicates areas of turbulence. Different types of precipitation have different reflective qualities. Reflectivity of precipitation is directly related to MOISTURE content. Large water droplets show the strongest returns, while dry hail or snow will show light returns, or no returns at all. Weather radar detects raindrops, not clouds or fog.

Airborne Weather Radar Works The precipitation painted (depicted) by airborne weather radar is not of primary concern, however it is representative of areas of severe weather. Areas of large raindrop size=high rainfall rate=intense storm=turbulence. The turbulence associated with convective clouds is often severe and always dangerous. Other dangerous factors associated with thunderstorms are: severe icing, hail, lightning, strong downdrafts.

Airborne Weather Radar Display Older weather radar displays depict weather in a monochromatic form. Areas of stronger returns will be brighter than weaker returns. Modern radar displays are full color: Level 1: light precipitation-green Level 2: moderate precipitation- yellow Level 3: heavy precipitation- red Level 4: very heavy precipitation- magenta Level 5-6: intense/extreme precipitation- may be an area of no returns (black) Attenuation can cause shadowing to occur, displaying an area of no returns where heavy precipitation exists. An area of intense activity may cause complete attenuation resulting in no signal penetration. Modern systems have alerts which will be displayed in areas of possible shadowing. The display will incorporate range and bearing information to aid the pilot in weather avoidance. EFIS allows the weather information to be displayed on the pilots HSI.

Weather radar is painting a cell at 40NM Weather radar is painting a cell at 40NM. But we have no idea what portion of the cell we are painting (upper, mid, lower) 3° beam width at 40NM is 12000 feet. Adjust tilt down until we paint continuous ground returns at 40NM. Now we have established a ground base. We know that 1° at 40NM is 4000 feet, so if we tilt up 1° we know the bottom of the beam is at 4000AGL and the top is at 16000AGL. If we continue tilting up we can progressively scan the vertical aspect of the cell, and find the altitude of greatest intensity, as well as approximate tops (wet tops). The most important information gained by this technique is the accurate location of storm cells, without proper tilt orientation we could mistake a strong cell for an area of light precipitation.

CAUTION: weather radar emits harmful radiation, it should not be operated when people are standing within 50 feet of radome or during refueling. The safe and effective use and interpretation of airborne weather radar comes with experience. It is an active system: you must adjust gain, tilt, and range settings to actively scan the sky. Keep the weather radar in standby when not in use, when needed it will be available. (some units take 3 or more minutes to warm up.) When convective activity exists you should start using radar to scan the sky before you take off and for the duration of the flight. Interpret the information and decide on a deviation plan before 40NM. Continue to adjust your flight path accordingly. As a general recommendation avoid all storms by: 5NM when flying below the freezing level 10NM when flying above the freezing level 20NM for any storm changing shape rapidly or displaying characteristics of severe weather. NOTE: This is a generalization only, severe weather is dynamic and impossible to accurately predict. Weather avoidance is dependant on equipment quality, aircraft type, pilot experience, and specific conditions.

Radome Radome is a dome-shaped protective enclosure for a radar antenna, made from materials that do not interfere with the transmission and reception of radio waves.

Radome

Conclusion Properties of wave are very essential for a better understanding on how radar and other instruments works. Radar is very useful for navigation purposes, safety purposes and very helpful as well in airport management.