Radio Waves b711k

Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Radio waves have frequencies from 300 GHz to as low as 3 kHz, and corresponding wavelengths ranging from 1 millimeter to 100 kilometers. Like all other electromagnetic waves, they travel at the speed of light. Naturally occurring radio waves are made by lightning, or by astronomical objects. Artificially generated radio waves are used for fixed and mobile radio communication, broadcasting, radar and other navigation systems, communications satellites, computer networks and innumerable other applications. Different frequencies of radio waves have different propagation characteristics in the Earth's atmosphere; long waves may cover a part of the Earth very consistently, shorter waves can reflect off the ionosphere and travel around the world, and much shorter wavelengths bend or reflect very little and travel on a line of sight. Electromagnetic radiation (EM radiation or EMR) is a form of energy emitted and absorbed by charged particles which exhibits wave-like behavior as it travels through space. EMR has both electric andmagnetic field components, which stand in a fixed ratio of intensity to each other, and which oscillate in phase perpendicular to each other and perpendicular to the direction of energy and wave propagation. In avacuum, electromagnetic radiation propagates at a characteristic speed, the speed of light.; EMR is classified according to the frequency of its wave. The electromagnetic spectrum, in order of increasing frequency and decreasingwavelength, consists of radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays. The eyes of various organisms sense a somewhat variable but relatively small range of frequencies of EMR called the visible spectrum or light. The maximum RVR reading is 2,000 metres or 6,000 feet, above which it is not significant and thus does not need to be reported. three transmissometers are provided, one at each end of the runway and one at the midpoint

If the airfield has RVR capabilities, it will be included in the ATIS or in reports from ATC. When RVR equipment is available, it is required to be reported when the visibility is below 1500 meters. All operational RVRs will be included in the report (i.e. RVR for touchdown, midpoint, and rollout) and can be reported in both meters and feet. RVR in METARS Like the verbal report of ATIS, METAR RVR reports the entire number. The format isR(XXX) Runway Designator including (L)eft (C)enter or (R)ight /(XXXX) 4 digit visibility in feet, for example: METAR KBNA 281250Z 33018KT 290V360 1/2SM R31/2700FT SN BLSN FG VV008 00/M03 A2991 RMK RAE42SNB42 R31/2700FT = Runway three one RVR two thousand seven hundred Aircrew may also see the following coding: M Indicates that RVR is less than lowest reportable sensor value (e.g. M0600FT) P Indicates RVR greater than highest reportable sensor value (e.g. P6000FT) V Variable If the RVR is variable between 2000 and 4000 feet for runway 6L: (R06L/2000V4000FT) N Indicates observation is Not changing significantly (e.g. R22/P1500N) U indicates an improvement or that the visibility is going Up (e.g. R22/P1000U) D indicates the visibility is decreasing or going Down (e.g. R04/P1500D) As I said, RVR can also be reported in meters. The biggest difference is that the FT suffix has been left out. You may see something like: METAR LBBG 041600Z 12003MPS 310V290 1400 R04/P1500N R22/P1500U +SN BKN022 OVC050 M04/M07 Q1020 NOSIG 9949//91= R04/P1500N = Runway zero four RVR one thousand five hundred meters and not changing significantly R22/P1500U = Runway two two RVR one thousand five hundred meters and rising.

RVR on Approach Plates Unlike the METAR report, the required RVR in an approach plate may only contain two digits. For example, 4000 feet RVR required would appear as RVR40. It's also important to note that on instrument approach plates, if the ceiling is followed by a dash (-) the visibility required is statue miles, where as if the ceiling is followed by a slash (/) the visibility required is in RVR.

S-ILS 14

DH

VIS

HAT

MILITARY

1165 /

24

200

(200-1/2)

Finally, nothing is ever simple is it. On the approach plates, RVRs listed in feet are not followed by the suffix FT, instead it is RVRs measured in meters that have a suffix and that suffix would simply be simply the letter ‘m.’

Radar Basic Principles The following figure shows the operating principle of a primary radar set. The radar antenna illuminates the target with a microwave signal, which is then reflected and picked up by a receiving device. The electrical signal picked up by the receiving antenna is called echo or return. The radar signal is generated by a powerful transmitter and received by a highly sensitive receiver.

Basic Principle of Operation The technical principle of weather radar is very similar to that of Primary Surveillance Radar (PSR) and it suffers from many of the same types of problems. The most important difference consists that an aim only will be detected at a radar unit for the air surveillance (Target visible: yes/no). It will be measured only the coordinates of the aim location. However, at a meteorological radar the echo signal will be estimated. These data finally give information about this, in which intensity and in which consistency reflective objects exist in the observation room. Several other major operating differences exist. This is often due to the fact that the shape of the „object of interest” is considerably different (weather is normally much larger and more fluid than moving targets for example) and the object velocity is normally considerably less than that of an aircraft or other flying „machine”. Best detection of „weather” objects takes place at different frequencies. (This one having another meaning in the meteorological radar than in a multi-frequency PSR system.)

transmitted energy backscatter

Figure 2: Radar principle

The familiar diagram shows high power transmissions hitting the object and reflections being scattered back (i.e. reflected or „backscattered”) towards the transmitting antenna to be interpreted by a sensitive receiver system (as well as reflected in a diffuse pattern). The signal is of a particular power (e.g. 850 kW) but the returns echoed of objects and weather are normally quite weak and a highly sensitive receiver is required to identify and interpret these. For PSR systems, the reflections of interest are those from aircraft and other flying objects. This is quite different to the reflections of interest being weather formations. For PSR, weather is regarded as noise and clutter and is filtered out. For weather radar, reflections from aircraft are a cause of noise and clutter. Both PSR and weather radar systems suffer from problems of ground or terrain clutter, refraction and other sources of noise and clutter.

Explain limacon - In geometry, a limaçon or limacon (pron.: /ˈlɪməsɒn/), also known as a limaçon of Pascal, is defined as a roulette formed when a circle rolls around the outside of a circle of equal radius. It can also be defined as the roulette formed when a circle rolls around a circle with half its radius so that the smaller circle is inside the larger circle. Thus, they belong to the family of curves called centered trochoids; more specifically, they are epitrochoids. The cardioid is the special case in which the point generating the roulette lies on the rolling circle; the resulting curve has a cusp. The term derives from the French word limaçon, which refers to small snails (Latin limax). Depending on the position of the point generating the curve, it may have inner and outer loops (giving the family its name), it may be heartshaped, or it may be oval. A limaçon is a bicircular rational plane algebraic curve of degree 4.

1) Explain why a plane stalls? What happens to the airflow over the wing? Explain the movement of the centre of pressure up to and after an aerofoil has stalled. Why is there a nose dipping tendency? On top of this they also ask you to write out the lift formula L=CL ½ Þ V2 S and explain the stall using the formula. 2) Engine failure after take off. What are the immediate actions (idle, feather, cut off) and what is the best glide speed? What is the minimum height you need to be at in order to commence a 180* turn and make it back to the field? What factors does a pilot need to bear in mind when doing this (wind, stall speed increases in the turn etc)? If you take off at max weight and you have engine problems (read not failure), are you allowed to come back and land straight away? 3) Meteorology. They ask you to define a host of met terminology. Make sure you know your isobars from your isoclinals and your DALR from your SALR. They also might ask you about thunderstorms and weather associated with a big developing CB, i.e. downdraughts, micro bursts, hail etc. 2. Understand how a stable environment such as warm advection will have on the ocean surface and how and unstable environment such as cold advection will have. 3. Know the geography and climate of where you will be forecasting. If you will be concentrating on areas near the UK, you likely know the usual storm track during different times of year and this will help when a big storm is coming in winter across the Atlantic and very large swells are expected to be generated.