# ATAC203 Avionics Systems > # [[C203 Week 4| ◀️ ]]  [[C203 Home| Home ]]  [[C203 Week 6| ▶️ ]]               [[QR C203T SSGW05| 🌐 ]] [📝](https://excalidraw.com/) > # [[C203 Week 5#ATAC203 Avionics Systems|Week 5]] >- [[C203 Week 5#Low Range Radio Altimeter LRRA|LRRA]] >- [[C203 Week 5#ATC Transponders|ATC Transponders]] >- [[C203 Week 5#Traffic Alert and Collision Avoidance System TCAS|TCAS]] >- [[C203 Week 5#Air Data Computer ADC|ADC]] >- [[C203 Week 5#Weather Radar WX|WX]] ^77c5ac >[!jbPlus|c-blue]- Lesson Intro >### What > >This week we will be looking at five important avionics systems. > >### Why > >No matter the type of aircraft you may eventually work on, these systems are likely to be part of the configuration. All are critical to flight safety, and your understanding of these systems will serve you well in your career. > >### Testing > >You will be tested on this material on Graded Quiz 4 and the Final Test. > >#### Approach and Objectives >By understanding the following topics, you will have achieved the learning outcome for this lesson. Consult your course outline for the learning outcomes and other details of this course. >##### Course Learning Objectives >- L1 CLO 12. Explain [[LRRA]], [[ATC Transponder|ATC]], [[TCAS]], [[ADC]], [[WX]] ## Low Range Radio Altimeter (LRRA) >[!aside]- Ref >[[LRRA|🗺️]] ### LRRA Purpose and Description %%==[[Faculty/Student/Content/C203/Master QB#Q00173|Q]]==%% %%==[[Faculty/Student/Content/C203/Master QB#Q00174|Q]]==%% %%==[[Faculty/Student/Content/C203/Master QB#Q00175|Q]]==%% %%==[[Faculty/Student/Content/C203/Master QB#Q00176|Q]]==%% - [[Height]] above ground Low Range Radio Altimeter (LRRA) is also known as Radio Altimeter, Radar Altimeter, and RADALT. It provides very accurate height above the ground information, or altitude. The word height is used with LRRA because it distinguishes it from the [[pressure altimeters|barometric altimeter]] and specifically refers to the aircraft height above the terrain, that is, the surface of the earth over which they are flying. It is important to note that this altitude is in reference to the ground, and not to [[MSL]] . LRRA is considered an essential part of aviation [[Navigation|navigation]]. It was introduced in the late 1930s. %%#JBXXX%% The LRRA is limited to 2500 ft [[AGL]], and thus is not generally used in flight except when in the [[Final Approach|approach phase]] of the flight. It can be coupled to the [[Autoland]] system and is an essential part of the Ground Proximity Warning System ([[GPWS]]). #### Decision Height One key feature of the LRRA is the [[Decision Height]] feature. This pilot adjustable setting moves a bug on the indicator that will illuminate a [[warning light]] when the [[altitude]] is reached. The decision referred to is the decision to land. Typically, if a pilot cannot see the [[runway]] lights or other aids at the DH he has set, he will perform a [[go around]], that is, he/she will not land. It should be noted that LRRA is one of the systems that [[GPS]] is not likely to fully replace. Despite the many strengths of GPS, it is not well suited to accurate measurement of airspeed or [[altimetry]] (the measurement of altitude). ### LRRA Components - Ground There are no ground components for the LRRA ### LRRA Components - Onboard %%==[[Faculty/Student/Content/C203/Master QB#Q00177|Q]]==%% %%==[[Faculty/Student/Content/C203/Master QB#Q00214|Q]]==%% Onboard components of the LRRA include the following: * [[Indicator]] * [[Transceiver]] * [[radio transmission|Transmit]] [[Antenna]] * [[Receive]] [[Antenna]] Because of the nature of the operation of the LRRA, it requires two antennas, one for [[radio transmission|transmission]] and another for reception. Only on much smaller and cheaper aircraft will you find a combined antenna, and the sacrifice is [[accuracy]], as the altimeter transceiver will have to alternate between transmitting and receiving. ### LRRA Theory of Operation %%==[[Faculty/Student/Content/C203/Master QB#Q00178|Q]]==%% - Measuring time of [[radio transmission|transmission]] and reflection - Measuring [[phase shift]] of [[radio transmission|transmission]] and reflection Different technologies can be used to achieve the LRRA function. [[Pulse techniques]] may use measurement of the time of [[radio transmission|transmission]] and reflection to determine altitude. However, the industry standard for radio altimeters rely on the fact that radio waves phase shift as they travel. The airborne LRRA transceiver transmits an [[FM]] signal via the [[radio transmission|transmit]] antenna that is reflected by the terrain back to the aircraft and picked up by the receive antenna. The transceiver compares the [[phase]] and [[frequency]] of the transmitted signal with the phase and frequency of the received signal to determine the aircraft's distance above the ground in feet. [[Pasted image 20210108221830.png|➡]]![[Pasted image 20210108221830.png|350]] This graphic indicates a few things of interest to us. The use of the two antennas can be noted, as well as the actual altitude being measured. On the right is a simplified graphic of the changes in an FM signal when used in this manner. ### LRRA Indications %%==[[Faculty/Student/Content/C203/Master QB#Q00179|Q]]==%% - 100s of feet [[AGL]] [[Pasted image 20210108222057.png|➡]]![[Pasted image 20210108222057.png|350]] The LRRA indicator shows 100s of feet up to 2500 ft. Often, as in the above graphic, the hundreds digits alone are displayed to reduce clutter, and the x100 is applied to the scale. The indicator points to the actual height of the aircraft above the ground. #### Decision Height bug %%==[[Faculty/Student/Content/C203/Master QB#Q00180|Q]]==%% %%==[[Faculty/Student/Content/C203/Master QB#Q00181|Q]]==%% [[Pasted image 20210108222311.png|➡]]![[Pasted image 20210108222311.png|350]] The [[Decision Height]] or Decision Altitude knob adjusts the position of the DH select bug on the [[altitude]] scale. When this altitude is indicated, the DH warning light will illuminate, initiating a [[decision-making]] process for the pilot in regards to the viability of landing. The DH bug may be placed anywhere on the altitude scale. ### LRRA Frequencies - 3400 MHz FM The LLRA transmits a 3400 MHz FM [[continuous wave]] [[carrier]] which is [[modulated]] to a depth of +/- 50MHz and a frequency of 100 Hz. ### ATC Transponders >[!aside]- Ref >[[ATC Transponder||🗺️]] #### ATC Transponders Purpose and Description %%==[[Faculty/Student/Content/C203/Master QB#Q00182|Q]]==%% - Provides [[Identity]], [[Position]] - [[Altitude]] in advanced systems The Air Traffic Control [[transponder]] system provides indication to [[Air Traffic Control]]lers of an aircraft's [[identity]], [[position]], and in advanced systems, [[altitude]]. #### ATC Transponder Components - Ground [[Pasted image 20210108222558.png|➡]]![[Pasted image 20210108222558.png|350]] Ground components of ATC include a transceiver ([[interrogator]]) and antenna installations. ##### ATC Transponder Components - Onboard %%==[[Faculty/Student/Content/C203/Master QB#Q00183|Q]]==%% %%==[[Faculty/Student/Content/C203/Master QB#Q00184|Q]]==%% %%==[[Faculty/Student/Content/C203/Master QB#Q00222|Q]]==%% %%==[[Faculty/Student/Content/C203/Master QB#Q00223|Q]]==%% Onboard components of the ATC include a [[transponder]] and [[antenna]]e. [[Pasted image 20210108222725.png|➡]]![[Pasted image 20210108222725.png|350]] The antenna is shaped as a fin to reduce [[aerodynamic drag]]. This antenna is suitable for installation on [[Metal]] [[fuselage]]s. In the case of [[composite]] fuselages, the antenna requires an additional sheet of metal to act as a [[ground plane]]. Since glass fiber fuselages are transparent to [[radio waves]], it may be more convenient to install a simple antenna inside the aircraft. Such an antenna does not require any holes in the fuselage, it does not generate aerodynamic drag and can not be broken away while handling the aircraft: [[Pasted image 20210108222921.png|➡]]![[Pasted image 20210108222921.png|350]] #### ATC Transponder Theory of Operation ##### Primary Surveillance Radar >[!aside]- Ref >[[PSR|🗺️]] [[PSR]] enables [[air traffic control]] to detect aircraft in the controlled zone. A rotating antenna [[transmits]] [[pulses]] that are reflected by the aircraft back to the [[antenna]]. A synchronized rotating scope display in the control tower shows a spot or blip at the bearing where the aircraft reflected the pulses. The time of the [[radio transmission|transmission]] and reception of the reflections is measured to determine range, and is shown on the display as distance from the centre of the screen which represents the tower (or more specifically, its rotating antenna). [[Pasted image 20210108223234.png|➡]]![[Pasted image 20210108223234.png|350]] PSR has some significant limitations. It depends on pulses being reflected back from aircraft, so any issues with reflectivity, such as the size of the aircraft or its finish, may reduce the reflection and thus the range of the system. Further, [[altitude]] cannot be determined with this type of [[radar]], and there is no means to identify specific aircraft. ##### Secondary Surveillance Radar >[!aside]- Ref >[[Secondary Surveillance Radar|🗺️]] %%==[[Faculty/Student/Content/C203/Master QB#Q00185|Q]]==%% %%==[[Faculty/Student/Content/C203/Master QB#Q00186|Q]]==%% %%==[[Faculty/Student/Content/C203/Master QB#Q00187|Q]]==%% [[ATC]] uses [[Secondary Surveillance Radar]]. SSR was developed to overcome limitations with PSR. Normally these capabilities are in addition to PSR, and the SSR antenna is co-located with the PSR antenna and rotates with it. SSR allows for active replies from the aircraft rather than a simple reflection of radar pulses. [[Pasted image 20210108223341.png|➡]]![[Pasted image 20210108223341.png|350]] SSR provides positive identification of all aircraft on the tower screen, regardless of their size. [[Altitude]] information is also available with certain onboard [[transponders]], as the aircraft provides this information back to the tower. The SSR antenna transmits [[interrogation]] pulses, at a [[frequency]] of 1030 MHZ. When an aircraft equipped with an [[ATC transponder]] receives the interrogation pulses, it sends reply pulses, at a frequency of 1090 MHZ. This reply will cause a clear indication to appear on the radar screen. ##### Pulse Codes and Modes A specific pattern of pulses is used for several purposes. The spacing between the P1 and P3 pulses determines the Mode of interrogation. [[Pasted image 20210108223452.png|➡]]![[Pasted image 20210108223452.png|350]] A "Mode A" interrogation is an [[identification]] [[interrogation]]. The [[pulse]] spacing between P1 & P3 is 8 microseconds, which identifies that the ground interrogator is requesting identification information from the aircraft. ##### Squawk %%==[[Faculty/Student/Content/C203/Master QB#Q00188|Q]]==%% [[Squawk]] identification is a technique where the tower instructs the pilot to [[radio transmission|transmit]] a 4 digit [[octal]] number. This number is selected by the pilot, on the [[ATC Transponder]] [[control head]]. [[Pasted image 20210108223617.png|➡]]![[Pasted image 20210108223617.png|350]] When the pilot does so, the blip on the radar screen associated with the aircraft glows and indicates which aircraft has squawked. Specific codes apply to various aspects of flight: ###### 1200 [[VFR]] flight, this is the standard [[squawk]] code used in US airspace when no other has been assigned. ###### 7000 VFR standard squawk code for most of European airspace. Others are reserved for emergencies: ###### 7700 %%==[[Faculty/Student/Content/C203/Master QB#Q00189|Q]]==%% Basic in flight [[emergency]] code. will cause alarms to go off at all stations that pick it up and grant immediate attention from [[air traffic controller]]s monitoring the area. ###### 7600 No [[radio]]. This code lets controllers know that a radio failure has occurred on the plane. Planes with a radio failure are given priority over other, non-emergency traffic, and ATC will communicate with them via aviation light signals. Remember we said that aircraft [[comms]] were an important flight safety requirement. This code supports the idea that no radios is a critical emergency. ###### 7500 Hijack code. A plane squawking this code will be given any assistance requested. If the plane alternates between 7500 and 7700 rapidly, it means a request for immediate, armed intervention in the hijacking. [[SquawkPic.png|😎]] ###### 0000 Military escort ##### Mode C %%==[[Faculty/Student/Content/C203/Master QB#Q00190|Q]]==%% A "Mode C" interrogation is an [[altitude]] [[interrogation]]. The pulse spacing between P1 & P3 of 21 microseconds instructs the aircraft [[ATC transponder]] to reply with altitude information. This information does not come from the control head, it is provided by altitude sensing devices such as: * Encoding [[Altimeter]] * Air Data Computer * Blind Encoder ##### Suppression Cable We saw in the [[C203 Week 4#Suppressor Cable|DME section]] a mention of a suppression cable (also commonly referred to as a suppressor cable). This is the system at the other end of that cable. This component can be responsible for snags on both [[ATC Transponder|ATC]] and [[DME]] at the same time. This is because the ATC transponder, and the DME interrogator operate in the same frequency range. A suppression system must be in place to prevent one system from transmitting into the other. This cable ensures that both signals are not lost by transmitting at the same time. ##### Side Lobe Suppression %%==[[Faculty/Student/Content/C203/Master QB#Q00191|Q]]==%% Even [[directional]] antennas will [[radio transmission|transmit]] in all directions, resulting in "[[Side Lobes]]". If a transponder were to reply to a side lobe, the ATC scope would show an erroneous position on the screen. A Side Lobe Suppression system "SLS' must be employed. [[Pasted image 20210108224056.png|➡]]![[Pasted image 20210108224056.png|350]] A P2 pulse is transmitted at lower power than P1 and P3 through an [[omnidirectional]] [[antenna]] as part of the [[array]]. When the aircraft can detect the sidelobes of the interrogations, rather than immediately responding (in error) it compares the amplitude or power of the pulses. If the P1 and P3 pulses are similar to the P2 pulses, it indicates these P1 and P3 pulses are weak because they come from the [[sideband]]. The aircraft will not respond. When, however, the aircraft transponder detects a difference of more than 9db between the P1/P3 and the P2 pulses, it knows that the aircraft is in the main [[radio transmission|transmission]] [[lobes|lobe]], as P1 and P3 are at full power, but P2 remains at its lower output. The aircraft knows to respond at this time, ensuring accurate positional information onscreen in the tower. So: The P2 pulse is used to provide [[side lobe suppression]], thereby preventing unwanted replies from the aircraft. ##### Transponders %%==[[Faculty/Student/Content/C203/Master QB#Q00192|Q]]==%% There are three different types of transponders for ATC: * [[Mode A]] * [[Mode C]] * [[Mode S]] All mode A, C, and S [[transponders]] include an "ident" button, short for Identify. When [[radar]] equipment receives the ident signal, it results in the aircraft's blip "blossoming" on the ATC radar scope. This is describing a glowing effect on the aircraft's symbol on the ATC screens in the tower. This is often used by the controller to locate the aircraft amongst others by requesting the ident function from the pilot. ###### Mode A transponders Mode A transponders are most basic kind of transponder and are usually found on older aircraft. [[Pasted image 20210108224223.png|➡]]![[Pasted image 20210108224223.png|350]] It can be programmed to [[radio transmission|transmit]] the four digit transponder or [[squawk]] code. ###### Mode C Transponders %%==[[Faculty/Student/Content/C203/Master QB#Q00193|Q]]==%% A more common type of transponder and found on newer aircraft. [[Pasted image 20210108224300.png|➡]]![[Pasted image 20210108224300.png|350]] Just like a mode A transponder a mode C transponder can have a squawk code. In addition to that it can also [[radio transmission|transmit]] its current [[pressure altitude]] to the ATC unit. We specify pressure altitude to indicate that we are not talking about radar altitude, i.e. [[RADALT]]. Rather we are talking about [[barometric altimeter]]s providing this information. This additional feature is required in some control zones in Canada to assist the ATC unit in [[vertical separation]] of aircraft. Vertical separation is a safety measure to give aircraft different altitudes to fly. This ensures they will never collide. I would like you to pause and think about that. Aircraft can be flying in all directions, even in close proximity, but if they are not at the same altitude, they cannot collide. ###### Mode S Transponders %%==[[Faculty/Student/Content/C203/Master QB#Q00194|Q]]==%% Mode S (Selective) transponders are designed to help air traffic control in busy areas and allow automatic collision avoidance. [[Pasted image 20210108224354.png|➡]]![[Pasted image 20210108224354.png|350]] [[Mode S]] is mandatory in [[controlled airspace]] in many countries. Some countries require that all aircraft be equipped with Mode S, even in uncontrolled airspace. However in the field of [[GA]], there have been objections to these moves, because of the cost, size, limited benefit to the users in [[uncontrolled airspace]], and, in the case of [[balloons]] and [[gliders]], the power requirements for these aircraft that do not have electrical systems. Mode S transponders can relay additional information, including the permanent identity of the aircraft, [[Traffic Information Service]], or weather information using a fixed [[radar]] installation to send information which is then displayed on the moving map. Mode A/C replies should be [[inhibited]] when the aircraft is on the ground to prevent [[interference]] when in close proximity to an [[interrogator]] or other aircraft. All other transmissions are to remain active to enable communication with other aircraft. Because of the radar frequencies involved, waveguides are used in the ATC transponder for more effective [[radio transmission|transmission]] of power. There will be more on why this is in another part of the course. #### ATC Transponder Indications ##### Control Head %%==[[Faculty/Student/Content/C203/Master QB#Q00195|Q]]==%% Onboard indications are simply the positions on the [[control head]], including the 4 digit pilot selectable [[squawk]] code. Air Control indications are radar screens in the terminal, which indicate position, altitude, ident and other information for [[Air Traffic Controllers]]. #### Limitations Secondary radar is, because of the nature of radar itself, susceptible to interference from obstructions of any sort, including [[precipitation]]. ### Traffic Alert and Collision Avoidance System (TCAS) >[!aside]- Ref >[[TCAS|🗺️]] #### TCAS Purpose and Description %%==[[Faculty/Student/Content/C203/Master QB#Q00196|Q]]==%% %%==[[Faculty/Student/Content/C203/Master QB#Q00197|Q]]==%% - Communicates with other aircraft - Provide [[advisories]] to pilot Traffic Alert and Collision Avoidance System ([[TCAS]]) detects the presence of nearby aircraft equipped with transponders that reply to Modes A, C or S interrogations. It continuously evaluates the [[collision]] threat potential of any of these aircraft. Its primary purpose is to issue [[Resolution Advisories]] to the pilot, that is, instructions to avoid collision with another aircraft. #### TCAS Components - Ground %%==[[Faculty/Student/Content/C203/Master QB#Q00198|Q]]==%% There are no ground components for TCAS. #### TCAS Components - Onboard Onboard Components consist of a [[Mode S]] [[transponder]]. Other aircraft must be equipped with either a [[Mode A]], [[Mode C]] or [[Mode S]] transponder. ##### Antennas %%==[[Faculty/Student/Content/C203/Master QB#Q00199|Q]]==%% The antennas used by [[TCAS II]] include a [[directional]] antenna which is mounted on top of the aircraft and an [[omnidirectional]] transmitting and receiving antenna mounted on the bottom of the aircraft which provides [[range]] and altitude data on targets that are below the TCAS aircraft. #### TCAS Theory of Operation %%==[[Faculty/Student/Content/C203/Master QB#Q00200|Q]]==%% %%==[[Faculty/Student/Content/C203/Master QB#Q00201|Q]]==%% %%==[[Faculty/Student/Content/C203/Master QB#Q00202|Q]]==%% Detection and tracking of an [[intruder]] aircraft's [[transponder]] is performed via TCAS [[radio transmission|transmission]] and receptions on top and bottom-mounted directional antennas. TCAS will survey valid transponder traffic approximately 15-40nm forward, 5-15nm aft, and 10-20nm on the sides, as well as altitudes within 9,000 feet of own-altitude. [[Pasted image 20210108225022.png|➡]]![[Pasted image 20210108225022.png|350]] It will issue a TA ([[Traffic Advisory]]) to alert the crew that closing traffic is in the vicinity. If the intruder gets closer, TCAS II will issue an RA ([[Resolution Advisory]]) to maintain safe vertical separation between the aircraft and the intruder. (Remember [[C203 Week 5#Mode C Transponders|this]]). This resolution advisory is the primary purpose of TCAS. The [[Mode S]] Transponder performs the normal ATC functions of existing Mode A&C transponders. The mode S transponder is also used to provide air-to-air data exchange between TCAS-equipped aircraft to ensure coordinated, complementary resolution advisories. So, if a tracked aircraft is a collision threat, the computer selects the best avoidance maneuver. If the threat aircraft is also equipped with TCAS II this maneuver is coordinated. In the event of a conflict between Air Traffic Control (ATC) instructions and a Traffic Collision Avoidance System (TCAS) alert, ==TCAS always takes priority==; meaning the pilot must follow the TCAS instructions, even if it contradicts ATC guidance. This is because TCAS is designed to autonomously detect and avoid imminent mid-air collisions, making its safety priority higher than ATC instructions which might not always have the most up-to-date information about nearby aircraft. #### TCAS Indications ##### Traffic Advisory Display The "Traffic Advisory" display depicts the position of the traffic relative to the TCAS aircraft. This display can be a dedicated TCAS display: [[Pasted image 20210108225216.png|➡]]![[Pasted image 20210108225216.png|350]] ##### Resolution Advisory Display %%==[[Faculty/Student/Content/C203/Master QB#Q00203|Q]]==%% %%==[[Faculty/Student/Content/C203/Master QB#Q00204|Q]]==%% The [[Resolution Advisory]] display is a standard [[Vertical Speed indicator]] modified to indicate the vertical rate that must be achieved to maintain safe separation from threatening aircraft. The RA display contains segmented red and green [[eyebrow lights]] around the vertical speed scale. The words "Traffic, Traffic" are annunciated at the time of the traffic advisory. If the encounter does not resolve itself, a resolution advisory is annunciated, e.g., "Climb, Climb, Climb." More and more, TCAS uses joint-use [[weather radar]] and traffic displays, or an electronic flight instrument system ([[EFIS]]) which combines traffic and resolution advisory information on the same [[scope]] face. [[Pasted image 20210108225434.png|➡]]![[Pasted image 20210108225434.png|350]] ### Air Data Computer (ADC) >[!aside]- Ref >[[ADC|🗺️]] #### ADC Purpose and Description %%==[[Faculty/Student/Content/C203/Master QB#Q00205|Q]]==%% %%==[[Faculty/Student/Content/C203/Master QB#Q00207|Q]]==%% Air Data Computers ([[ADC]]) process all air type data, converting it to [[electrical]] information to be used by displays and other systems to determine [[air speed]], [[mach number]], [[altitude]] and [[vertical speed]]. Air type data is the information from [[pitot]] systems and other sensors. More in a moment. ADC may also be known as: - CADC - Air Data Computer - DADC - Digital Air Data Computer - ADIRU - Air Data/Inertial Reference Unit #### ADC Components - Ground %%==[[Faculty/Student/Content/C203/Master QB#Q00206|Q]]==%% There are no ground components associated with ADC. #### ADC Components - Onboard Most modern aircraft are equipped with two ADCs to provide [[redundancy]]. #### ADC Theory of Operation ##### Traditional Air Data Aircraft that are not equipped with [[ADC]] apply [[static pressure]] and [[pitot pressure]] directly to the instruments. This diagram shows which instruments are fed by which types of air pressure. [[Pasted image 20210108225846.png|➡]]![[Pasted image 20210108225846.png|350]] ##### Air data to computer, not instruments %%==[[Faculty/Student/Content/C203/Master QB#Q00208|Q]]==%% On aircraft equipped with an [[ADC]], the pitot and static pressures are applied to the ADC rather than directly to the instruments. [[Transducers]] in the ADC convert these pressures to electrical signals. The electrical signals then drive the instruments in the cockpit ([[Altimeter]], [[IVSI]], [[MASI]], [[TAT]]). [[Pasted image 20210108225938.png|➡]]![[Pasted image 20210108225938.png|350]] [[Pasted image 20210108230010.png|➡]]![[Pasted image 20210108230010.png|350]] Look carefully at the above [[block diagram]] to see which air pressures contribute to the various indications and outputs on the right. It may help you to see a larger block diagram to give you insight into virtually every modern computer driven avionics system. In fact, this block diagram applies to any computer: ```mermaid graph LR subgraph Basic Computer Block Diagram A(Input) --> B(Processing) B --> C(Output) end ``` %%- [ ] #JB redo this in excalidraw #Wdev #C203 %% It really is that simple. Now have a look at the preceding diagram from this perspective, and see that [[inputs]] have to be processed, sometimes combined, to provide the various outputs. This is how these systems are organized, and it should also be the way your understanding of these systems is organized. #### ADC Indications ##### Indications As described in [[C203 Week 5#ADC Theory of Operation|Theory of Operation]] ### Weather Radar (WX) #### WX Purpose and Description >[!aside]- Ref >[[Weather Radar|🗺️]] %%==[[Faculty/Student/Content/C203/Master QB#Q00209|Q]]==%% - Visual indication of [[precipitation]] WR provides the pilot with a visual indication of precipitation ahead of the aircraft. WR is the abbreviation for weather radar, but you may see WX as well. This is an old abbreviation for just the word weather. #### WX Components - Ground There are no ground components associated with aircraft equipped weather radars. #### WX Components - Onboard %%==[[Faculty/Student/Content/C203/Master QB#Q00210|Q]]==%% Onboard components of the [[Weather Radar|WR]] consist of a [[transceiver]] and an [[antenna]]. [[Waveguides]] are used instead of [[wire]] to carry [[RF]] energy due to its higher efficiencies at the [[frequencies]] used for [[radar]]. #### WX Theory of Operation %%==[[Faculty/Student/Content/C203/Master QB#Q00213|Q]]==%% - Simple RADAR The transceiver in the aircraft sends pulses of RF energy forward of the aircraft. This RF is reflected by precipitation and received back at the transceiver. These reflections can be shown on a screen to indicate weather systems. This is very similar to [[C203 Week 5#Primary Surveillance Radar|Primary Surveillance Radar]] #### WX Indications %%==[[Faculty/Student/Content/C203/Master QB#Q00211|Q]]==%% [[PPI]] (Pictorial Position Indicator) displays a visual representation of precipitation ahead of the aircraft. This enables the crew to steer around storm cells. The display may be colour or [[monochrome]] (one colour). Additionally, it may be [[superimposed]] with other info such as HSI indications, especially on [[EFIS]] equipped aircraft. [[Range Marks]] indicate distance from aircraft, and the position of the weather indicated is relative to the aircraft heading. [[Pasted image 20210108230519.png|➡]]![[Pasted image 20210108230519.png|350]] #### WX Limitations/Precautions %%==[[Faculty/Student/Content/C203/Master QB#Q00212|Q]]==%% Weather radar is good at detecting reflections from rain and snow, but it cannot "see" [[fog]], [[icing]], [[turbulence]], [[windshear]] and other [[atmospheric]] circumstances, and so the pilot knows that a clear weather radar screen does not necessarily mean there is no "weather". Also, some of these issues exist in the early formation stages of a [[thunderstorm]], and weather radar provides no warning of these phenomena. [[Advanced Avionics Handbook#Limitations of Both Types of Weather Radar Systems|📖]] **Dangerous to personnel** WX [[emits]] high energy RF which can be harmful to personnel. Remember from the [[C203 Week 1#The Electromagnetic Spectrum|Radio Theory lesson]] that these frequencies are not far from the ones used in [[microwave]] ovens! **Do not operate near personnel/fuel** Therefore, WX should not be operated in [[hangar]], or in vicinity of buildings and personnel. You should never look into a [[waveguide]] when power is on, and you should never operate the WX when the aircraft is being fueled. [[Pasted image 20210221045820.png|😎]] ![[More WX]] #### Week 5 Conclusion A reminder that may be useful for you to try this [template for an aide-memoire](https://excalidraw.com/#json=DbVuRsjvs1aIS_8tp77Qv,HWbNqPeNoyUVJgtZWJxyKw) that may help you to keep all of this information organized in preparation for testing. The information is laid out in a table, so it is a matter of understanding the material as you go, and then comparing it to the other systems. And of course, the weekly review quiz will help you to determine the level of detail and depth that you are responsible for on the course. This may seem like a lot of material. Be organized, and contact your prof at any time. > # [[C203 Week 4| ◀️ ]]  [[C203 Home| Home ]]  [[C203 Week 6| ▶️ ]]               [[QR C203T SSGW05| 🌐 ]]    [[FB C203|Please Help]]