Satellite Navigation and Avionics

VOR based RNA V uses the VOR receiver, antenna, and VOR display equipment, such as the CDI. The computer in the RNA V unit uses basic geometry and trigonometry calculations to produce heading, speed, and time readouts for each waypoint. VOR stations need to be within line-of sight and operational range from the aircraft for RNA V use. [Figure 11-124] RNA V has increased in flexibility with the development of GPS. Integration of GPS data into a planned VOR RNA V flight plan is possible as is GPS route planning without the use of any VOR stations. Radar Beacon Transponder A radar beacon transponder, or simply, a transponder, provides positive identification and location of an aircraft on the radar screens of ATC. For each aircraft equipped with an altitude encoder, the transponder also provides the pressure altitude of the aircraft to be displayed adjacent to the on-screen blip that represents the aircraft. [Figure 11-125] Radar capabilities at airports vary. Generally, two types of radar are used by air traffic control (ATC). The primary radar transmits directional UHF or SHF radio waves sequentially in all directions. When the radio waves encounter an aircraft, part of those waves reflect back to a ground antenna.

Calculations are made in a receiver to determine the direction VOR R.NAV HOLD USE DATA DSP PAR ENR NM KT MIN FRQ RAD DST APR VOR RNV HLD ILS USE DSP MODE DME WAYPOINT FREQ-RAD-DST NAV SYSTEM PULL IDOFF and distance of the aircraft from the transmitter. A blip or target representing the aircraft is displayed on a radar screen also known as a plan position indicator (PPI). The azimuth direction and scaled distance from the tower are presented giving controllers a two dimensional fix on the aircraft. [Figure 11-126] A secondary surveillance radar (SSR) is used by ATC to verify the aircraft’s position and to add the third dimension of altitude to its location. SSD radar transmits coded pulse trains that are received by the transponder on board the aircraft.

Mode 3/A pulses, as they are known, aid in confirming the location of the aircraft. When verbal communication is established with ATC, a pilot is instructed to select one of 4,096 discrete codes on the transponder. These are digital octal codes. The ground station transmits a pulse of energy at 1030 MHz and the transponder transmits a reply with Station Radial Waypoint Distance VOR flightpath RNAV flightpath Airport A VORTAC XYZ ZYX 108/15 ABC 348/19 ABC 015/30 XYZ 105/25 XYZ 167/16 VOR/DME ABC VOR/DME ZYX Airport B Phantom waypoints created by RNAV CLC computer This allows direct routes to be created and flown rather than flying from VOR to VOR.

11-53 A B C connects to a transponder to provide ATC with an aircraft’ s altitude displayed on a PPI radar screen next to the target that represents the aircraft. the assigned code attached at 1090 MHz. This confirms the aircraft’s location typically by altering its target symbol on the radar screen. As the screen may be filled with many confirmed aircraft, ATC can also ask the pilot to ident. By pressing the IDENT button on the transponder, it transmits in such a way that the aircraft’s target symbol is highlighted on the PPI to be distinguishable. Range marks Rotating sweep Echoes or returns from aircraft radar locates target aircraft on a scaled field.

To gain altitude clarification, the transponder control must be placed in the ALT or Mode C position. The signal transmitted back to ATC in response to pulse interrogation is then modified with a code that places the pressure altitude of the aircraft next to the target symbol on the radar screen. The transponder gets the pressure altitude of the aircraft from an altitude encoder that is electrically connected to the transponder. Typical aircraft transponder antennas are illustrated in Figure 11-127. The ATC/aircraft transponder system described is known as Air Traffic Control Radar Beacon System (ATCRBS). To increase safety, Mode S altitude response has been developed.

With Mode S, each aircraft is pre-assigned a unique identity code that displays along with its pressure altitude on ATC radar when the transponder responds to SSR interrogation. Since no other aircraft respond with this code, the chance of two pilots selecting the same response code on the transponder is eliminated. A modern flight data processor computer (FDP) assigns the beacon code and searches flight plan data for useful information to be displayed on screen next to the target in a data block for each aircraft. [Figure 11-128] Mode S is sometimes referred to as mode select. It is a data packet protocol that is also used in onboard collision avoidance systems. When used by ATC, Mode S interrogates one aircraft at a time. Transponder workload is reduced by not having to respond to all interrogations in an airspace.

11-54 Additionally, location information is more accurate with Mode S. A single reply in which the phase of the transponder reply is used to calculate position, called monopulse, is sufficient to locate the aircraft. Mode S also contains capacity for a wider variety of information exchange that is untapped potential for the future. At the same time, compatibility with older radar and transponder technology has been maintained. Transponder Tests & Inspections Title 14 of the Code of Federal Regulations (CFR) part 91, section 91.413 states that all transponders on aircraft flown into controlled airspace are required to be inspected and tested in accordance with 14 CFR part 43, Appendix F, every 24 calendar months. Installation or maintenance that may introduce a transponder error is also cause for inspection and test in accordance with Appendix F. Only an appropriately rated repair station, the aircraft manufacturer (if it installed transponder), and holders of a continuous airworthy program are approved to conduct the procedures. As with many radio- electronic devices, test equipment exists to test airworthy operation of a transponder. [Figure 11-129] Operating a transponder in a hangar or on the ramp does not immunize it from interrogation and reply. Transmission of certain codes reserved for emergencies or military activity must be avoided. The procedure to select a code during ground operation is to do so with the transponder in the OFF or STANDBY mode to avoid inadvertent transmission. Code 0000 is reserved for military use and is a transmittable code.

Code 7500 is used in a hijack situation and 7600 and 7700 are also reserved for emergency use. Even the inadvertent transmission of code 1200 reserved for VFR flight not under ATC direction could result in evasion action. All signals received from a radar beacon transponder are taken seriously by ATC. Altitude Encoders Altitude encoders convert the aircraft’s pressure altitude into a code sent by the transponder to ATC. Increments of 100 feet are usually reported. Encoders have varied over the years. Some are built into the altimeter instrument used in the instrument panel and connected by wires to the transponder.

Others are mounted out of sight on an avionics rack or similar out of the way place. These are known as blind encoders. On transport category aircraft, the altitude encoder may be a large black box with a static line connection to an internal aneroid. Modern general aviation encoders are smaller and more lightweight, but still often feature an internal aneroid and static line connection. Some encoders use microtransistors and are completely solid-state including the pressure sensing device from which the altitude is derived. No static port connection is required. Data exchange with GPS and other systems is becoming common. [Figure 11-130] When a transponder selector is set on ALT, the digital pulse message sent in response to the secondary surveillance radar interrogation becomes the digital representation of the pressure altitude of the aircraft. There are 1280 altitude codes, one for each 100 feet of altitude between 1200 feet mean sea level (MSL) and 126,700 feet MSL. Each altitude increment is assigned a code. While these would be 1280 of the same codes used for location and IDENT, the Mode C (or S) interrogation deactivates the 4096 location codes and causes the encoder to become active. The correct altitude code is sent to the transponder that replies to the interrogation.

The SSR receiver recognized this as a response to a Mode C (or S) interrogation and interprets the code as altitude code. Collision Avoidance Systems The ever increasing volume of air traffic has caused a corresponding increase in concern over collision avoidance. Ground-based radar, traffic control, and visual vigilance are no longer adequate in today’s increasingly crowded skies. Onboard collision avoidance equipment, long a staple in larger aircraft, is now common in general aviation aircraft. 11-55 traffic information on a PPI radar screen. A modern approach ATC PPI is shown. Targets representing aircraft are shown as little aircraft on the screen. The nose of the aircraft indicates the direction of travel. Most targets shown above are airliners. The data block for each target includes the following information either transmitted by the transponder or matched and loaded from flight plans by a flight data processor computer: call sign, altitude/speed, origination/destination, and aircraft type/ETA (ZULU time). A “C” after the altitude indicates the information came from a Mode C equipped transponder. The absence of a C indicates Mode S is in use. An arrow up indicates the aircraft is climbing. An arrow down indicates a descent. White targets are arrivals, light blue targets are departures, all other colors are for arrivals and departures to different airports in the area.

New applications of electronic technology combined with lower costs make this possible. Traffic Collision Avoidance Systems (TCAS) Traffic collision avoidance systems (TCAS) are transponder based air-to-air traffic monitoring and alerting systems. There are two classes of TCAS. TCAS I was developed to accommodate the general aviation community and regional airlines. This system identifies traffic in a 35–40 mile range of the aircraft and issues Traffic Advisories (TA) to assist pilots in visual acquisition of intruder aircraft. TCAS I is mandated on aircraft with 10 to 30 seats. TCAS II is a more sophisticated system. It is required internationally in aircraft with more than 30 seats or weighing more than 15,000 kg. TCAS II provides the information of TCAS I, but also analyzes the projected flightpath of approaching aircraft. If a collision or near miss is imminent, the TCAS II computer issues a Resolution Advisory (RA). This is an aural command to the pilot to take a specific evasive action (i.e., DESCEND). The computer is programmed such that the pilot in the encroaching aircraft receives an RA for evasive action in the opposite direction (if it is TCAS II equipped). [Figure 11-131] The transponder of an aircraft with TCAS is able to interrogate the transponders of other aircraft nearby using SSR technology (Mode C and Mode S). This is done with a 1030 MHz signal. Interrogated aircraft transponders reply with an encoded 1090 MHz signal that allows the TCAS computer to display the position and altitude of each aircraft. Should the aircraft come within the horizontal or vertical distances shown in Figure 11-131, an audible TA is 11-56 A1 A2 A4 B1 B2 B4 C1 C2 C4 D4 PIN 1 PIN 4 PIN 7 PIN 8 PIN 14 POWER MOTION PIN 15 announced. The pilot must decide whether to take action and what action to take. TCAS II equipped aircraft use continuous reply information to analyze the speed and trajectory of target aircraft in close proximity. If a collision is calculated to be imminent, an RA is issued.

TCAS target aircraft are displayed on a screen on the flight deck. Different colors and shapes are used to depict approaching aircraft depending on the imminent threat level. Since RAs are currently limited to vertical evasive maneuvers, some stand-alone TCAS displays are electronic vertical speed indicators. Most aircraft use some version of an electronic HSI on a navigational screen or page to display TCAS information. [Figure 11-132] A multifunction display may depict TCAS and weather radar information on the same screen. [Figure 11-133] A TCAS control panel [Figure 11-134] and computer are required to work with a compatible transponder and its antenna(s). Interface with EFIS or other previously installed or selected display(s) is also required.

TCAS may be referred to as airborne collision avoidance system (ACAS), which is the international name for the same system. TCAS II with the latest revisions is known as Version 7. The accuracy and reliability of this TCAS information is such that pilots are required to follow a TCAS RA over an ATC command. ADS-B Collision avoidance is a significant part of the FAA’s NextGen plan for transforming the National Airspace aircraft. System (NAS). Increasing the number of aircraft using the same quantity of airspace and ground facilities requires the implementation of new technologies to maintain a high level of performance and safety. The successful proliferation of global navigation satellite systems (GNSS), such as GPS, has led to the development of a collision avoidance system known as Automatic Dependent Surveillance-Broadcast (ADS-B). ADS-B is an integral part of NextGen program.

The implementation of its ground and airborne infrastructure is currently underway. ADS-B is active in parts of the United States and around the world. [Figure 11-135] ADS-B is considered in two segments: ADS-B OUT and ADS-B IN. ADS-B OUT combines the positioning information available from a GPS receiver with on-board flight status information, i.e., location including altitude, velocity, and time. It then broadcasts this information to other ADS-B equipped aircraft and ground stations. [Figure 11-136] Two different frequencies are used to carry these broadcasts with data link capability. The first is an expanded use of the 1090 MHz Mode-S transponder protocol known as 1090 ES.

The second, largely being introduced as a new broadband solution for general aviation implementation of ADS-B, is at 978 MHz. A 978 universal access transceiver (UAT) is used to accomplish this. An omni-directional antenna is required in addition to the GPS antenna and receiver. Airborne receivers of an ADS-B use the information to plot the location and movement of the transmitting aircraft on a flight deck display similar to TCAS. [Figure 11-137] Inexpensive ground stations (compared to radar) are constructed in remote and obstructed areas to proliferate ADS-B. Ground stations share information from airborne ADS-Bs with other ground stations that are part of the air 11-57 traffic management system (ATMS). Data is transferred with no need for human acknowledgement. Microwave and satellite transmissions are used to link the network.

For traffic separation and control, ADS-B has several advantages over conventional ground-based radar. The first is the entire airspace can be covered with a much lower expense. The aging ATC radar system that is in place is expensive to maintain and replace. Additionally, ADS-B provides more accurate information since the vector state is generated from the aircraft with the help of GPS satellites. Weather is a greatly reduced factor with ADS-B. Ultra-high frequency GPS transmissions are not affected. Increased positioning accuracy allows for higher density traffic flow and landing approaches, an obvious requirement to operate more aircraft in and out of the same number of facilities. The higher degree of control available also enables routing for fewer weather delays and optimal fuel burn rates. Collision avoidance is expanded to include runway incursion from other aircraft and support vehicles on the surface of an airport.

ADS-B IN offers features not available in TCAS. Equipped aircraft are able to receive abundant data to enhance situational awareness. Traffic information services-broadcast (TIS-B) supply traffic information from non-ADS-B aircraft and ADS-B aircraft on a different frequency. Ground radar 2.1 NM 3.3 NM 25 seconds 40 seconds 20 NM RA issued for 300 KT TA issed Closure Surveillance Range Targets displayed on-screen (TCAS I & II) Traffic advisory (TA) region (TCAS I & II) TA Region RA Region (TCAS II only) Resolution advisory (RA) region (TCAS II only) Pilot commanded to take evasive action Pilot alerted to traffic in range Range criterion Intruder Altitude criterion 1200' 850' 1200' 850' aircraft in close proximity. The TCAS computer alerts the pilot as to the presence of an intruder aircraft and displays the aircraft on a screen in the flight deck. Additionally, TCAS II equipped aircraft receive evasive maneuver commands from the computer that calculates trajectories of the aircraft to predict potential collisions or near misses before they become unavoidable.

11-58 speed indicator. TCAS/ATC ABOVE ABS BELOW REL ABOVE ABS BELOW FAIL REL N N XPDR STBY TA TEST TA/RA 0 000 L R 15 5 21 24 197 GS 356 TAS386 195° 17 HDG MAG TRAFFIC +30 +13 +02 −12 display. An open diamond indicates a target; a solid diamond represents a target that is within 6 nautical miles of 1,200 feet vertically. A yellow circle represents a target that generates a TA (25-48 seconds before contact). A red square indicates a target that generates an RA in TCAS II (contact within 35 seconds). A (+) indicates the target aircraft is above and a (-) indicates it is below. The arrows show if the target is climbing or descending.

monitoring of surface targets, and any traffic data in the linked network of ground stations is sent via ADS-B IN to the flight deck. This provides a more complete picture than air-to-air only collision avoidance. Flight information services-broadcast (FIS-B) is also received by ADS-B IN. Weather text and graphics, ATIS information, and NOTAMs are able to be received in aircraft that have 987 UAT capability. [Figure 11-138] transponder for ATC use and TCAS. ADS-B test units are available for trained maintenance personnel to verify proper operation of ADS-B equipment. This is critical since close tolerance of air traffic separation depends on accurate data from each aircraft and throughout all components of the ADS-B system. [Figure 11-139] Radio Altimeter A radio altimeter, or radar altimeter, is used to measure the distance from the aircraft to the terrain directly beneath it. It is used primarily during instrument approach and low level or night flight below 2,500 feet. The radio altimeter supplies the primary altitude information for landing decision height.

It incorporates an adjustable altitude bug that creates a visual or aural warning to the pilot when the aircraft reaches that altitude. Typically, the pilot will abort a landing if the decision height is reached and the runway is not visible. Using a transceiver and a directional antenna, a radio altimeter broadcasts a carrier wave at 4.3 GHz from the aircraft directly toward the ground. The wave is frequency stations with only solar or propane support. This is not possible with ground radar due to high power demands which inhibit remote area radar coverage for air traffic purposes. 11-59 ADS-B signal ADS-B signal Ground transceiver Conventional data networks GNSS position data Aircraft broadcast position, Altitude, Speed, etc.

stations along with other flight status information. modulated at 50 MHz and travels at a known speed. It strikes surface features and bounces back toward the aircraft where a second antenna receives the return signal. The transceiver processes the signal by measuring the elapsed time the signal traveled and the frequency modulation that occurred. The display indicates height above the terrain also known as above ground level (AGL). [Figure 11-140] A radar altimeter is more accurate and responsive than an air pressure altimeter for AGL information at low altitudes. The transceiver is usually located remotely from the indicator.

Multifunctional and glass flight deck displays typically integrate decision height awareness from the radar altimeter as a digital number displayed on the screen with a bug, light, or color change used to indicate when that altitude is reached. Large aircraft may incorporate radio altimeter information into a ground proximity warning system (GPWS) which aurally alerts the crew of potentially dangerous proximity to the terrain below the aircraft. A decision height (DH) window displays the radar altitude on the EADI in Figure 11-141. Weather Radar There are three common types of weather aids used in an aircraft flight deck that are often referred to as weather radar: 1. Actual on-board radar for detecting and displaying weather activity; 2. Lightning detectors; and 3. Satellite or other source weather radar information that is uploaded to the aircraft from an outside source.

11-60 UAT + MFD UAT + MFD Aircraft “See” each other AWOS Text weather radar weather VHF Wind barometer temp/DP etc. Visibility Ceiling Weather data A/C position also be transmitted. On-board weather radar systems can be found in aircraft of all sizes. They function similar to ATC primary radar except the radio waves bounce off of precipitation instead of aircraft. Dense precipitation creates a stronger return than light precipitation. The on-board weather radar receiver is set up to depict heavy returns as red, medium returns as yellow and light returns as green on a display in the flight deck. Clouds do not create a return. Magenta is reserved to depict intense or extreme precipitation or turbulence. Some aircraft have a dedicated weather radar screen. Most modern antennas and transceiver for a radio/radar altimeter (bottom).

11-61 KGRN NORT 2 KBJKBJCC KCLN L89L89 KGHR 308308 KLAR KLVL KHEFKHEF KCOSKCOS LAR HCT KFTCKFTC H8H82 KDEN KFTR KBUKBUCC KCENKCEN W GPH 25 NORTH UPH UP VS IG / AIR P NEXRAD AGE: 5min RAIN MIX SNOW L G H T H E A V Y 30NM 5 338 1 1652 200 46 13.7 2300 23.0 I MA NRSTWPT AUX corner of this EADI display uses the radar altimeter as the source of altitude information. aircraft integrate weather radar display into the navigation display(s). Figure 11-142 illustrates weather radar displays found on aircraft. Radio waves used in weather radar systems are in the SHF range such as 5.44 GHz or 9.375 GHz. They are transmitted forward of the aircraft from a directional antenna usually located behind a non-metallic nose cone. Pulses of approximately 1 micro-second in length are transmitted.

A duplexer in the radar transceiver switches the antenna to receive for about 2,500 micro seconds after a pulse is transmitted to receive and process any returns. This cycle repeats and the receiver circuitry builds a two dimensional image of precipitation for display. Gain adjustments control the range of the radar. A control panel facilitates this and other adjustments. [Figure 11-143] Severe turbulence, windshear, and hail are of major concern to the pilot. While hail provides a return on weather radar, windshear and turbulence must be interpreted from the movement of any precipitation that is detected. An alert is annunciated if this condition occurs on a weather radar system so equipped. Dry air turbulence is not detectable. Ground clutter must also be attenuated when the radar sweep includes any terrain features. The control panel facilitates this.

Special precautions must be followed by the technician during maintenance and operation of weather radar systems. The radome covering the antenna must only be painted with approved paint to allow the radio signals to pass unobstructed. Many radomes also contain grounding strips to conduct lightning strikes and static away from the dome. 10 10 20 20 DH200 -4 80 110 60 4 45 6 SPD LIM VI INOP NAV2 108.00 117.95 135.975 120.050 COM2MAP - NAVIGATION MAP NORTH UP NAV1 117.95 115.40 123.750 119.925 COM1GS 123kts DIS 53.2NM ETE 25:58 ESA 16800 30NM MAP WPT AUX NRST ENGINE NEXRAD ECHO TOP CLD TOP LTNG CELL MOV SIG / AIR METAR LEGEND MORE WX multifunctional navigation display with weather radar overlay (bottom).

When operating the radar, it is important to follow all manufacturer instructions. Physical harm is possible from the high energy radiation emitted, especially to the eyes and testes. Do not look into the antenna of a transmitting radar. Operation of the radar should not occur in hangars unless special radio wave absorption material is used. Additionally, operation of radar should not take place while the radar is pointed toward a building or when refueling takes place. Radar units should be maintained and operated only by qualified personnel. Lightning detection is a second reliable means for identifying potentially dangerous weather. Lightning gives off its own electromagnetic signal. The azimuth of a lightning strike can be calculated by a receiver using a loop type antenna such as that used in ADF. [Figure 11-144] Some lightning detectors make use of the ADF antenna. The range of the lightning strike is closely associated with its intensity. Intense strikes are plotted as being close to the aircraft.

Stormscope is a proprietary name often associated with lightning detectors. There are others that work in a similar 11-62 W X R D R LEFT MODE RIGHT MODE GAIN UCAL GAIN UCAL 0 15 UP DOWN 5 0 15 UP DOWN 5 TFR WX/T WX MAP GCS TFR WX/T WX TEST MAP GCS usually controlled by the inertial reference system (IRS) to automatically adjust for attitude changes during maneuvers so that the radar remains aimed at the desired weather target. The pilot may also adjust the angle and sweep manually as well as the gain. A dual mode control panel allows separate control and display on the left or right HSI or navigational display.

manner. A dedicated display plots the location of each strike within a 200 mile range with a small mark on the screen. As time progresses, the marks may change color to indicate their age. Nonetheless, a number of lightning strikes in a small area indicates a storm cell, and the pilot can navigate around it. Lightning strikes can also be plotted on a multifunctional navigation display. [Figure 11-145] A third type of weather radar is becoming more common in all classes of aircraft. Through the use of orbiting satellite systems and/or ground up-links, such as described with ADS-B IN, weather information can be sent to an aircraft in flight virtually anywhere in the world. This includes text data as well as real-time radar information for overlay on an aircraft’s navigational display(s). Weather radar data produced remotely and sent to the aircraft is refined through consolidation of various radar views from different angles and satellite imagery. This produces more accurate depictions of actual weather conditions. Terrain databases are integrated to eliminate ground clutter. Supplemental data includes the entire range of intelligence available from system.

the National Weather Service (NWS) and the National Oceanographic and Atmospheric Administration (NOAA). received in an aircraft along with a list of other weather information available through satellite or ground link weather information services. As mentioned, to receive an ADS-B weather signal, a 1090 ES or 970 UAT transceiver with associated antenna needs to be installed on board the aircraft. Satellite weather services are received by an antenna matched to the frequency of the service. Receivers are typically located remotely and interfaced with existing navigational and multifunction displays. Handheld GPS units also may have satellite weather capability. [Figure 11-147] Emergency Locator Transmitter (ELT) An emergency locator transmitter (ELT) is an independent battery powered transmitter activated by the excessive G-forces experienced during a crash. It transmits a digital signal every 50 seconds on a frequency of 406.025 MHz at 5 watts for at least 24 hours. The signal is received anywhere in the world by satellites in the Cospas-Sarsat satellite system. Two types of satellites, low earth orbiting satellites (LEOSATs) and geostationary satellites (GEOSATs), are used with different, complimentary capability. The signal is partially processed and stored in the satellites and then relayed to ground stations known as local user terminals (LUTs).

Further deciphering of a signal takes place at the LUTs, and appropriate search and rescue operations are notified through mission control centers (MCCs) set up for this purpose. Note: Maritime vessel emergency locating beacons (EPIRBs) and personal locator beacons (PLBs) use the exact same system. The United States portion of the Cospas-Sarsat system is 11-63 BRT OFF ON FWD TST CLR 25 200100 50 0 927 18 N A V M A P B R G V U E SHFT SYNC WX-10 3330 24 2I I5 I2 6 3 M G P S 1 3 6 0 ILX 310° 5.8 nm 310° NAV1 16.1 nm 337° 165 KT RNG 20 nm 310° S107 310° 3 MA34 KUTG ILX MD ARBLE FF22 AZT T53 +++++++++ +++ + overlaid in the form of green “plus” signs (right).

• METARs/TAFs/PIREPs/SIGMETs/NOTAMs • Hundreds of web-based graphical weather charts • Area forecasts and route weather briefings • Wind and temperature aloft data • “Plain language” passenger weather briefs • Route of flight images with weather overlays • Significant weather charts and other prognostic charts • Worldwide radar and satellite imagery Bern / Belp, CH (LSZB) Satellite weather services available METAR Daylight: Sunrise 06:03 AM. Sunset 08:50 PM LT Wind: 270 degrees (W) 9 knots (~10 MPH) Variable between 220 and 310 degrees Visibility: 6 or more miles Clouds: broken clouds at 5,500 feet Temperature: 59°F, dewpoint: 50°F, RH:72% Pressure: 30.15 inches Hg No significant changes Conditions at: 08:20 AM local time (9th)Conditions at: 08:20 AM local time (9th) VFR Updated at 02:43 PM Source:NWS the flight deck from a satellite weather service for aircraft followed by a list of various weather data that can be radioed to the flight deck from a satellite weather service.

maintained and operated by NOAA. Figure 11-148 illustrates the basic components in the Cospas-Sarsat system. ELTs are required to be installed in aircraft according to FAR 91.207. This encompasses most general aviation aircraft not operating under parts 135 or 121. ELTs must be inspected within 12 months of previous inspection for proper installation, battery corrosion, operation of the controls and crash sensor, and the presence of a sufficient signal at the antenna. Built-in test equipment facilitates testing without transmission of an emergency signal. The remainder of the inspection is visual. Technicians are cautioned to not activate the ELT and transmit an emergency distress signal. Inspection must be recorded in maintenance records including the new expiration date of the battery. This must also be recorded on the outside of the ELT.

ELTs are typically installed as far aft in the fuselage of an aircraft as is practicable just forward of the empennage. The built-in G-force sensor is aligned with the longitudinal axis of the aircraft. Helicopter ELTs may be located elsewhere on the airframe. They are equipped with multidirectional activation devices. Follow ELT and airframe manufacturer’s instructions for proper installation, inspection, and maintenance of all ELTs. Use of Doppler technology enables the origin of the 406 MHz ELT signal to be calculated within 2 to 5 kilometers. Second generation 406 MHz ELT digital signals are loaded with GPS location coordinates from a receiver inside the ELT unit or integrated from an outside unit. This reduces the location accuracy of the crash site to within 100 meters.

The digital signal is also loaded with unique registration information. It identifies the aircraft, the owner, and contact information, etc. When a signal is received, this is used to immediately research the validity of the alert to ensure it is a true emergency transmission so that rescue resources are not deployed needlessly. 11-64