ATC (Air traffic control)

Air traffic control

Air traffic control (ATC) is a service provided by ground-based controllers who direct aircraft on the ground and in the air. The primary purpose of ATC systems worldwide is to separate aircraft to prevent collisions, to organize and expedite the flow of traffic, and to provide information and other support for pilots when able. In some countries, ATC may also play a security or defense role (as in the United States), or be run entirely by the military (as in Brazil).

Preventing collisions is referred to as separation, which is a term used to prevent aircraft from coming too close to each other by use of lateral, vertical and longitudinal separation minima; many aircraft now have collision avoidance systems installed to act as a backup to ATC observation and instructions. In addition to its primary function, the ATC can provide additional services such as providing information to pilots, weather and navigation information and NOTAMs (Notices to Airmen).

In many countries, ATC services are provided throughout the majority of airspace, and its services are available to all users (private, military, and commercial). When controllers are responsible for separating some or all aircraft, such airspace is called "controlled airspace" in contrast to "uncontrolled airspace" where aircraft may fly without the use of the air traffic control system. Depending on the type of flight and the class of airspace, ATC may issue instructions that pilots are required to follow, or merely flight information (in some countries known as advisories) to assist pilots operating in the airspace. In all cases, however, the pilot in command has final responsibility for the safety of the flight, and may deviate from ATC instructions in an emergency.

Although native language for the region is normally used, English language must be used if requested, as required by the International Civil Aviation Organization (ICAO.)^[1]

Read more : http://en.wikipedia.org/wiki/Air_traffic_control

GPS (GLOBAL POSITIONING SYSTEM)

GENERAL INFORMATION ON GPS

The Global Positioning System (GPS) was designed as a dual-use system with the primary purpose of enhancing the effectiveness of U.S. and allied military forces. GPS is rapidly becoming an integral component of the emerging Global Information Infrastructure, with applications ranging from mapping and surveying to international air traffic management and global change research. The growing demand from military, civil, commercial, and scientific users has generated a U.S. commercial GPS equipment and service industry that leads the world. Augmentations to enhance basic GPS services could further expand these civil and commercial markets.

GPS is managed by the National Space-Based Positioning, Navigation, and Timing (PNT) Executive Committee, supported by the PNT Executive Secretariat (http://www.pnt.gov). The PNT manages GPS and U.S. Government augmentations to GPS, consistent with national policy, to support and enhance U.S. economic competitiveness and productivity while protecting national security and foreign policy interests.

The basic GPS is defined as the constellation of satellites, the navigation payloads which produce the GPS signals, ground stations, data links, and associated command and control facilities which are operated and maintained by the Department of Defense; the Standard Positioning Service (SPS) as the civil and commercial service provided by the basic GPS; and augmentations as those systems based on the GPS that provide real-time accuracy greater than the SPS. GPS permits land, sea, and airborne users to determine their three dimensional position, velocity, and time, 24 hours a day in all weather, anywhere in the world.

From our site, you may view or download current and archived GPS satellite information such as status messages, precise ephemeris data, and almanacs.

Specific, operational GPS information may be obtained from the links below or from the links on blue navigation bar at the left.

Read more : http://www.navcen.uscg.gov/gps/default.htm

TCAS (Traffic Collision Avoidance System)

Traffic Collision Avoidance System

TCAS and IVSI Indicator

The Traffic alert and Collision Avoidance System (or TCAS) is an aircraft collision avoidance system designed to reduce the incidence of mid-air collisions between aircraft. It monitors the airspace around an aircraft for other aircraft equipped with a corresponding active transponder, independent of air traffic control, and warns pilots of the presence of other transponder-equipped aircraft which may present a threat of mid-air collision (MAC). It is an implementation of the Airborne Collision Avoidance System mandated by International Civil Aviation Organization to be fitted to all aircraft with MTOM (maximum take-off mass) over 5700 kg or authorised to carry more than 19 passengers.

Official definition from PANS-ATM (Nov 2007): ACAS / TCAS is an aircraft system based on secondary surveillance radar (SSR) transponder signals which operates independently of ground-based equipment to provide advice to the pilot on potential conflicting aircraft that are equipped with SSR transponders.

In modern glass cockpit aircraft, the TCAS display may be integrated in the Navigation Display (ND); in older glass cockpit aircraft and those with mechanical instrumentation, such an integrated TCAS display may replace the mechanical Instantaneous Vertical Speed Indicator (which indicates the rate with which the aircraft is descending or climbing).

Read more : http://en.wikipedia.org/wiki/TCAS

FMC (Flight Management Computer)

Introduction

First introduced on the series 200 in Feb 1979 as the Performance Data Computer System (PDCS), the Flight Management Computer (FMC) was a huge technological step forward. Smiths Industries (formerly Lear Seigler) has supplied all FMCs installed on the 737.

The PDCS was developed jointly by Boeing and Lear Seigler in the late 1970's. It enabled EPR and ASI bugs to be set by the computer and advise on the optimum flight level, all for best fuel economy. It was trialed on two in-service aircraft, a Continental 727-200 and a Lufthansa 737-200 for nine months in 1978 with regular line crews and a flight data observer. The 737-200 showed average fuel savings of 2.95% with a 2 minute increase in trip time over an average 71 minute flight. The 727 gave a 3.94% fuel saving because of its longer sector lengths. The PDCS quickly became standard fit and many were also retrofitted. By 1982 the autothrottle had been devised and thrust levers could be automatically driven to the values specified by the PDCS.

The true FMC was introduced with the 737-300 in 1984 this kept the performance database and functions but also added a navigation database which interacts with the autopilot & flight director, autothrottle and IRSs. The integrated system is known as the Flight Management System (FMS) of which the FMC is just one component. Most aircraft have just one FMC, but there is an option to have two this is usually only taken by operators into MNPS airspace eg Oceanic areas. The FMS can be defined as being capable of four dimensional area navigation (latitude, longitude, altitude & time) while optimising performance to achieve the most economical flight possible.

The photograph above is of the Control Display Unit (CDU), which is the pilot interface to the FMC. There are normally 2 CDUs but only one FMC. Think of it as having two keyboards connected to the one PC. The CDU in the photograph has a DIR INTC key at the beginning of the second row but some have a MENU key. This key gives access to the subsystems such as FMC, ACARS, DFDMU, etc.

In its most basic form, the FMC has a 96k word navigation database, where one word is two bytes (ie a 16 bit processor). This was increased to 192k words in 1988, 288k in 1990, 1 million in 1992 and is now at 4 Mega words for the 737-NG with Update 10.7. The navigation database is used to store route information which the autopilot will fly when in LNAV mode. When given data such as ZFW & MACTOW, it takes inputs from the fuel summation unit to give a gross weight and best speeds for climb, cruise, descent, holding, approach, driftdown etc. These speeds can all be flown directly by the autopilot & autothrottle in VNAV mode. It will also compute the aircrafts position based upon inputs from the IRSs, GPS and radio position updating.

The latest FMC – Model 2907C1, has a Motorola 68040 processor running at 60MHz (30Mhz bus clock speed), with 4Mb static RAM and 32Mb for program & database.

Read more : http://www.b737.org.uk/fmc.htm

ILS approaches

What does "ILS" stand for?

Instrument Landing System.

What is an ILS?

In a nutshell, it is an instrument approach that gives the pilot of an aircraft visual cues on the aircraft's instruments. If the pilot follows these cues he will arrive near the approach end of the runway, usually 200 feet above the surface.

How does the ILS differ from the other types of approaches?

Generally speaking, it is the most accurate of the approaches that is available to the average civilian pilot, and allows you to descend to lower minimums. The word "minimums" refers to height (above the ground), and visibility.

The ILS offers both horizontal and vertical guidance information, whereas the VOR and NDB approaches offer horizontal (lateral) guidance only. Because it offers vertical guidance, the ILS is in the category of a "Precision Approach".

What equipment do I need in my airplane to fly the ILS?

You will need a VOR head, with glideslope display, or an HSI (Horizontal Situation Indicator). "Glass cockpits" replace these instruments with a variety of displays on CRT's (Cathode Ray Tubes). Because of the variety of displays, glass cockpits will not be referenced in this tutorial. However, the procedures remain the same. In addition, you will need a Marker Beacon receiver to indicate passage over the ground components of the ILS. An ADF or RMI, while extremely handy for orientation, is not required.

OK. what surface equipment "makes" an ILS?

1. Localizer: This is the component that provides the "left/right" guidance. Think of it as the VOR needle if you will, just more sensitive.

2. Glide Slope: This is the component that provides the "up/down" guidance. Think of it as a VOR needle laying on it's side. And, like the Localizer, it is more sensitive than the VOR display.

3. Outer Marker: This guy is in line with the Localizer's extended center line across the ground. It is normally located four to seven miles from the threshold of the runway. It transmits a signal on 75 MHz with a 400 Hz tone timed at two dashes per second. In addition to this audio tone, a blue light on the Matker Beacon receiver will flash in rhythm with the audio tone.

4. Middle Marker: Like the Outer Marker, located on an extended center line from the runway. It is normally located at the Decision Height (Missed Approach Point), on the approach, usually .5 to .8 miles from the runway threshold.

5. Approach Lights: These are the guys that John Wayne saw when he broke out on the approach into San Francisco in the movie "The High and The Mighty", along to the strains of a large orchestra. They are designed to help the pilot transition from the cockpit displays to outside visual reference for the landing. There are a various ways these are displayed. Each type has a designation, such as "ALSF-1", "ALSF-2", "SSALR", "MALSR", and so on. Suffice it to say that the "approach lights" that you see on the approach are approved by the appropriate governing authorities to do the job.

Just a second here. How do you "tune" the Marker Beacons? I don't see any radios for that purpose

Well, you can't tune them- so there! Here's the deal. All Marker Beacons transmit on the same frequency, 75 MHz. The Outer and the Middle Beacons differ in the audio tone that they emit. The Marker Beacon receiver in the aircraft is tuned to this set frequency, you as the pilot can't do any more about it. You can turn the audio off, and on some receivers you can adjust the "sensitivity" from "low" to "high". The lights associated with the Outer and Middle Markers will flash automatically. So, why aren't you bombarded with these "whistles and bells" as you fly across the country? Because they are low-powered, and once you are several thousand feet above the ground the Marker Beacon receiver will not capture the signals.

Read more : http://stoenworks.com/Tutorials/ILS Approaches.html

VOR Navigation

The VHF Omnidirectional Range navigation system, VOR, was probably the most significant aviation invention other than the jet engine. With it, a pilot can simply, accurately, and without ambiguity navigate from Point A to Point B.

The widespread introduction of VORs began in the early 1950s and 50 years later it remains the primary navigation system in the overwhelming majority of aircraft.

If you jumped to this point of the website without proceeding through the earlier sections, I strongly recommend that you return to the Air Navigation section and review the sections on VFR Sectional Charts, IFR enroute low altitude charts, and the basics of plotting a course. Further, you should go to the NDB Approaches/Approach Plates section and read the basics of Instrument Approach Plates, now called Terminal Procedures.

The basic principle of operation of the VOR is very simple: the VOR facility transmits two signals at the same time. One signal is constant in all directions, while the other is rotated about the station. The airborne equipment receives both signals, looks (electronically) at the difference between the two signals, and interprets the result as a radial from the station.

The GPS, Global Positioning System, is making inroads onto the navigation scene and offers a flexibility unavailable with either NDB or VOR systems. However, it is supplementing these systems, not replacing them.

The RMI indicator used in the NDB navigation exercises is as close to a "hands-off" indicator as you will find. In an aircraft the RMI compass card must initially be aligned with the compass before a flight begins and then rechecked every fifteen minutes or so, and that's it.

With VOR, however, course information must be manually entered into the indicator. The VOR indicator below shows an aircraft heading toward, "TO," the Omni station.

NOTE this very important fact, with more info farther down. The radial signals of a VOR always point away from the station. The indicator below shows 345°, but since we are heading toward the VOR, see arrow D, we are actually on the reciprocal radial, or the 165° radial. This aircraft is south of the station. This will become more clear in a moment.

Read More : http://www.navfltsm.addr.com/vor-nav.htm