VUELO INSTRUMENTAL (IFR) - INSTRUMENTAL FLIGHT RULES

Reglas de vuelo instrumental
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Las llamadas Reglas de Vuelo Instrumental o Reglas de Vuelo por Instrumentos (más conocidas por las siglas en inglés, IFR -Instrumental Flight Rules) son el conjunto de normas y procedimientos recogidos en el Reglamento de Circulación Aérea que regulan el vuelo de aeronaves con base en el uso de instrumentos para la navegación, lo cual implica que no es necesario tener contacto visual con el terreno, como ocurre en el método de navegación bajo Reglas de Vuelo Visual (o VFR -Visual Flight Rules).

* 1 Separación de aeronaves
* 2 El controlador de tráfico aéreo
* 3 Meteorología
* 4 Procedimientos
o 4.1 Salidas y llegadas instrumentales
o 4.2 Aproximaciones
+ 4.2.1 Aproximación de precisión
+ 4.2.2 Aproximación de no precisión
o 4.3 Rutas y aerovías
* 5 Habilitación instrumental
* 6 Véase también

[editar] Separación de aeronaves

Lo más importante del vuelo instrumental es que permite la operación continua de aeronaves en los momentos en que la capacidad del piloto para ver y evitar colisiones con otras naves u obstáculos está claramente reducida o es, incluso, imposible.

Para ello, se aplican ciertos criterios de separación entre aeronaves y con el terreno. De la primera es responsable el controlador aéreo, mientras que la segunda está recogida en las cartas de navegación aeronáutica. El controlador establece la separación entre aeronaves mediante el cálculo de tiempo, de las distancias y de las velocidades entre los mismos. Obtiene tales datos de dos modos: bien mediante la velocidad, la altura, el rumbo o la posición que le transmite el piloto, bien mediante la pantalla de radar, que obtiene esos mismos datos gracias a un emisor de radio en la aeronave llamado transpondedor.
[editar] El controlador de tráfico aéreo

Generalmente, el vuelo instrumental requiere la autorización del controlador para cada fase del vuelo. El controlador proporciona rumbo o aerovía, altitud y límite (el punto más lejano al que la aeronave puede volar antes de recibir una nueva autorización. En las áreas más sobrecargadas de tráfico es usual que también se reclamen estas autorizaciones a los vuelos visuales.

En espacio aéreo no controlado, las separaciones están establecidas mediante las Cartas de Navegación, que indican altitudes mínimas para evitar el terreno y los obstáculos, las altitudes de crucero para evitar la colisión de aeronaves que vuelen en direcciones distintas. Asimismo, en el espacio aéreo no controlado los pilotos deben informar de sus intenciones utilizando una frecuencia específica de radio, para mantener alerta a los otros pilotos. En España, el espacio aéreo por encima de los 24.500 pies sobre el nivel del mar se denomina Espacio Aéreo de Clase A, y está restringido a los vuelos instrumentales.
[editar] Meteorología

Una ventaja del vuelo instrumental es la capacidad de volar en Condiciones Meteorológicas Instrumentales (siglas en inglés: IMC), esto es, aquellas condiciones que no permiten el vuelo visual. En estas condiciones, el piloto controla su avión atendiendo a la lectura de los instrumentos de vuelo, y confía al controlador su separación respecto de otras aeronaves o el terreno (a pesar de que la mayoría de los aviones de línea y cada vez más aeronaves ligeras incorporan sus propios sistemas de alarma de proximidad al terreno (GPWS) y de colisión con otras aeronaves (TCAS).

De todos modos, es importante no confundir las Reglas de Vuelo Instrumental (IFR) con las Condiciones Meteorológicas Instrumentales (IMC). La mayor parte de los aviones comerciales operan conforme a las reglas de vuelo instrumental, incluso cuando las condiciones permiten el vuelo visual. Siempre y cuando la visibilidad lo permita, el piloto utiliza como referencia primaria la observación directa, incluso para evitar colisiones con otras naves, ya que en algunos casos (en áreas con cobertura de radar limitada), el controlador carece de información sobre los aviones en vuelo visual.

Habitualmente, el piloto navega usando los instrumentos de vuelo. En áreas con cobertura de radar puede recibir también vectores –esto es, diferentes rumbos y altitudes- del controlador. También deben existir unas condiciones mínimas de visibilidad para permitir la operación, que dependen de varios factores: la habilitación de la tripulación, el equipamiento de la aeronave (algunas de ellas permiten aterrizajes completamente a ciegas, gracias al sistema de aterrizaje autómatco ILS -Instrumental Landing System-), los vientos reinantes y las radioayudas existentes en las inmediaciones del aeropuerto.
[editar] Procedimientos

Un vuelo instrumental consta de cuatro etapas: la salida, la ruta, la llegada y la aproximación. Cada una de estas etapas cuenta con sus procedimientos estándar, publicados en las cartas de navegación aeronáutica y que permiten a los vuelos instrumentales moverse de un modo ordenado y seguro, desde que el avión enciende sus motores hasta que los apaga. Estos procedimientos también permiten al piloto, en caso de fallo de comunicaciones, completar un vuelo de modo que sus intenciones puedan predecirse, tanto por el controlador como por los aviones que puedan encontrarse en la zona.

Salidas y llegadas instrumentales

Las salidas están descritas en las «cartas de salida instrumental» (SID (Standard Instrument Departure )) y describen las rutas a seguir por la aeronave en función de su destino, desde el Aeropuerto hasta que se incorpora a la Aerovía asignada. Las «cartas de llegada instrumental» (STAR (Standard Terminal Arrival Route )), por su parte, detallan la ruta desde que el avión abandona la Aerovía hasta el punto donde inicia la aproximación final a la pista.

La función de ambos procedimientos es permitir las salidas y llegadas simultáneas en el área de control del aeropuerto sin riesgos de colisión. Las rutas de salida y llegada están claramente detalladas y se fijan a partir de las radioayudas existentes (fundamentalmente los llamados [[VOR - Vhf Omni Range]] y [[NDB - Non-Directional Beacon]]), de puntos referidos a distancias y rutas a partir de tales radioayudas, llamados fijos o intersecciones, y de otros puntos marcados mediante GPS.
Aproximaciones

La aproximación a pista se detalla en las llamadas «cartas de aproximación instrumental» (IAC), que describen la ruta, tanto vertical como horizontal, hasta un punto a partir del cual el piloto debe tener contacto visual con la pista y completar el vuelo sin ayuda de los instrumentos. Dicho punto se denomina mínimo, o Altitud de Decisión. Si en este punto el piloto no tiene contacto visual con la pista, deberá frustrar el aterrizaje, de acuerdo con los procedimientos establecidos en la misma carta, y esperar instrucciones del controlador o bien dirigirse a un aeropuerto alternativo especificado en su plan de vuelo.
[editar] Aproximación de precisión

Llamamos aproximación de precisión a aquélla en la que el aeropuerto dispone de radioayudas específicas, llamadas ILS, o Sistema de Aterrizaje por Instrumentos. Esta radioayuda proporciona al avión, en el tramo final, una guía horizontal y vertical que le permite dirigirse y descender de modo seguro hasta la pista de aterrizaje.

En las versiones más sofisticadas, este sistema permite al avión tomar tierra sin intervención del piloto.
[editar] Aproximación de no precisión

Las aproximaciones de no precisión se utilizan en aeropuertos o pistas no equipados con ILS. En estos casos, las cartas conducen a la aeronave hasta un punto más o menos cercano y más o menos alineado con la pista, de modo que el piloto completa el aterrizaje de forma visual.
[editar] Rutas y aerovías

Asimismo, las rutas también están ordenadas mediante las llamadas «cartas de ruta», que establecen aerovías por las que los aviones deben volar de forma obligada. Dependiendo de su rumbo, volaran en altitudes pares o impares, para evitar así colisiones. Las aerovías se componen de puntos de referencia.
[editar] Habilitación instrumental

No todos los pilotos, ni tampoco todas las aeronaves, pueden volar bajo las reglas de vuelo instrumental. Los pilotos requieren una licencia especial y, además, acreditar que han volado recientemente bajo estas condiciones.

Del mismo modo, las aeronaves deben disponer del siguiente equipamiento:

* Dos emisores/receptores de radio para comunicaciones con los controladores
* Dos receptores VOR para contactar con las radioayudas en tierra
* Al menos un receptor NDB para contactar con los radiofaros en tierra
* Y un equipo de medición de distancias (DME) para conocer las distancias con las radioayudas.
* En caso de estar certificado un Equipo GPS con las bases de datos correspondientes


*** FUENTE WIKIPEDIA


***ENGLISH

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"IFR" redirects here. For other uses, see IFR (disambiguation).

Instrument flight rules (IFR) are one of two sets of regulations governing all aspects of civil aviation aircraft operations; the other are visual flight rules (VFR).

Federal Aviation Regulations (FAR) defines IFR as: “Rules and regulations established by the FAA to govern flight under conditions in which flight by outside visual reference is not safe. IFR flight depends upon flying by reference to instruments in the flight deck, and navigation is accomplished by reference to electronic signals.[1]” It is also referred to as, “a term used by pilots and controllers to indicate the type of flight plan an aircraft is flying,” such as an IFR or VFR flight plan.[2]

* 1 Basic Information
o 1.1 Visual flight rules
o 1.2 Instrument flight rules
o 1.3 Confusing flight rules with weather conditions
* 2 Separation and clearance
* 3 Weather
* 4 Navigation
* 5 Procedures
* 6 Qualifications
* 7 References
* 8 External links
* 9 See also

[edit] Basic Information
[edit] Visual flight rules

To put instrument flight rules into context, a brief overview of VFR is necessary. Flights operating under VFR are flown solely by reference to outside visual cues, which permit navigation, orientation, and separation from terrain and other traffic. Thus, cloud ceiling and flight visibility are the most important variables for safe operations during all phases of flight.[3] The minimum weather conditions for ceiling and visibility for VFR flights are defined in FAR Part 91.155, and vary depending on the type of airspace in which the aircraft is operating, and on whether the flight is conducted during daytime or nighttime. However, typical daytime VFR minimums for most airspace is 3 statute miles of flight visibility and a cloud distance of 500' below, 1,000' above, and 2,000' feet horizontally.[4] Flight conditions reported as equal to or greater than these VFR minimums are referred to as visual meteorological conditions (VMC).

Visual flight rules are much more simplistic than IFR, and require significantly less training and practice. VFR provides a great degree of freedom, allowing pilots to go where they want, when they want, and how to get there.[5] Pilots are not required to file a flight plan, do not have to communicate with ATC (unless flying in certain types of "busier" airspace), and are not limited to following predefined published routes or flight procedures.

VFR pilots may use cockpit instruments as secondary aids to navigation and orientation, but are not required to. Instead, the view outside of the aircraft is the primary source for keeping the aircraft straight and level (orientation), flying where you intended to fly (navigation), and for not hitting anything (separation).[6]
[edit] Instrument flight rules

Instrument flight rules permit an aircraft to operate in instrument meteorological conditions (IMC), which have much lower weather minimums than VFR. Procedures and training are significantly more complex as a pilot must demonstrate competency in conducting an entire cross-country flight in IMC conditions, while controlling the aircraft solely by reference to instruments.[7]

As compared to VFR flight, instrument pilots must meticulously evaluate weather, create a very detailed flight plan based around specific instrument departure, en route, and arrival procedures, and dispatch the flight. Once airborne, the IFR pilot is then challenged to fly the aircraft in the same air traffic control (ATC) environment and weather systems that two-crew jet aircraft are using at the same time.[6][8]
[edit] Confusing flight rules with weather conditions

It is essential to differentiate between flight plan type (IFR or VFR) and weather conditions (VMC or IMC). While current and forecasted weather may be a factor in deciding which type of flight plan to file, weather conditions themselves do not affect your filed flight plan. For example, an IFR flight that encounters VMC en route does not automatically change to a VFR flight, and the flight must still follow all IFR procedures regardless of VMC or IMC.
[edit] Separation and clearance

The distance by which an aircraft avoids obstacles or other aircraft is termed separation. The most important concept of IFR flying is that separation is maintained regardless of weather conditions. In controlled airspace, Air Traffic Control (ATC) separates IFR aircraft from obstacles and other aircraft using a flight clearance based on route, time, distance, speed, and altitude. ATC monitors IFR flights on radar, or through aircraft position reports in areas where radar coverage is not available. Aircraft position reports are sent as voice radio transmissions. Aircraft position reports are not necessary if ATC reports that the aircraft is in radar contact. In the United States, a flight operating under IFR is required to provide position reports unless ATC advises a pilot that the plane is in radar contact. The pilot must resume position reports after ATC advises that radar contact has been lost, or that radar services are terminated.

IFR flights in controlled airspace require an ATC clearance for each part of the flight. A clearance always specifies a clearance limit, which is the farthest the aircraft can fly without a new clearance. In addition, a clearance typically provides a heading or route to follow, altitude, and communication parameters, such as frequencies and transponder codes.

In uncontrolled airspace, ATC clearances are unavailable. In some states a form of separation is provided to certain aircraft in uncontrolled airspace as far as is practical (often known under ICAO as an advisory service in class F airspace), but separation is not mandated nor widely provided.

Despite the protection offered by flight in controlled airspace under IFR, the ultimate responsibility for the safety of the aircraft rests with the pilot in command, who can refuse clearances.
[edit] Weather
Above clouds, but still IFR

The main purpose of IFR is the safe operation of aircraft in Instrument Meteorological Conditions (IMC). The weather is considered to be IMC when it does not meet the minimum requirements for Visual Meteorological Conditions (VMC). To operate safely in IMC, a pilot controls the aircraft relying on flight instruments, and ATC provides separation.[9]

It is important not to confuse IFR with IMC. A significant amount of IFR flying is conducted in Visual Meteorological Conditions (VMC). Any time a flight is operating in VMC, the crew is responsible for seeing and avoiding other traffic; however, since the flight is conducted under Instrument Flight Rules, ATC still provides separation services.

During flight under IFR, there are no visibility requirements, so flying through clouds is permitted. There are still minimum conditions that must be present in order for the aircraft to take off and land; these will vary according to the kind of operation, the type of navigation aids available, the location and height of terrain and obstructions in the vicinity of the airport, equipment on the aircraft, and the qualifications of the crew. For example, landing at mountain airports such as Reno (KRNO) offer significantly different instrument approaches for aircraft landing on the same runway, but from opposite directions. Aircraft approaching from the north must make visual contact with the airport at a higher altitude than a flight approaching from the south, because of rapidly rising terrain south of the airport.{FAA approach plate AL 346} This higher altitude allows a flight crew to clear the obstacle if a landing is not feasible.

Although large airliners and, increasingly, smaller aircraft now carry their own terrain awareness and warning system TAWS,[citation needed] these are primarily backup systems providing a last layer of defense if a sequence of errors or omissions causes a dangerous situation.[citation needed]
[edit] Navigation

Under IFR, the primary means of navigation are either via radio beacons on the ground, such as VORs and NDBs, or GPS. In areas of radar coverage, ATC may also assign headings to IFR aircraft, also known as radar vectors. Radar vectors are one of several methods which ATC uses to provide separation between aircraft for landing, especially in busy traffic environments; in less congested airspace, aircraft are increasingly responsible for their own traffic awareness and collision avoidance.[citation needed]

Modern Flight Management Systems have evolved sufficiently to allow a crew to plan a flight not only as to route and altitude, but to specific time of arrival at specific locations.[citation needed] This capability is used in several trial projects experimenting with four dimensional approach clearances for commercial aircraft, with time as the fourth dimension.[citation needed] These clearances allow ATC to optimize the arrival of aircraft at major airports, which increases airport capacity, and uses less fuel providing monetary and environmental benefits to airlines and the public at large respectively.[citation needed]

* Required Navigation Performance (RNP)
* ADS-B

[edit] Procedures
Main article: Flight procedure

Specific procedures allow IFR aircraft to transition safely through every stage of flight. These procedures specify how an IFR pilot should respond, even in the event of a complete radio failure, and loss of communications with ATC, including the expected aircraft course and altitude.

Here is an example of an IFR clearance, for a Cessna aircraft traveling from Palo Alto airport (KPAO) to Stockton airport (KSCK).
"Cessna 21756, cleared to Stockton Airport via turn right heading zero-six-zero within one mile of the airport. Radar Vectors San Jose, then as filed. Maintain 3,000 expect 5,000 five minutes after departure. Departure frequency is 121.3, squawk 4263."

Detailed explanation:

"Cessna 21756"
Verifies that only this specific aircraft is cleared.

"is cleared to Stockton Airport."
Clearance Limit: the farthest destination the aircraft is allowed to go under IFR (in most cases it is the destination airport).

"via turn right heading zero-six-zero within one mile of the airport."
The pilot is expected to execute the right turn to 060° without further ATC prompting within one mile of the departure airport.

"Radar Vectors San Jose"
The departure controller will provide directional guidance to the San Jose VOR.

"Then as filed."
After arriving at the San Jose VOR, the pilot will likely resume navigation without ATC prompts along the airways and intersections that were filed in their flight plan.

"Maintain 3,000 ..."
After takeoff, climb to an altitude of 3000 feet above sea level.

"... expect 5,000 five minutes after departure."
Your final altitude assignment is probably going to be 5000 feet above sea level. However, you must follow actual ATC altitude assignments throughout the flight. This portion of the clearance provides a backup if communications are lost, allowing you to proceed to climb and maintain 5000 feet.

"Departure frequency is 121.3, ..."
Contact with NORCAL Departure on the specified communication frequency, after Palo Alto Tower tells you to switch.

"... squawk 4263."
Program your transponder to 4263 so that ATC can positively identify you on radar.

Departures are described in an IFR clearance issued by ATC prior to takeoff. The departure clearance may contain an assigned heading, one or more waypoints, and an initial altitude to fly. The clearance can also specify a departure procedure (DP), or standard instrument departure (SID) that should be followed unless "NO DP" is specified in the notes section of the filed flight plan.

En route flight is described by IFR charts showing navigation aids, fixes, and standard routes called airways. Aircraft with appropriate navigational equipment such as GPS, are also often cleared for a direct-to routing, where only the destination, or a few navigational waypoints are used to describe the route that the flight will follow. ATC will assign altitudes in its initial clearance or amendments thereto, and navigational charts indicate minimum safe altitudes for airways.

The approach portion of an IFR flight may begin with a Standard Terminal Arrival Route (STAR), describing common routes to fly to arrive at an initial approach fix (IAF) from which an instrument approach commences. Instrument approaches are categorized as precision and non-precision. Despite the names, a precision approach simply indicates that vertical guidance (as well as lateral guidance) is being used. Non-precision indicates only lateral guidance.

In either case, an instrument approach will terminate either in the pilot(s) acquiring sufficient visual reference to carry out a normal landing, or in a missed approach if the required visual reference is not encountered in time. The point at which the crew of an aircraft has to make a decision to either proceed visually, or "miss" the approach is called either the Decision Altitude (DA) or Decision Height (DH) for precision approaches, and missed approach point (MAP) for non-precision approaches. During precision approaches the altitude of the aircraft is determined by the navigational instruments. For non-precision approaches the crew will descend to specific altitudes during the approach procedure, with the final altitude termed the Minimum Descent Altitude (MDA).

Some commercial aircraft are equipped with automatic landing systems that allow the aircraft to land without transitioning from instruments to visual conditions for a normal landing. Such autoland operations require specialized equipment, procedures and training, and involve the aircraft, airport, and the crew. Autoland is the only way some major airports such as Paris-Charles de Gaulle Airport remain operational every day of the year. Some modern aircraft are equipped with enhanced vision systems based on infrared sensors, that provide a day-like visual environment and allow operations in conditions and at airports that would otherwise not be suitable for a landing. Commercial aircraft also frequently use such equipment for takeoffs when takeoff minima are not met.[10]

Documents describing the approach procedure are frequently called approach plates in reference to the plate-like appearance of single-page sheet that it is printed on.

An instrument approach that terminates in a missed approach will continue using missed approach procedure information shown on the approach plate. Typically it describes a transition to a nearby navigational fix, from which the instrument approach can be attempted again. In practice an approach that terminates in a missed approach rarely flies the missed approach procedure as published. Instead, ATC will assign headings and altitudes that will assimilate the aircraft into the arriving traffic for a repeated approach attempt. The crew may also request an alternate destination, either a previously stated alternate airport, or other suitable airport considering the prevailing weather conditions.
[edit] Qualifications

To fly under IFR, a pilot must have an instrument rating, and must meet currency of experience requirements. In the United States, these currency of experience requirements include six instrument approaches, NAVAID intercepting and tracking, and holding procedures in the past six calendar months. The aircraft must also be equipped and type-certified for instrument flight, and the related navigational equipment must have been inspected within a specific period of time prior to the instrument flight.

The UK differs in its pilot-licensing practice from the U.S. In the UK any pilot can decide to which flight rules he adheres provided that the meteorological conditions for those rules are met. The pilot does need an instrument rating to fly in instrument meteorological conditions and under IFR in controlled airspace. The upshot of this is that non-instrument-qualified pilots can elect to fly under IFR in visual meteorological conditions outside controlled airspace. Compared to the rest of the world, the UK's flight crew licensing regime is somewhat unusual in its licensing for meteorological conditions and airspace, rather than flight rules. As a partial alternative to the instrument rating, the UK issues an "IMC rating", the privileges of which include flight under IFR in controlled (classes D and E) airspace and flight outside controlled airspace in instrument meteorological conditions.

In the United States, instruments required for IFR flight are those that are required for VFR flight in addition to: Heading indicator, Sensitive Altimeter adjustable for Barometric Pressure, Clock with a sweep-second pointer or digital equivalent, Attitude indicator, Radios and suitable Avionics for the route to be flown, Alternator or generator, gyroscopic rate of turn indicator that is either a Turn coordinator or the Turn and bank indicator.[11]