In aviation, instrument flight rules (IFR) is one of two sets of regulations governing all aspects of civil aviation aircraft operations; the other is visual flight rules (VFR).
In aviation, visual flight rules (VFR) are a set of regulations under which a pilot operates an aircraft in weather conditions generally clear enough to allow the pilot to see where the aircraft is going. Specifically, the weather must be better than basic VFR weather minima, i.e., in visual meteorological conditions (VMC), as specified in the rules of the relevant aviation authority. The pilot must be able to operate the aircraft with visual reference to the ground, and by visually avoiding obstructions and other aircraft.
Air traffic control (ATC) is a service provided by ground-based air traffic controllers who direct aircraft on the ground and through a given section of controlled airspace, and can provide advisory services to aircraft in non-controlled airspace. The primary purpose of ATC worldwide is to prevent collisions, organize and expedite the flow of air traffic, and provide information and other support for pilots.
The Federal Aviation Regulations (FARs) are rules prescribed by the Federal Aviation Administration (FAA) governing all aviation activities in the United States. The FARs comprise Title 14 of the Code of Federal Regulations. A wide variety of activities are regulated, such as aircraft design and maintenance, typical airline flights, pilot training activities, hot-air ballooning, lighter-than-air aircraft, man-made structure heights, obstruction lighting and marking, model rocket launches, commercial space operations, model aircraft operations, Unmanned Aircraft Systems (UAS) and kite flying. The rules are designed to promote safe aviation, protecting pilots, flight attendants, passengers and the general public from unnecessary risk.
In aviation, uncontrolled airspace is airspace in which an Air Traffic Control (ATC) service is not deemed necessary or cannot be provided for practical reasons. It is the opposite of controlled airspace. It is that portion of the airspace that has not been designated as Control Area, Control Zone, Terminal Control Area or Transition Area.
Airspace is the portion of the atmosphere controlled by a country above its territory, including its territorial waters or, more generally, any specific three-dimensional portion of the atmosphere. It is not the same as outer space which is the expanse or space outside the Earth and aerospace which is the general term for Earth's atmosphere and the outer space within the planet's vicinity.
In aviation, visual meteorological conditions (VMC) is an aviation flight category in which visual flight rules (VFR) flight is permitted—that is, conditions in which pilots have sufficient visibility to fly the aircraft maintaining visual separation from terrain and other aircraft. They are the opposite of instrument meteorological conditions (IMC). The boundary criteria between IMC and VMC are known as the VMC minima and are defined by: visibility, cloud ceilings, and cloud clearances.
Flight plans are documents filed by a pilot or flight dispatcher with the local Air Navigation Service Provider prior to departure which indicate the plane's planned route or flight path. Flight plan format is specified in ICAO Doc 4444. They generally include basic information such as departure and arrival points, estimated time en route, alternate airports in case of bad weather, type of flight, the pilot's information, number of people on board, and information about the aircraft itself. In most countries, flight plans are required for flights under IFR, but may be optional for flying VFR unless crossing international borders. Flight plans are highly recommended, especially when flying over inhospitable areas such as water, as they provide a way of alerting rescuers if the flight is overdue. In the United States and Canada, when an aircraft is crossing the Air Defense Identification Zone (ADIZ), either an IFR or a special type of VFR flight plan called a DVFR flight plan must be filed. For IFR flights, flight plans are used by air traffic control to initiate tracking and routing services. For VFR flights, their only purpose is to provide needed information should search and rescue operations be required, or for use by air traffic control when flying in a "Special Flight Rules Area."
The world's navigable airspace is divided into three-dimensional segments, each of which is assigned to a specific class. Most nations adhere to the classification specified by the International Civil Aviation Organization (ICAO) and described below, though they might use only some of the classes defined below, and significantly alter the exact rules and requirements. Similarly, individual nations may also designate special use airspace (SUA) with further rules for reasons of national security or safety.
In aviation, instrument meteorological conditions (IMC) are weather conditions that require pilots to fly primarily by reference to flight instruments, and therefore under instrument flight rules (IFR), as opposed to flying by outside visual references under visual flight rules (VFR). Typically, this means flying in cloud or poor weather, where little or nothing can be seen or recognised when looking out of the window. Simulated IMC can be achieved for training purposes by wearing view-limiting devices, which restrict outside vision and force the trainee to rely on instrument indications only.
Special visual flight rules are a set of aviation regulations under which a pilot may operate an aircraft. It is a special case of operating under visual flight rules (VFR).
In air traffic control, an area control center (ACC), also known as a center or en-route center, is a facility responsible for controlling aircraft flying in the airspace of a given flight information region (FIR) at high altitudes between airport approaches and departures. In the US, such a center is referred to as an air route traffic control center (ARTCC).
Allegheny Airlines Flight 853 was a regularly scheduled Allegheny Airlines flight from Boston, Massachusetts, to St. Louis, Missouri, with stops in Baltimore, Maryland, Cincinnati, Ohio, and Indianapolis, Indiana. On September 9, 1969, the aircraft serving the flight, a McDonnell Douglas DC-9, collided in mid-air with a Piper PA-28 light aircraft near Fairland, Indiana. The DC-9 was carrying 78 passengers and 4 crew members, and the Piper was leased to a student pilot on a solo cross-country flight. All 83 occupants of both aircraft were killed in the accident and both aircraft were destroyed.
In aviation, a non-towered airport is an airport without a control tower, or air traffic control (ATC) unit. The vast majority of the world's airports are non-towered. In the United States, there are close to 20,000 non-towered airports compared to approximately 500 airports with control towers. Airports with a control tower without 24/7 ATC service follow non-towered airport procedures when the tower is closed but the airport remains open, for example at night.
Special use airspace (SUA) is a type of special airspaces in the United States designated for operations of a nature such that limitations may be imposed on aircraft not participating in those operations. Often these operations are of a military nature. The designation of SUAs identifies for other users the areas where such activity occurs, provides for segregation of that activity from other users, and allows charting to keep airspace users informed of potential hazards.
A transponder is an electronic device that produces a response when it receives a radio-frequency interrogation. Aircraft have transponders to assist in identifying them on air traffic control radar. Collision avoidance systems have been developed to use transponder transmissions as a means of detecting aircraft at risk of colliding with each other.
The United States airspace system's classification scheme is intended to maximize pilot flexibility within acceptable levels of risk appropriate to the type of operation and traffic density within that class of airspace – in particular to provide separation and active control in areas of dense or high-speed flight operations.
The Grand Canyon mid-air collision occurred in the western United States on June 30, 1956, when a United Airlines Douglas DC-7 struck a Trans World Airlines Lockheed L-1049 Super Constellation over Grand Canyon National Park, Arizona. The first one fell into a canyon and the other one slammed into a rock face. All 128 on board both airplanes perished, making it the first commercial airline incident to exceed one hundred fatalities. The airplanes had departed Los Angeles International Airport minutes apart from each other and headed for Chicago and Kansas City, respectively. The collision took place in uncontrolled airspace, where it was the pilots' responsibility to maintain separation. This highlighted the antiquated state of air traffic control, which became the focus of major aviation reforms.
Military training routes are aerial corridors across the United States in which military aircraft can operate below 10,000 feet faster than the maximum safe speed of 250 knots that all other aircraft are restricted to while operating below 10,000 feet. The routes are the result of a joint venture between the Federal Aviation Administration and the Department of Defense to provide for high-speed, low-altitude military activities.
A contact approach is an approach available to aircraft operating on an instrument flight rules (IFR) flight plan, where the pilot may deviate from the published instrument approach procedure (IAP) and proceed to the destination airport by visual reference to the surface. It is similar to a visual approach, except that the pilot is not required to have the destination airport nor the preceding aircraft in sight at all times during the approach, and the visibility requirements are less stringent.
