Visual Flight rule (VFR)
Visual Flight rule are a set of regulations under which a pilot operates an aircraft in weather conditions generally clear enough to allow the pilot see where the aircraft is going.

In order for this to happen the weather must be:

  •  Able to operate the aircraft with visual reference to the ground.
  • Better than basic Visual Flight Rule (VFR) weather minima i.e. in visual meteorological condition (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.

One should note that, if the weather is below Visual Meteorological Conditions, pilots are required to use instrument flight rules and operation of the aircraft will primarily be through referencing the instruments rather than visual reference.
Visual flight rule requires a pilot to see outside the cockpit in order to control the aircraft’s attitude, navigate and avoid obstacles and other aircraft.

Instrument Flight Rules (IFR)
Instrument flight rules is one of two sets of regulations governing all aspects of civil aviation aircraft operations. According to Federal Aviation Administration, IFR are rules and regulations established by the FAA to govern flight under conditions in which flight by outside visual reference is not safe. Instrument flight rules flight is dependent upon flying reference to instruments in the flight deck while navigation is acquired by reference to electronic signals.

Differences.
Visual flight rules are far much simpler than instrument flight rules hence need less training and practice. VFR provides a great degree of freedom which allows pilots to go where they want, whenever they want thus allowing them a much wider latitude in determining how to get there.
On the other hand, when operation of an aircraft under VFR is not safe because the visual cues outside the aircraft are concealed by weather or darkness, instrument flight rule is used instead. IFR allows an aircraft to operate in instrument meteorological conditions which is essentially any weather condition less than VMC but in which aircraft can still operate safely.

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Airspace is the portion of atmosphere controlled by a country above its territory, including its territorial waters. It is also defined as the space lying above the earth or above a certain area of land or water.

There are two kinds of airspace which include: Uncontrolled and Controlled airspace.

Uncontrolled Airspace
In the past, all airspace was uncontrolled, when there were a few airplanes that had no instruments necessary to fly in clouds. Even in the busiest airports, traffic density was very low and airplanes flew slowly. Although there we no conditions that aircraft could fly in, it was agreed upon that if one remained clear of clouds and had at least one-mile visibility you could see other airplanes and terrain in time to avoid a collision. This was known as see and avoid.
Controlled Airspace
Having invented inexpensive gyroscopic flight instruments, travel through the clouds became possible thus see and avoid became useless. Procedures to ensure aircraft separation were needed hence this led to the creation of air traffic control (ATC) and controlled airspace.

There are different classifications of airspace i.e. A, B, C, D, E airspace.

Class A
This is airspace from 18,000 feet mean sea level, flight level 600 and airspace overlying the waters within 12 nautical miles of the coast of the 48 contiguous states and Alaska. All operation in Class A airspace is conducted under instrument flight rules unless authorized otherwise.

Class B
This is airspace from the surface to 10,000 feet MSL surrounding the nation’s busiest airports in terms of airport operations or passenger enplanements. Class b airspace is designed to contain all published instrument procedures once an aircraft enters the airspace. Air traffic control clearance is required for all aircraft to operate in the area and all aircraft that are so cleared receive separation within the airspace.

Class C
This is airspace from the surface to 4,000 feet above the airport elevation surrounding those airports that have an operation control tower, are serviced by a radar approach control and have a certain number of IFR operations or passenger enplanements. Each aircraft must establish two-way radio communications with the ATC facility providing air traffic services prior to entering the airspace and thereafter must maintain those communications while within the airspace.

Class D
This is airspace from the surface to 2,500 feet above the airport elevation surrounding those airports that have an operational control tower. The layout of each Class D airspace area is individually tailored and when instrument procedures are published the airspace is normally designed to contain the procedures. Each aircraft must establish two-way radio communications with the ATC facility providing air traffic services prior to entering the airspace and thereafter maintain those communications while in the airspace unless otherwise.

Class E
Class E airspace is the controlled airspace not classified as class A, B, C and D.
Special Use of airspace
It is the designation for airspace in which certain activities must be confined. Special use airspace consists of: Prohibited, restricted, warning, military operation, alert and controlled firing areas.

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