Flight plan

Flight plans are plans filed by pilots with the local Aviation Authority (e.g. FAA in the USA) prior to flying. They generally include basic information such as departure and arrival points, estimated time, alternate airports in case of bad weather, type of flight whether instrument flight rules or visual flight rules, pilot's name and number of passengers. Flight plans are required for flights under IFR. Under VFR, they are optional unless crossing national borders, however they 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.

Routing Types

Aircraft routing types used in flight planning are: Airway, Navaid and Direct. A route may be composed of segments of different routing type. For example, a route from Chicago to Rome may include Airway routing over the U.S. and Europe, but Direct routing over the Atlantic Ocean.

Airway routing occurs along pre-defined pathways called Airways. Airways can be thought of as three-dimensional highways for aircraft. In most land areas of the world, aircraft are required to fly airways between the departure and destination airports. The rules governing airway routing cover altitude, airspeed, and requirements for entering and leaving the airway (see #SIDs and STARs). Most airways are eight nautical miles (14 kilometers) wide, and the airway flight levels keep aircraft separated by at least 1000 vertical feet from aircraft on the flight level above and below. Airways usually intersect at Navaids, which designate the allowed points for changing from one airway to another. Airways have names consisting of one or more letters followed by one or more digits (e.g., V484 or UA419).

The airway structure is divided into high and low altitudes. The low altitude airways in the U.S. which can be navigated using VOR Navaids have names that start with the letter V, and are therefore called Victor Airways. They cover altitudes from approximately 1200 feet above ground level (AGL) to 18,000 feet (5,486 meters) above mean sea level (MSL). The high altitude airways in the U.S. all have names that start with the letter J, and are called Jet Routes. These run from 18,000 feet to 35,000 feet (5,486 meters to 10,668 meters). The altitude separating the low and high airway structures varies from country to country. For example, it is 19,500 feet in Switzerland, and 25,500 feet in Egypt.

Navaid routing occurs between Navaids (short for Navigational Aids, see VOR) which are not always connected by airways. Navaid routing is typically only allowed in the continental U.S. If a flight plan specifies Navaid routing between two Navaids which are connected via an airway, the rules for that particular airway must be followed as if the aircraft was flying Airway routing between those two Navaids. Allowable altitudes are covered in Flight Levels.

Direct routing occurs when one or both of the route segment endpoints are at a latitude/longitude which is not located at a Navaid. Some flight planning organizations specify that checkpoints generated for a Direct route be a limited distance apart, or limited by time to fly between the checkpoints (i.e., Direct checkpoints could be farther apart for a fast aircraft than for a slow one).

SIDs and STARs

SIDs and STARs are procedures and checkpoints used to enter and leave the airway system. There is a defined transition point at which an airway and a SID or STAR intersect.

A SID, or Standard Instrument Departure, defines a pathway out of an airport and onto the airway structure. A SID is sometimes called a Departure Procedure (DP). SIDs are unique to the associated airport.

A STAR, or Standard Terminal Arrival Route, defines a pathway into an airport from the airway structure. STARs can be associated with more than one arrival airport, which can occur when two or more airports are in close proximity (e.g., San Francisco and San Jose).

Special Use Airspace

In general, flight planners are expected to avoid areas called Special Use Airspace (SUA) when planning a flight. In the United States, there are several types of SUA, including Restricted, Warning, Prohibited, Alert, and Military Operation Area. Examples of Special Use Airspace include a region around the White House in Washington, D.C., and the country of Cuba. Government and military aircraft may have different requirements for particular SUA areas, or may be able to acquire special clearances to traverse through these areas.

Flight Levels

Flight Levels are used to specify aircraft cruising altitude and are abbreviated in 100s of feet above mean sea level. For example, 29000 feet is FL290 and 25500 feet is FL255. Flight levels are an important part of flight planning, assuring a safe vertical separation of aircraft.

Airways have a set of associated standardized flight levels (sometimes called the “flight model”) which must be used when on the airway. On a bi-directional airway, each direction has its own set of flight levels. A valid flight plan must include a legal flight level at which the aircraft will traverse the airway. Due to differences in flight levels on different airways, a change in airway may include a required altitude change to stay at an acceptable flight level.

In the U.S., eastbound (heading 0-179 degrees) IFR flights must use “odd” flight levels in 2000 foot increments starting at FL190 (i.e., FL190, FL210, FL230, etc.); Westbound (heading 180-359 degrees) flights must use “even” flight levels in 2000 foot increments starting at FL180 (i.e., FL180, FL200, FL220, etc.).

Large aircraft flying a long distance may plan on altitude changes to a higher flight level, primarily to save fuel. For example, due to a heavy fuel load, an aircraft may be able to reach FL350 early in a flight, but move to FL370 later in the route after weight has decreased due to fuel burn off.

Alternate Airports

Part of flight planning often involves the identification of one or more airports which can be flown to in case of unexpected conditions (such as weather) at the destination airport. The planning process must be careful to include only alternate airports which can be reached with the anticipated fuel load and total aircraft weight and that have capabilities necessary to handle the type of aircraft being flown.

Fuel

Aircraft manufacturers are responsible for generating flight performance data which flight planners use to estimate fuel needs for a particular flight. The fuel burn rate is based on specific throttle settings for climbing and cruising. The planner uses the projected weather and aircraft weight as inputs to the flight performance data to estimate the necessary fuel to reach the destination. The fuel burn is usually given in pounds of fuel instead of volume (such as gallons) because aircraft weight is critical.

In addition to standard fuel needs, some organizations require that a flight plan include reserve fuel if certain conditions are met. For example, an over-water flight of longer than a specific duration may require the flight plan to include reserve fuel. The reserve fuel may be planned as extra which is left over on the aircraft at the destination, or it may be assumed to be burned during flight (perhaps due to unaccounted for differences between the actual aircraft and the flight performance data).

Other Flight Planning Considerations

Holding over the destination or alternate airports is a required part of some flight plans. Holding (circling in a pattern designated by the airport control tower) may be necessary if unexpected weather or congestion occurs at the airport. If the flight plan calls for hold planning, the additional fuel and hold time should appear on the flight plan.

Organized Tracks are a series of paths similar to airways which cross ocean areas. Some organized track systems are fixed and appear on navigational charts (e.g., the NOPAC tracks over the Northern Pacific Ocean). Others change on a daily basis depending on weather and other factors and therefore cannot appear on printed charts (e.g., the NAT tracks over the North Atlantic Ocean).

Description of Flight Plan Blocks

1. Type: Type of flight plan. Flights may be VFR, IFR, DVFR, or a combination of types, termed composite.
2. Aircraft Identification: The registration of the aircraft, usually the flight or tail number.
3. Aircraft Type/Special Equipment: The type of aircraft and how it's equipped. For example, a Mitsubishi Mu-2 equipped with an altitude reporting transponder and GPS would use MU2/G. Equipment codes may be found in the FAA Airman's Information Manual.
4. True airspeed in knots: The planned cruise true airspeed of the aircraft in knots.
5. Departure Point: Usually the identifier of the airport from which the aircraft is departing.
6. Departure Time: Proposed and actual times of departure. Times are Universal Time Coordinated.
7. Crusing Altitude: The planned cruising altitude or flight level.
8. Route: Proposed route of flight. The route can be made up of airways, intersections, navaids, or possibly direct.
9. Destination: Point of intended landing. Typically the identifier of the destination airport.
10. Estimated Time Enroute: Planned elapsed time between departure and arrival at the destination.
11. Remarks: Any information the PIC believes is necessary to be provided to ATC. One common remark is "NO SIDS/STARS", which means the PIC is unable or unwilling to accept a SID or STAR on an IFR flight.
12. Fuel on Board: The amount of fuel on board the aircraft, in hours and minutes of flight time.
13. Alternate Airports: Airports of intended landing as an alternate of the destination airport. May be required for an IFR flight plan if poor weather is forecast at the planned destination.
14. Pilot's Information: Contact information of the pilot for search and rescue purposes.
15. Number Onboard: Total number of people on board the aircraft.
16. Color of Aircraft: The color helps identify the aircraft to search and rescue personnel.
17. Contact Information at Destination: Having a means of contacting the pilot is useful for tracking down an aircraft that has failed to close its flight plan and is possibly overdue or in distress.

Some Terms and Acronyms Used in Flight Planning

Above Ground Level (AGL) : A measurement of altitude above a specific land mass (also see MSL).

International Civil Aviation Organization (ICAO) : The ICAO is the specialized agency of the United Nations with a mandate “to ensure the safe, efficient and orderly evolution of international civil aviation.” The standards which become accepted by the ICAO member nations “cover all technical and operational aspects of international civil aviation, such as safety, personnel licensing, operation of aircraft, aerodromes, air traffic services, accident investigation and the environment.” A simple example of ICAO responsibilities is the unique worldwide names used to identify Navaids, Airways, airports and countries.

Knot (Kt) : A unit of speed used in navigation equal to one nautical mile per hour.

Mean Sea Level (MSL) : The average height of the surface of the sea for all stages of tide; used as a reference for elevations (also see AGL).

Nautical Mile (NM) : A unit of distance used in aviation equal to approximately one minute of arc of latitude. It is defined to be 1852 metres exactly, or approximately 1.15 statute mile.

References

Aviation terminology

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