aviation Aviation includes the activities surrounding mechanical flight and the aircraft industry. ''Aircraft'' includes fixed-wing and rotary-wing types, morphable wings, wing-less lifting bodies, as well as lighter-than-air craft such as hot a ...

, vertical navigation (VNAV, usually pronounced ''vee-nav'') is

glidepath Instrument landing system glide path, commonly referred to as a glide path (G/P) or glide slope (G/S), is "a system of vertical guidance embodied in the instrument landing system which indicates the vertical deviation of the aircraft from its o ...

information provided during an

instrument approach In aviation, an instrument approach or instrument approach procedure (IAP) is a series of predetermined maneuvers for the orderly transfer of an aircraft operating under instrument flight rules from the beginning of the initial approach to a landi ...

, independently of ground-based

navigation aid Navigation is a field of study that focuses on the process of monitoring and controlling the movement of a craft or vehicle from one place to another.Bowditch, 2003:799. The field of navigation includes four general categories: land navigation, ...

s. An onboard navigation system displays a constant rate descent path to minimums. The VNAV path is computed using aircraft performance, approach constraints, weather data, and aircraft weight. The approach path is computed from the top of descent point to the end of descent waypoint, which is typically the runway or

missed approach point Missed approach point (MAP or MAPt) is the point prescribed in each instrument approach at which a missed approach procedure shall be executed if the required visual reference does not exist. It defines the point for both precision and non-precis ...

Overview

flight management system A flight management system (FMS) is a fundamental component of a modern airliner's avionics. An FMS is a specialized computer system that automates a wide variety of in-flight tasks, reducing the workload on the flight crew to the point that mode ...

(FMS) uses either a performance or a geometric VNAV path. The performance path is computed from the top of the descent to the first constrained

waypoint A waypoint is an intermediate point or place on a route or line of travel, a stopping point or point at which course is changed, the first use of the term tracing to 1880. In modern terms, it most often refers to coordinates which specify one's posi ...

, using idle or near idle power. This is referred to as an idle descent path at ECON speed. The geometric path is shallower descent and typically not at idle. The geometric path uses an assigned vertical angle or the computed point to point path between constrained waypoints.

RNAV Area navigation (RNAV, usually pronounced as "''ar-nav"'') is a method of instrument flight rules (IFR) navigation that allows an aircraft to choose any course within a network of navigation beacons, rather than navigate directly to and from t ...

approaches combine VNAV navigation equipment with

LNAV In aviation, lateral navigation (LNAV, usually pronounced ''el-nav'') is azimuth navigation, without vertical navigation (VNAV). Area navigation (RNAV) approach plates include LNAV as a non-precision instrument approach (NPA). When combined with V ...

navigation equipment to provide both lateral and vertical approach guidance. Vertical guidance comes from

WAAS The Wide Area Augmentation System (WAAS) is an air navigation aid developed by the Federal Aviation Administration to augment the Global Positioning System (GPS), with the goal of improving its accuracy, integrity, and availability. Essentia ...

GPS or a barometric VNAV (Baro-VNAV) system. The FMS provides flight control steering and thrust guidance along the VNAV path. VNAV information on an

approach plate Approach plates (or, more formally, instrument approach procedure charts) are the printed charts of instrument approach procedures that pilots use to fly instrument approaches during instrument flight rules (IFR) operations. Each country maintains ...

includes the

Final Approach Fix In aeronautics, the final approach (also called the final leg and final approach leg) is the last leg in an aircraft's approach to landing, when the aircraft is lined up with the runway and descending for landing.Crane, Dale: ''Dictionary of ...

(FAF), the FAF crossing altitude, a Vertical Descent Angle (VDA), the landing runway threshold as a second fix, the Threshold Crossing Height (TCH), and perhaps a Visual Descent Point (VDP). A pilot uses the VDA, and

ground speed Ground speed is the horizontal speed of an aircraft relative to the Earth’s surface. It is vital for accurate navigation that the pilot has an estimate of the ground speed that will be achieved during each leg of a flight. An aircraft diving ve ...

, to compute a

rate of descent In aeronautics, the rate of climb (RoC) is an aircraft's vertical speed, that is the positive or negative rate of altitude change with respect to time. In most ICAO member countries, even in otherwise metric countries, this is usually expressed ...

(from a table found in the U.S. Terminal Procedures Publication), which is flown using the

Vertical velocity indicator In aviation, a variometer – also known as a rate of climb and descent indicator (RCDI), rate-of-climb indicator, vertical speed indicator (VSI), or vertical velocity indicator (VVI) – is one of the flight instruments in an aircraft used to in ...

. Aircraft approved for LNAV/VNAV minimums include the

Boeing 737NG The Boeing 737 Next Generation, commonly abbreviated as 737NG, or 737 Next Gen, is a narrow-body aircraft powered by two jet engines and produced by Boeing Commercial Airplanes. Launched in 1993 as the third generation derivative of the Boeing ...

, 767,

777 777 may refer to: * 777 (number), a number * AD 777, a year of the Julian calendar * 777 BC, a year in the 8th century BC * Boeing 777, a commercial jet airliner :* Boeing 777X, the newer generation of the Boeing 777. Art and entertainment Alb ...

, the

Airbus A300 The Airbus A300 is a wide-body airliner developed and manufactured by Airbus. In September 1967, aircraft manufacturers in the United Kingdom, France, and West Germany signed a memorandum of understanding to develop a large airliner. West ...

and some

ATR ATR may refer to: Medicine * Acute transfusion reaction * Ataxia telangiectasia and Rad3 related, a protein involved in DNA damage repair Science and mathematics * Advanced Test Reactor, nuclear research reactor at the Idaho National Laboratory, ...

Baro-VNAV

A Baro-VNAV is an RNAV system which uses the aircraft altimeter to compute and display a vertical guidance path. The path is either geometric between two waypoints, or based on an angle from a single waypoint. Baro-VNAV procedures include a minimum and maximum temperature limitation. Otherwise, temperature compensations must be used.

References

External links

*{{cite web, url=http://www.ae.gatech.edu/people/jpclarke/cda/workshop2/presentations/Miller.pdf, title=Flight Management Computer System Vertical Navigation aka VNAV, author= Sam Miller, date= April 2006, access-date=2015-10-18, archive-url=https://web.archive.org/web/20110718205016/http://www.ae.gatech.edu/people/jpclarke/cda/workshop2/presentations/Miller.pdf, archive-date=2011-07-18 Air navigation