Critical area
Encyclopedia

Aviation

In aviation
Aviation
Aviation is the design, development, production, operation, and use of aircraft, especially heavier-than-air aircraft. Aviation is derived from avis, the Latin word for bird.-History:...

, a critical area refers to a designated area of an airport
Airport
An airport is a location where aircraft such as fixed-wing aircraft, helicopters, and blimps take off and land. Aircraft may be stored or maintained at an airport...

 that all aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...

 must remain clear of when another aircraft is inbound on an ILS
Instrument Landing System
An instrument landing system is a ground-based instrument approach system that provides precision guidance to an aircraft approaching and landing on a runway, using a combination of radio signals and, in many cases, high-intensity lighting arrays to enable a safe landing during instrument...

 approach. The critical area should be avoided when the weather is less than or equal to 2 miles visibility or less than or equal to 800 ft. ceilings. These areas are used to protect against signal interference
Interference (communication)
In communications and electronics, especially in telecommunications, interference is anything which alters, modifies, or disrupts a signal as it travels along a channel between a source and a receiver. The term typically refers to the addition of unwanted signals to a useful signal...

 that may lead to navigation
Navigation
Navigation is the process of monitoring and controlling the movement of a craft or vehicle from one place to another. It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks...

al errors, or worse.

ILS
Instrument Landing System
An instrument landing system is a ground-based instrument approach system that provides precision guidance to an aircraft approaching and landing on a runway, using a combination of radio signals and, in many cases, high-intensity lighting arrays to enable a safe landing during instrument...

 technology delivers two main types of information to pilots. These types include the glideslope (vertical location relative to the designed glide path) and the localizer (lateral position relative to the designed approach course). Each type of information is broadcast using a separate antenna array and each type has a specific critical area.
Localizer critical area - Vehicles and aircraft are not authorized in or over the critical area when an arriving aircraft is between the ILS
Instrument Landing System
An instrument landing system is a ground-based instrument approach system that provides precision guidance to an aircraft approaching and landing on a runway, using a combination of radio signals and, in many cases, high-intensity lighting arrays to enable a safe landing during instrument...

 final approach fix and the airport.

Glideslope critical area - Vehicles and aircraft are not authorized in or over the critical area when an arriving aircraft is between the ILS
Instrument Landing System
An instrument landing system is a ground-based instrument approach system that provides precision guidance to an aircraft approaching and landing on a runway, using a combination of radio signals and, in many cases, high-intensity lighting arrays to enable a safe landing during instrument...

 final approach fix and the airport unless the aircraft has reported the airport in sight and is circling or sidestepping to land on a runway other than the ILS runway.

For practical purposes, these two areas are combined into the ILS critical area and identified by signs and pavement markings.

During times of reduced ceilings and visibility (800 ft / 2 miles) or during ILS Autoland (coupled) approaches pilots are expected to:

BEFORE TAKEOFF - Stop aircraft before entering the critical area while waiting for takeoff.

AFTER LANDING - Move the aircraft out of the critical area before stopping to receive taxi instructions from the ground controller.

Much larger than the critical area is the sensitive area. Aircraft and vehicles are not allowed in this area when Low Visibility Procedures are in force, since aircraft will be making autolands and therefore the accuracy of the guidance signals provided by the ILS is absolutely critical.

Integrated Circuits

In integrated circuit
Integrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...

 design
Design for manufacturability (IC)
Achieving high-yielding designs in the state of the art, VLSI technology has become an extremely challenging task due to the miniaturization as well as the complexity of leading-edge products...

, a critical area refers to the area of a circuit design wherein a particle of a particular size can cause a failure. It measures the sensitivity of the circuit to a reduction in yield.
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