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Static wicks, also called static dischargers or static discharge wicks, are devices used to remove
Static dischargers were first proposed in a patent application by Howard Dudley Blanchard in 1920. At this time most aircraft were constructed from cloth and wood, and rigid body airships were widely used. Therefore, a method of gradually discharging static accumulation was necessary since static discharge on these craft could cause serious damage and start fires. Static discharge is the likely cause of the Hindenburg disaster.
The first static wicks were developed by a joint Army-Navy team led by Dr. Ross Gunn of the Naval Research Laboratory and fitted onto military aircraft during World War II. They were shown to be effective even in
static electricity
Static electricity is an imbalance of electric charges within or on the surface of a material. The charge remains until it can move away by an electric current or electrical discharge. The word "static" is used to differentiate it from electric ...
from aircraft in flight. They take the form of small sticks pointing backwards from the wings, and are fitted on almost all civilian aircraft.
Function
Precipitation static is an electrical charge on an airplane caused by flying through rain, snow storms, ice, or dust particles. Charge also accumulates through friction between the aircraft hull and the air. When the aircraft charge is great enough, it discharges into the surrounding air. Without static dischargers, the charge discharges in large batches through pointed aircraft extremities, such as antennas, wing tips, vertical and horizontal stabilizers, and other protrusions. The discharge creates a broad-band radio frequencynoise
Noise is sound, chiefly unwanted, unintentional, or harmful sound considered unpleasant, loud, or disruptive to mental or hearing faculties. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrat ...
from DC to 1000 MHz, which can affect aircraft communication.
To control this discharge, so as to allow the continuous operation of navigation and radio communication systems, static wicks are installed on the trailing edges of aircraft. These include (electrically grounded) aileron
An aileron (French for "little wing" or "fin") is a hinged flight control surface usually forming part of the trailing edge of each wing of a fixed-wing aircraft. Ailerons are used in pairs to control the aircraft in roll (or movement aroun ...
s, elevators
An elevator (American English) or lift (English in the Commonwealth of Nations, Commonwealth English) is a machine that vertically transports people or freight between levels. They are typically powered by electric motors that drive tracti ...
, rudder
A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, airship, or other vehicle that moves through a fluid medium (usually air or water). On an airplane, the rudder is used primarily to counter adverse yaw ...
, wing
A wing is a type of fin that produces both Lift (force), lift and drag while moving through air. Wings are defined by two shape characteristics, an airfoil section and a planform (aeronautics), planform. Wing efficiency is expressed as lift-to-d ...
, horizontal and vertical stabilizer tips. Static wicks are high electrical resistance
The electrical resistance of an object is a measure of its opposition to the flow of electric current. Its reciprocal quantity is , measuring the ease with which an electric current passes. Electrical resistance shares some conceptual paral ...
(6–200 megaohm) devices with a lower corona voltage and sharper points than the surrounding aircraft structure. This means that the corona discharge into the atmosphere flows through them, and occurs gradually.
Static wicks are not lightning arresters and do not affect the likelihood of an aircraft being struck by lightning. They will not function if they are not properly bonded to the aircraft. There must be a conductive path from all parts of the airplane to the dischargers, otherwise they will be useless. Access panels, doors, cowls, navigation lights, antenna mounting hardware, control surfaces, etc., can create static noise if they cannot discharge through the static wick.
History
Static dischargers were first proposed in a patent application by Howard Dudley Blanchard in 1920. At this time most aircraft were constructed from cloth and wood, and rigid body airships were widely used. Therefore, a method of gradually discharging static accumulation was necessary since static discharge on these craft could cause serious damage and start fires. Static discharge is the likely cause of the Hindenburg disaster.
The first static wicks were developed by a joint Army-Navy team led by Dr. Ross Gunn of the Naval Research Laboratory and fitted onto military aircraft during World War II. They were shown to be effective even in extreme weather
Extreme weather includes unexpected, unusual, severe weather, severe, or unseasonal weather; weather at the extremes of the historical distribution—the range that has been seen in the past. Extreme events are based on a location's recorded weat ...
conditions in 1946 by a United States Army Air Corps
The United States Army Air Corps (USAAC) was the aerial warfare service component of the United States Army between 1926 and 1941. After World War I, as early aviation became an increasingly important part of modern warfare, a philosophical ri ...
team led by Capt. Ernest Lynn Cleveland.
Dayton Granger, an inventor from Florida, received a patent on static wicks in 1950.
See also
* Pan Am Flight 214 *Precipitation (meteorology)
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, rain and snow mixed ("sleet" in Commonwealth ...
*Electrostatic discharge
Electrostatic discharge (ESD) is a sudden and momentary flow of electric current between two differently-charged objects when brought close together or when the dielectric between them breaks down, often creating a visible electric spark, spark as ...
*Triboelectric effect
The triboelectric effect (also known as triboelectricity, triboelectric charging, triboelectrification, or tribocharging) describes electric charge transfer between two objects when they contact or slide against each other. It can occur with d ...
* Ground loop (electricity)
References
{{Reflist Electrical engineering Electrodes