In
general aviation
General aviation (GA) is defined by the International Civil Aviation Organization (ICAO) as all civil aviation aircraft operations with the exception of commercial air transport or aerial work, which is defined as specialized aviation service ...
, scud running is a practice in which
pilots
An aircraft pilot or aviator is a person who controls the flight of an aircraft by operating its directional flight controls. Some other aircrew members, such as navigators or flight engineers, are also considered aviators, because they ar ...
lower their altitude to avoid clouds or
instrument meteorological conditions
In aviation, instrument meteorological conditions (IMC) is a flight category that describes weather conditions that require pilots to fly primarily by reference to instruments, and therefore under instrument flight rules (IFR), rather than by ou ...
(IMC). The goal of scud running is to stay clear of weather to continue flying with visual, rather than instrument, references. This practice is widely accepted to be dangerous, and has led to death in many cases from pilots flying into terrain or obstacles, such as masts and towers, normally referred to as controlled flight into terrain, or
CFIT
In aviation, a controlled flight into terrain (CFIT; usually ) is an accident in which an airworthy aircraft, under pilot control, is unintentionally flown into the ground, a mountain, a body of water or an obstacle. In a typical CFIT scenario ...
; however, even instrument-rated pilots sometimes elect to take the risk to avoid icing or embedded thunderstorms in cloud, or in situations where the minimum instrument altitudes are too high for their aircraft.
Scud running is occasionally described as "maintaining visual contact with the ground while avoiding physical contact with it" or "if the weather's too bad to go IFR, we'll go VFR."
[FAA AC60-22 "Aeronautical Decision Making"] A procedure under instrument flight rules (IFR), called a
contact approach
A contact approach is an approach available to aircraft operating on an instrument flight rules (IFR) flight plan, where the pilot may deviate from the published instrument approach procedure (IAP) and proceed to the destination airport by visual ...
, is often referred to as a form of "legalized" scud running.
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The term gets its name from
scud
A Scud missile is one of a series of tactical ballistic missiles developed by the Soviet Union during the Cold War. It was exported widely to both Second and Third World countries. The term comes from the NATO reporting name attached to the mis ...
, which is used to describe small, ragged, low cloud fragments that are unattached to a larger cloud base, and often seen with and behind cold fronts and thunderstorm gust fronts.
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Canadian regulations
In Canada, the visibility and altitude requirements are similar to those in the U.S., but most controlled airspace outside of terminal areas bottoms out at
Above Ground Level
In aviation, atmospheric sciences and broadcasting, a height above ground level (AGL or HAGL) is a height measured with respect to the underlying ground surface. This is as opposed to height above mean sea level (AMSL or HAMSL), height above ell ...
(AGL), so there is more room to scud run legally. In northern Canada, there is little controlled airspace at all, below the high-level class A airspace.
US regulations
In the United States, most
controlled airspace
Controlled airspace is airspace of defined dimensions within which air traffic control (ATC) services are provided. The level of control varies with different classes of airspace. Controlled airspace usually imposes higher weather minimums tha ...
below
MSL requires a pilot flying under
VFR to remain below a cloud ceiling and to maintain visibility. However, outside of airport control zones and major terminal areas, controlled airspace typically begins at above ground level; below that is uncontrolled (class G) airspace, where (at that altitude) a pilot is required only to remain clear of clouds and to maintain visibility.
References
External links
Scud Running – Discussing a Delicate Subject
{{DEFAULTSORT:Scud Running
Air traffic control