Aeronautical Terms beginning with O

Obstacle Clearance Surface (OCS)

An inclined or level surface associated with a defined area for obstruction evaluation.


Obstacle Departure Procedure (ODP)

A procedure that provides obstacle clearance. ODPs do not include ATC related climb requirements. In fact, the primary emphasis of ODP design is to use the least onerous route of flight to the en route structure while attempting to accommodate typical departure routes.


Obstacle Identification Surface (OIS)

The design of a departure procedure is based on TERPS, a living document that is updated frequently. Departure design criteria assumes an initial climb of 200 feet per NM after crossing the departure end of the runway (DER) at a height of at least 35 feet above the ground. Assuming a 200 feet per NM climb, the departure is structured to provide at least 48 feet per NM of clearance above objects that do not penetrate the obstacle slope. The slope, known as the obstacle identification slope (OIS), is based on a 40 to 1 ratio, which is the equivalent of a 152-foot per NM slope.


Off-Airway Routes

The FAA prescribes altitudes governing the operation of aircraft under IFR for off airway routes in a similar manner to those on federal airways, jet routes, area navigation low or high altitude routes, and other direct routes for which an MEA is designated.


Off-Route Obstruction Clearance Altitude (OROCA)

An off-route altitude that provides obstruction clearance with a 1,000 foot buffer in non-mountainous terrain areas and a 2,000 foot buffer in designated mountainous areas within the U.S. This altitude may not provide signal coverage from ground based navigational aids, air traffic control radar, or communications coverage.


Operations Specifications (OpsSpecs)

A published document providing the conditions under which an air carrier and operator for compensation or hire must operate in order to retain approval from the FAA.


Octane

The rating system of aviation gasoline with regard to its anti-detonating qualities.


Overboost

A condition in which a reciprocating engine has exceeded the maximum manifold pressure allowed by the manufacturer. Can cause damage to engine components.


Overspeed

A condition in which an engine has produced more r.p.m. than the manufacturer recommends, or a condition in which the actual engine speed is higher than the desired engine speed as set on the propeller control.


Overtemp

A condition in which a device has reached a temperature above that approved by the manufacturer or any exhaust temperature that exceeds the maximum allowable for a given operating condition or time limit. Can cause internal damage to an engine.


Overtorque

A condition in which an engine has produced more torque (power) than the manufacturer recommends, or a condition in a turboprop or turboshaft engine where the engine power has exceeded the maximum allowable for a given operating condition or time limit. Can cause internal damage to an engine.


Obstacle departure procedures (ODP)

Obstacle clearance protection provided to aircraft in instrument meteorological conditions (IMC).


Omission error

The failure to anticipate significant instrument indications following attitude changes; for example, concentrating on pitch control while forgetting about heading or roll information, resulting in erratic control of heading and bank.


Optical illusion

A misleading visual image. For the purpose of this handbook, the term refers to the brains misinterpretation of features on the ground associated with landing, which causes a pilot to misread the spatial relationships between the aircraft and the runway.


Orientation

Awareness of the position of the aircraft and of oneself in relation to a specific reference point.


Otolith organ

An inner ear organ that detects linear acceleration and gravity orientation.


Outer marker

A marker beacon at or near the glide slope intercept altitude of an ILS approach. It is normally located four to seven miles from the runway threshold on the extended centerline of the runway.


Overcontrolling

Using more movement in the control column than is necessary to achieve the desired pitch-and bank condition.


Overpower

To use more power than required for the purpose of achieving a faster rate of airspeed change.


Objectivity

The singleness of scoring of a test; it does not reflect the biases of the person grading the test.


Overhead question

In the guided discussion method, a question directed to the entire group in order to stimulate thought and discussion from the entire group. An overhead question may be used by an instructor as the lead-off question.


Operate

With respect to aircraft, use, cause to use or authorize to use aircraft, for the purpose (except as provided in §91.13 of this chapter) of air navigation including the piloting of aircraft, with or without the right of legal control (as owner, lessee, or otherwise).


Operational control

With respect to a flight, the exercise of authority over initiating, conducting or terminating a flight.


Overseas air commerce

The carriage by aircraft of persons or property for compensation or hire, or the carriage of mail by aircraft, or the operation or navigation of aircraft in the conduct or furtherance of a business or vocation, in commerce between a place in any State of the United States, or the District of Columbia, and any place in a territory or possession of the United States; or between a place in a territory or possession of the United States, and a place in any other territory or possession of the United States.


Overseas air transportation

The carriage by aircraft of persons or property as a common carrier for compensation or hire, or the carriage of mail by aircraft, in commerce:
(1) Between a place in a State or the District of Columbia and a place in a possession of the United States; or
(2) Between a place in a possession of the United States and a place in another possession of the United States; whether that commerce moves wholly by aircraft or partly by aircraft and partly by other forms of transportation.


Over-the-top

Above the layer of clouds or other obscuring phenomena forming the ceiling.


Obscuration

Denotes sky hidden by surface-based. obscuring phenomena and vertical visibility restricted overhead.


Obscuring phenomena

Any hydrometeor or lithometeor other than clouds; may be surface based or aloft.


Occlusion

Same as occluded front—a composite of two fronts as a cold front overtakes a warm front or quasi-stationary front. (commonly called occlusion or frontal occlusion).


Occluded front

A composite of two fronts as a cold front overtakes a warm front or quasi-stationary front. (commonly called occlusion or frontal occlusion).


Orographic

Of, pertaining to, or caused by mountains as in orographic clouds, orographic lift, or orographic precipitation.


Ozone

An unstable form of oxygen; heaviest concentrations are in the stratosphere; corrosive to some metals; absorbs most ultraviolet solar radiation.


Obstacle departure procedures (ODP)

A preplanned instrument flight rule (IFR) departure procedure printed for pilot use in textual or graphic form to provide obstruction clearance via the least onerous route from the terminal area to the appropriate en route structure. ODPs are recommended for obstruction clearance and may be flown without ATC clearance unless an alternate departure procedure (SID or radar vector) has been specifically assigned by ATC.


Obstruction lights

Lights that can be found both on and off an airport to identify obstructions.


Occluded front

A frontal occlusion occurs when a fast-moving cold front catches up with a slow moving warm front. The difference in temperature within each frontal system is a major factor in determining whether a cold or warm front occlusion occurs.


Omission error

The failure to anticipate significant instrument indications following attitude changes; for example, concentrating on pitch control while forgetting about heading or roll information, resulting in erratic control of heading and bank.


Optical illusion

A misleading visual image. For the purpose of this handbook, the term refers to the brain’s misinterpretation of features on the ground associated with landing, which causes a pilot to misread the spatial relationships between the aircraft and the runway.


Orientation

Awareness of the position of the aircraft and of oneself in relation to a specific reference point.


Otolith organ

An inner ear organ that detects linear acceleration and gravity orientation.


Outer marker

A marker beacon at or near the glideslope intercept altitude of an ILS approach. It is normally located four to seven miles from the runway threshold on the extended centerline of the runway.


Outside air temperature (OAT)

The measured or indicated air temperature (IAT) corrected for compression and friction heating. Also referred to as true air temperature.


Overcontrolling

Using more movement in the control column than is necessary to achieve the desired pitch-and-bank condition.


Overboost

A condition in which a reciprocating engine has exceeded the maximum manifold pressure allowed by the manufacturer. Can cause damage to engine components.


Overpower

To use more power than required for the purpose of achieving a faster rate of airspeed change.


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