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Aviation Glossary

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Above Ground Level (AGL) Actual height above the surface of the earth, either land or water.
Affiliated Aircraft Civil aircraft operated in accordance with 14 CFR 91, 121, or 135 for the mutual benefit of DOI and the affiliated party at no cost to DOI.
Agreement Aircraft An OAS-approved aircraft that is available for Intermittent, short-term use under an OAS Basic Ordering Agreement (BOA). Orders for use of agreement aircraft are subject to the small purchase limitation established under the Federal Acquisition Regulations unless otherwise authorized by the Contracting Officer.
Aircraft The term "aircraft" is used to refer to both airplanes and helicopters.
Aircraft Accident An occurrence associated with the operation of an aircraft which takes place between the time any person boards the aircraft with the intention of flight and all such persons have disembarked, and in which any person suffers death or serious injury, or in which the aircraft receives substantial damage.
Aircraft Acquisition Obtaining an aircraft through either purchase or transfer (excess), or through lease, rental or loan, the operating cost of which can reasonably be expected to exceed $25,000 per year. (Any aircraft secured on a fully vendor operated basis is specifically excluded from this definition.)
Aircraft Incident An occurrence other than an accident, associated with the operation of an aircraft, which affects or could affect the safety of operations.
Air Crewmember Essential for the Mission An objective determination is made by the first line supervisor that an additional crewmember is required to be on board the aircraft to ensure the successful outcome of the mission. (Example: loadmaster accompanying bulk fuel).
Airspace Conflict A near mid-air collision, intrusion, or violation of airspace rules.
Airtanker An aircraft used for the dispensing of a substance (normally fire retardant or water) on a wildfire.
Aileron Control surfaces on the trailing edge of the wing. Ailerons on each side of the airplane deflect in opposite directions to control the roll, or bank, of the aircraft. Movement of the ailerons is controlled by either the control yoke or side stick. A trim system minimizes the force needed to hold the ailerons in the proper position for various flight conditions.
Airworthiness A term used to describe both the legal and mechanical status of an aircraft with regard to its readiness for flight.
Altimeter A pressure-sensing instrument that displays the altitude of an aircraft above the mean sea level (MSL).
Altimeter Setting The barometric pressure setting used to adjust a pressure altimeter for variations in existing atmospheric pressure and temperature.
Altitude The height expressed in units of distance above a reference plane, usually above mean sea level or above ground level.
Attitude An aircraft's position in relation to the horizon (i.e., whether the aircraft is flying level, nose up, nose down, or banking left or right).
Aviation Hazard Any condition, act, or set of circumstances associated with aviation operations that exposes the Department to the risk of personnel injury, material damage, or mission degradation.
Avionics The computers and other electronic systems that monitor and control an aircraft's electrical and mechanical systems.
Azimuth The direction or angle between the radar site and an aircraft; measured clockwise from north in a horizontal plane.
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Bearing The horizontal direction to or from any point, usually measured clockwise from true north (true bearing) magnetic north (magnetic bearing), or some other reference point, through 360°.
Bureau A level of government defined by bureaus, services, surveys, and offices within the Department of the Interior.
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Ceiling The height above the earth's surface of the lowest layer of clouds or obscuring phenomena that is reported as broken, overcast or obscuration, and not classified as thin or partial.
Center of Gravity (CG) The theoretical point where the entire weight of the airplane is considered to be concentrated.
Commercial Aviation Aviation vendor being paid for aviation services.
Contract Aircraft An aircraft that has been approved by OAS for use in accordance with the terms of a formal contract. Generally, there is no monetary limitation on the extent of use of the contract aircraft.
Cooperator Aircraft An affiliated, military or other Government agency aircraft.
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Distance Measuring Equipment (DME) Equipment (airborne and ground) to measure, in nautical miles, the slant range distance of an aircraft from the DME navigation aid.
Drag The air's resistance to moving objects.
Dual-Function PilotAny person who acts as pilot-in-command of an aircraft while on official Government business and is not a full-time pilot (Office of Personnel Management classification 2181), but whose job description does include pilot duties.
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Elevator A control surface on the trailing edge of the horizontal stabilizer used to control the up or down movement of the airplane's nose. In some airplanes, the entire horizontal stabilizer can move, acting as the elevator. Movement of the elevator is controlled by either the control yoke or side stick. A trim system minimizes the force needed to hold the elevator in the proper position for climb, cruise, descent, and other flight conditions.
Emergency (a) Life-Threatening - A situation or occurrence of a serious nature, developing suddenly and unexpectedly and demanding immediate action to prevent loss of life.
(b) Operational - An unforeseen combination of circumstances that calls for immediate action, but not life-threatening.
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Fatal Injury Any injury which results in death within 30 days of the accident.
Federal Aviation Administration (FAA) The government agency responsible for air safety and operation of the air traffic control system. The FAA also administers a program that provides grants from the Airport and Airway Trust Fund for airport development.
Federal Aviation Regulations Rules and regulations contained in Title 14 of the Code of Federal Regulations.
Ferry Flight A flight for the purpose of: returning an aircraft to base, delivering an aircraft from one location to another, or moving an aircraft to and from a maintenance base. They do not carry revenue passengers.
First Aid Any medical attention that does not result in a bill for services. If a physician prescribes medical treatment for less than serious injury and makes a charge for this service, that injury becomes "medical attention."
Flaps Control surfaces on the trailing edge of the wing which are used to increase the amount of lift generated by the wings at slower speeds. Allow aircraft to takeoff and land at slower speeds.
Flight Crewmember A pilot, flight engineer, or flight navigator assigned to duty in an aircraft during flight time who holds a valid Federal Aviation Administration (FAA) Airman's Certificate and flight physical.
Flight Service Station (FSS) Air traffic facilities that provide pilot briefing, en route communications and VFR search and rescue services; assist lost aircraft and aircraft in emergency situations; relay ATC clearances; originate NOTAMS; broadcast aviation weather and NAS information; receive and process IFR flight plans; and monitor NAVAIDs. In addition, at selected locations, FSSs provide En route Flight Advisory Service (Flight Watch), take weather observations, issue airport advisories and advise Customs and Immigration of transborder flights.
Forced Landing A landing necessitated by a situation, which may or may not result in damage.
Fuselage The central body portion of an aircraft. Houses the crew, passengers and cargo and is pressurized and temperature controlled. An aircraft's wing and tail are not considered part of the fuselage.
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General Aviation That portion of civil aviation that encompasses all facets of aviation except air carriers.
Ground Mishap, Aircraft Ground Mishap An aircraft mishap in which there is no intent to fly; however, the power plants and/or rotors are in operation and damage incurred requiring replacement or repair of rotors, propellers, wheels, tires, wing tips, flaps, etc., or an injury is incurred requiring first aid or medical attention.
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Hazard, Aviation Hazard Any condition, act or set of circumstances that exposes an individual to unnecessary risk or harm during aviation operations.
Heading The direction in which the longitudinal axis of the airplane points with respect to true or magnetic north. Heading is equal to course plus or minus any wind correction angle.
High Performance Airplane An airplane that has more than 200 horsepower or that has a retractable landing gear, flaps, and controllable propeller.
High Reconnaissance A route of flight which includes reconnaissance and is conducted above 500' above ground level (AGL). This reconnaissance does not include any aircraft maneuvers which are in excess of commercial pilot skills, maneuvering below 1.4 Vso, or climbs/turns/descents greater than standard rate. This does not include any type of precise maneuvering or specialized equipment.
Horizontal Stabilizer The airfoil or small wing at the rear of the aircraft that balances lift forces generated by the wings and increases stability. In some airplanes, the stabilizer is fixed and the elevator attached to its trailing edge. In other airplanes, the entire stabilizer can move, acting as the elevator, which controls the up or down movement of the airplane's nose. A trim system minimizes the force needed to hold the elevator in the proper position for climb, cruise, descent, and other flight conditions.
Hover Landings Hover landings are landings which do not meet the definition of toe-in, single-skid, or step-out landings. These landings are characterized by the necessity to maintain a substantial amount of hover power while the landing gear is in contact with the surface. This is normally due to the nature of the surfaces such as swampy ground, tundra/muskeg, snow, lava rock, etc. During these landings, the potential CG shifts are not as hazardous as in the previously mentioned landings (i.e., toe-in, one-skid); however, the pilot remains alert and on the controls as opposed to a flat surface/flat pitch landing stability.
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IFR Aircraft/IFR Flight An aircraft conducting flight in accordance with instrument flight rules.
Incident An occurrence other than an accident, associated with the operation of an aircraft which affects or could affect the safety of operations.
Incident with Potential (IWP) An incident that narrowly misses being an accident and in which the circumstances indicate significant potential for substantial damage or serious injury. Final classification will be determined by the USDA-FS National Aviation Safety and Training Manager or the OAS Aviation Safety, Training, Program Evaluations and Quality Management Chief, as appropriate.
Inspector (a) OAS Accepted Inspector. An individual employed by a government agency other than DOI who is listed on the USFS Approved Inspectors List.
(b) OAS Approved Inspector. Any inspector approved by OAS. This includes OAS employees, DOI employees, and other government agency employees listed on the OAS Approved Inspectors List.
(c) OAS Inspector. An OAS employee listed on the OAS Approved Inspectors List.
Instrument Meteorological Conditions (IMC) Meteorological conditions expressed in terms of visibility, distance from clouds and ceiling less than minima specified for visual meteorological.
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Knot An abbreviation for one nautical mile per hour. In terms of distance, a knot is 15 percent longer than a statute mile. Therefore, a knot is equal to 1.15 statute miles or 1.85 kilometers.
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Landing Gear Those components comprising the tires, wheels and related assembly upon which an aircraft lands, and which provides mobility for the aircraft while on the ground. Includes all supporting components, such as the tail wheel or tail skid. Retracted during flight.
Large Helicopter A helicopter with a certified gross weight over 12,500 pounds.
Latitude Measurement north or south of the equator in degrees, minutes and seconds.
Lift The force generated by the movement of air across the wings of an aircraft. When enough lift is generated to overcome the weight of an aircraft
Long Range Navigation (LORAN) An electronic navigational system by which lines of position are determined by measuring the difference in the time of reception of synchronized pulse signals from fixed transmitters. LORAN-C operates in the 100-110 kHz frequency band.
Longitude Measurement east or west of the prime meridian in degrees, minutes and seconds.
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Maintenance Deficiency An equipment defect or failure which affects or could affect the safety of operations, or that causes an interruption to the services being performed.
Medical Attention An injury which is classified as less than serious, for which a physician prescribes medical treatment and makes a charge for this service.
Medium Helicopter A helicopter with a certified gross weight between 6,000 and 12,500 pounds.
Military Aircraft An aircraft maintained and operated by an active or reserve component (all Reserve forces, as well as Army National Guard and Air National Guard) of the DOD, or by any active or reserve component of the U.S. Coast Guard (USCG). All references to military aircraft include both DOD and USCG aircraft. The U.S. Government Manual describes the USCG as follows:

"The Coast Guard is a branch of the Armed Forces of the United States at all times and is a service within the Department of Transportation except when operating as part of the Navy in time of war or when the President directs."

Mishap, Aviation Mishap Mishaps include aircraft accidents, incidents with potential, aircraft incidents, aviation hazards and aircraft maintenance deficiencies.
Mountain Flying - Airplanes Conducting flight operations that require special techniques including takeoffs and landings at locations with 5,000 feet above sea level or greater pressure altitudes, at temperature ranges above 75oF, and/or limited and unimproved airstrips.
Mountain Flying - Helicopters Conducting flight operations in mountainous terrain including pinnacle landings and approaches at varying elevations and pressure altitudes of over 5,000 feet above sea level at temperature ranges above 75oF, and in areas of rugged peaks, deep canyons, cliffs, rock outcropping, steep slopes; including landing on mountain tops and confined areas surrounded by trees, brush, rocks, snow or ice.
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OAS-Designated Routes Flight routes designated by OAS which are bureau-requested, over mountainous terrain and pilot-specific.
Offshore Operations These are operations beyond a point where navigation by visual reference to landmarks can be made.
Operational Control, Aircraft Under the Operational Control of DOI The condition existing when a DOI entity exercises authority over initiating, conducting or terminating a flight.
Operated by DOI, Aircraft Operated by DOI The condition existing when the pilot-in-command is a DOI employee acting on official Government business for DOI.
Operating Agency An executive agency or any entity thereof using agency aircraft which it does not own.
Operating Cost Expenses which include, but not limited to: lease costs, crew costs, maintenance costs (materials and labor), fuel costs, facilities costs, administrative support costs, etc.
Operator Any person who causes or authorizes the operation of an aircraft, such as the owner, lessee, or bailee of an aircraft.
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Passenger Any person aboard an aircraft who does not perform the function of a flight crewmember or air crewmember.
Pilot in Command (PIC) The pilot responsible for the operation and safety of an aircraft during flight time.
Pitch A description of the movement of the nose of an aircraft up or down in relation to its previous attitude.
Point-to-Point Flight Flights between airports (excluding operations defined in 351 DM 1 as Special Use) for which the route of flight is determined only by the pilot(s) based on navigational requirements.
Positive Control The separation of all air traffic within designated airspace by air traffic control.
Precautionary Landing A landing necessitated by a situation which makes continued flight inadvisable.
Precision Reconnaissance (including Fire Recon) This type of reconnaissance is conducted above 500' AGL. Transect type operations, utilization of specialized equipment, or missions not normally conducted in the commercial sector are examples of specific tasks which require special consideration and which make this a special-use activity.
Pressurized Aircraft An aircraft that is kept at a designated atmospheric pressure to enable passengers and crew to breath normally.
Privately Owned Aircraft Any aircraft piloted by a DOI employee on official business which has an FAA registration showing the DOI employee as an owner(s) or member of the club which owns the aircraft.
Public Aircraft An aircraft used only for the United States Government; or owned and operated (except for commercial purposes) or exclusively leased for at least 90 continuous days by a government (except the United States Government), including a State, the District of Columbia, or a territory or possession of the United States, or political subdivision of that government; but does not include a government-owned aircraft transporting property for commercial purposes; or transporting passengers other than a) transporting (for other than commercial purposes) crewmembers or other persons aboard the aircraft whose presence is required to perform, or is associated with the performance of, a governmental function such as firefighting, search and rescue, law enforcement, aeronautical research, or biological or geological resource management; or, b) transporting (for other than commercial purposes) persons aboard the aircraft if the aircraft is operated by the Armed Forces or an intelligence agency of the United States. An aircraft described in the preceding sentence shall, notwithstanding any limitation relating to use of the aircraft for commercial purposes, be considered to be a public aircraft for the purposes of this part without regard to whether the aircraft is operated by a unit of government on behalf of another unit of government, pursuant to a cost reimbursement agreement between such units of government, if the unit of government on whose behalf the operation is conducted certifies to the Administrator of the Federal Aviation Administration that the operation was necessary to respond to a significant and imminent threat to life or property (including natural resources) and that no service by a private operator was reasonably available to meet the threat. 49 U.S.C. 40102 (a)(37).
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Radar Term coined from the phrase "Radio Detecting and Ranging." It is based on the principle that ultra-high frequency radio waves travel at a precise speed and are reflected from objects they strike. It is used to determine an object's direction and distance.
Ramp The aircraft parking area at an airport, usually adjacent to a terminal.
Range The maximum distance, based on fuel capacity and rate of fuel consumption, that an aircraft is capable of transporting passengers and/or freight.
Rating A statement that, as part of a certification, sets forth special conditions, privileges or limitations.
Roll A description of the rolling or banking movement of an aircraft to the left or right. The wing ailerons control roll.
Rudder A control surface on the trailing edge of the vertical stabilizer that controls the yaw motion of the aircraft - that is, the motion of the nose of the aircraft left or right. A trim system minimizes the force needed to hold the rudder in the proper position for various flight conditions.
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Series, Helicopter The sub grouping of makes and models such as Bell 206A, Bell 206B, Bell 206L. The letter designator of A, B and L denotes series.
Serious Injury Any injury which: (1) requires hospitalization for more than 48 hours, commencing within 7 days from the date the injury was received; (2) results in a fracture of any bone (except simple fractures of fingers, toes, or nose); (3) causes severe hemorrhages, nerve, muscle, or tendon damage; (4) involves any internal organ; or (5) involves second or third degree burns, or any burns affecting more than 5 percent of the body surface.
Shore That area of the land adjacent to the water which is above the high water mark and excludes land areas which are intermittently under water.
Single-Skid Landings Single-skid landings are those landings that are used to drop off or pick up passengers or cargo while holding the helicopter with one full skid on the ground and the other suspended in the air. When in contact with the ground, the center of gravity can shift laterally. This type of landing is normally used in sloping terrain or when the helicopter cannot land and reduce the power to flat pitch.
Small Helicopter A helicopter with a certified gross weight under 6,000 pounds.
Special Use Activities In DOI, Special Use Activities involve the utilization of airplanes and helicopters in flight operations which do not meet the definition of point-to-point flight (see 350 DM 1) and which require special considerations due to additional equipment and/or the increased complexity inherent in such operations. Point-to-point missions, when flown in Department owned or contracted aircraft, shall be considered civil aircraft operations and must be flown in full compliance with the applicable provisions of 14 CFR. Regardless of any status as a public aircraft, pilots must comply with the applicable provisions of 14 CFR and deviate only as authorized by published Department policy.
Special Use Airspace (SUA) Airspace of defined dimensions identified by an area on the surface of the earth wherein activities must be confined because of their nature and/or wherein limitations may be imposed upon aircraft operations that are not a part of those activities. Types of special use airspace are:
Alert Area Airspace which may contain a high volume of pilot training activities or an unusual type of aerial activity, neither of which is hazardous to aircraft. Alert Areas are depicted on aeronautical charts for the information of nonparticipating pilots. All activities within an Alert Area are conducted in accordance with Federal Aviation Regulations. Pilots of participating aircraft as well as pilots transiting the area are equally responsible for collision avoidance.
Controlled Firing Area Airspace wherein activities are conducted under conditions so controlled as to eliminate hazards to nonparticipating aircraft and to ensure the safety of persons and property on the ground.
Military Operations Area (MOA) Airspace established outside of Class A airspace area to separate or segregate certain nonhazardous military activities from IFR traffic and to identify for VFR traffic where these activities are conducted. (Refer to Airman's Information Manual)
Prohibited Area Airspace designated under FAR Part 73 within which no person may operate an aircraft without the permission of the using agency. (Refer to En route Charts, AIM)
Restricted Area Airspace designated under FAR Part 73, within which the flight of aircraft, while not wholly prohibited, is subject to restriction. Most restricted areas are designated joint use and IFR/VFR operations in the area may be authorized by the controlling ATC facility when that airspace is not being utilized by the using agency. Restricted areas are depicted on en route charts. Where joint use is authorized, the name of the ATC controlling facility is also shown. (Refer to FAR Part 73 and AIM)
Warning Area Airspace of defined dimensions extending from three nautical miles outward from the coast of the United States that contains activity potentially hazardous to nonparticipating aircraft. The purpose of such warning area is to warn nonparticipating pilots of the potential danger. A warning area may be located over domestic or international waters, or both. 
Step-out Landings Step-out landings are those landings that are used to drop off or pick up passengers and cargo (other than rappel/short haul) while holding the helicopter in a hover. The helicopter is not in contact with the ground and the center of gravity can shift laterally and longitudinally. This type of landing is normally used in lieu of toe-in/single-skid landings in terrain where the helicopter cannot land and reduce power to flat pitch.
Substantial Damage Damage or failure which adversely affects the structural strength, performance, or flight characteristics of the aircraft, and which would normally require major repair or replacement of the affected component. Engine failure or damage limited to an engine if only one engine fails or is damaged, bent fairings or cowling, dented skin, small punctured holes in the skin or fabric, ground damage to rotor or propeller blades, and damage to landing gear, wheels, tires, flaps, engine accessories, brakes, or wing tips are not considered "substantial damage" for the purpose of 49 CFR Part 830.2 Definitions.
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Thrust The force produced by a jet engine or propeller. It can also be defined as the forward reaction to the rearward movement of a jet exhaust.
Toe In Landings Toe-in landings are those landings that are used to drop off or pick up passengers or cargo by resting the helicopter on the toes of the skids. This requires holding a significant amount of hover power (within 15% of hover power) to keep the helicopter from falling backwards. When the helicopter is operated in this manner, there is the potential of significant lateral and longitudinal CG shift during loading/offloading operations. When the helicopter is balanced on the forward 1/3 or less of the skid tube, main rotor blade clearance is another significant concern (1/2 of flat surface/flat pitch blade clearance). These landings are normally used where landing areas are on slopes which exceed the capability of the helicopter. Identification criteria for toe-in landings are:

(1) Inability to reduce below hover power by 15%
(2) Forward 1/3 or less of skid tube in contact with surface
(3) 1/2 or less of flat pitch/flat surface blade clearance exists

Traffic Alert and Collision Avoidance System (TCAS) An electronic system installed in aircraft that searches for and alerts pilots to the presence of other aircraft. More advanced versions of TCAS also advise pilots of actions to take to avoid approaching aircraft, if warranted.
Transponder An electronic device that "responds" to interrogation by ground-based radar with a special four-digit code that specifically identifies the aircraft on which it is located. Certain transponders have the ability to transmit automatically the altitude of the aircraft in addition to the special code.
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Uncontrolled Airspace Known as Class G Airspace. Consists of the airspace not designated controlled airspace (Class A, B, C, D and E).
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Vendor An operator being paid by DOI or USFS for services.
Vertical Stabilizer The large "tail" surface on the top rear of the fuselage used to increase stability. The rudder is attached to the trailing edge of the vertical stabilizer and controls the left or right movement of the airplane's nose. A trim system minimizes the force needed to hold the rudder in the proper position for various flight conditions.
Very High Frequency Omnidirectional Range (VOR) A ground-based electronic navigation aid transmitting very high frequency navigation signals, 360-degrees in azimuth, oriented from magnetic north. VOR is used as the basis for navigation in the National Airspace System. The VOR periodically identifies itself by Morse Code and may have an additional voice identification feature. Voice features may be used by ATC or FSS for transmitting instructions/information to pilots.
Visual Flight Rules (VFR) Rules that govern the procedures for conducting flight under visual meteorological conditions (VMC). Aircraft flying under VFR are not required to be in contact with air traffic controllers and are responsible for their own separation from other aircraft. The term also is used in the United States to indicate weather conditions that are equal to or greater than minimum VFR requirements. In addition, it is used by pilots and controllers to indicate a type of flight plan.
Visual Meteorological Conditions (VMC) Meteorological conditions expressed in terms of visibility, distance from clouds and ceiling equal to or better than specified minima.
Volunteer Service Volunteer services is limited to personal services received without compensation (salary or wages) by the Department from individuals or groups.
VORTAC A navigational system that provides both VOR and TACAN course guidance, plus distance (DME) information.
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Windshear Weather phenomenon entailing a strong downdraft of air that can result in the loss of lift for an aircraft passing through it.