NAV Flashcards
02 What is air navigation?
The art of directing an aircraft from one position to another, and of determining the position of the aircraft over the earth at any time. (In other words: Finding out where you are, where you should be, and how to match the two)
02 What is an oblate spheroid
An oblate spheroid is a symmetrical body with a ‘bulge’ in one axis compared to the other (equatorial diameter is longer than the diameter from pole to pole).
02 What is a great circle?
A circle on the surface of the earth whose centre and radius are those of the sphere itself. A great circle divides a sphere into two equal hemispheres. It is also the shortest distance (along the Earth’s surface) between two points.
02 What is the equator?
A great circle on the surface of the Earth whose plane is perpendicular to the Earth’s axis of rotation.
02 What is a small circle?
A circle on the surface of the earth whose centre and radius are NOT those of the sphere itself. All circles on the surface of the Earth that are not great circles are small circles.
02 What is a parallel?
A small circle on the surface of the Earth whose plane is parallel to the equator.
02 What is a Parallel of Latitude
Angular distance from the equator measured along a meridian. Units are Degrees° Minutes’ Seconds”. Winnipeg Intl is at 49°54’36”N.
02 What is the meridian?
A semi-Great circle on the surface of the Earth joining the poles of the Earth.
All meridians converge at the poles.
Meridian is the angular distance from the prime meridian, measured along the shorter arc of the equator.
02 What is a rhumb line?
A regularly curved line on the surface of the Earth cutting all meridians at the same angle.
A Rhumb line is used to allow a path of flight to be a straight line on some maps. (Eg Mercator projections)
When flying a rhumb line the heading remains constant whereas if flying a great circle constant heading changes are required
02 What is a nautical mile (NM)?
Length of an arc on the surface of the Earth subtending 1minute. (1/60th of a degree) at the centre of the curvature of the place
1NM = 6,080 feet = 1’ of latitude
02 What is a statute mile (SM)?
An arbitrary unit of measurement which was set by law (ie a statute) in 1593 at 5,280 feet.
Not used in aviation navigation, but commonly used in meteorological visibility measurements.
This is the mile used for road distance in the US and UK
02 What is a Kilometre (km)
1 kilometre = 1000 metres.
The metre was originally defined in 1793 as 1/10,000 of the average distance between the equator and the North pole.
Redefined in 1983 as the length of the path travelled by light in a vacuum in 1/299,792,458 of a second.
1Km = 3,280 feet
02 _NM=_SM=_km
66 NM = 76 SM = 122 km
03/04 What is direction?
The position of one point in space relative to another, without reference to the distance between them.
The angle that a line makes with some reference datum line passing through the point
Always measured clockwise from the datum
Always expressed in a THREE figure group
03/04 What are the cardinal points?
North, South, East, West
03/04 What are the quadrantal points?
North East, North West, South East, South West.
03/04 Which system is used in air navigation? (Base 60)
The sexagesimal system. (Angular Distance in Degrees, Minutes, Seconds) Base of 60 (eg: 60 seconds in a minute)
Used for time and direction
03/04 What is cardinal direction
East - The direction in which the earth is spinning
West - The direction opposite to East
North - The direction of the North Pole
South - The direction opposite to North
03/04 What is true direction?
Direction measured with reference to the direction of the geographic North Pole.
03/04 What is magnetic direction?
Direction measured with reference to the direction of Magnetic North at the place.
Magnetic Force
There are 2 regions on the surface of a magnet where its attractive force for material like iron or steel is the greatest.
The attractive force is treated as if it emanates from 2 internal points called the poles.
An ordinary magnet has a magnetic axis, approximated by a line joining the poles.
The magnet has two poles, normally referred to as north and south poles, and is surrounded by lines of magnetic force, which run from pole to pole.
The poles are the position of the greatest field intensity. Magnets exhibit the property of attraction of unlike poles, and repulsion of like poles.
03/04 What is the magnetic meridian?
The direction of the horizontal component of the earth’s magnetic field at a point.
A compass needle will align itself with the magnetic meridian, pointing to the magnetic north pole. (powerpoint)
The vertical plane fixed by the direction of the line of force. It is also the direction taken by a perfect compass needle (notes section)
03/04 What is secular change?
Average value changes in the Earth’s magnetic field over time, reflecting changes in the Earth’s core = unpredictable
02 What are the radii at the equator and the poles?
6378 km and 6356 km
02 How many CT-142 does 402 Sqn have?
4
02 Where is 0 degrees longitude found?
Greenwich was chosen as the prime meridian in 1884 at the International Meridian Conference, defines 0° longitude.
03/04 What are the magnetic poles?
The poles are the position of the greatest field intensity. They are the projection onto the surface of the axis of the Earth’s magnetic field.
03/04 What is a local anomaly?
The anomaly may be natural or it may be artificial. The magnitude depends on the nature of the magnetic material. The effects of these anomalies will decrease rapidly with height above the surface – approx the inverse cube of the distance.
03/04 Define annual variation?
When the average monthly values of the magnetic elements are corrected for the secular change, it is found that there is a small systematic change from month to month. For example the horizontal or ‘H’ component is stronger in summer.
03/04 Define daily change?
There is a small fluctuation of each of the magnetic elements, which repeats itself with some degree of regularity day after day, and is known as the daily change.
03/04 What is a magnetic storm?
Solar flares (sunspots) cause irregularities in the earth’s magnetic field.
03/04 Define soft iron magnetism?
Caused by the magnetism induced into soft material. The soft magnetic material of an aircraft is magnetized by induction of the magnetic field in which they lie. Consists of magnetic fields induced solely by the earth’s magnetic field.
03/04 Define isogonal?
A line on a map joining points of equal variation; not coincident with the magnetic meridian and therefore does not indicate the direction of the earth’s field at a point.
03/04 What is an agonic line?
A line on a map joining points of zero variation.
03/04 Define compass direction?
Direction measured with respect to compass north
03/04 What is deviation?
The horizontal angle between compass north and magnetic north
03/04 Explain the Best/Least rule?
Deviation West = Compass Best, Deviation East = Compass Least.
03/04 What is variation?
The angular difference between the magnetic meridian and the true meridian, at any point is called variation.
The horizontal angle between true north and magnetic north
03/04 Define hard iron magnetism?
The aircraft’s own magnetic field. This field is caused by the permanent magnetism resident in the aircraft’s structure and by the magnetism from onboard electrical systems.
03/04 What is compass north?
The direction taken by a compass needle.
03/04 Solve for MH and CH: TH = 138, VAR = 10E, DEV = 3E.
MH = 128, CH = 125.
05/06 What are three methods of expressing position on the Earth?
Place names, bearing and distance, grid names (GEOREF; LAT/LONG).
05/06 What is latitude?
Angular distance from the equator measured along a meridian. Units are Degrees° Minutes’ Seconds”. Winnipeg Intl is at 49°54’36”N.
05/06 What is longitude?
A semi-Great circle on the surface of the Earth joining the poles of the Earth. All meridians converge at the poles. Measures distance east or west of the prime meridian
05/06 How do you write latitude and longitude?
Latitude first (2 digits), then longitude (sometimes 3 digits). Except for GEOREF.
05/06 What time is used during aviation?
Zulu/ Universal Time Coordinate.
05/06 What is GEOREF?
A type of grid system - Earth is divided into sections (quadrangles). Consists of 288 sections, 15 degrees longitude by 15 degreees latitiude. (in the house, up the stairs).
07/09 What is conformality?
The correct representation of angles.
07/09 What is orthomorphism?
Shapes are perfectly defined in a small area.
07/09 What are the criteria for orthomorphism?
Conformal; scale is the same in all directions and angles are preserved.
07/09 What is scale?
A ratio of a given distance on a map to the actual distance on Earth.
07/09 How can you express scale?
Representative fraction; statement in words; graduated scale.
07/09 Compare a large and a small scale?
Large scale = small area, more detail; small scale = large area, less detail.
07/09 What are the three kinds of map projections?
Cylindrical, conical, and azimuthal/tangential.
07/09 What is an example of a cylindrical projection?
Mercator Projection (Transverse and Oblique Mercator included).
07/09 Describe the projection of a Transverse Mercator?
Line of tangency touches both poles and follows a meridian/anti-meridian.