Nav 2 Flashcards
Why is no chart of earth completely accurate
- A sphere is a undevelopable surface (paper is two-dimensional and the earth is 3-D)
- Problem is developing a method for transferring the meridians and parallels to a developable surface that will preserve certain desired characteristics
Desirable chart characteristics
- Constant scale
- Course lines are great circles
Describe a great circle
A great circle is a circle formed by continuing the arc inscribed by connecting the shortest distance between two points on a sphere
OR
A circle whose plane passes through the earth’s center, dividing it into two equal halves
Describe a great circle route
- Shortest distance between two points
- Every meridian is a great circle
- The equator is the only parallel that is a great circle
Describe Lambert Conformal Charts
The most widely used projection.
A “conic” projection
Characteristics of a Lambert
- Parallels are equally spaced concentric circles
- Meridians are straight lines converging at the poles
- Scale is a constant distance scale
- Great circle routes plot as straight lines
List types of Lambert Conformal Charts
- Operational Navigation Chart (ONC)
- Tactical Pilotage Chart (TPC)
Describe the Operational Navigation Chart
- Provides a worldwide coverage at a scale of 1:1,000,000
- Contains multicolor hydrographic and cultural features
- Used for planning long-range navigation
Describe the Tactical Pilotage Chart
- Provides worldwide coverage at 1:500,000
- Has greater detail for visual and low-level radar nav
- Most common chart for route planning
Why is Mercator not used
Variable distance scales
Curved great circle routes
Define Course
The aircraft’s intended flight path.
Any straight line between two points on a Lambert is the True Course
Define Heading
the direction the nose of the aircraft is pointing. Will differ from the course to compensate for crosswind
Define Track
The aircraft’s actual flight path over the ground. Shown as a dashed line
Explain magnetic variation
The angular difference between true north and magnetic north from any given position on the earth’s surface. Expressed in degrees east or west
Equations for computing true and magnetic directions using magnetic variation
MC = TC - East Variation
MC = TC +West Variation
Describe the global timekeeping system
A common time standard that allows for coordination of assets on a global basis.
Time zone characteristics
360 degrees/24hours = 15 deg/hr. Gives us 24 time zones; each with 15 deg of width
Define local mean time
The time withing each zone
What time format is used in flight plans?
Greenwich mean time
Most common source for zone descriptions
IFR enroute supplement
Purpose of a divider
measure distance
Describe the purpose of a plotter
Used to aid in drawing course lines and measuring direction
List parts of a plotter
- Straightedge
- Grommet
- Protractor
- Scales
3 Vectors of the Wind Triangle
Air, Ground, Wind
