Flight Navigation General Flashcards
What is an isogonal?
A line joining points of equal magnetic variation.
When flying from Auckland to Perth on a great circle, will the track be a curve or straight line if you were using a Lamberts chart?
Great circles are straight lines on Lamberts charts.
Explain a mercator projection
- Turns a sphere into a cylinder
- All meridians are straight lines with parallel spacing
- Rhumb line will appear straight
- Great circle appears curved.
Explain a Small Circle
Any circle drawn on the earth whose radius is not the earth.
How do you calculate TAS given IAS?
TAS = IAS + (miles a minute x alt in thousands )
How do you calculate bank angle for a rate 1 turn given airspeed?
Bank angle = (TAS/10) x 1.5 or + 7.
Formula for turn radius / arc turn on?
Turn radius = 1% of TAS / 2.
What is earth convergency?
The angle of inclination between two meridians at a given latitude.
What is the speed of rotation of the Earth?
900kts at the equator
Speed = 900 x cos(latitude)
How do you calculate a reciprocal heading
Initial heading ± 200 ±20.
What is a Great Circle
A circle drawn on the surface of the earth whose radius is the earth. The shortest distance between two places.
When flying from Auckland to Perth on a great circle track, what happens to heading?
It slowly increases as great circles are concave to the equator on Mercator charts.
Explain lambert projection
- turns a sphere into a cone
- meridians are straight lines
- lats and longs intersect at right angles
- rhumb lines are curved concave to poles
- great circles are straight.
Explain a Rhumb Line
A line drawn on the earth’s surface which cuts each meridian at the same angle.
What is the conversion angle?
Angular difference between the great circle track and rhumb line track between two points.
How do you calculate a ToD?
3 x altitude to lose in 1000’s of feet plus 1nm per 10kts of slowdown required.
(This gives 333 feet per nm, can divide height to lose by 3 and add a zero for 300 feet per nm version).
Use top version for ToD but brackets version for non-precision or visual approaches.
Formula for distance on a DME arc?
Distance=radials / (60/DME distance).
Explain parallels of latitude
Small circles (except equator) that are Rhumb lines crossing meridians east to west.
Explain orthomorphism.
- The scale on the chart must be correct to the scale nearby.
- Parallels and meridians must cross at right angles.
What is the departure formula?
For figuring out how many nm east-west at a particular latitude.
Distance = longitude (in arc minutes) x cos(latitude)
Define a nautical mile.
- The distance on the surface of the earth which subtends an angle of 1 arc minute.
- 6080 feet.
- 1° latitude = 60nm.
What are the three kinds of errors an INS can have?
- Bounded errors - errors that do not increase with time or increase/decrease in a cycle. E.g. north alignment error will produce bounded velocity error.s
- Unbounded errors - errors that increase with time. E.g. initial position errors and north alignment errors (in position).
- Inherent system errors. E.g. change in distance travelled with height, the fact earth is not a true sphere.