Nav Flashcards
What is static pressure?
Where the pressure is exerted equally in all directions. (No movement)
What is dynamic pressure?
The pressure due to relative movement. Dependent on the speed and density of the air.
What is RAS?
Rectified air speed is the IAS corrected for instrument error.
What is ground speed?
The speed of the a/c over the ground. TAS corrected for wind.
When is ground speed used?
The speed seen on radar.
What is airspeed?
The speed at which an a/c moves through the air mass.
What is IAS?
Indicated air speed is the airspeed shown on the air speed indicator?
What 4 errors can IAS suffer from?
- Instrument faults
- Poor positioning of the pitot head
- Density, height or temperature error
- compressibility error
What is the TAS?
The true air speed is the RAS corrected for density error.
What is compressibility error?
At speeds in excess of 300knts the air in front of the a/c becomes compressed causing errors in the reading.
What is instrument error?
An error in the calibration of the instrument usually in the region of 2knts. Modern a/c have this corrected when testing instruments but some older a/c have a card for the pilot to know how far out it is.
What is the Pitot tube?
A tube on the front of the a/c that uses an expanding diaphragm to measure the dynamic pressure. This pressure is then compared to static pressure and shown on the airspeed indicator as IAS.
What is speed?
Rate of change of position.
What is velocity?
Rate of change of position in a given direction.
What is the most accurate representation of the Earth?
A sphere or globe.
How is a projection made?
By placing a conical or cylindrical sheet of paper onto an illuminated globe and coping the projection onto a piece of paper. This can then be laid flat but will be distorted.
What does conformal mean?
All angles and bearings are accurately represented.
What is a meridian?
A straight line along the Earths surface from pole to pole.
What is a parallel?
A straight line along the Earths surface that is parallel to the equator. Centres on the nearest poll.
What is a graticule?
One square of the ‘mesh’ made up by parallels of latitude and meridians.
What is ground velocity?
The track and the ground speed.
What is a vector?
A graphical representation of velocity.
What is mach numbers?
Mach number is a measurement relative to the speed of sound. At speeds close to and above Mach 1 Mach is used instead of Knots.
What is the avg. speed of sound?
- 661 knots at MSL
- 589 knots at 30,000ft
What is air velocity?
The heading and the TAS.
What is a rumb line?
A line that intersects all meridians at the same angle.
What is a great circle?
A circle that wraps around the Earth whose plane cuts directly through the centre of the Earth.
What is a small circle?
A circle that wraps around the Earth whose plane does not cut through the centre of the Earth.