Groundschool
Navigation
You will need to be familiar with basic navigation techniques
To be able to confidently use a navigation computer and to have the required level of knowledge able to pass the JAR Navigation examination
You will need a Chart, Ruler, Protractor and a Navigation Computer (CRP)
DIRECTION
Definition: Direction is the angular position of one point to another without reference to the distance between them.
Direction is divided into 360 degrees
Compass Directions are expressed as a three digit number:
- North 000/360 degrees
- East 090 degrees
- South 180 degrees
- West 270 degrees
Bearings:
- True: Chart North
- Magnetic: Compass North
- Relative: Heading or Nose of a/c
SPEED
Definition: Speed is the rate at which distance is covered; calculated using distance travelled divided by time taken
Units for speed is KNOT (nautical mile per hour)
True Air Speed (TAS): Speed through air mass
Ground Speed (GS): Speed over the ground
Wind Speed (V): Speed of the air mass
Air Speed Indicator:
- Calibrated for ISA density 1225 gm/cubic metre
- Changes in Pressure & Temperature affect density and hence TAS
- ASI will read Rectified (Calibrated) Airspeed (RAS/CAS)
QUESTIONS
- With a RAS of 85 kt, the temperature at 5000' is -5 degrees Celsius, what is the TAS?
- 80 kt
- 90 kt
- 100 kt
TRIANGLE OF VELOCITIES
Definition: Velocity has direction and speed, a vector has a length proportional to the speed, and an orientation in line with the direction.
Triangle of Velocities has three sides:-
- Heading & True Air Speed - one arrow - represents motion of the aircraft through the air
- Track & Ground Speed - two arrows - represents the motion of the aircraft over the ground
- Wind Direction & Wind Speed - three arrows - represents the motion of the air over the ground
THE EARTH
Definition: The Earth can be represented as a sphere rotating about an axis running from a geographic north to south pole
- Latitude: lines running horizontally around the world from equator to pole measured in degrees, minutes and seconds
- Longitude: lines running vertically around the world passing through both poles, measured in degrees minutes and seconds
- 1 degree = 60 minutes
- 1 minute = 60 seconds
- Nautical Mile: the distance the 1 minute of arc of latitude measures on the earth's surface
QUESTIONS
- WHAT IS THE EXACT LATITUDE AND LONGITUDE OF SOUTHEND AIRPORT?
- N5134.2 E00041.9
- N5104.2 E00041.9
- N5104.2 E00011.9
- WHAT FEATURES ON THE 1:500000 SOUTHERN ENGLAND CHART AT POSITION N5240.2 E00117.0?
- A MAST
- COLTISHALL MILITARY AERODROME
- NORWICH AIRPORT
CHARTS
Definition: An aeronautical chart represents the spherical surface of the earth on a small flat piece of paper
Scale: A model of the earth is produced at reduced size, this is called the reduced earth.
Lambert Conformal Conic Projection: The chart sheet is a cone that cuts the reduced earth sphere in two places
Mercator Cylindrical Projection: The chart sheet is a cylinder that is formed around the equator of the reduced earth
Compass North & Variation: Chart North and Compass North are not co-incident, isogonals indicate the variation between magnetic north and true north.
|
NAVIGATION COMPUTER
The CRP Navigation computer is a circular slide rule on one side, and allows the triangle of velocities to be resolved on the the other
Wind Up Method: in five simple steps:
- Set wind direction under INDEX, and mark upwards from the blue central dot, a line whose distance is equivalent to the wind speed
- Set your desired track under the INDEX
- Move the slider up or down, until your wind mark is indicating your TAS
- Read of the drift required to maintain your desired track, as the angle between your wind mark and the central vertical line. Add if on the right, subtract if on the left
- Read of the G/S under the blue dot, repeat 2-5 for each track
How to use the Wind Down Method
QUESTIONS
- What is the required heading to maintain a track of 125 degrees true, with a TAS of 90 kt, and the wind predicted at W/V 260/15?
- 117
- 125
- 132
VERTICAL NAVIGATION
Altimeter
Pressure instrument
QNH pressure a msl: Altitude
QFE pressure at aerodrome level: Height
QNE aerodrome pressure altitude: Flight Level
Terrain Clearance
Calculation of MSA:
Chart indicates MEF (Maximum Elevation Figure)
No obstacle under 300' will be shown
Either add 1299' to highest ground within 5nm either of track, or add 1000' to MEF
To calculate a Minimum Safe Altitude.
NB: whilst flying VFR you can fly below your MSA, so long as you do not infringe the low flying rules. The MSA is the absolute minimum for flight in instrument conditions
QUESTIONS
- An aircraft departs from "a" en route to "b" on a magnetic track of 180o. Along the route is high ground 1000m amsl. The QNH is 990 mb, what is the minimum flight level the aircraft can fly to clear the high ground by 1000'. Assume 1 mb is 30'.
- FL 40
- FL 60
- FL 30
FLIGHT PLANNING
Preflight
- Aircraft: documents, tech log, pre-flight inspection
- Weather: self briefing, and suitable for duration of flight
- NOTAMS: checked
- Route & Alternate: sensible alternate aerodromes
- Daylight: sunset
- VFR or IFR
- Fuel Planning: trip, hold & taxi, alternate, 10% contingency
- Aircraft Performance: CogG, take-off and landing distances required
LOST PROCEDURE
Formulate a Plan:
- Check last known position and time
- Read from Ground to Map
- Establish a circle of certainty
- TALK to someone. Many aeronautical stations have VDF, or known someone who can help (121.50)
- Consider flying reciprocal heading to relocate a known feature
- Consider precautionary landing if weather, daylight and fuel are at all an issue
RADIO NAVIGATION
VDF: VHF Direction Finding
- Displayed as a radial line on a screen, indicating QDM, QDR, QTE, QUJ, if requested
- Southend 128.95 is a VDF station
NDB: Non Directional Beacon
- Radiates on signal in all directions in MW band
- An ADF (Automatic Direction Finding) can be tuned into this frequency, and a display will indicate relative bearing TO
- Usually quite a short range, and affected by, night fall coastal refraction, precipitation and thunderstorms
VOR: VHF Omnidirection and Range
- VHF, so requires a line of sight, the higher the transmitter and receiver the better
- Displays QDM or QDR of aircraft TO/FROM transmitter
- Unaffected by weather, coastlines and night
SSR: Secondary Surveillence Radar
- Transponder and DME are both SSR
- Transmitter and Interrogator
- Special codes and allows altitude encoding (Mode C)
RADAR:
- Primary radar blips paint on a PPI (plan position indicator)
- Secondary radar requires transponder, and affords radar controllers greater situational awareness
- All radar is line of sight, and benefits from being mounted high, and reflectors/receivers flying high
- Radar range is improved using narrow beams with large radar dishes
Other Groundschool subjects
Introduction to the PPL ~ Air Law ~ Propellers ~ Principles Of Flight