18.4.4 Explain the processes, cautions and limitations when deriving track distances and
bearings from a chart.

When measuring track distances on a chart, make sure you measure in the middle of your track, that you measure accurately, and that you use the correct scale of ruler. 

When measuring bearings, make sure you line the protractor up with True North, and that you accurately read off the track line against the bearing. 

Following a constant heading creates a track called a Rhumb Line. This is the easiest method of travelling from one point to another.

It is not however the shortest track. The shortest track is following the path of a great circle. To do this a constant change of heading throughout the flight is required.

A Rhumb Line cuts each Meridian at a constant angle, this angle will be our heading relative to True North. Over a large distance and as we get closer to the poles, the issue with following this path becomes apparent.

  

To achieve the shortest track, a Great Circle path must be followed, This is more difficult as it requires many constant adjustments to the heading throughout the flight. Modern Flight Computers are perfectly suited to handle this issue

 

Tracking directly along the equator or directly true north creates a path that is both a Rhumb Line and a Great Circle

[vfr_{Model p1=”windtriangle” p2=”example=yes”]

(b) time and distance to a departure/destination equi-time point (ETP)

Equi-time Point is important to know when you have a problem you need to know quickly  what to do you go return to your departure point or carry on to your destination.

No wind

In a no-wind situation it is easy it is the halfway point due to your ground speed being the same on the way out as it is on your way back home.

Things get a whole lot more interesting when you start adding wind in to the situation which we always seem to have.

As you will observe how the Equi-Time Points (ETP) will all moved toward the wind

Head wind

Leg	Ture Airspeed	Wind Component	Ground Speed	Distance	Time
A to ETP	200kts	-40kts	160kts	160mn	1hr
ETP to B	200kts	40kts	240kts	240mn	1hr

Head wind (Example 2)

Leg	Ture Airspeed	Wind Component	Ground Speed	Distance	Time
A to ETP	100kts	-20kts	80kts	160mn	2hr
ETP to B	100kts	20kts	120kts	240mn	2hr

Tail Wind 

Leg	Ture Airspeed	Wind Component	Ground Speed	Distance	Time
A to ETP	200kts	40kts	240kts	240mn	1hr
ETP to B	200kts	-40kts	160kts	160mn	1hr

18.70.4 Briefly describe the coordinate systems in common use by GPS/GNSS units.

18.48.4 Describe techniques for:
(a) position fixing;
(b) changing heading to make good the desired track;
(c) changing heading to make good next turning point or destination;
(d) amending ETA.

18.46.4 Calculate the expected fuel burn on a given leg.

18.40.4 List the factors to be considered when selecting altitudes at which to fly in the cruise.

18.34.4 Using a navigation computer, solve triangle of velocity problems (given four of the six
variables):
(a) heading and track ( 2);
(b) TAS and GS ( 2kts);
(c) wind velocity ( 3/ 3kts);
(d) drift ( 1).

.

18.28.4 Solve mathematical equations:
Sub Topic Syllabus Item
(a) multiplication ( 2%);
(b) division ( 2%);
(c) proportion ( 2%).