Section 4 EO C437.02 – USE A VISUAL FLIGHT RULES (VFR) NAVIGATION CHART (VNC)

Earth is a sphere, so its surface cannot be represented accurately on a flat plane. Therefore, a map shows a portion of the Earth's surface with some distortion. There are four basic elements in map construction:

Depending on the particular purpose of the map, one or more of these elements is preserved with minimal distortion, with the most distortion in the remaining elements.

Using the globe and the sheet of construction paper, demonstrate the impossibility of wrapping the sheet around the globe smoothly to create a chart.

The two principal types of chart projections used in air navigation charts are:

Using the globe and the sheet of construction paper, demonstrate superimposing a cone over the surface of the globe.

Note. From "Image: Lambert Conformal Conic", Wikimedia. Retrieved November 27, 2008, from http://commons.wikimedia.org/wiki/Image:Lambert_conformal_conic.svg

Figure 1  Lambert Conformal Conic Projection

The properties of the Lambert Conformal Conic Projection are:

VNCs and World Aeronautical Charts (WACs) are examples of Lambert Conformal Conic Projections.

The Transverse Mercator Projection. Applies the Mercator technique by rotating the cylinder 90 degrees so the point of tangency is a meridian of longitude rather than the equator. This projection is accurate in depicting scale, especially on charts covering a relatively small geographical area. The VFR Terminal Area (VTA) Charts are examples of Transverse Mercator Projections.

Using the globe and the sheet of flip chart paper, demonstrate wrapping a cylinder around the globe with its point of tangency at a meridian of longitude.

Note. From "Swiss Map Projections", 2008, Federal Office of Topography Swisstopo. Retrieved November 27, 2008, from http://www.swisstopo.admin.ch/internet/swisstopo/en/home/topics/survey/sys/refsys/projections.html

Figure 2  Transverse Mercator Projection

Show the cadets a VNC.

VNCs are designed primarily for visual navigation at low altitudes and slow speeds. Each chart is identified by the name of a principal landmark on the chart (eg, Toronto, Winnipeg, Gander). The scale of the chart is 1 : 500 000 or about one inch to eight miles.

Show the cadets a WAC.

WACs are designed primarily for visual navigation at higher altitudes and greater speeds. Each chart depicts a sizeable portion of the country's geographical area—eighteen charts cover Canada. Each chart is identified by a letter and a number. For example, E17 covers the area from Marathon, Ont., west to Brandon, Man., and from the 48^th parallel north to Thompson, Man. The scale of the chart is 1 : 1 000 000 or about one inch to 16 miles.

Show the cadets a VTA Chart.

VTA Charts are large scale charts (1 : 250 000) published for airports where there is a high volume of air traffic and where there is usually a mix of controlled airspace. Radio communication information and other information that is necessary for conducting flight through the area are given on the chart.

Show the cadets an Enroute Chart.

Enroute Charts provide information for radio navigation over designated airways systems. Enroute Charts do not portray any cities, towns, or topographical features. They depict all radio navigation aids, including airways, beacons, reporting points, and communication frequencies. Examples of Enroute Charts are Enroute Low Altitude Charts, Enroute High Altitude Charts, and Terminal Area Charts.

Canada Flight Supplement (CFS). A joint civil / military flight information publication and a supplement of the Aeronautical Information Publication (AIP). It contains information on Canadian and North Atlantic aerodromes. The CFS is designed to be used in conjunction with all Canadian charts and should be carried by every pilot departing on a flight. It is revised and reissued every 56 days.

The cadets were introduced to latitude and longitude in EO M437.01 (Define Air Navigation Terms). They were asked to find the coordinates of a major airport. In this TP, the cadets are given the coordinates and asked to find the landmarks. They should require minimal instruction as it is a review.

Give the cadets coordinates of several landmarks on a local VNC and have them identify the landmarks.

For example, 43°59'N, 80°17'W is a soaring site (Grand Valley).

Note. From Toronto VFR Navigation Chart, by Geomatics Canada, 2001, Ottawa, ON: Geomatics Canada Department of Natural Resources. Copyright 2001 by NAV CANADA and Her Majesty the Queen in Right of Canada.

Figure 3  Example of a VNC

To plot a track between landmarks on a VNC:

1.Identify the landmarks.

2.Use a ruler to draw a straight line between the landmarks.

Give the cadets coordinates of a departure aerodrome and a destination aerodrome on a local VNC. Have them plot a track.

More advanced flight plan plotting (eg, 10-degree drift lines) will be taught during future aviation training.

Measure distance on a VNC by:

Using a Scale

The scale of the chart is the relationship between a unit of distance (eg, one inch) on the chart to the distance that the unit represents on the surface of the Earth.

There are two scales found on a VNC:

Note. From From the Ground Up: Millennium Edition (p. 123), by A. F. MacDonald and I. L. Peppler, 2000, Ottawa, ON: Aviation Publishers Co. Limited. Copyright 2000 by Aviation Publishers Co. Limited.

Figure 4  Graduated Scale Line

To measure distance on a VNC using the representative fraction:

1.Use a ruler to measure the distance between two landmarks in inches.

2.Multiply the number of inches by eight to determine the distance in statute miles.

To measure distance on a VNC using the graduated scale:

1.Use a straightedge to measure the distance between two landmarks.

2.Line the straightedge up with the graduated scale, starting at the zero mark, to determine the distance in kilometres, nautical miles, or statute miles.

Have the cadets practice measuring distance using each technique.

Using an ICAO Ruler

ICAO ruler. A plastic straightedge graduated in both statute and nautical miles for use with 1 : 1 000 000 and 1 : 500 000 scale charts. On its reverse side, the ICAO ruler provides conversion factors, VHF reception distances, standard time conversions to Co-ordinated Universal Time (UTC), time equivalencies, flight plan sequences, and an aviation gasoline conversion table.

Note. From "Other Publications", Aviation Publishers. Retrieved November 28, 2008, from http://www.aviationpublishers.com/otherpub/icao.html

Figure 5  ICAO Ruler

To measure distance on a VNC using an ICAO ruler:

1.Align the edge of the ruler with the track. Ensure the zero mark is at one of the landmarks.

2.Read the desired scale (nautical miles or statute miles) where the ruler meets the other landmark.

Use the edge of the ICAO ruler meant for 1 : 500 000 scale charts.

Have the cadets practice measuring distance using this technique.

Douglas protractor. A tool used for determining headings and as a straightedge. It is transparent and has a compass rose graduated in 360 degrees marked around the outer edges.

Note. From "Douglas Protractor / Parallel Ruler", VIP Pilot Centre. Retrieved November 28, 2008, from http://www.canada-shops.com/Magasin/vippilotcenter/c46907p95758.2.html

Figure 6  Douglas Protractor

To determine a heading on a VNC using a Douglas protractor:

1.Place the protractor on the chart with the hole in the centre lying on the track at a point where the north-south line on the protractor lies along the meridian of longitude. If this is not convenient, one of the vertical lines can be lined up parallel with the nearest meridian.

2.Read the heading where the track cuts the edge of the protractor.

Have the cadets determine the headings of the tracks previously plotted. Have them plot more tracks and determine the headings as time permits.