Aerial Navigation: Maps and the Compass 1941 US Army Pilot Training Film; Signal Corps
US Army Training Film TF-1245
Public domain film from NASA, slightly cropped to remove uneven edges, with the aspect ratio corrected, and mild video noise reduction applied.
The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and/or equalization.
There is a broadband hum in the vocal frequencies of this film which I cannot completely remove.
The basic principles of air navigation are identical to general navigation, which includes the process of planning, recording, and controlling the movement of a craft from one place to another.
Successful air navigation involves piloting an aircraft from place to place without getting lost, breaking the laws applying to aircraft, or endangering the safety of those on board or on the ground. Air navigation differs from the navigation of surface craft in several ways: Aircraft travel at relatively high speeds, leaving less time to calculate their position en route. Aircraft normally cannot stop in mid-air to ascertain their position at leisure. Aircraft are safety-limited by the amount of fuel they can carry; a surface vehicle can usually get lost, run out of fuel, then simply await rescue. There is no in-flight rescue for most aircraft. Additionally, collisions with obstructions are usually fatal. Therefore, constant awareness of position is critical for aircraft pilots.
The techniques used for navigation in the air will depend on whether the aircraft is flying under visual flight rules (VFR) or instrument flight rules (IFR). In the latter case, the pilot will navigate exclusively using instruments and radio navigation aids such as beacons, or as directed under radar control by air traffic control…
The first step in navigation is deciding where one wishes to go. A private pilot planning a flight under VFR will usually use an aeronautical chart of the area which is published specifically for the use of pilots. This map will depict controlled airspace, radio navigation aids and airfields prominently, as well as hazards to flying such as mountains, tall radio masts, etc. It also includes sufficient ground detail – towns, roads, wooded areas – to aid visual navigation. In the UK, the CAA publishes a series of maps covering the whole of the UK at various scales, updated annually. The information is also updated in the notices to airmen, or NOTAMs.
The pilot will choose a route, taking care to avoid controlled airspace that is not permitted for the flight, restricted areas, danger areas and so on. The chosen route is plotted on the map, and the lines drawn are called the track. The aim of all subsequent navigation is to follow the chosen track as accurately as possible. Occasionally, the pilot may elect on one leg to follow a clearly visible feature on the ground such as a railway track, river, highway, or coast.
When an aircraft is in flight, it is moving relative to the body of air through which it is flying; therefore maintaining an accurate ground track is not as easy as it might appear, unless there is no wind at all — a very rare occurrence. The pilot must adjust heading to compensate for the wind, in order to follow the ground track. Initially the pilot will calculate headings to fly for each leg of the trip prior to departure, using the forecast wind directions and speeds supplied by the meteorological authorities for the purpose… A general aviation (GA) pilot will often make use of either the E6B flight computer – a type of slide rule – or a purpose-designed electronic navigational computer to calculate initial headings.
The primary instrument of navigation is the magnetic compass. The needle or card aligns itself to magnetic north, which does not coincide with true north, so the pilot must also allow for this, called the magnetic variation (or declination). The variation that applies locally is also shown on the flight map. Once the pilot has calculated the actual headings required, the next step is to calculate the flight times for each leg. This is necessary to perform accurate dead reckoning…
The flight time will depend on both the desired cruising speed of the aircraft, and the wind – a tailwind will shorten flight times, a headwind will increase them. The E6B has scales to help pilots compute these easily.
The point of no return, sometimes referred to as the PNR, is the point on a flight at which a plane has just enough fuel, plus any mandatory reserve, to return to the airfield from which it departed… Similarly, the Equal time point, referred to as the ETP (also Critical point(CP)), is the point in the flight where it would take the same time to continue flying straight, or track back to the departure aerodrome…