Focus On Training
Old School Navigation
Basic navigating technique is still an important skill to learn and use despite any GPS supporters who may argue that it is obsolete.
When Columbus set out across the Atlantic in 1492, he used a compass that pointed northward, a crude timepiece, and a method of calculating speed based on the time for an object in the water to travel the length of the ship. Using a navigating technique called dead reckoning, he was able to determine his position from the time already traveled and the speed of the ship. Although unencumbered by concerns about fuel endurance, deadlines or diminishing daylight, the navigation on these early voyages of discovery was inexact and landfall more of a waiting game — it made sighting land a cause for celebration.
Fast forwarding to the present, the VFR (visual flight rules) helicopter navigator is much more concerned with accurate ground tracking, fuel requirements, pre-planned arrival times and legal daylight.
In Canada, Nav Canada is the source for weather information about existing and future winds, cloud cover and any other meteorological information needed to plan enroute altitudes, headings and ground speeds. In the United States, that information is available by phone from a Federal Aviation Administration Flight Service Station, or online through the FAA’s Direct User Access Terminal service.
When it comes to speed, true airspeed can be significantly higher than indicated airspeed at high altitudes. However, since helicopters generally fly low and slow, the two are usually very close.
In a headwind or tailwind, groundspeed (GS) changes according to wind strength. In a crosswind, GS changes via the headwind or tailwind component of wind strength: a direct crosswind should not affect GS.
The flight route is plotted on a Transverse Mercator aviation chart. Using a protractor, track lines are drawn and headings are measured relative to the geographic meridians and parallels. The magnetic compass in the helicopter aligns to the nearest magnetic meridian, called an isogonic line. The angle between the magnetic and geographic meridians is the variation, which appears on the chart as a westerly or easterly numeric value.
If Columbus had known about the westerly variation in the Atlantic, he would have added to the chart headings to navigate accurately. Instead, his tracking was constantly to the left, which is why he sailed southwest to the Bahamas after leaving Spain, instead of straight west.
In North America, the north/south agonic line of zero variation is located mid-continent, and points west of that have an easterly variation, requiring a reduction in chart headings to determine magnetic headings.
Using the magnetic compass, headings and track across the ground will be the same in still air. However, you will need to turn toward a crosswind to maintain track: increase the heading for a right crosswind and decrease it for a left one.
To determine exact headings and groundspeeds, use the traditional E6B calculator, a portable electronic device or a virtual calculator online.
For density altitude, remember that it varies from indicated altitude according to height and temperature. If landings at higher altitudes are necessary at your destination — especially in higher-than-normal temperatures — the calculated density altitude may be much higher than the indicated altitude. That means the helicopter will have reduced performance (as if it were at a higher altitude).
Once planning is complete, it’s time to fly. The altitudes and headings you’ve chosen will keep you clear of weather and on track in the wind. Your estimated arrival time will allow for fuel and daylight concerns. But, your job is not done.
The real work of navigating begins in flight. In addition to marking off time and setting heading, be sure to fly at the planned cruise speed or all your hard work will be compromised. Revise headings and arrival times as necessary if the wind changes speed and/or direction.
When viewing the map, hold it in front of you within the same visual plane as the instrument panel and outside terrain references. Match the track-line progress along the chart with the equivalent terrain features ahead, and revise the pre-planned heading accordingly. Give preference to map reading and not heading control by itself: helicopters, by nature, are very unsteady, so maintaining a steady altitude and heading takes scanning and practice.
Is the lake ahead just any body of water, or is it the landmark that you planned your trip to end at? If you have been careful to align the terrain features enroute with the same features found on the map, along the heading you planned and your expected arrival time has expired, then you are definitely at the correct lake.
Basic air navigation is an important skill to have even if you primarily rely on GPS — because a basic VFR navigator can carry on if the system fails, while GPS-only flyers have to wait for the satellites or system to come back on line.
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