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Visual Flight Rules Navigation(061.02)

Ground features (061.02.01.00)

Visual identification (061.02.01.02)

Problems of VFR navigation at lower levels (061.02.01.02.01).

At lower levels, the pilot’s field of view is restricted by (high) terrain, vegetation, buildings and other ground features which may hide checkpoints until very close and for a limited periode of time. Thus visual checkpoints may not stand out or align with chart symbols easily when flying at low level.

Furthermore, at low level, obstacles and terrain are closer and more frequent (i.e. power lines, masts, trees and structures). So, maintaining vertical situational awareness (e.g., avoiding terrain or controlled flight into terrain)becomes more critical at low level. Also other traffic is harder to spot and avoid at lower levels, which make collision avoidance more demanding.

Pilot’s should be aware that visibility can be even further reduced by:

  • Meteorological causes;
  • Environmental and time-of-day effects;

Meteorological causes:

  • Fog and Mist – Low-lying moisture reduces slant and horizontal visibility at lower levels;
  • Haze and Smoke – Particulates scatter light and reduce clarity over distance. Also other ground-level plumes van temporarily reduce visibility.
  • Precipitation (rain, snow, drizzle) – Attenuates visibility and can obscure ground references.
  • Sand or Dust – In certain regions, airborne particles can dramatically reduce visible range.
  • Valley inversions and temperature effects – Cold air trapped against terrain surfaces can hold moisture and create localized visibility reduction.

Environmental and time-of-day effects:

Low Sun angles / glare – Sun glare near horizon can mask features or create illusions.

Shadowing and Contrast reduction – At low altitude, shadows can make terrain features hard to distinguish.

Another aspect to take into account is that VFR navigation (the old-fashioned way), is about timing and correct heading. As turbulence is more of a problem closer to the ground, it can make it difficult to maintain the correct airspeed, heading and altitude, and may even cause difficulty reading the instruments or the navigation log.

Last but not least, radio communications and radar services are more likely to be less effective at lower altitudes.

Problems of VFR navigation at night time (061.02.01.02.02).

When navigating VFR at night, pilots have to take into account, even when there is unlimited visibility and not a cloud in the sky, that there will be an absence of sufficient visual clues. Obstacles and terrain may not be that easy to see (especially with little cultural lightning and no moonlight).

The lack of visual clues (e.g. the horizon) at night time, will increase the risk of spacial disorientation and visual illusions. Some of the possible visual illusions are:

  • Somatogravic and somatogyral – illusions related to the perception of gravity and the perception of rotation. Without a clear horizon, or clear external reference in general, it is extremely difficult to maintain a straight and level flight and might even result in loss of control.

    Flying visually but with cross-reference to  instruments is essential at night.
  • Runway Visual Perspective – may give rise to a visual illusion that may result in landing short of the runway, hard landing or runway overrun.
  • Autokinetic Effect – when staring at a single point of light against a dark background it might look like it is moving on its own. This way, a star or a planet can easily be mistaken for an aircraft.

The best ways to avoid night illusions are:

  • Flying with cross-reference to  instruments;
  • Adjust the cockpit lighting to improve night vision and reduce reflections.
  • Red and green lighting of cockpit instruments is improving night vision. The eye uses a light-sensitive protein called “rhodopsin” that activates the rod cells and makes you see at night. Especially red light breaks down this protein more slowly.
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VFR Navigation techniques (061.02.02.00)

Use of visual observations and application to in-flight navigation (061.02.02.01)

Map Reading (061.02.02.01.01)

Map reading is the ability to correctly interpret aeronautical charts in order to determine the aircraft’s position, direction, distance, terrain, obstacles, airspace and other relevant navigation information for the safe conduct of a flight.

Map reading consists of two skills:

  • “Map to ground”;
  • “Ground to map”;

Visual Checkpoint (061.02.02.01.02)

A visual checkpoint is defined as a clearly identifiable ground feature that can be positively recognized visually from the air and on the chart, used to confirm an aircraft’s position during VFR flight. Where a visual checkpoint should be :

  • Unambiguous (not easily confused with nearby features);
  • Charted on the aeronautical chart in use;
  • Fixed and reliable (not temporary or seasonal);
  • Distinctive in shape, size, or contrast;

Typical (EASA-accepted) examples:

  • Towns or villages (with a distinctive layout)
  • Road or railway junctions
  • Large rivers (bends) or river–road crossings
  • Lakes or reservoirs
  • Large industrial sites or power stations
  • Coastline features (headlands, bays)
  • Airfields

Unplanned events (061.02.02.02)

Unsure-of-Position Procedure

As soon as the position of the aircraft is in doubt:

  1. Note the time;
  2. “Turn on Time” and use dead reckoning techniques until a visual fix can be made.
    • Estimate the distance travelled since the last known position;
    • Compare the ground with your estimated position on the map (look for hills, valleys or line features such as a motorway, railway, large rivers or coastlines;
      And/or consider using any radio-navigation aids that may be available to give position information.
    • Once the position has been re-established, keep checking the heading (and look out for other aircraft) and continue the flight by updating the estimated position regularly while looking for unique features such as a lake, built-up area, mast, or a combination of roads, rivers and railways.
  3. Communicate with Air Traffic Control (ATC) and request assistance;
  4. If sort on fuel, or near controlled airspace, and not in contact met ATC, set 121.5Mhz and make a PAN call;

Procedure when lost

In cases where the pilot cannot verify their position, it is advised to initiate the “unsure of position” procedure. Should the pilot be unable to ascertain their position even after, they should proceed with the “lost procedure.”

Climb:
One of the pilot’s major concerns when lost, is the terrain separation. Climbing to a higher level is the best action to take in case you get lost. This will ensure obstacle clearance, Increase radio reception and probably improve visibility.

Communicate:
Contact ATC or Flight Service for help, state who you are, what you need, and that you are LOST. Don’t hesitate—ATC is there to help and there is no penalty for admitting it.

Comply:
Follow ATC instructions. They may ask you to squawk a specific code (i.e. 7700) and identify you on the radar. From there on they can give you vectors.

Conserve:
Keep a close look at the meteorological conditions and endurance (fuel status). If weather is deteriorating or you are low on fuel, inform ATC and plan for the nearest suitable airport. If this out of reach, try to identify an area suitable for a precautionary landing.

Another way of thinking about the “lost procedure” is based on the “HELP ME” mnemonic:

H: High ground / obstructions – are there any nearby?
E: Entering controlled airspace – is that a possibility?
L: Limited experience, low time or student pilot – let someone know.
P: PAN call in good time – don’t leave it to late.

M: MET conditions – is the weather deteriorating?
E: Endurance – is fuel getting low?