VFR Maps, Weather & Winds

Basic sectional chart interpretation is included in this lesson.  You will be expected to be able to interpret basic aspects of a sectional chart including but not limited to:

  • Identify airports by location and code and basic information regarding runway length and heading

  • Identify navigation facilities - VOR, NDB and DME facilities

  • Identify key landmarks - roads, railroads, rivers and other bodies of water and key structures / VFR checkpoints that provide reliable navigation by pilotage

  • Identify hazardous structures and restricted or hazardous areas AND be able to idenentify the Maximum Elevation Figure (MEF) for the quadrants you will fly through

  • Identification of towered and non-towered airfields along with pertinent frequencies for communication and information and the availability of services such as fuel and airport lighting.

  • Demonstrate a basic understanding of controlled airspace and how it is identified on a sectional or other map - the first page of this information from the FAA provides a quick summary of airspace classification - Airspace Classification - FAA 

 

The Aeronautical Chart User Guide from the FAA contains a great deal of information on both VFR and IFR charts that will serve as a good reference now and in the future  FAA Aeronautical Chart User Guide . For the purposes of this course you might find this document that provides just the VFR Chart Symbols.  You should know that if you use a source such as www.skyvector.com  these can be zoomed in and out which can distort the standard scale of a sectional chart which is 1:500,000

This is an example of one of many web sites that give some basic information on reading sectional charts - much less info than the FAA publication but just an overview --- Sectional Chart Basics  (note the disclaimer) and an excerpt from the complete FAA Aeronautical Chart User Guide provided by the Texas Interagency Coordination Center that covers the VFR symbols portion of the FAA Guide.

You can find other information on the web - including these videos from the Fly8MA.com folks that cover the basics of sectional chart interpretation and the second which gets into more detail and covers some of the more unusual aspects of sectional charts.

Video on Basic Sectional Chart Interpretation

Video on Advanced Sectional Chart Knowledge

Understand the basic rules of determining cruising altitude for VFR flight in an fixed-wing aircraft (does not apply to helicopter, powered parachute or weight-shift control aircraft):

  • Appropriate altitude for the terrain and obstacles enroute

  • Appropriate altitude for the direction of flight

    • Below 3000 feet AGL - any altitude (although some pilots will still follow the rules for above 3000 ft AGL when possible) but adhering to the following requirements

      • Anywhere:  An altitude that, in the event of power failure or other emergency, provides for an emergency landing which can be done without undo hazard to persons or property on the ground

      • Over Congested Areas - An altitude 1000 ft. above the highest obstacle within a horizontal radius of 2000 ft.of the aircraft

      • Over Other Than Congested Areas - An altitude 500 ft. above the surface unless over water or sparsely populated areas, in which case the aircraft cannot be operated within 500 ft. of any structure, person, vehicle or vessel.

    • Above 3000 feet AGL - 

      • Zero to 179 degrees magnetic heading: Odd thousands plus 500 feet (e.g., 3500 ft., 11,500 ft.)

      • 180 degrees to 359 degrees magnetic heading; Even thousands plus 500 feet (e.g., 6500 ft., 14,500 ft.)

  • Uncontrolled VFR flight is not permitted above 18,000 feet

You should also be aware of the basic altitude rules for determining cruising altitude for IFR  flight:

  • IFR flight is permitted below 3000 ft. AGL but may not be considered good practice but otherwise can be done at any altitude that provides appropriate terraine and obstacle clearance

  • Appropriate altitude for the direction of flight above 3000 ft AGL

    • 180 degrees to 359 degrees magnetic heading; Even thousands (e.g., 6000 ft., 14,000 ft.)

    • Zero to 179 degrees magnetic heading: Odd thousands (e.g., 5000 ft., 11,000 ft.)

Understand basic interpretation of a METAR - all have the same format but do not have headings or other identifiers of the information.  Information is presented in the same format for all METARs so it is the sequence that provides the 'identifier' for each part.  For example:

 

KSAT 061851Z 16012G20KT 10SM BKN040 BKN250 33/22 A3009  - where each part is interpreted as follows

  • KSAT - the station identifier (usually coincides with an airport, in this case San Antonio International)

  • 061851Z - the day of the month (06) and the time (UTC time)

  • 16012G20KT - wind direction (160 degrees), wind speed (12 gusting to 20 knots) - note that some European METARS may give wind speed in kilometers per hour (KPH) or meters per second MPS)

  • Visibility - US METARS use statute miles (SM) so the visibility is 10 SM or more since the maximum given is 10 SM.  European METARS generally give visibility in meters where 0000 indicates < 50 meters visibility and 9999 indicates 10 KM or more

  • Clouds - here the ceiling is broken clouds at 4000 feet (040) and broken clouds at 25,000 feet (250) - usual abbreviations for cloud cover is FEW, SCT (scattered), BKN (broken) and OVC (overcast)

  • Temperature and dew point - both in degrees C

  • Altimiter setting in inches of mercury (inHg). 

 

Some abbreviations are intuitive - KT for knots, BKN for broken, SM for statue miles, RA for rain.  But, since the original METAR system was developed by the French you will find some abbreviations to be not quite so obvious - BR for mist (French: Brume),   FU for smoke (French: Fume'e).  You can get the current METAR (along with other weather information) here: METAR Data/Decoder   - note that you can get the raw data form of a METAR or have this site decode it for you.

Our page on Reading METARs and TAFs in the Tools and Resources section of the website will provide additional information.

 

Understand how to correct your heading for wind - the basic rules of thumb work in most cases but you can find a number of online E6B calculators - for example:  Online E6B  - OR - see below for the '1 in 60' rule for heading correction.

The rule of thumb for estimated the crosswind and tailwind / headwind components is:

The 5-7-9 rule for 30°, 45° and 60° angled cross winds

  • For a 30° angled wind, the cross wind component = 50% x wind velocity; the tailwind/headwind component = 90% x wind velocity

  • For a 45° angled wind, the cross wind component = 70% x wind velocity; the tailwind/headwind component = 70% x wind velocity

  • For a 60° angled wind, the cross wind component = 90% x wind velocity, the tailwind/headwind component = 50% x wind velocity

  • For a direct (90°) crosswind use 100% of the wind velocity

  • For a direct headwind or tailwind there is no crosswind component

Drift Correction for Crosswind – Based on True Air Speed, Using the '1 in 60' Rule:

 

Cross wind heading correction (degrees) = ( Crosswind Component / True Airspeed) x 60

 

The correction is added to the current heading if the crosswind is from the right and subtracted from

the current heading for a crosswind from the left – That is, the correction is applied by turning into  the wind.

 

Example:  Crosswind of 15 knots at 45° from the right of the aircraft, coming from the right and behind.  True air speed = 120 knots.

 

Using the 5-7-9 rule:  Crosswind component = 70% of 15 (0.7 x 15) = 10.5

 

Heading correction for the crosswind =  (10.5/120) x 60 = 10.5/2 = (approximately) 5 degrees - 

it is actually 5.25 degrees but that quarter of a degree will be very hard to see on most HSIs or gyro compasses and the '1 in 60' rule itself is just an approximation so trying to make this too precise is not warranted.

The cross wind component comes from the same side as the angled crosswind, so if the wind is from the right the cross wind component will be from the right (pushing you to the left)

And - along with crosswind correction understand how to apply the headwind / tailwind component (calculated using the E6B or by the rules of thumb, above) to obtain your expected ground speed.  So - for the conditions in the drift correction example above the tailwind component (since winds are coming from the right and behind the aircraft) is also 10.5 knots - round to 11 knots, your ground speed would be TAS + tailwind = 110 + 11 = 121 knots.  Had this been a headwind your ground speed would be 99 knots.

You can download our document that includes this and other rules of thumb here:  Aviation Rules of Thumb