VFR Navigation
Home >> Aviation Guides >> VFR Navigation
WIP
VFR, or Visual Flight Rules, is flying & navigating by terrain, landmarks or other visual features outside the aircraft. This guide is intended to help new players with mastering this skill. The guide is divided into three parts - Navigation basics, Flight planning and Follow-up during flight. Flight planning is the planning performed before starting the flight, and follow-up covers methods for continuously verifying that you are where you are meant to be once underway.
Innehåll
Speed terms
There are several different methods for qualifying an aircraft's speed relative to the air Indicated Air Speed (IAS) is the uncorrected speed which is displayed on an aircraft's airspeed indicator. Multiple factors affect either the air itself or the airspeed instrument causing this airspeed to, genereally speaking, not actually match the aircraft's speed true speed relative to the air. The main error sources are Instrument error (Errors due to the construction / design of the cockpit instrument), Position error (When the positioning of the Pitot tube causes the pressure reading from which the airspeed is calculated to be inaccurate) and Density error (The airspeed instrument is calibrated for standard sea-level density, meaning that it will get less and less accurate as the measured air density decreases with increased altitude)
Calibrated Air Speed (CAS) is the IAS but corrected for instrument and position errors. In real life the airplane manufacturer provides the pilot with the information required to convert IAS to CAS. In DCS this information is rarely inlcuded in manuals - if no information is provided, assume that IAS = CAS.
EAS - Får gärna fyllas i av någon IRL-jet-nörd. Mvh// Flyger-aldrig-över-115-knop
True Air Speed (TAS) is a measure of the aircrafts true speed relative to the air. This is calculated by taking the CAS and correcting for the density error. Some DCS aircraft provide you with the TAS automatically. Calculating the TAS manually can be done with a flight computer (see Resources heading at the bottom). Calculating your TAS manually requires known values for pressure altitude, which is simply the reading on your barometric altimeter with QNH entered as well as the outside air temperature (as the density of the air for a given altitude varies depending on the temperature). The temperature in DCS is generally speaking only given for sea level, so to calculate the temperature for a given altitude use the ISA standard temperature change of 2°C / 1000 feet or 6,5°C per 1000 Meters. ¨
E.g. - if the Sea level temperature is +18°C and you're planning to fly at 8000 feet, the expected change in temperature is 2°C * 8 = -16°C. The outside air temperature is thus +2°C.
Ground speed (GS), is the actual speed your aircraft is travelling relative to the ground. This is important for navigating as it is this speed we will be using for calculating how long it will take to fly our waypoints later. Ground speed is calculated by taking the true air speed and correcting this for wind. This calculation can be performed using a flight computer or the online E6B tool linked in the resources section.
To perform the calculation, start by entering the true course in the course field. Enter the True Air Speed in the next field. Enter the Wind direction (Where the wind is coming from) and the wind speed and read the wind correction angle below. This angle is the amount of degrees you'll have to add or subtract from your course in order to compensate for wind. You'll now be able to read the ground speed below the Wind correction angle.
Note 1: Since the only source of variation between TAS & GS is the wind, TAS & GS will be equal if flying with no vind Note 2: In DCS, unlike in real life, the wind strength and direction is constant within the same mission. You will still need to calculate the wind correction angle for each leg as the heading of your aircraft relative to the wind affects the WCA.
Course terms
Courses are given relative to one of three sources - True (Relative to the geographic, or true, north pole), Magnetic (Relative to the magnetic north pole) or compass (Relative to the north pole of the magnetic field which the compass is picking up). In real life compass north deviates from magnetic north due to metallic objects in the airplane interfering with the magnetic field of Earth. To my knowledge this is not modelled in DCS, so focus on understanding True and Magnetic.
Different terms are used for describing various angular differences. Track is the angular difference between two points on the map. True track is defined using true north as a reference and Magnetic Track is defined using Magnetic north.
Heading, or course, is the angular difference between your chosen source of reference and which angle your aircraft is currently pointing.
Bearing is the angular difference between your aircraft and another object - aircraft, bullseye, terrain or something else. True bearing is relative to true north and magnetic bearing is relative to magnetic north.
Wind correction angle
Calculating the WCA is covered in the speed terms section above.
Compass Magnetism
North on most maps is pointing directly towards the geographic north pole. North on an aircrafts magnetic compass is pointing towards the magnetic south pole, which is actually located in the northern hemisphere. The Geographic North Pole and the Magnetic South Pole are not located at the same point, meaning that a compass will not point to true north. The difference between true north and magnetic north for a given location on Earth is called variation and is expressed in either degrees west / east or degrees +/-. The variation for Caucasus is +6°, or E6.
When we make our flight plans using the F10 map we are plotting tracks in relation to true north, but when we then fly these headings (assuming your aircraft isn't displaying true north) you are using magnetic north. You must therefore add or subtract the variation to the magnetic course reading in order to correct for the variation.
For example, if you're flying a waypoint leg in Caucasus with True Track = 360° and Variation is +6°, you should make fly a magnetic course 354° to compensate.
Time, speed and distance calculations
Calculating the time to fly a leg, the distance of a leg or the speed required to fly a leg of a given distance at a given time is made easy wit the SVT-triangle. S stands for Sträcka (Distance), V stands for Velocity (Fart) and T stands for Tid (Time). For as long as two values are known, the third is calculated using the formula in the image below. Simply remove the variable you want to solve for and follow the formula for the remaining two.
Examples: If S = 300 NMI and V= 415 knots, what is T? (How long does it take to fly a given distance at a given speed) Answer: We remove T and find that the formula now states S/V. 300/415 = 0,722. This is the time required expressed in decimal format. To convert this to hours:minutes, simply carry over the hours and multiply everything right of the decimal with 60. 0,722 * 60 = 43,32. Flying this leg will take zero hours, 43 minutes and 32 seconds (00:43:32).
If S = 25 NMI and T = 15 minutes, what is V? (Which speed do I have to maintain to fly a given distance at a given time) Answer: First convert 15 minutes to decimal format. Again we carry over the hours but we now divide everything right of the decimal with 60. 15/60 = 0,25. We can now perform the speed calculation. Remvoing V the formula now says S/T. 25/0,25 = 100. To fly this leg in 15 minutes we require a ground speed of 100 knots.
If V = 215 knots and T = 25 minutes, what is S? (If I fly a given speed at a given time, how far will I travel? Answer: Again we convert time to decimal - 25/60 = 0,416. Solving for distance we remove S from the triangle and find the formula to be V*T. 215*0,416 = 89,44. We will travel 89,44 nautical miles in 25 minutes at 215 knots.
Practice questions
1. If S = 73 and V = 215, what is T?
2. If S = 428 and T = 01:15, what is V?
3. If V = 317 and T = 00:45:30, what is S?
Flight planning
Start by marking your initial point and your destination on the map. Continue by marking waypoints along the route at reasonable intervals. These waypoints act as control points, allowing you to verify that you are flying where you've intended and allowing you to correct and errors before they accumulate too much. I would recommend no more than 20NMI between each waypoint. Generally speaking, shorter legs makes it less likely that you'll get lost, but will also mean that more work is required during the planning phase.
Once you have all your waypoints marked, plot the true track between them. This is the true track. Enter this into your flight plan for each leg. Now add or subtract the magnetic variation to get the magnetic track for each leg. Decide upon a desired altitude for each waypoint.
Next we'll be calculating the magnetic heading, i.e. the course you will be aiming for when flying. Start by deciding upon a certain IAS you want to use for your flight. You can alternate different IAS for different legs to make it more challenging. Once you have that IAS, carry it over to CAS and use that in combination with the outside air temperature and waypoint altitude to calculate your TAS. Now use your CAS and use that in combination with the true track & wind information to calculate your wind correction angle and your ground speed. This step will have to be re-done for every waypoint leg (assuming the track is different between them).
For each individual leg, add or subtract the wind correction angle to the magnetic heading and enter the ground speed into your flight plan. Use this ground speed to calculate how long it will take to fly the leg (leg time) as well as an accumulated total time (the sum of all leg times up to that waypoint).
This is all the core information you require to succesfully navigate from point A to B without crutches such as GPS, NDBs, Tacan etc. Remember that the better and more thorough your flight plan, the easier it will be to perform the flight once in the aircraft.
This guide has not covered control points. These are not proper waypoints but points of interest along your track which are meant to help you verify that you are on-track, such as a bridge, lake or other geographic feature easily seen from the cockpit. I generally find that these aren't required for a waypoint interval of roughly 20nm, but depending on the terrain these may still be a good idea. To add a control point to your flight plan, first measure how far into the leg you should cross it. If you for example cross a bridge 40% of the distance between WP1 and 2, you should reasonably expect to cross that bridge after 40% of your leg time has elapsed. Add the control point to your flight plan and note at which time you ought to fly over it. If during the flight you notice that you're 30 seconds late with flying over the bridge you need to increase your speed a bit to compensate for the rest of the leg.
Example Flight plan
| Waypoint | Latitude | Longitude | Description | True Track | Magnetic Track | Magnetic Heading | Leg time | Total Time |
|---|---|---|---|---|---|---|---|---|
| Start | N42°11’58” | E42°42’02” | Railroad bridge, east of Kutaisi Exit east | 270 | 264 | 268 | 00:05:00 | 00:05:00 |
| 1 | N42°06’33” | E43°02’42” | Road bridge, just south of a railway crossing | 243 | 237 | 241 | 00:07:30 | 00:12:30 |
Follow-up during flight
WIP
