Flight Planning

When planning a cross country flight of any distance, the pilot is required by Federal Aviation Regulations to have knowledge of the destination airport, fuel requirements, estimated time enroute, weather expected along the route and destination, and any other information which may affect the safety of the flight. The pilot should get a thorough weather briefing from a Flight Service Station (FSS), and the filing of a flight plan for VFR flight is strongly recommended.

This section will cover the time, distance, groundspeed, heading, and fuel required aspects of the flight planning process.

Basic Parameters

The planning log must address several factors:
  • Selection of Checkpoints
  • Distances
  • True Course
  • Magnetic Variation
  • Magnetic Course
  • True Heading
  • Magnetic Heading
  • Wind Correction
  • Ground Speed
  • Time Enroute
  • Fuel On-Board
  • Fuel Duration
  • Fuel Consumption

Definitions

Checkpoints

The pilot should determine the type of navigation to be used; Pilotage, VOR and/or Victor Airways, LORAN, GPS, etc. From that information, the pilot should establish checkpoints over which the flight is to pass. They may be prominent landmarks, VOR's, RNAV, LORAN or GPs waypoints. It is suggested for small slow speed aircraft that these checkpoints be within reasonable distances, say 50 nm or so. Distances shorter than this requires a lot of record keeping for long flights. Distances much longer than this does not allow the pilot to verify actual performance versus the plan sufficiently often enough. Generally a checkpoint every 30-40 minutes is a suitable procedure for the experienced pilot.

The pilot should plot the Course of Flight by drawing lines on the chart from checkpoint to checkpoint. It's like drawing your roadway in the sky which you plan to follow. These checkpoints should be written on the flight planning log in the Check Point column of your planning log.

An example flight is illustrated below. The flight is a simple one which a beginning student may be asked to fly. It is a triangular course, from SVH, LEX, 3N8, and back to SVH. You will note later that the wind will have a different effect on ground speed and headings for each leg. Note: This flight will be used as the basis for planning a simple flight and the associated flight planning log.

A simple example log is shown below to demonstrate the basic values to be determined. This is a sample log designed by the author for teaching purposes only. There are numerous commercially prepared log forms on the market. You can purchase them at most airports and pilot supply shops.

You will note that there are a number of items of information whick the pilot must consider:
  • Basic Information
    • Date
    • Winds Aloft - Get from Winds Aloft Forecast
    • True Airspeed (TAS) - Get from Pilot Operating Handbook
    • See -- Cruise Performance for an example table.
    • Fuel Use (gph) - Get from Pilot Operating Handbook

    • See -- Cruise Performance for an example table.
    • Fuel on Board - Based on refueling records
  • Course Data
    • Leg Distances - From the chart
    • - See -- Measuring the distance
    • True Course (TC) - From the chart
    • -- See - Measuring the course Note: COURSE always refers to the "track over the ground".
    • Wind Correction Angle (WCA) - Calculated
    • True Heading (TH) - Calculated
      Note: HEADING always refers to the "direction in which the nose of the aircraft is pointed".
    • Magnetic Variation (VAR) - From the chart
    • See -- Magnetic Variation
    • Magnetic Heading (MH) - Calculated
  • Time, Distance, Ground Speed, Fuel Computation
    • Calculate Ground Speed (GS) using E6B Computer (Wind triangle)
    • Use GS and Distance to calculate leg Time
    • Use Leg Time and Fuel Flow to calculate Fuel Used
    • Calculate Estimated Time of Arrival (ETA) to next check point.
    • Calculate Cumulative Time Enroute and Fuel Used.

Filling out the Planning Log

Heading Information

  • Obtain Winds Aloft data from preflight briefing by a Flight Service Station for the expected flight time.
  • Consult the Pilot Operating Handbook for estimated Fuel consumption and TAS figures.
  • If you know fuel amount on board, calculate flight duration from the POH.

Winds Aloft

Winds aloft are forecast by the Weather Bureau for numerous regions in the U.S. At the levels at which small aircraft fly, the forecasts will give wind direction and velocity in Kts. for 3, 9, and 12 thousand feet. You use the wind forecast nearest the altitude which you plan to fly to calculate the wind drift you expect to encounter. This calculation also derives an estimated Ground Speed which you will use in further calculations. The Wind Correction Calculations are covered later.

True Airspeed and Fuel Consumption

Consult the Pilot Operating Handbook for the aircraft to be flown to determine the power setting you plan to use at the planned flight altitude. See -- Cruise Performance for an example table. From the cruise performance table for the aircraft you should be able to derive estimated TAS and Fuel Consumption in gph. You will later use this TAS to calculate both the estimated WCA and Ground Speed. You will use the fuel consumption figure (gph) to calculate the estimated fuel consumption for each leg.

Course Planning Information

Identify each checkpoint on the chart in some way. It may be a number, an airport name, a VOR name, or city, etc. Write the identification of the each checkpoint in the CHK PT column of the log. Note that the checkpoint lines are not aligned with the other lines in the blank log form shown above.

In our example, our checkpoints are:

CHK PT
SVH
LEX
3N8
SVH
CHECK POINTS

Distance

Measure the distance as shown in Measuring the distance . Enter the distance in Nautical Miles (preferred) in the DIST column for each leg.

DIST
32
31
26

True Course

Using the plotter, measure the TC for each leg, using the example in - Measuring the course example. True Course is always measured in relation to a Longitude Line on the chart ( i.e. relative to True North). Enter the TC for each leg in the TC Column.

Compensating for Wind

In order to keep being blown "off course" by the wind, you probably will have to maintain a heading to either left or right of course to stay on track(TC). This requires that you calculate a Wind Correction Angle (WCA) in order to stay on track.

You can use a manual or electronic E6B Flight computer to compute the WCA. Obviously, when you are riding in a moving air mass, the wind will tend to drift you "Off Course" from your intended ground track.

A Graphical Illustration of WCA

Shown below is a graphical illustration of calculating WCA.

You want to fly a True Course (TC) of 360. The wind is from 290 at 20 Kts. Obviously the aircraft will drift right and off course unless a correction is made. The problem can be solved graphically. On paper, draw a TC line at 360. Draw a wind vector to some scale (line B-A) at 290 and 20kts according to your scale. Draw a TAS line to the same scale from point B to intersect the TC line at point C. In this example TAS = 100 kts. You have now constructed a Wind Triangle. The Wind Correction Angle (WCA) is the angle between line B-C and A-C. In this example it is 10 L. The Ground Speed is line AC, which measures 90 Kts.

It is obvious from this triangle, you have a 10 knot headwind, and must steer a heading 10 to the Left. Therefore to convert your True Course (TC) over the ground to a True Heading (TH) to which to steer, you:

TH = TC + WCA TH = 360 + (- 10) = 350
Treat R WCA as plus Treat L WCA as minus

Normally the pilot will use either a manual or electronic E6B Flight Computer to solve WCA problems. Consult your E6B computer manual for problem solution methods.


WCA for the Example Flight

The example flight from SVH, LEX, 3N8, SVH is shown below. The wind aloft for this problem is 270 degrees true at 35 knots. On your planning chart, add and subtract the WCA's to the TC's to fill out the TH column.

TC WCA TH
088 01 L 087
220 15 R 235
332 17 L 315
True Course, Wind Correction, True Headings (degrees)

Correcting for Magnetic Variation

As a refresher on Magnetic variation, see Magnetic Variation . True North and Magnetic North are not at the same location on the earth. In the eastern US, the Magnetic North Pole is west (left facing north) of the True North pole. The AGONIC LINE (where true and magnetic north are the same) runs from upper eastern Wisconsin, diagonally Southeastward through the central South Carolina coast. The difference between the True and Magnetic Norths is called Magnetic Variation (VAR). It is called Westerly Variation east of the agonic line; i.e. Magnetic north is west of True North. It is called Easterly Variation west of the agonic line.

To convert from TH to Magnetic Heading (MH), Add Westerly VAR, Subtract Easterly VAR. The variation is shown on the Aeronautical Charts as dashed magenta lines, running from the top to the bottom of the chart. They will be labeled 6W, 10E, etc.

In your planning log, write the magnetic variation down in the VAR column (denoted by the *). Add or Subtract the VAR (W = +, E = -) to the TH to get the Magnetic Heading (MH) values. This portion of the example SVH, LEX, 3N8, SVH flight is shown below. The flight is totally within a region where the Magnetic Variation is 6 degrees WEST.

TC WCA TH VAR (*) MH
088 01 L 087 06 W 093
220 15 R 235 06 W 241
332 17 L 315 06 W 321
Course, Headings, Wind Correction, Magnetic Variation (degrees)

This completes the Course and Heading definition of the log.

Distance and Time

As a by-product of the wind triangle calculations to arrive at a Magnetic Heading for each leg, you also found the Ground Speed for each leg. Using this GS, and the DIST (distance) for each leg (or segment) of the flight, the time and estimated fuel usage can be calculated.

DIST GS TIME FUEL RATE FUEL USE
32 139 :14 8.9 gph 2.0
31 78 :24 8.9 gph 3.5
26 83 :19 8.9 gph 2.8
Time, Distance, Groundspeed, Fuel Used per Leg