"NAVLOG?? What is this witchcraft??" - Every student pilot born after 2000
Yes, I know you have an Electronic Flight Bag (EFB). Garmin Pilot or ForeFlight give you all you need to know for a cross country flight. But do you know how it works? What is the math behind this mystical tool that determines your ETA and fuel requirements?
All private pilots should be able to complete a NAVLOG. There, I've said it. And the reason for it is that the principles of navigation that it entails are at the very basics of pilotage. The below NAVLOG was developed by me to offer a comprehensive preparation for a VFR cross country flight. It's a template, so if you have any recommendations on improving it, please let me know! An example of improvements is the C-O-N that my ex-student Anthony came up with. These are cautions, observations, and NOTAMs that apply to the flight. For example, if you will navigate through a MOA, he would note it there.
Don't remember how to do one? Here is a quick step-by-step guide.
How to Complete a VFR NAVLOG
GOAL: To identify an acceptable route with sufficient visual references to navigate and to calculate the magnetic heading, time enroute, and fuel requirements to complete said route.
PLOT A COURSE (line over the ground) between your origin and destination airports. Here it's seen on SkyVector for explanatory purposes. Let's fly from KSAV to KCHS. You can plot this line on your EFB or Skyvector. A straight line is the simplest example. Of course, this might not always be that simple: restricted, prohibited airspaces, etc., but the same principles apply.
IDENTIFY VISUAL WAYPOINTS between your origin and destination. These are visual "checkpoints" to help you guarantee you are on the right path and serve the purposes of performance verification. In the NAVLOG you will calculate how long it should take you not only to reach your destination, but each checkpoint as well. If you are slower, faster, etc. that will determine whether your performance needs to be re-evaluated (and for example, you need a fuel stop you hadn't predicted). Note that these NAVLOGs are intended for longer, complicated flights, not just a quick flight where you clearly have more than enough fuel. But it's an academic exercise, so we have to suffer through it. In the perfect world, your waypoints are close enough so that you can see the ensuing one while you're over your next one (so you can't get lost). But this is dependent on the presence of visual markers. Choose something recognizable, clearly visible... roads, golf courses, coasts, rivers, etc. In the below example, we chose as the first two waypoints a highway right by the town of Okatie, and the Beaufort MCAS airport. These work for both day and night conditions. You then enter these waypoints int he NAVLOG. Eventually, as you become more proficient, you also add Top of Climb and Top of Descent (TOC/TOD) as waypoints. These are provided in the POH or can be calculated using rules of thumb (e.g. recommended cruise climb speeds).
IDENTIFY USEFUL NAVIGATIONAL AIDS (NAVAIDS) as an aid to your visual flying. In the case of VFR, the VORs need to be located on or near the field to provide useful guidance. If they are not, you can still note them in order to help you orient yourself in case you get lost. And if there are none, you can just leave the column blank. In our example, KSAV has a NAVAID: a VORTAC with identifier SAV and frequency 115.95. If we were to fly our route, this would match a ~058 degree radial outbound (note that this is in magnetic, not true). Let's then populate the following two columns: VOR and VOR Course with this information.
Useful tip: If you cannot fly a straight line for your route, try selecting VORs as your route turns - as long as they match with a visual reference. This way you back up your turn with VOR navigation. In the below example, the CRG VOR is chosen as a waypoint to turn right. The VOR is over the KCRG airport - which is a great visual landmark.
CHOOSE AN ALTITUDE consistent with direction of travel and safety of flight. If your overall route travels to the west, you will choose a VFR cruising altitude of even-thousand feet and add 500. If it travels east, you will choose an odd-thousand feet and add 500. Make sure to consider airspaces and obstacles as well. For the latter, console the Maximum Elevation Figure (MEF) which is present on each grid of lat/long on the sectional. In our case, 1700 is the highest MEF for our route. The MEF is calculated in one of two ways. The most obvious is the highest manmade obstacle (e.g., tower), rounding it to the highest next hundred feet, and adding 100 ft for error. So in our first quadrant, we have an obstacle 1,548 ft high. Rounding it to 1,600 and adding 100 for error gives us the MEF of 1,700 ft. Note also that cruising altitudes begin 3,000 ft AGL. Remember that FAR 91.119 doesn't only provide requirements for altitude above populated or non-populated areas. It also says you must fly an altitude that will not cause undue hazard to people in the event of an emergency landing due to engine failure. For our flight, let's say 5,500 ft (East bound = odd + 500). For the TOC, I wrote CLIMB to emphasize that between origin and TOC I'm obviously climbing and not cruising.
IDENTIFY WINDS AND TEMPERATURES ALOFT to calculate the difference between course (line over the ground) and heading (where the nose points). We will do that math in a later column. Official winds aloft and temperature data should be used from AviationWeather.gov.
DETERMINE YOUR TRUE AIRSPEED from the aircraft POH. This will be typically in the form of a table or graph and is a function of Power Setting (RPM). Note that on the VFR NAVLOG as well. That value is for cruising only, not climb or descent. Your POH might have dedicated tables with this information or you may just need to use rules of thumb. I for example consider a TAS of 85 kts for a climb. But, for the images below, I inserted 120 kts to keep the math simple (and cause writing this tutorial is as pleasurable as doing the NAVLOG itself...).
DETERMINE YOUR TRUE COURSE by either using a plotter on a paper chart (archaic, I know, right??) or by finding the desired track over the ground from your EFB. Note that the sectional chart is in True North. That is why we need to find the desired course in true (not magnetic). This is ~053 degrees true for our route.
CALCULATE YOUR WIND CORRECTION ANGLE (WCA) and USE IT TO CONVERT YOUR TRUE COURSE (TC) TO TRUE HEADING (TH) using an E6B, navigation computer, or other source. I recommend you at least learn how to use a manual E6B. Plus it makes you look cool. And Spock used it once, as my friend Conor reminded me. My E6B skills yield a wind correction angle f 1 degree left. As the NAVLOG reminds you, left is negative and right is positive. So that will be a -1 WCA. If we subtract 1 degree from our TC we get a TH of 052.
IDENTIFY YOUR MAGNETIC VARIATION and USE IT TO CONVERT YOUR TRUE HEADING (TH) TO MAGNETIC HEADING (MH). The magnetic variation is found on the VFR sectional by dashed magenta lines. These will have a degree East or West. As the NAVLOG reminds you, you subs tact east and add west. In our area, the variation is 7 degrees west (so +7). If we add 7 to our TH we get a MH of 059.
CALCULATE YOUR CORRECTED HEADING (CH) if your airplane only has a standard magnetic compass with a compass deviation card. If you don't (e.g., you have a PFD), then you stop right here, and your CH equals your MH. Every airplane needs to have a magnetic compass, so you can always do the extra step of finding it off the deviation card. This will be tail number specific, of course.
CALCULATE TOTAL AND LEG DISTANCE IN BETWEEN EACH WAYPOINT using a plotter on a sectional or using your EFB. Under the leg distance determine what is the remaining total distance (remaining distance - leg distance). For TOC, consider a 500 ft/min climb at an appropriate ground speed (see next steps below) and then return to this step to complete all the other waypoints.
CALCULATE ALL OF YOUR ESTIMATES for ground speed, time enroute, time of arrival, and fuel required. These are found as follows: A. GROUND SPEED: use the E6B or digital E6B by converting the true airspeed to ground speed (this is wind dependent). B. TIME ENROUTE: use the E6B or digital E6B. Time enroute is labeled as HH+MM where H is hours and M is minutes. So a 1 hour 20 minute ride is 01+20. Keep in mind that Speed = Distance / Time. So if you have speed and distance, you can calculate time. C. TIME OF ARRIVAL: choose a departure time (e.g., 08:00L) and for each waypoint find what is the ETA. D. FUEL REQUIRED: Using your E6B, find how much fuel you need. The POH will provide you with fuel flow, which for a Cherokee is ~10 GPH at cruise. The POH will also provide an estimate of fuel consumption on the ground for engine start and taxi. In the example below, that is 1.3 gal.
ADD UP YOUR TOTALS to find our your destination ETA and total fuel requirement. In this abbreviated case, the requirements to reach Beaufort (at cruise) are the following: ETE = 0+20, ETA = 08:30, Fuel Required = 3.5 gal.
DETERMINE THE ACTUALS IN FLIGHT. While flying you will note any deviation so that at every waypoint you can compare actual performance compared to your estimated. If indications are very different you have a warning that something may be off (unexpected winds, vectors, etc.).
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