The Navigation Log (Nav Log) is a pilot’s foundational document for conducting cross-country flights. It serves as an organized record of pre-flight planning calculations, ensuring the aircraft can safely navigate from departure to destination while adhering to regulatory requirements. The log facilitates accurate fuel management and allows for systematic in-flight tracking of progress and performance. This article provides a procedural guide for filling out the Nav Log, detailing the necessary data inputs and calculation steps.
Gathering Essential Planning Materials
Before figures can be entered into the log, up-to-date source materials must be assembled. The primary geographical reference is the appropriate sectional chart, which details airspace, terrain, navigational aids, and magnetic variation. Precise calculations depend on current weather information, including METARs and TAFs for surface conditions, alongside the Winds Aloft Forecast.
Aircraft performance data is also required, detailing the true airspeed (TAS) maintained at the planned altitude and the specific fuel consumption rate. These figures are usually found in the aircraft’s Pilot’s Operating Handbook (POH). To perform the necessary calculations, a flight computer (E6B or electronic equivalent) and a navigational plotter are used to derive the required headings and speeds.
Defining the Route and Calculating True Course
Plotting the flight path on the sectional chart begins the transcription process onto the Nav Log. A long flight is broken down into smaller legs, generally defined by identifiable landmarks or navigational aids. These segments are often designed to keep durations between ten and twenty minutes to simplify tracking.
Once the route is segmented, the plotter is used to measure the distance of each leg in Nautical Miles (NM) and transfer that figure to the log. The plotter is then aligned with the route of flight to determine the True Course (TC), which is the angle of the intended track measured clockwise from True North. This measurement uses a nearby meridian line on the chart, which provides a direct reference to True North for the segment.
Incorporating Wind Effects and Determining Headings
The True Course represents the line drawn on the map, but the aircraft must compensate for the effect of wind. Compensation begins by obtaining the Winds Aloft forecast data for the specific altitude and region of each flight leg. The wind velocity and direction are entered into the E6B flight computer alongside the True Airspeed and the True Course.
The flight computer calculates the Wind Correction Angle (WCA), the angular offset required to keep the aircraft flying along the intended ground track. Applying the WCA to the True Course derives the True Heading (TH), which is the direction the aircraft’s nose must point relative to True North.
The next step is to convert the True Heading to a Magnetic Heading (MH) because the aircraft’s compass operates relative to Magnetic North. This conversion is accomplished by applying the local magnetic variation, the angular difference between True North and Magnetic North. Variation values are printed on the sectional chart along the isogonic lines and are added or subtracted from the True Heading depending on whether the variation is Westerly or Easterly. A final adjustment involves calculating the Compass Heading (CH) by applying the compass deviation, which accounts for magnetic interference within the aircraft.
Calculating Ground Speed, Time, and Fuel Consumption
The wind correction calculation on the E6B simultaneously yields the Ground Speed (GS), the actual speed of the aircraft across the surface of the earth. Ground Speed accounts for the headwind or tailwind component and determines the time required to complete the leg. This figure is transferred to the log and used to calculate the Estimated Time Enroute (ETE).
The ETE is calculated using the formula: Time equals Distance divided by Ground Speed for each leg. These individual ETE values are summed to find the total time required for the trip. The necessary fuel quantity for the segment is then calculated by multiplying the segment’s ETE by the aircraft’s known fuel consumption rate.
Pilots must calculate the cumulative fuel required and ensure the total includes a regulatory reserve. For flights conducted under FAA Part 91 regulations, this means carrying enough fuel to fly to the destination and then continue for an additional thirty minutes during the day or forty-five minutes at night. This reserve ensures compliance with safety regulations and provides contingency fuel for unexpected delays.
Recording Operational Data and Checkpoints
Beyond the core performance calculations, the Nav Log serves as a repository for all operational data required for the flight. A primary element is the selection and recording of prominent visual landmarks that serve as checkpoints. These checkpoints, such as identifiable towns or rivers, confirm the aircraft is tracking along the intended course and achieving the planned ground speed.
The log also requires dedicated space for recording radio frequencies necessary for navigation and communication. This includes frequencies for VOR navigational aids, Automatic Terminal Information Service (ATIS) for weather broadcasts, Common Traffic Advisory Frequency (CTAF) for non-towered airports, and Approach or Departure Control. Recording these frequencies prevents the need to search charts while managing the aircraft in flight.
The log must also include the Minimum En Route Altitude (MEA) or Minimum Safe Altitude (MSA) for each segment to ensure terrain and obstruction clearance. These altitude requirements are derived from the sectional charts and provide a reference for safe flight. A dedicated “Remarks” or “Notes” column allows the pilot to record specific reminders, such as airspace changes or emergency information like transponder codes.
Using the Nav Log In-Flight
The completed Nav Log transitions from a planning document to a dynamic tracking tool once the flight commences. The process involves systematically recording the Actual Time Over Checkpoint (ATO) as the aircraft passes each landmark. This actual time is compared to the Estimated Time Over Checkpoint (ETO) to assess the accuracy of the planning and the current performance.
Any significant difference between the ATO and ETO indicates that the actual wind or ground speed differs from the forecast. The pilot uses the updated performance data to revise the Estimated Time of Arrival (ETA) for the destination and subsequent checkpoints. Fuel tracking is managed by recording the actual fuel remaining at each checkpoint and comparing it against the planned fuel burn, providing a real-time check on endurance.
The pilot flies the calculated True Heading, which directs the aircraft to “crab” into the wind to maintain the desired ground track. If the aircraft drifts off course, the pilot uses the log’s data to make slight heading corrections. This continuous process of recording, comparing, and correcting ensures the flight remains efficient and adapts to the actual conditions encountered.
Final Review and Retention
Upon completion of the flight, the Nav Log remains a valuable document for regulatory compliance and post-flight analysis. Many operational regulations require the retention of flight planning records, often up to ninety days, to demonstrate due diligence. The completed log serves as a record of the pilot’s adherence to pre-flight preparation requirements.
Reviewing the completed log is an important step for refining future flight planning accuracy. By comparing the calculated figures, such as estimated ground speed and fuel burn, with the actual figures recorded in flight, the pilot can identify systematic errors in planning assumptions. This analytical review helps improve the pilot’s ability to forecast performance and select appropriate settings for subsequent flights.