VFR Flight Planning, Nav Log Preparation, and Navigation Calculations

Fundamentals of VFR Navigation

• Pilotage: Navigation solely by visual reference to landmarks and checkpoints on the ground.

• Dead Reckoning: Navigation by mathematical calculations utilizing course, true airspeed, ground speed, wind corrections, and elapsed time.

• Visual Checkpoints:

  • Optimal spacing along a route is typically $10$ to $15\,\text{miles}$ (or $10$ to $20\,\text{miles}$).

  • Spacing under $5\,\text{miles}$ creates excessive cockpit workload; spacing beyond $15\,\text{miles}$ increases the risk of disorientation.

  • Features include roads, freeways, lakes, bridges, and towns, placed either directly on course or abeam.

  • Charted city borders accurately represent lighted shapes visible at night.

VFR Flight Planning and Nav Log Structure

• Plotting Tools: Navigation utilizes a VFR sectional chart, a plotter for measuring courses and distances, and an approved flight computer (such as a CX-3 or mechanical E6B).

• Nav Log Waypoint Sequence:

  • Departure airport.

  • Top of Climb (TOC).

  • En route checkpoints.

  • Top of Descent (TOD), calculated to the destination Traffic Pattern Altitude (TPA) found in the Chart Supplement.

  • Destination airport.

• Direct Routing: A straight route simplifies nav log calculations; zigzagging requires individual course and heading calculations for each leg.

Altitude Selection and Weather Interpolation

• VFR Cruising Altitudes (Above $3,000\,\text{ft}\,\text{AGL}$):

  • Magnetic course $000^\circ$ to $179^\circ$ (East): Odd thousands + $500\,\text{ft}$ (mnemonic: NEODD).

  • Magnetic course $180^\circ$ to $359^\circ$ (West): Even thousands + $500\,\text{ft}$ (mnemonic: SWEVEN).

• Atmospheric Lapse Rate & Interpolation:

  • Standard sea-level temperature is $15^\circ\text{C}$, decreasing at a standard rate of $2^\circ\text{C}$ per $1,000\,\text{ft}$.

  • En route winds and temperatures aloft are interpolated between reporting stations and altitudes for the climb, cruise, and descent segments.

• Pressure Altitude Conversion: Calculated using the altimeter setting ($1\,\text{inch Hg} = 1,000\,\text{ft}$ difference from standard $29.92\,\text{inches Hg}$).

Aircraft Performance and Airspeed Calculations

• Cruise Performance Charts (POH Section 5):

  • Input variables: Pressure altitude, temperature deviation from standard, and engine RPM.

  • Output data: True Airspeed (TAS) and fuel consumption in gallons per hour (GPH).

• Climb Performance Charts:

  • Input variables assume maximum gross weight ($2,550\,\text{lbs}$), full throttle, flaps up, and standard temperature.

  • Chart conditions mandate adding $1.4\,\text{gallons}$ for engine start, taxi, and takeoff.

  • Performance charts assume zero wind; distances must be recalculated using actual ground speed.

Heading and Course Corrections

• True Course ($\text{TC}$): Measured clockwise from True North on the sectional chart using a plotter and a meridian of longitude.

• True Heading ($\text{TH}$):   $\text{TH} = \text{TC} \pm \text{Wind Correction Angle (WCA)}$

• Magnetic Heading ($\text{MH}$):   $\text{MH} = \text{TH} \pm \text{Magnetic Variation}$

  • Subtract East variation; add West variation ("East is least, West is best").

• Compass Heading ($\text{CH}$):   $\text{CH} = \text{MH} \pm \text{Compass Deviation}$

  • Deviation is obtained from the aircraft compass card; deviation is $0^\circ$ in aircraft equipped with a Horizontal Situation Indicator (HSI) driven by a remote wing-mounted magnetometer.

Questions & Discussion

• Circumnavigating Airspace Threats:

  • Prompt: When approaching jump activity near Cottonwood Airport, should a direct route divert to the left or right?

  • Response: Divert to the right to avoid high terrain (such as the $7,880\,\text{ft}$ mountain near Jerome), wilderness areas, and hang glider activity located to the left.

• Permissible Testing Calculators:

  • Prompt: What calculating device is legally permitted on the FAA written exam?

  • Response: Cell phones are strictly prohibited; only standard basic calculators issued at the testing center or dedicated aviation electronic flight computers like the CX-3 are allowed.

• Standard Temperature Calculations at Altitude:

  • Prompt: What is standard temperature at $5,000\,\text{ft}$ MSL?

  • Response: Standard temperature drops $2^\circ\text{C}$ per $1,000\,\text{ft}$, losing $10^\circ\text{C}$ from standard sea level ($15^\circ\text{C}$), resulting in $5^\circ\text{C}$.

• Aircraft Weight Assumptions on Charts:

  • Prompt: How does operating below the chart gross weight affect performance values?

  • Response: Climb charts are based on the absolute maximum gross weight ($2,550\,\text{lbs}$); operating at lower weights improves performance over the charted baselines.

• Compass Deviation Values:

  • Prompt: What is the compass deviation correction for an aircraft with a glass cockpit and wing magnetometer?

  • Response: Deviation is always $0^\circ$ because the HSI connects to a remote magnetometer isolated from cockpit magnetic interference.