Chapter 6 - Navigation

Navigation: <- Previous Chapter 5 Overview Chapter 6 Next -> Chapter 7

This chapter is an expanded exam-and-flight-practice reference for PPL navigation. It combines core theory, formula memory aids, worked examples, and cockpit decision flow.

6.1 Earth Geometry and Direction Basics

Why this matters

Navigation starts with a geometric model of Earth. Most exam mistakes in this area come from mixing latitude and longitude distance rules.

Core concepts

Graphic: GC vs RL concept

flowchart LR
    A(Point A) -->|Great Circle: shortest| B(Point B)
    A -->|Rhumb Line: constant heading| B

Key constants

Quantity Value Notes
Earth circumference 21,600 NM 360 deg x 60 NM
1 deg latitude 60 NM Always true (for navigation use)
1 NM 1.852 km ICAO standard
1 kt 1 NM/h Speed unit in navigation

6.2 Latitude, Longitude, and Distance Calculations

Latitude distance

\[\text{Distance (NM)} = \Delta \text{Lat (deg)} \times 60\]

or in minutes:

\[\text{Distance (NM)} = \Delta \text{Lat (min)}\]

Longitude distance (Departure)

\[\text{Departure (NM)} = \Delta \lambda \text{ (min)} \times \cos(\text{Mean Lat})\]

Where:

Worked example

Exam trap

6.3 Time Discipline (UTC, ETA, ETO)

Quick formulas

\[\text{Time (hr)} = \frac{\text{Distance (NM)}}{\text{GS (kt)}}\] \[\text{Fuel used} = \text{Fuel flow} \times \text{Time}\]

6.4 Tracks, Headings, Drift, and Wind Triangle

Definitions

Graphic: wind triangle logic

flowchart TD
    W[Wind vector] --> R[Resultant ground vector]
    A[TAS and Heading vector] --> R
    R --> GS[Groundspeed]
    R --> TMG[Track Made Good]

Practical sequence (DR planning)

  1. Plot true track (TT).
  2. Apply WCA from forecast wind -> true heading (TH).
  3. Apply variation -> magnetic heading (MH).
  4. Apply deviation -> compass heading (CH), if required.
  5. Compute GS and leg ETE.

Sign reminder

6.5 Compass, Variation, and Deviation

Types of north

Type Meaning Used for
True North Geographic pole reference Charts, true tracks
Magnetic North Earth magnetic field reference Magnetic headings/bearings
Compass North Aircraft compass indication Compass steering

Conversion chain

\[\text{True} \pm \text{Variation} = \text{Magnetic} \pm \text{Deviation} = \text{Compass}\]

Memory aid: True Virgins Make Dull Company.

Worked conversion

6.6 Earth Convergence and Conversion Angle

Earth convergence

\[Cv = \Delta \lambda \times \sin(\text{Mean Lat})\]

Where:

Conversion angle (commonly used with Lambert assumptions)

\[CA = \frac{1}{2} Cv\]

RL from GC relationship

\[RL = GC \pm CA\]

Worked example

6.7 1-in-60 Rule and Track Error Correction

Formula set

\[\text{Track Error (deg)} \approx \frac{\text{Off-track (NM)} \times 60}{\text{Distance flown (NM)}}\] \[\text{Closing Angle (deg)} \approx \frac{\text{Off-track (NM)} \times 60}{\text{Distance to go (NM)}}\] \[\text{Total correction} \approx \text{Track Error} + \text{Closing Angle}\]

Fast mental anchor

Worked example

6.8 Wind Components and Runway Use

Given angle $\theta$ between runway heading and wind direction:

\[\text{Crosswind} = W \times \sin\theta\] \[\text{Head/Tailwind} = W \times \cos\theta\]

Clock code estimates

Relative angle Factor
15 deg 0.25
30 deg 0.50
45 deg 0.70 to 0.75
60 deg or more ~1.00 (for crosswind mental estimate)

Operational reminders

6.9 Chart Projections (Exam Focus)

Mercator

Lambert Conformal Conic

Polar stereographic

Comparison table

Projection Straight line on chart Best use Main trap
Mercator Rhumb line Low-mid lat marine/general nav Assuming straight line is shortest
Lambert Approx GC over operational ranges Aviation enroute charts Forgetting residual distortion
Polar stereographic Depends on grid/plot method Polar operations Ignoring grid reference conversions

6.10 Grid Navigation and Grivation (Advanced awareness)

At high latitudes, true/magnetic references become difficult due to meridian convergence and magnetic behavior. Grid references provide a stable operational framework.

\[\text{Grivation} = \text{Grid Convergence} + \text{Variation}\]

Use these terms for conceptual exam questions, even if not heavily used in basic PPL route flying.

6.11 Radio Navigation Essentials (PPL level)

NDB/ADF

VOR

DME

6.12 GNSS/GPS Practical Use and Risk Management

Core operating points

Pilot discipline

6.13 Navigation Log and In-Flight Replanning

Minimum useful nav log fields

Leg item Why it matters
Planned track and heading Baseline steering reference
Distance and planned GS Planned ETE and fuel
Actual time overhead checkpoints Real GS trend
Revised ETA and fuel remaining Diversion decision quality
Frequencies and airspace notes Workload and compliance management

In-flight update loop

flowchart LR
    A[Checkpoint time] --> B[Recompute GS]
    B --> C[Update ETA and fuel]
    C --> D{Trend acceptable?}
    D -- Yes --> E[Continue and monitor]
    D -- No --> F[Divert early]

6.14 Lost Procedure and Repositioning

Priority order:

  1. Aviate (safe altitude, stable control).
  2. Navigate (fix position).
  3. Communicate (seek ATS/FIS assistance early).

Typical practical sequence:

6.15 Human Factors and Error Management

Common traps:

Countermeasures:

6.16 Formula Pack (Quick Revision)

Topic Formula
Latitude distance $D = \Delta Lat(\deg) \times 60$
Departure $Dep = \Delta Long(\min) \times \cos(\text{Mean Lat})$
Time $t = D/GS$
Fuel used $Fuel = FF \times t$
Earth convergence $Cv = \Delta \lambda \times \sin(\text{Mean Lat})$
Conversion angle $CA = 0.5 \times Cv$
1-in-60 track error $TE = Off \times 60 / Flown$
Closing angle $CA_{close} = Off \times 60 / ToGo$
Crosswind $XW = W \sin\theta$
Head/tailwind $HW/TW = W \cos\theta$

6.17 Common Exam Traps

6.18 Quick Study Plan (High Retention)

  1. Memorize formula pack by writing from memory daily.
  2. Do mixed 10-question blocks: wind, conversion, chart, timing.
  3. Explain each result in words (“why this sign?”, “why this correction?”).
  4. Rework all wrong questions after 48 hours.
  5. Practice tidy wind-triangle drawing under time pressure.

References

Navigation: <- Previous Chapter 5 Overview Chapter 6 Next -> Chapter 7
prepared by Raptor K