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06-A: Pilotage and Dead Reckoning

Knowledge

K1: Pilotage and dead reckoning

  • to track progress during dead reckoning without radio,
    • use pilotage and keep track of checkpoints
  • to avoid getting lost
    • refer to ground features and checkpoints
    • deviate from planned headings as needed

K2: Magnetic compass errors

  • magnetic variation: angular difference between true north and magnetic north

  • Magnetic compass

    • Accurate only during straight-and-level, unaccelearted flight
    • Components
      • Kerosene-like liquid
      • Pivot
      • Compass card
      • Housing
      • Lubber line

    • Compass errors

      • advantage over other instruments (heading indicator)
        • self-powered
        • north-seeking without drift
      • Variation
        • Discrepancy between true north and magnetic north
          • True north: geometrical center
          • Magnetic north: time-variable location of the earth’s magnetic field north
        • Correction
          • Via isogonic lines in the sectional
          • “East is least (subtract), best is west (add)”
      • Deviation
        • Error from aircraft-induced magnetic field (avionics, engine)
        • Correction via compass correction card (for heading… steer )
      • Horizontal compass card (inverted scale from pilots view, because we basically “x-ray” through the card)
        • Dip error: turning errors due to the dip effect
          • Occurs when turning TOWARD north or south
          • Reason
            • The magnetic field lines are not parallel to the surface
          • Correction via deliberate overshooting and undershooting when turning TOWARD
            • Mnemonic: OSUN on the northern hemisphere
              • LeadOS
              • LagUN
              • Overshoot south (because the compass leads southerly, so I have to go further than it shows)
              • Undershoot north (because the compass lags northerly, so I have to stop earlier)
            • Lead and lag degree Formula
              • Overshoot and undershoot by the same value
              • Rule 1
                • Latitude plus half bank
              • Rule 2
                • Half latitude plus 15
        • Dip error: acceleration errors (is this the same on the southern hemisphere)
          • On both an easterly and westerly heading (mnemonic: ANDS)
            • Accelerating the aircraft moves the needle north (AN)
            • Decelerating the air staff moves the needle south (DS)
            • does not affect north/south headings and decays in-between
      • Vertical compass card
        • Turning errors due to dip effect, correction when turning FROM north and south
        • Same OSUN rule as above but when turning FROM the respective heading

      • When initiating a turn from a northerly heading, the compass lags again (LagUN), so it will turn in the opposite direction, e.g.,

        • if a right turn is entered from a north heading, the compass will initially inidicate a turn toward the west
        • if a left turn is entered from a north heading, the compass will initially inidicate a turn toward the east

      • The FAA questions only ask about turns starting FROM a northerly/southerly heading away to an east/west heading

      • Best to use LagUN (LagUN = lag & undershoot north, thus lead and overshoot South)
        • lagging initially means opposite turn
      • In all cases, NOSE works well
        • NO: North opposite
        • SE: South Exaggerate
      • This is equivalent to OSUN as defined above
      • I am not sure if the rules
        • Apply when turning TO a northerly/southerly heading
        • Are different/applicable for a vertical compass card

    • Usage

      • True north
        • Maps (otherwise maps would have to be updated all the time because magnetic north wanders)
        • METARs and all other written weather reports (The weather man never lies!).
      • Magnetic north
        • Runway designations (runway numbers are updated and repainted regularly)
        • ATC instructions
        • Altitude-for-course requirements: magnetic courses (NEOOD, SWEVEN)
        • ATIS wind indications
      • Unclear

  • definitions

    • directions
    • heading
    • bearing
    • course
    • (wind) (ground) track
    • desired track

  • relationships

    • we want course and wind ground track track to be the same

  • Magnetic bearing vs true course

    • Magnetic variation
      • west is best, east is least
      • Add west variation, subtract east variation
      • East variation is found west of the agonic line
      • West variation is found east of the agonic line
    • Wind correction angle (mnemonic: number line from left to right)
      • Left correction angles have to be subtracted
      • Right wind correction angles have to be added
    • Dip errors

K3: Topography

K4: Selection of approriate

K4a: Route

  • airways

    • when changing altitude
      • execute gentle banks, left and right, for continuous visual scanning of the airspace

  • airport

    • airport diagram
      • star somehwere on the diagram in black
    • VFR Sectional
      • start around the runways in magenta/blue

K4b: Altitude

  • true altitude (MSL)
  • absolute altitude (AGL)
  • indicated altitude (altimeter reading)
  • pressure altitude
  • Indicated Altitude + (29.92 − Altimeter Setting) x 1000
  • assumption: lapse rate of 1 inHg per 1000 feet
  • density altitude
  • ISA Temp: 15 − ((Pressure Altitude / 1000) x 2)
  • Density Altitude: Pressure Altitude + 120 x (Outside Air Temp − ISA Temp)

  • flight level

  • Figure 22

    • mountaineous terrain may cause the altimeter to indicate an altitude of 1000 ft or more higher than the actual altitude (causing you to fly low)
    • mountain clerance altitude: 2000 ft above peak
      • find highest elevation in the sector andround up
      • add 1000 for maintaing legal minium altitude
      • add 1000 for altimeter error and downdrafts

K4c: Checkpoints

K5: Plotting a course, including

K5a: Determining heading, speed, and course

  • Given
    • intended crossing at A: 1500h
    • intended crossing at B: 1530h
    • distance: 70 NM
    • wind: 310 at 15
    • 8000ft
    • temperature -10 °C
    • true course 270°
  • computed
    • required ground speed: 140 kts
  • TAS from E6B/CX3 computer wind correction function (gs, wspd, wdir, tc)
    • 151.80 TAS
  • CAS from E6B/CX3 computer wind correction function (TAS, OAT, PAlt)
    • 137.15

K5b: Wind correction angle

  • given
    • true heading 135°
    • ground track 130°
    • airspeed 135 kts
    • groundspeed 140 kts
  • analysis
    • true heading > ground track, thus winds from the right.
    • groundspeed > airspeed, thus tailwind, winds must be larger than 135° + 90° = 225°

  • answer

    • only answer greater than 225°: 245° at 13 kts

  • crab into the wind to counteract it

K5c: Estimating time, speed, distance

  • distance flown = ground speed x time

  • Figure 20

      • departure, hampton roads aiport, 1456
      • crossing chesapeake municipal, 1501
    • given
      • hampton to cheasapeake, 9 NM
      • chesapeake to first flight, 50NM
    • computed
      • current ground speed, 108 kts
      • ETA, 0.463h = 28min, 1501 + 28min = 1529

  • time zone (Figure 27)

    • departure, 1030PST, 1030PST + 8h = 1830Z
    • 4h flight
    • arrival 1830Z + 4h = 2230Z,

K5d: True airspeed and density altitude

K6: Power setting selection

K7: Planned calculations versus actual results and required corrections