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Instrument Approach Basics

Format​

  • Whiteboard
  • Example approach charts

Objective​

Develop an understanding of the common structure of an instrument approach procedure, and show how an approach chart describes that structure and information.

Timing​

60 minutes

Outline​

  • What is an instrument approach?
  • What are the common elements of an instrument approach?
  • Instrument approach charts - Non-precision approach
    • Margin information
    • Briefing strip
    • Plan view
    • Profile view
    • Minimums
  • Precision approach
  • How do we brief an approach

Content​

What is an instrument approach?​

An instrument approach is a procedure which can be used to place the aircraft in a position from where it can land at an airport.

Enroute phase > arrival phase > approach phase > landing

Two broad categories of approaches: Approaches with vertical guidance, approaches without vertical guidance

Structure of an IAP​

  • Transition routes, how do we get established on the approach
  • Final approach segment with some kind of navigational guidance (ILS, VOR, GPS)
  • Decision point: A point where we decide whether we are going to continue to land
    • Dictated by a set of minimums, which tells us the altitude and visibility we need to have the runway in sight, and be able to land safely
    • Also a set of criteria to ensure we can land safely
  • Missed approach procedure with a hold

Chart Components​

Non-precision approach example: KCVO VOR RWY 17

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  • Margin identification
    • City/State (top L)
    • Identifier and responsible agency (top C)
    • Last update date (top R)
    • Volume ID of TPP, effective dates (left C)
    • Procedure title (bottom R)
      • Typically with name of runway ILS 31
      • "VOR-A": Not aligned with a runway
      • RNAV 31 Z, Y: Multi approaches
    • Airport name (bottom R)
  • Briefing strip
    • Primary navaid: Frequency and channel (military user)
      • RNAV approaches will also have "WAAS" here for LP/LPV
    • Approach course: Magnetic course, altitude, distance
    • Runway length: 5100
    • Touchdown zone elevation: TDZE
    • Airport elevations
    • Procedure notes:
      • Non-standard takeoff mins
      • Non-standard alternate mins
      • What if there's an acronym here you don't recognize? TPP legend
    • Missed approach procedure
    • Frequencies
      • Star next to com frequency: Indicates part-time tower ops
      • Inverse L: Pilot controlled lighting
  • Planview
    • IAF: Initial approach fix, where the approach can be start
    • IF: Intermediate fix - indicates we are on intermediate segment, aligned with the runway
    • MSA: Minimum safe altitudes, for emergencies (+1000' clearance over all obstructions)
    • Obstruction: +/- means "doubtful accuracy"
    • "RADAR REQUIRED"
    • Marker beacon: Outer, middle, and inner
  • Profile view
    • Approach descent angle: 3.2, TCH = Threshold crossing height
    • FAF: Maltese cross
    • Missed approach point: For non-precision it is the last waypoint
    • VDP: V symbol near the runway, point at which the approach descent angle from the touchdown zone intercepts the MDA
  • Airport sketch
    • Lighting systems
      • See Approach Lighting Systems
      • MALSR: Medium-intensity approach lighting system
      • V = VASI
      • A5 = 5 lead-in strobes
      • Inverted V and A5 = pilot controlled lighting
    • Timing stable for different ground speeds
      • Used for timing the missed approach point
  • Landing minimums
    • Airport categories: VREF or 1.3 * VS0
      • A: Less than 91 knots
      • B: 91 knots - 120 knots
      • C: 121 knots - 140 knots
      • D: 141 knots - 165 knots
      • E: 166 knots or more
      • See TPP supplement pg. 4 for category speeds
    • "S-ILS 33L" - Straight in for 33L
    • Altitude and visibility requirements
      • Big numbers:
        • Minimum descent altitude (MDA) or decision altitude (DA)
        • Minimum visibility in s.m.
        • RVR in 100's of feet, can be converted to s.m. (TPP supplement pg. 5) - See KSLE RNAV 31 for RVR
      • Small numbers: MDA/DA in height about runway threshold

Visual Descent Points (VDPs)​

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  • Used on non-precision approach charts
  • Tells you the last point where a descent to the runway can be made at the established (often, but not always, aligning with the angle of the PAPI/VASI)
  • For 3° slope: (Minimum descent height) / 300 = Distance in nm to VDP
  • Example: KCVO VOR 17
    • VASI 3° angle: (632 MDH) / 300 = 2.1nm
    • Approach angle 3.2°: (632 / 354) = 1.8
  • Depending on our aircraft, we should treat the VDP as the MAP
    • A 172 may be able to make a safe approach and landing at >3° descent angle
    • A Cirrus or a King Air should probably make a missed approach
    • Reminder that we need to land using normal maneuvers

Other Approach Charts​

Precision approach: KMFR ILS or LOC RWY 14

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Procedure turn: KSPB VOR-A

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Hold-in-lieu of procedure turn: KSLE RNAV 31

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Briefing an approach​

Basic flow: Top left to bottom rate of the chart Example: KSLE RNAV 31, DIYAT to NECIP, LPV

W-WIRE: Weather, waypoints, instruments, radios, everything else

  • Confirm approach name and chart currency
  • NAVAIDs: Tune and identify
  • Landing distance available, TDZE, airport elevation
  • Procedure notes: Inoperative equipment
  • Approach lighting system
  • Tune COM frequencies
  • Brief procedure entry
    • Set procedure course in OBS
    • Describe the procedure turn or hold-in-lieu of procedure turn
    • Initial altitude restrictions
  • Brief minimums for approach speed
  • Missed approach procedure
  • Any questions?

References​