Aircraft Approaches

Approaches

• Two types of approaches:
  • Precision: Lateral and vertical guidance, approach light systems, and distance information (waypoints and beacons).
  • Non-Precision: Lateral guidance (left and right), may or may not include vertical guidance.
• Precision Approaches:
  • Instrument Landing System (ILS).
• Non-Precision Approaches:
  • Localizers.
  • VORs.
  • NDBs.
  • RNAVs (though some RNAVs provide vertical guidance).

Instrument Landing System (ILS)

• Most common type of precision approach.
• Provides lateral (localizer) and vertical (glide slope) guidance.
• Localizer:
  • Signal from the end of the runway; shoots a beam down the center.
  • Provides guidance on how far off from the centerline you are.
  • Orange T's are elements of the approach lighting systems.
• Glide Slope:
  • Vertical guidance; indicates above or below the 3-degree glide path.
  • Doesn't provide lateral guidance.
  • Ensures obstacle clearance on the way in.
• Localizer Signals:
  • Sends out two signals (A and B).
  • On-course indication: equal parts of signals A and B.
  • If off the centerline, one signal will be stronger, and the pilot will notice the course is off.
  • Localizer only gives lateral guidance, requiring step-downs.
• Localizer Location:
  • Located at the back end of the runway it serves.
  • Service area: Assured correct guidance indications within the depicted service area. Outside, no assurance.
  • Range:
    • 10 NM: 35-degree window.
    • 18 NM: 10-degree area.
• Localizer Course Width:
  • Ranges between 3 to 6 degrees, depending on the runway length.
  • Width is always 700 feet wide at the approach end of the runway.
  • Longer runways have narrower course widths; shorter runways have wider course widths.
• Glide Slope:
  • Works similarly to the localizer but provides vertical guidance.
  • Typically located to the side of the runway.
  • PAPI systems provide glide slope information.
  • Service area can stretch out to about 10 miles with a 27 degree width.
• Glide Slope Indicators:
  • Needle centered: on the glide path.
  • Needle lower than center: airplane is high.
  • Needle higher than center: airplane is low.
• Marker Beacons:
  • Alert pilot to location along the final approach course.
    • Outer marker beacon: Blue.
    • Middle marker: Final approach fix, 200 feet above the ground (decision height).
    • Inner marker: Airlines, decision heights for CAT II landings (lower visibility).
• Approach Lighting Systems:
  • Aid in transitioning between instrument and visual flight.
  • If the runway is not visible at minimums but the lights are, it counts as airport environment.
  • Allows descending to 100 feet above the touchdown zone elevation.
• Parallel ILS Approaches:
  • Simultaneous approaches to parallel runways.
  • Types:
    • Dependent parallels: Runways 511,000 feet apart; aircraft staggered 2,500 - 3,600 feet.
    • Simultaneous independent parallels: Runways 4,309,000 feet apart; aircraft may be parallel but must not encroach on the no transgression zone.
    • Simultaneous close independent parallels: Runways 7,300 feet apart; aircraft may be parallel, but ATC requires precision runway monitoring.

RNAV (Area Navigation) Approaches

• RNAV approaches are non-precision approaches.
  • GPS (Global Positioning System) is the most common type.

LPV and LNAV/VNAV Approaches

• RNAV approaches with vertical guidance.
• Flown like precision approaches but are technically non-precision for cost and paperwork reasons.
• Uses GPS guidance from satellites instead of ground-based systems.
• RNAV Zulu: Light precision, requires WAAS (Wide Area Augmentation System), decision altitude minimums.
• LPV/LNAV Approaches:
  • Use GPS satellites for lateral and vertical guidance.
  • Require an IFR-approved GPS and WAAS capabilities.

Localizer Approaches

• Same as an ILS approach but without vertical guidance (glide slope).
• Can be flown if the glide slope indication is lost during an ILS approach.

Localizer Back Course Approach

• The ACS recommends against doing localized back courses because they usually take place in VFR, and they kind of go back to an unsafe area potentially if there's a lot of VFR traffic.
• Uses the front course number published on the instrument approach plate.
• Localizer antenna sends signals from the reverse side, establishing a flyable non-precision approach.
• Back course approaches have reverse sensing (opposite needle indications).
• If the needle is getting to the right and you try to turn to the right, you're gonna get further off course.

LDA and SDF approaches

• LDA (Localizer Type Directional Aid):
  • Similar to ILS approaches, some provide vertical guidance.
  • Not aligned with the runway centerline.
• SDF (Simplified Directional Facility)
  • Similar to localizers and LDA approaches.

VOR Approaches

• VOR (Very High Frequency Omni-Directional Range).
• Use VOR radials to create approach courses to the runway.
• VOR Alpha: VOR is off the center of the runway.
• Non precision.

RNAV Approaches

• LNAV (Lateral Navigation).
• Again, stands for that area navigation while there are multiple types of systems.
• GPS is most common.
• Like precision approaches to the Yankees.

PAR Approach

• Precision Approach Radar
• Includes both lateral and vertical guidance to pilots making an instrument approach in the form of verbal instructions from ATC.

ASR Approach

• Airport surveillance radar
• Includes guidance to pilots making an instrument approach in the form of verbal instructions from ATC.
• They will give a series of headings and corrections to align your final approach with the extended centerline.
• Pilot will follow the series of step down altitude fixes and the descent.

No Gyro Approach

• Made when aircraft's gyroscopic driven instruments are inoperative.
  • Attitude indicator, heading indicator, etcetera.
• ATC gives verbal lateral guidance (