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A helicopter approach path indicator (HAPI) is a visual glideslope indicator (VGSI), providing visual vertical course and descent cues for pilots. A HAPI system consists of:

  • 4 identical light units (type L-880) or 2 identical light units (type L-881)
  • A power control unit for style A systems only
  • Aiming and calibration equipment (may be part of the light units)


PAPI units may be voltage powered (style A) or current powered (style B).
Class I systems operate -31 to 131° F (-35 to 55° C) whereas class II systems operate -67 to 131° F (-55 to 55° C).


While VSGs are optional for helipads, provide one if:

  • Obstacle clearance, noise abatement, or traffic control procedures require a particular slope.
  • The environment of the heliport provides few visual surface cues.





Install a visual approach slope indicator (VASI) to serve the heliport approach to a heliport if one or more of the following conditions exist, especially at night:

  • Obstacle clearance, noise abatement or traffic control procedures require a particular slope.
  • The heliport environment provides few visual surface cues.
  • The characteristics of the helicopter require a stabilized approach.


A standard VASI for helicopter operations consists of the following:

  • PAPI and APAPI systems conforming to the Annex 14, Volume I specifications, except that the angular size of the on-slope sector of the systems shall be increased to 45 minutes; or
  • Helicopter approach path indicator (HAPI) system conforming to Annex 14, Volume I specifications.


The HAPI signal format includes 4 discrete signal sectors, providing an “above slope”, an “on slope”, a “slightly below” and a “below slope” signal. The signal repetition rate of the flashing sector should be at least 2 Hz.


Light Distribution

Sector Color and Format
Above Flashing Green
On Slope Green
Slightly Below Red
Below Flashing Red

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