Helicopter PAPI

The Helicopter PAPI (H‑PAPI) is a visual approach slope indicator system specifically designed for helicopter operations. It is structurally similar to the standard four‑unit PAPI used on fixed‑wing runways, but with a key difference: the glide path angle is set significantly steeper, typically between 4° and 6° (compared to the standard 3° for fixed‑wing). This steeper angle accommodates the typical descent profiles of helicopters, which often approach landing zones with a higher rate of descent and a steeper approach path.

Helicopter PAPI is installed at helipads, heliports, and helicopter landing zones (HLZs) to provide pilots with a clear, visual indication of their position relative to the correct approach slope. It is particularly valuable in low visibility conditions, at night, and in confined areas where terrain or obstacles require precise glide path control. The system uses the same red/white colour transition as standard PAPI, making it intuitive for pilots already familiar with the technology.

Helicopter PAPI exists because a standard 3° fixed-wing glide slope doesn't match how helicopters actually fly an approach — rotary-wing aircraft typically descend more steeply and into confined landing zones where a shallow, extended approach path may not be physically available due to terrain or obstacles. Without a glide indicator matched to that steeper profile, a helicopter pilot would have to judge the correct descent angle by eye alone, which is far less reliable at night, in poor visibility, or when the landing zone is surrounded by buildings, wires, or rising ground.

By using the same intuitive red/white colour logic as fixed-wing PAPI but calibrated to the steeper angle helicopters need, H-PAPI lets pilots already trained on standard visual glide slope indicators apply that same skill directly to helicopter operations, reducing the risk of a too-high or too-low approach into a landing zone with little room for correction.

Helicopter PAPI is deployed on a variety of helicopter landing sites:

• Heliports – providing standard visual glide slope guidance for commercial and private helicopter operations.
• Hospital helipads – ensuring precise approaches for emergency medical services (EMS) in confined urban environments.
• Offshore helipads – on ships or oil platforms where a steeper approach is often required.
• Military helicopter landing zones – supporting tactical and training operations.
• Confined area helipads – where obstacles require a steeper approach angle.
• As a complement to GPS/RNP approaches – providing visual backup for instrument approaches.

The wing bar is mounted to one side of the final approach and take-off area (FATO) or helipad touchdown point, positioned much closer in than a fixed-wing PAPI installation to suit the steeper helicopter approach angle and the confined dimensions of most helicopter sites. Units are set out on a survey tied to the FATO centreline and touchdown point, at a lateral offset and setback chosen to place the on-slope indication over the aiming point at the design approach angle (commonly steeper than the standard 3°, and adjustable for confined or obstacle-limited sites). Mounts are typically lower-profile than runway PAPI, and on rooftop or offshore helipads may be deck-mounted rather than on a frangible ground coupling, since impact frangibility requirements differ from runway environments. Cabling runs back to a compact constant current regulator suited to the shorter circuit lengths typical of helipad installations.

Helicopter PAPI operates on the same principle as standard PAPI, but with a steeper glide path angle and specific installation considerations for helipad environments:

• Optical Design: Each light unit contains a lamp (halogen or LED) and a precision optical system that projects a beam with a distinct red/white transition. The transition angle is set to the desired steep glide slope (typically 4°–6°).
• Colour Indication: The four‑light display provides the same intuitive red/white combination as standard PAPI:
  • All white – aircraft is well above the glide path.
  • 3 white / 1 red – slightly above the glide path.
  • 2 white / 2 red – on the correct glide path.
  • 1 white / 3 red – slightly below the glide path.
  • All red – well below the glide path.
• Steeper Glide Path: The steeper angle (4°–6°) allows helicopters to clear obstacles more effectively and follow a descent profile that aligns with typical helicopter approach procedures. The angle is adjustable to suit specific site requirements.
• Power and Control: Helicopter PAPI units are powered from the constant current series circuit (often a dedicated circuit) via isolating transformers, with intensity controlled by the CCR (typically 3‑step or 5‑step). Brightness can be adjusted for day, twilight, and night operations.
• Integration: Helicopter PAPI is typically deployed independently or integrated with the helipad lighting system and ALCMS. It may be combined with other approach aids such as the Helicopter Approach Path Indicator (HAPI) or visual docking guidance systems.

Helicopter PAPI shares the same control architecture as standard PAPI — the glide path signal is fixed optically per unit, not switched electronically. Each of the four units is levelled and its lens/shutter tilted so its red/white transition sits at a specific elevation, with the four angles set apart to straddle the steeper 4°–6° approach rather than the standard 3°; that steeper aim is set once at commissioning and adjusted on site if the helipad's obstacle environment changes. Units are powered from a constant current series circuit — often a dedicated circuit rather than one shared with fixed-wing runway lighting — through their own isolating transformers, with the CCR or ALCMS setting one shared brightness step for day, twilight, or night across all four units. As with fixed-wing PAPI, that command changes overall brightness only; it cannot alter which unit shows red or white. Loop monitoring is standard series-circuit practice: the CCR tracks loop voltage against commanded current and reports a voltage rise as a loop fault (open lamp or failed transformer) for maintenance to trace, while the fixed optical aim itself is verified by periodic ground or flight check rather than by any onboard sensor.

Each unit shares the same rectangular, box-section housing used on fixed-wing PAPI installations — die-cast aluminium alloy or louvred galvanised steel, weatherproofed against UV exposure and de-icing fluid — but is set up for the steeper approach angle used at a helipad. The optics are split into a lower red filter glass and an upper clear (white) glass, precisely separated so the beam transitions sharply between colours at the set glide-path angle, with a built-in spirit level and micrometer pitch adjuster used to aim each unit during commissioning. The housing mounts on a frangible mast at a fixed, surveyed height, positioned close to the helipad centreline compared to a runway installation, and engineered to shear away cleanly if struck. Cabling runs underground in conduit to a dedicated isolating transformer per unit, housed in a nearby base can, with sealed, direct-burial connectors and a drainage provision to keep the transformer and cable entries free of standing water.