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Application
The VIS PAPI provides a pilot with a safe and accurate glide slope on final approach to the runway by using combinations of red and white lights to indicate a path that is too high, too low or correctly on slope. It features a rugged, lightweight, battery powered design that may be radio controlled or manually activated.
Construction and Finish
The projector base is manufactured from a honeycomb sandwich composite material which provides a lightweight, extremely flat and rigid foundation upon which the optical system is mounted. The optical system comprises two parabolic reflectors, two dichroic red filters and two doublet lens assemblies. The inclinometer and spirit level are also mounted on the projector base. Three threaded adjusting legs, fitted with coil springs, support the projector base which is protected from the elements by a weatherproof enclosure which is secured in position by the attitude adjusting knobs. The enclosure incorporates viewing windows for both the inclinometer and the spirit level, while a hinged panel gives access to the inclinometer to enable the operator to set the desired approach angle. A window in the forward face of the unit protects the optical system from stone damage caused by jet blast. The radio antenna, control switches and sealed power supply sockets are also mounted on the enclosure. The electronics module is housed within the enclosure. All fittings are fully corrosion protected.
Photometric Performance
The PAPI is a two lamp unit which produces a variable intensity split red/white beam. The three pre-set levels of light intensity, which are in compliance with night time settings of the UK CAA document CAP 168, are:
Level 1: 1,100 cds
Level 2: 2,160 cds
Level 3: 3,260 cds
The five different sets of approach information presented to the pilot by a full PAPI system is as follows:
4 x White Signal: HIGH
3 x White and 1 x Red: SLIGHTLY HIGH
2 x White and 2 x Red: ON SLOPE
3 x Red and 1x White: SLIGHTLY LOW
4 x Red: LOW
Approach angles of between 2º and 8º can be achieved and the unit is accurate to within 1 min of arc.
Power Supply and Endurance
Power is supplied by sealed lead acid maintenance free batteries (SLAB). These are housed outside of the VIS PAPI in two separate waterproof cases of robust construction. A short cable connects each battery case to the VIS PAPI. Fully charged batteries will provide 8 hours of continuous operation at full intensity. Battery charging is accomplished via two sealed sockets on each case.
Environmental Performance
The VIS PAPI family of products has successfully completed a full and comprehensive schedule of environmental and type testing designed to meet rugged and exacting standards. These include:
• Climatic conditions
• Corrosion and salt resistance
• Mold growth
• Fluid contamination
• Vibration and shock
• Reliability and maintainability
Control
The PAPI can be supplied with either manual or radio control. With the radio version of the PAPI, control is achieved either manually or by using the Master Switching Unit (MSU). A selector switch mounted on the control panel of the VIS PAPI enables either mode to be selected by the operator during deployment. Radio control is via a coded VHF receiver module mounted inside the electronics enclosure. The coding of the radio signal ensures a high rejection of radio interference from other transmissions and protects the unit from unauthorized operation either by accident or intent.
Deployment
Once the optimum glide path angle has been decided, the VIS PAPI units are deployed in a wing-bar out from the runway edge (port side on approach). The approach angle and angle differential settings between the units can be set prior to deployment, it is then only necessary to level each unit once it has been positioned. When deployed, the VIS PAPI is mounted upon a rectangular base plate, which may be fixed into place and is then secured by keyholes in the base plate and a spring and bobbin arrangement at the fore and aft positions.
Dimensional Data
PAPI UNIT:
Height: 300mm
Width: 365mm
Length: 595mm
Weight: 16.8 kgs (incl. base plate)
BATTERY CASE:
Height: 260mm
Width: 210mm
Length: 170mm
Weight: 13.6 kgs
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