Skip to main content

PLASI RWY 31 Approach Guidance: How It Works!

Where did it come from?

Cameron Park Airport presently has a relatively unique landing guidance system on Runway 31. Donated to the Cameron Park Airport District (CPAD) by the Friends of Cameron Park Airport (FOCA), the Pulsed Light Approach Slope Indicator (PLASI) was acquired through many hours of dedicated volunteer work coupled with many people who made generous donations for this cause! This lighting system provides the airport and surrounding community with an improved measure of safety for both day and night flight operations.

How To Use the PLASI

The PLASI is a Visual Glide Slope Indicator (VGSI) and is similar to the VASI systems located at most commercial airports with on important exception: The PLASI System is more precise and easier for pilots to identify the actual projected glide path. The PLASI system provides the pilot with a stabilized approach by means of a single light signal from a location near the intended touchdown point on the runway. For O61, the projected touchdown point is approximately 170 feet beyond the actual displaced threshold markings on Runway 31.  In any event, pilots should not land before the displaced threshold and are encouraged to transition to touchdown at the displaced threshold marked on the runway in order to take full advantage of the available runway.

Profile schematic drawing of approach guidance system at airport
Note that Cameron Park's approach guidance to Runway 31 is 6 degrees and may require close attention to energy management in the pattern!

Pulsing White Means Too High!

The pilot of an aircraft that is on the glide path will see a steady white light emanating from the PLASI. If the aircraft is above the glide path the pilot will see a pulsing white light. The further the aircraft is above the glide path, the faster the pulses appear to the pilot, permitting the pilot to gage distance above the intended glide slope.  As the pilot corrects the approach and nears the intended glide path, the rate of pulsing will become slower until the aircraft intercepts the glide path. Once on the glide path, the pilot will observe the steady white light.

Red Means…well…

Here is the important side of the glide slope: If the aircraft descends slightly below the glide path the pilot will see a steady red light from the PLASI. The steady red light sector is one half the vertical distance of the steady white “on course” signal. If the aircraft continues to descend further below the glide path the steady red light will begin to pulse. The further the aircraft deviates from the glide path, the faster the pulses appear to the pilot. As the pilot corrects the approach and nears the glide path, the pulsing red light will appear to slow until it becomes steady, and then as the correction continues, will transition to the solid white signal associated with “on glide path.” REMEMBER: ALL RED LIGHTS INDICATE YOU ARE LOW. A steady red light indicates you are near the glide slope, but still low.  A pulsing red light means you are well below the glide slope.

The on-glide-path-steady-white light is a very narrow angular wedge of only 1/3 of a degree. This translates to approximately 1.25 dots above or below the glide path on a typical ILS-type glide slope indicator. Energy management is important.  Night approaches are safer when a glide slope assisting device is available to gauge a pilot’s position and to avoid obstructions near the approach path. The PLASI system also has an effective visual range of approximately 5 nautical miles during the day and up to 20 nautical miles at night, depending on weather conditions.

We hope you will use and enjoy the PLASI guidance system! It is unique, but is very effective.