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SpanLite FAQs

1. What is a “catenary” power line?
FAA Advisory Circular 70/7460-1L (Dec. 2015), which addresses Obstruction Marking and Lighting, defines “catenary” as “suspended wires (or lines) kept at a defined mechanical tension by supporting structures”. Examples of catenary power lines includes lines that cross rivers, canyons, and lakes, as well as certain lines in proximity to heliports and airports.

2. Why do catenary power lines need lighted markers?
The FAA advisory (cited above) calls for marking catenary power lines (69 kV or greater) with lighted “marker balls”. The goal is to make catenary lines more visible to pilots both day and night.

3. Does SpanLite satisfy the FAA advisory?
Yes, SpanLite meets or exceeds the guidelines in the FAA advisory for lighting and marking catenary lines up to 500 kV and higher.

4. What about other kinds of power lines?
In addition to marking catenary power lines, SpanLite is an effective solution for marking nearly any power line day and night. SpanLite should be considered for any location where pilots might have difficulty seeing a power line in their path. (Heliports are a good example.)

5. Can SpanLite be used as a tower light?
Absolutely! Monopoles 150 feet or less often have one conductor near the top of the pole. A SpanLite can be mounted near the top insulator on the conductor and provide the recommended 2-810 FAA LED steady red lights. There is no need for a transformer and associated electrical systems. This is an ideal solution for remote locations, such as Alaska, where solar or direct power is not an option. The marker simply lights up when attached directly to the live line (minimum 40 amps).

6. How does SpanLite work?
P&R Tech’s patented flux capacitor and solid state regulator built into SpanLite use the electrical field generated around the powered line to continuously illuminate the two 810 lights at 32.5 candela each. SpanLite installs directly on live lines from 15 kV to 500+ kV and carrying from 40–2,000 Amps.

7. What happens if the line suffers an outage or is taken out of service?
The FAA acknowledges that lighted markers (which include SpanLite) will go dark. Of course, the SpanLite marker still marks the line for visibility in daytime. (In most cases, tower light systems will also go dark, as they too will have lost power.) A minimum current is required to power a lighted marker. SpanLite requires a minimum of 40 amps to fully illuminate both 810 obstruction lights to 32.5 candela. (The lights start shining at 20 amps.)

8. Which size of SpanLite should I use?
The FAA advisory specifies 36 inch diameter lighted markers on “extensive” catenary wires.* “Less extensive” wires can use 12, 20, or 24 inch markers. (SpanLite is available in 12, 24, and 36 inch models.) The distinction between “extensive” and “less extensive” is not defined in the FAA advisory. In practice, P&R Tech suggests that 36 inch SpanLite markers be used only on extensive catenary lines. For all other lines, 12 or 24 inch SpanLite markers have a lower wind loading profile, weigh less, and cost less.

*An exception to the 36 inch guideline is allowed for closely spaced lines, such as “double bundled” transmission lines. For example, if spacing is 18 inches, a 12 inch SpanLite can be used as it has a 6 inch radius.

9. How many SpanLite markers will I need?
Lighted markers should be spaced equally along the wire at intervals of approximately 200 feet (61 m), or a fraction thereof. 25 feet is the maximum allowable distance between the highest wire installed with marker balls and the highest wire without marker balls. (Wire sag or droop will occur due to temperature, wire weight, wind, etc.) On less extensive catenary lines the FAA may recommend fewer lighted markers.

10. What color markers should I use?
Lighted and unlighted markers should be installed by alternating solid-colored markers of aviation orange, white, and yellow (with aviation orange at each end). For three or fewer markers in a sequence, all markers should be aviation orange.

11. Which sections of the FAA advisory specifically apply to lighted markers?
Click here to view a PDF containing these FAQs and the pages from FAA Advisory 70/7460-1L (Dec. 2015) that apply to lighting and marking catenary power lines. Click here to view the entire advisory.