![]() ![]() ![]() Three light bars (5 steady-burning white lamps on each) that form a crossbar Serves several functions Enables you to determine your physical location from the runway On glideslope, when the decision bar passes directly underneath you, you should be approximately 100 feet above the TDZE Decision bar is 1,000 feet from the threshold and will generally appear to slip below the airplane's nose at DH Serves as an artificial horizon to help transitioning from IMC to VMC at decision height Decision bar's horizontal spread of white lights acts like an external attitude indicator, providing you with visual bank references Reference point used as a distance-to-go markħ ALS Components Decision Bar and Light BarsĪllows you to make in-flight visibility estimates Distance from the decision bar at DH MALSR light bars are spaced at 200 foot intervals ALSF 1 / 2 light bars are spaced at 100 foot intervals Flashing white lights will stop at or before the decision bar (from the approach side)ĭecision Bar acts as an external bank indicator and assists in the transition from Instruments to visualĩ ALS May Allow You to Determine VisibilityĪt a standard decision height of 200’ AGL for an ILS Category I approach you will be approximately 3,846’ from the runway touchdown zone, or 2,846’ from the runway threshold on a 3° glide path, if the reported visibility is ½ SM or 2,500’ - you will see very little of the runway environment, if any, other than approach lights Knowing the type of lights to expect can help you identify the correct runway and avoid landing on the wrong runway at an airport with parallel runways If you know the type of approach lighting available, other lighting in the airport’s vicinity is less likely to cause confusionĤ ALS Components Threshold Bar - All ALSs begin with a row of green lights that indicate the approach end of the runway Runway Alignment Indicator Light (RAIL) consists of five sequenced white strobe lights located on the extended runway centerline, the first being located 200 feet beyond the approach end of the last steady-burning light bar (generally 1,000’ from the threshold) with successive strobes at each 200-foot interval out to 2,400 feet from the threshold (may extend to 3,000 feet) Sequenced Flashing Light (SFL) White sequenced strobe lights located on the last three light bar stations The RAIL and SFL strobes flash in sequence twice per second producing a ball of light streaking toward the approach end of the runway Click on picture to play the videoĥ ALS Components RAIL and SFL provide early identification and alignment / displacement information when approaching a runway RAIL are not imbedded in the approach lights Usually installed on a runway with an instrument approach procedure Actual utility power consumption will vary based on the efficiency of certain components but will likely shake out to something around 104kVA since the incandescent lamps have a power factor close to 1.0.The ALS is an airport lighting system that projects light in a directional pattern to help a pilot (i) identify a runway and (ii) align the aircraft with the runway on final approach and landing that: Is installed at the approach end of a runway Extends outward from the runway Consists of: Series of light bars Strobe lights, or a combination of the two. ![]() Specifications FAA-E-2628b or FAA-E-2689a for all sequenced flashers.įrom the number of required lights we can then derive the total system power used for an FAA-Specified ALSF-2 lighting system - As I'm not fond of doing math it's fortunate that some manufacturers have already done this for us, and a full system (with all the flashers) requires approximately 104kW (varying slightly depending on input voltage).Specifications FAA-E-2952 or FAA-E-2491 approach lights, 500-watt, for all semiflush lights.Specification FAA-E-2408b, 500-watt, 20A, PAR-56 lamps for steady-burning, aboveground, colored lights with Specification FAA-E-982 lampholder. ![]() Specification FAA-E-2408b, 300-watt, 20A, PAR-56 lamps for steady-burning, aboveground, white lights with Specification FAA-E-982 lampholder.The ALSF-2 is a High Intensity lighting system, so lights used in the system are defined in the FAA order as follows: High Intensity Systems. The specifications for an ALSF-2 (and other approach lighting systems) can be found in FAA JO 6850.2B - Conveniently titled "Visual Guidance Lighting Systems."Īs an FAA order these are obviously US-specific, but other jurisdictions' guidance is probably similar. ![]()
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