Lecture 12:ApproachLighting System

Introduction

Approach Lighting System (ALS) is the tail end of the Air Navigation System.

It is a lighting systems installed on the Approach end of an Airport.

ALS consist of a series of Light bars and Strobe lights

ALS uses

ALS serve the runway that has the Instrument Approach Procedure such as Instrument Landing System (ILS).

ALS allows the pilot to see and identify the Runway end and align the aircraft to land on the runway.

At the point where Decision Height is reached, pilot must be able to see ALS, then pilot can continue the approach.

ALS uses

If pilot can not see the ALS, the approach must be aborted and a missed approach procedure will be performed.

This is where the aircraft will climb back to a predetermined altitude and position.

From there the pilot will either try the same approach again, try a different approach or divert to another airport.

ALS Configurations

ALS are designed to allow the pilot to quickly and positively identify visibility distances under Instrument Flight Rules (IFR).

The most common approach light system configurations include: ALSF-1: Approach Lighting System with

Sequenced Flashing Lights configuration 1 ALSF-A2: Approach Lighting System with

Sequenced Flashing Lights configuration 2

Approach Lighting System Configuration 2

Used on Category II runways during instrument landing approach to align the aircraft with the centerline of the runway and to establish vertical orientation.

Up to 174 steady burning white lights serve as a reference plane,

Two rows of red side row increase the pilots horizontal perception.

Up to twenty-one white lights create a sequential strobing flash pattern that rolls toward the runway threshold.

Three intensity settings allow the approach to be used under changing weather conditions.

Approach Lighting configuration 2

Importance of Approach Lighting System As Approach Lighting System (ALS) is the tail end

of the Air Navigation System, it is important to affect the aircraft landing.

ALS allows the pilot to see and identify the Runway end and align the aircraft to land on the runway.

It very important especially during night time, bad weather and poor visibility

ALS also important to verify positive contact and let you know where the begin an end of the runway is.

Visual Approach Slope Indicators (VASI)

Function: To assist pilot with visual guidance during an aircraft landing

by indicate the pilot’s right angle of approach.

Visual approach slope indicator

VASI are light systems to let you know your position in relation to the desired glide path in landing to the runway.

They are located on the side of the runway and can be used both during the day and at night.

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Visual Approach Slope Indicators (VASI)

VASI may have 2 bars (rows) of lights. A 2-bar system has one near and one far bar.

Each bar can contain 2 light units. If both bars show white lights, you are too

high for your landing. If both bars show red, you are too low. If the far bar is red and the near bar is white

you are just right (be on the glide path).

Visual Approach Slope Indicators (VASI)

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Visual Approach Slope Indicators (VASI)

Precision Approach Path Indicator (PAPI)

PAPI work in a similar manner to the VASI. The difference is PAPI only have one row of

lights. This one row contain 4 light units. If all four lights show white, you are too high for

your landing. If all four lights show red, you are too low. If two lights show red and two lights show white

you are just right (be on the glide path).

Precision Approach Path Indicator (PAPI)

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