Skip to page content
Official US Government Icon

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure Site Icon

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

The latest general information on the Coronavirus (COVID-19) is available on For FAA-specific COVID-19 resources, please visit
United States Department of TransportationUnited States Department of Transportation

Lighting Systems - Medium Approach Light System with Runway Alignment Indicator Lights (MALSR)

Approach Light Systems (ALS) provide the basic means to transition from instrument flight to visual flight for landing. Operational requirements dictate the sophistication and configuration of the approach light system for a particular runway. The MALSR (Medium Intensity Approach Lighting System With Runway Alignment Indicator Lights) is a medium approach intensity lighting system (ALS) installed in airport runway approach zones along the extended centerline of the runway. The MALSR, consisting of a combination of threshold lamps, steady burning light bars and flashers, provides visual information to pilots on runway alignment, height perception, roll guidance, and horizontal references for Category I Precision Approaches.

Typical ground installation
Typical Ground Installation

A typical MALSR uses 18 lamps (PAR 56) along the runway threshold spaced 10’ apart, 9 light bars with 5 lights (PAR 38) separated every 200’ and 5 sequenced flashers also separated every 200’ over a distance of 2,400’ from the runway threshold. At the 1,000’ point there are three light bars (15 lamps) for added visual reference for the pilot on final approach. Sequenced flashing lights provide added visual guidance down the runway centerline path. Planned approach visibility is at least 1,800’ to .5 miles, with a decision height of 200’.

LED Green Threshold Lamp
LED MALSR System - The Medium Approach Light System with Runway Alignment Indicator Lights (MALSR) system has been evaluated for replacement of the current incandescent lamps with LED lamps and it has been determined that it will be extremely beneficial to do this replacement. The FAA awarded a contract in June 2010 to conduct a feasibility study for implementing the LED lamps and, if found feasible, prototype LED lamps will be developed for environmental testing and flight evaluation before starting production. The feasibility study will also determine if the LED lamps will support Enhanced Flight Vision System (EFVS) operations. A Civil Aviation Medical Institute (CAMI) study is also being conducted to determine if color deficient pilots can properly see the LED lamps.

The FAA conducted a CBA on the replacement of PAR-56 incandescent lamps with LED lamps for all MALSR threshold light applications. The study concluded that there was a considerable benefit in replacement lamps and the sensitivity analysis confirmed that the decision was sound.  Lamp life and lamp costs were the two most influential factors.  Estimated savings were significant and the costs of the change would be returned in only two years.

FAA Technical Lead in ATO:
Donald Lampkins -

Page last modified: