Adding New Functions to the Remote AirfieldLighting System

Jianhua Liu, Christopher GrantCollege of Engineering

Embry-Riddle Aeronautical UniversityDaytona Beach, FL 32114

Email: liu620@erau.edu, grantch@erau.edu

Donald GallagherVisual Guidance Programm

Airport Safety Technology R&D Sub-Group, AJP-6311Federal Aviation Administration

Email: Donald.Gallagher@faa.gov

Abstract—There are many remote airfields that are notconnected to the power grid. Providing adequate lighting tothese airfields is necessary and challenging. The Federal Avi-ation Administration (FAA) has sponsored a research project,Remote Airfield Lighting Systems (RALS), through the Centerfor General Aviation Research (CGAR). The findings from theRALS research specified a light that had low power needs anda color/intensity to meet the requirements for airfield identi-fication and landing. To make these lights more appropriateto wide spread applications, the research team is conductingan exemplary operational test. In this paper, we discuss thenew functions added to these lights for the operational test,including both automatically/remotely switching on/off thelights and smart charging of the batteries using solar panelsunder the control of a microcontroller. In addition, we considerfuture new functions such as low cost pilot controlled lightingas well as wireless networking for health monitoring andcontrolling of the lighting system. These new functions cangreatly improve the convenience of the usage of RALS whilekeeping the same low cost.

Index Terms—Runway lighting, Solar charging, Remotecontrol, Pilot-controlled lighting, Portable LED light, Em-bedded system, ZigBee applications.

I. INTRODUCTION

There are numerous small, remote communities in theUnited States (even more around the entire world) whichdo not have convenient, paved road access. For occasionalemergency and provisional supply functions, remote airfieldsare a vital lifeline for these communities. To aid the pilotsidentifying the runway of the airfields as well as landingsafely at night time, adequate lighting is necessary; however,a traditional airfield lighting system could cost hundreds ofthousands of dollars and still be unusable because of aninadequate power supply for the lighting system.

The Federal Aviation Administration (FAA) sponsored aresearch project to investigate remote airfield lighting sys-tems (RALS) [1] through The Center for General AviationResearch (CGAR). The RALS team includes FAA, CGAR,

Rensselaer Polytechnic Institute, Embry-Riddle Aeronauti-cal University (ERAU), University of North Dakota, andUniversity of Alaska Anchorage.

The RALS team characterized a remote airfield (RA1),with a typical remote runwar approximately being 75 ft.wide and 3000 ft. long, in the following aspects:

RA1 no power is available from the power grid;RA2 powering schemes are limited due to possible theft

or vandalism;RA3 power usage should be limited due to the cost and

inconvenience of on-site power generation;RA4 existing FAA-certified lighting systems cannot be

deployed due to high consumption of power; andRA5 the frequency of RALS usage is about 2 hours a

time, 2 times a day, and 3 days a week, whichyields a total of 2 × 2 × 3 = 12 hours a week.

The RALS research identified a lighting configurationconsisting of four corner lights (so that they can help pilotsidentifying the location and orientation of the runway ata distance 5 miles from the airfield) and a number ofretroreflective panels to act as edge lights (so that the panelscan assist pilots landing safely on the runway). After variouslab and field testing, including test flights with the specifiedsystem, the RALS team came out the following requirementsfor the corner lights (CL):

CL1 Aviation Green (wavelength λ ≈ 500 nm) is usedfor best visual perception effect at night time;

CL2 the emission is omnidirectional with 10 photopiccandelas minimum between 0 to 10 degrees in thevertical plane so that the lights can be perceivedby pilots from 5 miles away;

CL3 synchronized 2 Hz, 40% duty cycle flashing ofthe 4 corner lights is necessary to facilitate pilots’identification of the airfield in the presence of light

1To facilitate referencing the numbered items in the paper, we useleadings two-letter abbreviations, with the definitions underlined.

978-1-4244-5853-0/10/$26.00 ©2010 IEEE 106

pollutions; the synchronization can be achieved byusing a GPS receiver at each light.

The RALS team contracted FarLight LLC to producecustomized general purpose runway corner lights. The spec-ification did not require LED as the light source but dueto the required time usage of the light and having batterypower, LEDs were used in the test fixtures. Before widespread applications of RALS, exemplary operational test isnecessary. Currently, FAA, CGAR, and ERAU are collab-orating to conduct such an operational test in Florida, as asecond phase of the RALS project.

To facilitate this operational test, we add new functionsto the FarLight LED runway corner lights. In this paper,we discuss the new functions added to the FarLight LEDrunway corner lights, including both automatically/remotelyswitching on/off the lights and smart charging of the batter-ies using solar panels under the control of a microcontroller.In addition, we consider future new functions such as lowcost pilot controlled lighting as well as wireless networkingfor health monitoring and control of the lighting system.These new functions can greatly improve the convenienceof the lighting system while keeping the cost low.

II. NEW FUNCTIONS FOR THE CURRENT EXEMPLARY

OPERATIONAL TEST

Before discussing the new functions added for the currentexemplary operational test, let us give a quick overview ofthe FarLight LED runway corner light to which the newfunctions are added.

A. The FarLight LED runway corner light

The block diagram of the FarLight LED runway cornerlight is shown in Fig. 1. Note that the battery pack has twoterminals—a Regulated 6 V terminal that powers the LEDLight Controller and an Unregulated 7.4 V terminal that canbe used to charge the battery or monitor the voltage levelof the battery. The FarLight LED runway corner lights (FL)satisfy the above requirements CL1 to CL3 with additionalparameters listed below:

FL1 Color: Green, λ = 505 nm;FL2 Intensity: 12.5 photopic candelas minimum be-

tween 0 to 10 degrees in vertical plane;FL3 Power source: rechargeable 7.4 V Li-Ion battery

with 6 V regulated output and 7200 mAh capacity;FL4 Continuous operating time: 36 hours minimum.

B. The modified LED runway corner lights for the test

The LED runway corner light is an LED fixture withminimum functionalities—it has to be switched on/off man-ually and its battery has to be charged manually with an ACLi-Ion battery charger. These manual operations can cause

Fig. 1. Block diagram of the FarLight LED runway corner light.

much inconvenience for the exemplary operational test aswell as to those residents living nearby the airfield who areoften bothered by the light pollution when the system isnot used for landing2. To make the exemplary operationaltest easier, two new functions (NF) have been added, withcorresponding hardware and software:

NF1 switching on/off the lights automatically/remotely;and

NF2 charging the Li-Ion batteries smartly by using solarpanels.

The block diagram of the modified LED corner lightfor the operational test is shown in Fig. 2, where a SolarPanel and an Operation Controller, with related wiring, areadded to the light to perform the added new functions. Notethat the switch of the original light is set to always onso that the switching on/off of the LED Light Controllercan be controlled by an electronic switch in the OperationController. A picture of the modified LED runway cornerlight, with annotation to each functioning block, is shownin Fig. 3.

1) The Operation Controller: The Operation Controller,located in a sealed box under the solar panel in Fig. 3 andillustrated in Fig. 4, is the brain as well as the workhorseof the modified light. It consists of the Mother Board, theMicrocontroller board (an Arduino Nano [2] is used for theoperational test, and it can be replaced by a customizedmicrocontroller board designed by the authors, also shownin Fig. 4, in the future; this customized board has integratedZigBee [3], [4] wireless networking functions) and an 4channel Remote Control Receiver.

The Microcontroller (MC) board of the Operation Con-troller can perform the following functions:

MC1 polling the output of the Remote Control Receiverto perform the transition of the work mode (will

2These intense flashing LED lights can be annoying to some residents,and they have requested that the LED corner lights should be able to beturned off easily if needed.

107

Fig. 2. Block diagram of the modified LED runway corner light.

Fig. 3. Picture of the modified LED runway corner light.

be detailed later) according to the polling result;MC2 monitoring the voltage level of the Solar Panel to

determine if

∗ it is currently day time or night time by compar-ing the sampled voltage value to predeterminedthresholds; the result will be used to switchon/off the LED Light Controller according tothe work mode

∗ it has high enough voltage so that the BatteryPack can be charged

MC3 monitoring the voltage level of the Battery Pack todetermine if it should be charged according to therules to be described later and switching on/off thebattery charger accordingly;

MC4 switching on/off the LED Light Controller—andhence the light;

MC5 monitoring the health of the Battery Pack, such asthe discharging rate in normal usage, to determine

Fig. 4. Picture of the Operation Controller of the modified LED cornerlight.

if it has a satisfying capacity or not. (The result canbe sent to a PC through a USB cable if ArduinoNano is used or through a ZigBee device if thecustomized Microcontroller board is used.)

2) Remote control of the modified lights: The modifiedLED runway corner lights can be switched on/off remotely;this is supported by a low cost wireless remote control linkworking in the 315 MHz frequency band that is heavily usedby wireless garage openers. This link consists of a remotecontrol transmitter and 4 matching remote control receivers,each for a corner light, and has the following highlights:

RC1 Operating distance: up to 3000 meters;RC2 Modulation: ASK (amplitude-shift keying);RC3 Powering for the receiver: 5 V DC, 5 mA;RC4 Coding: Fixed code via soldering [5];RC5 Number of channels at each receiver: 4;RC6 Mode of receiver output: momentary3.

Note that coding is necessary to avoid interference fromnearby garage openers. Fixed code, where the code doesnot change, is preferred to rolling code where the codechanges each time the transmitter button is pressed, due tothe following reasons:

• for fixed code, multiple transmitters can be used tocontrol multiple receivers if they are coded with thesame code, which is necessary for our operational test,whereas for the rolling code, only one transmitter canbe used with multiple receivers—it is necessary to trainthe receivers so that they learn the code from one (andonly one) transmitter; (for our operational test, at leastone transmitter will be kept by the testing crew, and atleast another one will be kept by the residents living

3An alternative mode is latched. The momentary mode is preferred sincea button may have to be pressed a few times to activate all the lights if thetransmitter is not located appropriately; in this case, receivers with latchedmode can have different outputs which can desynchronize the lights.

108

nearby the lights if they choose to switch off the lightswhen not in use);

• when controlling multiple receivers with a single trans-mitter using the rolling code, if one receiver loses thesignal due to reasons such as long distance from thetransmitter or blocked transmission path, the codes inthe receivers will lose synchronization, and the systemwill have to be retrained.

3) Working modes: There are 4 push buttons on theremote control transmitter, denoted as A to D, each corre-sponding to a channel at the receiver. There are 3 workingmodes for the modified LED runway corner light, each istied to a push button on the transmitter:

Mode 1 (default mode, tied to button A) the light will beturned on at night time;

Mode 2 (button B) the light will be turned off at night time;Mode 3 (button C) the light will be turned on for 15

minutes at any time (day or night).

The transition between the working modes is shown inFig. 5. When the modified LED runway corner light isturned on, it enters Mode 1 at the reset of the microcon-troller. Pressing Button B on the transmitter will lead it toMode 2; this is necessary so that the residents around theairfiled can turn off the lights at night time if no aircraft islanding and not be bothered by the flashing runway lights.When it gets dark again the next day, the light returns toMode 1 automatically; the light can also be set to Mode 1from Mode 2 by pressing Button A. At anytime, a press ofButton C on the transmitter will bring the light to Mode3, where the light will be on for 15 minutes. After that,or if Button D is pressed, it will go back to the modebefore it enters Mode 3. Note that if one or more lightsdo not response to a press of a button due to long distanceor antenna blocking, a repeated pressing of the button at adifferent location will solve the problem.

4) Battery charging: Solar energy, if available, is a greenand convenient source for charging the batteries of the LEDcorner lights. The following issues are considered whenchoosing the solar panels and designing the battery chargingcircuitry.

a) Type of charger: The Li-Ion batteries cannot betrickle-charged (the tiny, constant charging current willshorten the life of the Li-Ion batteries), and hence a ‘smart’charger is needed. This smart charger will start chargingif the output voltage of the solar panel is higher than apreset threshold and the voltage of the battery pack is lowerthan another preset threshold. It will stop charging when thecharging current is lower than a preset threshold.

b) Choice of solar panel: The nominal voltage at theunregulated terminal of the Li-Ion battery pack is 7.4 V,

Fig. 5. Diagram of the state transition of the working modes for themodified LED corner light for the operational test.

and the maximum (allowable) voltage is 8.4 V when it isfully charged. As such, the solar panel should be able toprovide no less than 10 V output under the sunshine if theswitching type boost DC-DC converter, which is usuallymore expensive than other types, is not used. However, ifthe output voltage of the solar panel is too high, it will bewasted. For example, if a linear type voltage regulator isused, the excessive voltage is converted to heat, which is awaste of the output of the solar panel. Or if a switching typebuck DC-DC converter is used, the converter will not drawcurrent from the solar panel during the off period of the dutycycle of the converter, which is a waste of the solar panel.While using a capacitor with large capacitance at the inputof the switching type buck DC-DC converter circuit canmitigate the waste, it is not very efficient. The off-the-shelf6 V solar panels can provide more than 10 V output underthe sunshine, while the off-the-shelf 12 V solar panels canprovide about 20 V output under the same condition. Whilethe latter is perfect for charging the 12 V SLA (sealed leadacid) batteries, its voltage is too high for our application.Hence, we choose the 6 V solar panels. To leave enoughmargin for the charging in the case of a few consecutiveovercast/rainy days, we choose the solar panels with outputpower no less than 6 Watts.

III. NEW FUNCTIONS FOR FUTURE SYSTEMS

In this section, a few new functions for the future RALSare considered.

A. Pilot controlled lighting

In non-towered or little-used airfields where the powergrid is available but it is not economical to light the runwaysall night or to provide staff to switch the lights on/off, thelighting systems of the airfields can be controlled by usinga pilot controlled lighting (PCL, PL) system [6]. With the

109

PCL system, a pilot can turn on the lighting system for 15minutes from the air by clicking the microphone talk buttonon a specified aviation radio frequency. According to FAA,the PCL systems usually have three settings:

PL1 Low intensity: 3 clicks within 5 seconds;PL2 Medium intensity: 5 clicks within 5 seconds;PL3 High intensity: 7 clicks within 5 seconds.

Note that the controller of a PCL system may be reset at anytime during the turn-on which will keep the PCL system onfor another 15 minutes.

Unfortunately, the existing controllers of the PCL systemscannot be appropriately used in RALS because the existingcontrollers work in the centralized mode, i.e., a controllercontrols the entire lighting system, whereas the RALS’ lightswork in the distributed mode; this mode difference problemcan be remedied by providing a controller to each LEDrun corner light, but this remedy will lead to the nextproblem. An existing PCL controller, which consists of amicrocontroller, an aviation band receiver, and a relay forswitching on/off the 110/240 VAC or 24 VDC power supplyfor the lighting system, is very costly compared to the LEDrunway corner lights of the RALS.

The researchers propose to use a low cost method toimplement the PCL controller for RALS. This RALS PCLcontroller is the same as the existing PCL controllers (PC)except the relay is replaced by a remote control transmitter,which can be the same one used for the operational test.With a minor revision of the modified LED runway cornerlight, the following settings can be implemented:

PC1 Flashing corner lights for 15 minutes: 5 clickswithin 5 seconds;

PC2 Solid corner lights for 15 minutes: 7 clicks within5 seconds.

Note that with these settings, the GPS receiver for eachcorner light is no longer necessary since the synchronizationof the flashing can be triggered by the transmission of thesignals from the remote control transmitter and maintainedby the microcontroller in the Operation Controller of thelight. With appropriate choice of the aviation band receiver,the saving of the GPS receivers will be more than enoughto justify the cost of the PCL controller for RALS. Thisway, we can greatly improve the convenience of using RALSwhile maintaining the same cost (or even lowering the cost).

Note that Mode 3 of the modified LED corner light issimilar to the future new function PC1.

B. Wireless networking

With the lowering of the cost of electronic devices andsolar panels, the retroreflective panels can be replaced by

simple LED edge lights4. When the usage of these LEDedge lights can be justified, a microcontroller board like thecustomized one with ZigBee wireless networking functionsshown in Fig. 4 can be used in the edge lights to providecontrol as well as routing for wireless networking.

Wireless networking can bring RALS to a new levelof convenience. The new functions provided by wirelessnetworking (WN) can be summarized as follows:

WN1 By using a ZigBee devices connected to a personalcomputer, a maintenance staff can receive the sys-tem health data, such as the health of the batteries,just by driving by the lighting system;

WN2 The remote control transmitter and receivers forthe PCL function can be replaced by the wirelessnetworking transceivers, which can provide end-less system reconfiguration/upgrading capabilities.

IV. CONCLUDING REMARKS

In this paper, we have discussed the new functions addedto a manufacture’s LED runway corner lights for an ex-emplary operational test of RALS. These new functionsinclude automatically/remotely switching on/off the lightsand smart charging of the batteries using solar panels underthe control of microcontrollers. In addition, we have alsoconsidered future new functions such as low cost pilotcontrolled lighting as well as wireless networking for healthmonitoring and controlling of the lighting system. Thesenew functions can greatly improve the convenience of theusage of RALS while keeping the same cost and thus greatlyfacilitate wide spread application of RALS.

REFERENCES

[1] Project Description, “Remote airport light-ing systems (rals),” CGAR Online,http://www.cgar.org/information research.asp?E=1&PROJID=23,last accessed: 11/23/2009.

[2] “Arduino nano v 3.0 user manual,” Download available athttp://gravitech.us/Arduino/NANO30/Arduino-Nano3-0.pdf, last ac-cessed: 11/23/2009.

[3] S. Farahani, ZigBee Wireless Networks and Transceivers. Burlington,MA: Newnes, Elsevier Ltd., 2008.

[4] IEEE Standard 802.15.4, “Part 15.4: Wireless medium access con-trol (MAC) and physical layer (PHY) specifications for low-ratewireless personal area networks (WPANs),” Download available athttp://standards.ieee.org/getieee802/download/802.15.4-2006.pdf, lastretrieved 11/23/2009.

[5] A. I. Alrabady and S. M. Mahmud, “Analysis of attacks againstthe security of keyless-entry systems for vehicles and suggestionsfor improved designs,” IEEE Transactions on Vehicular Technology,vol. 54, pp. 41–50, January 2005.

[6] “FAA aeronautical information manual,” Federal AviationAdministration, Download available: http://www.faa.gov/air-traffic/publications/atpubs/aim/Chap2/aim0201.html. Last accessed:11/23/2009.

4Some of the solar-powered LED garden lights are already cheaper thanthe retroreflective panels.

110