"AD-A257 025

STANDARDIZATION OF PRECIPITATION STATIC TEST METHODSAND EQUIPMENT FOR THE NAVY

Matthew R. MaierSystems Engineering Test Directorate D TIC

Naval Air Warfare Center - Aircraft Division S ELECTEPatuxent River, MD 20670 0CT 7 1992

Telephone (301) 863-4598 Fax (301)1863-3876

ABSTRACT C

The Naval Air Warfare Center Aircraft Division, Patuxent River, is currently the Navy'slead facility for Precipitation Static testing of aircraft. It has been involved extensively withthe design and production of standard Precipitation Static test methods and equipment.As part of tasking given by the Naval Air Systems Command, these methods are to bepresented to other Navy facilities to provide additional test capability and overall fleetawareness of Precipitation Static. Further, this will provide standard procedures andequipment for Precipitation Static testing of'aircraft Navy-wide.

This paper presents an overview of the Precipitation Static test methods andequipment to be standardized, as well as the current plans to distribute these to Navyfacilities. Particular attention will be paid to test methodology, design of standard testequipment, and plans for distribution and training.

INTRODUCTION

For over 45 years, the U.S. Navy has the Electromagnetic Systems Departmentbeen concerned about the effects of at Patuxent River has extensivelyPrecipitation Static (P-Static) on its reviewed this material in the hopes thataircraft. During this'time, however, no this information can be used to createeffort has been made to produce or standard test methods and equipment todistribute standard, acceptable test be used Navy-wide. The scope of thisprocedures for ground testing of aircraft. paper is to discuss the Naval Air WarfareConsequently, to many facilities in the Center's current plans to achieve thisNavy, P-Static testing remins somewhat goal.

I' I " obscure. P-Static testing is the responsibility ofThe Naval Air Warfare Center Aircraft the EMP Section.- Since 1986, all Navy

I Division at Patuxent River has been aircraft undergoing electromagneticconcerned for some time about the environmental effects (E3) testing at the

apparent lack of awareness' of test 'Naval Air Warfare Center's shielded

0 I techniques on the part of the designers,, hangar have been subjected to simulatedP6 manufacturers, usersmand maintainers of P-Static testing. Testing of system level

Naval aircraft, despite many published components and testing of aircraft atreports and papers on the subject. The other Navy facilities has also beenElectromagnetic Pulse (EMP) Section of performed

92 10 ' 1 92-27900

TEST METHODOLOGY

Currently, ground testing of aircraftat Patuxent River is performed usingwidely accepted test methods in the,electrostatic field. Testing is performedby using a high voltage test set todeposit a charge onto an aircraft with ahigh voltage ion discharge wand (seefigure 1). The wand is comprised of a

FIGURE 1. P-STATnC TESTING AIRCRAFT

The need for other facilities to beable to perform P-Static Validation ofaircraft during production or maintenancephases is evident. Standard testmethods and equipment will give Navyfacilities the ability to protect aircraft andsystems from P-Static problenri. Earlydetection will preclude the necessityofmajor test programs to fix P-Static relatedproblems on aircraft. Also, if P-Static.testing in the Navy is standardized, all FIGURE& SAYING CCAGERs

equipment will be interchangeable and itwill be relatively simple for any facility to high voltage dish with electrostaticrepair or replace damaged. or defective dischargers attached, which enables theparts. wand to "spray' a simulated P-Static

charge onto the aircraft.Each areotof the aircraft is sprayed

at 40 kV and approximately 50 pA/ftcurrent while sensitive hand-heldreceivers are monitored for ,r.yelectromagnetic interference (EMI)generated by P-Static. Because thewand is comprised of electrostaticdischargers, P-Static noise generated by -c:, ror-r

the wand itself is almost nonexistent, thus %,ý --j. 1_1:• I I 1enabling a very effective test method foraircraft. EMI is generally produced due, :'-'to arcing between isolated sections of the ,c'-' t -1

"FIGURE2. HH VOLTAGE TEST SET aircraft. However, problems have alsooccurred due to corona discharge from 'btlen/the aircraft and streamering effects.

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Testing for P-Static interference Isnot the only use of the high voltage testset and wand. Additionally, specificchecks can be performed on eachaircraft static discharger to examineproper discharging capability (see figure3). A poorly performing discharger willgenerally begin arcing and generatenoise on the hand-held receivers. Also,the wand can be used to finddischargers which may be installed onisolated panels (thereby becoming lesseffective for dissipation of electrostaticcharge frdfn the aircraft). Finally, thewand can be used t~o test a fix installedon a problem area to'ensure that P-Staticno longer presents a problem in thatarea.

During a standard P-Static

FIGURE 4. DLRO ME•SURSIENT TECHNIOUES evaluation,,other instrumentation is usedto, augment testing. A Digital Low

Noise generated on the receivers can be Resistance Ohmmeter (DLRO) is used toheard in the form of popping, check bonding of the aircraft (see figuresmotorboating or squealing, depending on 4 and 5). Bonding checki can be madethe severity of the P-Static problem. I of installed electrostatic dischargers, fuel

After the entire aircraft has ýbeen tank cap of vent areas (for safety), andsprayed, the areas with the most serious also between isolated sections of theP-Static problems will be identified. Then aircraft's surface. )Bonding checks canthe actual aircraft radios or equipment to be made to determine if the aircraftbe tested for P-Static interference can be discharging system functions are inmonitored whili each problem area isresprayed at 20 ijA/ft current. This.current level has been determined to besevere for Inflight P-Static induced onNavy aircraft. However, because thedesign "of the high voltage test set isdynami'6 (see figure 2), testing can beperformed at any voltage level up to 40kV,•pd any current level up to 200 pA.

This -method can be used on avariety of aircraft to determine theirsusceptibility to P-Static interferenceInflight. Also, because each 'problem Varea can be examined closely, a solution FIGURE S. DLRO CHECK OF DISCHARGERScan readily be determined (such asInstalling a bonding strap). compliance with MIL-B-5087B (1), the

current bonding specification for Naval TABLE 1. STANDARD EQUIPMENT USTaircraft.

Also, a digital megohmmeter rWEQUIPuMEmr(megger) can be used to check the tip to Hoh Vwqý P=• SPplbase resistance of electrostaticdischargers to be used on aircraft, 1I401 VOWO DIIbO WO• nd Cabwhether installed or not (see figure, 6). 0ow Alswc Ohmmw (LRO)This will determine compliance with MIL-D-9129D (2), which gives the current f• M ~ohmgur(Mtgr)specifi6ation limits for Naval aircraft H0nd- MulMb Ro•PPr (2)dischargers. This can be used todetermine 'if the 'discharger has internal Cdamage and may need to be replaced. TESrDOCUroo ATI•oM

Stndmad Tot Promedures

DetaJWe 0Opeat Proeursa

Componnt• •sadown a•nd PLst

effective, relatively easy standard for P-Static testing can be achieved. Then,other -fJaval facilities will have thecapability and expertise to test aircraftand other systems for problems related

FIGURE L. MEGOHMMETER TIP TO BASE to P-Static, without the need for a largeRESISTANCE MEASUREMENT test program.

All of these test methods are TEST EQUIPMENTrelatively simple to accomplish.However, for the testing to 'be A current list of equipment and partsaccomplished correctly and consistently, to be provided to other Naval facilitiesstandard documentation 'will also be has already been established. The majornecessary. These will include standard components to be standardizedtest procedures, detailed operating throughout the Navy are shown in tableprocedures and equipment maintenance 1 and described in figures 7 and 8.documents. Currently, all three types of However, it is not the intention of thedocuments are available for 'P-Static Naval Air Warfare Center at Patuxenttesting of aircraft at Patuxent River. River to be the sole provider of thisHowever, this documentaticn can be equipment. An illustrated parts list,tailored for global testing at any Naval. assembly instructions, and operationalfacility, procedures will be provided at no cost to

If this test methodology can be any facility wishing to fabricate their owndistributed throughout the Navy for P- test set. All parts will be listed withStatic ground testing of aircraft, a cost- detailed diagrams showing design

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speciflcations, hdw to fix damaged Pensacola. The sixth Naval Depot,components and parti, and where to located in Cherry Point, North Carolina,procure new ones. In this way, it will be has already received this equipment withpossible for any Naval facility to provide operating procedures,, and has beenmaintenance and upkeep of the P-Static involved in P-Static testing since Octobertest equipment without having to 1990.constantly send equipment back to the This will give these facilities themanufacturer. ability to provide P-Static maintenance

This is by no means the only support for aircraft undergoingequipment possible for P-Static ground modification/ retrofits on location.testing of alnraft. The EMP section at Because these facilities are involved in allPatuxent River also utiUi.es various forms production and maintenance revolutions

.of instrumentation for'P-Static testing to of Naval aircraft, they are primedetermine the extent of interference candidates for standardizing P-Staticfound .on the aircraft equipments (see testing capability.figure 9). A six month program has been set

The.purpose of providing standard up by'the Naval Air Warfare Center attest methods and equipment is to make Patuxent River to manufacture andP-Static testing of Navy aircraft simpler, distribute these five sets of P-Staticmore cost-effective, and docentralized, equipment and documentation. Also,while also enhancing the Navy's'current other facilities are currently beingP-Stating testing capabilities, coordinated with, to provide further P-

Static. testing capability throughout theNavy. This will create a large? user baseof P-Static testing facilities, as well asassure awareness of P-Static and theeffects of interference and shock hazardproblems it causes on aircraft.

SUMMARY

By incorporating standard testmethods and equipment throughout theNavy, a reliable system of PrecipitationStatic ground testing of aircraft can be

FIGURE EMP SECTION P-STATIC TEST established. It will provide a relativelyINSTRUMENTATION simple and cost-effective means of

testing aircraft and systems for P-StaticDISTRIBUTION PLANS effects while still in the production and

manufacturing phases. Also, the needCurrently, the Naval Air Warfare for a large test program to get aircraft

Center at Patuxent River has plans to certified to operate under P-Staticdistribute five of these P-Static equipment weather conditions will be greatlyand documentation packages to the reduced.Naval Depots located* in Alameda, By distributing widely acceptedJacksonville, Norfolk, North Island, and methods of P-Static testing, problems will

be minimized if a facility decides to use replacement capability.differint P-Static testing equipment, and By distributing these test methodswill also make standard procedures for and equipment to the six Naval Depotstesting aircraft available to all Naval currently existing,-a strong capability forfacilities. Equipment design P-Static testing, development, andspecifications will also be available to awareness will exist for all Naval aircraftNaval facilities, allowing on-site repair and programs.

REFERENCES

1. MIL-STD-5087B, Bonding,, Electrical and Lightning Protection for AerospaceSystems, 2 September 1967.

2. MIL-STD-9129D, Electrostatic General Specification for Military SpecificationDischargers, 30 September 1986.

BIBUOGRAPHY

Nanevicz, J. E.; and E. F. Vance. "Corona Threshold Determination By Three StagePhysical Modelling of Aircraft." Paper presented at 10th Intemational Aerospace andGround Conference on.Ughtning and Static Electricity, Paris, 1985.

Nanevicz, J. E.; and R. L Tanner. "Some Techniques for theElimination of CoronaDischarge Noise in Aircraft Antennas." Proceeding of the IEEE, Vol. 52, No. 1, pp. 53-64,January 1964.

Tanner, R. L; and J. E. Nanevicz. "An Analysis of Corona-Generated Interference InAircraft." Proceedings of the IEEE, Vol. 52, No. 1, pp. 44-52, January 1984.

Tanner, R. L; and J. E. Nanevicz. "Precipitation Charging and Cor6na-GeneratedInterference in Aircraft." Technical Report 73, Air Force Contract AF 19(604)-3458, 1961.

Truax, R. L "Elctrostatic Charging and Noise Quieting." SAE/Air Force Lightningand Static Electricity Conference, Fort Lauderdale, Florida, 1970.

Twomey, R. C. "Laboratory Simulated Precipitation Static Electricity and Its Effectson Aircraft Windshield Subsystems." IEEE International Symposium on ElectromagneticCompatibility, Seattle, Washington, pp. 201-206, August 2-4, 1977.

Whitaker,' M. "Results of the Recent Precipitation Static Flight Test Program on theNavy P-3B Antisubmarine Aircraft." Paper presented at 1991 International Conference onLightning and Static Electricity, Cocoa Beach, Florida, April 16-19, ,1i991.

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