(1) Lowteaperatwe ioid hlgh-tesperature testing may affect seals.

(2) Dynamic testa may affect the structural integrity of tbeЪм%i

d= Teat yaaiationg. Before condueting tee testa; detendne *iw required variations of the test procedias(s). The choices for varying tbe test procedure(8) are extremely limited. The primary variations involve the test altitude, altitude change rate, and test duration, as outlined in 1-3.2. Other envirni-ntal coebinations, sucA as low tenperature and low pressiM. are not addressed in this method but aay be considered.

1-3.1 <а>о1се of test procedtjre(s)

a. Operational purpose of the test items. Prom the requirenuit dociaent(s). determine the fisxztions to be performed by the equipnent in a low-pressure envl

and any limiting COTditims.

b. Test objectives. The primary objectives of the low presswe (altitude) test ere to determine if:

(i) The test item can be stored and operated at Ы01 ground eievatien

sites.

lersPD 500.3

900.Э-2

ApDlioatlon. This msthod ia intended to be ueed for the following

slicaticns:

(1) Air ehipnant of materiel in cargo aircraft.

(2) Bciuipment designed for inatallation or operation at high ground

elevatione.

(3) jlosive (rid) decoaoresaion due to aira>aft dMBge.

b. BeatrictionB. Thie method ia not intended to be tMed to test equipanfit to be installed in and operated in aircraft, missiles that fly at high altitudes (i.e.. above 4,370m (13.000 it)), external stores, or space vehioies. since auch equipemnt sould bs subject tc asthcd 520. Ttiis altitude test ssuld be a dupllcaticr. cf effort and a less effective test for such equipeent.

c. Sequenoe. (See General Requirements, 5.1.4.) This method is 0( )Sldered to be the least damaging of those inclxided in this docunent for most types of equipment and therefore may be one of the first to be conducted. Other testing may contribute significantly to the effects of low pressure (see 1-2) on the test item and may have

to be conducted before tbis meUiod. For eKMsple:

300.5-5

(2) Th test Item can be transpopted by air in Ita normal shipping/storage ccnfiguraticn.

(3) The test item can survive a rapid daconfireesion and. if not, to determine if it will damage the aircraft or present a hazard to personnel.

c. Sslsctlon of the test D-ocedureCa). Three test procedures ar included ithin this method: storage, operation, and rapid decosnression. Based on the test data requirements, determine which of the test procedures or conbination of procedures is applicable. Consideration should be given to tenperature-altitxide effects as snropriate.

(1) FreeedTjre I - Storage. Ppocedis I is apporopriate if the test item is to be stored at high ground elevations or transported in its shijing/storage

eonf iguratlon.

(2) Procedure II - Operation. Procedure II is xjsed to determine the performance of the test item under lowr*pressure conditions and can be preceded by procedure I, procedure III, or both. If there are no low-pressure storage or explosive deccsprassicn requirassnts, this procedure can stand alone.

(3) Procedure III -JRffplJI jiXiTaxrmaaion. Procedure III is used to determine if a rapid decrease in pressure of the surroxjnding environment will cause a test item reaction that would endanger nearby personnel or the aircraft in tttich it is being transported. After the rapid deconpression test, a potential safety problem

operational ohe. Tbls mocedure essi be meceded by either the storage or other operational test.

1-3.2 Choice of related test conditions. After the tost procedure(s) is chosen, the test altitude(s), altitude caiange (cllnb/descent) rate, duration of eicposis>e,

test item ccnf ig-OFaticn, and any additional appropriate guldeliiies tsist be determined.

a. Test, altitude. Base determination of the specific test altitudes on the anticipated deployment or flight profile of the test item. If this information is not available, use the following guidance to determine the test altitude:

(1) Wbrld grojid areas. The highest elevation currently c№.t :plated for ground military operations (equlpnent operating ajnd nonoperating) Is 4,870 (IB,ООО ft), 57 kPa (8.3 psla) (reference a).

(2) Transport aircraft carso compartment pressure conditions. Table 9(Ю.З-1 provides the minimum cargo compartment pressiires for various aircraft used to transport cargc. These presstss ean oeewF as a result of failia of the autosntic pressijrization system. Rsdurtdant syst-ems prevent rspid loss of pressure vr.less explosive decoivression occurs. Testing to the 4,570m (15,000 ft) equivalent altitude vlll assure that the equipomnt shipped by air will successfully withstand the low-pressure environment.

14 JULY I9i

TABLE 500.3-1. mnlBA,

Aircraft

kfinioum Cargo CoDpartamit PraesiM

Equivalent Altitude (referenoe c)

jj (. .84 k?aJ.

it ftltUSBS-i

aioaive deoMBrem iau testing: IS.SGCa St cthsr altitudes ?rill be enceyntered.

test the equipsssnt for the fenoen elevatico.

b. Altitude change rate. If a specific rate of altitude change (climb/descent rate) is not known or specified in tbe requirements docueent, the follo ing guidarMse is offered: In general, and iith the exertion of the explosive decoBfxression test, tbe rate of altitude change should ct ssecseu 10 m/s (2.000 ft/Siln) isilsss Jvstified by the anticipated dsployssent platfcrss. In a full militapy рошвг takeoff, fdltery tranfiport aLircraift noma.1 ly have an average altitude change rate of 7.6 ха/в (1.5(X> ft/min). To conserve fuel, the present procedure is to have a 3.8 to 4.1 m/a (750 to 800 ft/min) altitxjde change rate noml practice for comsercial aircraft operations. The value of 10 m/s will also be used for ground deplcnaent tests (for standardization proposes) unless otherwise specified.

c. Bapid decoapression rate. There are several conditions for wMch the rapid rate of deconpression may vary. These inclixie:

(1) Massive damage to the aircraft, but the aircraft survives and deconpression is virtual ly instantaneous.

v2) Belatively small boles caused isy foreign objects through shich dscoisprsssion could occur at a slossr rate tlan in (1) above.

КЕТЮО 500.3

1-4.2 piiTrfirY rj test inforroatian required. The foiio n.ng information is requl in the test plan for adequate conduct of the test of section II:

a. Test jprocedure.

b. Test altitude(s).

c. Altitxzie change rates.

d. Test duration.

e. Test item conf lgta*atlon.

f. A:&iitiGrA! guidelines used.

(3) Relatively gradual loss of pressure due to loosening of aircraft

structure.

Explosive deooBiiressiGn (c(l)) should be accospllshed within 0.1 second, ltaфid decoBopression (c(2)) and (c(3)) should not take more than 00 seconds.

d. Test <luration. For procedure I, the test duration lould be representative of the anticipated service environment, but a test duration o£ at least опт how is considered adequate for most equipment. Procedures II sni 111 do not require extended periods at the test pressure once it has been reached and any required ftswtlons ai performed.

e. Test item conf Kuration. Configxjre the test item in a nanner that is characteristic of its normal configuration, i.e., operational for hi ground elevation simulation; in its shipping/storage container for air transport, etc.

f. Additional <uide 1 inea. Review the equipment specifications and requirements docunents. Apply any additional guidelines necessary.

1-4 SPECIAL OOMSiraSATIOMS

1-4Л Failure crriteria. Failure criteria for procedures I and II ar as described in Qeneral Requirements, 5.2.7. For procedure III, the test item falls only if rapid decompression causes a hazard to the aircraft or to the personnel; the test item need not show satisfactory post-test performance unless otherwise specified.

lub-siv-eiw 14 ja.7 18

1-5 VBFESOKES

a. ШЬ-ЗТО-гЮ. nrmt.o Infomation To Determine Deaign and Tmet BeouiremBnta For Militarv Svgtema and EoxilPmBnt. 9 January 1967.

b. !>,TJHig of Васкдго-Jd ffatgrial for ,MIL-STT>-21QS. Cltnatic ggrsai for llllitarv BtnitBeaent. Badfopd, MA: Air Force Caaibridge Research Laboratorias, 1974. DTIC пивймг AD-TBO-SOB.

e. яь.туТЬо/ of Qeophvaics and Space рпу^угтштт*, Bedford, MA: US Air Force CasiKridge uesearcn Laboratories. Office of Aerospace Research. 1965.

1076. МОДА/МАаАЛШГ, 1978.

iETBOD 500.3

ICTKX) 500.3 LOW PRESSURE (ALTITUDE) SE(7ri(XI II

II-l AfPffflfT

II-l.l Teat, facility. The vquivd apparatua consists of a chanbar op cabinet and avKlliary Instruaantation capable of saiintalnlng and continuously nonltorlng tbe specific conditions of low pressure. For procedure III, the facility shall be С1фаЫе of providing dec< >reS8ion in the prescribed time period.

11-1.2 Controls

a. Qnleas otherwise specified, the altitude change rate shall not exceed 10 т/в (2.000 ft/adn).

b. Continuous recordings of cbamber pressis shall be taken if required.

c. Readout diarts should be capable of being read with a resolution within two percent pf full scale.

11-1.3 Test, interruption. (See General Requirements, 5.3.4). To achieve the J desired effects, the test item must be subjected to th4 low-pressure (altitude) environnant without interruption.

a. Ondertest interrts>tions. Any occurrence that causes the test section pre8StB>e to deviate nore than 10 percent of the measured value toward aobient atnospheric conditions shall be followed by a repeat of the entire test.

b. Overtestf interruptior. Any occurrence that results in a pressure decrease of more than 10 percent of the measured val\je below that cited by the requirements docvamnt should be follo ed by a complete physical examination and operational check (where possible). Any evidence of deterioration should result in a retest. Reinitiation of the entire test with a new test item is allovmd. If no deterioration is detected, the entire test shall be repeated.

II-2

II-2.1 PreliBdnarv steos. Before initiating ai testing, determine from the test plan:

a. fbicfa test procedures are required.

b. The low-pressure operation and storage requirements.

КЕТЮО 500.3

MIL-STO-eiOE 14 JUL? 19

11-2.2 Pretest standagd ailmt rfieekout. All itens require m. poretest dwckout at standard anbient conditions to provide baseline data. Conduct tlM cdMKdcout as foil

Step 1. Insert the test item in the test chaaber.

Step 2. Prepare the test item in its operational configuration in aooordanoe

eith General Rsquiresssnts. 5.2.2.

Step 3. Record the standard ambient conditions.

Step 4. Conduct as oosplete of a visual ejouBinatlon of tiM %e t itea as possible, and docunent the results.

Step 5. Condix:t an operational checkout in accordance with tbe test plan.

Step e. Record the results for coopliance with General BequLremants. B.3.1.

II-3 ШХДйРиаВ. The following test proeedifes. almie or in eovinatisn. provide the basis for collecting the necessary information concerning the test item in a low presets< enviroiamt. Specif ic steps are included in the test jproeedises to conbine the test procedures to get the necessary test data. Qnless otberwlee specified, the Ghanter tenperature shall be maintained at standard esbient conditions.

II-3.1 Procedure I Storage

Step 1. Adjust the test Itmns conf igu<ation to that required for transit.

Step 2. Wth tbe test item in the daeaber, adjust tbe rhertjar air pressure, at

the rate specified in the test plan, tc the required test altitude.

Step 3. Maintain the conditions for a minimusi of one hour tstless otherwise si>ecified in the test plan.

Step 4. Adjwt the chaiAer air pressure to standard anbient atmospheric conditions at a rate not to exceed that specified in the test plan.

Step 5. Conduct a conplete visual examination and an operational chedfout of the test item in accordance flth test plan, and docunent tbe results.

Step e. Conpere these data with tbe pretest data.

Step ?. If an cperatlcnal test is {required, proceed to step 1 of procedis II: if a rapid decoREression test Is required, proceed to step 1 of proeedtsw III.

МЕТНСЮ 500.3

MIL-3TD-8I0E 14 JULY 1S8S

II-3.2 PpocedUTe II - Operation

Step 1. Adjust the test item to its operational conflgta>atian.

Step 2. Adjust the chaxrber air pressure to the required equivalent operational altitxxie at a rate not to exceed the specified in the test plan.

Step 3. Conduct an operational checkout of the test item in aooordance -with the test plan, and docunent the results.

Step 4. Adjust the chancer air pressure to stardard an&ient atmosfric conditions at the rate specified in thm test plan.

Step 5. CondxjBt a coinplete visual examination and an operational checkout of the test item in accordance ith the approved test plan, and document the results.

Step 8. C<iara these data with the pretest data.

Step 7. If a rid decoiqpression test is required, proceed to step 1 of procedure III.

xi-3.3 procedyre Щ - 4Щ>Г9Ш9

Step 1. Adixist the test item configuration that required for storage or ) transit.

Step 2. With the test item in the chamber, reduce the chanber air pressure at the rate specified in the test plan to the maxlnun equivalent altitude of the anticipated aircraft.

Step 3. Reduce the pressure to an equivalent altitude of 12,20Om (40,000 ft) (18.8 kPa), or as otherwise specified in the test plan, as quickly as possible but in not more than 15 seconds. Maintain this stabilized reduced pressure for at least 10 minutes.

Step 4. Adjvet the Ohaober air pressure to standard aobient atoospheric conditions at the rate specified in the test plan.

Step 5. Conduct a conplete visual examination of the test item, and doc\xn nt tbe results. 1КХПЕ: Be alert for potential safety ргоЫешш.

Step 8. Conduet an operational checkout of the test item in accordance dth the test plan.

Step 7. Docunent the results.

Step 8. Сощрштв these data with the pretest data.

KETISD 500.3

J 500.3-е

a. Test Itew lamtif ication (nunifaetuMr, serial maiber, etc.)

b. Previous test aethods to >icb the specific tasst item has been 8(£>Jected.

c. Besults of each operational <aiecx and visual examnation (and pbotographs.

if arpli€abl ).

(1) Pretest.

(2) Dirij test.

(3) Fset-test.

d. Tiae-wersiai-preeeiM data.

e. Boooi aabient conditions.

f. Initial failtB<e analysis.

гШайи 5(Ю.З

Step 0. Proceed to step 1 of procedis II If en operational teat is required following this procedxsre.

II-4 ШРОВМДТКЖ TO BB ШООНВЕР. Test data shall he recorded as specified in General Bequirennits. 5.2. and shall include the following:

MIL=Sro-810S 14 JTJLT 10в9

ЖтХ> 501.3 ШОН TEMPEB/miBE

Plfifi.

SBXTWM I

I-l ИШОБЕ....................501.3-1

1-2 wnKmexnua effects . . ........501.3-1

1-3 <ШШ№1 1ШВ FOR ОРГЕНМИПЮ TEST

FSOCEDUBBS AKD ГО5Т (XWDITHMS........ 501.3-2

1-4 SPECIAL CGMSIDERATI0N5............. 501.3-12

1-5 КЬУКНКЫСКЫ.................. 501.3-13

SECTION II

II-l APPARATOS.................. . 501.3-14

II-2 PBEPARATIOK FOT TEST..............501.3-15

II-3 TEDamsm..................501.3-ie

II-4 INFQRMATKW TO BE RECORDED..........501.3-18

SBCTKM I

I-l preOsi. High-taiipepatur* chaser tests are parfcpiss tc detsrsiine if sateriel can bs storad an4 operated under liot ciimatic conditions without experiencing physical damage or deterioration in performance.

1-2 ЕРУ1р Т ОПАЬт У^ДЛ> High tanperatiMs may teepMarily or permanently infwlr the performance of the test item Ъу changing the phsrsical properties or dimensions of the material (s) conoposing it. Exaaples of some other-problems that could occur as the result of blgh-teoperature exposure are:

a. Parts binding from differential expsneion of dissimilar materials.

b.. Lubricants becoming less viscous; joints losing lubrication by outward flow of lubricants.

c. Miterials cdmnging- in dimension, either totally Or aeleetively.

d. Packing, gaskets, seals, bearings and shafts becoming distorted, binding, and failing oausing mechanical or integrity failures.

e. Gaskets displaying permanent set.

, I-

f. Clostjre and sealing strips deteriorating.

g. Fixed-resistance resistors changing in values.

h. Electronic circuit stability varying with differences in tei4>eratis*e gradients and differential expansion of dissimilar materials.

Method 501.3