r ;

---~-~-.--~------~-----~

FILE COpy NO I -til MR No. L6.<\08

NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS

ORIGINALLY ISSUED February 1946 as

MemorandIDl Report L6AOR

()It

CALIBRATIONS OF SERVICE PITOT TUBES :rn ~.RE

LANGLEY 24- lN CH HIGR-SPEED TUNNEL

By W. F . Lindsey

Langley Memorial Aer onautical Laboratory Langley Field, Va .

WASHINGTON

LE COpy T returned to I of he National

y La.lfTml OIlilutics

ngton D. C.

NACA WARTIME REPORTS are reprints of papers or iginally issued to provide rapid distribution of advance research results to an authorized group requiring them for the war effort. They were pre­viously held under a security status but are now unclassified. Some of these reports were not tech­nically edited. All have been reproduced without change in or der to expedite general distribution.

L - 580

https://ntrs.nasa.gov/search.jsp?R=19930093488 2019-04-03T20:39:52+00:00Z

Ir.. ..

NACA LANGLEY 1TE1! OR IAL AERO NAUTIC AL LABORAT02.Y

ME~\-ORANDml REPOR T

f or t he

Air Tec lmica l Se rvi c e Cornxnand , Ar my Air For.ces an d t h e

Bureau o f Aeron a u t i cs , ~nvy De Js rtment

W.R ITo . L6A08

CJ...LI3RATIONS OF SE?.VICE PITOT TUBES IN THE

L. NGLEY 24 - I NCH HIGH- S PEED TUN1'EL

By \fl . F . LiYldsey

SUl.~,T A.RY

"' J.libration te st s ha ve Deen made in the LanGley 2J.~- :il1.ch h igh- speed t l.1nne 1 on a Ko l lsr: DJ1 tj--pe G- l and an NAF ~o. 1 D1 tot tube at an anp' l e o f a t tac k of 0 0 over a Il'tach numbe r ~ ange from 0020 to ~ . a7 . Additio~al calibraticn tests we re made on the l ~. F No . 1 pi tot tube at var':"ov,s a:r-.:>les o f' a tt ack OVt.; r a Mac h numbe r r8_~ ;e :'ror.1 0 . 20 to 0.53 .

Tl1e e f :ec t of d r 9.in holes 0n 'cbe i'low ·~vj.thin a s e::''',; ]',ce p i tot tube H t 0 0 o..').;le of ottac1,: was anal~Tzed and a 1'e l a t::'on was deri. ved wr,e 1'31)-- t :16 error in total pre ssure c oul d be estinat9d . TIlis a~a17si8 was ~xtended to include t he effeets ') f c:::ml-::.~es sit' ili~y on tre (,,1'ror so that an e oti:ndted value o r CtD 8x!'e;,lT.lentally determined value c oul d be ex-Lra,')olased to t.i ~;r.e r s;J~Elds . The cali1;ration t e::; ts lndic-a te th.l t t ~1. 8 accurn.c:r of t!J.e extrapolated and estionated value s are witL i n reasonable limits .

I :rrRO rac T IO:T

Calibration t e st s h&ve been made on one service pi tot tube (:~o l I sman t ype G- l) sU'J> lied hy the Ar:ilY Air Force3 , end on O:1e p i t o t tube s'J.p:;Jlied b:r t'l.El Navy Ein1 d"l s ic:n3d for service~ns t a ll 3.t':'ons . The tests WGre con­du cted t n' the Langle y 24- inc~1 r_is: - sJeed tuanel .

Tes ts of the Ko l l sn1arl t~T?e G- l pitot tube were r eq1.J8sted by the Army becau se of reported erroneous

2 m~ No . L6A08

total - pres sure indications encountered in fli ght during d ives , and be c ause a high- sneed c a libration of the inst r 1."h'nent had not been n'ade . Data pre viously obtained on ::li'-:lilar instrlJ..r.1er.ts (reference 1) show that the err')r in total ~ressure (in pe rcen t of tLe diffe r ence b e tween total and·· sta tic Dres s~res) is not a~nreciably affected oy ·:ac~. numl.)er .

If the l)re s sure i n d ica ~e d by the p i tot tube ins taIled on an.. airp l ane is i n error '.l.ud.e r di.ve concitions, it is m03t ~r oba~) IG t hat this e rror is a result of exce edino the useful angul ar ranbs cf t h e ins truJ'1en t . The angular r an:e of acceptaole acc~rac y would be greatly r educed if t:le nose of the instrument · La located t oo close to the l e'odin3 edge of t~e ~ing , because in t~1at re g ion changes :.n di r eotion of a-:'r flow are r:'uch z,reat e r than cha nge s in an6 1e of a t t ack of win.s . IllS truJnen ts he ve been ins taIled with the nose 1 0 inches fthead cf ~l'..e l eadin g edge of the wing .

For the stat'3d conciit i on s , wind - tunne l calib r at ion te s ts of the instrlw-ent a l one , even t hough made o ver a wide anbular range , could n ot be expe cted t o pr ovire a c om:;> lete s olution to t he prob l em , which coul d be o3t t e r studi"3d by comparing in f light t :::e r e ading of the se rvice 1)i to t tn.b e with that of an. i118 trw:18nt c apab l e of de ter ­min:ng the c orrect t o t al pr essur e ove r a large angular

( O i' ~ ) r ange . ~ee r e 3 rence ~ .

Ab rupt chhll:~e8 in the inci.j c ated a ir spee d under l anding c0!1ditio:1S had be'e n repo:rted for SOLe instrument installatioD3 on Rava l a i rcr a ft . Thi s troub le wa s belie ved to be d irectly related to the variatlon In the e r r or 0; the mea s ured t otal , res3ure wi th angle of a ttack . 1'he ~\j3.vy therefcre d.e signed the TiLS':No . 1 pi to t tube incor-rora tL1.; a Ete 1 t '¥:1e nose ",' ·. c h was expe c ted to me as',). re the to tal ~; re s sure t o an dC curacy of I mile per hour ovr-:r all 6ytended 8.11g ulal" r an-::;e . Tl-:e Ki~ l type instrwn8nt ( re!erence 2) is a pitot tUJe e nclosed within a tV.bul a r shie ld, thepurI'o se o f w .. tich is to maintain a l lner::k'l It be twe8::J. the pi tot tabe am: t:~e flo'i'l through t~e shield . The ins tru:·.1en t is thus capa. le of measuring t o tal ~n'essurc; withou t e rror over a l a r ge angu l a r r a nge . The u se of a Kiel t~rpe nese on t'1e :I:-iAF no . 1 pi tot t ube wi thout allowing flow t l1I'OU61: the ins trumen t except a s p r ovided by the drain holes shoul d n o t b e expected to inCl'ease i ts allgul ar r ar:',se f 8r z e ro e rror over t1-J.at of a simple total - pres Sl.:.re tube , -,hieh is a .pprox imate l y ±13° ( refe r ence 3) .

--~

Hi{ No . L6A03 3

A me thod is -; tve n ~~n this re nor t whereb-r the error c aused by t he c3 ra 5.n h0 1.0 s in a pi tot tube at' 0° angle of attack can be estlmated . 111l.e anal:Tsis Y!as extended to include the effects of cc~p~ecsibility on the error so

o t ha t an e s t ima ted value cr <..in expe l'im3ntally de termined ~ va lue coul d ~ e extr apolated to hi£l~r spe~d8 . ~

A t5st program was determined tn a conference attended by Hr. G. A . !iardi:l.g of the Ph~ ladelphia J.~a·IY

Yard, Lt . R . MUlT'llklJ.u Y:Je n 0:' Wright Field, and :nembers of the Langle ~T Laboratory staff. In accordance wi tr this program, tes ts Nere made C~ the Kolls~an type G- l and t :l1e ]I:AF No . 1 (Weit;Lnd manufactured) pitot tubes at 0 0 a,'g le of attack over '3. r~Iac~1 number range extending from 0 . 20 t o 0 . 37 . Additional tests ware then made on the NAF No . 1 pitot tu':)e 9.t var ioHs a :.lg1es 0.f attack over a range o f 11ar.11 m..1J::bers from 0 . 20 to 0.)3.

AIETEODS AlJ:) AI P AEA'I'US

The La~l.gl e y 21 ,.- inch hi.sh- s peed tun.ne 1 in v. l_ ich t~e se t es,ts were :nade is an induction- type wind tunr.el w:'" thout return p2.ssages , havin~; its incuct1.o:l nozzle dcwnstrea.'U from the test section.

The total p ressure at the test s"'ctio'l. for all s -:Jeeo3 is e 'I1.:2l t o tr:8 a tmospheric. nrass re except for a small 10s3 'c'lrou,:;h screens . 'l'hls loss , ':-or 'vvhic~l. the data re0a~ted ~erq ~ ~ ~ , V~ ~een co ~recte ~ , has been deter ­mine d j-' mes. 31)re:·1'? n.ts of t1:Je l OS3 throueh screens and by compcri~cn o~ the tot · 1 ~ressure measur od by several tota l -'9re s su:;:'e tubes .

T~e st a tic jJressurG in t!!.e ;(:st section ~.as deter ­mined by calibra cqd static -~res8u~e or1f1c83 in the tunne 1 wall u s tre am. from the te s t se c tion . The s tre a1:1 Mach YP1.lnbers and the correct total pressure in the tes t s ection were the:.l computed from. ueusured values of the atr.os :!~leric pressure and the pr essure at the calibrated 3tatic - ~rossure orIfices .

Th e two pi tot t'.lbes c alibraced and repcrted herein . are :

( 1) NA:5' No . 1 ~anu~actured by ~eigand

4 ~.Irt N8 . L6A08

( 2 ) Airspeed tube ty e 0 - 1 • ~ . • T oi ')'7;2. 8 Speclilcatlon No . /~-~iJ7

Kcl lsman l s ~art No . 701 - 02

::2he se i :13 tru.'r.en t s are shown in f L) ure s 1 ( a) a1J.d 1 (b ) , respect ively .

The pi tot tubes we::'e !Hounted for the callbra-cion tests on a long support tube lecated aD._rox::"mately in the center of the tunne1 . The suppor t tube , aving an outside diameter equal to t~at of the -pitot - tube adapter shown :n figure 1, for med a re~rward extension t o tte ad s..::'t e r , and was su_,rorted by two se ts of wi r e s which were fastened to the tunne l walls . Each set consisted of three wires snaced 1200 apart . One set of wires was attached to :':,11.e supcort tu e 3 inches downstrea:l1 from tlle adapter , and t:l~ othe r set was 8 inches farther down­stream. Figure 2 il lustrates this type of mounting .

Changes in the angle ef at tac k were made by r ota t ing the su~port tube in a plane '1',11.1 ch nas sed thro .l.gh the axis of the instr ument and the c.rain holes . The r otation wa:.:> made so that the n ose of the p::..tot tube 2etained its locat io ap~roximately at the center of the tunnel.

I '"}:{lBOLS

p s t;re an s t'1 tic ~;re 3 sure

H str ea., total prese're

H I total rre s sure ind icated by ins trumen t

~.~ sere a:-n Mc.ch numbe r

a anele of ins t r ument axi s wi th l'e spe c t to air flow

area of total - pr essure duct in region of pres ­sure H I

area of one drain hole in tube havinb j" equal ­diameter dr ain ho l es (NA2 is total orain area )

5

PL

lo cal static pressure a t drain hole

VI veloc~. ty at area Al

velocity through c rain hole

p stream mass de::1.sity ( at a static rressl1.re equal to p)

P~I ~tagn~tion mass de ns ity (at a static pressure equE!.l to H)

R::'::St:"Lrs l~}TD DISC~JSSIO:T

Tho error i::1 the meC;i.su.:."er~ent of total -r;ressure for a pi tot tube at 0 0 an£., l e of attack resul L .. ng from the presence of drain ho l es can be estinated by using the equation of cont inuity o.nc. Bernoulll 'S equation for an incom1)re s sibl e flow. Berno1.11li ' s equation is

From whlch

and

) 2 __ ·1

Ii - H' I - P 2

as 3'J..mi.1.::> <1n orifice coef'fi c ien t of J . 8 t:!l.e B'lua ti on of continuit? is

e limina t:Lng V

( 1 )

6

Th s

r.:H No . L6A08

The pressure coefficient for incompressible flow is

P = P1, - P Ii - f-'

H - I

Ii

- P7.,

- P

. 2 H - :1 ! ::;: O. 6LN2( A2) (1 _ p) H - D Al

~ \

(2 )

This relation shows that tL~ effect of locating the dral. hole in a l ow - res sure or hiCh- v~locity region woule: he to increase the e:C'r')I' J.n the reo.dLl:;J . For pitot. t1~es having d r ain ~o lvs located one or more tube diar eters behind t~!.e nose , however, the ~:.nC'uced ve l oci ties at the dra.i.n ho l es wou l d be s mall . Tr-~e resulting value of the Dress~re coefficient P would ~e between 0 and C. C2, as "i. nClicated by r ecults .f rom an u:1publis:1ec. pitot - static tub '3 investigatIon, J.ncl tllUS the assump t ion that P equ'lls zero wonle:. introd-lce n '3g1ig l ble error . Sl~atio::1 (1) thenlJeco:nes

_·=_-_X! ~ O. O~i.,.2(.~2..\ 2

H - P ~~

~he e3t~m~ted error in the ~easured total oressure at 0° 8.. g le of a ttack f o::.' the:' biO )':' tot tubes b~sed on mea1]ured dimension &nd equation (j) are : 0.0006 and 0 . 0J09 fo.' thG KAF No . 1 and the ~ollsrnm ty,e G- l pitot tu:!e , 1'e. sf'e c tl ve ly . A cO:':'.pal"lson ",'i th the re .sul ts presented in figure 3 shows ~hat c~e ex~erimanta l values at a lvi' ~h nu::nber of 0 . 2 are 1::1 Gxcel l ·3nt t:t€::ra8r:lent with these estimated values .

Previous expeI'lmental results (reference 1) have sho'rn that the j agni tude of u1~e Grror in the total­pressure measurem'3nts decreas~s slibhtl~ ':.ith increasing Mach nm.her . It can ~e aeen ~n figure) that the effect of c0l:1~·cess1 ' ility on the tot2.1 - p]:'essure error of these pi tot tu"'Jes i3 in agr ee1nent with the results of refer ­ence 1 .

o co Lf\

~

MR No . L6A08 7

I~ an effort to dete r mine the facto r s which produce a reduction in the magnit ude of the total - pressure error with increasing Mach number the -orocess whereby equa ­tion (3) was derived was r e-oeated for com~resei~le flows . It w!:).s as S'..lJlled that the pre 3 sure at tne crain ~Lole was eq'...l_al to stream stati c-pressure , velocity VI was small, no losses were incurred in t he flow un to the plene of the drain hole, &nd t hat the assumed discharge coef­fic! aht 0. 8 was c onstant . The resulting equation is:

r - H I o .64N2 ( A2 ~2 L 1 ,1 - (4 ) --H - p \ All PH 1_;2 r.:4 1\16

I + + + ~ I -1'0 1600 Ll- Lt-

If t~e subscripts th~ incompressible then :

i and c are used to differentiate and compressible forms, respectively,

__ (!I -\II

H ~ P) i

1 +

1

+

I'

roO I.

1600

Silica - the ls.st t'vo ter-::.s of equat::'on (5) decrease with L1creasing i;ach r..umb-:-I' , the relation shows that the tot 1 -;res3~re error shoul~ Gecrease ~:th increasing Mach nwnbe:... . LI J..:. ... ~~:? r , the large s t cf))1trL~uting factor to

--~----- 1

this dec r ease is the cl:unJe in ~_.'Jnsi ty . The a:"'fect of cO:L";Jressib~lity on t~1.is er2. ... or .lS det3i-'mined ':Jy e'1uation (5) is C:10rrn in fig~lre ,: .

Tl~e re suI ts of the cal i';.)ra tioD te s ts on the l'L-l.F :')0 . 1 [l:2. tot tube Cl t various nn51e s of attack are presented in fi ~ure 5 . It can be SC3n that the angular ra t -lf;8 wherein the error is essentiall"! equdl to the value Cl.t 0 0

lS li1'1ited to ap')rox:'rnately :1 0(:>, although the rate of change of error with ngle of &ttack beyond 100 is not Ll.-;"'~~g cOi:lpared to t~8. t for as:; V_DIe ::,i tot tube . (See reference 3 . )

A comparison of the results for the positive and negative cO~1ditions at a, given angle of attack shows that

~------~--------------------------------------------~--- ~

8 iiiR ~{o . L6A08

the di : ferencesare gene rall y within the scatter of the

test potnts .

An examination of the test re sults and the cu.rve

giving the limiting error for a reduction in velocity of

1 mile Der hour une e r standar d concitions shows that the

angular - r ange for this limit i ng error decreases frClm ±2ho

a t a I-Ilach nUr!1be r of 0 . 2 to ±2l 0 a t a Mach n1.,unb e r of 0. 5.

It can b e seen t hat the effect of compressibility

on the error, e ven a t t he higher angles of a ttack , is

in agre e;:nent with the r e sults sh own in fi gure 3 and

reference 1 . The change ' 1n t he magnitude a t the se

h i ghs r ang les of at tack i s such t hat t he error at a Mach

nU'1lb er of 0. 5 is a pprox':'mate l y 80 pe rcent of t he error

at a hiiach nu1:.tber of 0 . 2 . It is i n t ere st i ng to note t hat

a change of 86 pe rcent wO'J lci ha ve bee n pred i cted b y

equa tion (5) or f igure 4 al thou ::);. no effect of angle of

attac k wa s considered in t h e derivation of equation (5) .

CONC LUDING R~;MARKS

T le error in total p res s ure i ndicated by .a pitot

tube '.v:L th drain hole s at small o...11 c; l e s of attack can be

estimated , and this e st imu t ed va lue or an expe rimentall y

dete pmin8d value can be extr apola ted to h i gher spee d s.

These calibration tests indi c a t e t h at the accuracy of

the e stima t e d va lue s vvill be lfl l t h tn re a sonab le limits.

Langle y Iemori a l Aeronautical Lab oratory National Advi s ory COl ~it tee f or Aeronaut ics

Lan6 l e y Fi eld , V •

J

I1IR No . L6A08

1 . Hensley, Reece V.: at High Speeds .

9

REFERENCES

Cal i b r a tions of Pitot - St atic Tube s NACA ACR , July 1942.

2 . Kie l, G ~: Total-Head IIIeter with Smal l Sensitivity to Yaw . NACA TM No . 775 , 1935 .

.3 . Hump hreys, Mi l t o n D .: Eff'e ets of Compressibili ty and Lar ge Angles of Yaw on Pressure Indicated by a Total - Pressure Tube . NACA RB No . 15C30, 1945 .

~~ ~- - .~~~~~----~~--

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I

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Cl)

a. ~ ..-c: 0 E (f)

0 ~

. o Z

LL <[ Z

MR No. L6A08

(J)

Q)

.0 ;:j ..., ..., 0 ...,

• .-j

Q.

rl

Q)

l-< ;:j bD

• .-j

ex.

_J

~. , It\ I I

.....:I

Support wires

Air rlow

MR No. L6A08

Originol walls

~

Present walls rormecl Py /loIs

Cross -IL//l/le / a,Zls

Plolle of calibrated

-+--+---:5 to tic pressure orifices

NATIONAL ADVISORY COMMITTEE fot AERONAUTICS

F/gvrf:? ;? .- /VA F 170. j p/iol l ube moun ted //7 Ille lesT section o/I/;~ 24-//'1c/J h/.9h -speed tU/lnel r or co//bral/on

MR No. L6A08

H· H-,

~ ",- I ";· ;j-l

>-~ i-,.; Lt cx~ OJ !!! I::i:

~: ~:t <C

i-h ~~ F1

z ... Ow l-

e-< ~I-

I ='"'7 'Cz Zz

, - , -;" ITrH 8 p-'

I ~. Y

':=+ I--'-:c' '. i.;.... T

I-,:'.;:) ? t-h-i

1+1

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: ,~ !=+-!:I. ;

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,~!- I+,-" r.., 1 :;-;+ I+f-o---

. ' 1i "-n ': ~~' ~ , Itt:: I ttl:\: it!! ' 8:~ ,

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:j-

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~ :"-" 1- fE '£Eft ~ :-2i~~I -i- Wf~-:;.cC 'r

pc = , ~:- ,- riC . j:..

-- :.+::7. '~ ~~ :U~'J·· ' '1+ ~gb .. 1+ --. -, ~.m- tl i:t ..... f-' t, +-~

'++ $ It :t: :tW4:~ ::""- lli: . - t'

p:~ b ..... ' }ilt ~ :tf] 7_=" ~~

.j- ' IL:1,~' ~': ~;:j:;:! l+iTi tlfil:;-I ~ ·~ : 4 ++ --~ . :.,.,.. R+ -,~ .,,_ ..... • .+ H i~ h 1·"1 '-+,-1'-++' H+

: -~r.1;= It~? . . , 1:+,;:1 ,.., fl-\I, ;'1-' It

i::tL H"'-' 1+;

i:=+· ~ J+; Iti:; Ftl:) i:1\ tfj..f l ~~ TI-"; ,':;t

. ~'-IV !.j I:;j ~4 1':1 ij !#~ft; .-~

R r- h- I+" i-i-'- ' >+t r 4-"-' '" , - '':: [::0 /L.. .. >.;..~

-e li:; +-i-i h+" I~b~ 1 4 ~ '':; I+l I .. ' fl'i

~: :Ii f ] g !f 1;::':1 . 'n 1ftE,ttC;~ L~ ·brr.:lL ~~ _F"f 0.'

11['- 2 g~\_J &-:t ~J~ 1:.::2 ~-t Ittt l?]~ liJ~F ;::~ I '4. I P tt ~c~;

i rio I _:'~ I :;-~:, I '-;' Wi-! 1-15 1-4+f !=:~; I - kt~at t~ I~~ !k L-:1 tr~ i '" ; L:t:- :i [ '~\~ f,,~,., +: fT O:; tm' -F IE~fj~~+ '-'~ ~I:F-W

'i-!

1-<- · -\-r,:)r.'· n

~I . ~~%IIJ i'!- , '--r ~ fr- I'~ l~l~iij~ " I~~}bft£ ~'2:Ji:t Rt fi~ ';: ,,~r.:1 ,

..."!!' I- ' ~IVV~ ~ ~ liJ.t ~f.! l ~FFfFh;'~ !mYr".!.i '" " e ~. :tl ~ ILl r:: - , 7' -..P::-

~ ! f*-ift·'· ., j J~: t~~~~ ~j' .j." , ~ ,- rit ': .1-

... TT I - 1 '7" I' c I- 1-,... ..' ,f-'

o OJ

'" I H

_. -- - - ------ --

-:+

MR No. L6A08

: .. ~t~ i::C: tii_ t' i. lC: , ~

l;ft ffi ! '1~ ~"t . ~ fB I tt ~m8: r+t:B I ,:"c W t j.L '"' I .. ~:;:r;. ' ~ ""-;- ';.

·"' i ::F'~]::i~· JI-'1 ~i:tJt ~ T.ffL.,.. ~ :l' ~ ~:

:;:L+~. ~· b~. -~ F.t'"

~,i; :lttj~' j:1 :r!,~: " _ ~ ~ ~J: :~ '1 f:i '" 'i :p j:j:l ~:-,.. ,_,~'8 t fi lfd:t ~

~f!~ tj ~ Ii. , ~t:} -: II:J+t t:1 ~ . .,..; I; L ,

I ~=I+'

, f+, fh +1 Ii~~~ ~ H 111. ~l ' ;p ~..:. 1iZ1 It: I~ k:;~

~ f+t c:t:i" ' He' t'1 'f it' I 'f# ~l l~ ~;L~ d: !::t ,~ 1:+ YeLl c;.J. ::;:O'ltrS ,., [t F+- / I.... ~~J:~~t- I ~·

. ~ P=t l-;.-;±f i:i:j: Il:t m H-+ ~~i:j:j. Cl- ': ~ l'" :i 'i~$:j±'~ ~t"...: ~ r"'" '- ~';',,- A:p~~r. ++ -~tt ifLI.m1:4 14:4 "'" fh +H i"; t~~ . ., ' " '.;:: :g ~ i!':..11 1:tZ " to! -I

~ ':f-il /Ail + n r::::tt ~rj1~ -'-J ~ '''":; +I ' iitl - -1# :}-:.I ,_

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111

~ 'rtr ' I ~~ ay' ;:-:1 t;;~ ' 11 I

fiIf' I.Ltj

,II ' '.1

m ~. p.. . It"-

;t' t;t~ fll i.

!fu ' 3f' . Fit fH i:$ I £l!ff:i: .

ft.' I ,;

MR No. L6A08

II '1 ~I ':_ ;~ , l'llb

, 1;-"- ~" I

cM:W~ , '1r

. ',c IT! ~H;. 'n 'iilir?'

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