USAARL REPORT NO. 76-6

THE USE OF OPAQUE LOUVRES AND SHIELDS TO REDUCE REFLECTIONS

WITHIN THE COCKPIT: COMPUTER PROGRAMS FOR TWO APPROACHES TO THE PROBLEM

By

Wun C. Chiou, Ph.D. CPT Frank F. Holly, Ph.D. SP5 Chun K. Park, B.S.

Alford A. Higdon, Jr. B.S.

US Army Aeromedical Research Laboratory Fort Rucker, Alabama 36362

November 1975

Final Report

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Disclaimer

The findings in this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents.

..

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·' REPORT DOCUMENTATION PAGE READ INSTRUCTIONS BEFORE COMPLETING FORM

I. REPORT NUMBER r GOVT ACCESSION NO. 3. RECIPIENT'S CATAL.OG NUMBER

76- 6 4. TITL.E (•ond Sublllle)

THE USE OF OPAQUE LOUVRES AND SHIELDS TO REDUCE 5. TYPE OF REPORT lit PERIOD COVERED

REFLECTIONS WITHIN THE COCKPIT: COMPUTER PRO- Final GRAMS FOR TWO APPROACHES TO THE PROBLEM 6. PERFORMING ORG. REPORT NUMBER

7. AUTHOR(a) 8. CONTRACT OR GRANT NUMBER(a)

Wun C. Chiou, Ph.D.; CPT Frank F. Holly, Ph.D.; SP5 Chun K. Park, B.S. and Alford A. Higdon, Jr., B.S.

9. PERFORMING ORGANIZATION NAME AND ADDRESS 10, PROGRAM ELEMENT, PROJECT, TASK

Bio-Optics Division (SGRD-UAO) AREA 6 WORK UNIT NUMBERS

US Army Aeromedical Research Laboratory DO Form 1498 Fort Rucker, Alabama 36362

II. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATE

US Army Aeromedical Research Laboratory November 1975 SGRD-UAC 13. NUMBER OF PAGES

Fort Rucker, AL 36362 21 14. MONITORI~lG AGENCY ~lAME 6 ADDRESS(ll dlllerentlrom Controlllnll Qlflce) IS. SEI;U RITY CL. ASS. (of thla report)

USA Medical Research and Development Command Washington, D.C. 20314 Unclassified

I Sa. f~~ft~t1rf1CATIONIDOWNGRADING

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This document is unlimited.

has been approved for public release and sale; its distribution

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18. SUPPLEMENTARY NOTES

19. KEY WORDS (Continue on reverae 11lde II necessary and Identify by block nUIIIber)

Computer Program Light Shields Reflections Cockpit

20. ABSTRACT (Continue an reveree elfllf II nece .. _,. .,d Identity bJ' block number)

Opaque shields can be used to channel light and thereby reduce reflections within the cockpit. These shielding devices range from the standard glare shield on to~ of the instruwent panel to the more experimental use of Light Control Film and Micromesh for this purpose. Previous work in this series has demonstrated two mathematical approaches to a specific reflection pro-blem in the AH-1 aircraft, namely, the reflections coming from the portion of canopy directly above the gunner's head. It was felt that it would be use-ful to demonstrate the comnatibilitv of these twn .:~nnrn.:~rhPc:: .:~nci tn n11hlic::h

DO I ~~~~~73 1473 EDITION OF I NOV 11!1. IS OBSOLETE UNCLASSIFIED SECU .. ITV CLASSIFICATION OF TNIS PAGE (II'JI,.. Dale Bntered)

UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PAGE(II'IJ., Dill• BnteNd)

the computer programs (FORTRAN) for each approach for possible use by others.

UNCLASS I FlED SECURITY CLASSIFICATION OF THIS PAGE(II'hen Data Entered)

SW~MARY

Opaque shields can be used to channel liqht and thereby reduce

reflections within the cockpit. These shielding devices range from

th~ standard glare shield on top of the instrument panel to the more

experimental use of Light Control FilmR and MicromeshR for this purpose.

Previous work in this series has demonstrated two mathematical approaches

to a specific reflection problem in the AH-1 aircraft, namely, the

reflections coming from the portion of canopy directly above the gunner•s

head. It was felt that it would be useful to demonstrate the compatibility

of these two approaches and to publish the computer programs {FORTRAN)

for each approach for possible use by others. •

~~~ COL, r1SC . Commanding

INTRODUCTION

One technique of reducing the reflections of the instruments,

dials, etc. from the transparent enclosures is the use of opaque louvres

and shields. In using these screening materials, one wants to maximize

the extent to which they block light from reaching the canopy but mini­

mize the extent to which they block light from reaching the pilots•

eyes. This is accomplished by choosing the proper values for the posi­

tion, width, spacing, angle, etc. of these shields.

In a previous report 1 we showed a set of mathematical equations for

the solution of this problem in terms of analytic geometry. Quite

independently, the problem has also been investigated by a different

mathematical method, namely a plane geometrical and trigonometrical

method. The latter method will be documented elsewhere 2 • Regardless of

the different mathematical derivations, results from these two the­

oretical_predictions of the reduction in interior cockpit reflections

were essentially identical. The purposes of this report are to de~

monstrate the compatibility of these two theoretical predictions and to

document these two FORTRAN computer programs.

ANALYSIS

Due to the nature of the problem, visibility has been classified

into three cases. We denoted the projected points of the lower and

higher points of the louvre to the vertical axis of the pilot's position

by h and H respectively. Case I concerns the vi si bil ity VI above H.

Visibility VII (Case II) is the region between H and h. Below h,

visibility V is classified as Case III. Since Case II is relatively III

trivial and since Case III is similar to Case I, we will show the equa-

tions for Case I by.these two methods.

a. Analytical geometry method:

d1 tan 0 - k1 VI = 1 A IC I + k1 tan 0

(A)

Where VI is visibility, c is the distance between louvres, d1

is the A

thickness of the louvre, 0 is the decline angle of the instrument panel

and k1 is constant. All the symbols were explained in the original

paper and are shown in Appendix I (incorporated with notations in the

computer programs).

b. Plane geometrical method:

V = K I B

2

(B)

Where VI is visibility, K is constant, h is the minimum height, H is B

the maximum height, 0 is the decline angle of the instrument panel and

a is the extended angle.

A detailed explanation of the symbols in this equation is als6 given in

Appendix II .

. SOLUTION

Computer programs for equations (A) and (B) are attached in Appendices

III and IV respectively. Comments and notations used have been added

in the programs except for the graphic portion of the programs, which

required a few calls from standard subroutines, and were plotted through

a hybrid computer p lotter 3•

Results from both methods have been represented by two graphs

(Figures 1 and 2 correspond to methods (A) and (B) respectively.). They

were indistinguishably identical. (The vertical axis showed the nor­

malized visibility and the horizontal axis was the vertical distance

with respect to a referenced ground point in the Cartesian coordinates

system. There are six curves in each graph with each curve representing

a different louvre width. These graphic representations enabled us to

determine the amount of visibility of a pilot under a set of predeter­

mined cockpit parameters.

3

In short, this study has presented two different mathematical

formulations which produced identical solutions for the analysis of the

use of opaque louvres and shields to reduce reflections within the

cockpit. It has also documented two computational procedures with their

respective computer programs for future analyses of cockpit light reflections.

CONCLUSION

Previous work in this seri.es has demonstrated two mathematical

approaches to a specific reflection problem, namely, the reflections

coming from the portion of canopy directly above the gunner•s head.

Although these two studies addressed a specific reflection problem, they

each represented the modulus of a general approach to the canopy·reflec­

tion problem. Therefore, it was felt that it would be useful to de­

monstrate the compatibility of these two approaches and to publish the

computer programs for each approach for possible use by others.

REC0~1MENDAT IONS

In future canopy design, it is recommended that an analysis of this

sort be carried out prior to fabrication of the canopy and cockpit. In

this way, some potential reflection problems could be prevented without

having to initiate costly re-designs and product improvement programs.

4

REFERENCES

1. Chiou, W.C. and Holly, F.F., 11 The Use of Opaque Louvres and Shields to Reduce Reflections Within the Cockpit: A Mathematical Treatment .. , USAARL Report NO. 75-22, June 1975.

2. Park, C.K. and Holly, F.F., 11 The Use of Opaque Louvres and Shields To Reduce Reflections Within the Cockpit: A Trigonometrical and Plane Geometrical Approach, .. USAARL Report NO. 76-4, Sep 75.

3. We thank Dr. H.D. Jones of the Hybrid Computer and Analysis Branch, USAARL, for establishing the plot portion of the computer programs.

5

.9

.f

~ ~

~~ ~ r? 0 z 0 "

~ ~ =i • < u ~!:! ~ = z = ~,§ ~

- ~ ~ b ii:l ...r ;

i5

i= .5~

:>

.4-

.:3

.z

.1

12 15 18 "21

Height (inches)

24 27 30 33 36 39 42 "TS

FIGURE 1. Visibility as a function of height ih the plane of the gunner as determined by the method of analytic geometry.

.f

.f

~ ::i ~ ~ ~":' I z 0 ~ u

I ~ § .6

115

t >-t-

.5~ ~ :>

.+

-~

.1

12 15 18 21 Height (inches)

24 27 30 33 36 39 42 1-S

FIGURE 2. Visibility as a function of height in the plane of the gunner as determined by the method of plane geometry.

APPENDIX I

ANALYTICAL r,EOt1ETRY ~1ETHOD

COL. INPUT SYMBOLIC HEADER COM~1ENT (4 Decimal) CODE CODE CODE

1-7 A a A Distance from panel

8-14 B b B Distance the louvre is up the pane1

19-21 c c c Distance between the ------

louvres

22-28 Dl dl D Hidth of louvre 1

29-35 02 d2 02 Hidth of louvre

36-42 E 0 E L 0

43-49 ORGN ORGN Beginning point

APPEt'DIX I I

PLANE GEOMETRIC METHOn

COL INPUT SYMBOLIC HEADER COMf'-1ENT (3 Decimal) CODE conE CODE

1-7 A t. L Starting width of louvre Program Increments dy .003

·8-14 B a B L a

15-21 c K K Distance between louvres ------

22-28 D H HF Starting height to be varied + 10 by .25

29-35 E a A Height up the panel

36-42 F e T L e

43.;.49 G ~1 M Distance from panel

APPENDIX I II

COMPIJTER PROGRAM (a)

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APPENDIX IV

COMPUTER PROGRAt1· {b)

1/11/7'1

1 ,.

6 7 8 9

I o 11 12 13 14 15

1 7 1 R 19 20

?.'? . ?A

27 ~Fl 2'9 30 31 32 33 34 -~5 36 37 3R 3Y 411 41 42 43 44 4S 46 47 41'3 49 so 51 'i2 93 54 55 ~A 57 s~ '19 60 131 62

•63

73 74

1_ 1 S ARtvlY Af.ROMED RESEARCI-l LAB

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COi'AMOI\f I01oiVl C ICONV IS MAX SCALE FRACTION

' -CXYXYXYXYXYX~XYXYXYXYXYXYXYXYXYXYXYXYXYXYXYXYXYXYXYXYXYXYXYXYXYXYXYXYX~ C' THIS PARI l)f THE PROGRAM C::F'TS liP THE GRAPI-l!NG

CALL If\IIT CALL SAC~C1,IERRl

PL\USE FULLSC IDl=IVl=O CALL L80ACOoloi01,IEPRl PAUSE nRIGIN -

CXYXYXYXYXYXYXYCYXYXYXYXYXYXYXYXYXYXYXYYYXYXYXYXYXYXYXYXYXYXYXYXYXYXYX' WRITE<~•240l .

240 FORMATC1Hll . C 1\~CD A~C!')MCt lA ACt) A~Cf}Af'3CDA !'lCEJ AF!CUA~C El A ~ti')MCOAI'ICf'MCOA~CDABCO.A~CF) ~~~CDAB C Et>CH OF THESE HAVE 3 DECIMAL PLACES C A = STARTING WlrHH OF I OUVRE PROGRAM INCREMENTS BY ,003 C R - THE ANGEL OF T~E LOUVRE C C = DISTANCE AET~EEN LOUVRE C 0 IIF!GiiT OF PF.:PSO~J Tfl BE VAP!ED FOQ 29 INCI!gS QY .Ql C BUT H IS THE CALtULATEO LITTLE H C E =THF 4EIGHT UP THE PANEL WHfRE THE LOUVRE IS C F = I Fit ANGLE OF I HI'_ PANEL C G = THE OISTA"iCf FROM THE Pli~!EL CABCDABCnAACD6RCDA8CDARCDARCOA~CDA9COARCnARCDABCDABCOABCDARCDABCDABCDAB

2 READCSollAoRoC~O,EoF•G -1 FOR"'1ATC7F7.3) ..

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C · !II IS U5F::U AS TF1E STA~TIN\, ~lii!\IT ~=-2000 TFCAl3o4o4

·4 CONTI :\JUF:: C*********.**************************~********************************• C************;•****-1=*******-t'"***********.**********.*****;a-****************i C * THE 8IG DO LOOE INCREf"ENTS 11 A11 THE WIDTH OF * C * THE LOUVRE.. JI-lTS WILL rPAW THE DIFFERENT * C ~ t.IJ~VF"<;o.Ti=IE U'TTLf. 00 LuiiF DFlAWS Trl!: ·* C * CURVE IT SELF •• TOGETHEP THEY WILL DRAW 6. *

*************************************************

TAN=SIN(R-Fl/COS<R-fl*CG+CC+El•COSCEl-A*COS(8-Fll C H=THE HEIGHT AT ~HICH VISIBILITY IS 100%

D=H-20 01=0

C********************************************************************~ DO 23 M=N•2000 I~ (M):3J,<o'3o<i!'oi

33 .. CONTI \J!.IE . C THESE ARE Sf.T UP Il\l' r_,Y. FQUATIOI\I FOR "\1 11

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Ull/75

75 7F, 77 78 79 BO 81 1'12 83 84 85 86

.IH 88 89 ~(j 91 92 93 94 95 96 97 98 99

100 IOI 102 103 104 lOt;

c

G

c

G

c c c c

t":R<;LO II S ARMY I>"=RO'I.'Ffl f<ESF:APCH LAR

V = THE VISl8LE PORTION "!FLO'~ THE l_fiiiVRF V-C-DIV/CDIVER+DIVER2l GO TO 66

55 CONTI~JUE n..!fSt:: .'\RE <;ET UP lbl uy f-:0 11 <\TIOP! FCI< "V"

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101 L 1"1 AQ[ ~y X ~ Y }~ ~COlf fPACTJQN FOPM FOP @PAPHING IOl=ICO~V*CD-Dll/4U.Ol IVl=ICONV*V/C IFIIVl.LE.6liVl-O

************************************************* * THE REST OF T~IS P~Or.RAM T~ FOR GRAPHING *

IFC~. q,OlCALL DELAY IFCM.EQ.OlWRITE (6,230lO,V,~ IFIP1,GT.58f'lo4ND.VaLT.fi)Cil,ll IJELAY IFCM.G1.500.AND,V.LT.OlGO TO 5 IFCM.EQ~NlCALL DELAY 1F tK.EQ.IJCALL PENDOwN IFIK.EQ.1lCALL DELAY

229 TFIK 0 fA,}lWRIIEI6.230>D.UoM 232 CONTII\IUE

D=O+.Ol

C******************************~*****************~************~*******' D=D-.01

CALL PE"'UP 20 A=A+.003

C*~-~~M.MNM~f*******nKnMMMMfi~HMNMKMMMM~**"f*MM~MM~MMMMNM**MMMnaan•~~~a~ 0.**** *** *** ****** ********* *** *** **** * * *** *** *** *** *** ** * •.•• *** *** *****~ GO TO 2

. . I-118 . 230 FORMAT(•O•,• X=D=HIAH= •oF9.4olnX•'Y=V~VISI8LE= '•F9.4~4Xol6l ~------~~+Y~------~--------------------------------------------~---------120 E:ND 121 CSUBSUBSU8SIJBSU8SlJASUBSURSUPSLHSU8Sl! 122 C SUBRIJTINE TIIAT PICKS PH( UP PUTS 123 C, SETS UP 1\ DELAY FOR PL0TIC\JG PURO 124 SUAROUTINE PE:NUP . 125 cALL A5CLC15,!ERR) 126 2 DO 1 N=lo20000

136. 137

RETUR!-1 ENTRY PENDOWN CALL SSCL!lS•IERRl GO TO 2 ENTRY DELAY DO 3 N=1,3ooooo

·3 X=O

RETURN .

~I •t:C:UPSUPSIJI=lSU8SU~'~SUBSURS URSURSURS f'.l AQ~II\:lu AI_SO

139 140 CSUBS UR SUBS UR SURS U8S UBSUBS 1.18 SUR SUR S I!R S IIR S LIR S I.!R SUR S I.JRS URS UA SUR 5 UR S U8 SUBS

142 143 14"4 145 146 147 148

$ASSIGN! LI8=HYBLIR DIR=HYRDIR u 55 I G!\12 s=svr $ASSIGN2 6=SLQ•7000 $ALLOCATE 0000 $0PTI 01\:J NOMAP $EXECUTE GO . • ols,9o.o •• ol~3o.o,s.o~ss.o,27.o

7jll/75 08:28:16 II <; ARMY Al=qQMEO RESFARCH LA4

·:t49 -0001 150 $EO.! 151 '!i$·