Investigation of eye movements of an aircraft pilot under blind approach conditions

(1)

THE COLLEGE OF AERONAUTICS

CRANFIELD

INVESTIGATION OF EYE MOVEMENTS OF AN

AIRCRAFT PILOT UNDER BLIND APPROACH

CONDITIONS

by

(2)

Wm NO. 26

MAY, 1?,^^.

T H E C Q L L E G - E O F A E R O N A U T I C S

C R A N F I E L D

Investigation of

Eye

IJbvements of an Aircraft

Pilot under Bland Approach Conditions

-by-A,F.A, V/atts, D.C.Afi.,

and

H.C, Wiltshire, M.Sc.,

M,I,Mech,E,, M,I,I,A,

STOMARY"

Eye movement patterns were obtained of a pilot in an

aircrcft fitted \7ith a standard R,A,F, blind flying panel on

several approaches under Standard Bean Approach conditions,

These patterns were obtained'by photographing the

reflection of the pilot's eyes in a mirror attached to the

instrument panel,

The results show the

(^)

Rroportion of time spent on each instrument,

2) Diaration of the fixation time on each instrument,

3) Frequency of the eye fixations,

(4) Sequence of eye movements,

It \7as originally intended to investigate the eye

movenents on an I,L,S,approach using the Zero Reader and I,L,S.

Cross Pointer independently, Unforseen difficulties and delays,

hoivever, prevented the completion of this part of the investigation,

This Note is based on a thesis submitted by

A,P,A, Watts in partial fulfillment of the

requirements for the Diploma of the College

of Aeronautics,

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2

-IJST OF CONTENTS

Page

1• Introduction 3 2, Description of the procedure for recording k.

eye movements,

3, Results of film analysis 8 (a) Proportion of time spent on each

instrument

(b) Duration of eye fixations (c) Frequency of eye fixations

(d) link values between instruments,

2f, Suggested procedure for future experiments, 20

APPENDICES

1 • Methods of measuring eye movements 21

2, Standard Beam Approach, 23

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1, Introduction

One of the greatest problems of commercial and

military aviation is the landing of aiixjraft on a given airfield tinder imfavourable v/eather conditions,

The problem of visibility affects all fonns of trans-portation to some degree, but unlike surface vehicles, an air-craft is compelled to land regardless of weather conditions after a specific time,

G?his landing procedure is performed by pilots vd-th the assistance of various radio and radar aids, but it must be

emphasised that it is the pilot who lands the aircraft and not the equipment, however good it may be,

No effort has been spared to ensure wherever possible that the pilot has at his disposal the latest and most reliable navigational aids in order to make his vrork less arduous and complex,

Several attempts have been made to land an aircraft solely with the use of radio and servo mechanisms, and in one case the Atlantic Ocean was crossed successfully by an aircraft taking off and landing %7ithout any human actuation of the controls, While this v/as a remarkable feat it has a limited scope at

present due to the bulkiness of the equipment required, It may be accepted that the equipnent available to the pilot for navigation and blind approaches is technically sound and functions consistently well providing the equipnent is adequately maintained,

A problem still remains, however, in ensuring that the individual flying the aircraft functions as consistently and as well,

Most commercial pilots and certainly all service

pilots have been trained to fly to a strict and rigorous training programme in an attempt to eliminate inconsistencies as far as possible,

Each pilot T/ill, hovrever, tend to fly an aircraft

either visually or by instrui:ients according to his own particular style, and the differences betvreen trained pilots may even be apparent and measureable»

When flying Tander\isual flight iriles these differences nay be ignored but -when flying under instrument flight rules, any idiosyncrasy, especially on an approo.ch, may have a

disastrous effect,

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4

-The physiological and psychological reactions of human beings v/hile flying have received considerable attention at the R,A,F, Institute of Aviation Lïedicine, the U,S,A, Air 1/Iateriel CcxïBnand and the Applied Psychology Unit at Cambridge,

The need for instruments which can convey the correct information iji the shortest time has been realised by the

instrument manufacturers, but it is very djoutbtful if aircraft designers seriously consider the movements of pilots' eyes when arranging instruments on the instrument panel,

It is felt that consideration should be given to the link values of eye movement between instruments for all critical manoeuvres before deciding on a new instrument layout,

2, Description of Procedure for Recording Eye Movements

(a) Selection of Procedure

The method selected in this investigation was that suggested by Dodge and Cline, that is by direct photography of the eyes,

This method is comparatively simple and is adequate for such cases where there is no necessity to record such small eye movements as 10 minutes of arc.

Because of the difficulty in mounting a camera directly in front of the pilot, the reflection of the pilot's eyes in a mirror was photographed,

No trouble w^as expeidenced from vibration in the particular aircraft used for the investigations and the photo-graphs were quite sharp,

Alternative metSxids of measuring eye movements are given in Appendix 1 •

(b) Aircraft and Equipment

An Anson Nk 1 was fitted ivith an R,A,F, standard blind flying panel as shovvn in Fig, 1,

A mirror to reflect the pilot's eyes was moxmted on the inside of the cowling above and to the left of the blind flying panel and adjusted so that the pilot's eyes were reflected directly into the camera,

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FIGURE 1.

R. A, F . STANDARD BLIND FLYING P A N E L

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é

-Fig, 3 shows a viev/ of the pilot vd-th the mirror in position, and Fig. 4 shows the mounting of the camera,

The camera, a Paillard Bolex 16 mm, cine' camera fitted ¥/ith a 3 inch f 3,5 Dallmeyer telepho lens, was fixed on a tripod between the main and rear spars,

The tripod v/as mounted on three floor brackets and tied dovTn to the floor with bunjy to a central bracket,

It was originally intended that the floor brackets for the tripod should contain hard rubber inserts to eliminate

vibration during flight. These inserts were eventually removed hovrover, because although the rubber served as an excellent shock

absorber, it did not eliminate the vibration, on the contrary it enhanced it considerably.

In order to simulate blind approach conditions without restricting the photography of the eyes, the pilot v;as fitted v/ith

a hood similar to an arc welder's shield,

The hood coniprised a vare frarae attached to the helmet and covered v/ith fabric, and ?/as adjusted so that the pilot could see all the aircraft instruments without difficulty. Any attempt on the part of the pilot to see outside the cockpit vrould result in the head having to be tilted in a very awkvïard manner,

It was found that there was no necessity for artificial lighting inside the cockpit, and although the photography took place on a dull morning with overcast sky there was sufficient light available to photograph with a stop of f 5«6 at a speed of 10 frames per second,

Kodak Super XX panchrcnatic reversible cine film v/as used having a Scheiner of 32°,

(c) Flight Procedure

Five runs v/ere made on the Standrjrd Beam Approach

(S,B,A,) imder simulated instrument conditions and a photographic record was made of the pilot's eye movenents,

A description of the Standard Beam Approach is given in Appendix II,

The Bolex cine camera was started a.t a speed of 10 frames per second ^xs the aircraft passed over the Outer Marker and a continuous record of the eye movements was taken imtil the aircraft passed over the Inner ïlarker, a distance of 9»250 feet and a flying time of approximately 70 seconds,

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FIGURE 3. VIEW SHOWING MOUNTING O F MIRROR

AND P I L O T F I T T E D WITH HOOD

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TECHNISCHE HOGESCHOOL

VLIEGTÜIGBOÜWKUNDE -Kanaalstraat 10 - DELFT

It was found necessary trcm safety oansiderations to

fly v/ith a sEifety pilot as other low flying aircraft vrere often in the vicinity,

(d) Film imalysis

For analysing the film frame by frame a small Specto projector v/as used,

Before the flights commenced, sample frames v/ere taken of the eye positions of the pilot when looking at each of the specific f light, instruments ,

These frames constituted a series of instrument location reference photographs,

TvvD projectors were set up, adjacent to each other, one projecting the reference photographs and the other the film taken in flight. Each frame was then examined and ccnpared with the reference photographs to determine which instrument was

being viewed,the tine base being obtained by counting the frames,

3, Results of Film Analysis

(a) Proportion of time spent on each instrument

The two instruments on -yrfiich most time was spent were the Artificial Horizon and the Air Speed Indicator, For the five flights the average tine spent on both these instruments comprised 62 per cent of the total time,

Although the general patterns of the proportions were

similar on the individual flights, there were appreciable variations in the cases of some of the instruments,

In flight 1 the proportion of time spent on the Air Speed Indicator was as high as 42,4 per cent at the expense of the Artificial Horizon, but this dropped in flight 2 and remained

substantially constant for the other flights,

The reason for this high proportion in the first flight is not clear. It may have been due to the pilot feeling his way or more probably that the pilot was accustomed to flying aircraft that were undergoing sone f o m of flight test where it is imperative that the air speed should be consistent,

/In flight .,. # A suitable projector with a counter fitted to enable the number of frames to be read directly is now manufactured by the Specto Company of Y/indsor,

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In flight 2 more time was spent on the Rate of Climb

indicator than in the other four flights,

This may have been due to a bumpy approach \/here the rate of descent changed with each bump, although this v/ould seem unlikely as a.ll the observations vrere completed in one hour and

the other flights do not seem to be similarly affected, Table I gives the proportion of time spent on eexih

instrument for each flight, and also the averages for the five fliglrits,

Pig, 5 shoT/s the results in graphical f o m ,

Table II gives the analysis on the basis of seven periods of ten seconds duration during each flight,

In flight 1 it Td.ll be noticed that there is a tendency for the time spent on the Air Speed Indicator to increase during the flight, v/hile in Flight 5 there vre'.s a tendency to decrease, No such trends occurred in the other flights,

T/^LE I

Proportion of Ticae Spent on Each Instruraent

(1 Frame = l/lO second)

INSTRUÏ/IENT HOR ASI D/G A l t R/C ENG. T/S fflSC,

F u s i r 1

No, of frames 173 293 77 78 26 11 12 22 692

t

2 5 . 0 ^ . 4 11,1 11,2 3 . 8 1.6

i ^ « 7

100,0 FLIGHT 2 No, of frames '261 185 56 41 137 8 4 7 699

t

31,k 2 6 , 4 8,0 5 . 9 19.6 1.1 0 , 6 IfO

iioo

FUGHT 3 No. of frames 224 172 12t2 87 63 5 4 9 706 lo 3 1 . 8 2 4 . 4 20,1 1 2 , 3 8,9 0 , 7 1 0 , 5 1,3 100 FLIGHT 4 No, of frames 245 214 96 81 45 6 2 6 695 '0 55.2 3 0 . 8 1 3 . 8 11,6

e.5

0 , 9 0 , 3 0 , 9 100 FLEGffl No, of frames 235 166 144 85 52 4 2 7

695

^ ^ % 3 3 . 8 2 3 . 9 2 0 , 7 1 2 , 2

7.5

0 , 6 0 , 3 1.0 100

/AVERAGE ,,,

(11)

10

-ARTIFICIAL AIR DIRECTIONAL HORIZON SPEED GYRO

INDICATOR ALTIMETER 32-6

29-4

RATE ENGINE TURN OF INSTRUMENTS & CLIMB SLIP MISC. 14-7 IO-6 9*2

n n ^ :^

1-5

PROPORTION OF TIME SPENT ON EACH INSTRUMENT (PERCENTAGE)

0-74 0-6: f ₍_3-64

1

( J'flS t 0-62 1 0-57 0 - 4 0

DURATION OF FIXATION CYCLE (SECONDS)

29-5

24-O

13-8 13.1

n n ±^ ±^

NUMBER OF FIXATIONS PER MINUTE

PROPORTION OF TIME, DURATION, & FREQUENCY OF FIXATIONS

ON AIRCRAFT INSTRUMENTS.

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AVERi\GE OF FIVE FLIGHTS INSTRUl-IENTS HOR ASI

p/G

A l t R/C

mo

T/s

b/KSC -A r t i f i c i a l H o r i z o n A.i.r Speed Indixjator D i r e c t i o n a l Gyro A l t i m e t e r

Rate nf Climb Tnrlicntor Engine I n s t r u m e n t Turn and S l i p I n d i c a t o r M s c e l l a n e o u s ( b l i n k i n g , e t c . ) PERCE]>?IAGE

32,6

1

29.4 14,7

1 0 , 6 9 , 2 1,0 1.0 1.5 100,0 TABIE II

TB'IE SPENT ON EACH INSTRmiENT

(in periods of 10 sees, duration of flight)

FLIGHT 1 FLIGHT 2 [PLIGHT 3 PERIOD 1 10 s e c , j i n t e r v a l s 1 1 2

3

4

6 - 7

TOTAL 1 2 3 4 5 6 7 TOTAL 1 2

3

4

5 1 6

7

NUlvIBER OF FRi\I;IES ( l Frame = l / l O s e c ) 1 HOR 23 26 24 22

32 1

30 16

17^

64

41 31 35 39 1 24

27

261 29 hh 40 19 30 34 27

1 1

TOTAL 1224 ASI

38

36

47

31 5^

293

10 33 31 33 27 22 29 185 26 11 28 22 26 38 21 '172 D/G 15

13

14

191

7 4I

77

5

3

6

11 13 13

56

14 28 22 19 30 10 14 | l ^ A l t

8 1

11

7

11 12 14 1^

7 8 '

3

6

12

5

0 0

i 41

1 15

13 3 18 2 16 20

0 0 0 ^ MISC, 0 2 i 8 j 3 ' 4 5 0 22 0 0 0 2 0 0

5

7

0 0 2 0

i °

2

5 1 9

T0Ti\L 100 100 100 100 100 100 92 692 100 100 100 100 100 100

99 699 1

100 1

100 100 100 100 1 100 100

6 1 706 1

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- 12

Ti'^LE II (Continued) T B E SPENT ON EACH INSTEUlvIENT

(in periods of 10 sees, duration of flight)

FLIGHT 4 FLK2ÏP 5 PERIOD 10 s e e s , - ] i n t e r v a l s I 1 2 3 4 5 6 7 TOT/iL 1 2 4 6 7 TOTiJj

NUlvEER OF FRz^^IES (1 Frame = l / l O s e c , ) 1 HOR 32 37 35 32 33 20 56 245 30 31 1 34

1 26

1 43

40 51 | 2 3 5 / ^ I 31 34 16 30 26 43 214 31 29 30 30 14 14 18 166 D / G 19

8 1

31 5 15 18 0 96 13 18 22 17 27 14 144 A l t 16 10 2 1 11 21 ! 16

5

81 13 13

1 ""^

i 1 1 6 2 4

4 1 85

R / C 0 11 16 14 1 3 0 45 8 3 0 16 10 8

7

52 ENG 0 0 0 6 0 0 0 6 1 3 0 0 0 1 0 0

i ^

T / s 0 0 0 0 2 0 0 2 2 0 0 0 0 0 0 • 2 M S C , 2 0 0 2 2 0 0 6 2 3 0 0 0 0 2 7 TOTAL 100 100 100 100 100 100 95 695 100 100 100 100 100 100 95

695 1

At) ...

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("b) Duration of eye fixations

The duration of a fixation cycle has been taken as the time required to move the eyes to the instrument plus the time spent in looking at the instrument before the eyes make the next movement,

Table III gives the average durations of the fixations for each flight and the avera.ge for five flights while Fig, 5

shows the results in chart fctrm,

The instmjinent vrith the longest fixation time was the Air Speed Indicator v/ith 0,74 second, v/hile the Artificial Horizon, Direction Gyro, ?jid Rate of CliKob Indicator follo\/ed closely v/ith

0,67, 0,64 ö^nd 0,62 seconds respectively,

It may be of interest to note that the fixation times for the jJ-timeter and Turn vnd. Slip Indicator are substantieJJy

lavier than for the other instruments,

(c) Freciuency of eye fixations

The number of fixations per minute of flight for each instrument is shorm in Table IV and the averages for five flights are also shmvn in chart torn in Fig, 5.

Frcsn Fig, 5 it is seen that the iirtificial Horizon, the instrument on lihich most tij:ae was spent, also had the largest number of fixations per minute, although tlie duration of fixations v;as lOT/er than that of the Air Speed Indicator,

From Table IV it is seen that a fairly constant pattern v/as follow-ed in flights 3» 4, and 5.

Table I shov/s that the proportion of time spent on the iirtificial Horizon in flight 1 v/as lov/er than in the other flights, The number of fixations per minute for this instrument however was highest in this flight (Table IV) and the duration of fixation

the lov/est (Table III),

(d) lArlc values betv/een instruments

Table V is an anrOysis on a sequential, basis of the nuraber of eye movements occurring betv/een the various combinations of two instruments,

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14

-T.'fflLE I I I

AVERiVGE DURATION OF ME PIXilTIOl©

INSTRTOffiNT iiSI HOR 1 D/G E/C ENG A l t T/S FLIGHT 1 No.of^ F i x , ^ 35 37 14 5 2 19 2 114 Av.per FJbc,^ 0 , 8 4 0 , 4 6 0,55 0 , 6 4 0.55 0,41 0,60 PLIGHT 2 No,of F i x . ^ ! 27 31 12 21 1 10 1 103 Av.per F i x , ^ 0 , 6 8 0 , 8 4 0.47 0,65 0 , 8 0 0,41 10,40 PIUGHT 3 No,of F i x , " 24 33 17 7 1 17 1 i 100 Av,per F i x , " 0.72 0 , 6 8 0 , 8 3 0 . 9 0 0 . 5 0 0.51 0 . 4 0 FLIGHT 4 No. of Fdoc," 27 34 15 8 1 14 1 100 Av.per F i x . " 0.79 0,72 0 , 6 4 0 . 5 6 0,60 0 . 5 8 0,20

FLIGHT 5 1

No, of F i x , " 26 36 22 11 1 16 1 113

Av,peJ

F i x , " 0 , 6 4 0,65 0.65 0.47 0 . 4 0 0.53 0 . 2 0

AVER/lGE OF FIVE FLIOiTS

i\SI HOR D/G E/C ENG

lat

T/S ^^ -~ -BTSTRUI/IENTS A±T Speeci I n d i c a t o r i o r t i f i c i a l Horizon D i r e c t i o n a l Gyro Rate of Climb I n d i c a t o r Engine I n s t r u m e n t / i l t i m e t e r Turn and S l i p I n d i c a t o r No. of F i x a t i o n s 139 171 80 52 6

76

6

530

Average Time p e r F i x a t i o n ( s e e s ) 0 . 7 4 0.67 0 . 6 4 0 , 6 2 0 . 5 7 0 , 4 9 0 , 4 0 / T a b l e IV . . .

(16)

Ti^IE TV

NITilDER OF FIXiiTIONS PEE ivriNUTE

INSTRÜIvENT HOR i\SI D/G A l t E / c ENG T/S FLIGHT 1 No, of F i x a -t i o n s 37 35 14 19 5 2 2 114 No. p e r iirLn, 3 2 . 0 3 0 . 3 12.1 16,5 4 . 3 1.7 1.7 9 8 , 6 FLIGHT 2 No,of F i x a -t i o n s 31 27 12 10 21 1 1 103 No. p e r m i n . 2 6 . 6 23.1 1 0 . 3 8.6 1 8 . 0 0 , 9 0 , 9 8 8 , 4 FLIGHT 3 No,of F i x a -t i o n s 33 24 17 17 7 1 1 100 No, p e r m i n , 2 2 , 6 2 0 . 4 1 4 . 4 1 4 , 4 5 . 9 0 , 8 0 , 8

79.3

FLIGHT 4 No. of F i x a -t i o n s 34 27 15 14 8 1 1 100 No, p e r m i n . 2 9 . 3 2 3 . 3 12.9 12.1 6.9 0 . 7 0 . 7 8 5 . 9 PLIGHC 5 No, of Fiica-t i o n s 3é 26 22 16 11 1 1 113 No. p e r m i n , 3 1 . 0 2 2 . 4 19.0 1 3 . 8

9.5

0 . 9 0 . 9

97.5

AVERAGE OF FIVE FIIGtlTS

INSTEUi:.iENT HOR - / i r t i f i c i . a l Horizon i'vSI - A i r Speed I n d i c a t o r D / G - D i r e c t i o n a l Gyro 1'J.t - / J . t i i : i e t e r E / C - Rate of Climb I n d i c a t o r ENG - Engine I n s t r u m e n t T / S - Turn and S l i p I n d i c a t o r No. of F i x a t i o n s 171 139 80 7é 52 6 6 530 No. of F i x a t i o n s pel- ni.TTute 2 9 . 5 2 4 , 0 1 3 . 8 15.1 9.0 1.0 1.0 9 1 . 4 / T a b l e Y , , ,

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TECHNISCHE H O G E S C H O O L ••VLi:C7ülGECUV/KUNDE Xanaalstraat 10 - DELFT 16

-TABIE V

SEQUEI^CE OF EYE MOVFn\,TFTNTS

'1 M1C1111! fl'^fTIjVMTilO L-IJNbiHUïi'inlNTb r / ^ I - H O R H O R - . ^ I HOR-D/G A i l t - Z ^ I D/G-HOR HOR-Alt / i S I - A l t HOR-E/C R/C-HOR Alt-HOR E / C - i i S I D/G-E/C ; ^ I - D / G

D/G-iat

D/G-ASI / i S I - E / C ! E/C-D/G / i l t - D / G

E/c-/at

AST-ENG A l t - R / C T / S - E / C E N G - M t D/G-T/S T / S - i \ l t HOE-T/S AiSI-T/S i J . t - T / S i i l t - E N G D/G-ENG T / S - / i S I T/S-HOR ENG-iiSI ENG-HOR ENG-D/G ENG-E/C HOR-ENG FLIGHTS

1 1

25 17 11 12

6

7

8

5

2

3

1 1 •

3

2

3 1

1 0 0 1 0 0 0 0 0 1 0 'l 1 1 1 1 0 1 1 0 0 0

1

114

2 17 16

8 1

^ 1

^

3

2

4

8 1

6

5

0 2 1

9

4

0

3

1 2 0 0 0 0 1 0 0 0 0 0 1 0 0 0

1 1

0 | 1 0 3

3 1

15 16

7

5

9

8

6

5

3

6 0 1

2

3

1

3

0 2

4

2 0 1 1 0 1 0 0 0 0 0

1 0

: 0 0 0 0 1 0

4 8 4 0 59 27 26 2 3 2 0 18 12 12 12 11 11 11 1 0

9

8

3

5

2 2 2 2 1 2

530 1

(18)

The laDvements most frequently occurring v/ere those

bet;7een the /dr Speed Indicator and the /artificial Horizon, a toteil of 92 movements during the five flights. Next in order of

magnitude were the movements from the Artificial Horizon to the idr Speed Indicator -ivith 74 occurrences,

Frcm Table V the link values beti/een the various

combinations of two instruments have been compiled and are given jji Table VI,

A link value beirv/een any two instruments is the total number of tiries that eye movements occurred betv/een the t\7o instruments. For exariiple in flight 1 the number of movements betv/een the /dr Speed Indicator and the Artificial Horizon v/as

25, and from the Artificial Horizon to the /dr Speed Indicator 17,

BO that the link vadue bet\7een these te/o instruavients is talcen as the sum of ihese movements, i,e, 42,

The relative link values are shoivn in Fig, 6 expressed as a percentage average for five flights, from v/hich it is seen that the instruments vdth the highest link values are the /dr Speed Indicator and the /irtificial Horizon with a percentage of

31.4.

(19)

0.7%

NOTE: VALUES LESS THAN

O-S'/o ARE NOT SHOWN H 00

0-6%

EYE MOVEMENT LINK VALUES BETWEEN AIRCRAFT INSTRUMENTS ON STANDARD

BEAM APPROACH

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T//BIE VI

LINK V/iLUES BEmïEEN INSTRUMENTS

/iSI-HOR and HOR-/iSI

H O R - D / G and D / G - H O R

A l t - A S I and / ^ I - A l t 1 HOR-Alt and Alt-HOR

1 H O R - R / C and E / C - H O R

j R / C - A S I and /iSI-R/C D / G - R / C and V C - D / G A S I - D / G and D / G - / \ S I

D/G-Alt and Alt-D/G R/C-Alt and A l t - E / C ASI-ENG and ENG-/iSI

T / S - R / C and R / C - T / S

ENG-Alt and /dt-ENG

D / G - T / S and T / S - D / G

T / S - . U t and / d t - T / S

H O R - T / S and T / S - H O R

A S I - T / S and T / S - A S T .

D / G - E N G and E N G - D / G

ENG-HOR and HOR-ENG

E N G - E / C and ^C-ENG Number of

Fixations

FLIGHTS 1 k2 17 20 10

5

2 1

6

2 1 : 1 0 1 0 2 0 2 1 1 0 |l14 2

33

12

6

4

12 15

9

1 2

5

1 0 0 0 0 2 ! 0 0 0 1 103

3

31 16 11 14 6

°

4

6

5

3

0 1 0 1 0 0 0 1 1 0 100 4 30 16 16 10 12 1

3

7

1 0 1 0 1 1 1 0 0 0 0 0 100

5

30 26 13

7

8

5

3

10 2 1 1 1 0 0 0 1 0 0 0

113 Total of

5 Flights

166

87

66

45

43

23 22 23 20 11

4

2

3 ! 2

3

2

3

2 2 1

530 Percent-age of

Total

31.4 16,4

12,4

8,5

8,1

4.3

4.1

4.3

3.8

2 , 0 0 , 7 0 . 4 0 , 6 0 . 4 0 . 6

! 0 . 4

0 , 6 0 . 4 0 . 4 0 , 2

100,0

/4. •.•

(21)

20

-4. Suggested Procedure for Future Investigations

The results of this investigation vrere obtained for the last tvro miles of each of the five approaches, v/hich, v/hile being the most critical section, represents only part of the

approach,

As data for establishing statistical relationships they must be considered incomplete and can only serve as a guide for subsequent experiments.

Extension of the observations over a longer flight

period would require some modifications of the procedure, Yvdth the type of camera used in this investigation, the maximum length of film which could be run through using the spring motor v/as 20 feet. This is equivalent to 800 frames and which if exposed at the rate of 10 per second vrould give a run of 80 seconds dur-ation,

As it is not possible to rev/ind during filming, it vrould be necessary to either cxrank the camera by hand, or attach an electric motor to the drive of the camera if longer filming time is required,

With this mcDdification the filming time could be increased to the capacity of the camera, in this case 100 feet, v/hich v/coild give a filiTong time of 6,6 minutes at a speed of

10 frames per second,

Unforseen circiimstances prevented the investigation being extended to the eye movements on an I,L,S, approach using

the Zero Reader and I,L,S. Cross Pointer independently,

(22)

AEPENDIX I

METHODS OF MEi^SURING EYE MOVEMENTS

Various methods have been employed to measure eye movements, a brief summary of Y/hic3h is appended,

(i) Direct visual observation of the eyeball

Javal (1879) made a study of eye movement by direct observation, and in an attempt to reduce the distraction of the experiment, a mirror v/as placed in front of the subject so that the reflection of the eye movements could be recorded behind the subject,

(ii) Counting technicpies

Landolt (I89I) determined what he considered v/as the smallest angle through v/hich the eye could move voluntarily by viev/ing a reciorring pattern at various distances. The distance between the patterns was 13 mm, and he increased the distance of view until the number of patterns could only just be coimted, The angular separation betv/een the patterns v/as then found to be about five minutes of arc,

(iii) Photographic methods

Dodge and Cline (I901) using a falling plate, appear to be the first to make a photographic study of eye movements, Kar slake (1940) brought this method up to date for work on the attention value of advertisements and notices,

Judd, ï.!c/dldster and Steele (I905) attached to each cornea a flake of Chinese v/hite, and by means of a cine camera achieved considerable success. The subject's head was clamped at the back and sides and he v/as required to bite a rigid piece of wood in order to eliminate any head movements,

In addition, two small steel balls vrere attached to a spectable frame and vrom by the subject, so that v/hen the eyes v/ere photographed, the movement of the flake of Chinese white relative tolhe steel ball image v/as an indication of the eye movement, the steel balls being a head datum. It was claimed by this method that the maximum error did not exceed 7-g- minutes of arc, (Experiments on stea.dy fiscation showed that movements of the eyes of at least 30 minutes of arc took place,)

Dodge (1907) passed light from an A,C, operated arc

lamp througih a blue glass filter and a vertical slit onto the cornea of the eye, and the image formed by the reflected light

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22

-was then photographed through a horizontal slit on to a falling plate. Thus, a record of side to side movements of the corneal reflex was obtained, and since the arc was A,C, operated, the record v/as broken and gave a time scale also. Again it v/as necessary to clamp the subject's head to eliminate any movement,

Taylor (1937) designed the ophthalmograph which v/as made by the Amevxcsn Optical Ccanpany to meet the need for a conmiercial eye camera. This camera is usedfor research on the saccadic nature of the movements in reading and the fixation pauses but again it is necessary to clamp the subjectfe head.

securely,

(iv) Mechanical recording

Ohm (1914) used a lever attached to one end of the eyelid near the outer cornea, and as the eye moved the lever was raised or lowered and the movement recorded on a revolving drum,

Other vrorkers have placed capsules over the eyeball and any movement of the cornea under the capsule produced a change in air pressure ivhich v/as recorded and calibrated,

(v) Photo-electric recording

Rotations of the eye a^ small as one minute of arc were detected by the photoelectric method as described by Lord and Wright (1948). An ultra-violet beam of wave length 365OA was reflected onto the subject's eye in such a direction that it fell on the blind spot when the subject was viewing the fixation target, Y/ith the assistance of photo-electric cells, a single stage balanced D,C, amplifier, a cathode ray oscillograph and other items, the eye movements v/ere recorded v/ith the above accuracy. As on previous experiments, the

subject was obliged to bite a dental block to obviate head movements as far ats possible,

(vi) Recording of the corneal retinal potential difference Carmichael and Dearbome (1948) are the greatest exponents of this method v/hich measures the eye movements by means of the potential change that occ;urs around the eye»

Since changes in comeal-retinad potentials are closely prop-ortional to the sine of the angle of rotation of the eye it is possible, v/ith correct positioning of the electrodes and amplifying system, to record eye movements electrically,

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AEESNDIX I I S T A : M D A R D B E A Ï I A P P R O A C H

In the Standard Beam Approach the iïain Beacon transmits tv/o beam morse signals (,-) A, and (-,) N, which enable the pilot to determine on v/hich side of the beam approajch he is flying,

When the pilot is flying in the narrov/ section vdaere the two beams overlap he receives a continuous note,

There are tvro Markers, the Outer I/Iarker and Inner Marker situated at 10,000 feet and 750 feet respectively from

touc3hd£)wn,

The Outer Marker transmits signals at two dashes per second while the Inner Marker transmits dots at the rate of six per second,

The pilot passes the Outer Marker at 1,000 feet and then descends to I50 feet at 6OO feet per minute. This height is maintained lontil the Inner Marker is heard, by which time the runway should be visible and the aircraft is landed safely, If the runway is not visible at the Inner Marker the procedure is repeated,