Human factors: Human Engineering for the Australian F/A-18 NVC Project 12th ASCSA Workshop Adelaide – 30th to the 31st August 2007 Author: Matthew Squair

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Outline

•  Background to the NVC project •  The Physics of NVG operations •  NVG limitations •  Lighting compatibility •  Human error and NVG •  Design concept •  Verifying the design •  Conclusions •  Questions

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Background to the F/A-18 NVC Project

•  Operational need –  Night vision imaging systems provide an ability to conduct air

operations at night –  Balkan, Iraq and Afghanistan have proved their value

•  Key safety challenge –  NVG use has also been correlated to greater occurrence

rates of Spatial Disorientation (SD) accidents in aviation

–  30% of USAF identified NVG related accidents had lighting incompatibility identified as a significant factor

•  A change to the Pilot Vehicle Interface (PVI) –  Significant changes to lighting and displays are required to

make them compatible with NVG

–  But, we still need to maintain existing performance

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The physics of NVG operations

•  NVGs operate in the visible light & lower end of the IR spectrum using reflected, not radiant energy

•  This overlaps with aircraft lighting & display spectra

•  An NVG filter minimises the effect of these sources

•  Specific colour zones for lighting compatibility

400 500 600 700 800 900 1000

20

0

40

60

80

100

VISIBLE INFRARED

WAVELENGTH (nanometres)

Sky ambientradiation

Generation III (Class B/C)NVIS response

Class B‘minus blue’filter line 665 nm

Human eyeresponse

RELATIVE R

ESPON

SE (%)

Display/HUD P43 phosphor

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The limitations of NVG

•  They do not turn night into day, they are limited

•  These limits act as perceptual PSF’s –  Reduces visual acuity & contrast sensitivity –  Limited FOV (40 degrees) –  Nil colour contrast –  Lighting halo effects –  Reduced stereopsis –  Inability to detect light fog or rain

•  Lighting (and transparencies) can further degrade NVG

–  Sometimes subtly

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Lighting & transparency incompatibility

•  Incompatibilities –  Haloing –  Veiling glare –  Reflected light into FOV –  Transparency attenuation

•  NVG AGC reduction –  Reduces VA & CS –  Not perceptible to aircrew

•  Turn the display down? –  Makes it harder to read –  Doesn’t eliminate the

problem

•  Worse in low light levels

Effect of In-Compatible Lighting

HALOING

AUTO GAINING REDUCTION

CANOPY REFLECTION

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Human error and NVG

•  Visual perception effects –  Ambient vision reduced

–  Detection (VA) & form (CS) perception reduced by scintillating & monochrome scene

–  Depth perception monocular cues degraded

–  Colour effects & adaptation

–  Unusual scene contrasts increase perceptual workload

•  Physically fatiguing to use

•  PSF increase human error rates esp. in perception stage

•  Endsley’s SA model was used to categorise errors and causation

Situation awareness errorsPERCEPTION (LEVEL 1) SA ERRORS

Data not available due to:- No colour contrast- No visibility of light cloud, fog through NVG- Shadowing of terrain detail- Peripheral parallax motion cues

Data hard to discriminate due to:- Reduced visual acuity due to low light levels- Reduced NVG FOV & obscured displays- NVG/display/lighting in-compatibility- External lighting haloing- External scene effects (low moon etc)- Poor readability of displays (luminance, shadowing)- Canopy/windshield reflections in NVG FOV

Memory loss due to:- High scanning workload + operational task load

Data misperceived due to:- Halo size illusion- Distance estimation errors

Failure to monitor due to:- Breakdown of instrument scan- Attentional narrowing to NVG visual scene- Failure to maintain NVG scan for peripheral cues- High scanning workload + operational task load

COMPREHENSION (LEVEL 2) SA ERRORSIncomplete mental model due to:

- Unawareness of NVG limitationsIncorrect mental model due to:

- Visual illusions, spatial disorientationPROJECTION (LEVEL 3) SA ERRORS

Over-projection of current trends due to:- Unperceived spatial disorientation

Situation awareness errorsPERCEPTION (LEVEL 1) SA ERRORS

Data not available due to:- No colour contrast- No visibility of light cloud, fog through NVG- Shadowing of terrain detail- Peripheral parallax motion cues

Data hard to discriminate due to:- Reduced visual acuity due to low light levels- Reduced NVG FOV & obscured displays- NVG/display/lighting in-compatibility- External lighting haloing- External scene effects (low moon etc)- Poor readability of displays (luminance, shadowing)- Canopy/windshield reflections in NVG FOV

Memory loss due to:- High scanning workload + operational task load

Data misperceived due to:- Halo size illusion- Distance estimation errors

Failure to monitor due to:- Breakdown of instrument scan- Attentional narrowing to NVG visual scene- Failure to maintain NVG scan for peripheral cues- High scanning workload + operational task load

COMPREHENSION (LEVEL 2) SA ERRORSIncomplete mental model due to:

- Unawareness of NVG limitationsIncorrect mental model due to:

- Visual illusions, spatial disorientationPROJECTION (LEVEL 3) SA ERRORS

Over-projection of current trends due to:- Unperceived spatial disorientation

NVG error classes & causation (Endsley’s model of SA)

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The design concept

•  Operational concept –  Only during tactical phase of flight –  Unaffected day and night (non-NVG) ops –  No take-off/landings with NVG

•  Key performance attributes for the modification

–  Daylight & night-time readability –  Lighting balance of displays –  digital display and HUD effects –  NVIS compatibility of lighting –  Reflections

•  Cockpit had some natural advantages

•  Developed a design strategy for the integration

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Cockpit design

•  Issues we found –  FQI night time readability –  Legend inconsistencies –  Initial floodlight balance –  Daylight readability of legends –  Digital display effects –  Individual component

incompatibility –  Legend design

–  Follow on modifications •  Colour displays •  Solar coat transparencies

EMI FQI HSI

RIGHTDDI

LEFTDDI

SPN

--- --- ---- - -

LEFT

CO

NSO

LE

RIG

HT C

ON

SOLE

HUD

CHARTLIGHT

STANDBYINSTRUMENTS

NVG 400 FOV 1 STERADIAN (660)

NVG COMPATIBLE COMPONENT

NVG COMPATIBLE FLOODLIGHT

UNMODIFIED

MAIN INSTRUMENT PANEL (MIP)

LOCKSHOOT

HORIZONTALEYE LINE

LDG GEARFLAPS & STORE

PANEL

LH A&TWPANEL

RH A&TWPANEL

RADALT

CENTRE CONSOLE

CAUTIONPANEL

ARI

1 STERADIAN

400 NVGFOV

EMI FQI HSI

RIGHTDDI

LEFTDDI

SPN

SPN

--- --- ---- - ---- --- ---- - -

LEFT

CO

NSO

LE

RIG

HT C

ON

SOLE

HUD

CHARTLIGHT

STANDBYINSTRUMENTS

NVG 400 FOV 1 STERADIAN (660)

NVG COMPATIBLE COMPONENT

NVG COMPATIBLE FLOODLIGHT

UNMODIFIED

MAIN INSTRUMENT PANEL (MIP)

LOCKSHOOT

HORIZONTALEYE LINE

LDG GEARFLAPS & STORE

PANEL

LH A&TWPANEL

RH A&TWPANEL

RADALT

CENTRE CONSOLE

CAUTIONPANEL

ARI

1 STERADIAN

400 NVGFOV

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Verifying the design

•  Two tier program of component & aircraft level tests

•  Components qualified to MIL-L-85762A

•  At the aircraft level looked at system properties –  Reflections –  Readability –  Balance –  NVIS visual acuity

•  Use of aircrew to evaluate human factors of design –  Often no pass or fail but rather shades of grey –  Qualitative assessment –  Developed methodology based on Cooper Harper handling

scale method –  Aircrew evaluated ‘’1..5’’ then hidden weighting scheme used

to establish criticality –  Two test subjects (from same population)

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Aircraft ground test sequence

Results Summary •  T1 Pass/C* •  T2 Pass/C* •  T3 Pass/C** •  T4 through 6 Pass

•  All discrepancies evaluated by sponsor during tests

•  Final disposition agreed to by sponsor

•  Ferry crew feedback sought to validate T1 results

* Minor non-conformances, qualitative assessment scale used, similar to Cooper handling scale ** All chargeable non-conformance subsequently resolved.

TRR -TECH-

ACTIONS FROM TRR

TRR -OPS-

ACTIONS FROM TRR

T1 DAYLIGHT

READABILITY

T2 LIGHTING BALANCE

T3 NIGHT TIME

READABILITY

T4 CREW STATION REFLECTIONS

T5 NVG VISUAL

ACUITY

T6 NVIS

RADIANCE

POST TEST WASHUP

DRAFT TEST REPORT

DAYLIGHT

NIGHT/NVG

NIGHT

GROUND TEST SEQUENCE

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Visual acuity

•  Requires human evaluation –  Tri-bar chart illuminated at NRB limit –  Evaluate max. resolution (smallest bars)

•  Compare for lighting off then on cases –  Human error and bias issues

•  Chart shape is known (decision bias) •  Scintillation causes ‘fade in/fade out’ •  Human differences (upto 24%!)

•  A partial solution –  Two test subjects –  Qualitative comparison ARDU & USN data –  Illuminate at above NRB limit to reduce

scintillation

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5

Lighting ‘On’

Lighting ‘Off’

Incr

easi

ng

Opt

ical

fre

quen

cy

USAF 1950 TRI-BAR CHART FRAGMENT

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Conclusions

•  We achieved what we set out to do –  The cockpit is compatible with current NVG

–  No identified discrepancy was assessed as having a Safety of Flight implication

–  We retained the existing daylight and night time readability performance of the PVI

–  We identified how veiling glare from legacy digital displays could be managed

•  We actually improved performance in some areas:

–  Lighting balance and consistency –  Reflections –  Positive unsolicited comments from aircrew!

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Questions?