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
Matthew Squair 2
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
Matthew Squair 3
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
0
2
3
4
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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