1. Civil Aviation Use of NVG
Presented by:
Transport Canada
Operational Standards
Division
Introduce ourselves.
The goal of the presentation is to discuss the integration of Night Vision in Civil Aircraft.
June 30, 2005

2. OUTLINE NVG Basic Concepts NVG Characteristics Human Factors
NVG/Aircraft Integration
Operational Considerations for Civil Certification
In order to integrate NV we need to understand the basic concepts of NV, the characteristics of NVG, and finally the factors that must be considered to properly integrate NV into a civil aircraft. I am not sure how much detailed knowledge each of you has about NVG and their characteristics, so some of this stuff may seem very basic to some of you. Please feel free to ask questions though, since I intend to cover the basics rather quickly.

3. Why Use NVG?
Human visual performance under night illumination levels very poor - 20/200 (full moon) or worse.
NVG - Enhanced visual performance - 20/30
Better spatial awareness
Improved situational awareness
We have all experienced that we can not perform flight tasks as well under dark conditions as we can during the day. NVG can help us perform VFR tasks better at night.

4. NVG Flight NVGs do NOT turn night into day!
Is NVG-aided flight considered to be enhanced night flight?
Or is it more appropriate to consider it degraded day flight?
NVG have been characterized as turning the night into day. That is not true. It depends on the approach taken by the operator. If operators try to do what they do in the day time at night when they use NVG then it is definitely much degraded day. NVG provide better spatial awareness than unaided night so they do enhance night ops, but within limits.

5. Basic Operating Concept
NVG - Used to view the outside world
Unaided Eye - Used to view the cockpit
There are a lot of misconceptions about how NVG are used. This is partly due to the evolution of the technology, and its use in the military. The NVG currently suitable for civil use are used to view the outside world, and the unaided eye is used to view the cockpit.

6. Anatomy of NVG
This is the basic anatomy of a NVG image intensifier tube. The incident light is filtered and focused by the objective lens and transmitted to the photocathode. The photocathode converts the light energy into an electron stream which is accelerated towards the microchannel plate. The microchannel plate acts as an amplifier, the output of which is directed on the phosphor screen, which converts the electron stream into light. The resulting image is then inverted and displayed on the eyepiece lens.

7. Objective Filters
Prevent certain wavelengths from entering image intensifier
Allows use of properly filtered lighting to illuminate cockpit for viewing underneath goggles
Class A: blocks below 625 nm (blue/green)
Class B: blocks below 665 nm (blue/green/reduced red)
Class C: incorporates notch filter to permit viewing of specific wavelength
TSO C164 requires that NVG be Class B or C. This is because it has been judged that the use of colour in a civil cockpit is necessary. There has not been any research that shows that Class A goggles have an operational advantage over Class B.
Class C is being used to permit aircrew to see fixed HUD symbology through the NVG

8. Spectral Response
The energy available from the night sky is represented by the gray shaded area. As you can see most of the energy is found in the IR region, with only a small portion available inside the visible region. The exact cut-off frequency in the visible spectrum is controlled by an objective lens cut-off filter.
NVG response has been tailored to amplify the light available in the near infrared and to drop off sharply in the red/orange region of the visible spectrum. This spectral response was chosen to allow the NVG to amplify a portion of the night sky illumination in which there is a lot of energy.

9. CLASS A/B/C
Class A - allows more visible light to be amplified by the NVG. The use of Class A means that the aircraft lighting must be designed not to allow those wavelengths to impinge on the NVG. This usually results in a monochrome cockpit. This is not an option for civilian use, since there are specific requirements for use of colour in the cockpit.
Class B - Allows less visible light to be amplified by the NVG. This allows for colour to be used in the cockpit, although standard aviation red is still not acceptable.
Class C - This is similar to Class B goggle with a notch filter designed to allow the fixed HUD light to be viewed through the NVG

10. Automatic Gain Control
Designed to maintain image brightness and protect tube from excessive light levels.
Automatic Brightness Control - Provides consistent output brightness by control of microchannel plate voltage.
Bright Source Protection - Protects the image intensifier tube by control of photocathode voltage.

11. Automatic Gain Control
NVG adjusts to ambient
conditions from overcast
starlight to dusk/dawn
Gain is constant, and noise increases
as illumination decreases
Gain (%)
Illumination (mlux) X
100
Constant brightness
region
The threshold illumination level for maximum gain depends on the goggles. For early Gen III it was approximately 1.5 mlux. The latest goggles are approximately 0.75 mlux.
The AGC/ABC results in phenomena that the pilot must learn to recognize and cope with.

12. Airborne Complex Light Scene
In this scene you can see the state of the art civil goggle. This is a complex lighting scene, with bright light sources and dark areas in the same area. Here we can see the effects of the AGC. The brightly lit areas provide usable visual information, the dark areas do not. The bright spot sources have halos around them, this is characteristic of NVG. The halo size is fixed, but its opacity is a function of the brightness ratio between the light source and its immediate surroundings.

13. NVG Performance Metrics
Tube Gain - Ratio of intensifier tube output brightness (in foot-lamberts) compared to illumination of the input (in foot-candles).
Gen III typical value: 25,000-60,000 fl/fc or fl/fl
System Gain - Ratio of output brightness to input brightness (both in foot-lamberts) for the complete system.
Gen III typical value: fl/fl

14. Signal (electrons produced by ambient light) Noise (stray electrons)
Signal to Noise Ratio
Measure of image intensifier performance
Defined as:
Stronger signal produced by:
More ambient light
More sensitive photocathode
SNR highly dependent on ambient light levels
Signal (electrons produced by ambient light)
Noise (stray electrons)
The SNR will be high at high ambient light levels and decreases as the light levels drop. SNR numbers quoted by manufacturers are based on standard test conditions.

15. Generation III - Improvements
Gen III I2 tubes (1995)
Photocathode sensitivity:
SNR of 16
1000 A/l
MCP channel diameter:
11 microns
Tube gain: 25,000 fl/fc
System gain: 2500 fl/fl
Resolution: 36 lp/mm
Gen III I2 tubes (2000)
Photocathode sensitivity:
SNR of 25
1,800 A/l
MCP channel diameter:
6 microns
Tube gain: 60,000 fl/fc
System gain: 6000 fl/fl
Resolution: 64 lp/mm
The resolution improvements in current equipment allow aircrew to see finer detail, such as wires.

16. Spectral Response - Gen II vs. Gen III
As mentioned in an earlier slide, the Gen III tubes are designed to work in the are where the most information is present. This results in greatly enhanced low light capability.

17. NVG Low Light Capability Comparison

18. Generation I, II and III Comparison

19. NVG HUD Display flight and navigation information
Eliminates need to look under the goggles for aircraft system and flight information
Increased safety
Enhanced situational awareness
NVG HUD can be provided in some installations. The cost of integrating a HUD is probably prohibitive in civil applications.

20. NVG HUD Image

21. Human Factors Visual Performance Fatigue Spatial Disorientation
Complacency

22. Visual Performance NVG FOV is 40 degrees
NVG partially obstruct view of cockpit
Visual Acuity is generally 20/30 at best
Decreases in low light
Decreases as contrast in scene decreases
Monochrome image

23. Vision Physiology Day vision – Photopic (Cones)
Night vision – Scotopic (Rods)
NVG Image – mesopic (mixture)
The NVG image is fairly bright, transition to lower light levels takes time.
Flight crews are not “dark adapted” while using NVGs
The newest versions of NVG have a output display luminance of approximately 4 fL. Physiological studies have shown that accommodation to a dimmer light level (flight instruments set dimly) can result in excessive (2 to 10 seconds) time delays especially in pilots over 40.

24. Spatial Disorientation
Visual Performance factors result in increased susceptibility to visual illusions
Black hole
Terrain Masking
Resolving object size/ Altitude estimation
Judging Closure rates with terrain/ aircraft
Scanning techniques can result in disorientation

25. Environmental Issues Summer Winter Backlit Terrain (Terrain masking)
Dust-ball (Loss of drift cues close to ground)
Falling Rain (IIMC)
Winter
Snow covered ground (whiteout)
Snowball (Loss of drift cues close to ground)
Falling snow (IIMC)

26. Environmental Issues Cultural Lighting
Bright light in FOV – NVG Gain decreases
Could make obstacles invisible
Halos mask obstacles
Difficulty picking obstacle lights out of background

27. Environmental Issues Remote Areas
NVG sees reflected energy – don’t work under all conditions
NVG operating at maximum gain - scintillation
Grainy image may mask precipitation (Inadvertent IMC)
Lack of resolution may make obstacles impossible to see, make accurately judging closure rates impossible
Image scintillation (video noise) indicates the NVG is at maximum gain. This could mask precipitation. Could result in terrain masking.

28. Fatigue NVG Weight and CG – physical fatigue
Visual performance factors – eye strain
Increased Cognitive workload – mental fatigue
Decreased FOV and obstructed view – physical fatigue
Circadian Rhythms
Crew scanning techniques need to be defined in company SOPs.
Cockpit scanning difficulties can result in two pilot minimum flight crew.

29. Complacency Complacency can be caused by excessive fatigue
Pilot may overestimate NVG performance
Decreased Visual Acuity – Don’t know what you can’t see
Flying with NVG has an almost video game feel – this could lead to unconsciously taking excessive risk

30. Human Factors - Solutions
Pilot Training
NVG Characteristics/Limitations
Visual Illusions
NVG Flying Skills – scanning, cross-check, image interpretation – use of a terrain board
Minimum instrument flying training; requirement for pilots to be instrument rated and current
NVG Compatible Aircraft
Training must be to proficiency, not just to a minimum hour level. Training must be tailored to the operators type and area of operation. An NVG compatible aircraft includes not only interior lighting but exterior lighting as well. Flashing strobes and the glow from non compatible position lights can have a marked effect on NVG performance and pilot fatigue.

31. NVIS Aircraft Integration
Cockpit Lighting
Aircraft Exterior Lighting
Windshield/Window Transparency
Physical Constraints
Handling Qualities - AFCS
These are the areas that need to be considered when integrating NVG into an aircraft. For helicopters there is not usually a problem with windshield or window transmission of infra-red light, but this needs to be considered. The cockpit may not be large enough to allow pilot head movements with NVG, or there may be aircraft structure which blocks a critical portion of the pilot’s FOV. Depending on what types of operation are contemplated, under which environmental conditions, and the aircraft’s handling qualities, there may be a requirement to have increased AFCS automation, ie. Rad Alt Height hold, Position hold…

32. Failure Criticalities
Severe-Major/Hazardous Failures
Display of hazardously misleading imagery
Inadvertent/Uncommanded illumination of NVG incompatible Light
Major Failures
Complete Loss of NVG image
Complete Loss of NVIS Lighting System
TSO C164, and RTCA DO 275
The complete loss of the NVG image is obviously hazardous, especially if it occurs at a critical point in the flight. The NVG currently being produced have a reliability of about 1 e-8 for the loss of both image intensification channels. The NVG incorporate a dual independent power pack, which warns the pilot of impending battery failure.
By design the NVG amplify light, they do not generate imagery. There are some image defects that could occur, but they do not generally resemble the real world, and as such can be easily identified by the pilot. With proper training pilots learn to cope with the visual illusions possible with NVG. So hazardously misleading imagery is not a problem by design.
The aircraft lighting system must be designed to make the illumination of a non-compatible light extremely remote. The most reliable way to do this is to remove all incompatible light sources from the aircraft. If incompatible lights are retained they must be controlled using very reliable switches, that minimize inadvertent actuation by the pilot.

33. NVG Compatible Lighting General Requirements
All sources of light in and on the aircraft must not degrade the operator’s view of the outside world through NVG.
Interior light sources and displays must allow the pilot to easily interpret flight, navigation and system information.
Exterior light sources must comply with CARs/FARs.
What makes an aircraft cockpit NVG compatible. Obviously, it must not degrade the NVG image. But at the same time it must allow the use of all the cockpit displays and controls while flying NVG-aided. The cockpit must also be usable for un-aided night flight and day flight.

34. Design/Certification Issues
Prevent light leaks.
Colour integrity/intensity to meet the certification basis, including external lights.
Daylight readability
Minimize cabin/cockpit reflections by using appropriate paint/curtains, etc.
Continue to meet the aircraft certification basis.
A properly designed NVG compatible cockpit allows the pilot to more easily interpret information than many OEM cockpits.

35. Design/Certification Issues
Aircraft Configuration
Maintain the qualification of all components installed or modified for NVG purposes.
STC Applicability
Test Conditions - Facilities
Test Equipment
Control of the aircraft configuration is a significant issue. All light emitting devices/equipment could render the aircraft unusable for NVG operations unless they are specifically designed to be compatible.
When components are modified for NVG compatibility the modifier must ensure that they continue to meet their environmental qualifications, performance specs etc.
Will it make sense to extend a NVG STC to a whole type, or multiple types. The interaction between other kits/STCs can render a NVG certified aircraft unusable for NVG. Examples are Large Spot/Flood Lights, mirrors, FLIR, etc. Configuration control is very important.
Test results are dependent on adequate test facilities, using equipment that will allow test conditions to be quantified and recorded. The Critical test condition requires the aircraft to be evaluated under “starlight” conditions. Obtaining these conditions requires careful planning, and preparation.

36. Aircraft Certification Test Program
Ground Test
Assess windshields
Assess Interior lighting
Assess Displays
Flight Test
Assess Exterior lighting
Confirm performance of cockpit displays/lighting

37. Incompatible Cockpit Light
Incompatible cockpit lighting has the capability to de-gain the goggles to point of being unusable. The effect is much like pointing a camcorder into the sun.

38. Poor Lighting Uniformity
Light uniformity has been implicated in numerous NVG accidents. Pilot workload has already increased from normal day flight by using NVG. If the cockpit information is difficult to see or interpret this may be the straw that breaks the camel's back.

39. Good Lighting Uniformity
In this cockpit the light levels have been made relatively uniform. The ratio of the brightest to darkest display is close to the spec value of 2 to 1.

40. Good Practice
The overhead panel in this aircraft was not illuminated in the original aircraft. The modifier/operator decided that it would reduce pilot workload and enhance safety to provide illumination.

41. Questions ?

42. Civil Approval of Aviator’s Night Vision Imaging Systems Programs utilizing Night Vision Goggles

43. Background
The development of ANVIS programs utilizing NVGs is being incorporated into, or considered by, organizations such as HEMS, police, and provincial forestry organizations.

44. OUTLINE
The following slides provide guidance for Canadian approval of commercial ANVIS programs.

45. Definitions ANVIS – Aviators Night Vision Imaging System
NVG – Night Vision Goggles
HEMS – Helicopter Emergency Medical Services

46. Approval to conduct ANVIS operations will be conducted in 2 parts:
Aircraft Certification Branch Approval
Operational Approval

47. Aircraft Certification Branch Approval
Approving the Supplement Type Certificate for installation of NVG compatible lighting in accordance with Airworthiness Notice AN BO53, and Aircraft Certification Policy Airworthiness Letter ACPL 29;
Flight test for ANVIS compatibility;
Development of the Rotorcraft Flight Manual Supplement
Only Night Vision Goggles conforming to TSO C164 may be used

48. Operational Approval
Evaluation of ANVIS ground and flight training programs;
Amendments to the COM including ANVIS Standard Operating Procedures (SOPs)
Monitoring of the training program;
Observing training and operational flights utilizing ANVIS

49. Additional Aircraft Equipment
A searchlight, steerable from either pilot seat, if night landings are to be conducted anywhere other than a lit, night certified aerodrome. This light need not be NVG compatible;
A Radar Altimeter;
NVG compatible exterior lighting

50. Inspector Training
It is recommended that Inspectors responsible for companies that wish to utilize this new technology receive training in ANVIS evaluation techniques as well as NVG operational training prior to assessing an air operator’s ANVIS program.

51. Company Training
Acceptable company training programs should consist of both ground and flight training programs.

52. Ground Training
Ground training should consist of classroom lectures, practical training and written exams with records of initial and recurrent training. The use of a terrain board model to simulate light levels and contrast is highly recommended. The following topics should be covered:

53. Ground Training Theory of Operation;
ANVIS Physiology and Human Factors;
Terrain Interpretation and Environmental Factors
SOPs and Emergency Procedures
Pre and post flight procedures
Flight profiles and weather considerations

54. Flight Training
The aim of ANVIS training should be to “train to proficiency”. At a minimum, this training should consist of 5 separate flights of at least 1-hour duration to establish basic NVG proficiency. Previous demonstrated NVG experience; such as recent operational military NVG experience may be considered an acceptable alternative.

55. Flight Training
Experience is considered current if it has occurred within the previous 24 months. During the last NVG training flight the candidate’s proficiency should be assessed in a manner similar to the pilot competency check and the candidates training file should be annotated accordingly. ANVIS flight training should include the following items:

56. Flight Training Pre-flight fitting, testing, and adjustment
Rehearsal of company ANVIS SOPs
Line / route / mission indoctrination as appropriate
Enroute procedures
Aircraft normal procedures including scanning techniques and cockpit drills while using NVGs;

57. Flight Training (cont’d)
Aircraft emergency procedures and NVG failure procedures
Post flight removal, safe storage,and maintenance considerations.

58. Flight Crew Requirements
Safe and successful ANVIS flying requires a high degree of instrument scanning proficiency.
Pilots conducting ANVIS operations must hold a current Instrument Rating

59. Currency
ANVIS flying is recognised as a skill that degrades with time and lack of currency. Company training programs must indicate minimum currency requirements to conduct ANVIS operations. The accepted interval to retain NVG currency is 90 days. After that time, a pilot may regain currency by conducting a training flight with a qualified NVG pilot prior to conducting passenger-carrying operations.

60. Flight Duty Time Limits
Conducting ANVIS operations, and the wearing of NVGs increases fatigue due to increased pilot workload and by the weight of the appliance itself. Flight and duty times should be reduced for pilots conducting NVG operations.
The current recommended maximum for ANVIS operations is 5 hours per night.

61. Company Operations Manual (COM) Amendments
COMs should be amended to contain, at a minimum, the following information:

62. COM (Cont’d)
Comprehensive SOPs for the conduct of ANVIS operations including normal and emergency procedures;
Pilot NVG currency requirements
Proficiency check requirements;
Pilot training requirements;
Company training pilot requirements;

63. COM (Cont’d) Crewmember training requirements and use of NVGs;
Recordkeeping requirements;
Minimum safe altitudes;
Weather considerations.

64. Current NVG Use
The Alberta Shock Trauma Air Rescue Society (STARS) is the first EMS operator in Canada to incorporate an ANVIS program into their operations.
They service areas around the cities of Calgary and Edmonton and some communities in British Columbia

65. Type of Operation
STARS uses their NVG program to reach communities in mountainous areas that would otherwise not be accessible due to the nighttime lateral obstacle clearance restrictions of Canadian regulations (CARs).

66. STARS
This is the first authority that has been granted to a Canadian operator providing alleviation from certain Regulations while using an ANVIS program, in this case, the MOCA for night routes with respect to lateral obstacle clearance limits.
Restrictions on the authority include; T/C approval of the ground and flight training program, pre-surveyed routes based on the use of TSO- C129 GPS units, increase in visibility on mountainous routes to 5 miles, minimum altitude enroute will be 1000 AGL.
NVFR Routes must be 1000agl min and 3 miles vis

67. NVG Reference Material
RTCA DO – CONOPS
RTCA DO – MOPS
RTCA DO – 295 – Training Guidelines
HBAT 02/04 - FAA Guidance
TSO C164 – Issued 30 September, 2004
FAA AC 27-1B/29-2C, MG-16
NVG Compatible Lighting Design Requirements – MIL-STD-3009
The RTCA charged a special committee with producing a document to define what is required for safe civil NVG operations. The deliverables of the SC 196 include the RTCA Document 275, which led to TSO C164 for the NVG, and could eventually lead to a TSO for NVG compatible lighting and displays. The FAA, JAA and TC drafted guidance material for NVG certification in aircraft, and it was published in the mega-AC.
The RTCA DO 275 was largely based on the military developed specifications and guidelines for NVG compatible lights/displays. The US military developed those Requirements and Guidelines over a long period of time with enormous resources. Many people will be tempted to say that civil NVG operations will not be as stringent as military NVG operations. The obvious extension to the argument is that the mil-spec is over-kill. We all have to keep in mind that the mil specs were developed to deal with the physical characteristics of the NVG, and the limitations of the humans using them in flight. They are independent of the type of operation that will be performed.

68. Summary of Key Safety Elements:
Thorough training of flight crews in both the strengths and weakness inherent in the system.
RADAR Altimeter.
Aircraft lighting fully NVG compatible.
Only TSO’d appliances used.
2 pilot multi engine environment with the capability to go IFR if required.
1000 foot minimum ceiling and 3 mile minimum visibility required for commercial night VFR (NVFR) ops.
5 mile visibility required for NVFR flight in mountainous areas

69. Questions ? Mike Laughlin Program Manager Rotorcraft & Aerial Work
Commercial & Business Aviation
Transport Canada
613) Telephone / Télélephone
(613) Fax / Télécopier
(613) Cell / Cellulaire