Night Vision Goggle Training and Currency Requirements for the Fixed-Wing VFR Pilot

Night Vision Goggle Training and Currency
Requirements for the Fixed-Wing VFR Pilot
Manuel Gomez
Embry-Riddle Aeronautical University

ASCI 691 Graduate Capstone Course
Submitted to the Worldwide Campus
in Partial Fulfillment of the Requirements of the Degree of
Master of Aeronautical Science
March, 2013
Abstract
The current FAA mandated Night Vision Goggle (NVG) training and currency requirements will be evaluated to determine their suitability when applied to the fixed-wing VFR rated pilot. A comprehensive examination of the capabilities and limitation of NVG technology will be presented and analyzed across the scope of aviation related topics. An evaluation of NVG related guidance by different countries will be accomplished. A survey will be conducted to determine the opinion of experienced NVG operators on the appropriateness of current NVG training and currency requirements when applied to VFR-only rated pilots. Conclusions will be formulated and recommendations on changes to the FAA requirements for NVG use by VFR-only rated pilots will be presented if warranted.

Keywords: federal aviation regulations, night vision goggle (NVG), VFR pilot

Night Vision Goggle Training and Currency
Requirements for the Fixed Wing VFR Pilot
Statement of the Project
This project examines the suitability of Night Vision Goggle (NVG) use by the fixed-wing VFR rated pilot and evaluates whether the FAA mandated training and currency requirements are adequate to assure safe operations by this subset of general aviation operators. For decades, the military has utilized NVGs to aid night flight operations. In recent years, advances in
NVG technology and an inject of NGV-experienced pilots to the civilian sector have prompted this group to request the FAA for approval to use NVGs outside of military. The first steps towards this end came from the FAA in the form of supplemental type certificates for the use of NVGs in Helicopter Emergency Medical Services (HEMS) in 1999. In 2009, the FAA amended Part 61 to include training and currency requirements for the use of NVGs by general aviation pilots. This guidance specifies the ground and flight training, pilot currency, and equipment requirements needed before a pilot can operate an aircraft with NVGs. At the onset, NVG technology with its apparent ability to “turn night into day” appears to provide the VFR pilot a number of significant benefits. By using NVGs, VFR pilots can identify terrain features for more efficient navigation. Pilots can also see other aircraft and their lights at greater distances, aiding in collision avoidance. NVGs can also help pilots to avoid controlled flight into terrain (CFIT) situations and inadvertent flight into instrument meteorological (IMC) conditions, both major causes for fatal accidents in aviation. However, personnel trained in NVG operations know that NVGs do not turn nigh into day. There are significant technical and physiological limitations when using NVGs. NVGs provide a monochromatic image, which quality can be significantly degraded by user adjustment error, illuminations levels (natural and artificial), weather, and the contrast and composition of the object been observed (Night vision goggle training: Civilian vs. military, 2009) . Furthermore, most NVGs only provide a limited 30° to 40° field of view requiring the user to utilize a scan pattern to properly assimilate the observed scene. Also, depth perception and the ability to accurately measure distance are degraded under NVGs (Parush, Gauthier, Arseneau, & Tang, 2011). With so many considerations to evaluate it is not surprising that it took the FAA many years to provide guidance on NVG use and training. However, in its attempt to cover too much ground the FAA may have come up short in its requirements for NVG use by the basically qualified VFR-only pilot. Program Outcomes

PO #1
Students will be able to apply the fundamentals of air transportation as part of a global, multimodal transportation system, including the technological,
social, environmental, and political aspects of the system to examine, compare, analyze and recommend conclusion. The multimodal aspect of the air transportation system will be addressed by conducting an investigation of NVG use by the military and civilian sector as a basis for comparison to the general aviation subset of the VFR pilot. The technological aspect will be addressed by examining NVGs as a whole system composed of the ocular unit(s), pilot /device interface, and the aircraft interior and exterior lighting. The social aspect will be analyzed by researching into the economic feasibility of NVG systems for the private pilot sector. The environmental aspect will be addressed by exploring the manner by which several environmental conditions such as cloud cover, moon illumination, rain, air quality and light pollution affect NVG operations. The global and political aspects will be discussed as the work compares the regulations established on NVG matters by the U.S., Canada, and Australia (FAA, 2011; Transport Canada, 2012; CASA, 2010). Conclusions will be presented based on this work. PO #2

The student will be able to identify and apply appropriate statistical analysis, to include techniques in data collection, review, critique, interpretation and inference in the aviation and aerospace industry.

A survey based on one conducted by the National EMS Pilots Association (2008) will be developed and administered via an online service to collect the opinion from subjects on several aspects of NGV operations, training, and currency requirements. The three targeted groups are military fixed-wing pilots, HEMS pilots, and general aviation pilots that have not flown with NVGs. These groups will provide perspectives from a pool of experienced and inexperience pilots in NVG operations. The survey will utilize Likert-Scale type questions. The data will be analyzed utilizing the Kruskal-Wallis test to determine if there is a statistically significance difference (p=.05) between these groups on their opinions and perceptions on the appropriateness of FAA training and currency regulations. The results will be interpreted and conclusions will be presented.

The limitations of this study are the short time allotted for data
collection and the lack of sampling control when an online service is utilized to administer the surveys (Leedy & Ormrod, 2010). PO #3

The student will be able across all subjects to use the fundamentals of human factors in all aspects of the aviation and aerospace industry, including unsafe acts, attitudes, errors, human behavior, and human limitations as they relate to the aviators adaption to the aviation environment to reach conclusions.

A considerable part of this project centers on the discussion and analysis of the human factors involved in NVG use. The human limitations present when using the device such as reduced field of view, depth perception, and poor distance estimation among others will be scrutinized and conclusions as to their impact on VFR flight operations will be stated. The topic of improper attitudes and expectations when using night vision technology will be examined and a cause-and-effect link from these to unsafe acts will be established. Finally, NVGs require pilots to adapt normal human behavior and develop new cross checks and visual scanning techniques to maximize their effectiveness and prevent dangerous errors. The goal of studying these factors it to reach conclusions on whether current training and currency FAA requirements are enough to assure safe NVG operations by VFR-only rated pilots. PO #4

The student will be able to develop and/or apply current aviation and industry related research methods, including problem identification, hypothesis formulation, and interpretation of findings to present as solutions in the investigation of an aviation / aerospace related topic The problem addressed by this work is stated as follows: The current FAA NVG training and currency requirements may be inadequate when applied to VFR-only rated pilots. Utilizing the data collection and analysis in the survey described in program outcome #2 above, the author will set out to answer the following research question: Is there a difference of opinion about the adequacy of current FAA NVG training and currency guidance between military fixed-wing pilots, HEMS operators, and pilots with no NVG experience? The null hypothesis that there is no statistically significant
difference in the opinion about the adequacy of current FAA NVG training and currency requirements between these groups. The research hypothesis is that there is a difference of opinion about the adequacy of current FAA NVG guidelines between the groups. Further analysis of the data will be conducted to determine if factors such as aviation rating, total flight hours, total NVG hours or total years of NGV use point to a particular point of view on the matter. The findings will be interpreted and solutions to the stated problem will be presented if warranted by the findings. PO #5 – Aeronautics

The student will investigate, compare, contrast, analyze and form conclusions to current aviation, aerospace, and industry related topics in aeronautics, including advanced aerodynamics, advanced aircraft performance, simulation systems, crew resource management, advanced meteorology, rotorcraft operations and advanced aircraft/spacecraft systems.

This project will evaluate NVGs as an advanced aircraft system which must be properly integrated into the aircraft for safe operations. Rotorcraft operations will be discussed as a baseline for civilian NVG use as currently HEMS operations provide the most developed example. The role of simulation systems for NVG operations formative training and maintenance of currency will be scrutinized. The effects of meteorology on NVG operations will be considered. Crew resource management will be addressed, comparisons between multi-crew and single pilot NVG operations will be conducted and conclusions will be presented. At this time it is assessed that the advance aerodynamics and advance aircraft performance aspects will not be significantly discussed in this project.

References
CASA (2010, March). Civil aviation order 82.6 instrument 2007. Retrieved March 8, 2013, from http://www.comlaw.gov.au/Details/F2012C00111 FAA (2011, August). Part 61.31. Retrieved March 8, 2013, from http://www.ecfr.gov Leedy, P. D., & Ormrod, J. E. (2010). Descriptive research. In Practical research (ninth ed., pp. 203-204). Upper Saddle River, NJ: Pearson Education. National EMS Pilots Association (2008). Helicopter emergency
medical services (HEMS) NVG utilization survey. Retrieved March 7, 2013, from http://www.nemspa.org/PubDocs/NEMSPA_NVG_Survey_0508.pdf Night vision goggle training: Civilian vs. military (2009, September). Rotor & Wing, (43), 9. Parush, A., Gauthier, M. S., Arseneau, L., & Tang, D. (2011). The human factors of night vision goggles: Perceptual, cognitive, and physical factors (2011 7:238). doi:10.1177/1557234X11410392 Transport Canada (2012, February). Advisory circular 603-001. Retrieved March 8, 2013, from http://www.tc.gc.ca/eng/civilaviation/opssvs/managementservices-referencecentre-acs-600-603-001-1467.htm

Night Vision Goggle Training and Currency
Requirements for the Fixed-Wing VFR Pilot
Manuel Gómez
Embry-Riddle Aeronautical University

ASCI 691 Graduate Capstone Course
Submitted to the Worldwide Campus
in Partial Fulfillment of the Requirements of the Degree of
Master of Aeronautical Science
May, 2013
Abstract
A study was conducted to determine if there is a significance difference in the opinions of NVG-trained vs. Non NVG-trained pilots in relation to training and currency requirements under FAR Part 61. A complementary literary review was conducted to evaluate the suitability of FAA mandated Night Vision Goggle (NVG) training and currency requirements when applied to fixed-wing VFR rated pilots. A comprehensive examination of the capabilities and limitation of NVG technology is presented and analyzed within the scope of aviation national and international regulations, human factors, economic impact, and training. A statistical analysis of the data collected in the study revealed that there is a significant difference of opinion among NVG-trained and Non-NVG trained populations in key areas concerning Part 61 regulation. Specifically, NVG-trained pilots appear to favor more conservative requirements such as making an instrument rating mandatory for NVG pilots and reducing NVG currency periods.

Keywords: federal aviation regulations, night vision goggle (NVG), VFR pilot

Table of Contents
Page Night Vision Goggle Training and
Currency Requirements for the Fixed-Wing VFR Pilot 6
Background of the Problem6
Statement of the Problem7
Significance of the Problem7
Assumptions7
Limitations8
Definition of Terms8
Acronyms8
Aviation NVG Development9
NVG Basic Theory of Operation10
NVG Physical Configuration11
Monocular NVGs11
Biocular NVGs11
Binocular NVGs12
Panoramic NVGs12
Helmet Mount12
Aircraft Windscreen13
Aircraft Lighting14
NVG Alignment and Focusing15
Measuring NVG Image Quality18
Resolution18
Contrast18
Visual noise18
Environmental Factors Affecting NVG Operations18
Weather18
Clouds18
Fog and rain19
Snow19
Landscape composition19
External light levels19
Human Factors of NVG Operations20
Visual acuity20
Physiology of human vision20
NVG vision21
Visual illusions22
False horizon illusions23
Confusion with ground illumination23
Autokinesis23
Height-depth perception23
Size estimation and size-distance illusion24
Task saturation24
Fixation24

Page

Historical Development of NVG Regulation24
Current FAA NVG Requirements28
Applicable regulations28
Ground training requirements28
Flight training requirements29
Currency requirements29
NVG Regulations in Other Countries30
Future Changes to FAA NVG Regulation31
NVG Training32
NVG training topics32
NVG alignment and focusing32
Flight planning, ORM, and CRM in NVG operations 33
Physiological factors and visual illusions35
Lighting effects and scene interpretation36
Computer based training (CBT)37
Economic Viability of NVG Operations for the Private
Pilot Sector37
Hypothesis Statement40
Method40
Participants41
Sampling Procedures42
Sample Size and Power43
Data Collection44
Research Design44
Results45
Statistics and Data Analysis45
Ancillary Analyses48
Discussion49
Conclusion and Recommendations50
References53
Appendix A: NVG Training Requirements Questionnaire58
Appendix B: Human Subject Protocol Application Form 64

List of Figures
Figure Page 1 NVG low light capability comparison by generation.10 2 Basic NVG operation concept.11

3 NVG Helmet Mount.13
4 MIL-L-85762A Type A & Type B lighting15
5 NVG binocular assembly adjustment and focusing components17

List of Tables
Table Page 1 Part 61 NVG Ground Training Cost Estimate39

2 NVG Training Study Participant Characterization41 3 Participant’s Current Area of Operations42
4 Mann Whitney Test Results on Assessment
of NVG Task Suitability by NVG Training Status46 5 Mann Whitney Test Results on Assessment
of Need for Instrument Flying Skills by NVG Training Status46
6 Mann Whitney Test Results on Assessment
of NVG Currency Periods by NVG Training Status47 7 Mann Whitney Test Results on Assessment
of NVG Proficiency Check Mode by NVG Training Status48

Night Vision Goggle Training and Currency
Requirements for the Fixed-Wing VFR Pilot
Background of the Problem
For decades, the military has utilized NVGs to aid night flight operations. In recent years advances in NVG technology and an inject of NGV-experienced pilots to the civilian sector have prompted this group to request the FAA for approval to use NVGs outside the military. The first steps towards this end came from the FAA in 1999 in the form of supplemental type certificates for the use of NVGs in Helicopter Emergency Medical Services (HEMS). In 2009 the FAA amended Part 61 to include training and currency requirements for the use of NVGs by general aviation pilots. This guidance specifies the ground and flight training, pilot currency, and equipment requirements required before a pilot can operate an aircraft with NVGs. At the onset, NVG technology with its apparent ability to “turn night into day” appears to provide the VFR pilot a number of significant benefits. With NVGs VFR pilots can more easily identify terrain features enhancing VFR navigation. Pilots can also detect other aircraft at greater distances, aiding in collision avoidance. NVGs can also help pilots avoid controlled flight into terrain (CFIT) situations and inadvertent flight into instrument meteorological (IMC) conditions, both major causes of fatal accidents. Nevertheless, personnel experienced in NVG operations know that NVGs do not turn nigh into day. There are significant technical and physiological limitations when using NVGs. NVGs provide a monochromatic image, which quality can be significantly degraded by user adjustment error, available illuminations levels (natural and artificial), weather, and the contrast and composition of objects been observed (Night vision goggle training: Civilian vs. military, 2009). Furthermore, NVGs are limited to providing a 30° to 40° field of view requiring the user to utilize a scanning pattern to properly assimilate the scene been observed. Moreover, depth perception and the ability to accurately measure distances are significantly degraded under
NVGs (Parush, Gauthier, Arseneau, & Tang, 2011). With so many considerations to evaluate it is not surprising that it took the FAA many years to provide guidance on NVG use and training. Finally, in 2009 the FAA opened the door allowing civil use of NVGs to include VFR-only rated private pilots. However, in its attempt to cover too much ground the FAA may have come up short in its requirements for NVG use by the basically qualified VFR-only pilot. Statement of the Problem

This project examines the suitability of Night Vision Goggle (NVG) use by the fixed-wing VFR rated pilot and evaluates whether the FAA mandated training and currency requirements are adequate to assure safe operations by this subset of general aviation operators. Significance of the Problem

If current Part 61 requirements for NVG training and currency are truly too relaxed, then there is a possibility that legally-trained NVG pilots may not have the necessary skills to surmount challenging situations that could develop during NVG operations. This could result in a trend of aviation accidents in the future when NVG use by the VFR private pilot sector is more readily adopted. Assumptions

Although a comprehensive review of topics related to NVG operations is presented in this work, it is assumed that the reader possesses a basic understanding of aviation operations.

Limitations
The limitations for this study were the need to adopt convenience sampling procedures and the short time available for data collection. Definition of Terms
Aided flight – Any portion of a flight where NVGs are used to perceive the outside scene.
Currency – Currency refers to a prescribed number of maneuver and/or events that must be performed within a specific period of time to avoid the need for refresher training or a proficiency check.

Part 61 – Section of Tittle 14 regulations that deals with the certification
of pilots.
Part 91 – Section of Tittle 14 regulations that deals with general operations and flight rules.
Unaided flight – Portion of a flight where NVGs are not used and the pilot relies on normal vision to perceive the outside scene. Acronyms
ABC – Automatic Brilliance Control
ANVIS – Aviation Night Vision Imaging System
BSP – Bright Source Protection
FAA – Federal Aviation Administration
FAR – Federal Aviation Regulations
FOR – Field of Regard
FOV – Field of View
HEMS – Helicopter Emergency Medical Services
I2 – Image intensification
IPD – Interpupillary Distance
MCP – Microchannel Plate
MOPS – Minimum Operational Performance Standards
NVG – Night vision goggles
RTCA – Radio Technical Commission for Aeronautics
STC – Supplemental Type Certificate
Aviation NVG Development
Initial work on night image intensification (I2) was conducted during the 1950s. However, it was not until the early 1960s that the first generation I2 tubes were introduced. These first systems were too large to be head-mounted and were not compatible for aviation use. In the late 1960s and early 1970s the introduction of the microchannel plate miniaturized the NVG assembly sufficiently to allow for head-mounted aviation applications. In 1973 the Army introduced the Gen II AN/PVS-5. This system although functional had significant limitations in low-light-level environments and was incompatible with fielded cockpit lights. It was heavy and it utilized a facemask that generated visual obstructions. In 1976 the U.S. Army Night Vision and Electro-Optics Lab started the development of the aviator’s night vision imaging system (ANVIS); the first NVG designed for aviation requirements. During the 1980s the AN/AVS-6 model was introduced for use in helicopters. A parallel development to ANVIS was the definition of military
design standard MIL-L-85762 to establish the requirements for ANVIS-compatible aircraft and cockpit lighting. In the 1990s the generation III AN/AVS-9 was developed for fixed-wing aircraft. As shown in figure 1, generation III NVGs enjoy vastly improved performance in low light conditions. The AN/AVS-9 model included for the first time a green filter that allowed head-up-display information to pass thru the NVGs without gaining down (dimming) the unit. Also the new NVG layout moved the battery pack to the front, making the model compatible with fast moving aircraft which require pilots to rest their helmet on the seat headrest during ejection (Schmickley, 2001).

Figure 1. NVG low light capability comparison by generation. Generation I NVGs had limited low light capability. Improvements by Gen III NVGs greatly increased their ability to work in extremely dim conditions. Copied from “Integration of Night Vision Goggles in Civil Aircraft” [PowerPoint slides] by M. Laughlin M Intergration of night vision goggles in civil aircraftLaughlin, (n.d.), p. 7. Copyright (n.d) by Transport Canada.

NVG Basic Theory of Operation
NVGs gather ambient light and intensify it by a factor of 104 before projecting it unto the user’s eye. The NVG operation sequence is depicted in figure 2. First, light photons enter the device through the objective lens. The lens focuses the light energy onto a photocathode detector sensitive in the visible to near-infrared spectrum. Generation III night vision devices utilize a gallium arsenide detector. Photocathodes materials have the property of releasing electrons when excited by light. When light photons strike the photocathode the photoelectric effect emits a current of electrons. This current of electrons is channeled by a component called the microchannel plate (MCP). The MPC is a solid state amplifier about a quarter of an inch long that contains about a million microscopic tubes. Each of these tubes is in itself an electric amplifier. When an electron strikes the plated walls of the channel other electrons within the channel are released and continue hitting and releasing other electrons within the tube generating a cascade effect. The amplified electrons then hit a phosphor fluorescent screen which converts the electrons back into light photons
creating a visible image which is projected unto the tube’s eyepiece lens (Schmickley, 2001).

Figure 2. Basic NVG operation concept. Ambient light is collected by the objective lens and focused into a photocathode which releases electrons via the photoelectric effect. The electrons are amplified by the microchannel plate and finally hit a phosphor screen which converts the electrical energy back to visible light for the user to see. Copied from “Night Vision Devices” [PowerPoint slides] by M. Robison M 2010 Night vision devicesRobinson, 2010, p. 5. Copyright 2010 by Robson Forensics. NVG Physical Configuration

There are different physical configurations for different NVG systems. Each present advantages and disadvantages for their particular application. Monocular NVGs. Monocular systems have a single tube and can only be used by one eye at a time. They are light weight and allow the free eye to see the scene unobstructed. Monocular systems are not suitable for aviation applications. Biocular NVGs. Biocular systems also have a single I2 tube but the image is projected into two eye pieces. Because the user sees the same scene on both eyes these devices do not provide stereoscopic depth perception. Additionally, this system does not provide redundancy in case of tube failure. Biocular systems are not considered suitable for aviation. Binocular NVGs. Binocular systems are the predominant configuration for aviation applications and will be the NVG system primarily addressed in this work. This configuration has two individual tubes that project slightly different scenes to each eye. This results in improved depth perception, contrast detection, and a slight increase in the overall FOV of the device over biocular devices (Parush et al., 2011). This set up also improves image quality by allowing the brain to merge both images and partially cancel out or reduce the noise generated by scintillation (Velger, 1998). Moreover, each I2 tube in a Binocular system works independent of the other improving redundancy. The drawbacks of this configuration are the added weight of the second tube plus the added complexity in adjusting and focusing each tube. Panoramic NVGs. Panoramic NVGs provide a 100° horizontal by 40° vertical FOV. This is accomplished by adding an intensifier tube to either side of
the binocular configuration. The main benefit of this configuration is the expanded peripheral vision for the pilot. However, several shortcomings have been identified during development. Image clarity is not as sharp as with conventional NVGs due to the need to merge the overlapping sections of four images. Additionally, fitting and focusing are more difficult to perform, and the extra FOV may prevent operators to turn their head away sufficiently to avoid blooming light sources (Thorndycraft, 2003). Helmet Mount

To be useful, aviation NVGs need to be coupled to the user’s eyes so the focused image is always available to the pilot. Although NVG head straps are used in ground applications aviation NVGs are usually helmet mounted. As seen on figure 3 the NVGs assembly mounts to the front area of the helmet right above the pilot’s eyes. The bracket mount assembly allows the pilot to rotate and lock the NVGs up in a stowed up position. The location of the NVGs introduces additional weight that must be supported by the pilot’s neck. For non-ejection capable aircraft applications, the added frontal weight induced by the NVG assembly can be offset by locating the battery pack and counter weights on the back of the helmet. The use of counter weights have been demonstrated to minimize the metabolic stress of the musculoskeletal structure of the neck resulting in lessened neck strain (Harrison, Neary, Albert, Veillete, et al., 2007).

Figure 3. NVG Helmet Mount. The binocular assembly is locked into position in front of the pilot’s eyes. Notice the space between the pilot’s eyes and the diopter lenses. This eye relief is used by the pilot to look below the NVGs at the cockpit instruments. Also, notice the location of the battery pack on the back of the helmet to offset the NVG assembly’s weight. Copied from “Night Vision Devices” [PowerPoint slides] by M. Robison M 2010 Night vision devicesRobinson, 2010, p. 13. Copyright 2010 by Robson Forensics.

Aircraft Windscreen
Although technically not an integral part of NVGs, an aircraft’s windscreen must not be overlooked when evaluating NVGs as part of a system. Windscreens can pose several integration issues that could hinder or limit NVG performance. Conventional windscreens are designed primarily for the visible
spectrum of 400 to 700nm and may absorb light energy in the 700-900nm infrared region where NVGs are most sensitive. Additionally, as the viewing angle towards the lower forward part of the windscreen becomes steeper, the transmission coefficients for the windscreen may drop to 70% to 20% from optimal. This is an important consideration as this part of the windscreen is usually used during the landing phase. Moreover, windscreens may produce light aberrations that may significantly degrade image clarity (Task, 1992). Aircraft Lighting

Incompatible external and internal aircraft lighting can have a negative impact on NVG performance. The issue is that light generated by the aircraft, instrument panel, and avionics can be gathered and amplified by the NVG device overpowering the light from the external visual scene. NVGs utilize circuitry to implement a Bright Source Protection (BSP) feature which reduces voltage to the photocathode to prevent tube damage by bright light sources. Additionally, an automatic brilliance control (ABC) feature is used to maintain the image projected to the user at relatively constant brightness levels by adjusting the intensifier gain response. When the observed scene is relatively dark, NVGs automatically adjusts their luminance gain to increase the device’s light intensification. The opposite happens when the system detects high levels of light; the BSP and ABC functions reduce overall light intensification. Incompatible NVIS lights can reduce the NVG’s night vision enhancement capability by reducing its luminance gain which in turn reduces contrast sensitivity (Gibb & Reising, 1997). To mitigate this problem, the MIL-L-85762A standard was developed to define NVIS-compatible aircraft lighting. The requirements were categorized into types and classes to match specific NVIS configurations. Type I lighting components are defined as being compatible with direct view image NVIS. These are Gen III systems were I2 tubes display the image on a phosphor screen. ANVIS are direct view image devices. On the other hand, Type II components are compatible with projected image NVIS. These are Gen III systems which project the intensified image on a see-through medium which in turn reflects the image into the user’s light of sight. As seen in figure 4, NVG compatible lighting is divided into Class A & Class B. Class A lighting use a 625 nm minus-blue objective lens filter while Class B
incorporate a 665 nm minus-blue objective lens filter. Class B lighting allows red and yellow colors in cockpit displays but at a price. Class B lighting can reduce NVIS sensitivity 8 to 10% when compared to Class A lighting when operating in moonless conditions (Schmickley, 2001).

Figure 4. MIL-L-85762A Type A & Type B lighting. Type A lighting make use of the blue/green spectrum by applying a 625nm minus-blue filter. Type B lighting allows for red display cockpit lighting by utilizing a 665nm minus-blue filter. The 40nm spectrum loss of Type B can reduce overall NVG sensitivity by up to 10%. Adapted from “Night Vision Goggles” by D. L. Schmickley D L 2001 avionics handbookSchmickley, 2001, The Avionics Handbook, p. 8. Copyright 2001 CRC Press. NVG Alignment and Focusing

Proper adjustment of the NVGs is critical to maximize image quality and minimize physiological discomforts. Alignment and focusing is accomplished by the manipulation of a number of knobs and focusing rings as seen on figure 5. The procedure is typically done in a prepared room called a test lane which houses an NVG resolution chart. The room needs an area 30 to 50 feet long that can be darkened when required. Viewing distances of 20 and 30 feet are marked on the floor. A reflector light with a 7 ½ watt bulb and calibrated to 20-25 VAC is used as a dim source of illumination during focusing. First the user should ensure the tubes’ optics are clean as dirty optics can reduce NVG performance by 30%. Second, the interpupillary distance (IPD), the distance between the eyes, is adjusted to a known value for later refinement. This is done with IPD adjustment knobs located on each side of the NVG assembly which moves each tube to the left or right. Next, the diopter focus setting is set to an individual’s personal setting or if this is unknown it is set to zero as a starting point. The whole assembly is then moved all the way forward away from the eyes, the tilt adjustment is centered and the NVG mount is placed on the lower one third in the vertical axis. The binocular assembly is then mounted on the NVG mount. With the helmet and NVGs on, the lights are turned off in the test lane room and the NVGs are powered on. The vertical position of the binoculars is adjusted until the tubes are directly in front of the eyes. Then, the tilt is adjusted to line up the tubes with the visual axis. The next step is to
recheck the IPD. With the IPD properly set the images from each individual tube overlap and form a single image. This is a critical adjustment as it has been demonstrated that a 4 to 5 millimeter IPD misalignment can result in visual acuity of 20/100 and 20/200 respectively from an attainable 20/40; a significant degradation. Next, the assembly is moved back towards the eyes. This sets the eye relief. Eye relief should be as close to the eyes as possible but should allow for viewing the aircraft’s instrument panel without having to tilt the head up significantly to move the NVGs out of the line of sight to the instruments. Once proper alignment is achieved the tubes are focused to infinity. The procedure calls for each tube to be focused individually. This is done by covering one tube or closing one eye while the other tube is calibrated. While standing at the 20-foot line, the first tube is calibrated by first adjusting the outer objective focus ring until the best resolution of the patterns on the NVG chart is obtained. Then, the picture is fine-tuned by moving the inner diopter focus ring counter-clockwise until the picture starts to blur. At that point the diopter ring is moved back in the clockwise direction and stopped immediately when the picture becomes sharp. It is important to stop immediately at this point. It is possible to maintain a sharp picture while still moving the diopter ring clockwise. However, it is the eye’s muscles that are adjusting for the overcorrection and over time they will fatigue resulting in loss of visual acuity, depth perception, an possibly headaches. After one tube is done the process is repeated on the second tube and visual acuity is then check with both tubes. The focus setting on the objective and diopter rings as well as the IPD settings should be noted and rechecked once in the aircraft as it is possible for them to shift during handling and transport (Sampson, Simpson, & Green, 1994; Angel, 2001). It should be noted that the focusing procedure can also be accomplished on a portable electronic device such as the Hoffman ANV-20/20. However, due to its cost and availability it is more probable that civil pilots will use the test lane or a similar configuration for their focusing procedure.

Figure 5. NVG binocular assembly adjustment and focusing components. Copied from “Night Vision Devices” [PowerPoint slides] by M. Robison M 2010 Night vision devicesRobinson, 2010, p. 14.Copyright 2010 by Robson Forensics.

Measuring NVG Image Quality
NVG image quality is dependent on interrelated optical and electro-optical parameters that determine the human eye’s ability to detect details and differences in contrast and texture within a visual scene (Parush et al., 2011). Resolution. The higher a device’s resolution the more or smaller details can be displayed. In NVGs image resolution is determined by the number of tubes the device’s microchannel plate contains. Resolution is measured in number of dots per square area. Therefore, a higher number of dots within a given image area translates to higher resolution. Contrast. Contrast measures the difference in brightness between the light and dark areas of a scene. In NVGs contrast is limited by the luminance (how much light is reflected) of the brightest and dimmest elements been observed. Visual noise. NVG images suffer from scintillation, a random effect that produces “grains” on the image. As available light decreases the ABC function of the system increases the units gain to achieve better luminance levels. The cost is an increase in electronic noise which reduces resolution. Environmental Factors Affecting NVG Operations

Weather. Climatological conditions can affect the available illumination upon a scene and diminish NVG performance (Parush et al., 2011). Clouds. Depending on are coverage and density, clouds can filter or block light from reaching the ground. The result is dependent on the operations area. An overcast deck can block all illumination below clouds and render NVGs all but useless on remote areas with no artificial illumination. However, cloud ceilings don’t always negate NVG operations. Over populated areas with significant artificial illumination a low cloud deck can reflect the light back towards the ground and increase overall scene brightness. Fog and rain. Fog and rain can filter available light in a way similar to thin clouds. Although some light may still be available for NVG use, image quality is typically degraded. Snow. The high albedo of snow allows it to reflect too much light. In most cases the BSP feature reduces NVG sensitivity reducing overall image quality. In the worst case the excess light may overwhelm the BSP circuitry and can potentially damage the system (Sampson et al., 1994). Landscape composition. For NVG operations landscape
refers to the scene been observed. Because NVGs work primarily in the IR range of the visual spectrum it is the landscape contrast in that wavelength range that has the most impact on image quality. Therefore, a scene with good contrast in visible light may appear less visible under NVGs. Deserts, large bodies of water, and forested areas provide little contrast under NVGs. Urban areas and roads typically present good contrast levels because different materials have dissimilar IR reflectivity levels (Sampson et al., 1994). External light levels. It may appear counterintuitive but the presence of bright external light sources in the operating area can be problematic to NVG operations. Even when operating an aircraft with NVIS-compatible lighting, external bright light sources can over saturate the NVGs. If the bright scene covers most of the NVGs FOV the user can be flash-blinded in a fashion similar to turning a light on in a dark room after a person’s eye have adjusted to darkness (Howard, Riegler, & Martin, 2001). At the same time, the NVGs’ BSP and ABC functions detect the increased brightness and reduce the device’s sensitivity. Depending on the brightness and duration of the event this may result in a period of time (seconds to minutes) where the pilot loses his/hers night vision adaptation as well as the NVG enhancement capability. Also, during this time pilots may find it difficult to read dimly lighted cockpit instruments which could be needed as a backup to maintain situational awareness (Howard et al., 2001). In cases where the bright light is a small point within the NVG FOV, a halo effect may be noticeable. The halo effect produces an expanded circular area around the light of increased brightness. According to Reising, Martin, and Martin this can lead to a loss of contrast in the image and errors in size and distance estimation (as cited in Parush et al., 2011, p. 248). Human Factors of NVG Operations

Visual acuity. Visual acuity is the ability of the eye to detect a separation between two points and therefore make out the details of a scene. A typical way of measuring visual acuity is by utilizing a Snellen chart. The chart contains row of letters in decreasing sizes, with the lowest row employing a separation between letters of one arc minute from 20ft away which is assessed to be what a person with normal vision should perceive. The results are reported in the form of a ratio with 20/20 been the standard for nominal
vision. The first number signifies the person’s distance from the chart, typically 20 ft. The second number means that the person can read the chart as well a person with nominal vision could at that distance. Therefore as the second number of the ratio increases, visual acuity decreases. Physiology of human vision. During periods of darkness, humans use scotopic vision. Scotopic vision uses the eye’s rods which are not color nor detail sensitive but can make out shapes and perceive movement. Visual acuity drops to 20/200 or less and a night blind spot appears in the central field of view. During daytime, the eye uses photopic vision. Photopic vision uses the eye’s cones to focus on sharp details and detect color. Photopic vision is superior in depth perception than Scotopic vision. Mesopic vision occurs during dawn, dusk, or full moonlight nights. Mesopic vision is an intermediate state between photopic and scotopic vision. Vision is achieved by a combined use of cones and rods. Details and color perception are dependent on available light levels and cone sensitivity. NVG vision. NVG output brightness is deliberately calibrated to be in the mesopic vision range. This allows the user to have a faster adaptation to scotopic vision if transition to unaided night flying is required. A typical transition from photopic to scotopic vision takes on average 30 minutes, while a pilot under NVGs can adapt to scotopic vision in 3 to 5 minutes (Parush et al., 2011; Sampson et al., 1994). Because NVG vision works in the mesopic range some detail and color perception is retained and available to the pilot. Although acuity levels of 20/25 are possible in perfect conditions, the average NVG visual acuity with current systems is assessed to be 20/40 across the spectrum of illumination levels. Consequently, NVG vision is regarded as considerably better that unaided night vision which nominally measures 20/200 (Hatley, 2001). Another important aspect of NVG vision is that the picture presented to the pilot is monochromatic green. Green is used because the human eye can perceive more shades of green than any other color and can therefore provide the most contrast in a picture. On the down side, the monochromatic aspect of NVG vision can degrade a pilot’s ability to make out objects and has negatively impacts depth perception (Australian Transport Safety Bureau, 2005). Finally, NVG vision is limited to 40° in the vertical and the horizontal. This 40° represent the instantaneous FOV of the device and it is significantly less than the normally available 200° horizontal by
120° vertical FOV. However, only the central 3% of the eye parafoveal area can provide high-acuity vision with acuity dropping 50% outside of that area (Schmickley, 2001). This means that even when under NVGs the whole FOV is not being used for high-acuity vision. The real issue with the restricted NVG FOV is the loss of peripheral vision. Humans rely on peripheral vision to maintain spatial orientation which is critical in flight operations. According to Task (1992) the reduce NVG FOV diminishes the pilot’s spatial orientation ability. This can in turn result in spatial disorientation.

Visual illusions. The visual system provides 80% the information a pilot’s uses for orientation. Therefore, important consideration should be given to any issue that negatively impacts the visual system. Visual illusions while operating under NVGs can lead to spatial disorientation (SD), a condition where a pilot fails to correctly perceive the correct motion, attitude, or position of the aircraft. In the best case, SD results in a momentary loss of awareness. In the worst case SD can end up in total loss of aircraft control. There are 3 types of SD events. On a Type I event the pilot is disoriented but he does not recognize his situation. This is the most dangerous type of disorientation as the pilot does not know something is wrong and therefore is not able to take corrective action to rectify the situation. In a Type II event, the pilot recognizes that there is a problem and can try to salvage the situation. Finally, in a Type III SD event the disorientation is so overwhelming that inhibits the pilot from regaining the proper orientation necessary to recover the aircraft (E Company, 1-212th Aviation, 2009).

During a study of night vision devices vision illusions and sensory events, Crowley (1991), reported that most of these events happened in good weather and during low periods of illumination. It was also determined that the main contributing factors were inexperience, division of attention, and fatigue. The most common illusions were misjudgment of height above terrain and attitude. In this same study, it was determined that pilots had a higher incident rate of illusionary events early in their careers with the number of incidents decreasing as they gained more experience. However, the pilots also stated that they felt the need to fly frequently to avoid recurrence of
the sensory effects. The following are the main visual illusions associated with NVG operations.

False horizon illusion. This illusion occurs when the pilot confuses a slanted cloud formation with the horizon or the ground and uses it as the wings level reference (E Company, 1-212th Aviation, 2009). Confusion with ground illumination. This illusion results when the pilot confuses ground lights with the star field or vice versa. Unchecked, this illusion can result in an unusual attitude and loss of attitudinal reference as the pilot maneuvers the aircraft employing the wrong reference (E Company, 1-212th Aviation, 2009). Autokinesis. Autokinesis occurs after a person visually fixates on a dim light in low light conditions. After 6 to 12 seconds of staring, the brain perceives the light source to move in random directions by up to 20° off center although in actuality the light has not moved (E Company, 1-212th Aviation, 2009). Height-depth perception. This illusion is cause by the lack of visual references when flying in areas with no significant contrast or detail such as deserts, snow, and large bodies of water. The danger materializes when the pilot relying on sporadic or non-existent references misjudges the aircraft’s altitude and terrain clearance (E Company, 1-212th Aviation, 2009). Size estimation and size-distance illusion. It is typical for a person using NVGs to underestimate the size of objects been observed. This induced error in size estimation occurs because the combined limitations of NVG vision reduce or alter some of normal cues used to perceive depth (Zelevski, Meehan, & Hughes, 2001). Because object size is one of the cues used to determine and object’s distance, the spatial perception of the outside world and a pilot’s own ship position is degraded. The size-distance illusion occurs when a pilot misinterprets an unfamiliar object’s size to be the same as a familiar object. By trying to make the unfamiliar match the familiar, the pilot may misinterpret the actual distance of the object. If an object is perceived as larger than it actually is then it is assessed to be at a closer distance than it actually is. An object perceived as been smaller than it actually is will appear to be farther than it actually is (Crowley, 1991).

Task saturation. Task saturation occurs when a pilot must deal with multiple
tasks simultaneously, maybe unexpectedly. The added stress of the multi-task environment negatively affects the pilot to the point where it becomes difficult to accomplish otherwise relative simple tasks.

Fixation. Fixation occurs when a pilot becomes preoccupied with a single task at the expense of monitoring other potentially more important flight tasks. For NVG operations fixation can be detrimental because it can break downs the pilot’s cross check which could result in loss of spatial information. Historical Development of NVG regulation

As discussed, NVGs are a great tool with the potential to significantly increase the awareness of pilots. However, their limitations and risk must be fully understood to ensure safety. Hence, it is not surprising that it has taken the FAA well over a decade to establish regulations for the civil use of NVGs. Before 1999, civil operator use of NVGs in the National Airspace System (NAS) was limited to those involved in public-use operations. This aviation sector was able to bypass many of the aircraft operation, pilot certification, and aircraft type certification FAA regulations because they were operating within the public-use charter. Under the public use charter, which includes the military, aircraft operating for certain government operations do not require FAA certification (Winkel & Lorelei, 2001). Examples of civilian sectors that fall under this classification are law enforcement and firefighting.

In 1999 the FAA approved the first Supplemental Type Certificates (STC) which on a case-by-case basis allowed operators to modify aircraft interior lighting for NVG compatibility. At the same time the FAA amended operational specifications allowing some commercial helicopter emergency medical service (HEMS) operators to begin limited use of NVGs in flight (Salazar, Temme, & Antonio, 2003). As part of this effort an FAA memorandum designated NVG’s as an appliance and made it necessary for manufacturer’s to acquire FAA certification for their devices before they could be used under Part 135. These steps opened the door for NVG use by the commercial sector and as a result the FAA saw a marked increase on requests for NVG related certifications. The process soon probed to be too cumbersome,
time-consuming, and expensive for operators and the FAA. The process needed to be streamlined and the ideal solution was to incorporate NVG rules in the FAA’s standing body of regulations (Winkel & Lorelei, 2001).

In July 1999, the FAA requested the Radio Technical Commission for Aeronautics (RTCA) to look at the issue the civil-use of NVG. The RTCA, a private, not-for-profit organization, develops standards for aviation technical concepts by assembling committees composed of industry, operator, and regulator experts. Special Committee (SC)-196, convened for the first time in December 1999 with representatives from the Air Force, Army, and Navy;

FAA, U.S. Customs, Border Patrol, DOE;
aircraft manufacturers, NVG manufacturers, aircraft lighting OEMs; international representatives from Australia, Canada, the United Kingdom, and other European member nations; and a number of special interest groups among others (Winkel & Lorelei, 2001).

The representatives where organized into 5 working groups; operational concept, NVGs, NVIS lighting, continued airworthiness, and training. The efforts of SC-196 resulted in the publication and adoption the following documents: 1. DO-268, “Concept of Operations, Night Vision Imaging System for Civil Operators”. This document describes the concept of operations supporting the implementation of aviation NVIS technology into the NAS by civilian operators. It defines terminology, capabilities, limitations and operations for NVIS and discusses training and supporting agencies. The focus of the document is the safe and efficient implementation of NVIS during various phases of flight. DO-268 was issued on March 27, 2001 (RTCA, 2013). 2. DO-275, “Minimum Operational Performance Standards (MOPS) for Integrated Night Vision Imaging System Equipment”. This document contains MOPS for aviation NVIS used to supplement night VFR operations. The document defined the NVIS system components. It also provides performance and test procedures for night vision goggles and lighting. DO-275 includes a section on continued airworthiness containing guidance to ensure the integrated NVIS equipment installation continues to meet the minimum performance standards
once in operational use. DO-275 was issued on October 12, 2001 (RTCA, 2013). 3. DO-295, “Civil Operators’ Training Guidelines for Integrated Night Vision Imaging System Equipment”. This document presents training guidance generated from lessons learned by agencies having years of experience in the training and operational application of NVIS with the goal of mitigating NVG-operations related mishaps. DO-295 was issued on October19, 2004 (RTCA, 2013).

The efforts of SC-196 were paralleled in Europe by EUROCAE an equivalent organization to the RTCA. In fact many of the members of SC-196 were also members of EUROCAE Working Group-57 chartered to address the NVG issue. As the intent of these documents was to provide a foundation for the development and establishment of regulations, it was highly desirable to standardize the final products at the international level to avoid undue burden for manufacturers, operators, and regulators (Winkel & Lorelei, 2001). This desire for harmonization was sensible as it currently minimizes the need to meet different standards across the industry. But the effort required to coordinate the number of agencies involved resulted in years of delays for the integration of NVG guidance into FAA regulations.

The next step taken by the FAA was the publication of FAA order 8900.1. This order provided FAA guidance on how to implement the RTCA documents under Part 135 (FAA, 2008). Then in 2009 the FAA finally added NVG rules to FAR Parts 61 and 91. For the first time private pilots could use NVGs in flight.

Current FAA NVG Requirements
A key point in assessing current NVG requirements is that the FAA early on adopted the standing viewpoint that NVGs will not enable flight. From the FAA point of view NVGs are used by pilots to complement night VFR operations and therefore pilots must meet all standard requirements for VFR flight. This means that currently there is no situation where a flight could be performed with NVGs that could not be performed without them (Schmickley, 2001; FAA, 2008). NVGs are considered to be a tool that augments VFR flight and increase safety.

Applicable regulations. For the purpose of this work only the regulation applicable to private pilots will be discussed. The bodies of regulations applicable to private pilots desiring to fly with NVGs are: FAR 61.1 NVG Definitions

FAR 61.31(k) NVG Pilot Training Requirements
FAR 61.51(f) Logging of NVG Pilot Time
FAR 61.57(f) NVG Recent Pilot Experience Requirements
FAR 91.205 NVG Aircraft/Equipment Requirements
In order to fly with NVGs a private pilot must complete a ground and a flight training program. The instruction must come from an FAA NVG authorized instructor and the pilot must receive a logbook or training record endorsement certifying the completion of both the ground and flying training components. In order to obtain the flight training endorsement the pilot must demonstrate proficiency in the use of NVGs.

Ground training requirements. The FAA currently mandates the following topics be covered in NVG ground training under Part 61.k.1: FAA regulation on night vision goggle limitations and flight operations. Aeromedical factors including:

Night vision protection and eye adaptation.
Self-imposed stresses that affect night vision.
Lighting effect on night vision.
Cues to estimate distance and depth perception at night.
Visual illusions.
Normal, abnormal, and emergency operations of NVG equipment. NVG performance.
NVG operation flight planning.
Night terrain interpretation and factors affecting terrain interpretation.
Flight training requirements. For NVG flight training under Part 61.k.2, the FAA requires the following areas to be covered: Preflight and use of internal and external aircraft lighting systems for NVG operations. Proper piloting techniques when using NVGs during takeoff, climb, enroute, descent, and landing phases of flight. Normal, abnormal, and emergency flight operations using NVGs.

Currency requirements. Once trained for NVG operations, pilots must maintain NVG currency in order to keep flying with NVGs. The currency requirements stated in Part 61.k.2 are: Three takeoff, climbout, descent, approach and landing sequences (these are only needed if the pilot wants to use the NVGs during the takeoff and landing phase of flight). Three area departure and area arrival tasks.

Three tasks of transitioning from aided (NVGs on) to unaided (NVGs off) and back to aided flight. In order to act as pilot in command using NVGs pilots must fly the above requirements within the 4 calendar months of the month preceding the flight. In order to carry passengers while using NVGs, pilots must comply with the same requirements but in a shorter period; within 2 calendar months preceding the month of the flight. It is important to note the wording of the regulation as the distinction between calendar months and months is important. For example, if a pilot makes 2 NVG flights between 1 and 2 March in which all the currency requirements are met then the latest the pilot could perform an NVG flight as PIC without passengers would be 31 July. This means the maximum period of time between NVG flights can be as long as about 150 days when flying solo or as long as 90 days if carrying passengers. Pilots that fail to maintain the currency requirements must pass an NVG proficiency check in the category aircraft they fly or in a representative simulator or flight training device. NVG Regulations in Other Countries

A comparison of NVG related regulations between the U.S., and other countries that have adopted NVG regulations yield a number important similarities and differences. Although, Australia has not expanded the use of NVGs to private pilots, Canada has followed on the steps of the FAA (Civil Aviation Safety Authority, 2010; Transport Canada, 2012). There are evident signs of international cooperation. For example, all countries cite RTCA DO-275 as the source document for NVG MOPS. Additionally, the ground training topics required by all three countries’ regulations are very similar. Nonetheless, there are some notable differences as well.

The most obvious differences between the U.S. and Canada (the only other country found to allow NVG use by private pilots) are in their flight training requirements. For example, Transport Canada requires pilots to have 300 hours in aircraft category, 20 hours of night unaided flight, and either an instrument rating or 10 hours of dedicated instrument training before commencing NVG training. The FAA does not have any prior experience requirement under Part 61, with the exception of having a private pilot certificate. There are some differences in NVG currency as well. In order to maintain currency to fly solo, Transport Canada mandates a 120-day currency period while the FAA currency period can extend to approximately 150 days Additionally, if currency is lost, in addition to performing the required events to regain currency Transport Canada requires pilots to conduct a review of inadvertent IMC procedures (Transport Canada, 2012). Finally, Canadian regulation does require different equipment minimums for NVG operations. Transport Canada requires a radar altimeter like the FAA. But, the radar altimeter requirement can be waived if the aircraft has a GPS navigation system with a terrain database. Notably, Transport Canada also requires either a pilot steerable searchlight or aircraft flood light capable to illuminating the maneuvering area. Although, this rule seems to make sense for rotorcraft it is not totally clear in the text if fixed-wing aircraft must also meet this requirement. This brief comparison was made to highlight the fact that other countries with NVG regulations have adopted more demanding rules for NVG operations than the FAA. Future Changes to FAA NVG Regulations

There is no indication at this time that the FAA intends to make any changes to its NVG requirements for the general aviation sector. However, on October 2012 the FAA released a charter creating an Aviation Rulemaking Committee (ARC) with the intent to study the feasibility of requiring the use of NVGs by 14 C.F.R. part 135 air ambulance helicopter pilots (FAA, 2012). The committee was tasked to study the benefits, economic, and risk implications of such a requirement and make recommendations by February 14, 2013. At the time of this writing the committee’s recommendations had not been made public.

NVG Training
Both the military and the civilian sectors have established formal courses to teach NVG operations. The scope of each course is varied and tailored to the end-user. Because of the tactical aspect of military aviation, military training programs tend to include more flight hours than civilian programs. Yet, the topics and concepts taught have a large degree of commonality between the two groups. (Night vision goggle training, 2009). A good NVG training program must be designed to achieve several key goals. Users must be trained to a high degree of familiarity with the equipment specifications and operation. This give pilots a solid understanding of NVGs capabilities and limitations helping them avoid unrealistic expectations that could result in unsafe situations.

There are two issues with the FAA training requirements under Part 61. First, some of the listed requirements can be too general, making them open to interpretation. For example, Part 61 requires NVG flight training in abnormal and emergency flight operations, yet it is open to interpretation what this actually means. Does inadvertent flight into IMC qualify as an abnormal operation? Many will argue that it does, still some instructors could elect not to cover this skill since it is not a spelled out requirement. Second, the requirements under Part 61 are topic or maneuver based with no minimum training time requirements. Consequently, due to ambiguity, it is possible to have two pilots trained to different standards under Part 61.

NVG training topics. This section presents an overview of select NVG training topics and a discussion on the applicable methodologies of instruction. NVG alignment and focusing. With so many possibilities for degradation, starting out with the best possible image is important for NVG operations. As previously described the goggles’ alignment and focusing procedure can be involved for the uninitiated. This is a critical skill to master as a poorly focused instrument can significantly degrade image quality. This skill has also show to degrade over time. In a 1994 study, Devilbiss, Ercoline, and Antonio found that a group of experienced NVG users were only able to achieve visual acuities averaging 20/45 and 20/50 on their
initial attempts to focus their device. After the participants were given refresher NVG adjustment and focusing training the averages acuities improved to between 20/35 and 20/40.

Flight planning, ORM, and CRM in NVG operations. Operational Risk Management (ORM) and Cockpit Resource Management (CRM) are considered mandatory instructional topics and NVG operations are no different. The need for ORM and CRM is evident in certain operations such as HEMS were pilots and crew may be under NVGs while attempting to land on an unprepared landing zone. In this case, crews train with the goal of understanding each other’s responsibilities and limitations, and to establish efficient communication. For private pilots the need for ORM and CRM may not be completely evident and yet could be even more critical as private pilots often fly as the only aircraft operator without anyone in the cockpit to highlight issues or take over the controls if required.

Both ORM and CRM start on the ground during mission planning. After deciding on a destination a pilot most get a weather forecast which for night flying should also include the illumination level (full vs. new moon). Based on the forecast and illumination available, the pilot can make an assessment on how useful the NVGs will be for navigation which could be a determining factor in the route selected (on or off airways). For increased safety a conservative approach is essential. Statics show that inexperience is a main contributing factor on NVG accidents and incidents (Crowley, 1991). Inexperienced and pilots with low currency should check unrealistic expectations of what capabilities NVGs can provide and avoid putting themselves in difficult situations that may exceed their skill levels. An example here would be a pilot that decides to fly a night NVG VFR mission with the ceiling reported at 1500ft (the VFR limit) when she would not otherwise do so without NVGs. In this situation the pilot is counting on the NVGs to provide additional information to maintain terrain clearance or avoid weather but this is perhaps an unrealistic expectation. As discussed before, even in nights of high illumination, a cloud ceiling can significantly decrease the light available to the NVGs. The pilot may takeoff expecting adequate NVG performance and find something else entirely.
A disciplined approach to mission planning and careful consideration of factors affecting the flight are essential. The following items should receive special consideration during NVG flight planning: Weather

Illumination levels (natural and artificial)
Route of flight and terrain avoidance
Total and recent flight currency
Total and recent NVG currency
Expected performance of NVGs given the conditions
Alternate plan in case expected NVG performance is not met (land, change of route, elevation, etc.) Pilot fatigue
CRM is another component that requires consideration. The goal of CRM for solo pilots is to identify all tools available as an aid to accomplishing the flight. Pilots may be alone is the aircraft but they can still communicate with servicing agencies to gather weather updates or obtain flight following. Moreover, by carefully preplanning the flight, pilots can identify times where they can expect to be busy and take steps to prevent situations potentially leading to task saturation.

Physiological factors and visual illusions. The physiological factors and visual illusions are other mandatory topics in NVG training. The focus of addressing visual illusions is to increase the pilots’ awareness about the possibility of experiencing these and provide pilots with techniques on how to prevent or recover from their occurrence.

A stressed lesson learned is that under most conditions visual illusions can be avoided or minimized by performing an aggressive scan that covers the available Field of Regard (FOR) coupled with a fluid crosscheck of the aircraft’s instruments (E Company, 1-212th Aviation, 2009; Night vision goggle training, 2009; Bless, 2008). This scan pattern is probably the most important and difficult skill to learn when learning to fly with NVGs. To be clear, the scan itself is not difficult to perform, what is difficult for the pilot is to internalize the new habit pattern for the scan and avoid fixating on any one object for too much time. The FOR is defined as the viewing area available to the pilot by moving his head to the horizontal and
vertical axis extremes. While NVGs can only cover an instantaneous FOV of 40° the pilot can scan a FOR of up to about 220°. By constantly moving his head from side to side the pilot is able to create a mental picture of his surroundings which become the basis of his spatial orientation. However, the scan process is only complete when the pilot performs and aircraft instrument scan (Bless, 2008). Based on the instrument parameters the pilot may receive reinforcing information (what he sees outside matches the instruments) or conflicting information (his perception does not match aircraft parameters). When a pilot receives conflicting information he becomes aware that there is a spatial awareness problem and can take action to correct it. The approved solution in this type of situation is for the pilot to transition to instrument flight, establish safe flight parameters, and only then attempt to resume a visual scan. This previous point highlights an apparent shortfall in requirements under Part 61. Pilots are not required to have neither an instrument rating or additional instrument training (such as the 10 hours that Transport Canada requires) to complete NVG training, yet as demonstrated by a number of incidents (Crowley, 1991) instrument flight skills are evidently necessary when pilots experience visual illusions or disorientation.

Lighting effects and scene interpretation. Traditionally, demonstrations of the effects of lighting levels on scene interpretation have been accomplished on a terrain board. A terrain board is a miniaturized mockup of a landscape. Students then can don their NVGs and thru them see a realistic representation of scenes at different light levels as well as some examples of visual illusions (Bless, 2008; Joralmon, Dunham, & Price, 2008). This simulation although effective is not very practical for pilots training under Part 61. Terrain boards are not mobile, requiring the pilot to travel and gain access to a location that has one. Nevertheless, there have been several developments in simulation that present adequate alternatives for Part 61 NVG training. The U.S. Air Force for example, has developed with Night Reediness LLC a Virtual Terrain Board (VTB). The VTB display scenes on a screen utilizing a personal computer and a high-definition projector in a standard classroom setup. The system has the capability to display scenes for direct NVG viewing (NVG stimulate mode) or it can show the scenes as
viewed thru NVGs (NVG simulation mode). Although some issues with the demonstrations of light color, halo intensity levels, and NVG gain effects were noted, the VTB received good marks from instructors and is a viable training alternative to physical terrain boards (Joralmon et al., 2008). Computer based training (CBT). CBT training is a proven flexible method for the delivery of instructional content. Night Flight Concepts offers a CBT program called NVIO as an NVG training alternative. An overview of NVIO’s brochure shows that the program covers all ground training topics required under Part 61 (Night Flight Concepts, n.d.). The program also has modules that the lighting effects and illusions demonstrations typically covered on terrain boards. There a several benefits to this training approach. The content is deliverable thru the Internet assuring accessibility. Also, students can cover the material at their own pace and review concepts on demand. Finally, Night Flight Concepts states that the programs content is FAA approved, meaning the instruction is standardized and that the possible training ambiguities previously discussed should not materialize. Economic viability of NVG operations for the private pilot sector

The entry cost into NVG operations is significant and will probably be the main reason most private pilots will not be able to conduct NVG operations for the foreseeable future. Any private pilot considering using NVGs must evaluate whether the potential added benefits of NVG flight offset the cost of equipment, aircraft modifications, and training. For most pilots the answer is no. Clearly, the first piece of equipment that must be acquired is the NVG. A Gen III aviation NVG set like the ANVIS-9 M949 sells for $10,200. This cost does not include other necessary components such as a helmet or head strap, light filters, and mounts which can easily add another $2,000 or more (Own The Night, 2013). Another significant cost is the modification of an aircraft lighting system for NVG compatibility. In order to obtain a FAA certification for NVG use an aircraft must be modified to the Class B lighting standard. Class B is used to comply with current FAA regulations which require certain warnings be presented to the pilot in red (Kearby, 2011). The options for cockpit lighting modification range from the use of filters on the face of instruments that block unwanted light frequencies to a complete overhaul and replacement of all light sources. The
complete overhaul option is the most effective but it is also the most expensive. An internet search for providers of cockpit lighting modification services revealed that most existing certified modifications are for helicopters. This is understandable as helicopters services such as HEMS, law enforcement, and firefighting are areas of operations with established NVG use. As these are custom jobs in nature no estimate was obtained but even the installation of instrument face filters (cheapest option) is estimated at thousands of dollars.

The last piece of equipment required for NVG operations under FAA regulations is a radar altimeter. Radar altimeter costs vary by model and extent of integration with other avionics but a stand-alone unit can be purchased for around $6,000 (Pacific Coast Avionics, 2013).

Training cost is the last component that must be considered. Table 1 shows an estimated breakdown for an NVG ground training course under Part 61. The total estimated cost for the ground course is $975. It is estimated that the current requirements for flight training can be accomplish in an average of four hours. Estimating an aircraft rental cost of $200 wet plus instructor time at $50 per hour, the average NVG flight training cost is estimated at $1,000.

Table 1
Part 61 NVG Ground Training Cost Estimate
Class/Item
Duration (hours)
Costa ($)
NVG Regulations
0.5
25
Aeromedical Factors
2
100
Normal NVG equipment operations
2
100
Abnormal and emergency NVG operations
1
50
Night vision goggle performance
2
100
Night vision operation flight planning
2
100
Night vision scene/terrain interpretation
1.5
75
NVG training software/Materials

400
Total Ground training
11
975
Note: The FAA only mandates the topics to be covered, not the duration. aInstructor time calculated at $50.00 per hour.
These calculations bring the NVG initial entry cost to be $18,175 without adding aircraft lighting modifications. It is easy to see that at this time the most significant hurdle to the use of NVGs by the private pilot population is its cost. With current instrument rating cost being about $7,843 (TNG Aviation, 2013) it is more efficient and versatile for a pilot to obtain an instrument rating than to train for NVGs operations for most applications. To be cost effective the NVG capability needs to bring something more to the table than just an additional aid to navigation.

Hypothesis Statement
The next section concentrates on a study conducted as part of this research work. The original research design set out to determine if there a difference of opinion about the adequacy of current FAA NVG training and currency guidance between military fixed-wing pilots, HEMS operators, and
pilots with no NVG experience. The null hypothesis stated was that there is no statistically significant difference in the opinion about the adequacy of current FAA NVG training and currency requirements between these groups. The research hypothesis was that there is a difference of opinion about the adequacy of current FAA NVG guidelines between the groups.

After analyzing the number of surveys returned, it was determined that there were not enough responses from HEMS operators (n=4) to test the original hypothesis. The research design was adapted to test a new set of hypothesis. The new design would still test the FAA NVG regulation adequacy question but against two broader groups; NVG trained pilots and non NVG-trained pilots. The null hypothesis is that there is no statistically significant difference in the opinion about the adequacy of current FAA NVG training and currency requirements between experienced NVG pilots and non NVG-trained pilots. The research hypothesis is that there is a difference of opinion about the adequacy of current FAA NVG training guidelines between these groups. Method

The goal of the study conducted was to make an assessment on the adequacy of current FAA regulations governing NVG training and currency requirements for civilian private pilots. The assessment was based on the difference in opinions between NVG-trained pilots and non NVG-trained pilots with regards to specific aspects of pertinent rules. Participants

In order to participate in the study the participants were required to have a private pilot’s license as minimum qualification. Table 1 and 2 below break down the study participant’s characteristics. Table 2

NVG Training Study Participant Characterization

NVG Training Status
Descriptor
Trained (n = 56)
Not Trained (n = 22)
Age
M=38.09, SD=9.74
M=40.14, SD=12.41
NVG Flight Hoursa
M=215.14, SD=223.15
–
NVG Total Years
M=4.45, SD=3.57
–
Total Night Hours
M=2149.86, SD=2906.63
M=247.68, SD=346.11
Total Flight Hours
M=3141.48, SD=3477.69
M=2149.86, SD=2906.64
aOne participant did not provide this information.

Table 3
Participant’s Current Area of Operations
Area
NVG Trained
Non NVG Trained
Total by Area
Fixed Wing – Private pilot
3 (3.8%)
9 (11.6%)
12 (15.4%)
Fixed Wing – Commercial
3 (3.8%)
7 (9.0%)
10 (12.8%)
Fixed Wing – Military
29 (37.2%)
1 (1.3%)
30 (38.5%)
Fixed Wing – Othera
0 (0%)
0 (0%)
0 (0%)
Helicopter – Private pilot
1 (1.3%)
4 (5.1%)
5 (6.4%)
Helicopter – EMS
4 (5.1%)
0 (0%)
4 (5.1%)
Helicopter – Military
4 (5.1%)
0 (0%)
4 (5.1%)
Helicopter – Othera
12 (15.4%)
1 (1.3%)
13 (16.7%)
Total by NVG Trained Status
56 (71.80%)
22 (28.20%)
78 (100%)

aOn the survey this option appeared as “ – other (law enforcement, firefighting, etc.).”

Sampling Procedures
Due to time constraints and available methods for participant recruitment the researcher had little control over sampling. The researcher requested the participation of qualified candidates by posting messages in select aviation forums, e-mail communication to fixed-base operators, HEMS companies, and direct communication with known aviators. This unavoidably resulted in convenience sampling and must be taking into account when measuring the validity of the conclusions made in this work. Out of 105 attempted responses, 27 where disqualified because they did not contain any answers to
any of the opinion questions. The reason for so many failed attempts is unknown but based on feedback received the researcher speculates that some respondents may have had problems navigating the questionnaire in mobile phone applications while others simply became disinterested and abandoned the questionnaire. Sample Size and Power

For this study, the overall population was defined as civilian and military pilots in the United States with a rating of Private Pilot or higher. According to the FAA (2012b) there were 465,117 pilots meeting this criteria in the United States by the end of 2012. The U.S. Air Force (2012) reported a pilot force of 15,258. By adding these figures the pilot population was conservatively estimated at 480,300 pilots. It was not possible to find statistical data to determine the NVG-trained pilot population. The researcher very conservatively estimated the NVG-Trained pilot population to a minimum of 9,000 pilots. The researcher assumed that at least one third (approximately 5,000) of Air Force pilots are assigned to fighter or helicopters which are generally NVG-trained. Additionally, the researcher estimated that there are at least 2,500 Army and Navy helicopter pilots and a minimum of 1,500 civilian pilots that are NVG trained. These population values were used to calculate the study‘s statistical power. For a significance level of .05, the sample sizes obtained provided a low statistical power of .19. With a significance level of .10 the statistical power rose slightly to 25% (Pezzullo, 2009). As the increase in power was negligible, the researcher opted to maintain a significance level of .05 for the statistical tests in this study. Due to the low power of this study all results and conclusions must be carefully evaluated. To validate the results presented in this work, a new study with a higher number of participants should be performed. To achieve the normally accepted power of .80 with a significance level of .05; the study should have collected 2441 responses, 688 from NVG trained pilots and 1754 from non-NVG trained pilots (Pezzullo, 2009). Data Collection

The data collection instrument selected for this study was a 28-item questionnaire which is available for review in the appendix. The questionnaire was administered via an online service. Questions 1 thru 10
covered participant consent to participate in the study and descriptive information about each participant’s qualifications and experience level. Questions 8, 9, and 10 were not available to respondents that were not NVG trained. Questions 11 thru 28 consisted of Likert-type items, each addressing specifics aspects related to NVG training and currency. The respondents had the option to select a level of agreement to each statement ranging from strongly disagree to strongly agree. NVG experience participants were instructed to state their level of agreement with a statement base on their own experience with NVG operations. Non NVG-experience pilots were instructed to state their level of agreement based on their current perceptions on NVG operations. Research Design

The goals of the research design were twofold. First, the researcher’s aim was to determine if there is a significance difference in the opinions of the general population of pilots vs. that of NVG-trained pilots when it comes to FAA training and currency requirements under Part 61. Second, the researcher wanted to analyze if the general opinion of NVG-trained pilots favored more demanding training and currency requirements. The participants were divided into two groups based on their NVG training status; trained or non-trained. To facilitate further discussion from now on this work will use the trained, non- trained labels to identify each group respectively. Because the survey utilized Likert-type questions the data collected was ordinal in nature and required non-parametric methods of analysis. Each question was analyzed utilizing the Mann-Whitney U test to determine if there was a statistical difference in the level of agreement between trained and no-trained populations. Additionally, the mean score for level of agreement was calculated to determine towards what level of agreement each population leaned to. Results

Statistics and Data Analysis
In other to perform the statistical analysis each agreement level was assigned a number value as follows: 1=Strongly Disagree, 2=Moderately Disagree, 3= Slightly Disagree, 4= Neutral, 5=Slightly Agree, 6=Moderately Agree, 7=Strongly Agree. Because the data collected was ordinal in nature a non-parametric test was selected. The Mann-Whitney test (p