In The Dark Of The Night: Night Vision Goggles (NVG) Mishaps Lessons Learned
AUTHOR Major George H. Keating, USMC
CSC 1991
SUBJECT AREA - Operations
EXECUTIVE SUMMARY
TITLE: IN THE DARK OF THE NIGHT: NVG MISHAPS LESSONS
LEARNED
Beginning in the early 1970's, the proliferation of
sophisticated weapons' systems has necessitated changes in the
way the Corps will fight on the modern battlefield. In order
to survive and succeed in combat, Marine Aviation now depends
largely on its ability to fly and fight at low altitudes
utilizing night vision devices to "see in the dark."
Since 1978, with the advances made in night vision
technology and the development of an aggressive night
training program, the Corps has greatly improved its
warfighting capability. However, the improvements have not
come easy, nor without tragic losses in both human and
material assets due to NVG related aircraft mishaps.
The Corps had eleven NVG Class "A" flight mishaps
during calendar years 1984-1990. These mishaps resulted in
the loss of a squadron's worth of helicopters and the death
of 55 combat Marines. For some, this represented an
acceptable price to pay for the benefits derived in increased
combat potential. However, when 91 percent of the NVG
mishaps are caused by aircrew error, an attempt to ascertain
the more definitive causes of the mishaps should be of
interest to all Marine Corps aviation commanders and NVG
users. Asset conservation is as important in peacetime as it
is in combat. Thus, an analysis of helicopter NVG mishaps
can provide valuable lessons learned which may contribute to
the operational safety and overall combat readiness of the
Corps.
Two NVG mishaps were selected from the total to
illustrate some of the pitfalls associated with NVG flight
operations. They serve to depict the need for aircrews to
minimize the risks of NVG flight through proper self-assess-
ment in the overall context of the NVGs they use, and
the dynamic night environment in which they fly.
The lessons learned clearly indicate that we have been
our own worst enemy, often unable to distinguish between "can
do" and "hope for the best." The most significant lessons
learned from the Corps' eleven NVG Class "A" mishaps are as
follows: failure to consider environmental conditions and
their effects on NVG performance; failure to consider the
effects of low angle moons; failure to recognize the inherent
limitations of the NVGs; failure to properly plan and brief
for NVG missions; failure to coordinate as a crew; failure to
consider the effects of fatigue; failure to exercise good
judgment, failure to deconflict aircraft in congested
airspace; and failure to utilize required night aircraft
equipment.
IN THE DARK OF THE NIGHT:
NIGHT VISION GOGGLE (NVG) MISHAPS LESSONS LEARNED
OUTLINE
Thesis Statement. An analysis of helicopter NVG mishaps can
provide valuable lessons learned that can contribute to the
operational safety and overall combat readiness of the Marine
Corps.
I. Statistics
A. Calendar Years 1978-1983
B. Calendar Years 1984-1990
C. Pilot/Aircrew Error Factor
D. Low Angle Moon Factor
II. Selected Mishap
A. Case Study One
1. Environmental Data
2. Aircrew Fatigue Factor
3. NVG Equipment Factor
4. Navigation Factor
5. Crew Coordination Factor
6. Low Angle Moon and Terrain Shadowing Factors
B. Case Study Two
1. Environmental Data
2. Deconfliction Factor
3. Communication Factor
4. Low Angle Moon and NVG Factor
5. Crew Coordination Factor
III. Lessons Learned
A. Weather Considerations
B. Effects of Low Angle Moon
C. NVG Equipment Limitations
D. NVG Mission Planning and Briefing
E. Effects of Cumulative Fatigue
F. Crew Coordination Procedures
G. Overconfidence and Complacency
H. Light Level Planning Tools
I. Tactical Airspace Management (TASM)
J. Low Light Level Training
K. Required Aircraft Equipment
IN THE DARK OF THE NIGHT:
NIGHT VISION GOGGLE (NVG) MISHAPS LESSONS LEARNED
The heights by great men reached and kept
Were not attained by sudden flight,
But they, while their companions slept,
Were toiling upward in the night.
Henry Wadsworth Longfellow
Since the early 1970's, the development and
proliferation of sophisticated weapons systems has placed
greater emphasis on the U.S. Armed Forces to conduct night
operations to enhance their survivability and success in
combat. Consequently, the Marine Corps, in an effort to
maximize its combat potential, adopted from the U.S. Army in
1978, the use of night low level tactics with its reliance on
night vision goggles (NVGs) to "see in the dark." In the
past twelve years, with the aid of night vision technology
and an aggressive training program, Marine Aviation has
significantly improved its overall night fighting capability.
However, the improvements did not come easy, nor without some
blood, sweat, and tears.
During calendar years 1984-1990, the Marine Corps
recorded eleven Class "A" helicopter mishaps involving NVGs.
These mishaps have resulted in the destruction of thirteen
tactical helicopters and the death of 55 combat Marines. The
estimated cost of these mishaps was over $240 million
dollars. (16) Consequently, asset conservation through
mishap prevention remains a challenge for the Marine Corps.
Thus, an analysis of NVG mishaps can provide valuable lessons
learned which can contribute to the operational safety and
overall combat readiness of the Corps.
STATISTICS
Statistics are no substitute for good judgment.
Henry Clay
During calendar years 1978 to 1983, NVG training in
the Corps was in its infancy, and the reasonable man would
have assumed that the number of mishaps would have been high.
On the contrary, not one NVG training mishap occurred during
this period. This accident-free milestone was not a matter
of luck, or due to a particularly conscientious safety
program. It was more a function of a small number of elite
aviators, flying with NVGs in a very benign training program
under ideal environmental conditions.
However, beginning in 1984, the number of mishaps began
to rise due in part to the increased emphasis on NVG
training. All helicopter pilots were now required to train
with NVGs, and be able to complete at night, any mission that
could be flown in the day. Of the Corps' eleven NVG Class
"A" mishaps that occurred between 1984-1990, pilot/aircrew
error contributed to ten--a full 91 percent. In comparison,
only 45.7 percent of all non-NVG Class "A" mishaps were
caused by pilot/aircrew error for the same time period.
Although environmental factors are not causal to Naval
Aviation mishaps, it is interesting to note that 72 percent
of the NVG mishaps occurred when the angle of the moon was
less than 30 degrees above the horizon. These mishaps
accounted for 81.3 percent of the fatalities. Not one mishap
has yet to be attributed to the failure of the NVGs in use.
SELECTED MISHAPS
Few things are harder to put up with than a good example.
Mark Twain
The Corps' Class "A" NVG mishaps are summarized in Table
1 on page 4. Only two of these mishaps will be summarized in
greater detail. Both mishaps were selected based on their
numerous lessons learned which serve to illustrate what can
happen when the pitfalls of NVG flight are not understood and
approached with due caution. The following summaries will
clearly show that man has often been his own worst enemy,
unable to distinguish between "can do" and "hope for the
best."
Case Study One. David D. Hewitt once wrote, "To obtain
maximum attention, it is hard to beat a good big mistake."
His words are certainly applicable to this case study. This
particular mishap was the Corps' first NVG mishap, and it
received considerable media attention due to the high
number of fatalities--15 U.S. and 14 R.O.K. Marines.
The mishap occurred at 0400 when a CH-53 transport
TABLE 1
USMC NVG CLASS "A" MISHAP SUMMARIES
YEAR ACFT DEATHS TYPE NVGS MOON DATA CAUSE
1984 CH-53 29 PVS-5 FFP 53% 21 Degs Aircrew
Dash 3 flew into mountain in poor weather during troop
assault mission. 14 of 29 killed were South Korean Marines.
1985 AH-1T 1 PVS-5 FFP 0% 0 Degs Aircrew
Dash 3 impacted water while orbiting at rendezvous point.
NVG flight was not authorized.
1987 CH-46 3 PVS-5 MFP 97% 32 Degs Aircrew
Aircraft enroute to NVG training impacted mountain in poor
weather.
1987 CH-46 4 ANVIS-6 82% 29 Degs Aircrew
Lead aircraft impacted mountain while executing inadvertent
IMC procedures.
1987 UH-1N 1 ANVIS-6 100% --- Aircrew
Aircraft impacted water following T/R drive failure caused by
loose debris which flew out of cabin section.
1987 CH-46 1 ANVIS-6 0% 0 Degs Aircrew
Aircraft impacted flight deck on landing after engine failure
in flight. Aircrew launched form ship with known engine
discrepancy. NVGs were not authorized for flight.
1988 H46/UH1 10 PVS-5 MFP 99% 19 Degs Aircrew
command and Control Helicopter collided in midair with lead
helicopter of transport flight.
1989 UH-1N 5 ANVIS-6 0% 28 Degs Aircrew
Aircraft struck powerlines while conducting NVG navigation
route.
1989 AH-1W 0 ANVIS-6 97% 18 Degs Material
Aircraft rolled over in FARP due to crosstube failure.
1990 UH-1N 2 ANVIS-6 37% 17 Degs Aircrew
Aircraft impacted ground following improper pilot reaction to
T/R drive failure.
1990 2 UH-1N 8 ANVIS-6 83% 59 Degs Aircrew
Two aircraft collided in midair during formation training
flight.
helicopter impacted a mountain while participating in an
assault support mission of a combined exercise. The ambient
light level and visibility were reduced by cloud cover and
rain. Lunar illumination was projected to be 53 percent.
The moon's elevation at the time of the mishap was 21 degrees
above the horizon. This was nine degrees below the required
30 degree Marine Corps standard for the time. (15)
The troop assault mission involved eight CH-53
helicopters, divided into two divisions of three aircraft and
one section of two aircraft. The mishap aircraft was dash
three in the second division. The squadron had flown a day
rehearsal of the mission over the actual route of flight, but
canceled the night rehearsal due to adverse weather
conditions. Mission preparation time was extensive, yet
inefficiently managed which precluded crewmembers from
obtaining adequate crewrest. The mishap pilot (MP) and
mishap copilot (MCP) received only three and five hours of
sleep, respectively. (16)
The mishap aircraft did not have an NVG blue-light kit
installed which allows the use of interior instrument
lighting without adversely affecting NVG performance. To
compensate for this lack of NVG compatible lighting, the
mishap aircrew turned off all their interior lights and
superimposed blue filter paper over the secondary flood
lights. This unauthorized "quick-fix" procedure may have
permitted stray interior lights to degrade NVG performance,
given the existing low ambient light conditions.
Shortly after departing the airfield, the flight
experienced navigational problems on the NVGs due to poor
visibility caused by rain and cloud cover. Most pilots on
this mission reported the conditions to be the worst they had
experienced, and estimated that the forecast illumination of
53 percent was actually about 10 to 20 percent. This low
light level condition was beyond the experience level of the
squadron pilots who had trained in only high light levels
(39 to 98 percent illumination) under clear weather
conditions. Due to the reduction of available light for
proper NVG performance, the mishap flight was forced to
navigate on the route of flight by dead reckoning vice visual
terrain referencing. While enroute, the mishap division
became disoriented and lost sight of the flight. The mishap
division leader unsure of his position altered course and
altitude to effect a rendezvous with the flight in the
objective area.
Intraflight crew coordination and communication were
essentially non-existent. No radio calls were exchanged
concerning the deteriorating weather or navigational errors.
A sense of urgency to complete the mission was fostered by
higher authority in the chain of command. This compelled
mission aircrews to continue NVG flight when deteriorating
weather conditions dictated otherwise.
The mishap occurred as the second division attempted to
rejoin the lead division in mountainous terrain. The
extensive cloud cover and the combination of high terrain and
low moon angle created dark shadows that masked the terrain
to the immediate front of the mishap division. The mishap
aircraft was flying in step-down formation, 100 feet below
dash two with excessive lateral separation when it struck
the top of a mountain and tumbled to the valley below.
Neither the lead aircraft nor dash two saw the high terrain
which they narrowly missed.
Case Study Two. Ivern Ball said, "History repeats
itself because we weren't listening the first time." This
mishap was another of the Corps' spectacular NVG mishaps that
received national media attention and still echoes the words
of Ball. In this particular mishap, ten highly trained
aviation warriors were killed in a fiery midair collision.
The mishap occurred at 1943 and the weather was clear
and visibility unrestricted. The moon was 99 percent
illuminated, 19 degrees above the horizon, and 078 degrees in
azimuth. The mission was a simulated troop insert (no
passengers) into a desert landing zone (LZ). The mishap CH-
46 transport helicopter was the lead aircraft in the flight
of four. The other mishap aircraft was an UH-1N command and
control helicopter, separate from the flight of four
transports.
Due to the large number of aircraft involved in the
exercise, helicopter aircrews were briefed to remain 200 feet
and below for deconfliction while to and from the objective
area. However, no deconfliction plan was established or
briefed for traffic separation in the objective area.
At 1940, the mishap flight of transports landed at their
predetermined LZ. At 1942, the mishap flight leader received
the mission termination call from the command and control
helicopter, and instructed to report "lifting" from the LZ to
indicate his transition for departure. The mishap flight
leader acknowledged, but failed to give the preparatory
departure call. The mishap CH-46 lifted from the LZ and took
up a southwesterly heading toward its initial egress
checkpoint. About the same time, the mishap UH-1N, assuming
that the flight of transports was still on the deck, departed
from its observation point, and flew in a southeasterly
direction toward the same egress checkpoint of the CH-46
flight. The egress checkpoint now became an egress
chokepoint. Dash two and three of the transport flight
observed the converging flight path of the two mishap
aircraft but failed to communicate the danger. At 1943, the
two aircraft collided.
At the time of the mishap, any attempt to look east with
the NVGs was futile since the position of the low angle moon
(19 degrees) and its brilliance (99%) would have activated
the automatic brightness control (ABC) of the NVGs and shut
them down. This is the most probable reason that the UH-1N
aircrew did not see the CH-46 which would have been totally
obscured by the moon's position and brilliance. Why the
CH-46 aircrew did not see the well lit UH-1N will never be
known for sure, but it is postulated that an internal
breakdown in crew coordination occurred which degraded
lookout responsibilities.
LESSONS LEARNED
Learn from the mistakes of others or you'll not live long
enough to make them all yourself.
MGen. Daley
The following lessons learned were taken from the mishap
investigation reports of all eleven NVG Class "A" mishaps.
The lessons were derived from the author's analysis of each
mishap based on the evidence presented by the aircraft mishap
boards.
Weather and Visibility Restrictions. In one third
of the NVG mishaps, planners and operators failed to consider
weather and visibility restrictions which serve to reduce
ambient light levels. This reduction, in turn, reduces the
amount of light to the NVG and degrades the user's ability to
see features necessary for flight. Recognition of this
reduction is often difficult to determine because the
automatic gain (AGC) of the NVGs will attempt to provide a
constant image in spite of changing ambient light levels.
Therefore, aircrews must remain aware of the common cues to
reduction in light levels such as reduced resolution, halo
effect around a light source, and increased graininess.
Effects of Low Angle Moon In 63 percent of the
mishaps, aircrews failed to consider the effects of a low
angle moon. A low angle moon in mountainous terrain can
cause shadows which will affect obstacle avoidance. Flying
directly into a low angle moon amplifies the problems created
by shadows because the NVG's ABC feature will shut down the
goggles when a bright light source appears in its field of
view (FOV). Flying into a low angle moon on the NVGs is much
like driving a car into a low angle sun without the aid of
sunglasses or a visor. Thus, the NVGs react in much the same
manner as the human eye to a bright light source.
NVG Limitations. NVG mishaps have also indicated that
aircrews exceeded the capabilities of the NVGs. Although the
new ANVIS-6 NVGs are a significant improvement over the
older PVS-5 NVGs, the limitations of reduced visual acuity,
limited 40 degree FOV, reduced contrast, reduced depth
perception, and visual fatigue still exist. Therefore, the
user must develop a more active scan pattern, crosschecked by
cockpit instruments and information from his crew. Total
reliance on the NVG and fixating solely on an outside scan
has proven to be an unsatisfactory flight technique.
NVG Mission Planning and Briefing. In over one-half of
the mishaps, the saf e execution of the NVG mission was
jeopardized from the start due to inadequate planning and
briefing. NVG missions require a detailed game plan that
must be thoroughly covered to ensure mission success and
safety of flight. Applicable planning and briefing guides
must be consulted to ensure that no detail is overlooked.
Particular emphasis must be directed to environmental
conditions, ambient light levels, terrain analyses, map
studies, low altitude emergencies, inadvertent instrument
meteorological conditions (IMC), and crew coordination.
Mission planners and pilots must keep in mind the old
aviation axiom that "the mission usually goes as well as it
is planned and briefed."
Effects of Fatigue. In over half of the NVG mishaps,
fatigue was cited as a causal factor. Fatigue, especially
cumulative fatigue associated with circadian rhythm
disruptions and sleep deprivation, poses a genuine threat to
NVG flight safety. (14:3-10) The best means of combating
fatigue are as follows: manage one's off-duty time, maintain
proper nutrition and physical conditioning, enforce
crewday/crewrest requirements, gradually work into extended
night operations, avoid flight during physiological low
points (0300-0600 hours), and permit any crewman to cancel a
flight when fatigued. (14:3-11)
Crew Coordination. The lack of crew coordination was
cited in 82 percent of all NVG mishaps. Good crew
coordination involves flight leadership, two-way
communication, good judgment, and the ability to maintain
situational awareness. Aircrews must be aware of the
following indicators of loss of crew coordination: fixation,
confusion, violation of flight regulations, lack of flight
leadership, lack of lookout doctrine, absence of
communications, and failure to meet mission milestones.
(1:14)
Overconfidence and Complacency. It appears that as
aircrews become more proficient with NVG flight,
overconfidence and complacency have become problems to safe
mission execution. Overconfidence and complacency both tend
to lure the aircrew to over-fly their own capabilities as
well as those of the NVGs. (16) Aircrews must remember that
although NVGs enhance night flight, they have their limits.
Aeronautical Judgment. The Corps' NVG mishaps are full
of examples where aircrews failed to exercise good judgment
and flight leadership. Judgment and decision-making must
involve the assessment of risk. Risk management must be
continuous from brief to debrief. If risks are not properly
assessed, good judgments and decisions will not be made.
(2: 15)
Light Level Planning Tools. Illumination prediction,
using the U.S.M.C. computer generated Global Light Level
Calendar is an important planning tool. However, as useful
as this system is for planning, it does not provide real time
light level information. Variables such as weather and
visibility restrictions, moon angle, terrain shadowing, and
contrast differences in relation to aircraft heading and
altitude, can significantly alter the amount of light
available to the NVGs. When using the light level calendar,
planners and operators must keep in mind that it assumes
clear conditions. Therefore, aircrews must ultimately
determine go-no-go criterias based on actual weather
conditions, demands of the mission, and aircrew experience.
Furthermore, aircrews must keep in mind that the natural
illumination criteria established by Marine Corps policy is
based on the performance limitations of the NVG and the human
eye. Below this criteria, the NVGs are operating close to
its maximum sensitivity. Thus, image quality can be expected
to degrade with low light levels and the electronic noise (TV
snow) inherent to the goggles.
Tactical Airspace Management (TASM). Some form of
aircraft deconfliction is necessary whenever large numbers of
aircraft are in the operating area. Simply deconflicting
flight paths by altitude may not be enough. Planners may
need to establish TASM procedures which will deconflict
aircraft by time, space, altitude, and positive communication
when necessary. Additionally, consideration should be given
to separate aircraft operating with dissimilar night vision
devices which have different performance capabilities.
NVG Training. In several mishaps, aircrews did not
progressively train from high to low light levels.
Consequently, they were ill-prepared to deal with the
demanding conditions of the low light level environment.
Commanders must ensure that all assigned aircrews are
afforded the opportunity to master the basics and then train
in different conditions and operating areas.
Night Aircraft Equipment. In three mishaps, the
required aircraft equipment for NVG flight was incorrectly
set or not installed. The importance of having operable
radar altimeters, low altitude warning devices, automatic
flight control systems, IMC instrumentation, and NVG
compatible interior and exterior lighting cannot be
overemphasized. These systems should always be operable for
low altitude missions, particularly over featureless deserts
or large bodies of water where contrast is severely degraded.
For Marine Aviation, NVGs have truly enhanced combat
capability. NVGs have allowed us to operate clandestinely
with greater efficiency and effectiveness in a realm where
once there was only darkness. However, the lessons learned
from the NVG mishaps prove that aircrews repeatedly made
the same mistakes because they failed to consider the risks
of NVG flight. These risks can be minimized by analyzing NVG
mishaps for the valuable lessons learned which can contribute
to the operational safety and overall combat readiness of the
Corps. The underlying lesson learned from these mishaps is
that neither the environment nor the NVGs contributed to the
mishaps. Rather, the aircrews failed to fully assess their
own capabilities within the limits of the NVGs they used, and
the dynamic night environment in which they flew. Thus:
Darkness is a double edged sword, and
like the terrain, favors the one who best
understands and uses it, while hindering
the one who does not. (14:1-1)
Although the lessons learned were drawn exclusively from
helicopter NVG mishaps, some of the lessons may be applicable
to the Corps' fixed wing community which has recently
embarked on the AV-8B and F/A-18 Night Attack Program. It
would be beneficial for them to review these lessons to ensure
that they do not repeat the mistakes of the rotary wing
community.
Recent changes in Marine Corps policy have relaxed the
natural ambient light requirements for NVG operation. These
changes have widened the operating window for NVG flight to
permit more realistic training in low light level conditions
and with greater frequency. The new policy changes are
welcome and will further enhance the Corps' night fighting
capability. However, we must keep in mind that man with his
night imaging devices are still neophytes in a complex night
environment. Until night imaging devices are improved to the
performance standards of the human eye in daylight, NVG users
must recognize that nothing turns night into day, except the
sun." (15) Only a cautious approach, tempered by good
judgment, and command supervision will ensure that future NVG
training safely continues "in the dark of the night."
BIBLIOGRAPHY
1. Alkov, Robert A., Ph.D. "Loss of Situational Awareness."
Naval Safety Center Aeromedical Newsletter, 89-1
(Jan 89), 14-16.
2. Alkov, Robert A., Ph.D. "Aeronautical Decision Making."
Naval Safety Center Aeromedical Newsletter, 89-2
(Nay 89), 15-18.
3. Helicopter NVG Manual. Yuma, AZ: Marine Aviation and
Tactics Squadron One, 1 Sep 90.
4. HMN-361 AMB, Class A Flight Mishap Investigation Report,
01-84, CH-53D, 24 Mar 84.
5. HMM-261 AMB, Class A Flight Mishap Investigation Report,
01-85, AH-1J, 16 Sep 85.
6. HMM-764 AMB, Class A Flight Mishap Investigation Report,
01-87, CH-46E, 12 Feb 87.
7. HMM-164 AMB, Class A Flight Mishap Investigation Report,
01-87, CH-46E, 3 Sep 87.
8. HMM-263 AMB, Class A Plight Mishap Investigation Report,
01-87, UH-1N, 4 Oct 87.
9. HMM-164 AMB, Class A Flight Mishap Investigation Report,
02-87, CH-46E, 22 Nov 87.
10. HMLA-369 AMB, Class A Flight Mishap Investigation Report,
01-88, UH-1N/CH-46E, 25 Oct 88.
11. HNN-162 AMB, Class A Flight Mishap Investigation Report,
01-89, UH-1N, 3 May 89.
12. HMLA-369 AMB, Class A Flight Mishap Investigation Report,
01-89, AH-1W, 20 Jun 89.
13. HMLA-367 AMB, Class A Flight Mishap Investigation Report,
01-90, UH-1N, 27 Jul 90.
14. HMN-164 AMB, Class A Flight Mishap Investigation Report,
01-90, UH-1N, 8 Oct 90.
15. Mason, Richard, LCDR USN (MC), Aeromedical Safety
Officer, NAWTS-1. Personal interview about NVG
aeromedical issues. Quantico, VA., 28 Feb 91.
16. Tart, Wallace, MAJ USMC, Aviation Safety Officer, HQMC.
Personal interview about NVG mishaps. Washington,
D.C., 25 Jan 91.
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