Gentex HGU-84/P Troubleshooting guide

OPERATION AND MAINTENANCE INSTRUCTIONS
WITH ILLUSTRATED PARTS LIST
HGU-84/P COMMERCIAL
HELMET ASSEMBLY
GENTEX CORPORATION
CARBONDALE, PA
JUNE 2001
© 2001 GENTEX Corporation

CONTENTS
CHAPTER 1: INTRODUCTION AND GENERAL INFORMATION
1-1 INTRODUCTION ....................................1-1
1-2 SCOPE ........................................1-1
1-3 SYSTEM DESCRIPTION ................................1-1
1-3.1 HELMET ASSEMBLY.............................1-1
1-3.2 HELMET SHELL ASSEMBLY ........................1-2
1-3.3 THERMOPLASTIC LINER ASSEMBLY (TPL®) ASSEMBLY ........1-2
1-3.4 EARCUP ASSEMBLIES ...........................1-3
1-3.5 INTEGRATED CHIN/NAPE ASSEMBLY ...................1-3
1-3.6 EEK-4 SINGLE VISOR ASSEMBLY .....................1-4
1-3.7 DUAL VISOR ASSEMBLY WITH QUICK DISCONNECT ..........1-4
1-3.8. LIGHTWEIGHT VISORS ...........................1-4
CHAPTER 2: PREPARATION FOR USE
2-1 SIZING ........................................2-1
2-2 HELMET FITTING ...................................2-2
2-3 FITTING OF TPL ASSEMBLY .............................2-5
2-4 FITTING OF OPTIONAL BAYONET RECEIVER ASSEMBLY ............2-9
2-5 INSTALLATION OF LIGHTWEIGHT VISORS ....................2-12
2-6 ANVIS MOUNT MODIFICATION (DUAL VISOR ASSEMBLY) ...........2-13
CHAPTER 3: MAINTENANCE
3-1 GENERAL........................................3-1
3-2 INSPECTION ......................................3-1
3-2.1 Preflight/Postflight Inspection .........................3-1
3-2.2 Calendar Inspection..............................3-1
3-2.3 Visual Inspection ...............................3-2
i

CONTENTS (Continued)
3-3 CLEANING .......................................3-3
3-4 SERVICING THE HELMET...............................3-4
3-4.1 INSPECTION UPON RECEIPT........................3-4
3-4.2 REPLACEMENT OF COMPONENTS ....................3-5
3-4.2.1 Replacement of TPL Cover or Layer Assembly.............3-6
3-4.2.2 Replacement of Earcup Assembly or Earphone ............3-7
3-4.2.3 Replacement of Earphone Holder ...................3-9
3-4.2.4 Replacement of Earseal ........................3-10
3-4.2.5 Replacement of Chin/Nape Strap Assembly .............3-11
3-4.2.6 Replacement of Chin Strap and Chin Pad...............3-13
3-4.2.7 Replacement of Nape Strap Clamp ..................3-14
3-4.2.8 Replacement of Boom Swivel Assembly ...............3-14
3-4.2.9 Replacement of Optional Bayonet Receiver Assembly ........3-16
3-4.2.10 Replacement of Energy-Absorbing Liner...............3-18
3-4.2.11 Replacement of Dual Visor Assembly ................3-20
3-4.2.12 Replacement of Single Visor Assembly ...............3-22
3-4.2.13 Replacement of Visor Lock Assembly ................3-24
3-4.2.14 Replacement of Single Visor Lens ..................3-25
3-4.2.15 Replacement of Lightweight Visor ..................3-26
3-4.2.16 Replacement of Visor Snap .....................3-27
CHAPTER 4: ILLUSTRATED PARTS BREAKDOWN
4-1 GENERAL .......................................4-1
4-2 COMPONENTS OF IPB ................................4-1
4-2.1 Figure and Index Number Column ......................4-1
4-2.2 Part Number Column .............................4-1
4-2.3 Description Column ..............................4-1
4-2.4 Units Per Assembly Column .........................4-1
4-2.5 Usable on Code Column ...........................4-1
ii

CHAPTER 1
INTRODUCTION AND GENERAL INFORMATION
1-1 INTRODUCTION
The HGU-84/P Commercial Helmet Assembly is designed to provide eye, ear, and head
protection when properly assembled and fitted to the aircrew member. It has a light-
weight helmet shell constructed of graphite, ballistic nylon, fiberglass, and epoxy resin.
The helmet assembly, available in four sizes (medium, large, X-large, and X-large
wide), is form-fitted. Its stability is enhanced by an integrated chin/nape strap assembly.
The helmet assembly also houses the headset communications and allows for the use
of clear or sunshade visor assemblies. The helmet is designed to permit the use of the
MBU-17/P oxygen mask if required.
1-2 SCOPE
This manual contains a description of the HGU-84/P Commercial Helmet Assembly
as well as the sizing, fitting, and maintenance instructions required to outfit aircrew
members successfully and to maintain the equipment properly.
1-3 SYSTEM
DESCRIPTION
1-3.1 HELMET ASSEMBLY
The aircraft helmet
assembly is available
with one of the
following visor
configurations: (1) a pair
of lightweight visors,
(2) a single visor
assembly, or
(3) a dual visor assembly
with a quick-disconnect
for night vision goggles.
These configurations
are shown in Figure
1-1. A chin/nape
strap assembly and a
thermoplastic liner
assembly are added
to the helmet shell
assembly for a better
fit and increased
stability.
1-1
Figure 1-1. HGU-84/P Commercial Helmet Assembly
HELMET WITH
SINGLE VISOR ASSEMBLY
HELMET WITH
DUAL VISOR ASSEMBLY
(QUICK DISCONNECT)
HELMET WITH LIGHTWEIGHT VISORS

1-3.2 HELMET SHELL
ASSEMBLY (Figure 1-2)
The helmet shell assembly
is intended to provide head
protection during in-flight
buffeting and emergencies
such as ejection, bailout,
or crash landings. It has a
polystyrene energy-absorbing
liner and a fitted leather
edgeroll installed. Earshell
pile fasteners on each side
of the helmet interior help
hold earcups in place. A
boom swivel on the left side
(as worn) of the helmet shell
allows for the mounting of a
boom/microphone assembly.
Optional bayonet receivers
(not shown) can be installed
to hold an oxygen mask.
1-3.3 THERMOPLASTIC
LINER (TPL®) ASSEMBLY
(Figure 1-3)
The TPL assembly, used in
conjunction with the energy-
absorbing liner installed in the
helmet shell assembly, pro-
vides helmet stability and
comfort. The TPL assembly
consists of preformed
plastic layers and a washable
cloth cover, which are held
together by double-sided tape.
If necessary, the TPL assem-
bly can be custom-fitted to the
aircrew member’s head. The
TPL assembly comes in three
sizes: medium, large, and
extra large.
1-2
HELMET SHELL
ENERGY-ABSORBING
LINER
EDGEROLL
EARSHELL PILE
FASTENER
BOOM
SWIVEL
Figure 1-2. Helmet Shell Assembly
Figure 1-3. TPL Assembly
TPL® is a registered trademark of GENTEX
Corporation.
DOUBLE-SIDED
TAPE
PLASTIC LAYERS
CLOTH COVER

1-3.4 EARCUP ASSEMBLIES
(Figure 1-4)
The earcup assemblies provide sound
attenuation and are compatible with
H-87B/U and H-143 earphones.
These assemblies are attached via
hook fasteners to the pile fasteners
installed inside the helmet shell. A
raised-ring earseal on each earcup
optimizes comfort and sound
attenuation. Earcup fitting pads
can be placed between earcup and
fitting shell if needed to optimize
the fit to the aircrew member’s
head. The pads can be cut to
any size or shape.
1-3.5 INTEGRATED CHIN/NAPE
ASSEMBLY (Figure 1-5)
The integrated chin/nape assembly is
adjusted via the chinstrap, which simul-
taneously adjusts the cross straps at the
nape strap area. This provides a snug,
comfortable fit with maximum helmet
stability. Clamp assemblies on the
nape straps allow adjustment of
the nape area without added strain
on the chin strap. The nylon
webbing nape straps feature
a leather-covered pad for comfort. A
spacer pad can be added behind the
nape pad for increased snugness.
The nylon webbing chin strap is
reinforced with aramid tape on the
inside. A snap tab on the right side
(as worn) of the chin strap allows for
fastening and unfastening without the
need for repeated lacing through the
D-rings on the left side (as worn).
The chin strap features a chinpad
with a pile fastener tab. A hook
fastener on the end of the chin strap
fastens to the pile tab to minimize
slippage.
1-3
CHINPAD
D-RING
CLAMPS
NAPE STRAP
SPACER PADS
NAPE PAD
CHINSTRAP
Figure 1-4. Earcup Assembly
Figure 1-5. Integrated Chin/Nape
Assembly
SPACER
PADS
EARCUP
GROMMET EARSEAL
EARPHONE
HOLDER

1-3.6 EEK-4 SINGLE VISOR
ASSEMBLY (Figure 1-6)
The EEK-4 is a single-lens helmet
visor assembly. When installed, the
EEK-4 provides face and eye
protection from impact, projectile
penetration, sun glare, dust,
windblast, and fire. Each assembly
comes with interchangeable clear
and neutral gray (sunshade) lenses.
The installed visor is operated by a
center lock mechanism.
1-3.7 DUAL VISOR ASSEMBLY
WITH QUICK DISCONNECT
(Figure 1-7)
The dual visor assembly has a clear
lens and a neutral gray (sunshade)
lens. The outer lens is operated
via a rotating lock. The inner lens
is operated via an actuating knob.
The center of the housing has a
quick disconnect for ANVIS night
vision goggles. Before you can
use the quick disconnect, you must
attach the ANVIS modification kit to
the ANVIS mount. This procedure
begins on Page 2-13.
1-3.8 LIGHTWEIGHT
VISORS (Figure 1-8)
The lightweight visors protect the
eyes. They are attached and
removed via snap fasteners.
Included are a clear visor and
a neutral gray (sunshade) visor,
both of which are trimmed to
accommodate the MBU-12/P
oxygen mask. Bump stops
attached to the helmet shell
hold the raised visor in place.
A lens cover can be added to
protect the raised visor.
1-4
LOCK MECHANISM
Figure 1-6. EEK-4 Single Visor Assembly
Figure 1-7. Dual Visor Assembly
With Quick Disconnect
Figure 1-8. Snap-On Visors
SNAP
FASTENER
LENS COVER
BUMP
STOP
ACTUATING KNOB
VISOR LENS
QUICK
DISCONNECT
TAB
LOCK
VISOR
HOUSING

CHAPTER 2
PREPARATION FOR USE
2-1 SIZING
To select the proper size helmet shell assembly
for the aircrew member, proceed as follows:
NOTE
Ideally, aircrew members will wear the
same size helmets as in previous
designations. However, if a good fit is
not possible, additional sizing procedures
may be required.
1. If helmets are available, aircrew member
should trial-fit to determine correct size to be
ordered. If helmets are not available, mea-
sure the circumference of the head with a
tape measure as shown in Figure 2-1. Refer
to Table 2-1 as a guide for sizing.
NOTE
Sizing instructions are provided only as general guidance. Because of the
wide variation in head shapes likely to be encountered, it is not possible to
present detailed guidance. The helmet is designed to provide lightweight
head protection and should fit close to the head. For this reason, aircrew
members should be fitted with the smallest helmet size that provides an
acceptable fit.
2. Once the correct size has been determined, requisition the helmet shell assembly
through normal supply channels.
Table 2.1. HELMET SHELL ASSEMBLY SIZING GUIDE
CIRCUMFERENCE (INCHES/MILLIMETERS) SHELL AND LINER SIZE REQUIRED
Less than 21-1/2 in. (546 mm.) Medium
21-1/2 to 22-1/2 in. (546 to 571 mm) Large
22-1/2 to 23-1/2 in. (571 to 596 mm) or more X-Large
23-1/2 in. (596 mm) or more X-Large Wide
2-1
Figure 2-1. Head Circumference
for Helmet Sizing

2-2. HELMET FITTING
1. Place the TPL in the helmet, ensuring that the holes in the TPL plastic layers are
positioned toward the front of the helmet.
NOTE
The TPL should seat down against, and align with, the front edge of
the energy-absorbing liner.
2. Have the aircrew member don the helmet as follows:
CAUTION
Spread the helmet just enough to allow ease of donning and doffing.
Excessive spreading may damage the helmet.
a. Grasp the helmet with thumbs hooked in the earcups, and spread the helmet
slightly.
b. Place the front edge of the helmet against the forehead.
c. Rotate the helmet toward the rear and down onto the head. Ensure that the
edgeroll is positioned just out of the aircrew member’s line of sight as the aircrew
member looks upward.
3. Check earcup position, ensuring that the earseals completely surround the ears.
4. Check earseal compression.
For optimum sound attenuation,
earseals should be compressed
to about half of their original
thickness. If necessary, adjust
compression by adding earcup
spacer pads.
NOTE
The earcup spacer pads
can be installed whole or
trimmed to any size or
shape needed for optimum
earseal compression.
Figure 2-2 shows several
examples.
2-2
INCREASE
OVERALL
PRESSURE
Figure 2-2. Earcup Spacer Pad Trims
BALANCE
TOP/BOTTOM
PRESSURE
BALANCE
FRONT/REAR
PRESSURE
BALANCE TOP/BOTTOM
AND FRONT/REAR
PRESSURES
BALANCE
CORNER
PRESSURE

5. Loosen the chinstrap clamp screws,
and slide the clamps (Figure 2-3)
down as far as possible on the
chinstrap. Adjust the nape straps for
a snug fit. Slide the clamps to hold
the adjusted straps in place, and
tighten the screws.
6. If you cannot achieve a snug fit by
adjusting the nape strap clamps,
install spacer pads (supplied with
the helmet) as needed between
the nape pad and the TPL.
7. If not already done, insert the
end of the chinstrap (Figure 2-4)
through the D-ring on the right side
(as worn) and fasten the snap.
8. Have the aircrew member
fasten the chinstrap as
follows (Figure 2-4):
a. Feed the end of the chinstrap
through the D-rings on the left
side of the helmet (as worn).
b. Split the D-rings, and loop the
end of the chinstrap through
the inner D-ring.
c. Tighten the chinstrap to the desired
tension. Thereafter, fasten and
unfasten the chinstrap via the
snap on the right side (as worn)
of the helmet.
9. Slide the chinpad (Figure 2-4)
to the center of the chinstrap.
Using needle and thread,
tack the chinpad in place to
prevent slippage.
2-3
Figure 2-3. Chinstrap Clamps
INNER
D-RING
END OF
CHINSTRAP CHINPAD
Figure 2-4. Fastening Chinstrap
CLAMP
CLAMP

WARNING
Ensure that the chinstrap is fastened at all times when the helmet is worn.
Failure to do so will result in a loss of helmet stability and may cause injury
or death.
10.Attach the end of the chinstrap to the chinpad by engaging the hook fastener on the
chinstrap to the pile fastener on the chinpad.
11.To check visor operation, raise and lower the visor or visors as follows (Figure 2-5):
Dual visor assembly: For the outer visor, rotate the visor lock counterclockwise
until the visor can be moved. Raise or lower the visor by sliding the lock up or down.
Secure the visor in the desired position by rotating the lock clockwise until it can
no longer be rotated. For the inner visor, unlock the visor by pushing the knob
outward. Raise or lower the visor by sliding the visor while holding the knob in the
outward position. Lock the visor in the desired position by releasing the knob.
Single visor assembly: Rotate the visor lock counterclockwise until the visor can be
moved. Raise or lower the visor by sliding the lock up or down. Secure the visor in
the desired position by rotating the lock clockwise until it can no longer be rotated.
Lightweight visor (with snaps): If the visor is not already installed, install it as speci-
fied in paragraph 2-5. Grasp the visor in the middle to raise or lower it. Adjust the
straps as needed by sliding the buckles.
12.After the aircrew member has worn the helmet for about 30 minutes, have him or her
evaluate the fit. If no pressure points exist and the helmet appears to fit properly,
have the aircrew member remove the helmet. Mark the helmet with the aircrew
member’s identity and store it properly. If the helmet does not fit properly, have the
aircrew member remove the helmet. Remove the TPL and follow the custom-fitting
procedure (Paragraph 2-3).
2-4
Figure 2-5. Visor Operation
DUAL VISOR ASSEMBLY SINGLE VISOR
ASSEMBLY LIGHTWEIGHT VISOR
OUTER VISOR INNER VISOR

2-3. FITTING OF TPL ASSEMBLY
MATERIALS REQUIRED
QUANTITY DESCRIPTION REFERENCE NUMBER
4Fastener tape, hook, pressure sensitive 85B7027
As required Tape, double coated, vinyl, approximately
1 x 2 inches (25 x 50 mm)
No. 419 (3M) or equivalent
To fit the TPL assembly in the helmet shell assembly, proceed as follows:
1. If four 1 x 2-inch (25 x 50-mm) pressure-sensitive hook fastener tabs are not present
on inside surface of energy-absorbing liner, installation is required. Install two tabs
vertically on the front of the energy-absorbing liner, and two tabs in the rear approxi-
mately 1-1/2 inches (38 mm) left and right from the center and approximately 1/4
inch (6.3 mm) from the bottom edges.
2. Ensure the TPL cover assembly
is secured to the TPL preformed
layer assembly with two approxi-
mately 1 x 2-inch (25 x 50-mm)
pieces of double-sided tape
(one on each side) as shown
in Figure 2-6.
3. Referring to Figure 2-7, install
the TPL into the helmet by
squeezing the TPL sides to-
gether to clear the earcups and
ensuring that large holes in the
TPL assembly (wide end) are
toward the front of the helmet
assembly.
4. Check the installed TPL to
ensure that the front edge of
the TPL is aligned with the front
edge of the energy-absorbing
liner inside the helmet, and
that the TPL assembly is
centered in the helmet.
2-5
Figure 2-6. Cover Assembly
Secured to Layer Assembly
Figure 2-7. Installing TPL

5. Have the aircrew member don the helmet with the installed TPL by placing the front
edgeroll on the forehead and rotating the helmet assembly rearward down onto the
head. For proper eye offset, have the aircrew member rotate the helmet assembly
forward to the position on forehead that will allow him or her to see the front edgeroll
of the helmet assembly while looking upward.
6. Readjust the earcup assembly inside the helmet assembly as necessary.
7. Adjust the chin/nape strap assembly, without disturbing the eye offset. The nape
strap pad should fit snugly against the nape area of the aircrew member’s head.
8. Ensure that the helmet assembly fits properly without hot spots or pressure points on
the aircrew member’s head. In extreme cases involving large sizes, removal of
TPL layers may be required for proper fitting. If so, proceed as follows:
a. Remove TPL assembly from helmet assembly.
WARNING
The helmet must always contain at least two plastic layers. Having
fewer than two layers will reduce helmet stability, which could obstruct
vision and reduce bump protection.
b. Remove layers from the TPL assembly one at a time, beginning with the layer
closest to the head. Check for proper fit after each plastic layer is removed. The
helmet must always contain at least two plastic layers.
9. After following the procedures listed above, if a safe, stable fit cannot be obtained,
then the TPL may be heat-softened and reshaped to aircrew member’s head. To
reshape the TPL, proceed as follows:
a. Set oven rack to the lowest position and heat oven to 200° ± 5°F (93.3°±2.8°C).
Place thermometer on the rack in a position where it may be observed
throughout the entire heating process.
b. Thoroughly instruct the aircrew member on the fitting procedures, emphasizing
those to be accomplished by the aircrew member.
c. Remove the TPL assembly from the helmet. Remove the cloth cover. Replace
the removed layers in the order in which they were removed. After the layers
have been reassembled, pass a heated soldering pencil through all five layers
at the original attachment point. Reinstall the cloth cover.
2-6

CAUTION
Do not attempt to heat the TPL in a toaster oven, as permanent
damage to the liner will result.
Do not attempt to heat the TPL in a microwave oven, or damage to the
oven may result.
Check oven temperature every two to three minutes to avoid overheat-
ing; otherwise, the plastic layers may melt. Do not leave the TPL unat-
tended while heating.
d. After 15 minutes, ensure the oven is stabilized at the pre-set temperature and
place the TPL onto the center of the oven rack with the fabric side down. Set
timing device for 10 minutes.
NOTE
Heating characteristics of ovens vary. This should be taken into
account during the TPL heating process. The time stated above is for
reference only and is not a rule.
e. For easy positioning of the heated liner into the helmet, place masking tape over
the rear hook fastener tapes.
WARNING
The TPL plastic layers will be hot when you remove the TPL from the
oven. Handle only the fabric-covered portion to avoid burning your
hands.
f. Remove the TPL from the oven, touching only the fabric-covered portion.
Squeeze in the sides of the TPL in order to clear the earcup assemblies, and
insert the heated liner into the helmet with the wide end toward the front of the
helmet.
2-7

NOTE
Steps g and h are to be performed by the aircrew member assisted by
the maintenance technician, and should be accomplished within 30
seconds of removal of the heated liner from the oven.
g. With the TPL centered in the helmet, have the aircrew member hook thumbs
over the edgeroll, spread helmet slightly, place front of helmet against brow, and
rotate the helmet rearward and down onto the head. The maintenance techni-
cian should hold the rear portion of the TPL tightly against the energy-absorbing
liner during donning to ensure the TPL does not bunch up in the rear.
h. Have the aircrew member interlock fingers on top of helmet and pull down until
ears are centered in the earcup assemblies and eye offset is correct. (See Step
5.) Maintain this pressure for 5 minutes.
i. Release downward pressure at the end of 5 minutes and check helmet fit. If
required, steps a through j may be repeated until a satisfactory fit is achieved.
j. Once a satisfactory fit is achieved, have the aircrew member doff the helmet.
Lift the rear portion of the TPL away from the energy-absorbing liner and remove
masking tape from the hook fastener tapes.
CAUTION
To avoid damage to the TPL plastic layers from excessive heat, do not
store helmet in closed cockpit or automobile. Temperature in these closed
areas can exceed 200°F (93.3°C) on an 85°F (30°C) day.
NOTE
The TPL cover can be laundered or dry-cleaned. Replacement of the
double-sided tape that attaches the TPL layer assembly to the TPL cover
assembly should be accomplished after each laundering.
2-8

2-4. FITTING OF OPTIONAL BAYONET RECEIVER ASSEMBLY
Materials Required
QUANTITY DESCRIPTION REFERENCE NUMBER
1Bayonet Receiver Assembly 93A8514
As required Adhesive MIL-A-5540
NSN 8040-00-515-2245
CAUTION
Before drilling holes in the helmet shell, ensure that the TPL assembly
and chin/nape strap assembly are properly fitted and adjusted to the
aircrew member’s head. (Fitting instructions are in paragraph 2-2.)
Location/alignment of the bayonet receiver assembly is critical, since
the bayonet receivers are not adjustable.
1. Have the aircrew member don the properly fitted helmet.
2. Insert each oxygen mask bayonet into a jaw receiver to the third locking position.
The projections on the jaw receiver should be positioned toward the tip of the
bayonet.
3. Referring to Figure 2-8, have the aircrew member hold the properly adjusted oxygen
mask against his/her face.
NOTE
Ensure that the oxygen mask straps
have equal tension.
Ensure that the jaw receivers are
placed no closer than 1/2 inch
(12.7 mm) from the edge of the
helmet shell.
4. Hold each jaw receiver firmly against
the helmet, ensuring that each offset
bayonet is flush with and parallel to the
edgeroll. Use a lead pencil to trace the
outline of each jaw receiver assembly
onto the helmet. Do not use marker or
grease pencil.
2-9
Figure 2-8. Positioning Oxygen Mask

5. While holding only the bayonet
receiver spacers against the
helmet at the marked
positions, use a lead pencil as
shown in Figure 2-9 to mark the
screw holes onto the helmet
shell.
CAUTION
When drilling holes in the
helmet shell, hold the drill
perpendicular to the shell to
prevent damage to the shell.
6. Remove the earcup
assembly on one side.
Referring to Figure 2-10,
pull back the earcup
pile fastener fabric
inside the helmet
shell on the same
side. Using a #25 drill
bit, drill the marked
hole locations. Repeat
for the other side.
NOTE
You may apply a small
amount of general-purpose
wood glue to each screw
before you add the lock
washer and backplate.
You should fit each spacer
against the riveted side
of the jaw receiver.
2-10
Figure 2-10. Earcup Pile Fastener Pulled Back
Figure 2-9. Marking Screw Holes

7. Hold the pile fastener fabric away from the helmet shell. Referring to Figure 2-11,
insert screws with lock washers through the backplate and the inside of the helmet
shell. Attach the spacers and receivers to the outside of the helmet shell. Ensure
that the jaw receiver projections point to the rear of the helmet.
8. Tighten all screws so that the jaw receivers and spacers are firmly attached to the
helmet.
9. Cement the earcup pile fastener fabric to the inside of the helmet shell. Cut an “X”
pattern into the fabric across each screw head to facilitate inspection and tightening.
10.Reinstall the earcup assembly.
2-11
Figure 2-11. Bayonet Receiver Assembly
SCREW
LOCKWASHER
BACKPLATE
SPACER
JAW RECEIVER

2-5. INSTALLATION OF LIGHTWEIGHT VISORS
Materials Required
QUANTITY DESCRIPTION REFERENCE NUMBER
1Lightweight visor, clear 81D5189-3
1Lightweight visor, neutral gray 81D5189-4
1Visor cover 82C5701
1. Remove the tissue paper from
the visor bags. Open the visor
bags, and remove the visors.
2. Referring to Figure 2-12, install
the clear or neutral visor by
stretching the end of the strap
slightly past the helmet snap
and fastening the visor snap to
the helmet snap from front to
back. Repeat for the other
side.
3. Adjust the visor straps as
desired by sliding the buckles.
4. Referring to Figure 2-13,
install the visor cover by
attaching the hook fastener
on the inside of the visor
cover to the pile fastener
on the outer visor on both
sides.
2-12
Figure 2-12. Installing Visor
Figure 2-13. Installing Visor Cover

2-6. ANVIS MOUNT MODIFICATION (DUAL VISOR ASSEMBLY)
Before the ANVIS NVG can be installed, the ANVIS mount must be modified and a
cable clip attached. The ANVIS modification kit contains four screws for the rear of the
mount, a cable clip and attaching screw, and pile fastener for ANVIS battery pack at-
tachment to the helmet. Referring to Figure 2-14, perform the modification as follows :
1. Remove the nut from the right side (as worn) of the ANVIS mount, and place the
strain relief clamp over the end of the screw threads.
2. Place the wires under the clamp arm, and replace the nut over the clamp and screw
threads. Tighten the nut until secure.
3. Position the backing plate on the rear of the mount so that the screw holes are
aligned and the plate is flush with the top and bottom of the rear of the mount.
Ensure that the wires extending from the rear of the mount are aligned in the slots in
the mount to prevent crushing of the wires.
4. Applying a small amount of thread locking adhesive to the threads of each locating
pin, secure the backing plate to the mount with the pins. Ensure that the two pins
with the longer tapered heads are installed in the two top holes. Tighten the pins
until secure, but do not over-tighten them.
5. Remove the backing from the hook fastener. Wrap the hook fastener around the
cable connector until the ends meet as shown in Figure 2-14.
2-13
Figure 2-14. ANVIS Modification Kit (*P/N 90A7946-6)
* TOP LOCATING PINS
(LONG TAPERED HEADS)
* BOTTOM LOCATING PINS
(SHORT TAPERED HEADS)
* BACKING PLATE
* CABLE STRAIN RELIEF
CLAMP (SHOWN INSTALLED)
* HOOK FASTENER
(SHOWN INSTALLED)
ANVIS MOUNT, CFE
(CUSTOMER
FURNISHED
EQUIPMENT)