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Chapter 2: Helmet Preparation and Operation

2-4   OPERATION

This section contains a summary of the helmet operational tasks described in the fitting and 

installation sections of this chapter. Operational tasks include donning the helmet, fastening and 

adjusting the chin strap, operating the visor, and connecting the mask microphone cord to the 

helmet connector.

2-4 1   Donning Helmet

Don the helmet as follows:

1.  Grasp the helmet in the earcup 

areas.

2.  Referring to 

Figure 2-29

, place 

the front of the helmet against the 

forehead, and rotate the helmet 

toward the rear and down onto the 

head.

3.  Ensure that the ears are centered 

in the earcups.

2-4 2   Fastening Chin Strap

Referring to 

Figure 2-30

, fasten and 

adjust the chin/nape assembly as 

follows:

1.  Snap the chin strap.

2.  Pull on the end of the chin strap to 

adjust it for a snug fit.

3.  Attach the end of the chin strap 

securely to the pile fastener on the 

chin pad.

Nape pad

(inside helmet)

LOWER FRONT VIEW OF HELMET

Snap

Buckle

End of chin strap

Chin pad

Figure 2-29. Donning Helmet

Figure 2-30. Fastening Chin Strap

For the safety of the aircrew member, 

the chin strap must remain firmly 

secured at all times of flight. This 

prevents helmet rotation during 

high-G maneuvers, or loss of helmet 

during emergency ejection

Summary of Contents for HGU-55/P

Page 1: ...Operation and Maintenance Instructions with Illustrated Parts Breakdown Lightweight HGU 55 P Helmet Assembly 2011 Gentex Corporation...

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Page 3: ...product Use of non Gentex parts salvage refurbished etc for replacement or additional installation will void any product warranty and may compromise the safety of the user Proper fitting operation an...

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Page 5: ...CL or XLiner 9 2 2 3 Checking Helmet Fit and Operation 10 2 3 BAYONET RECEIVER INSTALLATION 15 2 3 1 Installing Standard Bayonet Receivers 15 2 3 2 Installing Anti Snag Receiver Spacer Kit 19 2 4 OPER...

Page 6: ...t of Bayonet Receivers 37 3 4 6 Replacement of TPL SCL or XLiner 37 3 4 7 Replacement of Energy Absorbing Liner 38 3 4 8 Replacement of Integrated Chin Nape Strap Assembly 40 3 4 9 Replacement of Viso...

Page 7: ...needed to maintain the helmet 1 2 HELMET DESCRIPTION The HGU 55 P Helmet Figure 1 1 provides basic head protection sound attenuation and communications for aircrew personnel The helmet features a sna...

Page 8: ...ress conditions Tightening the chin strap also tightens the fit of the nape pad Metal clamps help keep the adjusted chin strap in place Headset The headset allows the aircrew member to communicate bot...

Page 9: ...gy absorbing liner Visor Helmet shell Pile fastener Earcup Earphone Clamp Nape pad Clamp Chin strap Standard bayonet receiver kit Anti snag receiver spacer kit Cable Jack holder Leather buffer Edgerol...

Page 10: ...solate problem components Instructions provided with each tester Table 1 2 Tools ITEM PURPOSE Caliper To measure head length width and height for determining helmet size may be locally manufactured fr...

Page 11: ...helmet components Isopropyl alcohol 70 percent solution To clean the visor Thread locking adhesive MIL S 22473 Grade C or equivalent To apply to bayonet receiver screws during installation or replace...

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Page 13: ...0 knots indicated airspeed KIAS A properly fitted helmet also aids in maintaining the stability of helmet mounted devices such as night vision goggles In addition a proper fit ensures a comfortable he...

Page 14: ...t aluminum plastic or cardboard Ruler calibrated in inches to tenths or metric used to obtain the dimensions of the caliper measurements Continued on next page Proper fitting of the helmet is imperati...

Page 15: ...ot indent the skin surface 2 Record the measurement Selecting Helmet Size Based on Measurements Compare the head length and head width measurements to the sizing parameters shown in Table 2 1 and sele...

Page 16: ...two screws on each nape strap clamp Move both clamps down as far as possible on the straps to provide slack during the fitting process 2 Temporarily insert a piece of paper or plastic between each ear...

Page 17: ...p 11 next page If the height is not correct perform Step 7 7 Attempt to adjust the height by rotating the helmet forward or rearward as applicable Readjust the chin strap Perform Step 8 8 Check the he...

Page 18: ...emove the helmet Referring to Figure 2 8 attach one or more fitting pads to the back of each earcup Then continue to Step 14 NOTE You can install the fitting pads whole or cut them to any size or shap...

Page 19: ...t the visor straps to center the visor over the nose Ensure that the visor is snug enough it should not slide freely up and down There should be enough resistance to require pulling the visor away fro...

Page 20: ...ad and remove the chin pad from the chin strap g Cut the strap at the trim line h Sear the cut edge to prevent the strap from unraveling i Fold the cut end of the chin strap under doubled 1 4 inch or...

Page 21: ...also familiarize the aircrew member with mask attachment in this procedure Tools and Equipment Required Pencil Drill with 25 5 32 drill bit Small cross tip screwdriver Adhesive polychloroprene MIL A...

Page 22: ...ically positioned place the bayonet receiver on the helmet with the projection facing aft as shown in Figure 2 15 Ensure that the numbered side of the receiver faces the helmet shell 5 Hold the receiv...

Page 23: ...2 1 16 drill bit before drilling full size holes 9 Ensuring that the pile fastener inside the helmet is not in the drilling area drill both the right and the left marked hole locations with a 25 drill...

Page 24: ...stener material firmly against the shell surface Allow the adhesive to set at least 15 minutes ideally you should allow it to set overnight 14 Use a utility knife to cut an X pattern through the pile...

Page 25: ...t you have the following components of the anti snag receiver spacer kit Two anti snag spacers Two 5 16 MS51957 27B screws Four 1 2 MS51957 30B screws Six lock washers NOTE If the aircrew member has w...

Page 26: ...Figure 2 24 shows the right hand spacer on the right hand side of the helmet as worn 5 Mark the top spacer hole as follows a On one side of the helmet align the holes of the anti snag spacer Figure 2...

Page 27: ...e that the edgeroll is trimmed or pushed back so that the backplate will lie flush against the inside of the helmet d Install the MS51957 27B screw and washer into the anti snag spacer where the hole...

Page 28: ...ility knife to cut an X pattern in the pile fasteners over the screws This will permit future inspection and tightening of the screws 11 Reattach both earcups to the pile fasteners 12 Reinstall the vi...

Page 29: ...rotate the helmet toward the rear and down onto the head 3 Ensure that the ears are centered in the earcups 2 4 2 Fastening Chin Strap Referring to Figure 2 30 fasten and adjust the chin nape assembly...

Page 30: ...lower it NOTE When the visor is up you can attach the visor cover by pressing the hook fasteners on the cover to the pile fastener on the visor 2 4 4 Connecting Mask Microphone Cord to Helmet Connect...

Page 31: ...or dispose of it as applicable 2 Inspect the helmet for any damage incurred during shipment such as breaks or cuts in the helmet shell or scratches or cracks in the visor 3 Replace all damaged parts...

Page 32: ...re that the energy absorbing liner is securely attached to the helmet and is free of holes and cracks 9 Ensure that the TPL or XLiner is securely attached properly fitted and free of holes or tears 10...

Page 33: ...MQ1A tester DMH 1 tester or another tester while the mask microphone is connected to the helmet headset Speak into the microphone The microphone and earphones are working when the voice is transmitted...

Page 34: ...ecurely adhered to the liner and that they hold the TPL or XLiner securely 6 Inspect the chin strap and the nape strap to ensure that the fabric and stitching are not torn and that the chin strap buck...

Page 35: ...ition of all helmet attaching hardware 3 3 CLEANING Helmets should be cleaned at regular intervals to ensure that they are in serviceable condition and to prevent the possibility of dermatitis Users a...

Page 36: ...ht 6 TPL or SCL Do the following a Remove the TPL or SCL from the helmet b Referring to Figure 3 1 note the manner in which the cloth cover is installed on the plastic layers The holes in the plastic...

Page 37: ...temperatures can exceed 200 F 93 3 C on an 85 F 30 C day The TPL or SCL cover can be hand washed only Use mild detergent only no bleaches or machine detergents Do not put the TPL or SCL cover in the...

Page 38: ...finish 78B4170 1 Tools Materials Required None Procedure Referring to Figure 3 3 replace the jack holder as follows 1 Remove the cable connector from the jack holder 2 Remove the jack holder by rotati...

Page 39: ...s inside the helmet 2 Note how the existing earseals are installed on the earcups then remove the earseals from the earcups 3 Stretch the replacement earseals over the earcups in the same manner in wh...

Page 40: ...ter Procedure 1 Referring to Figure 3 5 pull the earphone out the earcup as follows a Detach one earcup from the pile fastener inside the helmet b Remove the earphone holder from the earcup Optional Y...

Page 41: ...gh the small hole and insert the small rubber grommet into the hole Ensure that the grommet is seated properly NOTE To ease insertion of the grommet you may lubricate the grommet with a small amount o...

Page 42: ...rring to Paragraph 3 4 3 perform Steps 1 2 to remove the cable leads from both earcups 2 Referring to Figure 3 7 do the following a Remove the cable connector from the jack holder b Remove the jack ho...

Page 43: ...ommet you may lubricate the grommet with a small amount of soap and water or 70 percent isopropyl alcohol g Press the jack holder against the large grommet and rotate it counterclockwise h Insert the...

Page 44: ...egrated chin nape strap to the helmet to ease removal and installation of the energy absorbing liner d Referring to Figure 3 9 insert a thin flexible metal spatula between the inner surface of the hel...

Page 45: ...iner firmly against the inside surface of the front helmet shell edgeroll Ensure that the liner is centered within the helmet b Press the rear portion of the liner into place ensuring that the rear ed...

Page 46: ...m wire coat hanger Procedure 1 Referring to Figure 3 12 do the following a Remove the TPL or XLiner and detach both earcups from the helmet b Remove the screws flat washers lock washers and T nuts tha...

Page 47: ...he chin pad is on this strap 4 Referring to Figure 3 12 previous page insert the nape straps through the nape pad NOTE Ensure that the straps are not twisted Optional To make this task easier you can...

Page 48: ...t Figure 3 14 Fasten each snap from front to back Adjust each visor strap for a snug fit to the helmet 3 Test visor operation as described in Paragraph 2 2 3 Figure 3 14 Installing Visor Edgeroll cove...

Page 49: ...rethane paint lusterless gray NSN 8010 01 167 1139 320 grit sandpaper Epoxy filler putty NSN 8040 00 753 4800 Putty knife squeegee or other applicator suitable for epoxy filler putty Epoxy primer pain...

Page 50: ...evel with the helmet shell 5 Repeat Steps 3 and 4 until the repair is level and smooth NOTE When accessory components are removed and relocated unused holes in the helmet shell may be filled by using...

Page 51: ...ivers as follows 1 To remove paint hand sand using wet 320 grit sandpaper feathering chipped or cracked areas of paint 2 Paint the receivers with one coat of primer coating epoxypoyamide MIL P 23377 a...

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Page 53: ...GU 55 P helmet with MBU 20 P visors 81D5330 16 Medium 81D5330 17 Large or 81D5330 18 X Large The parts breakdown contains illustrations paired with lists of parts Illustration numbers are shown in the...

Page 54: ...48 Chapter 4 Replacement Parts and Optional Items Figure 4 1 HGU 55 P Helmet Components 1 2 3a 4 5 6 7 8 9 11 10 3b...

Page 55: ...arge 1 F I 2 85D7081 1 97427 Energy Absorbing Liner Medium 1 A D G 85D7082 1 97427 Energy Absorbing Liner Large 1 B E H 85D7083 1 97427 Energy Absorbing Liner X Large 1 C F I 3a 85D7087 1P 97427 TPL K...

Page 56: ...bly Large Black See Figure 4 4 for breakdown 1 B E H 90D7916 6 97427 Integrated Chin Nape Assembly X Large Black See Figure 4 4 for breakdown 1 C F I 90B7948 1 97427 Integrated Chin Nape Assembly Medi...

Page 57: ...087 3P 97427 TPL Kit X Large REF C F I 1 88D7518 1 97427 Layer Assembly Medium 1 A D G 88D7518 2 97427 Layer Assembly Large 1 B E H 88D7518 3 97427 Layer Assembly X Large 1 C F I 2 85D7088 1 97427 Cov...

Page 58: ...Y UOC 4 3 80C4754 3 97427 Headset Asssembly REF 1 80C4758 97427 Earcup 2 2 67A1697 97427 Filler Pad 2 3 69B2032 97427 Earphone H 143 AIC 2 4 70A2249 97427 Earphone Holder 2 5 75C2990 97427 Earseal 2 6...

Page 59: ...27 Nape Strap with Snap Medium 1 A D G 89B7730 2 97427 Nape Strap with Snap Large X Large 1 B C E F H I 3 84D6899 1 97427 Nape Pad Leather Black Medium 1 A D G 84D6899 2 97427 Nape Pad Leather Black L...

Page 60: ...QTY UOC 4 5 05A12024 1 97427 Anti Snag Receiver Spacer Kit REF D E F 1 MS51957 27B 97427 Screw Pan Head 6 32 x 5 16 2 2 MS51957 30B 97427 Screw Pan Head 6 32 x 1 2 4 3 MS35335 58 97427 Washer Lock Ex...

Page 61: ...6 82A5614 20 97427 Bayonet Receiver Kit REF 1 MS51957 29 97427 Screw Pan Head Cross Recessed 6 32 x 7 16 4 2 MS35335 58 97427 Washer Lock External Tooth 6 4 3 82A5722 97427 Backing Plate 2 4 80B4858 9...

Page 62: ...ad shapes through body heat to ensure increased stability nearly eliminating the need for custom fitting The SCL cloth cover provides a more comfortable plush feel than the standard TPL cover Leather...

Page 63: ...gh contrast MBU 20 P 91A8058 1 Gradient MBU 12 P 81D5189 11 Gradient MBU 20 P 91A8058 2 The high contrast visor yellow enhances vision in snowy foggy hazy or cloudy environments it causes the blue por...

Page 64: ...utral gray visors are raised and lowered with actuating knobs at the sides Dual visor kit Figure 4 15 MBU 12 P 85B7050 1 MBU 20 P 85B7050 3 The dual visor kit includes a visor cover and clear and neut...

Page 65: ...sk bayonets They are also hinged to allow the mask to swing away from the helmet without obscuring instrumentation to the left or right In addition they feature an anti snag contour to prevent parachu...

Page 66: ...kit with friction holding edgeroll cover and anti snag receiver spacers for use in high speed high G environments The helmet also has pre drilled holes for the installation of night vision goggle NVG...

Page 67: ...ohm dynamic 78A4046 1 Microphone 150 ohm dynamic 77A3484 Microphone electret 79B4568 2 Communications cord 25 inches with U 174 plug 77C3523 1 Lower cord with mask boom switch 06D12449 1 Flex booms Fi...

Page 68: ...62 Chapter 4 Replacement Parts and Optional Items TPL and XLiner are registered trademarks of Gentex Corporation SCL is a trademark of Gentex Corporation...

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Page 70: ...TP0351 DECEMBER 2011...

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