ModularAircrewCommonHelmetSpecVer21(26Sep06).doc

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PERFORMANCE SPECIFICATION

Modular Aircrew Common Helmet

26 September, 2006

AMSC

FSC XXXX

TABLE OF CONTENTS

11.0

SCOPE

11.1 Scope

22.0

APPLICABLE DOCUMENTS

22.1 General

22.2 Government Documents

22.2.1 Specifications, Standards, and Handbooks

32.2.2 Other Government documents, drawings, and publications

32.3 Non-Government publications

32.4 Order of Precedence

43.0

SYSTEM REQUIREMENTS

43.1 General

43.1.1 Requirements

43.1.2 Objective

43.1.3 First article

43.1.4 Materials

43.1.5 Recycled, recovered, or environmentally preferable materials

43.2 Design and construction

43.2.1 Equipment Compatibility (KPP)

53.2.2 Human factors engineering

53.2.3 Logistics

53.2.4 Aircraft Compatibility

53.2.5 Reliability

53.2.6 Maintainability

53.2.7 Durability

53.2.8 Support Equipment

63.2.9 Maintenance Planning

63.2.10 Maintenance Environment

63.2.11 Inspections

63.2.12 Technical Data

63.2.13 Manpower

73.2.14 Service life

73.2.15 Coating adhesion

73.2.16 Training

73.3 Performance characteristics

73.3.1 Stability (KPP)

83.3.2 Force protection (KPP)

83.3.3 Head Supported Weight

83.3.4 Mass properties

103.3.5 Anthropometric Accommodation (sizes)

103.3.6 Acoustic Dose

103.3.7 Speech intelligibility

103.3.8 In-flight mission reconfiguration

103.3.9 Endurance

113.3.10 Visor/visual compatibility

113.3.11 Field of view/regard

113.3.12 Penetration protection

113.3.13 Retention

123.3.14 Bulk

123.3.15 Spinal Alignment

123.3.16 Emergency ground egress

123.3.17 Fire safety

123.3.18 Donning

123.3.19 Doffing

123.3.20 Maxillofacial protection

123.3.21 Valsalva

123.3.22 Habitability

133.3.23 Operability

133.3.24 Positive pressure breathing

133.3.25 Temperature and moisture control

133.3.26 Materials and helmet shape

133.3.27 Survival and Rescue Compatibility

143.3.28 Chinstrap release time

143.3.29 Visor lenses

143.3.30 MACH wiring connection

143.3.31 Head Motion

143.3.32 Electromagnetic interference (EMI)

143.3.33 Windblast resistance

153.3.34 Ejection

153.3.35 Bailout

153.3.36 Parachute deployment and descent

153.3.37 Riser deployment

153.3.38 Oxygen mask release

153.3.39 Color

153.3.40 IR signature

163.4 Fit.

163.4.1 Fit/wearability

163.5 Communications

163.5.1 Audio Compatibility

163.5.2 Internal Communications Systems (ICS)

163.5.3 Audio performance

163.5.4 Volume control

163.5.5 3-D Audio

163.5.6 External Audio

163.5.7 Communication devices

173.5.8 Boom microphone

173.6 Aircrew Helmet Noise Reduction (AHNR)

173.6.1 Fail safe design

173.6.2 Feedback

173.6.3 Sound pressure level (SPL) spikes

173.6.4 On/off switch

173.6.5 Batteries

173.6.6 Battery life

173.6.7 Battery life indicator

183.7 Neck protection

183.7.1 Neck tension limits

183.7.2 Neck compression and shear force limits

193.7.3 Combined Neck Moment and Load Limits

193.7.4 Neck X and Z Moment Limits

193.8 Environmental considerations

193.8.1 Atmospheric Pressure change

203.8.2 Altitude protection

203.8.3 Electromagnetic Interference/Electromagnetic Compatibility (EMI/EMC)

203.8.4 Electrostatic discharge (ESD)

203.8.5 Storage Temperature

203.8.6 Operational Temperature

203.8.7 Temperature, altitude, and humidity

203.8.8 Temperature shock

203.8.9 Salt fog

203.8.10 Humidity

203.8.11 Blowing Dust

213.8.12 Blowing Sand

213.8.13 Solar Radiation

213.8.14 Rain

213.8.15 Fungus

213.8.16 Transit Drop

213.8.17 Rapid decompression

213.8.18 Explosive Decompression

213.8.19 Immersion

213.8.20 Explosive atmosphere

213.8.21 Vibration curves

213.8.22 Acceleration

223.8.23 Shock

223.8.24 Vibration

223.8.25 Nuclear, Biological, and Chemical Survivability

234.0

VERIFICATION

234.1 Scope

234.2 First article testing

234.3 Production lot testing

234.4 Functionality check

244.5 Methods

314.6 Design and construction

314.6.1 Equipment compatibility (KPP)

324.6.2 Human factors engineering

324.6.3 Logistics

324.6.4 Aircraft Compatibility

324.6.5 Reliability

324.6.6 Maintainability

324.6.7 Durability

324.6.8 Support Equipment

324.6.9 Maintenance Planning

324.6.10 Maintenance Environment

324.6.11 Inspections

324.6.12 Technical Data

334.6.13 Manpower

334.6.14 Service life

334.6.15 Coating adhesion

334.6.16 Training

334.7 Performance characteristics

334.7.1 Stability (KPP)

334.7.2 Force protection (KPP)

344.7.3 Head supported weight

344.7.4 Mass properties

344.7.5 Anthropometric Accommodation (sizes)

344.7.6 Acoustic Dose

344.7.7 Speech intelligibility

344.7.8 In-flight mission reconfiguration

354.7.9 Endurance

354.7.10 Visor/Visual compatibility

354.7.11 Field of view/regard

354.7.12 Penetration protection

374.7.13 Retention

374.7.14 Bulk

374.7.15 Spinal Alignment

374.7.16 Emergency ground egress

384.7.17 Fire Safety

384.7.18 Donning

384.7.19 Doffing

384.7.20 Maxillofacial protection

384.7.21 Valsalva

384.7.22 Habitability

384.7.23 Operability

384.7.24 Positive pressure breathing

394.7.25 Temperature and moisture control

394.7.26 Materials and helmet shape

394.7.27 Survival and rescue compatibility

394.7.28 Chinstrap release time

394.7.29 Visor lenses

404.7.30 MACH wiring connection

404.7.31 Head motion

404.7.32 Electromagnetic interference (EMI)

404.7.33 Windblast resistance

404.7.34 Ejection

414.7.35 Bailout

414.7.36 Parachute deployment and descent

424.7.37 Riser deployment

424.7.38 Oxygen Mask Release

424.7.39 Color

424.7.40 IR signature

424.8 Fit

424.8.1 Fit/wearability

434.9 Communications

434.9.1 Audio Compatibility

434.9.2 Internal Communications Systems

434.9.3 Audio performance

434.9.4 Volume Control

444.9.5 3-D audio

444.9.6 External audio

444.9.7 Communication devices

444.9.8 Boom microphone

444.10 Aircrew Helmet Noise Reduction

444.10.1 Fail safe design

444.10.2 Feedback

444.10.3 Sound Pressure Level Spikes

454.10.4 On/off switch

454.10.5 Batteries

454.10.6 Battery life

454.10.7 Battery life indicator

454.11 Neck protection

454.11.1 Neck tension limits

454.11.2 Neck compression and shear force limits

454.11.3 Combined Neck Moment and Load Limits

464.11.4 Neck X and Z Moment Limits

474.12 Environmental considerations

474.12.1 Atmospheric pressure change

474.12.2 Altitude protection

474.12.3 Electromagnetic interference/electromagnetic compatibility

474.12.4 Electrostatic discharge

474.12.5 Storage temperature

474.12.6 Operational Temperature

484.12.7 Temperature, altitude, and humidity

484.12.8 Temperature shock

484.12.9 Salt fog

484.12.10 Humidity

484.12.11 Blowing dust

494.12.12 Blowing sand

494.12.13 Solar radiation

494.12.14 Rain

494.12.15 Fungus

494.12.16 Transit Drop

494.12.17 Rapid decompression

494.12.18 Explosive decompression

504.12.19 Immersion

504.12.20 Explosive Atmospheres

504.12.21 Vibration curves

504.12.22 Acceleration

504.12.23 Shock

504.12.24 Vibration

514.12.25 Nuclear, Biological, and Chemical Survivability

525.0

PACKAGING

525.1 Packaging

536.0

NOTES

536.1 Intended use

536.2 Acquisition requirements

536.3 Subject term (key word) listing.

536.4 Changes from previous issue

54APPENDIX A – Equipment Compatibility

55APPENDIX B – Aircraft Compatibility

57APPENDIX C – Acoustic Dose

Table of Tables 8Table 3‑1: Head Impact Limits

11Table 3‑2: Field of View Requirement

18Table 3‑3 Neck tension force and duration limits for a given occupant size

18Table 3‑4 Neck compression and shear force limits for a given occupant size

24Table 4‑1: Verification Matrix

41Table 4‑2: Ejection Test Matrix

46Table 4‑3: Critical intercept values for Nij calculation at C0-C1 and C7-T1 for a given occupant size

46Table 4‑4: Values for NMI calculation at C0-C1 and C7-T1 for a given occupant size

Table of Figures 9Figure 3‑1: Vertical of Mass Placement as a Function of head-supported mass

9Figure 3‑2: Allowable head-supported mass as a function of longitudinal center of mass placement

9Figure 3‑3: Knox Box Plot

36Figure 4‑1: Tear Penetration Holding Fixture and Penetration Impactor

37Figure 4‑2: Tear Penetration Impact Test Tower

1.0 SCOPE

1.1 Scope

This specification covers the requirements for the Modular Aircrew Common Helmet (MACH). The MACH is single modular helmet system capable of meeting all rotary and fixed wing mission requirements. MACH will replace the HGU-56/P, IHADSS IHU (Integrated Helmet and Display Sighting System Integrated Helmet Unit), HGU-84/P, Marine’s Super Cobra Helmet, HGU-68/P, HGU-55/P, HGU-55A/P and the Joint Strike Fighter (JSF) flyers’ helmets. The key performance parameters for the MACH are Stability, Equipment Compatibility, and Force Protection. In addition the MACH will integrate with existing and planned aircraft and Life Support Equipment (LSE) used by the Air Force, Army, and Navy.

The MACH is critical to normal and egress procedures. MACH will be capable of withstanding an ejection speeds up to 600 KEAS while mitigating the likelihood of injury to the head and neck. It shall adequately protect and maintain the maneuverability of a crewman’s head in a high “G” environment. The MACH will also provide impact protection for those aircraft where ejection is not possible. In addition it will be a platform for Helmet Mounted Devices (HMD) and shall maintain stability to ensure that the HMDs performance is not degraded.

2.0 APPLICABLE DOCUMENTS

2.1 General

The documents listed in this section are referenced in sections 3, 4, or 5 of this standard. This section does not include documents cited in other sections of this standard or recommended for additional information or as examples. While every effort has been made to ensure the completeness of this list, document users are cautioned that they must meet all specified requirements of documents cited in sections 3, 4, and 5 of this standard, whether or not they are listed.

2.2 Government Documents

2.2.1 Specifications, Standards, and Handbooks

The following specifications, standards, and handbooks form a part of this document to the extent specified herein. Unless otherwise specified the issues of these documents are those listed in the issue of the Department of Defense Index of Specifications and Standards (DoDISS) and supplement thereto, cited in the solicitation.

DEPARTMENT OF DEFENSE SPECIFICAITONS

(Unless otherwise indicated, copies of the above specifications, standards, and handbooks are available from the Standardization Document Order Desk, 700 Robbins Avenue, Building 4D, Philadelphia, PA 19111-5094 or www.dodssp.daps.mil.)

2.2.2 Other Government documents, drawings, and publications

The following other Government documents, drawings, and publications form a part of this document to the extent specified herein. Unless otherwise specified, the issues are those cited in the solicitation.

2.3 Non-Government publications

The following document form a part of this document to the extent specified herein. Unless otherwise specified, the issues are those cited in the solicitation or contract.

AMERICAN NATIONAL STANDARDS INSTITUTE (ANSI)

(Application for copies of ANSI Standards should be addressed to the American National Standards Institute, Inc., 1430 Broadway, New York, NY 10018.)

2.4 Order of Precedence

In the event of a conflict between the text of this document and the references cited herein, the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained.

3.0 SYSTEM REQUIREMENTS

3.1 General

3.1.1 Requirements

The MACH system requirements specified herein are separated into the following categories: design and construction, performance requirements, fit, communications, aircrew helmet noise reduction, neck protection and environmental considerations. Objective requirements are the desired level of performance. Threshold requirements are the minimum acceptable level of performance and must be met in the event that a common objective requirement cannot be met.

The MACH system shall include the helmet, head tracker and helmet mounted display (when applicable), mask, ear cups, microphone and 6 inches of HMD cord (from the base of the helmet) and 3 inches (7.62 cm) of oxygen hose and communications cord.

3.1.2 Objective

The objective of the MACH system is to provide a single helmet system that is capable of meeting all rotary and fixed wing mission requirements. The MACH system will provide the ability to change mission roles from a standard 600 knot ejection safe tactical fixed wing mission to a standard rotary wing mission.

3.1.3 First article

When specified (see 6.2), a sample shall be subjected to first article inspection in accordance with 4.2.

3.1.4 Materials

The contractor shall select materials capable of meeting all of the operational and environmental requirements specified herein. The materials specified in MIL-P-11268 are recommended, but are not mandatory.

3.1.5 Recycled, recovered, or environmentally preferable materials Recycled, recovered, or environmentally referable materials should be used to the maximum extent possible provided that the material meets or exceeds the operational and maintenance requirements, and promotes economically advantageous life cycle costs.

3.2 Design and construction

3.2.1 Equipment Compatibility (KPP)

The common helmet shall provide the ability to interface with mission-specific Aviation Life Support Equipment (ALSE) listed, but not limited to, in: APPENDIX A – Equipment Compatibility.

3.2.2 Human factors engineering

The design and construction of the MACH will incorporate human engineering design principles, using MIL-STD-1472 as a guide, to ensure that the equipment can be operated and maintained in an effective, efficient, and safe manner by appropriately trained personnel throughout the range of its intended operating environments. In addition, the MACH will be able to be operated and maintained by 99% appropriately trained aircrew personnel with 90% confidence.

3.2.3 Logistics

The MACH system variants shall use common components to reduce the logistical footprint.

The MACH system shall be organically supportable by Defense Logistic Agencies, military depots, and multiple services.

3.2.4 Aircraft Compatibility

The MACH shall be compatible with the aircraft listed, but not limited to, in APPENDIX B – Aircraft Compatibility.

3.2.5 Reliability

The MACH system shall have a minimum acceptable mean-time-between-critical failure (MTBCF) of 7 years.

3.2.6 Maintainability

The MACH system Mean-Time-To-Repair (MTTR) shall not exceed 0.5 hours, with 95 percent of the tasks not exceeding 3.0 hours.

3.2.7 Durability

The MACH system shall be shatter proof and have the abrasion/corrosion resistance equal to the current system.

The MACH system will be shatter proof and have abrasion/corrosion resistance better than the current system.

3.2.8 Support Equipment

Existing tools, Test Measurement and Diagnostics Equipment (TMDE) and/or presently approved emerging TMDE or SE shall be used if possible. If new TMDE or SE is required, it shall be provisioned for and provided as part of the system. Removal, repair, replacement, adjustment, modification, checkout, and calibration shall be accomplished using common shop tools. Special tools or equipment shall be kept to a minimum and delivered as part of the support package.

3.2.9 Maintenance Planning

Maintenance, repair, and reconstitution tasks for the MACH system shall be accomplished by appropriately qualified organizational level Life Support Specialist/Aviation Life Support Equipment/Parachute Rigger personnel. The MACH system shall exhibit a cost-effective, supportable design with emphasis on optimizing logistics resources using an Integrated Logistics Support (ILS) plan.

3.2.10 Maintenance Environment

The MACH system design shall allow maintenance to be performed at operating bases/locations worldwide to include mobile, sea-based, and bare-base facilities. The MACH system design shall allow maintainability even when the technician is fully dressed in protective clothing, to include arctic and Mission Oriented Protective Posture -4 (MOPP-4).

3.2.11 Inspections

Periodic inspections and preventive maintenance tasks for the MACH system shall be sufficient to ensure system integrity. Routine inspections of the MACH system shall be sufficient to validate operational status. The MACH system inspection intervals shall be a minimum of 30 days.

3.2.12 Technical Data

Technical orders/manuals (TO/TM), user manuals, and vendor documentation for integration/operation and repair for the MACH system shall include at a minimum illustrated parts breakdowns, parts listings, diagrams, theory of operation, maintenance, and troubleshooting guides. The technical data of the MACH system shall be formally verified, validated, and approved by the appropriate agencies prior to the delivery of the first system. Time and cost to fully incorporate technical data for the MACH system shall be part of the program cost and schedule.

3.2.13 Manpower

Manning for the MACH system shall meet current authorized manning levels. Specifically, no additional logistics, maintenance or life support authorizations shall be required to support the MACH system. Opportunities to integrate improved reliability and maintainability features into the helmet to reduce manpower requirements shall be explored.

Manning for the MACH system will reduce current authorized manning levels.

3.2.14 Service life

The equipment will be durable and economically maintainable throughout the design service life when exposed to the environment defined herein. Durability for the equipment will be adequate to resist fatigue damage, wear and deterioration/thermal degradation, and corrosion during operational and maintenance usage such that the functional capability of the equipment is not impaired for the service life of the components. The service life of the MACH shall be 7 years.

3.2.15 Coating adhesion

All surfaces of the helmet assembly and its component subassemblies finished in accordance with MIL-C-46168 shall not show evidence of lifting of any square.

3.2.16 Training

The vendor of the MACH system shall provide a training package to the service training commands. Service training commands shall establish initial and follow on training requirements to include instruction on the fit, inspection, maintenance, and use of the helmet. Vendors shall provide and Services shall ensure the appropriate training units are provided the necessary assets, test equipment, and technical manuals to conduct training.

3.3 Performance characteristics

3.3.1 Stability (KPP)

The MACH shall provide a stable fixed reference to the user’s eye through the full range of aircraft operations including land, water, and carrier takeoff and landing. When used with helmet mounted equipment there shall be no distortion or vignetting of symbology or imagery or loss of resolution of optical systems independent of head/helmet orientation and position throughout the dynamic envelope to include vibration, multiple shocks, and sustained acceleration. Specifically, stability shall be maintained during high angle-of-attack maneuvers, aircraft buffeting, and propulsion-induced oscillations when optimum performance is critical.

3.3.2 Force protection (KPP)

Each MACH system location shall not exceed the specified impact force and dynamic response levels in Table 3‑1.

Table 3‑1: Head Impact Limits

3.3.3 Head Supported Weight

The MACH flight-ready configuration including head protection, eye protection, oxygen mask receivers, sound attenuation, earphone elements, and shell final color coat weight shall not exceed 2.60 pounds.

3.3.4 Mass properties

The MACH system (including HMD, NVG, displays, head trackers, oxygen masks and chemical masks) mass and center-of-gravity (cg), shall not exceed the limits defined by the USAARL mass/cg curves (Figure 3‑2, Figure 3‑2, and McEntire, 1998) for helmet systems used in rotary aircraft, and shall not exceed the limits defined by the Knox Box (Perry, 1998) for helmet systems used in fixed wing aircraft. For rotary wing aircraft, the lateral (ear to ear) cg of the helmet system shall fall within ±0.75 inch (±19 mm) of the mid-sagittal axis regardless of mass. For fixed wing aircraft, the lateral (ear to ear) cg of the helmet system shall be as specified in the Knox Box (Figure 3‑3 and Knox, 1991 and Perry, 1998). The MACH system shall be designed to limit neck loads during a crash and/or ejection sequence.

Figure 3‑1: Vertical of Mass Placement as a Function of head-supported mass

Figure 3‑2: Allowable head-supported mass as a function of longitudinal center of mass placement

McEntire B.J. and Shanahan D.F. “Mass Requirements for Helicopter Aircrew Helmets,” USAARL Report No. 98-14, U.S. Army Aeromedical Research Laboratory, Fort Rucker AL, Jan.1998.

Figure 3‑3: Knox Box Plot Knox F.S., Buhrman J.R., Perry C.E., and Kaleps I. “Interim Head/Neck Criterion,” (non-published consultation report), Air Force Research Laboratory, Wright-Patterson AFB OH, Dec. 1991.

Perry C.E. “Vertical Impact Tests of the Panoramic Night Vision Goggle,” AFRL-HE-WP-SR-1998-0006, Air Force Research Laboratory, Wright-Patterson AFB OH, Nov. 1998.

3.3.5 Anthropometric Accommodation (sizes)

The MACH system shall accommodate the central 96% of the male and female aircrew population with 90% confidence in a maximum of three sizes.

The MACH system will accommodate the central 99% of the male and female aircrew population with 90% confidence in a maximum of five sizes.

3.3.6 Acoustic Dose

The MACH system shall ensure wearers experience acceptable noise levels, technically defined as 100% Acoustic Dose (1.0 Total Daily Exposure (TDE) @ mean -2 Standard Deviations (SD) performance for fit (see APPENDIX C – Acoustic Dose)) for crew positions in 90% defined aircraft.

The MACH system will ensure wearers experience acceptable noise levels, technically defined as 100% Acoustic Dose (1.0 Total Daily Exposure (TDE) @ mean -2 Standard Deviations (SD) performance for fit (see APPENDIX C – Acoustic Dose)) for crew positions in 100% defined aircraft.

3.3.7 Speech intelligibility

An aircrew member wearing the MACH system shall score greater than 80% on the Modified Rhyme Test (MRT) in the laboratory with talker and listener under simulated flight noise conditions.

An aircrew member wearing the MACH system will score greater than 90% on the Modified Rhyme Test (MRT) in the laboratory with talker and listener under simulated flight noise conditions.

3.3.8 In-flight mission reconfiguration

An aircrew member wearing the MACH system and standard flight gloves shall accommodate safe and rapid reconfiguration of helmet mounted devices without removing the MACH system during all mission profiles.

3.3.9 Endurance

96% of the male and female aircrew population with 90% confidence shall be able to wear the MACH system without adjustment or removal for 8 hours.

96% of the male and female aircrew population with 90% confidence shall be able to wear the MACH system without adjustment or removal for 12 hours.

3.3.10 Visor/visual compatibility

The MACH shall have no optical distortion visible in the critical areas of the visor.

The MACH visors’ transmissivity requirements shall be defined by MIL-G-174.

3.3.11 Field of view/regard

The MACH system shall provide a field of view that meets or exceeds the requirements in Table 3‑1 with the central 96% of the male and female aircrew population with 90% confidence.

Table 3‑2: Field of View Requirement

Radial Measurement Angle

(degree) Minimum FOV Angle

(degree)

Radial Measurement Angle

(degree) Minimum FOV Angle

(degree)

3.3.12 Penetration protection

The MACH system shell shall resist a tear length shall be 2 inches (5 cm) over the entire outer surface of the helmet assembly.

3.3.13 Retention

The angular displacement of the MACH system resulting from the simulated crash pulse shall not result in any optical systems, supporting surfaces or frames contacting the facial, eye, or forehead regions of the head form for the central 96% of the male and female aircrew population with 90% confidence.

The MACH system shall be safely retained and remain in its worn position when exposed to either a 600 KEAS ejection, and/or helicopter crash environments for the central 96% of the male and female aircrew population with 90% confidence.

Angular displacement of the head, relative to the angular displacement of the helmet shall withstand a 438.38 pounds (1950 Newton) tension load for 2 minutes and shall not elongate more that 1.5 inches (3.8 cm) from a preload of 24.73 pounds (110 Newton).

3.3.14 Bulk

The MACH and cabling shall not interfere with necessary aircrew mobility, ingress/egress requirements, or the operation of the ejection seats.

3.3.15 Spinal Alignment

The MACH shall enable proper spinal alignment when interfacing with the ejection seat head pads.

3.3.16 Emergency ground egress

The MACH system shall not interfere with the emergency ground egress procedures of the aircrew for the central 96% of the male and female aircrew population with 90% confidence. The aircrew shall not require any additional action to disconnect the helmet system from the aircraft wiring (i.e. disconnect will break away when the aircrew stands up).

3.3.17 Fire safety

The MACH system will provide flame protection as defined in ANSI Z87.1.

3.3.18 Donning

An aircrew member wearing standard flight gloves shall be able to don the Mach system without assistance to the designed and fitted position of ocular alignment in under 30 seconds.

3.3.19 Doffing

An aircrew member wearing standard flight gloves shall be able to doff the Mach system without assistance in less than 10 seconds.

3.3.20 Maxillofacial protection

The MACH system shall shield the maxillofacial region and integrate with the visors and communication systems during all phases of flight (takeoff/landing, airborne/airlift, rescue/recovery missions, etc.) from adverse effects of windblast, airborne debris, and ballistic spall during flight and ground operations.

3.3.21 Valsalva

The MACH system shall not interfere with a one-handed valsalva maneuver performed while wearing standard flight gloves.

3.3.22 Habitability

The MACH system shall allow aircrew members an unimpeded ability to eat and hydrate.

3.3.23 Operability

Direct manipulation of the donned MACH system by the aircrew under operational conditions, shall require only one standard flight gloved hand to easily operate any mechanism (this includes items such as swapping out/adjusting modules, replacing batteries, snapping/unsnapping the quick release chin strap, securing/releasing the oxygen mask, and raising/lowering the helmet visors) for 96% of the male and female aircrew population with 90% confidence.

Direct manipulation of the donned MACH system by the aircrew under operational conditions, will require only one gloved (MOPP-4) hand to easily operate any mechanism (this includes items such as swapping out/adjusting modules, replacing batteries, snapping/unsnapping the quick release chin strap, securing/releasing the oxygen mask, and raising/lowering the helmet visors) for the central 96% of the male and female aircrew population with 90% confidence.

3.3.24 Positive pressure breathing

The MACH system shall allow for the effective use of positive pressure breathing for altitude and G systems for the central 96% of the male and female aircrew population with 90% confidence.

3.3.25 Temperature and moisture control

The MACH system shall incorporate a washable, moisture-wicking, and anti-microbial interface.

3.3.26 Materials and helmet shape

The MACH system materials and helmet shape shall not damage aircraft canopies, windscreens, other transparencies, and structures.

3.3.27 Survival and Rescue Compatibility

The MACH system shall not interfere or degrade the performance of any survival/rescue equipment or procedures.

These will include but are not limited to the following:

· Flotation collar inflation and usage

· Parachute disentanglement procedures

· Universal automatic parachute release

· Helicopter rescue equipment and hoist operation

· Rescue hooks

· Rescue strap (horse collar)

· Forest penetrator

· Emergency Underwater Air Helo Air Breathing Device (HABD)

3.3.28 Chinstrap release time

The aircrew member wearing the MACH system shall be able to release the chinstrap with a single gloved hand in 5 seconds.

3.3.29 Visor lenses

Class I and Class II lenses shall be coated in accordance with MIL-C-83409 and meet all requirements of MIL-DTL-43511 after coating application. In addition, visors will have the capability of carrying additional visors to adapt to changing mission requirements.

3.3.30 MACH wiring connection

The MACH system connections shall operate as designed when performing operations inside the flight envelope.

3.3.31 Head Motion

The MACH system and cable(s) shall allow the wearer a range of head and body motions required by the flight envelope.

3.3.32 Electromagnetic interference (EMI)

EMI requirements shall be in accordance with the applicable requirements of MIL-STD-461.

3.3.33 Windblast resistance

The helmet assembly will meet the following requirements:

3.3.33.1 The helmet shall not crack, split, or sustain physical damage that would cause injury to the aircrew or impair the ability of the helmet to protect the aircrew

3.3.33.2 The helmet and visor assembly shall provide facial protection, prevent foreign objects from entering between the face and visor, provide protection to the eyes, and shall not loosen, break or show any evidence of material failure when exposed to wind blast

3.3.33.3 If the visor rises, the visor assembly shall continue to provide eye protection against windblast and foreign objects of ¼ inch (in any dimension) or greater. Objective: The visor shall remain in place on the face throughout the entire windblast event

3.3.33.4 If any parts of the helmet are lost during the windblast (by chance or by design) and all of the above requirements are still met, those lost parts shall not interfere with the proper operation of the ejection seat or parachute

3.3.34 Ejection

The hazards attributable to the helmet during the ejection acceleration events, canopy penetration phase of the ejection sequence, parachute opening shock, windblast effects, and water entry shall be minimized.

3.3.34.1 Helmet cables shall not interfere with the ejection sequence.

3.3.34.2 All cables and connectors shall be securely attached to the wearer to prevent injury due to flailing during the ejection sequence.

3.3.34.3 The system shall not interfere with successful functioning of the escape system. The ejection seat may be equipped with fixed or deployed pressure sensing pitot tubes.

3.3.34.4 The helmet system shall not interfere with the aircrew tasks related to survival, escape and evasion, and rescue operations.

3.3.35 Bailout

The MACH system shall not interfere with the airframe during bailout procedures.

3.3.36 Parachute deployment and descent

The MACH system shall not interfere with parachute deployment, or the performance of any manually actuated ejection releases, or the performance of any related procedure performed while descending in the parachute. The helmet shall allow the aircrew member to move his head back and forth freely between the risers.

3.3.37 Riser deployment

The MACH system shall not interfere with the riser or parachute release fittings nor interfere with the deployment of the parachute or riser during ejection sequence and parachute deployment. The MACH system contour shall allow risers to pass over it without snagging.

3.3.38 Oxygen mask release

An aircrew member shall be able to disconnect the MBU-20/P oxygen mask from the MACH system with one flight gloved hand within 2 seconds.

3.3.39 Color

The MACH system color scheme shall be as dictated by each service, defined by the CPD.

3.3.40 IR signature

The MACH system IR signature shall be dictated by each service, defined by the CPD.

3.4 Fit.

3.4.1 Fit/wearability

The MACH shall not cause hot spots/pressure points that degrade aircrew performance for 96% of the male and female aircrew population with 90% confidence for a period of 8 hours.

The MACH will not cause hot spots/pressure points that degrade aircrew performance for 100% of aircrew members for a period of 8 hours.

3.5 Communications

3.5.1 Audio Compatibility

The MACH noise attenuation system shall be compatible with all aircraft systems and shall not impede audible aircraft warning/caution systems, night vision equipment, weapons system employment, or decrease accuracy of helmet-mounted cueing devices.

3.5.2 Internal Communications Systems (ICS)

The MACH noise attenuation system shall be compatible with all current and planned aircraft ICS.

The MACH will automatically match impedance to maximize audio performance.

3.5.3 Audio performance

The MACH system shall provide broadband audio output with distortion not exceeding 10%, Sound Pressure Level (SPL) shall be within 3 db between both ears, and electrical polarity shall be matched across both ears.

3.5.4 Volume control

Adjustment of the aircraft ICS volume control shall result in a corresponding volume change at the ear.

3.5.5 3-D Audio The MACH system shall be capable of accepting 3-D audio cueing for radio communication and threat and targeting information.

3.5.6 External Audio

The MACH system shall be capable of providing an external audio capability that allows dismounted aircrew the ability to hear the external environment while wearing the MACH system.

3.5.7 Communication devices

The MACH system shall be compatible with or replace current communications devices designed for use with aircrew helmets and oxygen masks.

3.5.8 Boom microphone

The MACH system shall be compatible with, or provide a boom microphone.

The MACH system will provide a flexible boom microphone.

3.6 Aircrew Helmet Noise Reduction (AHNR)

The requirements specified in Section 3.6 shall be mandatory for only MACH system requiring AHNR.

3.6.1 Fail safe design

AHNR shall incorporate fail-safe modes to allow continued communications upon system/battery failure.

3.6.2 Feedback

AHNR shall automatically turn off active components in the event of uncontrolled feedback oscillation or control instability.

3.6.3 Sound pressure level (SPL) spikes

Active systems shall continue to operate after extreme SPL spikes of 140 dB without system degradation.

3.6.4 On/off switch

AHNR shall provide an on/off switch and controller that is readily accessible to the aircrew member during flight, low profile, resistant to inadvertent activation and deactivation, and enables the aircrew member to select the mode with a single gloved hand. AHNR on/off switch shall only disable AHNR function and not other communications.

3.6.5 Batteries

If batteries are required, they will be readily available, Commercial off the Shelf (COTS), and replaceable by the aircrew member during the flight.

3.6.6 Battery life

AHNR battery life shall operate for 10 hours without requiring battery replacement.

AHNR battery life will operate for 20 hours without requiring battery replacement.

3.6.7 Battery life indicator

AHNR shall provide a non-distracting, visible means for the aircrew member to determine the percentage of remaining battery life.

3.7 Neck protection

3.7.1 Neck tension limits

The maximum acceptable neck tension (lifting force) limits measured at the occipital condyles (C0-C1, upper neck) and cervical vertebrae (C7-T1, lower neck) are defined in Table 3‑3 (use linear interpolation for intermediate values in force and time duration). These limits represent the maximum allowable load that can be sustained for a given duration.

Table 3‑3 Neck tension force and duration limits for a given occupant size

Small Female Hybrid

III Type Manikin

(103 to 135 lbs) Mid-Size Male Hybrid

III Type Manikin

(136 to 199 lbs) Large Male Hybrid

III Type Manikin

(200 to 245 lbs)

Duration

(ms) Tension at C0-C1 & C7-T1

(lbs) Duration

(ms) Tension at C0-C1 & C7-T1

(lbs) Duration

(ms) Tension at C0-C1 & C7-T1

(lbs)

3.7.2 Neck compression and shear force limits

The maximum acceptable cervical compression and shear force limits are defined in Table 3‑4 (use linear interpolation for intermediate values in force and time duration).

Table 3‑4 Neck compression and shear force limits for a given occupant size

Small Female Hybrid

III Type Manikin

(103 to 135 lbs) Mid-Size Male Hybrid

III Type Manikin (136 to 199 lbs) Large Male Hybrid

III Type Manikin

(200 to 245 lbs)

Duration

(ms) Compression at C0-C1 & C7-T1

(lbs) Duration

(ms) Compression at C0-C1 & C7-T1

(lbs) Duration

(ms) Compression at C0-C1 & C7-T1

(lbs)

Duration

(ms) Resultant Shear at C0-C1

(lbs) Duration

(ms) Resultant Shear at C0-C1

(lbs) Duration

(ms) Resultant Shear at C0-C1

(lbs)

Duration

(ms) Resultant Shear at C7-T1

(lbs) Duration

(ms) Resultant Shear at C7-T1

(lbs) Duration

(ms) Resultant Shear at C7-T1

(lbs)

3.7.3 Combined Neck Moment and Load Limits

The maximum combined-cervical-force-and-moment limit, expressed as Neck Injury Criteria (Nij), is 0.5, as measured at the occipital condyles (C0-C1). The maximum Nij as measured at the cervical vertebrae (C7-T1) is 1.5. Nij is not applied for pure tension or compression.

3.7.4 Neck X and Z Moment Limits

To evaluate neck lateral bending (Mx) and rotation (Mz), the Neck Moment Index (NMI) will be calculated. The maximum allowable NMIx, is 0.5, as measured at the occipital condyles (C0-C1) and 1.5 as measured at the cervical vertebrae (C7-T1). The maximum allowable NMIz, is 0.5, as measured at the occipital condyles (C0-C1) and 1.0 as measured at the cervical vertebrae (C7-T1).

3.8 Environmental considerations

3.8.1 Atmospheric Pressure change

The MACH system shall not increase the risk of aircrew injury throughout the range of atmospheric pressure changes experienced during flight.

3.8.2 Altitude protection

The MACH system shall allow users to safely operate at altitudes up to the maximum operational cabin altitude of aircraft listed in APPENDIX B – Aircraft Compatibility.

3.8.3 Electromagnetic Interference/Electromagnetic Compatibility (EMI/EMC) The MACH system shall not emit electromagnetic energy that exceeds the limits of MIL-STD-461 and ADS-37A-PRF as it applies to Mission Critical Equipment or be degraded by electronic emissions in its operational environment.

3.8.4 Electrostatic discharge (ESD)

The MACH system shall meet the requirements of this specification after being exposed to an electrostatic discharge (ESD) pulse of 4 kilovolts for 1 to 3 nanoseconds or a current flow of 5 amps.

3.8.5 Storage Temperature

The MACH system shall meet the requirements of this specification after storage at any temperature in the range of -80°F to 185°F (-62(C to +85(C).

3.8.6 Operational Temperature

The MACH system shall meet the requirements of this specification over the temperature range of -65°F to 160°F (-54°C to +71(C).

3.8.7 Temperature, altitude, and humidity

The MACH system shall meet the requirements of this specification after the combined effects of temperature, altitude, and humidity.

3.8.8 Temperature shock

The MACH system shall meet the requirements of this specification after exposure to sudden changes in the thermal environment from 165°F to -65°F (74°C to -54°C).

The MACH system shall meet the requirements of this specification after exposure to sudden changes in the thermal environment from -65°F to 165°F (-54°C to 74°C).

3.8.9 Salt fog

The MACH system shall meet the requirements of this specification during and after exposure to moisture with salt.

3.8.10 Humidity

The MACH system shall meet the requirements of this specification in relative humidity levels of 95% relative humidity.

3.8.11 Blowing Dust

The MACH system shall meet the requirements of this specification during and after exposure to blowing dust.

3.8.12 Blowing Sand

The MACH system shall meet the requirements of this specification during and after exposure to blowing sand.

3.8.13 Solar Radiation

The MACH system shall meet the requirements of this specification during and after exposure to solar radiation.

3.8.14 Rain

The MACH system shall meet the requirements of this specification during and after exposure to rain rates of 4 inches (10.16 centimeters) per hour and 40 mile per hour winds for a period of 30 minutes.

3.8.15 Fungus

The MACH system shall be fungus resistant.

3.8.16 Transit Drop

The MACH system shall be free of defects (i.e., chips, scrapes) and shall operate after exposure to transit drops.

3.8.17 Rapid decompression

The MACH system shall meet the requirements of this specification after being subjected to a rapid decompression from 8,000 feet to 60,000 feet over a duration of 10 seconds.

3.8.18 Explosive Decompression

The MACH system shall meet the requirements of this specification after being subjected to an explosive decompression from 8,000 feet to 60,000 feet over a duration of 0.1 seconds.

3.8.19 Immersion

The MACH system shall meet the requirements of this specification immediately upon removal from immersion in salt water or fresh water to 32.8 feet (10 meters) for 15 minutes and 3.28 feet (1 meter) for 24 hours.

3.8.20 Explosive atmosphere

The MACH system shall operate in explosive atmospheres without causing an explosion.

3.8.21 Vibration curves

The MACH system shall meet the requirements of this specification after exposure to vibrations representing jet and propeller aircraft.

3.8.22 Acceleration

The MACH system shall meet the requirements of this specification after exposure to accelerations of 35 Gs forward, 25 Gs aft, 25 Gs up, 25 Gs down, and 25 Gs left and right. Directions are defined as if the helmet is worn in a sitting position in an ACES II/III survival kit configuration, with forward direction facing the nose of the aircraft.

3.8.23 Shock

The MACH system performance shall meet the requirements of this specification after normal hard landing or other mechanical shocks encountered in servicing and normally associated with air, land, or sea transport of the aircraft.

3.8.24 Vibration

The MACH system shall meet the requirements of this specification after exposure to vibration.

3.8.25 Nuclear, Biological, and Chemical Survivability

The MACH assembly will be serviceable and operable in a nuclear, biological, and chemical environment.

4.0 VERIFICATION

4.1 Scope

This section specifies the verification requirements to qualify MACH in meeting all of the requirements in section 3. All section 3 requirements shall be verified in a government approved testing facility.

4.2 First article testing

First article testing, as required by contract shall consist of the first article tests shown in Table 4‑1. MACH shall pass all required first article tests in Table 4‑1to be considered acceptable.

4.3 Production lot testing

Production lot testing, as required by contract, shall consist of the production lot tests called out in Table 4‑1. Sample MACH systems shall be selected at random from each lot on the same production purchase order, in the quantities specified below, and subjected to the examination of the product per the tests called out in Table 4‑1. MACH shall pass all required production lot tests in Table 4‑1 top be considered acceptable. Failure to meet any of the specified requirements for any one MACH system shall be considered cause for rejection of the lot.

A minimum of 5 MACH systems from each lot up to 250 A minimum of 10 MACH systems from each lot of 251-500 A minimum of 1 for every 50 MACH systems from each lot over 501

4.4 Functionality check

A functionality check shall consist of the functionality check tests called out in Table 4‑1. The MACH system shall pass all required functionality check test in Table 4‑1 to be considered acceptable. A functionality check shall be required on all units to be delivered, in addition to functionality check requirements otherwise contained in this performance specification document.

4.5 Methods

One or more of the following methods shall be used for verification:

(Note: X signifies a requirement for testing, N/A signifies not applicable)

Table 4‑1: Verification Matrix

3.2 Design and Construction

3.3 Performance characteristics

3.4 Fit

3.5 Communications

3.6 Active Helmet Noise Reduction (AHNR)

3.7 Neck Protection

3.8 Environmental Considerations