Atch2_-_IACP_AS_Journal_Paper.pdf

11 http://jaspo.csd.disa.mil AS Journal 14 / SUMMER by Mark Robeson

The US Army’s Aviation Development Directorate (ADD)–Aviation Applied Technology Directorate (AATD) executed a project to evaluate and select technology for enhanced aircraft and crew/occupant protection, improved durability, and reduced environmental vulnerability in an integrated, platform-level prototype without impacting mission performance. In the project, entitled Integrated Aircraft and Crew Protection (IACP), threats to aircraft and occupants were defined, vulnerability to those threats was quantified, and technologies addressing those threats were identified. Prototypes were defined based on production Army rotorcraft with mature technologies added as independent point solutions. Less mature technology solutions were also identified, traded at the system level, and integrated into weight-constrained, system-level prototypes. The differences between these production platforms, the prototypes with independent point solutions, and the prototypes with integrated solutions were quan-tified in terms of project metrics. In the three cases considered in IACP, the integrated approach yielded significantly larger improvements than did the approach using independent solutions.

INTEGRATED AIRCRAFT

AND CREW PROTECTION

INTRODUCTION

High operational tempo requirements, asymmetric threats, and harsh operating environments all impact the operational availability of Army rotary wing aviation assets. Current qualification methodology is intolerant of any form of structural damage, and while this approach provides high assurance of structural integrity and mission reliability, it negatively impacts operational availabil-ity. In addition, crew, passengers, and aviation platforms are vulnerable to conventional threats, such as small arms fire. Hard landings and crash landings cause damage sufficient to make the platform unavailable for operations.

Aircraft damaged in flight cannot reduce loads to damaged areas to limit propaga-tion, and rotor systems cannot adapt to deal with partial blade loss or to effectively manage energy during an unpowered descent.

The addition of operational availability to the traditional survivability components of susceptibility and vulnerability has resulted in a paradigm called total survivability (see Figure 1). Technology is available to increase the durability of the platform, and to reduce the vulnerability of the crew and passengers to hostile threats and crash injury or death. These vulnerability reduction technologies can reside in the airframe structures, rotor system, vehicle management system, and vehicle subsystems for overall system benefits, which include increased operational availability. These technolo-gies enable a platform to avoid/absorb damage, avoid destruction, and return to service. An increase in total survivability

Figure 1 Total Survivability Chain

AS Journal 14 / SUMMER http://jaspo.csd.disa.mil 12 means improved aircraft/crew protection and a more operationally available aircraft.

APPROACH

To explore the benefits of increased total survivability afforded by vulnerability reduction technologies, the US Army’s ADD–AATD executed a project entitled IACP. [1,2] Through multiple contracts with industry, IACP focused on technol-ogy evaluation and selection targeting future demonstration of enhanced aircraft and crew/occupant protection, improved battlefield durability, and reduced environmental vulnerability in an integrated, platform-level prototype without a deleterious effect on mission performance. For the technology spectrum under consideration in IACP, the constraint on mission performance was effectively a prohibition on increasing platform weight. A key objective of IACP was to illustrate the contrast in how an integrated, system-level approach provides greater benefits than a feder-ated (assembling independent point solutions) approach to using technology to enhance platform total survivability (see Figure 2).

The federated approach considered in IACP consists of combining independent, typically mature, technology upgrades to a platform. This maturity is typically reflected by technology readiness levels (TRLs) of 8 or 9. [3] This federated approach is often seen in upgrades to Department of Defense aircraft as executed by program management offices in response to perceived urgent needs, and often results in increased platform weight.

On the other hand, as explored in IACP, the integrated approach consists of fully blending, both with each other and at the system level, technology upgrades into a platform. To support this broad integration and offer greater potential benefits, less mature (typically TRL 4-7) technologies were considered in the integrated approach of IACP.

In executing IACP, a wide spectrum of threats to platforms and occupants were defined, vulnerability to those threats was quantified, and technologies to counter or address those threats were identified. Federated prototypes were defined based on current production Army rotorcraft with mature (TRL 8-9) technologies added on as independent point solutions. Less mature (TRL 4-7) technology solutions were identified, traded at the system level, and fully integrated into weight-constrained, system-level integrated prototypes based on current production Army rotorcraft.

The differences between these produc-tion platforms, the federated prototypes, and the integrated prototypes were quantified in terms of project metrics related to total survivability.

Figure 2 IACP Approaches

13 http://jaspo.csd.disa.mil AS Journal 14 / SUMMER

Three cases, corresponding to different current production Army rotorcraft (unspecified herein) of different mission types and subject to different threats, were considered in IACP.

RESULTS

Case 1

The IACP metrics for Case 1 initially used included weight, a system hardening index, a crashworthiness index, and operational availability. The system hardening index was a function of probability of kill given a hit for various threats, such as small arms fire, the crashworthiness index was based on the Full Spectrum Crashworthiness Criteria [4], and operational availability repre-sented a percentage of time that the aircraft was available for mission use. As part of the technology trade study and benefits quantification process, a composite IACP Index was defined as follows:

IACP Index = (Normalized System Hardening Index)

* (Normalized Crashworthiness Index)

* (Normalized Operational Availability)

Weight and the composite IACP Index were then used as the metrics for Case 1.

For the federated prototype, mature technologies incorporated were transpar-ent canopy armor, crashworthy crew seats, a cockpit airbag system, composite airframe structure, and structural usage monitoring technology.

For the integrated prototype, extensive trade studies were carried out to determine the most effective solution integrating TRL 4-7 technologies, both with each other and into the platform at a system level. The goal in the trade studies was maximizing the IACP index without impacting platform mission performance through a weight increase.

The resultant integrated technology solution suite included advanced transparent armor, a comprehensive crash predictive and subsystem control system, an inflatable restraint system, crashworthy energy-absorbing crew seats, composite drive shafts, and extensive composite fuselage structure.

These TRL 4-7 technologies provided the opportunity for a more thorough integration as compared to corresponding technologies used in the federated prototype.

The weight and IACP Index values for the Case 1 federated prototype and inte-grated prototype were determined and compared with corresponding values for the Case 1 production platform (see Figure 3). While the federated prototype provided an 11% improvement in IACP Index accompanied by a slight weight increase, the integrated approach yielded a 28% improvement with no weight penalty (a slight weight decrease, actually).

Case 2

The IACP metrics for Case 2 were the same as those used for Case 1—weight and the composite IACP Index.

Mature technologies incorporated for the Case 2 federated prototype were transparent canopy armor, crashworthy crew and troop seats, a cockpit airbag system, high-energy crashworthy landing gear, composite airframe structure, structural usage monitoring technology, rotor blade erosion control technology, an advanced drive lubrication system, and ballistically hardened swashplate actuators.

As before, extensive technology trade studies were carried out to define an integrated prototype with the most effective solution, integrating TRL 4-7 technologies both with each other and into the platform at a system level. The resultant technology solution suite for Case 2 included advanced transparent armor, crashworthy crew seats, crash-worthy troop seats, fuel tank reconfiguration, advanced composite structure, composite drive shafts, ballistically hardened swashplate actuators, rotor blade erosion control technology, rotor track & balance/ vibration technology, and advanced flight

Production Platform

Federated Prototype

Integrated Prototype

0.00

0.25

0.50

0.75

1.00

1.25

1.50

Weight

IACP

Index

Figure 3 Case 1 Results

Production Platform

Federated Prototype

Integrated Prototype

0.00

0.50

1.00

1.50

2.00

Weight

IACP

Index

Figure 4 Case 2 Results

AS Journal 14 / SUMMER http://jaspo.csd.disa.mil 14 controls. These technologies also offered increased opportunity for integration as compared to the corresponding mature technologies used in the federated prototype.

The weight and IACP Index values for the Case 2 federated prototype and inte-grated prototype were calculated and compared with corresponding values for the Case 2 production platform (see Figure 4). In this case, the federated prototype provided a 68% improvement in IACP Index at a weight penalty of about 5%, but the integrated approach yielded a 95% improvement with no weight penalty (as before, a slight weight decrease, actually).

Case 3

The IACP metrics for Case 3 included weight, aircraft survivability, occupant survivability, and operational availability.

For the Case 3 federated prototype, the mature technologies incorporated were upgraded rotor damper technology, fly-by-wire flight controls, composite fuselage skins, a dry bay fire extinguish-ing system, a cabin ballistic armor system, and a cockpit airbag system.

As was done in the previous cases, the integrated prototype was defined through extensive trade studies carried out to determine the most effective solution, integrating TRL 4-7 technologies, both with each other and into the platform at a system level. The Case 3 integrated technology solution suite included extensive composite fuselage structure, vibration suppression, structural health sensors, advanced flight controls, an external airbag system, fuel tank reconfiguration, ullage inerting technol-ogy, rotor blade erosion control technology, and advanced component manufacturing techniques, in addition to a few of the mature technologies that were used in the federated prototype.

As before, the TRL 4-7 technologies offered increased opportunity for integration as compared to the corresponding mature technologies used in the federated prototype.

The weight, aircraft survivability, occupant survivability, and operational availability metric values for the Case 3 federated prototype and integrated prototype were determined and com-pared with corresponding values for the production platform (see Figure 5). While the federated prototype provided 2%, 6%, and 1% improvements in aircraft survivability, occupant survivability, and operational availability, respectively, the integrated prototype yielded correspond-ing improvements of 12%, 14%, and 3% with essentially no weight penalty.

Production Platform

Federated Prototype

Integrated Prototype

0.00

0.95

1.00

1.05

1.10

1.15

Weight

Aircraft Survivability

Occupant Survivability

Operational Availability

Figure 5 Case 3 Results

CONCLUSIONS

In IACP, technology was evaluated and selected for enhanced aircraft and crew/ occupant protection, improved durability, and reduced environmental vulnerability in an integrated, platform-level prototype without impacting performance through increased weight. Threats were defined, vulnerabilities quantified, and countering technologies identified. Federated prototypes were defined based on production rotorcraft with mature technologies added as independent point solutions. Less mature technology solutions were also identified, traded at the system level, and integrated into weight-constrained, system-level integrated prototypes. The differences between these production platforms, the federated prototypes, and the integrated prototypes were quantified in terms of metrics. Three cases were investigated to show that the integrated approach yielded significantly larger improvements than did the federated approach, in terms of metrics based on crashworthiness, system hardening, aircraft survivability, occupant survivability, and operational availability. The cases corresponded to aircraft of different mission types, so the quantified improvements could not be compared on a technology-by-technology basis.

The compelling total survivability benefits yielded by the integrated approach have led to this approach being implemented in multiple, ongoing ADD–AATD technology development efforts. [5,6] The fully integrated approach offers tremen-dous benefits to technology developers, Department of Defense Program Management Offices, and ultimately the soldier.

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ACKNOWLEDGEMENTS

This research was funded by ADD–AATD under Contracts W911W6-10-C-0041 and W911W6-10-C-0042. The US Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation thereon. The views and conclusions contained in this document are those of the author and should not be interpreted as representing the official policies, either expressed or implied, of ADD–AATD or the US Government.

INTEGRATED AIRCRAFT AND

CREW PROTECTION

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About the Author Dr. Mark E. Robeson is an aerospace engineer with the US Army’s ADD–AATD at Fort Eustis, VA. He has over 23 years of research and development experience with advanced aircraft structures. His current areas of specialization include advanced composite airframe structures, structural contributions to vulnerability reduction, and multifunctional structures. Dr. Robeson is the Army co-chair of the Structures & Materials Committee of the Joint Aircraft Survivability Program Vulnerability Reduction Subgroup. He may be reached at mark.e.robeson.civ@mail.mil.

REFERENCES

[1] Integrated Aircraft and Crew Protection, US Army RDECOM Technical Report TR 12-D-02, Final Report for ADD–AATD Contract W911W6- 10-C-0041, December 2011.

[2] Integrated Aircraft and Crew Protection, US Army RDECOM Technical Report TR 12-D-03, Final Report for ADD–AATD Contract W911W6- 10-C-0042, December 2011.

[3] Technology Readiness Assessment (TRA) Guidance, Assistant Secretary of Defense for Research and Engineering, April 2011.

[4] Full Spectrum Crashworthiness Criteria for Rotorcraft, US Army RDECOM Technical Report TR 12-D-12, ADD–AATD, December 2011.

[5] Combat Tempered Platform Demonstration, ADD–AATD Agreement W911W6-12-2-0005, Effective June 2012.

[6] Combat Tempered Aft Fuselage, Phase 3 under ADD–AATD Agreement W911W6-11-2-0014 (Rotorcraft Durability and Damage Tolerance), Effective September 2012.