Chapter IV. Technology Development
Army Science and Technology Master Plan (ASTMP 1997)


D. AIR AND SPACE VEHICLES

1. Scope

DoD has assigned the Army as the lead for Rotary Wing science and technology in the areas of aeromechanics, flight control, structures, and subsystems supporting development of military rotary-wing air vehicles. The Aviation community is aligning all planning documents to coincide with the DoD (DDR&E) requirement to establish technology objectives, identify technical barriers, and establish milestones for achievement. Programs will be tracked by OSD to these detailed plans. The rotary-wing vehicle sub-area is divided into the following four technology efforts: aeromechanics, flight control, subsystems, and structures. The Goals objectives for each technology effort and the time frames for accomplishing them have been set in accordance with the DDR&E document entitled "Rotary Wing Vehicle (RWV) Technology Development Approach (TDA)" and are summarized below.

2. Rationale

Rotorcraft have become critically important members of the combined arms team, bringing a degree of deployability, mobility, lethality, and sustainability to the battlefield commander not available with other systems. With the continuing decrease in fiscal resources, affordability and dual use have become increasingly important in shaping Army Aviation's S&T strategy. Technology must support solutions to real world problems, avoiding work which does not provide leap ahead improvements in system capabilities. This is important to the sustainment of current systems, as the fielding of new systems is being pushed further to the "out years." From a dual use perspective, civilian and military Rotorcraft communities have a mutual stake in all but few areas of rotorcraft technology research, such as the work being done to reduce the vulnerability of rotor craft in battlefield environments. Improvements in handling qualities, vibration, and sound level reductions are equally important to civil and military rotorcraft operators. It is estimated that 95 percent of the DoD investment in rotary-wing technology has civil application.

3. Technology Sub-Areas

a. Aeromechanics

Goals and Time Frames

Work in aeromechanics technology addresses efforts in multidisciplinary phenomena including acoustics, aerodynamic performance, rotor loads, vibration, maneuverability, and aeroelastic stability. Aeromechanics science and technology seeks to improve the performance of rotor craft while reducing the noise, vibrations, and loads inherent to helicopter operation. Efforts are focused on refining analytical prediction methods and testing capabilities, on improving the versatility and efficiency of modeling advanced rotorcraft, and on achieving dramatic advances through concept applications. Attaining the goal of a "jet-smooth ride" in helicopters will greatly enhance public acceptance, along with providing quieter rotorcraft. The goals set at component level are focused on reducing vibratory loads 33 percent to 53 percent, reducing vehicle adverse aerodynamic forces 10 percent to 20 percent, increasing the maximum blade loading 15 percent to 25 percent, increasing the rotor aerodynamic efficiency 5 percent to 10 percent, reducing acoustic radiation 4dB to 7dB, increasing rotor inherent lag damping 50 percent to 100 percent, and increasing the accuracy of aeromechanics prediction effectiveness 74 percent to 84 percent. The span of time set for accomplishing these goals runs from the present through the year 2012 with an intermediate milestone at year 2005. These goals and associated milestone are in tabular form following.

Major Technical Challenges

Approach - Investigate the influence of airfoil profile on development of dynamic stall in compressible flow; quantify influence of compressibility on flow control techniques; develop innovative ways to use smart materials for flow control and structural response.

Approach - Enhance flowfield visual techniques using Doppler Global Velocimetry; study various models' rotor wake and fuselage pressure distributions using Isolated Rotor Test System. Calculate adverse forces using validated Computational Fluid Dynamics (CFD) and comprehensive analyses.

Approach - Develop high dynamic-lift stall-free airfoils with multi-element concepts such as slat, slots, variable leading edges, or boundary layer controls.

Approach - Develop reliable, validated engineering computational codes based on full-potential, vortex embedding techniques to predict rotor performance and loads in all flight regimes.

Approach - Develop verified CFD code to predict wake geometry, airloads, and performance for rotor blades, in particular blade-vortex interaction regimes and the resulting aeroacoustics.

Approach - Investigate kinematic and smart structures couplings that result in less dependency on separate damping devices. Utilize parametric rotor testing to substantiate prediction fidelity of marginally damped rotor configurations.

Approach - Prediction effectiveness attributes defined and composed against data to determine element accuracy. Metrics for improvement shall include quantifiable subelement effectiveness and system integration value, such as in a product and process development simulation.

b. Flight Control

Goals and Time Frames

Flight control technology defines the aircraft flying qualities and pilot interface to achieve desired handling qualities in critical mission tasks, synthesizes control laws that will facilitate a particular configuration achieving a desired set of flying qualities, and integrates advanced pilotage systems to the aircraft. Helicopters are inherently unstable, nonlinear, and highly cross coupled. As with many other technologies, the revolution in the power and miniaturization of computers holds tremendous promise in this field, permitting realization of the full potential of the rotorcraft's performance envelope and maintenance of mission performance in poor weather and at night.

Through the integration of the vehicle's flight control system with weapons fire control, a 60 percent improvement in the pointing accuracy by the turn of the century will permit increased use of low-cost, unguided rockets as precision munitions. Further, a significant development cost driver is being assessed. Objectives have been set to improve external load handling qualities at night and with partial actuator authority, in each case from a Cooper Harper Pilot's Rating (CHPR) of 4 to 3; to reduce the probability of encountering degraded handling qualities due to flight control system failures 50 percent to 90 percent; to improve the weapon platform pointing accuracy techniques 60 percent to 80 percent; to increase exploitable agility and maneuverability 10 percent to 15 percent; and to reduce flight control system flight test development time from 30 percent to 50 percent. The time frame for accomplishing these goals spans from the present through year 2012, with an intermediate milestone at year 2005. These goals are quantified in the table below.

Major Technical Challenges

Approach - Use piloted simulation and flight test to investigate handling qualities requirements for external loads. Develop appropriate criteria for poor weather and darkness. Extend efforts to address high speed flight and loads with significant aerodynamic interactions.

Approach - Use analysis and piloted simulation to develop techniques for protecting the pilot from loss of control and avoiding catastrophic failures or reduced fatigue life. Validate critical concepts in-flight using variable stability helicopter.

Approach - Improve mathematical modeling and simulation fidelity so that new aircraft actually fly as designed. Improve techniques for updating math models and control laws to minimize time required to diagnose and eliminate deficiencies. For advanced fly-by-wire flight control systems develop simpler redundancy management and software V&V techniques so that time for making changes can be reduced.

Approach - Develop a viable Integrated Fire and Flight Control (IFFC) system architecture; conduct manned full-mission simulation, ground demonstration of hardware and software for airborne vehicle application; and flight test demonstration of the IFFC concept.

c. Structures

Goals and Time Frames

Focusing on Integrated Product and Process Development (IPPD), rotary-wing structures science and technology aims at improving aircraft structural performance while reducing both acquisition and operating costs of the existing fleet of aircraft and future systems. The technical feasibility of load synthesis methods (holometrics, et al.) and regime/flight condition recognition algorithms as means to predicting the actual loads experienced in-flight has been demonstrated; further improvements to the reliability of these methods will enhance the safety, performance, and cost-effectiveness of rotorcraft. "Virtual prototyping" of systems to optimize the structural design for efficiency and performance will remove a large portion of the risk in exploring new concepts and rapidly move the most promising concepts to production.

Objectives have been established for the 2005 and 2012 timeframes, relating to increasing the accuracy of in-flight cumulative fatigue damage prediction techniques by 95 percent and 98 percent; reducing the production labor hours per pound for composite structures by 25 percent and 40 percent; increasing airframe structural efficiency by 15 percent and 25 percent; increasing the displacement capability of smart materials actuators by 300 percent and 500 percent; and increasing the accuracy of structural loads prediction by 75 percent and 85 percent.

Breakthroughs in these areas will effect improvements in maintenance and production costs, as well as reduce the empty weight fraction of the airframe while increasing durability, performance, and ride comfort of rotorcraft. Example: Validate stress and failure analysis based on inspection model for structural integrity.

Major Technical Challenges

Approach - Develop and refine flight regime/flight condition recognition and load synthesis algorithms based on aircraft state parameters and other measured loads. Conduct bench and flight test evaluations on instrumented aircraft to validate accuracy. Collect operational data over a period of 1 to 3 years to validate the reliability of the flight data recorder and the algorithms.

Approach - Develop and refine regime/flight condition recognition algorithms based on aircraft state parameters. Conduct bench and flight test evaluations on instrumented aircraft to validate accuracy. Collect operational data over a period of 1 to 3 years to validate the reliability of the flight data recorder and regime/flight condition recognition algorithms.

Approach - Design and fabricate representative components to demonstrate advanced manufacturing technologies and tooling techniques. Investigate manufacturing process simulation models through cure prediction, cure cycle optimization, and structural testing to validate cure cycle optimization and structural efficiency. Demonstrate the use of embedded sensors for adaptive control of the cure cycle through fabrication and test of representative rotorcraft components. Develop and demonstrate the use of nondestructive inspection techniques for determining the integrity of bonded structures.

Approach - Develop innovative structural design configurations using advanced materials tailorable for structural efficiency. Develop and demonstrate representative rotorcraft structures using IPPD to optimally meet multidisciplinary design requirements that include cost, weight, performance, and reliability. Fabricate structural components in sufficient quantities to validate the quality, manufacturing repeatability, structural efficiency, and recurring cost. Develop and demonstrate advanced braiding and weaving equipment and methods to minimize fiber breakage and marcelling. Fabricate structural preforms and incorporate these preforms into tailored structural fittings and components to validate the structural efficiency and recurring costs.

Approach - Investigate the force, displacement, and poor requirements of new and emerging smart materials for advanced rotor actuation methods; conduct trade-off analyses; demonstrate smart materials applications to rotor actuators through laboratory testing in a dynamic environment.

Approach - Develop and validate enhanced comprehensive methods that incorporate multidisciplinary technology based on finite element techniques that include composite structures modeling, specifically concentrating on the rotor system loads and aeroelastic stability analysis. Develop and validate reliable finite element analysis modeling and simulation techniques that include large strain effects required to model the energy absorbing characteristics of crushable composite structures.

d. Subsystems

Goals and Time Frames

Rotary-wing Vehicle subsystems encompass a broad range of science and technology topics related to the support, sustainment, and survivability of increasingly complex aircraft systems, and to the unique problems associated with the application of high performance weapons on rotorcraft. In addition to addressing affordability issues for operation and support (O&S) costs, this area also encompasses the extension of the useful life of weapon systems through upgrading armament and other mission equipment. Five key technological objectives have been established for the 2005 and 2012 timeframes: increasing the probability of detecting incipient mechanical component failures to 90 percent and 95 percent, increasing hardening to threats by 20 percent and 35 percent, reducing radar cross section (RCS) by 25 percent and 40 percent, reducing infrared (IR) signature by 35 percent and 50 percent, and reducing visual and electro-optical signature by 35 percent and 55 percent. Once these goals are attained, aircraft will be able to operate with fewer maintenance hours per flight hour, and to operate safely and effectively in a hostile environment.

Major Technical Challenges

Approach - Conduct computer modeling from signature prediction to battlefield simulations. Conduct laboratory and flight testing of cost-effective attenuating materials and design concepts that will reduce IR, RCS, acoustic, visual, and electro-optic emissions from rotorcraft.

Approach - Conduct computer modeling of hardening concepts to provide reduced probability of kill across the full spectrum of known threats, as well as crash impacts. Conduct demonstrations of components and of the integration of lightweight armor, DEW, and NBC hardening that balance cost, weight, and effectiveness.

Approach - Develop a quantified database of the performance of impending component failures. Conduct laboratory and field testing of advanced sensors and monitoring systems.

4. Roadmap of Technology Objectives

The roadmap of technology objectives for Air and Space Vehicles is shown in Table IV-D-1, below.

 

Table IV-D-1. Technical Objectives for Air and Space Vehicles

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Table IV-D-1. Technical Objectives for Air and Space Vehicles (Continued)

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