SCIENTIFIC AND TECHNICAL AEROSPACE REPORTS
A Biweekly Publication of the National Aeronautics and Space Administration
VOLUME 44, ISSUE 14 - JULY 18, 2006
05 AIRCRAFT DESIGN, TESTING AND PERFORMANCE
Includes all stages of design of aircraft and aircraft structures and systems.
Also includes aircraft testing, performance and evaluation, and aircraft and flight simulation technology.
For related information see also 18 Spacecraft Design, Testing and Performance and 39 Structural Mechanics.
For land transportation vehicles see 85 Technology Utilization and Surface Transportation.
20060019360 Illinois Univ., Urbana, IL USA
Pilot Dependence on Imperfect Diagnostic Automation in Simulated UAV Flights: An Attentional Visual Scanning Analysis
Wickens, Christopher; Dixon, Stephen; Goh, Juliana; Hammer, Ben; Jan 2005; 7 pp.; In English; Original contains color illustrations Contract(s)/Grant(s): MAD-6021.000-01 Report No.(s): AD-A446167; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA446167; Avail.: CASI: A02, Hardcopy
An unmanned air vehicle (UAV) simulation was designed to reveal the effects of imperfectly reliable diagnostic automation a monitor of system health parameters on pilot attention, as the latter was assessed via visual scanning. Four groups of participants flew a series of legs under different automation conditions: a baseline (no automation) control, and automation which was either 100% reliable, 60% reliable with a low-threshold bias to produce false alerts, and 60% reliable with a high threshold to produce misses. A high workload mission completion task and ground surveillance task were simultaneously imposed. Consistent with the reliance-compliance model of imperfect automation developed by Meyer (2001), miss-prone automation removed visual attention from the surveillance task, while FA-prone automation delayed the alert-driven attention shift to the system monitoring task. DTIC
Display Devices; Drone Vehicles; Pilots; Visual Perception
20060019388 Michigan Univ., Ann Arbor, MI USA
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Modified Generalized-Alpha Method for Integrating Governing Equations of Very Flexible Aircraft
Shearer, Christopher M; Cesnik, Carlos E S; Apr 14, 2006; 22 pp.; In English Report No.(s): AD-A446258; AFIT-CI-04-1764; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA446258; Avail.: CASI: A03, Hardcopy
This paper focuses on the time integration of the nonlinear EOM associated with a very flexible aircraft in flight. Variousintegration methods exist for linear structural dynamics problems. However, a review of the literature indicates little material associated with the integration of nonlinear structural EOM of relatively large order. Moreover, for the problem of simulation of very flexible aircraft, a combination of flight dynamics and aeroelastic degrees of freedom must be integrated concurrently.A modified first and second order Generalized-alpha Method along with an implicit sub-literation scheme were deve loped. It has shown good agreement with predictor/corrector integration schemes for a reduced set of linear EOM. The method is also seen to be numerically stable when compared to non-dissipative time marching integration schemes and requires less computational time compared to predictor/corrector methods for the full set of nonlinear EOM. DTIC
Equations of Motion; Flexible Wings; Remotely Piloted Vehicles
20060019446 Air Force Research Lab., Wright-Patterson AFB, OH USA
Agent-Based Cooperative Control
Barth, Eric J; Dec 2005; 23 pp.; In English Report No.(s): AD-A446345; AFRL-VA-WP-TM-2006-3031; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA446345; Avail.: CASI: A03, Hardcopy
This report addresses the formulation of a general theoretical framework for issues unique to cooperative control. The approach taken is to unify the fundamental principles of control Lyapunov functions, potential field theory, and the so-called optimal return function. These three principles are woven together to achieve an analytically vigorous formulation that addresses the required functionality of cooperative control problems. The development is prepared in the context of a multiple UAV cooperative ground moving target engagement scenario. DTIC
Remotely Piloted Vehicles; Robots
20060019480 Naval Air Systems Command, Patuxent River, MD USA
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Environmental Assessment in the UH-1Y and AH-1Z
Rudy, Maura A; Oct 2005; 8 pp.; In English Report No.(s): AD-A446388; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA446388; Avail.: CASI: A02, Hardcopy
The USA Marine Corps USMC Upgrade Program involves the remanufacture of all light/attack helicopters in the fleet to extend their service-life into the year 2020. In order to assess whether air quality was favorable for aircrew in the UH-1Y and AH-1Z aircraft, levels of carbon monoxide and hydrocarbons were measured during ground and flight operations. In the past, cockpit gas detection during flight was prohibitive, due to detector size and the resulting inability to mount sensors on aircrew. In this report, a novel method for measurement of combustion gases during ground and flight operations is discussed.
Commercially-available man-mounted sensors provide crucial cockpit air quality data in an unobtrusive manner, while eliminating the need for mounting equipment inside the aircraft, possible alteration of airframe, and reducing the risk of interference and injury to aircrew. Cockpit air-quality findings are discussed and recommendations are made to mitigate risk to aircrew. DTIC
Air Quality; Carbon Monoxide; Cockpits; Flight Crews; Hydrocarbons
20060019509 Air Force Research Lab., Wright-Patterson AFB, OH USA
Multi-AXIS Vibration Mitigation Properties of Seat Cushions During Military Propeller Aircraft Operational Exposures
Smith, S D; Smith, J A; Sep 27, 2005; 12 pp.; In English Report No.(s): AD-A446432; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA446432; Avail.: CASI: A03, Hardcopy
There have been increasing complaints of annoyance, fatigue, and musculoskeletal pain during prolonged exposures to propulsion-generated vibration in military propeller aircraft. The objective of this study was to evaluate the effects of seat cushions on mitigating the higher frequency (\g10 Hz) multi-axis vibration associated with Navy E-2C Hawkeye operations. An E-2C crew seat was used in the laboratory during exposure to a selected operational signal. Triaxial accelerations were measured at the interface between the human and cushion (seat pan and seat back). The most pronounced effects were observed at the blade passage frequency (-73.5 Hz). The highest vibration occurred at the seat pan in the fore-and-aft (X) direction of the subject (lateral direction of the aircraft). Substantial vibration was observed at the seat back in the vertical (Z) direction. Significantly lower levels of fore-and-aft (X) vibration occurred at the seat pan with all cushions as compared to the original E-2C cushion (P\h0.05). The largest reduction in the X acceleration was about 40% with a mean reduction of approximately 20% among the cushions. The results raised questions regarding psychophysical effects and whether the vibration mitigation at the blade passage frequency is sufficient for reducing the reported symptoms. DTIC
Accelerated Life Tests; Cushions; Exposure; Propellers; Seats; Vibration
20060019514 Naval Air Warfare Center, Patuxent River, MD USA
Mobile Aircrew Restraint System - MARS
Podob, Roger; Happ, Michael; Sample, Angela; Oct 2005; 9 pp.; In English; Original contains color illustrations Report No.(s): AD-A446438; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA446438; Avail.: CASI: A02, Hardcopy
For several decades, aircrew working in the cabin of military helicopters have used a simple nylon chest strap with an adjustable tether. commonly called a 'gunner's belt', as their fall protection system. The chest strap is donned and the tether is clipped to various anchor points in the cabin in order to provide fall protection. However. aircrew have been thrown out of the aircraft during mishaps, when using this configuration. This paper discusses the development of a system that provides a substantial improvement in fall and crash protection. The system consists of a webbing retractor that mounts to the aircraft cabin ceiling, extending and retracting webbing as the aircrew moves about the cabin. Attached to the retractor mount is a modified gunner's belt with a shorter tether. Should the aircraft crash or the aircrew fall, the retractor locks, preventing further webbing extraction. By preventing slack from developing, and proper location of the retractor within the aircraft, the system significantly improves the likelihood the aircrew will remain within the cabin. Additional work is underway to eliminate the gunner's belt completely by utilizing the lifting harness already worn as part of the AIRSAVE survival vest, thus distributing the crash or fall loads over the aircrew member's body. DTIC
Aircraft Compartments; Constraints; Flight Crews; Straps; Survival Equipment
20060019527 Martin-Baker Aircraft Co. Ltd., Denham, UK
Aircrew Endurance and Effectiveness
Ransley, Michelle; Loughran, Eileen; Oct 2005; 8 pp.; In English; Original contains color illustrations Report No.(s): AD-A446459; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA446459; Avail.: CASI: A02, Hardcopy
With changing operational environments for tactical aircraft new demands are being placed on aircrew, which are pushing the limits of physical endurance. In particular, mission durations have increased to the point that previous issues with ejection seat control have become more pronounced and have begun to affect aircrew performance. In the past, short duration missions have been the norm and the effect of ejection seat comfort was not well documented. However, changed mission profiles requiring extended seated durations have highlighted the effect of discomfort on aircrew performance. As part of the Navy Aircrew Common Ejection Seat (NACES) Stability Improvement Programme (SIP) Martin-Baker have been working alongside the US Navy to assess and develop comfort improvements suitable for the SJU- 17A seat used in F- 18's and T-45's. Various cushion designs were first assessed for anthropometric compatibility and thus comfort, and then environmental testing was undertaken on a reduced number of the chosen cushioning designs. The 3 most promising designs were finally tower and ejection tested in support of a flight clearance. Three F-18 squadrons, who complete regular evaluation questionnaires, are currently flying these three ejection seat designs. The initial results of this trial are demonstrating a need for improved lumbar support and the introduction of non-foam cushion inserts, rather than the highly compressible urethane and slow response cushions that are currently used. It is acknowledged that comfort affects the state of mental and physical well being of the aircrew, and their performance in the cockpit. Therefore understanding their endurance requirements and providing solutions to resolve these issues are imperative for the future of high performance fast jet aircrew. DTIC
Ejection Seats; Flight Crews
20060019528 Naval Medical Research Inst., San Diego, CA USA
Whole Body Vibration Exposure for MH-60S Pilots
Harrer, Kristin L; Yniguez, Debra; Majar, Maria; Ellenbecker, David; Estrada, Nancy; Geiger, Mark; Oct 2005; 13 pp.; In English; Original contains color illustrations Report No.(s): AD-A446461; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA446461; Avail.: CASI: A03, Hardcopy
Pilots of the MH-60S helicopter are exposed to continuous whole body vibration (WBV). Pilot fatigue is a growing operational concern due to the increased frequency of extended durations of missions (6-8+hours) in support of Operations Iraqi Freedom and Enduring Freedom. Endurance aspects of the currently used rotary wing seating systems were not optimized for the longer missions and wide range of pilot anthropometric measurements, which is now typical of naval aviation. The current seating systems were designed primarily to meet crashworthiness requirements, not for the wide range of pilot anthropometry or to mitigate WBV. Albeit, an issue, pilot fatigue and reduced mission effectiveness are also critical concerns. Current Hazard Reports (HAZREP) indicated that pain in both pilots' legs and backs begin 2 to 4 hours into the flight and increase with time. Situational awareness also decreases with an increase in flight duration due to the constant distraction of pilots shifting in their seats while flying to get comfortable. From (1987) reported a dose-response relationship between the length of military helicopter flights and back discomfort. He also concluded that this pain is typically dull, over the lower back, and its prevalence and intensity are dependent on the total flight hours of exposure. DTIC
Exposure; Helicopters; Seats; Vibration
20060019538 Naval Air Systems Command, Patuxent River, MD USA
An Investigation of Troop Seat Testing Methodology Using Madymo Models
Sieveka, Edwin M; Kitis, Levent; Oct 2005; 20 pp.; In English; Original contains color illustrations Report No.(s): AD-A446486; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA446486; Avail.: CASI: A03, Hardcopy
Energy-absorbing troop seats can save lives and mitigate injury in many military aircraft mishaps. Several designs are currently in the field and research continues to provide additional improvements. When it comes to evaluating performance, however, troop seats raise some issues that normally do not occur for pilot seats. Pilots have hand and foot controls that dictate the logical position for manikins in laboratory tests. The same cannot be said for troop seats, but positional variations can have significant effects on some test results. The first part of this study uses computer modeling with the MAthematical DYnamic MOdel (MADYMO) simulation program to examine the sensitivity of test outcome to troop seat occupant position. The vertical component of the lumbar load, a key performance parameter for troop seats, serves as the principal variable in case comparisons. For some types of seat energy absorbers (EAs), it is shown that changes in arm and leg position can produce lumbar load differences which exceed those that might be expected from normal test-to-test variability. These results point to a need for standardization so that tests of a given seat design, as well as tests of differing designs, can be compared directly. The second part of this paper considers an issue that arises in the testing of both troop and pilot seats: the method chosen todeliver the crash impulse. The two most common methods are a drop tower (DT) test and a horizontal accelerator (HA) test. In the latter, the seat is rotated 90 degrees to vertical so that the seat's Z-axis is aligned with the laboratory X-axis. This leads to questions about the influence of gravity on the test results. Once again, MADYMO simulations are employed to study test result sensitivity, and to determine whether gravity compensation is called for in the form of an HApulse adjustment or a small forward pitch of the HA seat. DTIC
Computerized Simulation; Dynamic Models; Energy Absorption; Injuries; Mathematical Models; Seats
20060019679 General Dynamics Advanced Information Systems, Dayton, OH USA
Evaluation of the Safety Performance of Ejection Seat Cushions
Cheng, Zhiqing; Pellenttiere, Joseph A; Sep 2004; 10 pp.; In English; Original contains color illustrations Report No.(s): AD-A446609; No Copyright; Avail.: CASI: A02, Hardcopy
Several operational and prototype ejection seat cushions were selected for the evaluation of their performance for the prevention and reduction of spinal injuries. The evaluation was performed using impact tests on the vertical deceleration tower, where a cushion was placed between the seat pan and the occupant (a 50th percentile Hybrid III manikin) and was subjected to +Gz impact at 8, 10, and 12 g, respectively. For comparison, tests were also conducted on a bare seat pan without a cushion. Based on the test data, analyses were performed to determine the dependency of certain occupant responses and structural responses on the cushions. The cushions were ranked in the sequences illustrating their performance merit in terms of the peak values of the lumbar force and other responses. DTIC
Cushions; Ejection Seats; Safety
20060019683 Logistics Management Engineering, Inc., Arden, NC USA
The Optimized Three Weight Range, Five Force Level EA System for Energy Absorbing Crew Seats
Peck, Walter R; Oct 2005; 14 pp.; In English; Original contains color illustrations Report No.(s): AD-A446614; No Copyright; Avail.: CASI: A03, Hardcopy
The addition of small females into the helicopter pilot population has increased appreciably the weight range for which energy absorbing crew seats must provide low probability of spinal injury performance in survivable crashes. The three weight range, five force level (3WR/5FL) energy absorber system is a simple approach to the solution of the problems associated with providing maximum aviator protection against spinal injury even in thirty-degree nose-down survivable crashes for the total ollot popuThtion. This paper presents the results of an optimization study performed on the 3WR/5FL energy absorber system. This study indicates that in a 42 feet per second crash the dynamic response index (DRI) can be kept at or below 18.2, the maximum lumbar acceleration will be at least 1.OG below the acceptable level of 20.4 C, and the maximum energy absorber stroke can be kept at or below 13.8 inches for small pilots, who will have the seat adjusted up for correct eye position, and at or below 12 inches for average and large pilots. This system is light weight, comparatively low cost, small size, easily maThtaThed, simple in operation, truly reliable and can meet the specification requirements for energy absorber systems. DTIC
Aircraft Safety; Flight Safety; Helicopters; Seats
20060019723 Naval Surface Warfare Center, Indian Head, MD USA
CKU-5C/A Rocket Catapult Aces II Sled Test Program
Wheeler, Craig; Reese, Milton; Briscoe, Thomas; Sep 2004; 9 pp.; In English; Original contains color illustrations Report No.(s): AD-A446695; No Copyright; Avail.: CASI: A02, Hardcopy
The CAD/PAD Department at the Indian Head Division, NSWC in conjunction with the Joint CAD/PAD Program, conducted a series of five ACES II ejection seat tests using the CKU-5C/A rocket catapult which has been developed to replace the current CKU-5B/A rocket catapult. The system tests included F-15, F-16, and A-10 configuration ACES II ejection seats with large (JPATS Case 6) and small (LOIS) anthropometric manikins that represented test conditions to evaluate the system compatibility of the revised rocket catapult design. Highlights of the system sled tests results, conducted by Goodrich AIP at the Hurricane Mesa Test Facility, and the Holloman Air Force Base High Speed Test Track are reviewed and key results presented. These results indicate acceptable system performance of the ACES II ejection seat with the upgraded CKU-5C/A rocket catapult. Figure 1 is a test sequence photo from the A-10 CKU-5C/A system test. DTIC
Catapults; Ejection Seats; Rocket Catapults; Sleds
20060019727 Naval Air Systems Command, Patuxent River, MD USA
Development of a Mobile Aircrew Webbing Retractor System
Podob, Roger; Culbertson, Chris; Sep 2004; 16 pp.; In English; Original contains color illustrations Report No.(s): AD-A446702; No Copyright; Avail.: CASI: A03, Hardcopy
System Requirements: (1) Prevent ejection of cabin aircrew in survivable crashes; (2) Minimize strike envelope within cabin in survivable crashes; (3) Provide in-flight fall protection; (4) Permit aircrew mobility for mission duties. DTIC
Ejection; Flight Crews; Helicopters; Retractable Equipment; Tethering; Webbing
20060019729 Naval Air Systems Command, Patuxent River, MD USA
Body Dynamics Computer Modeling: Prototyping of Safety Systems and Laboratory Tests
Sieveka, Ed; Sep 2004; 25 pp.; In English; Original contains color illustrations Report No.(s): AD-A446705; No Copyright; Avail.: CASI: A03, Hardcopy
CONCLUSIONS: Benefits of Modeling and Simulation for Safety System Prototyping: (1) Understand the safety issues; (2) Evaluate current system performance; (3) Establish realistic performance bounds; (4) Explore potential improvements. Benefits of Modeling and Simulation for Lab Experiment Prototyping: (1) Conceptualize proposed experiment; (2) Evaluate probably dynamics and loads; (3) Guide fixture fabrication; (4) Establish realistic test parameters; (5) Provide a reality check for test results. DTIC
Computerized Simulation; Helicopters; Human Body; Prototypes; Safety; Tethering
20060019753 Air Force Research Lab., Wright-Patterson AFB, OH USA
A Hypersonic Vehicle Model Developed with Piston Theory (Preprint)
Oppenheimer, Michael W; Doman, David B; Jan 2006; 9 pp.; In English Report No.(s): AD-A446749; AFRL-VA-WP-TP-2006-310; No Copyright; Avail.: CASI: A02, Hardcopy
For high Mach number flows, M \g 4, piston theory has been used to calculate the pressures on the surfaces of a vehicle. In a two-dimensional flow, a perpendicular column of fluid stays intact as it passes over a solid surface. Thus, the pressure at the surface can be calculated assuming the surface were a piston moving into a column of fluid. In this work, piston theory is used to calculate the rigid body forces, moments, and stability derivatives of a hypothetical hypersonic vehicle. Only longitudinal motion is considered in this case and lateral motion will be included in subsequent work. DTIC
Hypersonic Vehicles; Piston Theory; Pistons
20060019766 National Research Council of Canada, Ottawa, Ontario Canada
A Novel Adaptive Structural Impedance Control Approach to Suppress Aircraft Vibration and Noise
Wickramasinghe, Viresh; Zimcik, David; Chen, Yong; Oct 2004; 14 pp.; In English; Original contains color illustrations Report No.(s): AD-A446767; No Copyright; Avail.: CASI: A03, Hardcopy
No abstract available
Adaptive Control; Aircraft Noise; Approach Control; Impedance; Vibration
20060019771 Air Force Research Lab., Wright-Patterson AFB, OH USA
Evolving Self-Organized Behavior for Homogeneous and Heterogeneous UAV or UCAV Swarms
Price, Ian C; Mar 2006; 238 pp.; In English Report No.(s): AD-A446785; AFIT/GCS/ENG/06-11; No Copyright; Avail.: Defense Technical Information Center (DTIC)
This investigation uses a self-organization (SO) approach to enable cooperative search and destruction of retaliating targets with swarms of homogeneous and heterogeneous unmanned aerial vehicles (UAVs). To facilitate specific system design, a facilitating SO algebraic framework is created that emphasizes scalability, robustness, and exibility. This framework is then used to implement a UAV behavior architecture relying upon rules governing formation and target interaction. Sets of applicable behaviors are created by weighted summation of the rules where different weights act as distinct behavior archetypes. Appropriate behavior archetypes are based upon sense information distilled from the environment and a simple perceptron mapping. Successful behaviors are evolved within this architecture using a genetic algorithm. This approach tests a swarm of UAVs, when sensor and attack abilities are both homogeneous and heterogeneous, against targets with superior engagement range. Resulting behaviors are highly cooperative, generally scaleable, and robust. DTIC
Heterogeneity; Remotely Piloted Vehicles; Self Organizing Systems
20060019802 Air Force Research Lab., Wright-Patterson AFB, OH USA
On the Computation of the Ego-Motion and Distance to Obstacles for a Micro Air Vehicle
Iyer, R V; Jan 2006; 17 pp.; In English Report No.(s): AD-A446850; AFRL-VA-WP-TP-2006-311; No Copyright; Avail.: CASI: A03, Hardcopy
In this paper, we have considered the problem of velocity and range estimation for a UAV using a camera and the knowledge of total speed through a GPS device. We have shown that this problem can be solved using a reliability-based motion computation and an optimization problem that is well-posed. If the velocity in the body frame is known, then the problem results in a straight-forward solution. For the more complicated case, when only the total speed is known, we assume that the component of the linear velocity along the axis of the camera is positive. We show that these assumptions form minimal additional information required to solve the problem of ego-motion and range estimation. DTIC
Drone Vehicles; Motion; Pilotless Aircraft
20060019803 Air Force Research Lab., Wright-Patterson AFB, OH USA
Decision Making Under Uncertainty Applied to the Counter Scenario
Girard, Anouck; Jan 2006; 36 pp.; In English Report No.(s): AD-A446851; AFRL-VA-WP-TP-2006-312; No Copyright; Avail.: CASI: A03, Hardcopy
A team of micro air vehicles (MAV) are inspecting a sequence of objects to accumulate evidence to convict/acquit an object as a target. Images are sent to a remote operator who serves the role as feature detector. This apart models the MAV-operator team as a stochastic dynamic program (DP). Solution of the DP yields the optimal policy of actions to performon the objects regardless of the operator evaluation or when it is received. DTIC
Counters; Decision Making; Drone Vehicles
20060020088 Air Force Inst. of Tech., Wright-Patterson AFB, OH USA
A Comparison of Main Rotor Smoothing Adjustments Using Linear and Neural Network Algorithms
Miller, Nathan A; Mar 2006; 146 pp.; In English Report No.(s): AD-A446788; AFIT/GAE/ENY/06-M24; No Copyright; Avail.: CASI: A07, Hardcopy
Helicopter main rotor smoothing is a maintenance procedure that is routinely performed to minimize airframe vibrations induced by non-uniform mass and/or aerodynamic distributions in the main rotor system. This important task is both time consuming and expensive, so improvements to the process have long been sought. Traditionally, vibrations have been minimized by calculating adjustments based on an assumed linear relationship between adjustments and vibration response. In recent years, artificial neural networks have been trained to recognize non-linear mappings between adjustments and vibration response. This research was conducted in order observe the character of the adjustment mapping of the Vibration Management Enhancement Program's PC-Ground Base System (PC-GBS). Flight data from the UH-60, AH-64A, and AH-64D were utilized during the course of this study. What has been determined is that the neural networks of PC-GBS produce adjustments that can be reproduced by a linear algorithm, thus implying that the shape of the mapping is in fact linear. DTIC
Algorithms; Helicopters; Linear Systems; Maintenance; Neural Nets; Rotary Wings; Rotors; Smoothing
20060020094 Naval Air Systems Command, Patuxent River, MD USA
Influence of Added Head Mass Properties on Head/Neck Loads During Standard Helicopter Impact Conditions
Paskoff, Glenn; Sieveka, Ed; Sep 2004; 22 pp.; In English; Original contains color illustrations Report No.(s): AD-A446872; No Copyright; Avail.: CASI: A03, Hardcopy
Thirty-degree pitch-down helicopter crash pulses were examined at the Patuxent River Horizontal Accelerator facility. The pulses used were representative of standard seat qualification crash corridors for a variety of rotary wing platforms. The primary objectives of this effort were 1) to quantitatively determine the effect of varying helmet weight and center of gravity (CG) during simulated rotary wing crash scenarios, and 2) to perform data analysis using existing injury criteria to identify maximum requirements for helmet weight and CG for the extremes of the rotary wing aviator population. Quantification of risk was based upon aviator size, helmet mass properties and impact severity. Testing included a Hybrid III 95th percentile male, a 50th percentile male, and a 5th percentile female. In order to achieve the necessary helmet weight and CG values required for the tests, a head-mass fixture was developed and used in place of the manikin's head that allowed weights to be added both forward and laterally on the head to generate a wide array of weight and CG configurations. Modeling of the system was performed using MADYMO, which was used to refine the test matrix for the weight and CG locations that would most likely define the mass properties envelope from the known criteria force/moment limits. A comprehensive analysis of the data was performed using available injury predictors to determine the likelihood of injury to the upper and lower cervical pine. The Nij cervical injury criterion developed by the National Highway and Traffic Safety Administration (NHTSA) was adapted and used to determine the risk of cervical injury. An analysis of variance (ANOVA) with a post-hoc Tukey-Kramer test to determine the source of the difference was conducted on the principal neck parameters to determine whether any of the factors were statistically significant (defined as pd0.05). DTIC
Helicopters; Loads (Forces)
20060020177 NASA Langley Research Center, Hampton, VA, USA
Free-jet Testing of a REST Scramjet at Off-Design Conditions
Smart, Michael K.; Ruf, Edward G.; 2006; 12 pp.; In English; 25th AIAA Aerodynamic Measurement Technology and Ground Testing Conference, 5-8 Jun. 2006, San Francisco, CA, USA; Original contains color illustrations Contract(s)/Grant(s): SAA1-664; 489-02-07-07-01 Report No.(s): AIAA Paper 2006-2955; Copyright; Avail.: CASI: A03, Hardcopy
Scramjet flowpaths employing elliptical combustors have the potential to improve structural efficiency and performance relative to those using planar geometries. NASA Langley has developed a scramjet flowpath integrated into a lifting body vehicle, while transitioning from a rectangular capture area to both an elliptical throat and combustor. This Rectangular-to- Elliptical Shape Transition (REST) scramjet, has a design point of Mach 7.1, and is intended to operate with fixed-geometry between Mach 4.5 and 8.0. This paper describes initial free-jet testing of the heat-sink REST scramjet engine model at conditions simulating Mach 5.3 flight. Combustion of gaseous hydrogen fuel at equivalence ratios between 0.5 and 1.5 generated robust performance after ignition with a silane-hydrogen pilot. Facility model interactions were experienced for fuel equivalence ratios above 1.1, yet despite this, the flowpath was not unstarted by fuel addition at the Mach 5.3 test condition. Combustion tests at reduced stagnation enthalpy indicated that the engine self-started following termination of the fuel injection. Engine data is presented for the largest fuel equivalence ratio tested without facility interaction. These results indicate that this class of three-dimensional scramjet engine operates successfully at off-design conditions. Author
Free Jets; Supersonic Combustion Ramjet Engines; Test Facilities; Computational Fluid Dynamics; Wind Tunnel Tests; Aircraft Design
20060020216 NASA Langley Research Center, Hampton, VA, USA
Overview of NATO Background on Scramjet Technology, Chapter 1
Drummond, J. Philip; Bouchez, Marc; McClinton, Charles R.; [2006]; 28 pp.; In English; Original contains color and black and white illustrations Contract(s)/Grant(s): 708-72-80-01; Copyright; Avail.: CASI: A03, Hardcopy
The purpose of the present overview is to summarize the current knowledge of the NATO contributors. All the topics will be addressed in this chapter, with references and some examples. This background enhances the level of knowledge of the NATO scramjet community, which will be used for writing the specific chapters of the Report. Some previous overviews have been published on scramjet technology worldwide. NASA, DOD, the U.S. industry and global community have studied scramjet- powered hypersonic vehicles for over 40 years. Within the U.S. alone, NASA, DOD (DARPA, U.S. Navy and USAF), and industry have participated in hypersonic technology development. Over this time NASA Langley Research Center continuously studied hypersonic system design, aerothermodynamics, scramjet propulsion, propulsion-airframe integration, high temperature materials and structural architectures, and associated facilities, instrumentation and test methods. These modestly funded programs were substantially augmented during the National Aero-Space Plane (X-30) Program, which spent more than $3B between 1984 and 1995, and brought the DOD and other NASA Centers, universities and industry back into hypersonics. In addition, significant progress was achieved in all technologies required for hypersonic flight, and much of that technology was transferred into other programs, such as X-33, DC-X, X-37, X-43, etc. In addition, technology transfer impacted numerous other industries, including automotive, medical, sports and aerospace. Derived from text
Hypersonic Flight; Hypersonic Vehicles; Supersonic Combustion Ramjet Engines
20060020221 NASA Langley Research Center, Hampton, VA, USA
Fuel-Air Mixing and Combustion in Scramjets, Chapter 6
Drummond, J. Philip; Diskin, Glenn S.; Cutler, Andrew D.; [2006]; 15 pp.; In English; Original contains black and white illustrations Contract(s)/Grant(s): 708-72-80-01; Copyright; Avail.: CASI: A03, Hardcopy
At flight speeds, the residence time for atmospheric air ingested into a scramjet inlet and exiting from the engine nozzle is on the order of a millisecond. Therefore, fuel injected into the air must efficiently mix within tens of microseconds and react to release its energy in the combustor. The overall combustion process should be mixing controlled to provide a stable operating environment; in reality, however, combustion in the upstream portion of the combustor, particularly at higher Mach numbers, is kinetically controlled where ignition delay times are on the same order as the fluid scale. Both mixing and combustion time scales must be considered in a detailed study of mixing and reaction in a scramjet to understand the flow processes and to ultimately achieve a successful design. Although the geometric configuration of a scramjet is relatively simple compared to a turbomachinery design, the flow physics associated with the simultaneous injection of fuel from multiple injector configurations, and the mixing and combustion of that fuel downstream of the injectors is still quite complex. For this reason, many researchers have considered the more tractable problem of a spatially developing, primarily supersonic, chemically reacting mixing layer or jet that relaxes only the complexities introduced by engine geometry. All of the difficulties introduced by the fluid mechanics, combustion chemistry, and interactions between these phenomena can be retained in the reacting mixing layer, making it an ideal problem for the detailed study of supersonic reacting flow in a scramjet.With a good understanding of the physics of the scramjet internal flowfield, the designer can then return to the actual scramjet geometry with this knowledge and apply engineering design tools that more properly account for the complex physics. This approach will guide the discussion in the remainder of this section. Derived from text
Combustion; Fluid Mechanics; Fuel Injection; Supersonic Combustion Ramjet Engines; Mixing Layers (Fluids)
20060020247 Air Force Inst. of Tech., Wright-Patterson AFB, OH USA
Performance Capability of a Damaged Lighter-Than-Air Vehicle Operating in the Near Space Regime
Vogt, Jr, Charles W; Mar 2006; 93 pp.; In English; Original contains color illustrations Report No.(s): AD-A446699; AFIT/GSS/ENY/06-M13; No Copyright; Avail.: CASI: A05, Hardcopy
This study investigates the ability of a high-altitude airship to maintain lift following the compromise of its lifting gas envelope. Accepted engineering principles are applied to develop a model that provides comparative analyses for airship depressurization alternatives following hull compromise. Specifically, maintaining lifting gas envelope overpressure to provide controllability in wind currents while sacrificing some buoyancy is compared with allowing envelope depressurization to occur with the goal of maintaining greater buoyancy as long as possible. The model provides insights to alternatives for recovering a damaged vehicle and its payload. In particular, the analysis demonstrates that maintaining the ability to navigate while forfeiting buoyancy can provide additional down-range maneuver capability. In some cases preserving the airship's hull overpressure for some period of time following compromise, vice allowing a slow depressurization to atmospheric equilibrium, extends the distance a damaged airship can sustain controlled navigation as much as eighty percent. However, the airship will forfeit nearly twenty percent of the altitude it would otherwise preserve by not forcing a constant hull overpressure. DTIC
Airships; Controllability; Hulls (Structures); Navigation
20060020248 Goodrich AIP, Phoenix, AZ USA
Digital Recovery Sequencer - ACES Ejection Seats
Ross, David A; Cotter, Lee; Culhane, David; Ferrell, Steven; Sep 2004; 9 pp.; In English; Original contains color illustrations Report No.(s): AD-A446714; No Copyright; Avail.: CASI: A02, Hardcopy
The ACES ejection seats currently utilize a Recovery Sequencer based on analog technology to control ejection event timing and ejection mode selection. The Recovery Sequencer has limitations with respect to installed life, electronic component obsolescence, flexibility to accommodate seat safety improvements, and mode differentiation at the Mode 1 to 2 crossover point. The Digital Recovery Sequencer (DRS) program was undertaken by Goodrich, the seat OEM, and the CAD/PAD Joint Program Office (JPO) to design and qualify a sequencer based on digital technology that overcomes the limitations of the Recovery Sequencer. The DRS Program was broken down into three phases. DTIC
Ejection Seats; Ejection; Analog Data
20060020757 NASA Langley Research Center, Hampton, VA, USA
Advances in Hot-Structure Development
Rivers, H. Kevin; Glass, David E.; [2006]; 11 pp.; In English; 5th European Workshop on Thermal Protection Systems and Hot Structures, 17-19 May 2006, Noordwiji, Netherlands; Original contains color illustrations; No Copyright; Avail.: CASI: A03, Hardcopy
The National Aeronautics and Space Administration has actively participated in the development of hot structures technology for application to hypersonic flight systems. Hot structures have been developed for vehicles including the X-43A, X-37, and the Space Shuttle. These trans-atmospheric and atmospheric entry flight systems that incorporate hot-structures technology are lighter weight and require less maintenance than those that incorporate parasitic, thermal-protection materials that attach to warm or cool substructure. The development of hot structures requires a thorough understanding of material performance in an extreme environment, boundary conditions and load interactions, structural joint performance, and thermal and mechanical performance of integrated structural systems that operate at temperatures ranging from 1500 C to 3000 C, depending on the application. This paper will present recent advances in the development of hot structures, including development of environmentally durable, high temperature leading edges and control surfaces, integrated thermal protection systems, and repair technologies. The X-43A Mach-10 vehicle utilized carbon/carbon (C/C) leading edges on the nose, horizontal control surface, and vertical tail. The nose and vertical and horizontal tail leading edges were fabricated out of a 3:1 biased, high thermal conductivity C/C. The leading edges were coated with a three-layer coating comprised of a SiC conversion of the C/C, followed by a CVD layer of SiC, followed by a thin CVD layer of HfC.Work has also been performed on the development of an integrated structure and was focused on both hot and warm (insulated) structures and integrated fuselage/tank/TPS systems. The objective was to develop integrated multifunctional airframe structures that eliminate fragile external thermal-protection systems and incorporate the insulating function within the structure. The approach taken to achieve this goal was to develop candidate hypersonic airframe concepts, including structural arrangement, load paths, thermalstructural wall design, thermal accommodation features, and integration of major components, optimize thermalstructural configurations, and validate concepts through a building block test program and generate data to improve and validate analytical and design tools. Author
Carbon-Carbon Composites; Aircraft Structures; Control Surfaces; Design Analysis; Structural Engineering; Structural Design; Tail Assemblies; Temperature Control; Stabilizers (Fluid Dynamics)
20060020788 Forensic Safety Group, Hatboro, PA USA
Pretensioners and Injury Risk
Yannaccone, John R; Whitman, Gary R; Sicher, Larry; Oct 2005; 28 pp.; In English; Original contains color illustrations Report No.(s): AD-A446485; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA446485;Avail.: CASI: A03, Hardcopy
In recent years rotary wing aircraft restraint systems that incorporate pretensiones have appeared on the market. While similar systems have been available and used in production automobiles for over 30 years, there have been concerns regarding the potential of injuring occupants should such systems be fielded in aircraft. This paper provides an overview of the purpose and function of a pretensioner. It discusses the performance enhancements provided by pretensioned restraint systems in ground vehicles. It also discusses the protection offered by pretensioned restraint systems and provides an overview of the literature related to thoracic and other injuries in pretensioned restraint systems. The benefits a pretensioner is expected to provide in fixed and rotary wing aircraft and integration issues will also be discussed. Based on the research performed and the real world performance of pretensioners in the automotive environment, it is apparent that pretensions have great potential to decrease the risk of injury to occupants in aircraft without introducing ant significant potential for injury as result of the loads generated by the pretensioner itself. DTIC
Aircraft Configurations; Fixed Wings; Injuries; Risk; Rotary Wing Aircraft; Safety
20060020806 Air Force Inst. of Tech., Wright-Patterson AFB, OH USA
A Monocular Vision Based Approach to Flocking
Kirchner, Brian P; Mar 2006; 81 pp.; In English Contract(s)/Grant(s): DACA99-99-C-9999 Report No.(s): AD-A446909; AFIT/GCS/ENG/06-09; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA446909;Avail.: CASI: A05, Hardcopy
Flocking is seen in nature as a means for self protection, more efficient foraging, and other search behaviors. Although much research has been done regarding the application of this principle to autonomous vehicles, the majority of the research has relied on GPS information, broadcast communication, an omniscient central controller, or some other form of 'global' knowledge. This approach, while effective, has serious drawbacks, especially regarding stealth, reliability, and biological grounding. This research effort uses three Pioneer P2-AT8 robots to achieve flocking behavior without the use of global knowledge. The sensory inputs are limited to two cameras, offset such that the area of stereo vision is minimal, thus making stereo image analysis techniques effectively impossible, but allowing a much larger effective field of vision. The flocking algorithm analyzes these images and updates each robot's velocity vector according to the relative position, heading, and speed of its nearest neighbor. The result of this velocity update is an eventual stabilization of speed and heading, resulting in a coherent, stable flock, demonstrated in both software simulation and in hardware. DTIC
Algorithms; Bionics; Control; Drone Vehicles; Formation Flying; Image Processing; Monocular Vision; Pilotless Aircraft; Robotics
20060020844 Air Force Research Lab., Edwards AFB, CA USA
Propulsion and Power Generation Capabilities of a Dense Plasma Focus (DPF) Fusion System for Future Military Aerospace Vehicles (POSTPRINT)
Knecht, Sean D; Mead, Franklin B; Thomas, Robert E; Miley, George H; Froning, David; Oct 6, 2005; 8 pp.; In English Contract(s)/Grant(s): Proj-4847 Report No.(s): AD-A446973; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA446973; Avail.: CASI: A02, Hardcopy
The objective of this study was to perform a parametric evaluation of the performance and interface characteristics of a dense plasma focus (DPF) fusion system in support of a USAF advanced military aerospace vehicle concept study. This vehicle is an aerospace plane that combines clean 'aneutronic' dense plasma focus (DPF) fusion power and propulsion technology, with advanced 'waverider'-like airframe configurations utilizing air-breathing MHD propulsion and power technology within a reusable single-stage-to-orbit vehicle. The applied approach was to evaluate the fusion system details (geometry, power, T/W, system mass, etc.) of a baseline p-11B DPF propulsion device with Q = 3.0 and thruster efficiency, eta prop = 90% for a range of thrust, Isp and capacitor specific energy values. The baseline details were then kept constant and the values of Q and eta prop were varied to evaluate excess power generation for communication systems, pulsed-train plasmoid weapons, ultrahigh-power lasers, shielding/cloaking devices and gravity or time-distorting devices. Thrust values were varied between 100 kN and 1,000 kN with Isp of 1,500 s and 2,000 s, while capacitor specific energy was varied from 1 - 15 kJ/kg. Q was varied from 3.0 to 6.0, resulting in gigawatts of excess power. Thruster efficiency was varied from 0.9 to 1.0, resulting in hundreds of megawatts of excess power. Resulting system masses were on the order of 10's to 100's of metric tons with thrust-to-weight ratios ranging from 2.1 to 44.1, depending on capacitor specific energy. Such a high thrust/high Isp system with a high power generation capability would allow military versatility in sub-orbital space, as early as 2025, and beyond as early as 2050. This paper presents only the views and recommendations of the authors themselves and are not necessarily those of the Air Force. DTIC
Aerospace Planes; Aerospace Vehicles; Controlled Fusion; Dense Plasmas; Plasma Control; Plasma Focus; Propulsion
20060020900 Arkansas Univ., Fayetteville, AR USA
Quantifying the Impact of Aircraft Cannibalization
Cassady, C R; Mendoza, Alejandro; Ormon, Stephen; Schneider, Kellie; Rainwater, Chase; Carrasco, Mauricio; Crawford, Jonathan; Honeycutt, Jason; Dec 2003; 27 pp.; In English Contract(s)/Grant(s): F33615-99-D-6001-23; Proj-4923 Report No.(s): AD-A447077; MM0206; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA447077; Avail.: CASI: A03, Hardcopy
The primary objective of this project was to develop a mathematical modeling methodology for assessing the impact of cannibalization on fleet performance in order to identify policies for making effective cannibalization decisions and to study the impact of these policies on management of the spare parts supply chain. To achieve this objective, we pursued two research avenues in parallel. First, we developed and analyzed a 'generic' cannibalization model. This discrete-event simulation model was used to investigate two key issues related to aircraft readiness: cannibalization and spare parts inventory levels. Second, we developed and analyzed two discrete-event simulation models based on the cannibalization practices that take place at Hill AFB. These models were used to investigate several key issues raised by USAF officers experienced with conditions similar to those existing at Hill AFB. DTIC
Maintenance; Mathematical Models
20060020908 Air Force Inst. of Tech., Wright-Patterson AFB, OH USA
Performance Analysis of a Cooperative Search Algorithm for Multiple Unmanned Aerial Vehicles under Limited Communication Conditions
Morris, Kevin M; Mar 2006; 138 pp.; In English Report No.(s): AD-A447093; AFIT/GE/ENG/06-44; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA447093; Avail.: CASI: A07, Hardcopy
This research investigates the impacts of realistic wireless communications upon a group of unmanned aerial vehicles (UAVs) utilizing a distributed search algorithm. The UAVs are used to survey an area for mobile targets and they require communication to cooperatively locate the targets. The mobile targets do not continually radiate energy, which exacerbates the search effort; a UAV could fly directly over a target and not detect it. A simulation of cooperative UAVs is implemented using the OPNET Modeler network simulation tool. The search performance of a group of UAVs is observed when communication range, data rate, and the number of UAVs are varied. The performance is evaluated based on the total time it takes for the UAVs to completely detect all the targets in a given search area, the number of times internal reas are scanned, the amount of communication throughput achieved, the network traffic generated, network latency, and number of network collisions. The results indicate that the number of UAVs was found to have the greatest impact on the group's ability to search an area, implying that the data shared between the UAVs provides little benefit to the search algorithm. In addition, it was found that a network with a 100 Kbps or faster data rate should allow for minimal congestion and a large degree of scalability. The findings demonstrate that the proposed four-stage search algorithm should operate reasonably well under realistic conditions. DTIC
Algorithms; Communication Networks; Detection; Drone Vehicles; Pilotless Aircraft; Reliability Analysis; Target cquisition;
Wireless Communication
20060020927 Air Force Academy, CO USA
Detached-Eddy Simulations of Full Aircraft Experiencing Massively Separated Flows
Morton, S A; Forsythe, J R; Squires, K D; Cummings, R M; Apr 14, 2005; 11 pp.; In English; Original contains color illustrations Report No.(s): AD-A447205; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA447205; Avail.: CASI: A03, Hardcopy
A high resolution turbulence treatment for massively separated flows is presented for fighters at flight Reynolds numbers. The method is Detached Eddy Simulation (DES), a hybrid Reynolds averaged Navier-Stokes - Large Eddy Simulation technique that can accurately capture attached boundary layers at flight Reynolds numbers, while still reproducing the unsteady loads associated with massively separated flow. Three examples of US Department of Defense aircraft, the F-15E, F/A-18C and F/A-18E, are used as test cases to show the utility of Detached Eddy Simulation in capturing nonlinear phenomena such as wing buffet, vortex breakdown, and abrupt wing stall. Comparison with either flight test or experiment is also accomplished for these cases. DTIC
Aircraft; Boundary Layer Separation; Separated Flow; Simulation; Vortices
20060020957 Naval Research Lab., Washington, DC USA
Loop-Dipole Antenna Modeling using the FEKO Code
Lippincott, Wendy L; Pickard, Thomas; Nichols, Randy; Jan 2005; 5 pp.; In English; Original contains color illustrations Report No.(s): AD-A447233; No Copyright; Avail.: CASI: A01, Hardcopy
A study was done to optimize the design of a loop dipole antenna over a broad frequency range (0.5-2 GHz) using the FEKO method of moments code. Variations to the design were modeled as well as the performance of the antenna in an array. The modeling was compared to anechoic chamber data. The fields generated by the FEKO code were also input to a GTD (geometric theory of diffraction) code as an antenna pattern to model the multipath effects caused by mounting the antenna onto an aircraft. DTIC
Aircraft; Dipole Antennas; Loop Antennas; Optimization
20060020992 Massachusetts Inst. of Tech., Cambridge, MA USA
High Speed Linear Induction Motor Efficiency Optimization
Johnson, Andrew P; Jun 2005; 188 pp.; In English Report No.(s): AD-A447307; No Copyright; Avail.: CASI: A09, Hardcopy
One of the reasons linear motors, a technology nearly a century old, have not been adopted for a large number of linear motion applications is that they have historically had poor efficiencies. This has restricted the progress of linear motor development. The concept of a linear motor as a rotary motor cut and laid out flat with a conventional rotary motor control scheme as a design basis may not be the best way to design and control a high-speed linear motor. End effects and other geometry subtleties of a linear motor make it unique, and a means of optimizing efficiency with both the motor geometry and the motor control scheme will be analyzed to create a High-Speed Linear Induction Motor (LIM) with a higher efficiency than what is possible with conventional motors and controls. This thesis pursues the modeling of a short secondary type Double-Sided Linear Induction Motor (DSLIM) that is proposed for use as an Electromagnetic Aircraft Launch System (EMALS) aboard the CVN-2 1. Mathematical models for the prediction of effects that are peculiar to DSLIM are formulated, and their overall effects on the performance of the proposed machine are analyzed. These effects are used to generate atransient motor model, which is then driven by a motor controller that is specifically designed to the characteristics of the proposed DSLIM. Due to this DSLIM's role as a linear accelerator, the overall efficiency of the DSLIM will be judged by the kinetic energy of the launched projectile versus the total electric energy that the machine consumes. This thesis is meant to propose a maximum possible efficiency for a DSLIM in this type of role. DTIC
High Speed; Induction Motors; Launching; Linear Systems
20060021045 Concordia Univ., Montreal, Quebec Canada
Modeling Multiple HF Antennas on the C-130/Hercules Aircraft - Part II
Kubina, Stanley J; Trueman, Christopher W; Gaudine, David; Lau, Anita K; Jan 1, 2005; 5 pp.; In English; Original contains color illustrations Report No.(s): AD-A447453; No Copyright; Avail.: CASI: A01, Hardcopy
Long-range transport aircraft such as the C-130/Hercules require reliable HF communication systems for their global missions. In some cases dual HF systems are installed using two separate antennas, in a SIMOP mode: one antenna for transmitting and the other for receiving, at arbitrary frequencies over the 2-30 MHz HF frequency range. Candidate antennas for such HF systems are probes on the vertical stabilizer or the wingtips and dorsal or wing-root notch antennas. Previous work has modeled the HF performance of these antennas by executing spectral sweeps of models at 0.1 MHz increments using the NEC4 and MBC computer codes. These results were also correlated with scale model radiation pattern and impedance measurements. In this paper the results of explicit modeling of the SIMOP mode are presented for the candidate antenna pairs. The receive antenna terminals are terminated in 50 ohms and transmit and receive currents are extracted from the solution file and each pair is plotted vs. frequency. It is seen that peaks in the antenna coupling correspond to the resonant peaks in plots of impedance reported earlier. Insights provided by current distribution plots on the wire-grid model for each antenna allow the degree of antenna coupling to be well understood. This exceptional use of the CEM Virtual Antenna Range can lead to very cost-effective HF SIMOP installation designs. DTIC
Antennas; C-130 Aircraft; High Frequencies; Stabilizers (Fluid Dynamics); Transport Aircraft
20060021540 Congressional Budget Office, Washington, DC USA
CBO Testimony: Modernizing Tactical Aircraft
Williams, Cindy; Apr 16, 1997; 29 pp.; In English Report No.(s): AD-A447663; No Copyright; Avail.: CASI: A03, Hardcopy
Our analysis suggests that DoD's planned aircraft purchases for fighter fleets will be difficult to afford. CBO projected prices for the three new fighters the department plans to buy: the F-22, the Joint Strike Fighter (JSF), and the F/A-18E/F. The costs of two of those planes--the F-22 and the JSF--are likely to far exceed DoD's current goals. Since CBO released its analysis, DoD has released an estimate of F-22 program costs that sheds further light on the potential for cost growth in the fighter program. That estimate was part of a Congressionally mandated report on the F-22's cost. Prepared by the Office of the Secretary of Defense's Cost Analysis Improvement Group, that report expressed concerns similar to those raised by CBO about the potential for higher prices. I will have more to say about that later in my testimony. Another problem for DoD will be the aging of its aircraft fleets. Even though current plans call for buying about 4,400 new aircraft between now and 2030, the planned pace of purchases will mean that, to prevent shortfalls, the services will have to operate aircraft to unprecedented ages. The average age of aircraft today is about 10 years, reflecting the historical practice of replacing tactical fighter and attack aircraft as they approach 20 years of service. By 2003, however, the average age for all Air Force tactical aircraft will exceed 15 years, and it will peak at 18 years by 2010. The Department of the Navy's tactical aircraft fleet will also age, but to a lesser extent, reaching an average age of 15 years by 2008. Joint Strike Fighters begin to arrive in quantity after 2008, so then the average age of the Navy's fleet begins to decline. CBO's analysis presents policy alternatives that address the problems of affordability and aging. It lays out specific alternatives that illustrate the hard choices that DoD might have to make if current plans for tactical aviation prove to be unaffordable. DTIC
Cost Analysis; Military Technology; Attack Aircraft; Policies
Source: NASA
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