Structural Design Analysis of the Tail Landing Gear Bay and the Vertical/Horizontal Stabilizers of the RAH-66 Comanche Helicopter

Structural Design Analysis of the Tail Landing Gear Bay and the Vertical/Horizontal Stabilizers of the RAH-66 Comanche Helicopter PDF

Author: Brian Shoop

Publisher:

Published: 1997-09-01

Total Pages: 80

ISBN-13: 9781423570158

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The RAH-66 Comanche's stealth design requires the use of radar- absorbing material (RAM) on the outer skin of the aircraft. The reduced stiffness properties of RAM produce insufficient tail torsional stiffness, necessitating the use of non-radar-absorbing graphite on the outer skin of the tail section. This thesis investigates structural design modifications to increase the tail section's stiffness to allow the use of RAM on the outer skin and still meet all structural requirements. An original model represents the prototype aircraft at first flight. The goal is to create a model using RAM on the outer skin that watches the structural stiffness of the original model. This thesis builds on earlier work conducted at the Naval Postgraduate School (NPS). Two new design modifications to the tailbone are developed. The best modification increases the torsional stiffness of a baseline model by six percent. Integrating earlier NPS modifications increases torsional stiffness by 12 percent. When RAM is applied to the outer skin of the modified model, torsional stiffness is reduced by only six percent from the baseline as compared to a 24 percent reduction with no modifications. Additional modifications to the vertical and horizontal stabilizers further increase structural stiffness and reduce weight.

Analysis of Potential Structural Design Modifications for the Tail Section of the RAH-66 Comanche Helicopter

Analysis of Potential Structural Design Modifications for the Tail Section of the RAH-66 Comanche Helicopter PDF

Author: Vincent M. Tobin

Publisher:

Published: 1997-06-01

Total Pages: 117

ISBN-13: 9781423571865

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The Army RAH-66 Camanche Helicopter made its first flight in January of 1996. Its current structural configuration, however, does not meet the Army's requirements for radar signature. Structural configurations of the tailcone that meet radar cross-section requirements tend to lack sufficient structural stiffness due to the presence of Kevlar in place of graphite on the outer mold line. This thesis investigates potential structural design modifications to the Comanche tailcone that would move the design closer to meeting both its structural and radar signature requirements. Structural geometry modifications with baseline (current configuration) materials increased torsional stiffness by nine percent. Geometry modifications using radar signature-compliant materials reduced torsional stiffness by 10 percent. The geometry changes analyzed produce structural performance improvements insufficient to allow the use of radar- compliant materials without further geometry changes.

Analysis of Potential Structural Design Modifications for the Tail Section of the RAH-66 Comanche Helicopter

Analysis of Potential Structural Design Modifications for the Tail Section of the RAH-66 Comanche Helicopter PDF

Author: Vincent M. Tobin

Publisher:

Published: 1997-06-01

Total Pages: 119

ISBN-13: 9781423569534

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The Army RAH-66 Comanche Helicopter made its first flight in January of 1996. Its current structural configuration, however does not meet the Army's requirements for radar signature. Structural configurations of the tailcone that meet radar cross-section requirements tend to lack sufficient structural stiffness due to the presence of Kevlar in place of graphite on the outer mold line. This thesis investigates potential structural design modifications to the Comanche tailcone that would move the design closer to meeting both its structural and radar signature requirements. Geometry modifications with baseline (current configuration) materials increased torsional stiffness by nine percent. Structural geometry modifications using radar signature compliant materials reduced torsional stiffness by 10 percent. The geometry changes analyzed produce structural performance improvements insufficient to allow the use of radar-compliant materials without further geometry changes.

Flight Service Evaluation of Composite Components on Bell 206L and Sikorsky S-76 Helicopters

Flight Service Evaluation of Composite Components on Bell 206L and Sikorsky S-76 Helicopters PDF

Author: Donald J. Baker

Publisher:

Published: 1983

Total Pages: 20

ISBN-13:

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Progress on two programs to evaluate composite structural components in flight service on commercial helicopters is described. Thirty-six ship sets of composite components that include the litter door, baggage door, forward fairing, and vertical fin have been installed on Bell Model 206L helicopters that are operating in widely different climatic areas. Four horizontal stabilizers and ten tail rotor spars that are production components on the S-76 helicopter will be tested after prescribed periods of service to determine the effects of the operating environment on their performance. Concurrent with the flight evaluation, specimens from materials used to fabricate the components are being exposed in ground racks and tested at specified intervals to determine the effects of outdoor environments. Results achieved from 14,000 hours of accumulated service on the 206L components, tests on a S-76 horizontal stabilizer after 1600 hours of service, tests on a S-76 tail rotor spar after 2300 hours service, and two years of ground based exposure of material coupons are reported. (Author).

An Analysis of the Impact of Reliability and Maintainability on the Operating and Support (O&S) Costs and Operational Availability (AO) of the RAH- 66 Comanche Helicopter

An Analysis of the Impact of Reliability and Maintainability on the Operating and Support (O&S) Costs and Operational Availability (AO) of the RAH- 66 Comanche Helicopter PDF

Author: Gregg M. Dellert

Publisher:

Published: 2001-12-01

Total Pages: 142

ISBN-13: 9781423524182

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The RAH-66 Comanche helicopter program was initiated in 1983 to develop a reliable and maintainable attack/reconnaissance aircraft to replace the aging feet of AH-1 Cobra and OH-58 A/C helicopters. After several funding reductions and restructurings, the program entered the Engineering and Manufacturing Development (EMD) stage of the acquisition process in 2000. With only four years remaining until initial fielding, the program office is still attempting to reach the ambitious reliability and maintainability goals needed to experience reduced operating and support (O&S) costs and high operational availability (Ao). This thesis analyzes the impact of reliability and maintainability on the O&S costs and Ao of the Comanche helicopter. The research focused on the question of where the Comanche program office should allocate resources to minimize O&S costs and maximize Ao. The research indicated that the best allocation of resources is to the improvement of system reliability. The negative impact to both O&S costs and Ao is significant if the predicted reliability goals are not met.

Military Airframe Costs

Military Airframe Costs PDF

Author: Obaid Younossi

Publisher: Rand Corporation

Published: 2001

Total Pages: 141

ISBN-13: 9780833030368

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In recent years, a number of attempts have been made to estimate the cost of future weapon systems toward the goal of optimizing acquisition policy. This report focuses specifically on the effects of material mix, manufacturing techniques, and geometric part complexity on the cost of military airframes. It begins by offering background information on those materials that are most critical to airframe manufacture and on the relative advantages of both traditional and evolving part fabrication techniques. It then proceeds to a quantitative analysis of the cost implications of various materials and manufacturing techniques on airframe production, drawing both from an industry survey and from analysis of industry data. The data thus derived are then integrated with those of a comprehensive historical database. The report concludes that composites, while offering a number of advantages over metals in airframe manufacture, are generally associated with higher costs across a range of categories. At the same time, it concludes that while new manufacturing technologies hold the potential to diminish airframe manufacturing costs, the increased airframe complexity of future fighter aircraft may well offset this advantage. The report recommends that cost analysts remain abreast of changes in industry practice so that they may more accurately gauge the potential effects of such changes on future airframe costs.

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