Attachment 1.C - NFAC Test Planning Guide.pdf

Test Planning Guide – 2016 40x80 and 80x120 Wind Tunnel Test Sections

NFAC Test Planning Guide January 2016 Page 1

National Full-Scale Aerodynamics Complex

Test Planning Guide for Experiments in the 40- by 80- Foot and 80- by 120- Foot

Wind Tunnel Facilities

Revision January 2016

Approved for Public Release

This is a controlled document. Printed copies are for reference only.

Table of Contents

Overview

Acronyms

1. Introduction

2. NFAC Test Process

2.1 Planning Phase

2.2 Design and Fabrication

2.3 Test Execution Phase

2.4 Reporting Phase

3. Test Process Documentation

3.1 NFAC Test Documentation Outline

3.2 Test Plan & Test Requirements Documentation

3.2.1 Programmatic and Operational Requirements

3.2.2 Instrumentation and Data Acquisition Requirements

3.3 Design Analysis Documentation

3.3.1 Predicted Loads Report

3.3.2 Stress Analysis Report

3.3.3 Dynamic Stability Analysis

3.3.4 Fragmentation Analysis

3.3.5 Fatigue Analysis

3.3.6 Safety Factor Summary

3.3.7 Monitoring Requirements

3.3.8 Certifications, Inspections, and Qualification Tests

3.4 Safety Analysis Documentation

3.5 Planning Meetings and Review Minutes

3.6 Additional Documentation

Appendix Test Request Form NFAC Hazard Severity and Probability Matrix Test Readiness Report Guide NFAC Data Acquisition System Security Agreement Request for Access to NFAC Data Systems

NFAC Test Planning Guide January 2016 Page 1

Overview

The National Full-Scale Aerodynamics Complex (NFAC) facility consists of the 40- by- 80- Foot Wind Tunnel, the 80- by 120-Foot Wind Tunnel, and the Model Preparation Building.

The NFAC is managed and operated by the US Air Force Arnold Engineering Development Center (AEDC). Test inquiries should be directed to the NFAC Deputy Director, mailto:ARC- NFAC-DeputyDirector@mail.nasa.gov.

This intent of this guide is to assist customers who are preparing to test at NFAC. Please use the Guide as a general reference for information about the facility, systems and the NFAC test process. Specific facility details have been intentionally omitted for brevity.

Detailed information required for test planning will be provided through the NFAC Test Director assigned to the project. Every effort has been made to incorporate the most up-to-date information in this document. However, systems, procedures and forms are frequently updated and revised. Customers should check the revision level of this copy, and request the latest version before initiating a project. This document replaces the 1993 version of the Test Planning Guide in wide use when NFAC was operated under NASA management.

The NFAC Test Process

Planning for a test at NFAC begins after discussions between the Customer and NFAC management demonstrate the feasibility of safely conducting the experiment at NFAC within an acceptable timeframe.

The NFAC staff approaches every test as a unique effort to be planned and executed in collaboration with customers and stakeholders acting with NFAC personnel as one team.

Customers should be aware that sound engineering and system safety analyses take precedence over the general guidelines presented in this document. Safety of personnel and facility will always be given precedence over schedule.

Generally, only United States citizens are allowed in NFAC facilities. Early notification is required to obtain State Department approval for non-U.S. citizens involved in experiments at NFAC.

NFAC Staff will provide a Rough Order of Magnitude (ROM) cost estimate to the customer before beginning a project. DoD customers must reimburse AEDC for the actual direct costs, which may be higher or lower than these estimates. Other government agencies and commercial customers will be charged direct costs, plus a surcharge established by the Commander of AEDC. Funds must be received in advance of NFAC incurring the costs. Any remaining funds will be returned to the customer at the end of the project after the Air Force financial analysts have completed their reconciliation.

Before a proposed test can be confidently scheduled, the NFAC staff must examine the effect of the test on the rest of the NFAC schedule. With the cooperation of the Customer, the proposed test is studied and assessed, resources are estimated, and test duration is determined. At the end of this process, the test is integrated into the NFAC Master Schedule if Customer funding is available. The objectives of this process are to more accurately estimate the resources and costs associated with a potential test and develop a more accurate test schedule.

NFAC facilities and staff support many customer programs, so maintaining the facility schedule is crucial. The end date of a test window may not be extended if milestone dates are missed. NFAC will do its best to honor schedule commitments, but tests of national urgency must be given priority.

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Acronyms

AEDC Arnold Engineering Development Complex CFD Computational Fluid Dynamics DAS Data Acquisition System DNE Do Not Exceed EU Engineering Units HA Hazard Analysis IFC Induction Frequency Control LAN Local Area Network NFAC National Full-Scale Aerodynamics Complex PSI Pounds Per Square Inch POC Point of Contact RPM Revolutions Per Minute SoC Statement of Capabilities SoF Safety of Flight TRR Test Readiness Review TSR Test Safety Review USB Universal Serial Bus V/STOL Vertical/Short Take-Off and Landing

1. Introduction

The National Full-Scale Aerodynamics Complex (NFAC) is a unique facility primarily used for determining aerodynamic and acoustic characteristics of large-scale and full-scale rotorcraft, fixed wing and powered-lift V/STOL aircraft, as well as testing of wind turbines, parachutes, trucks, and other unique test articles. The facility is located at Ames Research Center, Moffett Field, CA, and is managed and operated by the U.S. Air Force’s Arnold Engineering Development Complex (AEDC).

The NFAC is comprised of the largest wind tunnels in the world, the 40- by 80-Foot

Wind Tunnel and the 80- by 120-Foot Wind Tunnel. The 40- by 80-Foot Wind Tunnel has a closed test section with semicircular sides and a closed-circuit air return passage. The 80-by 120-Foot Wind Tunnel is a non-return tunnel with a closed test section that is rectangular in cross-section. The two test sections share a common fan drive system. By adjusting the position of vane sets, the airflow can be directed through one test section or the other (40x80 or 80x120). The air in the tunnel is driven by six 40-foot diameter, 15-bladed, variable-pitch fans, each powered by a 22,500-hp motor. The maximum speed in the 40- by 80-Foot Wind Tunnel test section is 300 knots, while the maximum speed in the 80- by 120- Foot Wind Tunnel test section is 100 knots.

Actual test section dimensions for the 40- by 80-Foot Wind Tunnel are 39 feet high, 79 feet wide (at the horizontal center line), and 80 feet long. The test section dimensions for the 80- by 120-Foot Wind Tunnel are 79 feet high, 118.3 feet wide, and 170 feet long. Both the 40- by 80- and 80- by 120-Foot Wind Tunnel test sections are lined with sound-absorbing material to permit acoustic and aerodynamic data to be acquired simultaneously.

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There are numerous goals that we strive to meet during each test program including technical, financial, and schedule objectives. All of these are extremely important, but paramount to these objectives is providing a safe work environment through all operations for all personnel. The primary technical objectives include execution of the test program in its entirety, achieving all planned configurations and conditions, and acquiring experimental data of quality and quantity that meets or exceeds our customer’s needs.

Customers are required to provide NFAC staff with analysis and documentation to demonstrate that the candidate test article is properly qualified for the testing in the NFAC.

The purpose of this Test Planning Guide is to describe the NFAC Test process and explain the requirements and expectations for analyses and documentation associated with hardware to be tested in these facilities. A description is presented for Customer-furnished documentation related to integrity of model design, fabrication, and safety. Safety considerations must encompass all aspects of the project from planning through test operations and hardware removal. It is important to note the milestones for delivery of information to NFAC outlined in this document. Failure to meet these milestones will jeopardize the entire test because it is never easy to move test windows when the tunnel schedule affects multiple customers. The NFAC Test Director may have limited ability to mitigate the effect of minor milestone deviations during the planning process.

2. NFAC Test Process

The National Full-Scale Aerodynamics Complex (NFAC) is frequently used for tests aimed at maturing low technology readiness level concepts, so facility modifications and unique hardware and software are often required. Successful tests at NFAC may take more than six to twelve months to adequately prepare, depending on complexity. Customers should plan accordingly and involve NFAC personnel as early as possible.

NFAC, like all facilities at the U.S. Air Force’s Arnold Engineering Development Complex (AEDC), follows a standard process for Test and Evaluation Project Management.

The Air Force periodically solicits feedback from Customers during the test project in order to improve service, with a final meeting at the end of the test to allow the Customer team to provide feedback in person. There are four defined project phases in the AEDC test lifecycle, with analysis, by both the Customer and NFAC, being an essential element of each phase.

2.1 Planning Phase

The Planning Phase typically begins with a test inquiry. NFAC Test inquiries can be sent to AEDC, but are generally directed to the NFAC Deputy Director at mailto:ARC-NFAC- DeputyDirector@mail.nasa.gov. If the NFAC facilities are appropriate for the experiment, the customer will be asked to submit a Test Request (see Appendix) that should include customer information, prioritized test objective information, general instrumentation and software requirements, specialized test utilities or instrumentation requirements, a tentative run schedule, and the test window required from earliest start to latest acceptable completion. NFAC management will prioritize tests based on national interest and urgency.

Test schedules will be determined based on this priority and the availability of resources.

The test window includes all test specific installation and removal time.

NFAC Staff will provide a Rough Order of Magnitude (ROM) cost estimate to the customer before beginning a project. DoD customers must reimburse AEDC for the actual direct costs, while other government agencies and commercial customers will be charged direct costs plus a surcharge established by the Commander of AEDC. The actual costs may be higher or lower than the ROM estimate provided. Funds must be received in

NFAC Test Planning Guide January 2016 Page 1 advance of incurring the costs. At the end of the project, any remaining funds will be returned to the customer.

Once a test is accepted by the NFAC and funded, a Test Director is assigned to the project. It is the Test Director's responsibility to ensure that the Design and Fabrication, Test Execution, and Reporting phases of the experiment are all performed safely and effectively, and follow good systems engineering practice. The Test Director will coordinate with the Customer during this initial Planning Phase to gather information required to generate a feasible milestone schedule for the test program from test plan development through execution and test close out. Building on this information, a cost estimate more realistic than the ROM will be generated, and stakeholder roles and responsibilities will be clearly defined.

The Test Director will create a summary of the test scope, schedule and cost estimate in a document called the Statement of Capabilities, or SOC. The SOC defines the baseline project plan and will proved a qualitative assessment of risk to the test program. The SOC will be signed by all stakeholders, and updated as necessary whenever the baseline plan changes significantly. A Test Change Request will be used to document changes that affect cost, schedule, scope, or safety agreements documented in the SoC.

2.2 Design and Fabrication

During this phase, a detailed test plan is generated, technical and safety reviews are conducted, and models and other required materiel are fabricated as required. Additionally, a thorough assessment of cost, schedule, technical and safety risks is conducted, and risk mitigation plans are developed. One or more Technical Review Board (TRB) meetings will be held during the test planning phase in order to establish that there are clearly defined success criteria for the experiment, and that plans have been made with sufficient technical rigor to ensure they are met. The Customer should expect to provide information and support this effort as requested by the Test Director.

Testing in the NFAC wind tunnels, as in any wind tunnel, involves risks to the safety of personnel and hardware. Our goal is to identify all of these risks for a particular test, and implement measures to mitigate or control them to a reasonable and manageable level so that a safe environment and operations are established. This is best accomplished when safety is factored into the experiment design and development from the very beginning.

The NFAC Test Director is responsible for ensuring that required test documentation is developed using generally accepted engineering methods. The Customer should make sure documents are available for review by NFAC representatives as scheduled with the Test Director. The Test Director will ensure that they are reviewed in a timely manner, and that NFAC management knows and understands the risk level being accepted to perform the experiment. For these reasons, the Customer is encouraged to seek advice and share draft documentation with the Test Director early and often.

In order to clearly identify and convey risks, a System Safety Analysis will be performed and included in the Test Plan documentation. The NFAC Chief Engineer, Test Director and System Safety Engineer should jointly determine what level of System Safety Analysis is required for the test. The depth and scope of the analysis is based upon the complexity of the test and obvious level of risk involved. It is the NFAC Test Director’s responsibility to ensure the analysis is performed in conjunction with the NFAC System Safety Engineer and members of the test team, including Customer personnel. A copy of the hazard severity and probability matrix applicable to NFAC tests is included in the appendix.

In order to conduct the test in a collaborative manner, the Test Director will schedule meetings as appropriate for the test. Several key meetings will occur before operations begin. Customer personnel are encouraged to participate on site if at all possible to ensure the meetings are as productive as possible, and to help build team cohesion. The Customer is expected to provide planning documentation as outlined below prior to the planning meetings. To meet the test window, it is critical that the documentation is provided when

NFAC Test Planning Guide January 2016 Page 1 requested. The test window will be compromised if NFAC personnel are not given sufficient time to implement systems based on this documentation.

The Test Director will schedule an Initial Test Planning Meeting with the Customer to review requirements, clarify roles and responsibilities and identify action items. Two weeks before this meeting, the Customer needs to provide detailed information about topics covered in the Test Request: test objectives, draft instrumentation and software requirements, and run schedule. In general, at least two additional Test Planning Meetings will be held before tunnel entry. The Customer should deliver draft versions of key documents four weeks prior to the second planning meeting. A draft version of the System Safety Analysis should also be available for this meeting. Draft documents should contain all necessary information, but do not need to be reviewed, or in final form. Final versions of the key documents should be delivered four weeks prior to the third planning meeting. Key documents, at a minimum, include the Instrumentation Requirements, the Software Requirements, and the Design Analysis Report. The NFAC Test Director will work with the Customer to establish the complete list of key documents, their content, and the due dates required to maintain schedule.

Configuration Management (CM) is an essential part of successful testing, and NFAC Test Directors are responsible for maintaining CM control during planning and testing activities. A Test Change Request (TCR) will be used to document changes that affect agreements documented in the SoC, hardware, instrumentation or software requirements, implementation methods, or design or safety analyses.

Air Force regulations require the many hardware components forming the NFAC Data Acquisition System to be an isolated network. Customer supplied data systems also may be used, but coordinating multiple data systems may be difficult. Typically, only analog interfaces are allowed between the NFAC data system hardware and non-NFAC hardware, and this may complicate data timing alignment. In addition to connections to the NFAC DAS network, U.S. Air Force guidelines also govern data system operations including access to the system, and the transfer of data from the NFAC DAS to the Customer. Only authorized NFAC personnel may transfer data to the Customer, and no USB memory sticks are allowed in the Control or Computer Rooms. Customers wishing to monitor data acquired on the NFAC DAS during test operations must be U.S. citizens and complete the “NFAC Data Acquisition System Security Agreement” and the “Request For Access to NFAC Data Systems” forms located in the Appendix. Since it may take several weeks to process these requests, the Customer is encouraged to submit these forms as early as possible.

An isolated Local Area Network (LAN) is available for the Customer within the Control and Computer Rooms, and a block diagram of all hardware to be connected to it must be developed and submitted for approval. All wireless network connectivity must be turned off in the Control and Computer Rooms. Access to the World Wide Web will be available to the Customer outside of these rooms in the Customer office area.

At least two design reviews will be scheduled when significant hardware development is required. Preliminary Design Reviews (PDRs) are to ensure that all requirements and operational considerations have been incorporated appropriately, and Critical Design Reviews (DRCs) are to ensure that fabrication, check out, and test operations can be accomplished as designed.

The Customer will be required to perform component and system level testing before shipping hardware to NFAC. While complex test hardware may be assembled in the NFAC model preparation area prior to installation in the test section, this area is not approved for validation of Customer supplied systems. Hardware delivery dates to NFAC will depend on the amount of assembly and system checks required before installation in the NFAC test section. Also, complex test hardware may require extensive end-to-end checks after installation in the test section. The NFAC Test Director will help detail the quality assurance checks required, and how much time to allow between installation and the start of test

NFAC Test Planning Guide January 2016 Page 1 operations. The Test Director will factor these considerations into the milestone schedule included in the SOC. Air Force directives require the NFAC Test Director to ensure adequate consideration is given to safety and data quality, so involving NFAC personnel in the pre-delivery calibrations and hardware acceptance testing is critical to maintain schedule.

Instead of extensive, pre-defined model design criteria, NFAC policy is to establish hardware requirements based on thorough system safety analysis techniques. General guidelines for design are presented later in this document, but the Customer should be aware that final requirements might be more or less stringent based on the system safety analysis. It is always best to work with the NFAC Test Director early to ensure test hardware and software is validated for use in the NFAC efficiently.

A test Safety Review Board (SRB) will be held prior to test hardware installation to summarize test specific hazard analyses, and the controls and countermeasures that will be implemented. The status of safety related action items that need to be closed out prior to test operations is also presented at this review.

The Design and Fabrication phase typically ends after the test crew has successfully passed the first Test Readiness Review. Test Readiness Review Part 1 (TRR 1) will be held shortly after the TSR. TRR part 1 demonstrates to Customer and NFAC management that the test preparation is sufficient to begin installation of hardware into the test section. Copies of the Test Readiness Review sign-off forms are included in the appendix.

2.3 Test Execution Phase

This phase includes test article installation in the facility, post-installation system checkout and calibration runs, completion of the test run-matrix, and removal of the test article from the test facility. All test efforts associated with this phase are accomplished during the calendar window assigned on the NFAC facility schedule. The standard NFAC schedule provides 80 hours during each two-week period. The exact work schedule will be determined after consideration of all test requirements such as access to special utilities or personnel, and coordination with concurrent NFAC activities. It is important to plan all test activities carefully to ensure the calendar window is used productively. For this reason, it is important to work with the NFAC Test Director to realistically estimate the time required for model changes and run matrix execution, and allow some budget for Lost Test Time due to wind tunnel and test article problems.

The NFAC Test Director is ultimately responsible for safe, efficient operations at NFAC, and will serve as the primary point of contact for all Customer communications. It is important that all Customers know and understand the hazards associated with testing at the NFAC facility. Customer personnel on-site during the test execution phase will receive appropriate safety orientation training upon arrival at NFAC. Personal Protective Equipment (PPE) such as gloves, eye, and ear protection will be made available for Customer personnel. Steel-toed work shoes must be provided by the Customer if required. The Test Director will provide training for test specific Emergency Operating Procedures before operations commence, and hazards associated with each run will be discussed during pre-run briefings.

Test articles are generally lifted into the NFAC wind tunnels using large cranes operated by an installation crew following engineered procedures. These procedures need to be thoroughly reviewed and are documented in the lift plan. All hardware and rigging for critical lifts must be independently certified within one year of the lift. This applies to all Customer supplied lifting hardware, and cannot be done on-site at NFAC.

Once the test article has been installed on the model support system, control and instrumentation cables and model utilities can be routed. Methodical end-to-end checks must be completed to ensure the integrity of all data and control wiring, and proper

NFAC Test Planning Guide January 2016 Page 1 operation of all utilities. Data acquisition and data reduction software must be validated for all research and safety of flight parameters. This effort is critical to both test safety and data quality, and solidifies understanding of the experimental set up for effective crew training, so it must not be rushed. Another Test Readiness Review is held to finalize the completion of this effort and gain permission to commence operations.

NFAC refers to these operational readiness reviews as TRR part 2, and complex tests may require more than one when significantly different operational phases are involved. For instance, one operational test readiness review for a helicopter rotor test may be held prior to conducting aero tares, another before hover testing, and one more before beginning forward flight operations. These readiness reviews may be combined or held individually at the discretion of the test team based on their readiness level.

Customer personnel should expect a disciplined atmosphere in the control room during test operations. Key personnel responsible for decisions affecting safety and program objectives during the run will be stationed in the control room. Two engineering work stations are available in the control room for evaluating recently acquired data to inform run matrix decisions. Additional work stations are available in the computer room for more in depth program analysis. The lead Customer representative will coordinate with the NFAC Test Director to ensure programmatic objectives are being met, but it is the NFAC Test Director’s responsibility to ensure safe efficient operations. The Test Director will coordinate and supervise all team operations during wind tunnel runs.

Configuration Management (CM) will be more heavily utilized during the test execution phase. The NFAC Test Director will ensure Test Change Requests (TCRs) are used to keep track of the modifications to instrumentation, hardware and software that are required to ensure efficient operations. Test Discrepancy Reports (TDRs) will be used to track resolution of anomalous operations. Any TCRs or TDRs that substantially affect that content of the signed Statement of Capabilities (SoC) will trigger a revision of the SoC with a corresponding signature cycle. SoC revisions may also be triggered by multiple TCRs and TDRs that aggregate to a significant change.

Test Review Board (TRB) meetings will be convened by the Test Director as required to address issues related to safety or technical merit of the test. TRB meetings are chaired by the NFAC Chief Engineer or designee, and require cognizant test and facility representatives, along with appropriate technical experts. As an example, a TRB meeting may be required when unanticipated vibratory loading triggers safety of flight limits, preventing a key test condition to be reached. TRB personnel will be allowed adequate time to review technical analyses or proposals prior to the meeting.

Test operations will be stopped once the run matrix has been satisfied, or as necessary to ensure all test hardware is removed by the end of the allotted test window.

2.4 Reporting Phase

This phase commences upon completion of the test execution phase and continues through completion of the prescribed test report for the project. Air Force policy requires the generation of Quick Look test reports during the Test Execution Phase, and a summary report at the completion of the experiment.

3. Test Process Documentation Test programs conducted at NFAC are generally complex in nature, requiring clear, extensive verbal and written communication. The documentation discussed in this section should be a natural consequence of clear and timely communications as plans for the experiment progress. Documents provided by the customer will be reviewed by NFAC and questions will naturally arise. This review cycle is fundamental to building a cohesive team

NFAC Test Planning Guide January 2016 Page 1 that understands the experiment well enough to integrate the many systems that must come together for safe, efficient operations.

The unique research done at NFAC may take as much as six to twelve months to adequately plan. The Test Director will maintain records of the test development process, including minutes and action items from meetings. In general, draft versions of documents should be made available to NFAC four weeks before the second Test Planning Meeting, and final versions should be submitted four weeks before the third Test Planning Meeting.

Specific test planning meeting and documentation delivery dates will be coordinated with the Customer and included in the milestone schedule included in the SoC. Documents relating to requirements, test plan development, safety and design analyses are of particular interest and may include some or all of the following:

3.1 NFAC Test Documentation Outline

Test Plan & Test Requirements Documentation Programmatic and Operational Requirements

Test Objectives and Schedule Requirements Customer versus NFAC Responsibilities Prioritized Run Schedule (test conditions) Security Requirements Photo/Video Requirements Test Hardware Description

• Hardware Assembly Inspection Requirements and Checklists

• Interface Specifications (mechanical, electrical, data system)

• Utilities Requirements (electrical, water, air, etc.)

• Installation & Removal Plan / Lifting & Rigging Requirements

Operating Procedures

• Predicted Operational Envelope

• Manpower Requirements

• Pre-Run/Post Run Checklists

• Maintenance/Inspection Procedures

• Emergency Procedures

Instrumentation and Data Acquisition Requirements Instrumentation Description

• Prioritized Measurements List

• Voltage-to-Engineering Unit (EU) Conversion Requirements

• Calibration Requirements

Customer Data Acquisition System (DAS) Description (if applicable)

• Required Inputs from NFAC

• Interface to NFAC Systems (if applicable)

NFAC DAS Test Specific Data Reduction Requirements Data Reduction Equations To Be Implemented Real Time Data Monitoring Requirements Safety of Flight Monitoring Requirements Post Point Processing Requirements Special Requirements (Stand Alone Programs)

Design Analysis Documentation Predicted Loads Report Stress Analysis Report (including fatigue considerations if applicable) Dynamic Stability Analysis Fragmentation Energy Analysis Fatigue Analysis Safety Factor Summary Table

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Monitoring Requirements & Redline (Do Not Exceed) Limits Certifications, Inspections and Qualification Tests Safety Analysis Documentation

Planning Meetings and Review Minutes Test Planning Meetings (Adjusted as required)

• Initial Test Planning Meeting

• Second Test Planning Meeting (roughly six months out)

• Third Test Planning Meeting (roughly three months out)

Preliminary Design Review Critical Design Review Test Safety Review Test Readiness Reviews

3.2 Test Plan & Test Requirements Documentation

Many details must be planned and organized to successfully conduct a test in the

NFAC wind tunnels. The outline above should be used as a guide instead of being considered comprehensive. The test team should tailor the documentation to meet the needs of the test. The NFAC Test Director and Customer POC will coordinate planning efforts to ensure that safe, reliable and effective test operations result.

3.2.1 Programmatic and Operational Requirements

Careful planning of schedule milestones to ensure timely delivery of information and hardware is critical to successful planning. The following notional timeline will generally provide enough review and iteration time for moderately complex experiments at NFAC.

Once established for the project, failing to meet milestones may result in reduced test operation time, or even loss of the entire test window.

Figure 3.1 Notional timeline for a moderately complex test at NFAC.

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It is very important to specify all interfaces between NFAC and Customer hardware or software when planning and documenting the test. Key areas include the model interface with the support system to be used during the test, the instrumentation interfaces, and data acquisition systems interfaces. The NFAC Test Director will be able to provide support hardware drawings for coordinating model installation.

3.2.2 Instrumentation and Data Acquisition Requirements

Instrumentation and data acquisition system coordination requires careful thought and planning to ensure the data accuracy meets Customer requirements. Models tested at NFAC are generally large, and careful consideration should be given to instrumentation wire routing and junction locations. Wire runs are very long, so provisions for grounding instrumentation shields should be coordinated with NFAC and provided on the model if necessary. A complete listing of instrumentation measurement requirements with anticipated ranges, transducer accuracies, excitation requirements and desired voltage-to-EU conversion methods is essential.

Software requirements are essential because of the need to compute parameters from the Engineering Units. Equations used for computing these derived parameters are programmed into the NFAC DAS to provide Real Time Monitoring for setting test conditions, or monitoring safety of flight limits. Reduced data parameters computed during post-point processing allow data quality assessments and decisions regarding future test conditions to be made. Provisions can also be made to incorporate stand-alone programs on NFAC DAS computers for more complex post-point processing requirements. Alternately, post-point processing can be done on Customer provided computer hardware, but this hardware normally is not connected to the NFAC DAS network.

An isolated network links the many hardware components forming the NFAC DAS.

U.S. Air Force guidelines govern data system operations including access to the system, connections to the NFAC DAS network, and the transfer of data from the NFAC DAS to the Customer. Only authorized NFAC personnel may transfer data to the Customer, and no USB memory sticks are allowed in the Control or Computer Rooms. Customers wishing to monitor data acquired on the NFAC DAS during test operations must be U.S. citizens and complete the “NFAC Data Acquisition System Security Agreement” and the “Request For Access to NFAC Data Systems” forms located in the Appendix. Since it may take several weeks to process these requests, the Customer is encouraged to submit these forms as early as possible.

While NFAC data acquisition systems are typically used to acquire and process measurement signals, Customer supplied data systems also may be used. Coordinating multiple data systems may be difficult, and careful planning must begin early. Typically, only analog interfaces are allowed between the NFAC data system hardware and non-NFAC hardware, and this may complicate data timing alignment. An isolated Local Area Network (LAN) is available for the Customer within the Control and Computer Rooms, and a block diagram of all hardware to be connected to it must be developed and submitted for approval.

All wireless network connectivity must be turned off in the Control and Computer Rooms.

Access to the World Wide Web will be available to the Customer outside of the Control and Computer rooms in the Customer office area.

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3.3 Design Analysis Documentation

Test articles must be designed and built to safely withstand the maximum loads anticipated during the test, and the design analysis documents should demonstrate a logical, comprehensive approach to ensuring this objective. The requirements and methods used for qualifying hardware for testing in the NFAC are very similar to those used to qualify for experimental flight tests. Substantiation methods may include analyses, static and/or rotating tests, material and coupon testing, and previous wind tunnel, ground, or flight test results. The NFAC has no “standard set of requirements” for the precise content and presentation of analyses and substantiation reports beyond the need to be thorough and robust. Analyses that follow accepted industry practices and engineering standards, and demonstrate sound judgment will be acceptable. The Customer and NFAC Test Director should agree on the specific analyses and supporting documents to include in the design analysis package.

NFAC personnel, or an independent third party, will review analyses and reports to ensure NFAC requirements are satisfied. The inevitable question-and-answer review cycles that occur between NFAC and Customer personnel should be approached as a team building exercise that helps NFAC fully understand the test article capabilities and limitations. This understanding will help NFAC plan and implement a safe experiment that proceeds as efficiently as possible. Ultimately, monitoring limits will be programmed into the Safety of Flight (SoF) System to ensure that loads on critical model components will not exceed either steady state or oscillatory allowable load limits. SoF monitoring limits shall be based on appropriate structural limits, not anticipated load levels during the test. These “Redline” or “Do Not Exceed (DNE)” limits must be directly traceable to the design analyses supplied by the Customer.

The Customer is responsible for preparing analyses and supplying other supporting evidence such as material certifications, inspections and qualification test reports. The NFAC Test Director will be available to provide guidance during development of this documentation and is responsible for either reviewing it on behalf of NFAC staff, or ensuring that it receives the appropriate level of third party review before being accepted. In order to speed review, the reports should be clear, concise and self-explanatory. They should include free body diagrams, lists of assumptions, engineering calculations, test results and any other information needed to verify the integrity of the model. Analyses should be revised as changes in the test envelope, model design or fabrication developments warrant. Timely delivery of this documentation to NFAC staff can be critical to achieving the Customer’s objectives. The wind tunnel schedule affects many customers, so missing test preparation milestones may directly reduce time for data acquisition.

The following information should be contained in the design analysis documentation:

• List of all planned test conditions or test envelope

• Summary of maximum global (total) loads and corresponding test conditions

• Summary of maximum component loads and corresponding test conditions with an explanation of how they were derived

• Comprehensive Summary of all factors of safety – for all model components, based upon conservative calculations

• Description of safety of flight system requirements - monitoring requirements with specific sensor/channel information, caution limits, red-line limits, etc.

with an explanation of how they were derived.

• Detailed stress analyses of model components (static strength) – see below

• Detailed analyses of total loads acting on model support struts

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• Detailed analyses of model component oscillatory limits (endurance/fatigue limits) – see below

• Model drawings – complete set (may be included as appendix)

• Summary listing of fatigue life budgets, if appropriate, for critical components in the load path

• Acceptance test results for any testing performed (static proof-loading, rotating/whirl testing, fatigue tests, coupon/material tests, etc.)

• Detailed analyses of extreme operating condition or failure loads and stresses (rotor thrown blade, asymmetric thrust due to engine failure, etc.)

Additional information for major analysis areas is provided below.

3.3.1 Predicted Loads Report

Thorough documentation of the loads expected during the test will form the foundation of the design analysis. The factor of safety numbers provided in the stress analysis will be based on the loads predicted, so it is important to thoroughly document how the load cases are derived, and any simplifying assumptions used. NFAC will review the Loads Report for insight into the anticipated test conditions and perspective on the stress analysis.

3.3.2 Stress Analysis Report

NFAC will review the stress analysis to ensure that adequate safety margins exist for the planned experiment. The entire load path must be analyzed, from the point of load application through the structural elements down to the interface with the wind tunnel model support system. This includes any panels forming the aerodynamic surface of the test article and the fasteners that hold them in place.

The reviewer will generally look for the following attributes in the stress analysis report, and deviations will be discussed with the customer on a case-by-case basis.

• The stress analyses must be comprehensive and the entire load path must be included in the analysis, addressing all components and interfaces in the particular load path.

• Schematics, drawings and free-body diagrams should be used wherever appropriate.

All engineering equations should be shown in generic form and with values inserted.

Resultant safety factors should be shown in the deriving equations and listed in the summary table.

• A minimum factor of safety of 4.0 for ultimate strength, and a minimum factor of safety of 3.0 for yield strength for ductile materials (metals), is required for all model hardware that is not instrumented. This is applicable for rotating and non-rotating components.

• A minimum factor of safety of 2.0 for ultimate strength, and a minimum factor of safety of 1.5 for yield strength for ductile materials (metals), is required for all model hardware that is instrumented such that actual loads can be accurately measured or inferred and monitored during testing. This is applicable for rotating and non-rotating components.

• All components subjected to vibratory conditions shall be shown to have infinite fatigue life after appropriate knockdown factors have been included.

• The loads used to calculate these safety factors should be the absolute maximum loads, i.e. steady-state plus maximum half peak-to-peak oscillatory loads.

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• Certified, flight rated components are generally accepted for use as long as the test operating envelope and applied loads do not exceed the established flight envelope and loads. The analysis must show that the load path in wind tunnel test conditions (vehicle restrained) will be the same as in flight (unrestrained).

3.3.3 Dynamic Stability Analysis

The Customer must show that test articles with rotating components can be operated safely throughout the operating envelope. A dynamic stability analysis for any test that may involve aero-elastic or dynamic instabilities (this includes rotorcraft tests and fixed wing tests where flutter is possible) is required. Modes and natural frequencies that could be excited must be identified and shown to be safely outside of the operating conditions. The corresponding levels of system damping must also be identified. The use of any dynamic damping should be included in this analysis.

The report should document the analysis method used, assumptions made, and the predicted results for the complete test envelope proposed. All model lifting surfaces, propellers and rotors must be analytically demonstrated to be free of aero-elastic instabilities throughout the test envelope. All critical modes of potential dynamic instability must be identified and shown to be completely stable throughout the entire test envelope.

The modes, natural frequencies and damping after installation will need to be verified by either wrap testing, or more thorough shake tests, so the Customer should expect to include time for this in the required test window. Data acquired during wrap tests, shake tests, or checkout runs can be used to identify potential model resonance frequencies that could be excited by operation of a rotor or propeller system. The dynamic stability analysis should be updated accordingly.

This documentation may be included with the Design Analysis Report or prepared as a separate document, per Customer preference. The Dynamic Stability Analysis results shall be incorporated into the system safety analysis.

3.3.4 Fragmentation Analysis

NFAC wind tunnels are frequently used to test vehicles with onboard energy sources such as turbine engines, rotors and propeller systems. Portions of the NFAC test section walls are lined with armor plating, and an assessment of danger to personnel resulting from failure and subsequent release of high-energy fragments is required. The energy level, direction and range of these fragments must be determined in order to implement mitigation strategies if required. NFAC personnel can help the Customer perform this assessment using information such as weights, dimensions and speeds of possible fragments. The Fragmentation Analysis may be included in the design analysis report, or provided separately, and the results shall be incorporated into the system safety analysis. Additional countermeasures will be implemented as required.

3.3.5 Fatigue Analysis

All model components subjected to oscillatory loads should be analyzed for fatigue life or undergo fatigue testing. The preferred design approach is that oscillatory loads will not exceed the infinite life oscillatory load limits for any component. The endurance limit shall be corrected using knockdown factors for Surface, Size, Temperature, and a Reliability of 99.99%. If the standard deviation of the endurance limit for the material is not known, a safety factor of 2 may be used rather than reliability knock down factor. If the infinite-life criterion cannot be met, it should be shown that adequate fatigue life margins exist for the expected duration of test operations. NFAC will allow the component to be used during operations for up to one half of the predicted fatigue life before change out is required. Fatigue cycle counting methods may be employed during test operations if appropriate. The cycle counting system must be provided by the Customer.

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If model hardware has been tested previously, load and time usage history must be evaluated for possible model component fatigue damage. In general NFAC allows operation in test up to half of a production part’s change out life. If a component has suffered fatigue damage, the Customer must define appropriate fatigue limits that incorporate a fatigue damage knock-down factor.

If the fatigue life status of a previously tested model component cannot be determined, it may be estimated using methods approved by the NFAC. The NFAC Test Director should be consulted in this case. If the fatigue life cannot be confidently shown to be sufficient for the testing planned, the component shall not be tested and new/replacement parts shall be required.

3.3.6 Safety Factor Summary

The entire suite of design analyses is a critical resource during complex tests, and is referred to frequently. In order to facilitate quick reference, a section summarizing the design analyses shall be provided. This summary should be in tabular form listing the critical components and their corresponding factors of safety, along with where the analysis can be found, and what the failure mode is.

3.3.7 Monitoring Requirements

Complex tests typically require active load monitoring to ensure critical components are not over stressed. Safety of flight parameter limits must be based on traceable hardware design limits or component test data, and not on load levels expected during the test. The Customer should realize that these limits must be programmed into the Safety of Flight Data Acquisition System (SoFDAS) and verified, channel-by-channel. This means that the various design analyses must be completed early enough to keep SoFDAS programming and verification off of the schedule critical path. Ideally, columns for warning and DNE limits would be included in the Safety Factor Summary described above.

3.3.8 Certifications, Inspections, and Qualification Tests

It should be evident that materials use during model fabrication must have properties that meet or exceed the material properties used in the design analyses. Material certifications shall be provided for all critical components that could result in catastrophic failure. The Safety Factor Summary shall include notation stating that material certifications are required for these components.

Inspection is a valuable tool for determining the structural integrity of test hardware and aiding qualification of a test article for NFAC testing. “Inspection” as used here includes searching for cracks or flaws in model parts, checking dimensions and contours for accuracy, or inspecting for proper assembly of critical components. Inspections may be required for critical structural parts or assemblies identified by the hazard analysis or design analysis process. If required, the Customer should ensure that critical inspections are performed and documented as the test article is being fabricated and assembled. Records of these inspections should be included in the Design Analysis documentation. The Test Director will rely on this as evidence of the test article’s integrity. The Test Director and Customer should plan for critical inspections that may be required during model build-up, or at intervals during test operations.

Qualification tests, including static loading and material/coupon testing are encouraged wherever possible and appropriate. New rotor and propeller systems must be whirled to 110% of their maximum rotation speed before being tested in NFAC wind tunnels.

While other acceptance tests are not firm requirements for a test article to be cleared for testing in the NFAC, they are very valuable and will reduce overall risk. The hazards analysis will take into account any qualification tests performed, often leading to reduced

NFAC Test Planning Guide January 2016 Page 1 levels of analyses, monitoring or inspections required. In some cases, qualification testing can be used to substitute for component stress analyses.