F15_Flow_Rake_SOW_v2.pdf

RFP # 80AFRC18R0011

Statement of Work

Title: NASA F-15B Flow Rake Design and Fabrication

National Aeronautics and Space Administration Armstrong Flight Research Center Edwards, California

Table of Contents

1.0 Background

2.0 Objectives

3.0 Requirements

4.0 Deliverables

5.0 Period of Performance

6.0 Travel

7.0 Other Special Requirements and Considerations

RFP/Contract No. SOW Title Date or Version #

1 Background The NASA Armstrong Flight Research Center F-15B test bed aircraft, shown in figure 1, is used to conduct flight research in several areas such as natural laminar flow, advanced air data measurements, and propulsion. Typically, experiments are flown on modified pylons mounted to the centerline store location of the airplane. The workhorse of these modified pylons is the Centerline Instrumented Pylon (CLIP). The CLIP is a modified F-15 centerline pylon that includes a highly swept nose extension and a splitter plate to help isolate experiments from the flow field directly underneath the aircraft. Photos of the F-15B with the CLIP and the CLIP on its loading table are shown in figure 2. The MAU-12 bomb rack has been removed from the CLIP to allow experiments to mechanically interface with the pylon using a tongue which fits inside the CLIP and is secured in place using the forward and aft MAU-12 mounting bolts. An illustration of this tongue/mechanical interface from a previous CLIP experiment is shown in figure 3.

Figure 1. NASA F-15B high-speed research testbed

Figure 2. CLIP (black pylon) mounted underneath the F-15B (left) and close up photo (right)

Figure 3. Illustration showing CLIP/Experiment mechanical interface

In support of current and future flight research using the CLIP, NASA AFRC intends to fly a new, custom design flow rake, hereafter referred to as the rake, installed on the CLIP to characterize the flow underneath the F-15B. The project objectives of the rake flight tests are as follows:

• Measure the local flow speed and direction at multiple locations underneath the CLIP from Mach

0.8 to Mach 2.1

• Measure fluctuating total pressure levels underneath the CLIP from Mach 0.8 to Mach 2.1

AFRC has developed a notional outer mold line (OML) for the rake, shown in figures 4 and 5. Flow measurements will be made using a combination of five-hole conical probes for flow speed and direction, and custom pitot probes to measure fluctuating total pressure levels to estimate turbulence. The rake is a cruciform shape with a vertical leg swept back at 35-degrees and a set of lateral legs located at mid-span of the vertical leg. The vertical leg holds up to five probes while each lateral leg can hold one probe. The rake is intended to be able to translate fore and aft at discrete locations in order to allow for flow measurements to be obtained at different locations underneath the CLIP. In figure 4, the rake is shown in its forward most position.

Figure 4. CLIP and notional flow rake side view

Figure 5. Notional flow rake (CLIP removed)

AFRC has conducted preliminary computational fluid dynamics (CFD) analyses of the rake OML at to investigate the flow quality around the probes. Additional CFD cases are planned to generate aerodynamic force and moment estimates for worst-case conditions in the desired flight envelope for the rake. These aero loads will be delivered to the contractor in a loads definition document at the onset of the contract award.

2 Goal & Objectives The goal of this effort is to have a contractor perform the detailed mechanical design and fabrication of the rake and mechanical interface to the CLIP. Specific objectives are as follows:

• Develop a detailed mechanical design for the rake including the tongue/mechanical interface to the CLIP using the Government provided rake OML as a starting point for the design

• Create a drawing package of the rake design for fabrication

• Develop a finite element model (FEM) of the rake for structural analysis

• Perform a loads and stress analysis showing that the rake has positive structural margins under the Government specified worst case flight load cases

• Fabricate the rake and deliver to the Government

3 Requirements The contractor shall create a detailed mechanical design for the rake using the OML provided by the Government. Any changes in OML deemed necessary to meet structural or other requirements shall be conveyed to the Government at the earliest possible convenience to allow the Government time to assess the effects of the OML changes on the flow field around the probes.

3.1 Mechanical requirements

1. The rake shall mechanically interface with the CLIP using the four MAU-12 bolts in the CLIP

2. The rake vertical arm shall be swept back at an angle of 35 degrees

3. The rake vertical arm shall extend 40 inches below the bottom of the CLIP splitter plate

4. The rake shall be able to hold either type of probe (conical or turbulence) at any of its seven probe locations

5. The rake position shall be ground adjustable in the longitudinal axis (forward and aft)

a. The rake in the full forward position shall place the tip of the top probe 36 inches forward of the first MAU-12 bolt hole in the CLIP (figure 6)

b. The rake in the full aft position shall be 36 inches rearward of the full forward position (figure 7)

c. The rake shall have discrete set points with 12-inch spacing from the forward most position to the rear most position

6. The rake shall be designed to allow for pressure tubing and wiring to be routed up through the upper section of the rake and into the aft instrumentation bay of the CLIP

7. The rake shall contain sufficient internal volume for pneumatic tubing and electrical wiring from the probes

a. 25 lines of 3/16” OD pneumatic tubing

b. Electrical wiring from Kulites

8. The rake shall be designed to allow three accelerometers to be mounted internal to the rake at TBD locations specified by the Government

9. The rake shall be designed for ease of disassembly/reassembly to enable quick installation of the probes and routing of the probe pneumatic tubing and instrumentation wiring inside of the rake

10. All rake materials including fasteners shall be Mil-spec certified

Figure 6. Rake in full forward position

Figure 7. Rake in full aft position

3.2 Loads requirements

The rake shall be designed to withstand the aerodynamic and inertial loads cases provided by the Government. Aerodynamic forces and moments will be estimated from CFD analysis of the rake and will be provided to the contractor. Table 1 lists the flight conditions that will be analyzed for aerodynamic loads. Inertial loads are given in table 2. The moment reference center shall be located at the centerline of the rake-CLIP interface mid-way between the forward and aft sets of MAU-12 bolt holes as shown in figure 8. From this reference location, the loads axes definition for this reference is as follows. The x-axis points backwards, the y-axis points to the left side of the rake, and the z-axis points upwards. The rake structure shall be analyzed using the combined aero and inertial loads with the inertial loads transferred from the CG to the reference center. All rake components shall have a positive margin of safety (MS) as defined as:

𝑀𝑀𝑀𝑀 = �𝐹𝐹𝑎𝑎𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖 𝑖𝑖𝑙𝑙𝑎𝑎𝑙𝑙

𝑈𝑈𝑖𝑖𝑈𝑈𝑖𝑖𝑈𝑈𝑎𝑎𝑈𝑈𝑖𝑖 𝑖𝑖𝑙𝑙𝑎𝑎𝑙𝑙� � − 1

where the ultimate load is defined as:

𝑈𝑈𝑖𝑖𝑈𝑈𝑖𝑖𝑈𝑈𝑎𝑎𝑈𝑈𝑖𝑖 𝑖𝑖𝑙𝑙𝑎𝑎𝑙𝑙 = 𝐹𝐹𝑀𝑀 × 𝐷𝐷𝑖𝑖𝐷𝐷𝑖𝑖𝐷𝐷𝐷𝐷 𝑖𝑖𝑙𝑙𝑎𝑎𝑙𝑙

For the rake structure, a factor of safety (FS) of 2.25 shall be used to determine the ultimate load. The contractor shall provide a stress report for the rake documenting the structural analyses and the margin of safety for all components of the rake.

Figure 8. Moment reference center location and axes conventions. Y-axis points into the figure.

Table 1. Aerodynamic loads cases

Case Condition

Mach 0.85 900 psf

Mach 1.2 600 psf

Mach 2.3 1740 psf

Table 2. Inertial loads

Fx Fy Fz

± 1.5g ± 1.5g ± 7.5g

4 Deliverables

4.1 Contractor

The contractor is responsible for the detailed mechanical design, drawings, FEM, stress analysis, fabrication, and material certification of the rake. The contractor shall provide the following deliverables to the Government:

• Slide package for the rake final design review

• Engineering drawings of the rake components and entire assembly in .pdf format

• CAD model of the rake in IGES, STEP, and native CAD format

• Finite Element Model (FEM) of the rake in PATRAN/NASTRAN compatible format and a table of the rake FEM’s mass properties

• Loads and stress report documenting the structural analysis method and margin of safety for all rake components

• Material certifications for the rake and fasteners

• The rake after fabrication is complete, shipped to NASA AFRC

• Rake assembly/disassembly procedure

4.2 Government

The Government shall provide the contractor with the following:

• CAD model of the rake OML in IGES and STEP format

• CAD model of the CLIP OML in IGES and STEP format

• CAD model of the conical and turbulence probes in IGES and STEP format

• Mechanical interface drawings for the CLIP

• Aerodynamic loads estimates

5 Period of Performance The period of performance begins at contract award. Contractor milestones with durations referenced from contract start are show in table 3. After the final design review has been accomplished, the Government will perform a flutter analysis of this design to ensure that it is flutter free in the proposed flight envelope. The flutter analysis is expected to take approximately 1 month. Should the flutter analysis show negative flutter margins, the Government will provide feedback to allow the contractor to iterate the final design to provide positive flutter margins. The Government will also perform CFD analyses of the contractor’s notional rake design if it significantly deviates from the initial OML provided by the Government. The CFD will be used to assess any changes in the local flow field and aerodynamic forces and moments due to the OML change.

Table 3. Contractor milestones

Milestones Time after contract award

Kickoff meeting (telecon) 2 weeks Preliminary rake design review (telecon) 2 months

Preliminary engineering drawings and CAD models delivered to AFRC 2 months

Preliminary FEM model delivered to AFRC 2 months

Final rake design review (face-to-face) 4 months

*Final rake design delivered to AFRC 5 months Final Engineering drawings and CAD models delivered to AFRC 5 months

Final FEM model delivered to AFRC 5 months Final loads and stress report delivered to AFRC 5 months

Rake fabrication complete 9.5 months

Rake delivery to AFRC 10 months

* Pending positive flutter margins from AFRC flutter analysis

6 Travel The contractor shall travel to AFRC for the final rake design review. The contractor may also travel to AFRC at the beginning of the effort to examine the CLIP hardware, if desired.

7 Other Special Requirements and Considerations The Government desires to visit the contractor’s facility for a face-to-face meeting to examine the rake during fabrication prior to delivery.

8 References

1. Drawing # CLIP-00014_D.pdf, CLIP mechanical interface drawing, page 2

2. Drawing # 08072012-.pdf, Dynamic Probe Body for XCQ-062

REVISIONS

Revision Number Date Brief Summary of Changes

1 5/09/2018 Initial version 2 7/26/2018 Updated some figures, added estimated aero loads