Project Summary

My senior project group was presented with an outstanding opportunity to work with MOOG, a major engineering firm here in Buffalo. MOOG has an incredible project history, ranging from Apollo to Formula 1.

Our group was brought in to work with MOOG's aircraft group, which is currently working on an autonomous flight control system for integration with existing piloted helicopters. To start off, MOOG has been working with the R-44 platform. To facilitate this, MOOG has acquired an operating R-44 for flight testing, and an R-44 which has suffered damage from a hard landing rendering it unsafe to fly. The damaged airframe has been stripped and is used for development and simulation of the flight system.

As you can see, this airframe, which has been dubbed "The Iron Bird" is sitting in what is essentially a cluttered garage. MOOG is beginning to bring customers in for demonstration, and so it has begun the process of cleaning up the space. This is where we come in.

Our project had the primary goal of developing a compact, static display stand for the Iron Bird, such that the existing landing gear can be cut away. Reducing the footprint of the Iron Bird is the first phase of the aircraft group's plan to renovate the space into something more presentable.

Load Distribution Problem

Before we could begin sizing our supports, we had to figure out the loading they would be subjected to, and to do this we had to figure out the weight distribution of the Iron Bird. I jumped on this problem the very day we first met with our sponsors and got to take measurements of the Iron Bird in person.

The manufacturer of the R-44 has the pilots manual available for download as a pdf, and this includes a guide to estimating the stock R-44's center of gravity (CG) before any given flight. This is much like any other a CG estimation for any other complex geometry, being a function of the weights and position of each constituent component. Following the provided example, I determined the weight and CG of a stripped, stock, R-44, to within the limits of the handbook. Next, I did some research and made some estimates for the weight and position of the engine, the gear box, and various other components which had been removed from the Iron Bird. I also had to account for the weight and position of various pieces of equipment the team at MOOG had added to the airframe. For added safety, I factored in some extreme dynamic loads, such as a person jumping out of the pilot's seat, or running into the Iron Bird with their full body weight behind them. Using this information, I was able to come up with some very reasonable weight and CG estimations.

The image on the right is the spreadsheet I used to perform these calculations.

After relating the center of gravity of the Iron Bird to the positions we planned to mount our supports, I was able to treat this as a fixed inclined beam problem to determine the reaction forces that the supports would have to resist. Using these reaction force estimates, I ran through some basic stress calculations and was able to provide my group with some ballpark dimensions for the initial sizing of the support design. I performed these calculations assuming we would be using Aluminum 6061-T6, a material I am quite familiar with through my work with UB SEDS, and also a factor of safety of 5, which the group had determined would be appropriate.

Design

For once I actually took a backseat on the conceptual design for this project. My only contributions were just to reduce the complexity of fabricating some of the parts, making sure fasteners were placed appropriately.

The design my group members settled on is a system of three vertical columns, two for the front and one for the rear of the Iron Bird. Each column is sized to withstand the loads on their own, however, each column is complimented by two diagonal struts which help resist bending loads.

The supports clamp onto the root of the existing landing gear, and are anchored to the concrete below. The clamps rest on an adjustable sub-assembly, consisting of a pinned joint on top of a linear screw. This allows for adjustments in both height and angle during installation.

Analysis

I personally took the lead on the analysis of the initial design using ANSYS. Because of my experience with UB SEDS, I am very comfortable using ANSYS for finite element analysis. I prepared the geometry, setup mesh, the contacts, and the boundary conditions, then simulated how the design would behave under the anticipated loads.

The first analysis I performed revealed that some components were slightly undersized and did not achieve our chosen factor of safety of five. I relayed this information to my group, and we increased the diameter of all of our components.

With this new and improved geometry, I performed another analysis in ANSYS, and found we had most likely achieved a factor of safety of five. The model did contain several stress singularities which overestimated the local stresses. I performed some calculations to assure myself that these singularities did not represent the real behavior, and disregarded these singularities.

To ensure that the quality of my model was sufficient, I performed a manual mesh convergence study, and found that the stresses throughout did in fact converge as the mesh was refined.

As a required verification of my analysis, a group member performed finite element analysis in Fusion 360, and found results which closely conformed to my own. By comparing trends in stress distribution and total deformation, we could be certain that our design was mature, and we could move into production.

Fabrication

Myself and another student lead the machining of all the parts that we had the ability to make in house at UB's engineering machine shop. I have quite a bit of experience with the lathe and the mill at this point, so I was also able to teach the rest of my group members the basics.

Since most of our parts are cylindrical, most of our work was done on the lathe. Some basic things were done on the mill, mostly just to drill straight holes.

When all of our parts were done, we sent them over to a local welding company that MOOG has worked with in the past, and had the handful of welded connections done.

We picked up the welded parts and assembled and lubricated everything in a parking lot on campus.

Results

On the right you can see the finished product, installed on the Iron Bird. This came out pretty great, our sponsors seemed very satisfied and they let us know that they were excited to work with more students from UB in the future.

This was an awesome experience for me as a student engineer. I got to successfully apply a lot of things I've learned through UB SEDS onto another large project, and I look forward to applying these skills to more projects in the future.