Overview
After my first semester of aerospace engineering, I came across Dr. Raymer’s Aircraft Design textbook. I picked the book up during winter break, and I was hooked - I read the thing from cover to cover, and decided to follow one of his pieces of advice to become an aircraft designer: join a design competition.
The RFP for the 2023 AIAA Individual Undergraduate Aircraft Design Competition called for the design of a New Efficient Water and Terrestrial (NEWT) aircraft, a STOL amphibian to fly a 250 nautical mile mission carrying 19 passengers. As a response to it, I designed the AirSChooner-105 P/C (105 was a homage to USC’s introductory aerospace class, AME 105, and P/C the designation for passenger and cargo).
The Report
My final submission is embedded (and downloadable) below.
The Work
This was my first aircraft design project, and I used it as an opportunity to apply directly what I had learned with Raymer’s text. I started with an overview of similar aircraft, including their geometry, performance, and aerodynamics. This was my first time reading the famous Jane’s All The World’s Aircraft, and the data was compiled into a table. This served to guide the following sizing works and was used to compare the performance at the end of the design.
For sizing, I used the method of weight fractions with the suggested fractions in Raymer’s text. Mission analysis was done with basic Breguet formulations, and a design takeoff gross weight was calculated iteratively with a power-fit for empty weight and the detailed payload weights laid out in the RFP. I had time for some basic design studies, such as cruise velocity influence in W0, as shown to the left. These were greatly improved in my 2024 entry, StratoSOL, and are now much higher-fidelity with DSAeroTools.
The layout was arguably the best part of my work in this report. It started with an estimation of the required fuselage size. I made a simple planform view of the cabin with SolidWorks, using the proposed seat pitch and widths in the RFP and including space claim for a lavatory and a reasonably-sized cockpit. During this process I also read Roskam’s Airplane Design series for the first time, getting inspiration from the cabin layouts of similar aircraft.
The layout also included provisions for several different components of the aircraft, and was done using OpenVSP. Namely, the propulsion system was properly sized, including the required fuel volume, and appropriate space claim was allocated in the wings (green containers on the left iso-picture). The aircraft’s waterline was also considered when designing and placing the wingtip floats and the hull’s cross-section, done with OpenVSP’s sectioned volume capabilities. Other practical considerations were analyzed, such as tail striking, loading/unloading provisions, etc.
The report also featured analysis of various different aspects of the aircraft. In the aerodynamics department, the analysis methods were primarily DATCOM-based, as detailed in Raymer. A study of high-lift devices was held -and thus the required level of complexity for those devices given the required maximum lift coefficient - drag buildups in a few different configurations, and variations in key parameters with Mach number were investigated.
My experience in the AeroDesign Team also helped: for stability and control analysis, an AVL model guided most of the small but critical design decisions for weight and balance. Some custom tools were also developed for this, including a W&B spreadsheet that I would later use again for the 2024 design competition.
A basic propulsion analysis was also conducted. Raymer provides a series of representative thrust diagrams for different engine types, and recommends scaling them appropriately. This was the gist of the propulsion analysis for AirSChooner, taking into account engine installation and miscellaneous losses to the total thrust versus altitude and Mach number.
Lastly, I conducted some basic cost analysis using cost estimating relations (CERs) detailed in Raymer’s text. Namely, RAND’s DAPCA IV model was used (I later learned this method bases its estimates off of millitary aircraft alone, so the analysis likely overestimated the costs associated with engineering development of the aircraft).
A Positive Surprise
To my surprise, this report was awarded second place in the competition! It now lives in the AIAA’s website. As a nice bonus, I received a fancy certificate and some good money. Good stuff!
Reflections
In hindsight, there is a lot I could have done better in this report.
Firstly, though I do believe this aircraft would meet the performance requirements (I’ve spent some time re-analyzing this aircraft with my newfound knowledge and tools, including DSAeroTools) it is by no means optimized. Arguably because I had not spent the time developing the tools or procedures for proper performance analysis… but I would learn this later on.
I also later realized I was straight up missing some diagrams. I had no CG excursion diagrams, nor did I have a payload-range diagram. More work could also have been done with a simple theoretical presentation on the performance analysis (and results) of the airplane.
Despite these shortcomings, this report did its primary job of getting me very excited about aircraft design. It is still what I am passionate about today, and I would later participate in this competition again in 2024, and plan on doing so until I cannot anymore (when I graduate with my M.S.!)