Guest Lecture: Inlet Design

Today, we learn the basics of aircraft inlet design.

This November, I was asked to provide a substitute lecture to a senior level propulsion class (AEM 408). For this lecture, I attempted to provide the basics of inlet design by discussing the relevant physics and constraints.

Inlet fan face total pressure was introduced as a way to quantify the performance of an inlet and to diagnose common issues.

The concept of boundary layer growth with the inlet’s adverse pressure gradient was reinforced from an earlier Aerodynamics I course.

The lecture notes are available here:

Thanks and best wishes to the UA Aero 2018 Seniors.

Dr. O’Neill


On 27 Sept 2017, I gave a servo lecture to the UA senior design teams.

The lecture notes are at: ServoTalk


Flight Dynamics and Control 1 (AEM 368)

AEM 368 is an introduction to aircraft dynamics including performance and stability and control. Dr. O’Neill taught this course in the Spring of 2017.Example Lectures:

Required Books:

  • Flight Stability and Automatic Control, R. Nelson, McGraw-Hill, 2nd ed, 1998.
  • Aircraft Performance and Design, John Anderson, McGraw-Hill, 1999.


By the end of the course, students should be able to:

  • Understand basic aircraft performance and stability and control (S&C) terminology
  • Estimate aircraft performance in steady and accelerated flight mission phases
  • Size S&C surfaces of an aircraft
  • Demonstrate a physical and mathematical understanding of aircraft flight modes


We will cover S&C and performance topics in the textbooks. Selected topics and sources supplement the text.

  • Aircraft Nomenclature, Atmosphere, Instruments
  • Static stability and control (FSAC, Chap 1)
  • Aircraft equations of motion (FSAC, Chap 2)
  • Longitudinal motion (FSAC, Chap 3)
  • Lateral motion (FSAC, Chap 4)
  • Steady Flight (APD, Chap 5)
  • Accelerated Flight (APD, Chap 6)
  • Aircraft Performance and Control Projects

Aerodynamics I

In the Fall of 2016, I taught AEM 313 Aerodynamics I.

Objectives:   Introduction to subsonic aerodynamics, including properties of the atmosphere; aerodynamic characteristics of airfoils, wings, and other components; lift and drag phenomena; and topics of current interest.

Required Book:     Fundamentals of Aerodynamics, John Anderson, McGraw-Hill, 5th ed, 2010


We will cover subsonic and transonic topics in the textbook. Selected topics and sources supplement the text.

  • Conservation Equations
  • Similarity Parameters
  • Flow Kinematics
  • Euler and Bernoulli Equation
  • Velocity Potential and Stream Function
  • Elementary Potential Flows
  • Laminar and Turbulent Boundary Layers
  • Airfoil and Wing Geometry
  • Thin Airfoil Theory
  • Lifting Line Theory (Example: Lesson16-PrandtlLiftingLine)
  • Lift, Drag and Pitching Moment
  • Low-Re and High-Alpha Effects
  • Subsonic Compressible Flow
  • Transonic and Supercritical Airfoils
  • Aircraft Aerodynamic Design Project (MemoAEM313Project)

Student Evaluations (Fall 2016): 16C Charles O’Neill (AEM 313-001 Aerodynamics)

Induced Drag for Linearly Tapered Wings

More soon…..

Tapered Wing Induced Drag Ratio to Elliptical

Tapered Wing Induced Drag Ratio to an Elliptical Wing

Prandtl Lifting Line Tool

Prandtl Lifting Line theory remains an excellent tools for preliminary design and gaining intuition about the aerodynamics of unswept wings.

Implementing a PLL solver is relatively simple; I made this version in a few hours with Fortran. The solver generates SVG files displaying the wing geometry, gamma and lift distributions as well as the integrated lift and drag coefficients for arbitrary wing geometries (as approximated by linear sections). The program and input files are available at:

A flat elliptical wing demonstrates the flat sectional lift coefficient distribution resulting from an elliptical lift distribution.


The beauty of the Prandtl lifting line theory is the ability to modify the wing geometry and airfoil sections. For example, given a 20% flap deflected 20 degrees on inner wing sections, the sectional lift distribution reflects the flap deflection. Of particular interest is that the shed vorticity is proportional to the slope of the green lift distribution.

Prandtl Lifting Line

The PLL theory is also instructive for understanding control surface behaviors. In the following image, the 20% ailerons are deflected approximately +-10 degrees (Thin airfoil theory is used to determine the equivalent zero lift line.). Of particular concern is that aileron deflections at high AOA can push the local angle of attack into a stalled state.


Delta Wing Demonstrator (DWD16)

Can a flyable aircraft be designed and built in 1 hour?

The Delta Wing Demonstrator is the result of this challenge in rapid aircraft design. Unfortunately, the answer was no. The aircraft actually required 1 hour and 20 minutes.

Continue reading

Low Aspect Ratio Wings

Back in 2006 as part of an independent study course, I used an inviscid CFD solver to estimate the aerodynamic performance of actual low aspect ratio wing configurations. The report (lowargeometryco2006.pdf) was written in a handbook style inspired by the classic Hoerner Lift and Drag books.  lowarconfigsThe configurations were: monoplane, biplane, joined-tip biplane “box”, disc, monoplane with endplates, and a shroud cowl. Biplane gap, stagger, and decalage were considered. Performance criteria such as lift slope, induced drag, lift to drag ratio (L/D) were compared for multiple configurations and aspect ratios.lowar-liftslopeThe final portion of the report provides a visual display of the pressures and flow fields near the configurations.

Wake rollup of an AR=1 wing:



Wake aft of a biplane:


Pressure field interference with respect to biplane gap.


The full report from 2006 is available: LowARGeometryco2006.

The report was intended to support the OSU 2007 AIAA Design/Build/Fly teams during a competition year where the total aircraft span was severely limited:

Aircraft Systems Course

In the Spring of 2016 at the University of Alabama, I taught a brand new course titled Aircraft Systems under the course number AEM 617. Topics under consideration included:

  • Nomenclature (Sample Notes: Lesson01-Introduction)
  • Standard and Non-standard Atmospheres (e.g. Moist Air Density)
  • Airspeed (Flight Data Computer Calculations)
  • Vacuum Systems
  • v-n Diagrams including gust loading
  • Basic 4 bar mechanisms (e.g. slat & flap extensions) and Freudenstein Equations
  • FAR 23 (14CFR23)
  • FAR 25(14CFR25)
  • Cockpit Layouts
  • Flight Control Systems including equations of motion, gear ratio
  • Aircraft Hardware (e.g. AN bolts, rivets, etc.)
  • Hinge Moments (Guest Lecture)
  • Nonlinear Systems Phase Plane Analysis
  • Hydraulic Systems including Actuators, PCU (Power Control Units),
  • Fuel Systems including Inerting Systems and Refueling
  • Pressurization Systems (Guest Lecture)
  • Test Flight Systems and Instrumentation (Guest Lecture)
  • Communication and Navigation
  • Environmental Control Systems (ECS)
  • Emergency Systems
  • Survivability
  • Inertial Navigation Systems including World Reference Frames, and Strapdown Equations
  • OBOGS (Onboard Oxygen Generating System) (Guest Lecture)
  • Kalman Filters
  • Electrical Systems and Wiring  (Guest Lecture)
  • Morphing Wings (Guest Lecture)
  • Software Development and Modular Avionics Bus
  • A brief description of IEEE 754 floating point numbers
  • Spacecraft Attitude (Guest Lecture)
  • Propulsion (Guest Lecture)
  • Multi-Engine Vmc

The notes contain numerous hand drawn images of systems and references to many books.


Detailed Aircraft Systems of Particular Aircraft were analyzed through flight manuals, NTSB accident reports, AIAA case-studies, and expert guest lectures.

  • Cessna 170 & 310
  • Gossamer Condor
  • VTOL: VJ101 and VAK191B
  • X15
  • WW2 Dam Busters (system development case study)
  • DHC-7 (aka. EO-5C / RC-7B)
  • A behind-the-scenes guided tour of the Southern Museum of Flight in Birmingham by two (2) PhDs in History and Engineering.


The course also included a set of lectures titled “Failure Fridays” which investigated aircraft incidents and accidents by tracking the failure points and symptoms with a special emphasis on systems. These included:

  • Cessna 182 Fuel Contamination
  • Alaska 261
  • A320 Fly By Wire
  • Boeing 737 Rudder Actuator
  • TWA 800
  • Diesel Bug
  • Advisory Circulars (AC)
  • Patriot Missile
  • Ariane 5
  • The largest non-nuclear explosion known to man. (Not aerospace, but still an impressive and covertly intentional systems failure!)


This course was particularly interesting; as the instructor, I learned a great deal about many topics. I had to work hard to stay ahead of the students. The students gave one of the best ratings that I have ever received. One student said:

The course was very interesting and likely one of the most valuable classes I have had in college. Rather than sticking strictly to theory as most of the Aerospace curriculum does, this class covers details about the what, why, and how for a wide range of
systems that will be particularly useful in any aerospace career.

Another student said:

This course provided me with an otherwise unobtainable insight into the real world of engineering systems, something not talked
about in other courses. This class is great for the industry engineer.

Not every comment was so positive. One student mentioned that this course required several prerequisites and that “newly transferred” students would find the course “difficult”.

More information and the full course notes are available by contacting Charles O’Neill.

SPA Prototype Aircraft

This summer, my lab in conjunction with Dr. Branam developed an aircraft for testing a prototype flight control system. The aircraft flies beautifully for a rudder-elevator control system. Low power and a large efficient wing allows for exceptional performance at the design weight. As a design decision, the rudder-dihedral roll control is sufficient for the mission purposes.


SPA aircraft

The aircraft specifications are:

  • Wing span: 8 ft
  • Powerplant: OS 3815-1000 with 5000 mAh 3S LiPo
  • Airfoil: SD7062
  • Differential spoilers (marginal for roll control)

SPA aircraft

Thanks to the following engineers and designers:

  • Josh Richards (chief design engineer, air-to-air video pilot)
  • Christopher D. Simpson (chief systems engineer)
  • Christopher R. Simpson
  • Reid Ruggles
  • Abraham Ortiz
  • Alex West
  • Griffin Uthe
  • David Maulick
  • Liz Suttles