UCLA Extension

Airframe Stress Analysis and Sizing

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March 16-19, 2020

Most airframes deal with thin-sheets or shells that may have buckling and crippling characteristics. This course provides a comprehensive background in metallic airframe sizing that combines input from both material strength analyses and hands-on design experience. Practical airframe design depends extensively on experimental or test data that must be correlated with analytical procedure.

Discussion focuses on the selection of structural configurations and materials that combine to produce an economic design, while at the same time taking into account the effects of static, fatigue, fail-safe requirements, damage tolerance, and repairability. Substantial information and data for metallic airframe sizing is presented in tables, charts, and/or curves based on past experience and/or test results.

The sizing methods presented in this course also are intended for those who need rough estimation techniques to support preliminary structural design. Moreover, these methods can give quick and accurate solutions to design problems simply with the aid of a desktop engineering calculator.

Homework assignments are given everyday in class. Participants must bring a small desktop engineering calculator.


Some basic understanding of strength of materials is required.

Course Materials

The text, Airframe Stress Analysis and Sizing, Third Edition, Michael C.Y. Niu (Conmilit Press, 2016), and lecture notes are distributed on the first day of the course. The notes are for participants only and are not otherwise available for sale or unauthorized distribution.

Coordinator and Lecturer

Michael C.Y. Niu, MS, President, AD Airframe Consulting Company, Granada Hills, California. Mr. Niu is a metallic and composite airframe consultant who has acquired over 35 years’ experience in aerospace and airframe structural analysis and design, and was a senior research and development engineer (management position) at Lockheed Aeronautical Systems Company. As department manager in charge of various structural programs there, he was responsible for the development of innovative metallic and composite structural design concepts applicable to current and future advanced tactical fighters and advanced transports. He also was involved in conceptual and preliminary airplane design, and was lead stress engineer responsible for the L-1011 wide-body aircraft wing and empennage structures. During 1966 and 1968 he served as stress engineer for the B727, B747, and other aircraft at The Boeing Company in Seattle. Mr. Niu is the author of Airframe Stress Analysis and Sizing (1999), Composite Airframe Structures (1992), and Airframe Structural Design (1988). He also has written Lockheed’s Composites Design Guide and Composites Drafting Handbook . He received the Lockheed Award of Achievement and Award of Product Excellence in 1973 and 1986, respectively. Mr. Niu is listed in Who’s Who in Aviation , 1973.

Daily Schedule

Day 1


Discussion of preliminary sizing, structural design phases, design criteria and regulations for certification, detail design and stress analysis, design guidelines.


Structural external and internal loads, static and dynamic load, wing and empennage loads, fuselage loads.

Material Properties

Hooke’s law, stress-strain curves, material properties, material selection, grain directional effects, stress corrosion effects, fatigue and crack growth characteristic.

Structural Analysis

Determinate (non-redundant) structures, indeterminate (redundant) structures.

Sizing Procedures

Preliminary sizing requirements, production stress analysis, formal stress analysis for certification, rigidity requirements, margin of safety (MS) or reserve factor (RF).

Simple Beam

Beam bending, plastic bending, forced bending, stiffness (EI), shear stresses and shear flows, taper effect.

Day 2

Box Beam

Beam in torsion (closed vs. open sections), single-cell enclosed sections, two-cell enclosed sections, panel stiffener effects, shear stresses, shear stiffness (GJ), taper effect.

Plate and Shell

Plates and shells applications, plate pressure bulkheads, shell pressure bulkheads, honeycomb panel application.

Joints and Fittings

Types of joint, fastener selection, under ultimate and fatigue loads, shim and eccentricity effects, lugs and shear pins, tension fittings and bolts, fatigue considerations, design concerns.

Day 3

Column and Instability Buckling
Euler column equation, column end restraints, beam-columns, crippling stress, Euler-Johnson curves.

Buckling of Thin Sheet

Compression loads, shear loads, combined loads.

Flat and Curved Shear Panels

Shear resistant beams (non-buckled web), incomplete diagonal tension beams (buckled web).


Holes and cutouts, cutout in shear beam, panel with small hole, tension and compression panel with large cutout.

Day 4

Compression Panels

Flat skin-stringer panels, integrally-stiffened panels, axial and shear load redistribution, sizing of the panel skin and stringers.

Damage-Tolerant Panels (In Tension)

Fatigue design considerations, stress concentration, crack growth and fail-fail.

Discussion of Transport Preliminary Wing Sizing

Upper panel (mainly in compression loads), lower panel (mainly in tension loads), spars, ribs, general discussion of design considerations and applications.

Discussion of Transport Preliminary Fuselage Sizing

Fuselage cabin pressure and flight loads, skin and stringers, frames, floors, general discussion of design considerations and applications.

Structural Test Setup

Strain gauges; component tests under compression load, shear load, and tension fatigue load; full-scale airframe static and fatigue test; test considerations.


For more information contact the Short Course Program Office:
shortcourses@uclaextension.edu | (310) 825-3858 office