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Dr. Jan Roskam • Soft cover • 496 pp • Print: 2012

Lessons Learned in Aircraft Design presents examples of lessons learned in airplane design since 1945. The lessons are largely drawn from the aircraft design and accident/incident literature. The author hopes that this book will contribute to the safety of flight.

A brief summary is presented of safety statistics, certification and operational standards, safety standards and their relationship to design in general.

Accident/incident discussions are presented in the following areas:

• operational experience

• structural design

• flight control system design

• powerplant installation design

• systems design

• manufacturing and maintenance

• aerodynamic design

• configuration design and aircraft sizing

In each case the discussion starts with the recounting of a problem which arose. Then the probable cause of the problem is identified, one or more solutions are indicated and finally a lesson learned is formulated.

Since many designers will eventually become program managers, it is instructive to recount some trials and tribulations associated with marketing, pricing and program decision making.

As is shown by many examples in this book, safety of airplanes often starts in the design phase. However, sometimes the certification process itself, for whatever reason, fails.

This book will be useful to practicing design engineers, test pilots and program managers. It can be used in the classroom to help in the education of future aircraft designers and engineering/maintenance personnel.

Table of Contents

Chapter 1 Safety, Incidents, Accidents and their Relationship to Aircraft Design in Perspective

1.1 Introduction
1.2 Commercial Airplanes
1.3 General Aviation Airplanes

Chapter 2 Design Lessons Learned from Operational Experience 17

2.1 Introduction
2.2 Gust Lock on During Take-off
2.3 Center of Gravity Too Far Aft I
2.4 Minimum Un-Stick Speed I
2.5 Accidental Retraction of Landing Gear During Landing Roll
2.6 Cowl Flaps Left Open Upon Flap Retraction
2.7 Flight Characteristics with One Engine Inoperative
2.8 Tail Stall in Icing Conditions
2.9 Unsweeping Wings with the Flaps Down
2.10 Center of Gravity too far Forward
2.11 Loss of Electrical Power Leading to Loss of Attitude Instrumentation
2.12 Flight Characteristics with one Engine Inoperative II
2.13 Rudder Control System too Complicated
2.14 Minimum Unstick Speed II
2.15 Electrical System Failed During Take-off Emergency
2.16 Aft Center of Gravity and Stabilizer Mis-trim During Take-off
2.17 Reverse Propeller Mode in Flight
2.18 Center of Gravity too far Aft and Seat Design
2.19 Icing on Take-off I
2.20 Take-off without Flaps
2.21 Sterile Cockpit and Rudder Trim Switch Location
2.22 Icing on Take-off II
2.23 High Speed Descent to Avoid Icing
2.24 Center of Gravity too far Aft II
2.25 Center of Gravity too far Aft, Overloading and Misrigged Controls
2.26 Center of Gravity too far Aft and Overloading
2.27 Old Habits Return in Emergencies I
2.28 Old Habits Return in Emergencies II
2.29 Postlude

Chapter 3 Lessons Drawn from Structural Design

3.1 Introduction
3.2 Fatigue Failure of Wing Fitting I
3.3 Fatigue Failure of Wing Fitting II
3.4 Canopy Loads Must Be Watched
3.5 Verification in Structural Design
3.6 Fatigue Failure due to Pressurization Cycles
3.7 Vertical Tail Flutter
3.8 Whistling Swan Downs Viscount
3.9 A New Flutter Mode
3.10 Corrosion Fatigue
3.11 Rear Pressure Bulkhead Failure I
3.12 Crack Propagation I
3.13 Horizontal Stabilizer Failure
3.14 Elevator Structural Failure
3.15 Rear Pressure Bulkhead Failure II
3.16 Crack Propagation II
3.17 Cargo Door Hinge Design
3.18 Vertical Tail Fatigue due to Vortex Shedding
3.19 Design Instructions Ignored

Chapter 4 Lessons Drawn from Flight Control System Design

4.1 Introduction
4.2 Heat Source Close to Flight Controls
4.3 Ailerons Reversed I
4.4 Gust Lock Engaged in Flight
4.5 Propeller Blade Severs Controls I
4.6 Design for One-way Fit
4.7 Ailerons Reversed II
4.8 Propeller Blade Severs Controls II
4.9 Elevator Boost System Bolt Backs Out
4.10 Elevator Control Forces to Overcome Electric Trim Tab Failure Become too High
4.11 Pitch Trim Failure Reverses Elevator Stick-force-speed-gradient
4.12 Reversing Polarity in a Pitch Damper
4.13 Take-off with Locked Elevator I
4.14 Elastic Stop-nuts in Flight Control Systems
4.15 Controls Jammed by Foreign Object
4.16 Rudder Fitting Failure
4.17 Locating Flight Control System Cables
4.18 Pilot Induced Oscillations
4.19 Reversing Polarity in a Yaw Damper
4.20 Loss of Control due to Unwanted Extension of Ground and Flight Spoilers
4.21 Take-off with Locked Elevator II
4.22 Take-off with Rudder and Aileron Controls Locked
4.23 Take-off with Mis-trimmed Stabilizer
4.24 Defunct Elevator Hard-stop
4.25 Control System Compliance
4.26 One Engine Out Control Problem
4.27 Redundant System is not Redundant
4.28 Uncommanded Elevator Travel
4.29 Uncommanded Roll at Take-off
4.30 Elevator Trim Tab Failure
4.31 The Hard-stop which was not a Hard-stop
4.32 Jammed Servo Tab
4.33 Unnecessary Loss of Control
4.34 Frozen Ailerons
4.35 Misrouting of Control Cables
4.36 Water Leaks do it Again
4.37 Uncommanded Yaw
4.38 Routing Control Cables Past Engine Burst Planes

Chapter 5 Lessons Drawn from Engine Installation Design

5.1 Introduction
5.2 Propeller Too Large or Landing Gear Too Short
5.3 Propeller Reversal in Flight I
5.4 Propeller Reversal in Flight II
5.5 Propeller Reversal in Flight III
5.6 Exhaust Fairing I
5.7 Propeller Reversal in Flight IV
5.8 Propeller to Fine Pitch During Approach
5.9 Design for Engine Removal
5.10 Flame-out Due to Engine Mount Compliance
5.11 Engine Bearing Failure Followed by Propeller Separation
5.12 Whirl Mode Flutter
5.13 Adjacent Engine Installations
5.14 Exhaust Fairing II
5.15 Propeller Reversal in Flight V
5.16 Exhaust Fairing III
5.17 Propeller Blade Separation I
5.18 Propeller Blade Separation II
5.19 Uncommanded Propeller Blade Pitch Reduction
5.20 Uncommanded Thrust Reverser Deployment
5.21 Power levers Moved To Beta Range in Flight I
5.22 Uncontained Engine Failure I
5.23 Propeller Blade Separation III
5.24 Uncontained Engine Failure II
5.25 Uncommanded Thrust Reverser Deployment II
5.26 Tire Tread Ingested Into Engine
5.27 Fuel Line Chafed Through
5.28 Involuntary Engine Shutdown
5.29 Power Levers Moved to Beta Range in Flight II

Chapter 6 Lessons Drawn from Systems Design

6.1 Introduction
6.2 Electrical System Design I
6.3 Fuel System and Electrical System Design
6.4 Fuel Vent Design I
6.5 Fire Extinguishing System Design
6.6 Hydraulic System Design I
6.7 Design Induced Mistake I
6.8 Service Door Fasteners
6.9 Design Induced Mistake II
6.10 Firewall Fuel Shut-Off Valve Cables in Wheel Well
6.11 Hydraulic System Design II
6.12 Hydraulic System Design III
6.13 Fuel System Design I
6.14 Fuel Vent Design II
6.15 Cabin Door Design I
6.16 Fuel System Design II
6.17 Cargo Compartment Light Causes Fire
6.18 Cabin Door Design II
6.19 Design for Lighting Strikes
6.20 Fuel Lines Close to Landing Gear Brace
6.21 Loss of Pitch Control Due to Fire
6.22 Confusing Systems Design
6.23 System Redundancy Saves the Day I
6.24 Engine Failure Precipitates Brake Failure
6.25 Systems Design, Flight Crew Training and Improper Maintenance Procedures
6.26 Service Lift Design
6.27 Leading Edge Slat Asymmetry
6.28 System Redundancy Saves the Day II
6.29 Flap Asymmetry
6.30 Design of Windshield Washer System
6.31 Three Hydraulics System Lines in the Leading Edge
6.32 Leaks into the Avionics Bay I
6.33 Nacelle Cowl Design and Fuel Filter Cover Design
6.34 Ground Spoilers Deploy in Flight
6.35 Hydraulic System Design Problem
6.36 Cabin Door Design III
6.37 Landing Gear Actuator Corrosion
6.38 Leaks Into the Avionics Bay II
6.39 Fuel System Design II
6.40 Landing Gear Door Design
6.41 Moisture Ingress I
6.42 Electrical System Design II
6.43 Icing of Stall Warning System
6.44 Moisture Ingress II
6.45 Flap/Slat System Design
6.46 Galley Chiller Fan Blade and Wiring Failure Causes In Flight Fire

Chapter 7 Lessons Drawn from Maintenance and Manufacturing 369

7.1 Introduction
7.2 Propeller Blade Separation in Flight
7.3 Elevator Control Bolt Backed Out I
7.4 Elevator Servo Tab Bolt Backed Out
7.5 Engine Maintenance Error
7.6 Propeller Reversal in Flight
7.7 Landing Gear Truck Beam Failure
7.8 Elevator Control Bolt Backed Out II
7.9 Loss of Roll Control
7.10 Quenching
7.11 Weight Control
7.12 Incomplete Skin Bonding
7.13 Drain Holes Forgotten
7.14 Maintenance Man-Hours Per Flight Hour
7.15 Placards on Inspection Covers
7.16 Inspection Cover not Large Enough
7.17 Landing Gear Corrosion
7.18 Grit Blasting
7.19 The Wrong Hydraulic Pump
7.20 Faulty Structural Repair
7.21 Fuel Tank Purge Door Left Open

Chapter 8 Lessons Drawn from Aerodynamic Design, Configuration Design and Aircraft Sizing

8.1 Introduction
8.2 Empennage Changed Due to Insufficient Longitudinal and Directional Stability
8.3 Dorsal Fin Suppresses Rudder Lock
8.4 Commonality Lost
8.5 Deep Stall I
8.6 Sizing the Cabin Cross Section in a Competitive Environment
8.7 Sizing an Airplane to the Requirements of One Customer
8.8 Spin strips
8.9 Transonic Aerodynamic Center Shift
8.10 Swept Vertical Tail on a Propeller Driven Airplane
8.11 Transonic Drag I
8.12 Deep Stall II
8.13 Snaking Oscillation Due to Local Directional Instability
8.14 Aileron Reversal due to Tail Interference
8.15 From Vatlit to Avanti
8.16 Horizontal Tail Sizing I
8.17 Horizontal Tail Sizing II
8.18 The XFV-12
8.19 Do Forward Swept Wings Make Sense?
8.20 Unique Solution to an Extreme Range Requirement
8.21 More Examples of Area Ruling
8.22 Candar with Close Coupled Propeller
8.23 Directional Stability Should be Required

Chapter 9 Lessons Drawn from Marketing, Pricing and Program Decision Making

9.1 Introduction
9.2 Cessna 620
9.3 Convair 880/990
9.4 McDonnell 119 and 220
9.5 Boeing 909
9.6 Boeing 707 and Douglas DC-8
9.7 Boeing 720
9.8 Dassault Mercure
9.9 Lockheed 1011 and its Rolls Royce RB-211 Engines
9.10 Pricing Yourself out of the Market
9.11 VisionAire Vantage
9.12 DreamWings Valkyrie and Hooligan
9.13 Eclipse 500
9.14 Safire S-26

Chapter 10 Summary of Lessons Learned

10.1 Introduction
10.2 Lessons Learned from Operational Experience (Chapter 2)
10.3 Lessons Learned from Structural Design (Chapter 3)
10.4 Lessons Learned from Flight Control System Design (Chapter 4)
10.5 Lessons Learned from Engine Installation Design (Chapter 5)
10.6 Lessons Learned from Systems Design (Chapter 6)
10.7 Lessons Learned from Maintenance and Manufacturing (Chapter 7)
10.8 Lessons Learned from Aerodynamic Design (Chapter 8)

About the Author:

Dr. Jan Roskam has authored ten books on airplane flight dynamics and airplane design. He co-authored Airplane Aerodynamics and Performance with Dr. CT. Lan. He has written more than 160 papers on these topics and authored the popular Roskam's War Stories. He has actively participated in more than 36 major airplane programs. He retired as Ackers Distinguished Professor of Aerospace Engineering at The University of Kansas (KU) in 2003, where he taught airplane design, stability and control. Dr. Roskam retired as President of DARcorporation (Design, Analysis and Research Corporation) in 2004. He currently serves as an active consultant for DARcorporation, which develops and markets airplane design and analysis software, and is a successful private and government consulting firm.

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