Comparison of Three Angle of Attack (AOA) Indicators

89 Pages·2016·2.81 MB·English

by  Camilo Jimenez

Dissertations and Theses
11-2013
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Camilo Jimenez
Embry-Riddle Aeronautical University - Daytona Beach
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Jimenez, Camilo, "Comparison of Three Angle of Attack (AOA) Indicators: A Usability Study" (2013).
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COMPARISON OF THREE ANGLE OF ATTACK (AOA) INDICATORS: A
USABILITY STUDY

By
Camilo Jimenez

A Thesis Submitted to the College of Arts and Sciences in Partial Fulfillment of the
Requirements for the Degree of Master in Science in Human Factors and Systems

i
Embry-Riddle Aeronautical University
Daytona Beach, Florida
November 2013

ii

ABSTRACT
Researcher: Camilo Jimenez
Title: COMPARISON OF THREE ANGLE OF ATTACK (AOA) INDICATORS: A
USABILITY STUDY
Institution: Embry-Riddle Aeronautical University
Degree: Master in Science in Human Factors and Systems
Year: 2013

Angle of Attack (AOA) is an important aeronautical concept used to understand the performance
status of an aircraft during different flight stages. The Federal Aviation Administration (FAA)
has indicated the importance of developing and encouraging the use of affordable AOA based
systems to increase inflight safety. Embry-Riddle Aeronautical University’s flight department
decided to install AOA indicators in its fleet of Cessna 172S, to increase safety and to help
student pilots better understand this important concept. This paper presents a review of AOA,
visual display design principles, and usability. This experimental study examined three different
AOA indicators provided by the flight department. The goal was to conduct a usability study in
order to understand which of these indicators was better suited for student training. Instructor
pilots were used as participants in a series of flights, in which they were asked to perform
different maneuvers in which using AOA indicators was thought to help increasing stall
awareness and performance. At the end of each flight participants were asked to complete a
series of surveys (including an adaptation of the system usability scale) and to provide comments
in order to understand their preferences related to AOA indicators. The analysis of the data
shows significant differences between the indicators. Discussion of the results and
recommendations for future studies are also covered.
iv
TABLE OF CONTENTS

Review Committee Signature Page .............................................................................................................. iii
Abstract ........................................................................................................................................................ iv
List of Tables .............................................................................................................................................. vii
List of Figures ............................................................................................................................................ viii
Introduction ................................................................................................................................................... 1
Significance of the Study .......................................................................................................................... 6
Purpose Statement ..................................................................................................................................... 7
Hypotheses ................................................................................................................................................ 7
Limitations and Assumptions ................................................................................................................... 8
Definition of Terms ................................................................................................................................... 8
List of Acronyms ...................................................................................................................................... 9
Review of the Relevant Literature .............................................................................................................. 10
Angle of attack ........................................................................................................................................ 10
Usability .................................................................................................................................................. 12
Methods ...................................................................................................................................................... 20
Research Approach ................................................................................................................................. 20
Sample .................................................................................................................................................... 20
Apparatus and Materials ......................................................................................................................... 21
Design and Procedures ............................................................................................................................ 22
Sources of the Data ................................................................................................................................. 25
Data Collection Device ........................................................................................................................... 25
Instrument reliability and validity ....................................................................................................... 25
Treatment of the Data ............................................................................................................................. 26
Results ......................................................................................................................................................... 27
Discussion, Conclusion, and Limitations .................................................................................................... 38
Discussion ............................................................................................................................................... 38
Conclusion .............................................................................................................................................. 45
Limitations .............................................................................................................................................. 48
References ................................................................................................................................................... 51

v
Appendices
A Approximate AOA Indications for Each Flight Maneuver ...................................................... 56
B Informed Consent Form ........................................................................................................... 58
C Pre-Flight Questionnaire .......................................................................................................... 61
D Post-Flight Questionnaire......................................................................................................... 67

vi
LIST OF TABLES

Table 1 Mean and Standard Deviation for SUS............................................................................ 28
Table 2 Mean and Standard Deviation for Visual Representation ............................................... 28
Table 3 Pairwise Comparisons for Visual Representation ........................................................... 29
Table 4 Mean and Standard Deviation for Enhanced Performance .............................................. 29
Table 5 Pairwise Comparisons for Enhanced Performance .......................................................... 30
Table 6 Mean and Standard Deviation for Enhanced Stall Awareness ........................................ 30
Table 7 Pairwise Comparisons for Enhanced Stall Awareness .................................................... 31
Table 8 Mean and Standard Deviation for Crosschecked Indicator During Maneuvers .............. 31
Table 9 Mean and Standard Deviation for Indicator would Enhance Students’ Performance ..... 32
Table 10 Ranks for Crosschecking the Indicator helped in Flying a More Stable Approach on
Final (Normal Approach and Landing)......................................................................................... 32

Table 11 Ranks for Crosschecking the Indicator helped in Flying a More Stable Approach on
Final (Short Field Approach and Landing) ................................................................................... 33
Table 12 Ranks for Crosschecking Indicator Enhanced Landing Performance (Normal Approach
and Landing) ................................................................................................................................. 33
Table 13 Ranks for Crosschecking Indicator Enhanced Landing Performance (Short Field
Approach and Landing) ................................................................................................................ 34
Table 14 Overall Satisfaction Ranks............................................................................................. 34
Table 15 Observer A * Observer B Comments Crosstabulation………………………………...36

vii
LIST OF FIGURES

Figure 1. Relationship of lift to AOA. ......................................................................................... 11
Figure 2. The three AOA indictors preselected by the flight department for the proposed study.
vertical bar, horizontal, bar, and legacy indicators. ...................................................................... 21
Figure 3. Interrater agreement by indicator type separated by type of comment. ........................ 37
Figure 4. Interrater agreement on the instrument location in the cockpit by indicator. ................ 38
Figure 5. Location of the AOA indicators in relation to the airspeed tape on the G1000 and
standalone airspeed indicator. ....................................................................................................... 44

viii
1

Introduction
Angle of attack (AOA) is an important concept used to understand basic aerodynamics
principles in aviation, as well as to understand some aspects of an aircraft’s performance
capabilities (Boeing, 2000). Angle of attack, in its simplest form, could be defined as the angle at
which the aircraft’s wing chord lines meet the relative wind (the direction of the airflow with
respect to the airfoil) (Flach, Patrick, Amelink, & Mulder, 2003; Federal Aviation
Administration, 2008). In most military and commercial aircraft, there is either a dedicated
instrument that shows AOA, or a warning stall system that, even though it does not explicitly
depict AOA information, uses this aeronautical concept to warn pilots of a potential stall. In
general aviation (GA) the use of AOA indicators is almost nonexistent and most GA aircraft lack
such an indicator. Even though the concept of angle of attack has been around since the first
years of aviation (Langewiesche & Collins, 1972; Aarons, 2006), and is currently widely used by
military pilots, especially naval aviators (Boeing, 2000; Dunn, 2011; Aarons, 2006), its
importance among commercial and general aviation pilots has been undervalued or simply
ignored due to the lack of knowledge and/or training on the value of the information a dedicated
AOA indicator can provide to airmen (Aarons, 2006; Flach et al., 2003). One of the reasons why
many pilots do not value angle of attack is because, even though at some point during their flying
career they have been exposed to this concept and its relation to the lift curves, AOA is usually
displaced by the airspeed as a primary indicator of performance (Aarons, 2006). Flach et al.
(2003) mentioned that during a landing simulation task, experienced pilots seemed to be more
interested in final approach speeds rather than angle of attack. Pilots are trained to use airspeed
as a source of performance data, and when airspeed is available to the pilot, AOA should only be
used as a supplementary or advisory source, but never as a primary source of performance data