Table Of Content'11 IE ROD AMICS OF '11 IE
CONVENTION AIR
V E l II
'~ES
OF A. LIPPISCH
BY
HENRY V. BORST
HENRY V. BORST AND ASSOCIATES
WAYNE, PENNSYLVANIA
1980
COPYRIGHT }980 BY HENRY V. BORST
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•
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PREFACE
Ever since the very early days in there
aviati~n
have been innovative engineers and designers that have
been responsible for some of the major advances in the
design and development of aircraft. These people have
developed new concepts that have made improvements
possible in the capability and performance of vehicles
that otherwise might not have occurred in the course
of the usual process of evolution. As the work of
these innovative engineers has been an important asset
over the years many have wondered by what process the
new ideas are formed and how such people might be
developed. While this question cannot be answered
directly some insight can be gained by examining the
work and technology of an innovative engineer.
One of the early inventors in aviation was
Alexander M. Lippisch whose working career spanned in
Germany the period from 1919 through World War II and
in the U.S. from 1946 to 1975. During this time
Lippisch worked on many unusal and advanced aeronaut-
ical concepts. Many of these design concepts were
unconventional with the design feature based on some
idea or invention. The ob-iect of the advanced design
was to provide improved performance in terms of eff-
iency, speed and/or better flight capabilities such as
vertical take-off with high speed flight performance.
Because of the many ideas and advanced concepts of A.
Lippisch a review of his work has been made to -try to
understand his reasoning and the technical concepts
that led him to the advanced vehicles. From this
review it is hoped that some insight will be gained by
both the practicing engineer and the student as to how
new concepts are formed as well as to a better under-
standing of the aeronautical technology.
Dr. Lippisch had planned to help in preparing
this review of his work and the presentation of the
technology involved. The original concept was to
write a book entitled "Physics of Aerodynamics"
which would draw on his work and background for the
material. His desire was to have the teChnology
presented in a way that would lead to the best poss-
ible understanding of the subject. This presentation
would include those areas where there are still un-
0-4
knowns. Unfortunately his death in 1975 made this
impossible. It became necessary to depend on his
reports, notes and data to prepare the book. Mrs.
Lippisch kindly made available all his notes, reports
and data for this effort. Mr. Arthur Collins furn-
ished all the excellent smoke pictures used in the
book. In addition he allowed the writer to review
all the data and material available from the Collins
Aeronautical Research Laboratory where Lippisch did
much of his research in this country. Additional
material was obtained from a search of NASA and
patent files. While a considerable amount of mat-
erial was found it is believed that much was lost.
In preparing this book we tried to capture the
original idea expressed by the ti tIe "Physics of
Aerodynamics" However as the work proceeded it
became clear that it was also necessary to present
the technology behind many of Lippisches innovative
concepts. As a result the first two chapters con-
tain fundamental aeronautical concepts and present-
ations that cover the basics. While this material
is not necessarly new it is presented to provide an
insight into the ideas used by Lippisch. The many
smoke flow pictures should be useful for gaining
•
this insight. These chapters supplement standard
aeronautical texts and it was tried to bring out the
important aspects that might lead to new iaeas. To
obtain a feel of how Lippisch considered the aero-
nautical technology it is suggested that these chap-
tures be reviewed after Appendix A which was written
by Lippisch is studied. In preparing Chapters I and
II we tried to include any of the concepts of
Lippisch as well as our own that would apply to
the remaining chapters on the advanced vehicles.
In Chapter III the technology of V/STOL aircraft
is presented which leads to the unique vehicle con-
cept known as the Aerodyne. As very little material
was found on the technology of the Aerodyne it was
necessary to develop the important aeronautical
concepts that would apply. This included the aero-
dynamics of the rotor system, means for turning the
flow and other aspects that apply in the design of
V/STOL aircraft such as a method of evaluating
systems for optimum performance. From the material
0-5
presented in this chapter a basic background is
given that should lead to a better understanding of
V/STOL aircraft and their design.
During the latter years of Lippisch's career he
was active in the development of the wing in ground
effect aircraft, WIG. His successful development
and demonstration of the X-112 and X-113 manned WIG
vehicles showed that he had the basics in hand.
This technology was achieved as a result of simple
.experiments and the application of basic concepts
such as those presented in Chapter IV. The idea as
presented of the use of channel flow theory to de-
termine the increase of lift due to ground effect
presented in this chapter was found in his notes.
This basic concept was useful in the analysis of
the stability of the vehicle. In Chapter IV some
of the basic theories and their substantiation by
test data used by Lippisch are given along with
some extensions by the writer in order to make the
work as complete as possible. The material pre-
sented should serve as a basis for future WIG
developments.
The development of the tailless airplane was
the most important achievement of Lippisch during
his career in Germany. This work led to the design
of the rocket powered Messerschmitt Me 163 airplane
used as an interceptor during the latter stages of
WW II. The Me 163 airplane was very clean and fast
for its time and was one of the first aircraft to
encounter adverse effects in stability and control
due to compressibility effects at high Mach numbers.
The swept wing used to obtain stability with the
tailless design helped to alleviate some of these
problems. A presentation of the important aspects
of the tailless airplane is given in Chapter V. In
this chapter we tried to show the complete picture
of the problems involved with the tailless airplane
including the effects of the design on stability,
control, maximum lift and drag.
Chapter VI on new concepts gives the technology
involved in reducing the drag due to lift of con-
ventional aircraft wings. Lippisch obtained a patent
0-6
on wing tip devices for reducing the induced drag.
Although he did 1 itt 1 e in developing the technology
of these devices they are similar to the winglets
studied and tested by NASA. Since drag reduction
is especially important today the various devices
for reducing drag and their technology is given by
the writer based on present day technology. Also
presented in Chapter VI is a discussion of bird
flight which was based on the material found in
Lippisch's note s.
From our review of the work and career of
Alexander Lippisch it appears that his motivation
in being creative was driven by the desire to make a
large step improvement in the performance of aircraft.
Ii: was not satisfied in making evolutionary improve-
ments of existing designs so he was not constrained
by the then conventional concepts. Therefore, he
developed the technology needed to achieve his
goals of better flight characteristics, improved
1 i ft drag ratio and higher flight speeds. As a
result of this many of his design concepts were
ahead of their time. It is hoped that the material
presented will help the engineer and the student
achieve a better grasp, of the subject and develop
more innovative designs and concepts.
ACKNOwr Fl XJFMENIS
The work of the review and analysis of the
technology of Dr. A. M. Lippisch was made possible
by the cooperation of Mrs. Lippisch and Mr. Arthur
A. Collins whom we wish to thank. Mrs. Lippisch
made available a 11 the existing notes, data and
reports covering the work of Dr. isch. Mr. A.
also wish to thank Mr. Ralph Cooper of the Office
Colli n sal s 0 made a v ail a b 1 e the f i 1 e s 0 f the Colli n s
of Naval Research and Mr. Robert Krida of the Naval
Aeronautical Research Laboratory and supplied many
Air Systems Command whose support made th i s book
possible.
of the fine smoke pictures used in this book. Vi
TABLE OF CONTENTS
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(pages are numbered by chapters)
ru:w
I - PHYSICAL CHARACTERISTICS OF
1-1
1HE BASIC PROBlEM
•
Analysis Methods . . . . . . . . . . . . . . 1-2
Fluid Properties . . . . . . . . . . . . . . 1-3
ru:w
VISUALIZATION 1-3
•
Streamlines 1-4
• • • • • • • • • • • • • • • •
Design Features of the Smoke Tunnel 1-7
• • • •
Methods of Testing 1-11
• • • • • • • • • • • • •
Flow Observations at Zero Speed 1-14
• • • • • •
ru:w ru:w
VISUALIZATION OF 1HREE DIMENSIONAL PATIERNS
Flow T est sin Free F I i g h t . . . . . . . . . 1-17
Three-dimensional tunnel for Flow Observa-
tions 1-16
• • • • • • • • • • • • • • • • • • •
1-18
ANALYSIS CF S\fl(E PAT I ERNS
- 1-19
Flow Pattern Blunt Bodies
• • • • • • • •
1-20
Unseparated Flow
• • • • • • • • • • • • • •
1-23
Separated Flow at Higher Angles
• • • • • •
1-23
Boundary Layer Transitions
• • • • • • • • •
-
1-24
Two Dimensional Tests Airfoils
• • • • • • •
1-25
Smoke Time Lines
• • • • • • • • • • • • • •
1-27
Inlet Duct Flow
• • • • • • • • • • • • • •
1-28
Airfoil Flow
• • • • • • • • • • • • • • • •
1-30
Zero Speed Flow Observations
• • • • • • • •
1-31
Flow Augmentation
• • • • • • • • • • • • •
ru:w
1HREE DIMENSIONAL 1-36
•
Wing Tip Flow 1-37
• • • • • • • • • • • • • • •
ru:w
APPLICATION CF VISUALIZATION STUDIES 1-39
•
I I - BASIC CONCEPTS AND THEIR
APPLICATION TO AERODYNAMIC ANALYSIS
BASIC FLUID 1HECRY · . . . . - 2-2
• • • • •
•
0-8
. . . . . . .
. . .
VISCOSITY EFFECTS .. .. .. .. 2-2
Laminar Boundary Layer _ Skin
Friction . . . . . . . . . . . . . . . . . . . . 2-6
Turbulent Boundary Layer _ Skin
Friction . . . . . . . . . . . . . . . . . . . . . . . 2-7
. . .
Boundary Layer Thickness . . . . . . .. 2-8
Skin Friction _ Laminar and
Turbulent Flow • . . . . . . . • . . . . . . 2-9
2-10
Boundary Layer Separation
.. I • .. • .. I .. ..
Separation _ Laminar Flow 2-11
•• I . . . . . . . ..
Separation _ Turbulent Flow . . . . . . . . . 2-12
mAG AND LIFT . 2-13
.. I .. .. • I . . . . . . . . . . •
TWO-DIMENSIONAL AIRFOILS . . • . . . . . . . 2-14
Drag . . . .. .. .. . .. .. . .. .. .. . . .. .. . . 2-1'5
. . .
LIFT .. .. .. .. . . .. .. .. .. .. .. . .. 2 - 2 2
•
•
Unsteady Lift . • . • . . . . • . . . . . . . 2-25
AIRFOIL LIFT mAG CHARACTERISTICS . . . . . • 2-27
Variation of Performance with
Reynolds Number . . . . . . . . . . . . . . . 2-29
Drag at High Reynolds Number . . . . . . . . 2-32
,
Drag with Forced Turbulence . . . . . . . • 2-34
MACH EFFECTS . . . . . . . . . . . . . 2-35
~
THREE-DIMENSIONAL 2-35
R.(W • • • • • • • • • • •
Three- Dimensional Wing . . . • • . . . . . . 2-37
Performance Prediction . . . • . • . . . . '. 2-40
CHAPTER II I _ V/STOL CONCEPTS
RJNDAMENTAL CONSIDERATIONS 3-2
• • • • I .. • .. •
Augmentation ... . . . . .. . . . . .
3-6
I .. .. ..
. .
. . . .
Basic Flight Characteristics .. .. 3-7
SYSIEM EFFICIENCY . . . . . . . • . . • . . . 3-8
. .
Ideal Efficiency . . . . . . . • . . .. .. 3-9
3-9
Adiabatic Efficiency . . . . . . •
• • • • •
Hover and Takeoff Efficiency . .. .. • .. .. . • 3 - 13
Figure of Merit . . . . • . . . . . . . 3-13
• •
0-9
Hover Lift Capability · . . . . . . . . 3 - 15
• • •
Efficiency in Forward Flight . . . . . . . . . 3-16
PERFORMANCE EVALUATION OF V/ STOR AIRCRAFT . . 3 -17
Lift Forces . . 3 -17
• • • • • • • • • • • • • •
V/STOL AIRCRAFT LIFT AND PROPULSION SYSIEMS . 3-24
VIDL Aircraft Hover Lift Systems . . . . . . . 3-24
Helicopter and/or Propeller Rotors . . . . . . 3-25
Propellers . . . . . . . . . . . • . . . . . . 3-25
Ducted Fans . . . . . . . . . . . . . . . . . 3-26
Ducted Fan Design and Analysis Procedures . . 3-27
Shroud Thrust and Velocity . . . . . . . . . . 3-28
Fan Thrust and Power . . . . . . . . . . . . . 3-28
Duct Induced Velocity . . . . . . . . . . . . 3-34
DUCIED FANS I N V/STOL AIRCRAFT . . . . . . . . 3-35
Ducted Fans with Turning Vanes . . . . . . . . 3-36
Design and Analysis of Turning Vanes . . . . . 3-38
Turning Losses . . . . . . . . . . . . . . . . 3-41
Powered Lift with Jet Engines . , . . . . . . 3-43
Lift Augmentation . . . . . . . . . . 3 - 43
• • • •
V/STOL AIRCRAFT EVALUATION · . . . . . . . . 3 - 44
1HE LIPISCH AERODYNE · . . . . . . . . 3 - 45
• • •
Formation of Design Criteria . . . . . . . . . 3-46
Vehicle Configuration . . . . . . . . . . . . 3-48
CHAPTER I V _ GRaJND EFFECT MACHINES
PRINCIPLES . . . . . . . . . . . . . 4-2
. . . . .
.
4-3
CLASSICAL GRaJND EFFECT 1HEORY
"
•
4-4
Wing Without End Plates • . • . . . . • . . .
4-8
Wings With End Plates
• • • • • • • • • • •
GRaJND EFFECT 1HEORY EVALUATION . . . . . . . 4 - 10
Experimental Data . . . . . . . . . . . . . . 4-10
Lift Drag Ratio Comparison . . . . . . . . . 4-11
Lift Comparison . . . . . . . . . . . . . . . 4-13
Lift Curve Slope . . . . . . . . . . . . . . 4-13
0-10
WING GROUND EFFECT THEORY • . . . . • . . . 4-16
~
Lift Losses Due to Leakage • • . . . . . . . • 4-23
MAXIMUM LIFT COEFFICIENT .. .. .. .. .. .. .. .. .. .. • 4-26
CENTER OR PRESSURE LOCATION • . . • . • . . . • 4-28
STABILITY AND CONTROL .. .. .. .. .. .. .. .. .. .. .. .. 4 - 29
Longitudinal Stability . . .. .. .. .. .. .. .. .. .. .. .. 4 - 31
Hydrodynamic Stability • • .. .. .. .. .. .. .. .. .. .. .. 4-32
Stability Derivatives . . .. .. .. .. .. .. .. .. .. .. .. 4 - 32
Dynamic Stability • . • • • . . .. .. .. .. .. .. 4- 33
• •
WIG VEHICLE DESIGN STUDIES .. .. .. .. .. .. · • 4- 34
• •
EXPERIMENTAL DATA .. .. .. .. .. .. .. .. .. . . . 4 - 38
LIPPISCH WIG VEHICLE DESIGNS . . . . . . . . . 4-43
FULL SCALE VEHICLE TESTS .. .. .. .. .. · • • . 4-44
.. ..
RESULTS .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . . 4-47 : -
CHAPTER V _ DELTA AND SWEPT WINGS
BASIC CONCEPTS • . • • • . • • • • • • . . • 5-1
•
•
TAILLESS AIRCRAFT DEVELOPMENT . . 5-2
• • • • • • •
Ram Jet Eng i n e s . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 5-6
.. .. .. ..
• • •
BASIC DESIGN CONSIDERATIONS' • • 5-8
_ TAILLESS AIRPLANES
Design of Swept and Delta Wings • . 5-8
• • • • • •
Stability . . . . . . . . .. .. .. .. .. .. .. .. .. .. .. 5-9
Trim and Pitch Control . . . . . . . . . . · . 5-14
Lateral Control . . .. .. .. .. .. .. .. .. .. .. .. .. .. .. 5 - 16
Directional Control .. .. .. .. .. .. .. .. .. .. .. .. .. .. 5 - 18
Flap Interaction . .. .. .. .. .. .. .. .. .. .. .. .. .. .. 5 - 18
Power Effects . . . .. .. .. .. .. .. .. .. .. .. .. .. .. .. 5- 19
.. .. .. .. .. 5-20
Maximum Lift • • • • • • • • · . . .
Leading Edge Slots . . .. .. .. .. .. .. .. .. .. .. .. .. 5 - 21
Compressibility Effects • • • • • · . 5- 21
• • • • •
Aeroelastic Effects • . · . 5-22
• • • • • • • • • •
