Abstract VTOL (Vertical Take Off/Landing) Designs
Created on X-Plane® Plane Maker software
Zak Sky King
Whitefish High School
Whitefish, Montana
April 30, 2007
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Abstract
This project addresses the design of a high altitude, low capacity, jet powered
vertical take-off and landing aircraft. The design requirements required an empty weight
of 40,000 pounds, a maximum capacity of six passengers, gear, and two crewmembers.
The aircraft needed a maximum airspeed of just under mach one (770 MPH), at least full
vertical take-off and landing capabilities with possibilities of STOL (short take off and
landing) or SVTOL (short/Vertical take-off and landing) capabilities. Range was short as
the aircraft would not be designed for endurance, and had a ceiling of 30,000 feet.
Specially designed CAD software called X-Plane Plane Maker, which was designed to
accurately portray an aircraft in flight, was used to design the models. The project would
have been far more time consuming and expensive without the simulation and design
software X-Plane provided. An extension of the X-plane software was used to fly and test
the models designed in plane maker. With different designs, different problems arose, as
well as different causes for the same problems. As of yet, an aircraft capable of
successful transition between vertical and horizontal flight has not been developed.
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Introduction
On Mt. Everest in the Himalayan mountains, climbers are often unreachable
should an accident happen. The air is so thin that rotary winged aircraft are unable to
reach the climbers (Flight Ceiling 2004). But such altitude restrictions are less stringent
upon jet turbine aircraft because of their ability to compress the air before expelling it for
thrust. Therefore, a jet VTOL (Vertical Take-Off/Landing) aircraft would be able to
perform rescue and re-supply missions to endangered climbing parties better than any
existing aircraft.
VTOL aircraft have existed since the nineteen fifties, when the U.S. Air Force
saw the advantages of the ability to take off and land vertically in a small area (Flying
Bedstead 2007). Many programs ensued, and other countries soon followed suit. Russia
developed a jet-powered fighter VTOL with the Yak-36 Freehand, Britain developed the
Hawker Sidley Harrier, and now America has the Lockheed-Martin F-35 and the BellBoeing V-22 Osprey. The concept of a jet powered VTOL transport is nothing new;
Germany developed the Dornier Do.31 in the sixties, though the concept was scrapped
because of its fuel ineffectiveness (Dornier Do.31 1960).
However, since the time of the Do.31 and following projects, there have been
enormous leaps in the field of aerospace engineering. The major use of computers in
aircraft now has allowed for stability in the most unstable aircraft designs such as the B-2
Spirit (Flight Control Systems 2004). These computers could help to overcome the
essential flaws of VTOL aircraft, and opens up possibilities for new designs.
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I decided to design a set of criteria for a VTOL aircraft and then design a plane to
meet them. I used a software program called X-Plane® Plane Maker that allowed me to
design the aircraft in almost every aspect and then test and fly it in a partner program.
I was interested in the idea of a VTOL aircraft because of a personal fascination
with aircraft, and the possibilities of a VTOL design. VTOL designs have the ability to
land vertically in a small space and then fly horizontally at high speeds and reach areas
remote to most conventional designs, being either out of range or too time consuming to
reach by rotary wing aircraft or impossible to land on by fixed wing aircraft.
I set up a set of design criteria that the aircraft had to perform to. The criteria
were: a flight ceiling of thirty thousand feet, jet turbine engines and VTOL capabilities,
and the ability to carry at least six passengers, two crew members and additional gear.
The aircraft I designed evolved to more than twenty different designs, though all
have some similarities. The design criteria I used limits the size and weight of the
aircraft, so all of the designs are relatively the same size and weight. VTOL’s are the
future of aviation because of their theoretical efficiency, and what better a way to get a
glimpse of the future than by designing it?
Materials and methods
I designed the aircraft on X-Plane® Plane Maker. I began by designing a basic
fuselage, the main body of the aircraft. I then designed a basic set of wings and set up
engine nacelles (casings) and engine specifications. The specifications for the primary
base model were two low-bypass engines each with twenty thousand pounds of thrust and
another five thousand pounds with afterburners. I used a compression area of two square
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feet, a five second fuel intro time, a four second throttle advance and a two second spoolup time for the turbines (See Fig. 1.1). All of the engine specs were independent and were
set factors that I programmed in. I also programmed in an initial empty weight of eight
thousand pounds with a one thousand pound fuel load, and two thousand pounds of
possible payload weight. The specs were updated as new models were designed and the
initial specs were deemed impractical. These figures were purely hypothetical. I located
two fuel tanks and a lateral position of three feet to each side, a vertical of one foot under
point of origin and fifteen feet behind the origin. I located the center of gravity at
seventeen feet behind and two feet underneath the origin (See Fig. 1.2). The point of
origin was two feet behind the nose of the aircraft and I based all measurements from that
point. As models progressed the fuselage was changed to accommodate better weight
distribution, as were the wings for better aerodynamics and as VTOL (Vertical Take-Off
and Landing) capabilities were incorporated, swept downward for more support during
vertical flight.
The engines nacelles were modified in one series of designs to incorporate four
exhaust nozzles to allow for vertical thrust vectoring. Another series used four lift fans,
two on each side, positioned in front of the engine turbines and vertically over each other.
The blades were counter rotating so as to prevent any rotation of the airframe. Other
models used different wing designs and variations of different parts of the airframe. Each
design change was initiated as a result of an action in the simulation program, and an
attempt to either fix a problem or improve upon a desirable trait; some changes were
attempts at preemptive solutions. As of present, designs have varied so that some designs
fly conventionally, some fly vertically and some do not fly as the design changes to their
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airframes resulted in catastrophic failures. Changes are on going in an attempt to fix everpresent problems, and a solution to a certain problem may result in an entirely new
problem until the result is within the acceptable parameters.
Fig. 1.1 AVX2 Base Model Jet Engine Specs Data Entry Points
Fig. 1.2 AVX2 Base Model Weight and Balance Data Entry Points
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Results
I have twenty-three models of aircraft designed to meet VTOL (Vertical TakeOff/Landing) criteria, ranging from the original base design to the most current model
with vertical capabilities. Six of the models are capable of vertical flight, ten are only
capable of conventional flight and seven are completely dysfunctional at this point.
Dysfunctional in some models means that more time and attention are required to make
the design flight worthy while in some cases the design has a major flaw that result in
new model designations when fixed.
Discussion
As the aircraft I designed are abstract in that they exist purely as virtual designs
and not as real world models, they cannot be accurately compared to any existing model
of aircraft. Despite the fact that the X-plane® simulation software offers a high level of
accuracy for flight characteristics, it does not govern whether or not the aircraft could
actually be built. There are design possibilities that are purely theoretical as physical
construction of certain designs would be physically impossible. Though the simulation
software will allow the design to fly, it does not necessarily mean that the design could
actually be constructed. So theoretically the aircraft could meet the design requirements
necessary to perform rescue missions at high altitude, however the only way to definitely
determine whether the designs meet criteria would be a real world construct. Further time
needs to be committed to further evolve the designs into proper VTOL designs on the
computer before a true model could even be considered at my current budget.
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Conclusion
I created twenty-three models up to the time this paper was written, though none
of them are capable of true VTOL (Vertical Take-Off/Landing) capabilities. None of the
aircraft are capable of successful transition between vertical flight and horizontal flight,
and as such, the project has not completed.
As the project is of an engineering nature, and is an effort to experiment with
VTOL designs concerning specific criteria, conclusions can only be stated as current
progress, and results change as the designs do. The project cannot reach a natural point of
termination, as there are always factors that can be changed in an effort to increase the
efficiency of the models, and ways to create alternate designs to match the same criteria.
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Acknowledgments
Thank you to Mr. McGinnis from MC squared designs for introducing me to the
X-Plane® software I used. Thank you to Mr. Spangler for helping me through the process
and establishing contacts for me to speak with. Thank you to my family for being
supportive of my interest in aircraft. Thank you to Mr. Austin Meyers of Laminar
Research for designing X-Plane.
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Works cited
“Flight Ceiling” Wikipedia: the free encyclopedia. 2004. 18 April, 2007
http://en.wikipedia.org/wiki/Flight_ceiling
“Flying Bedstead” Wikipedia: the free encyclopedia. 19 February 2007. 17 April, 2007
http://en.wikipedia.org/wiki/Flying_bedstead
“Flight Control Systems” Wikipedia: the free encyclopedia.17 April. 2004. 18 April
2007 http://en.wikipedia.org/wiki/Flight_control_system
“Dornier Do.31” Unreal Aircraft: Beating gravity. 2005. 17 April 2007
http://www.unrealaircraft.com/gravity/do31.php
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