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The Technology
THE DIFFERENCE
As the name says, a flying wing is "all wing". Conventional aircraft have a large fuselage and a tail
resulting in more weight, more parasite drag and more interference drag, all without contributing any lift. The flying wing improves effenciecy by incorporating everything into the wing.
The Idea
HOW LIFT IS GENERATED
Theoretically the most efficient aircraft concept is the "FLYING WING". Why?
A body heavier than air can only fly when aerodynamic lift takes effect.
Lift is generated when the body moves through air so that the air that flowing around it excerts the appropriate differences in pressure. Inevitably drag is a product of motion
through air. Lift is useful while drag wastes power.
THE OPTIMUM
We want as little drag as possible for the amount of lift needed for flight. Elimination of those parts of
aircraft that produce only drag; the fuselage and the tail, leaves only a flying wing.
An example of this principle of optimizing the lift to drag ratio by choosing a flying wing design is the solar powered "Pathfinder" which reached an altidude of 27,000 m during the
NASA-ERAST-Program.
Advantages
CONVINCING ARGUMENTS
Good performance is not the only advantage the flying wing has to offer. There are other very
important advantages which we invite you to examine.
1. Top performance
FASTER TO DESTINATION
The three fastest ultra-light planes are Polaris FK 14, Impulse100 and Fascination D4BK. They
achieve cruising speed from 125 to 145 knots using the ROTAX 912 S engine (the fastest speeds are achieved by using a electric variable pitch propeller.)
VELOCITY OF THE H 3000
The PUL 10 cruised at a 110 knots using only a 80 HP engine and a fixed pitch propeller. For
the following reasons we expect the H 3000 to cruise at speeds comparable to those of the fastest ultra-lights:
A. Reduction of drag by
a.narrow cabin (Tandem seating)
b.lower cabin
B. The propeller is more efficient by
a.having a narrower cabin in front of it
b.placing it in less turbulent air further behind the wing trailing edge
C. The more powerful ROTAX 912 S engine
D. A variable pitch propeller
ADVANTAGES OF THE PUSHER CONFIGURATION
Although the aft position of the propeller seems unusual this
configuration has advantages: The conventional single engine plane with its propeller in front forces its higher velocity thrust to blow upon the fuselage and the center section of the wing, creating additional aerodynamic drag. (To
understand this advantage, imagine a ship with the propeller placed in its bow. It would do extra work blowing water on the ships hull thereupon wasting power.) With a pusher the airplane glides through the air like a jet; the airframe
encountering undisturbed air.
BIG POTENTIAL
We wish to comment on the performance issue; the aerodynamic data on our aircraft came from Dr. Horten.
His designs are famous for safe and forgiving flying characteristics. Since Dr. Horten designed his flying wings there have been revolutionary improvements in airfoil design. These improvements which have been applied to conventional
aircraft have significant possibilities for the flying wing.
2. Unusually wide speed range
Thanks to its light wing loading the PUL 10 was stable and controllable at 35 knots and over a runway it could fly 30 knots in ground effect. This is remarkable for a plane with a
never exeed speed of about 140 knots.
3. Safety and ease of use
Dr. Horten's designs are the result of a lifetime of experience in building and testing flying wings. The PUL 9 and the PUL 10 are his final masterpieces. His flying wings are so
stable that the best test pilots could not make them stall violently enough to spin as long as the C.G. was within range.
QUOTATION OF THE MOST FAMOUS FEMALE TEST PILOT
Germany`s legendary test pilot Hanna Reitsch stated after flying the H II on November 12, 1938:
"There was no possible control movement which could bring the H II into a spin or even cause it to tip over on one wing. With the stick pulled all the way aft and to the right the
airplane rotates slightly in front and descends but accelerates to no faster speed than 90 km/h. This is very useful while flying in clouds when the instruments are frozen."
That testemony is stronger than anything we can say about it.
4. Short take off and landing distance
As a result of the low stall speed shorter takeoffs and landings are possible and the runway need not be paved. Also an emergency landing is less dangerous.
5. Loading advantages
Because the interior of the flying wing is so spacious it may be possible for example for large cargo and passenger aircraft to run on hydrogen some day. Smaller flying wings can
more easily contain larger fuel tanks and more cargo space. As a result of the low wingloading, flying wings can carry more weight.
6. Low production cost
In the global market ability to sell at a competitive price is important. The Polaris FK 14, Impulse 100 or Fascination D4 BK sell for $95,000 to $115,000 complete with the ROTAX 912
ULS engine, ballistic parachute, taxes and no extras. It is realistic to expect to sell a factory built, ready to fly H 3000 for $70,000. There are a number of reasons why the H 3000 is cheaper to build than a comparable conventional
airplane.
a. Compact construction
The flying wing consist of three main parts: two wings and a center section. This saves factory floor space during production. The molds require
less space and the aircraft take up less space while they are being assabled. A containerized flying wing takes up less space so it is costs less to ship.
b. Fewer parts
With no tail and no fuselage and a simpler control mechanism, material costs and labor costs are reduced. Less warehouse space is needed. This makes it
attractive to a manufacturer as well as to a kitbuilder.
c. Modular assembly
The center section and the wings are designed so that the sub assemlies are easily installed in them. This ensures short turnaround time fort he
expensive tools such as the molds and it improves the efficiency of production. With a factory operating on a single shift schedule (with one additional Saturday shift each month) it should be possible to produce 84 units per year. There is
the flexibility to outsource the production of some parts.
d. Homogenous construction with modern materials
The H 3000 is designed to be made of modern materials such as honeycomb or foam composite sandwich assembled with vacuum
layup. Because of the ease with which strength is achieved with a thick hollow wing, the H 3000 can be built with less expensive fiberglass while the weight is kept to a minimum, unlike thin wings of more conventional aircraft. Thin wings
suffer higher stress per pound of wingloading and require so much additional reinforcement that even with carbon fiber they will be heavier than the thicker H 3000 wing.
e. Simple Control Mechanism
The flying wing eliminates three of the control systems found in most conventional aircraft. The rudder, the aileron, and the elevator are
replaced by one elevon on each wing. These are controlled by simple pushrods; no cables or pulleys. ----- This further simplifies construction and reduces the maintanance burden for the owner. The ground steering is accomplished
by differential breaking, using a castering nose wheel.
7. Simpler controls
Because Dr. Hortens designs are more stable and forgiving and because in flight only the control stick is needed, no rudder pedals are used, the H 3000
will be much easier to fly. Dr. Horten called the concept of an easy to fly airplane the Volksflugzeug" (Peoples Aircraft)
8. Better Crosswind Handling
The rudder on a conventional airplane applies a large yaw movement during a crosswind landing. This requires the pilot to have sufficient skill
in cross controling the aircraft to keep its landing and takeoff path straight. This is especially true of tailwheel aircraft. The H 3000 has no rudder so it is less vunerable to crosswind. Once it touches down in a crab attitude the
landing gear causes it to straighten out, much in a manner of the Ercoupe.
9. Less parking space
Without a fuselage or a tail the H 3000 uses less hangar space. 30 such flying wings can be parked on a floor of 800 square meters. This could reduce
the expense of indoor storage.
10. Easy dismantling and transport
Within minutes the H 3000 can be dismanteled into its three parts and loaded on a trailer. Thus the recreational user can store the
airplane in his garage and save hangar rental fees.
11. Lower operating costs and easier maintenance
Everything inside the H 3000 is more accessable; there is plenty of room for hands and tools, there are fewer parts to
maintain, these parts are simpler, longer lasting, require less mechanical attention and are usually less expensive. (For example control rods are less expensive and simpler than elaborate systems of cables and pulleys.)
12. An interesting possibility
Nearly as old as the dream of owning an airplane is the dream of the flying car. The cost and efficiencyof private air travel is limited by
the inconvenience of gound transportation to and from the airport. Even though the H 3000 is not designed as a flying car we should not dismiss the following: the flying wing, when dismanteled, leaves a center section containing almost
everything needed for a car – an engine, a cabin, controls, fuel, and seats. The wings of an H 3000 flying car could be left at the airport. The center section takes up less space than past attemps to make a car out of a long fuselage
and tail section.
A meeting with the German TÜV institute revealed that it would not be difficult for such a vehicle as an H 3000 to receive road certification.
13. Uniqueness
Let`s be truthful. One reason for appearing at an airport in a flying wing is to create a sensation. Therefore let us dare to admit that it would be fun to
have your aircraft mistaken for something from a far more advanced planet. The enjoyment of fame and the attention you will attract is not something of which you should be ashamed.
Future Possibilities
DESIGNED FOR FUTURE DEMANDS
In this chapter , we will look at what kept the advantages of the flying wing from being
realized. But now the flying wing`s time has come.
Why has the Horten flying wing concept not been widely accepted until now?
SCIENTIFIC PREJUDICE
After several flying wings were built and successfully tested during World War II, scietists
discussed the pros and cons of such aircraft.
Today in every graduade school in every university science department, students are told over and over that the labotory test is the final judge and jury for every theory. Science
had not yet matured to this degree of academic discipline in the mid Twentieth Century.
DEVELOPMENT IN SECRECY
An example of this can be seen in the records of a flying wing conference held in Berlin in
April 1943. In this conference, Prof. A.W. Quick predicted that swept back wings would quickly become uncontrollable in a stall and spin easily. This prediction was thoroughly disproven by the flight tests of the Horten flying wings. Today
swept back wings are routinly used. This we submit to the reader as an example of the resistance the Horten brothers encountered with their unconventional aircraft designs.
Research data on flying wings was classified top secret during the war.
AFTER WORLD WAR II
When Göring saw that the war was lost, he ordered the destruction of all flying wings and their
research data. After the war ended, the Allies either confiscated or destroyed most of what Göring had missed. Also developement stalled because the Allied Powers shut down the armament industries, including the German aircraft
industry.
MAIL UNDER CENSORSHIP
The Allies made it extremely difficult for Dr. Horten from working on aircraft as long as he was in Europe. So he emigrated to Argentina. His efforts to do further work on flying
wings was disrupted by censorship of letters to scientists outside Argentina.
And as often happend in history the defenders of convention silenced or stifled the unconventional.
The current state of knowledge
UNFLEXIBILITY OF TODAY`S AIRCRAFT INDUSTRY
Scale, complexity, and growth of the aircraft industry from many small shops
into large conglomerates has left flying wings as a curiosity. This has resulted in an emphasis on profits by lowering cost per unit at the expense of flexibility. There is a fear of the risks in producing anything so radical that it might
not succeed as well as the more conventional things that have proven themselves in the market place.
GIANT PASSENGER AIRCRAFTS ARE PROJECTED
But this is changing. Both AIRBUS and BOEING have calculated that a giant
airliner designed to carry 1,000 passengers will be 25 % to 30 % more fuel efficient if it is built as a flying wing. The flying wing is favored by those who would take advantage of all the space inside the wing to store hydrogen. These
aircraft are expected to use the elliptical lift distribution curve. Dr. Horten used a bell shaped lift distribution curve.
DIFFERENT LIFT DISTRIBUTIONS
There is a consensus among scientists that the flying wing`s advantages are significant
for very large passenger and cargo aircraft that use elliptical lift distribution that require computer synthesized stabilization. However in smaller aircraft the wing twist and bell curve lift distribution needed for
pitch stability impose an induced drag disadvantage that makes the smaller flying wing`s effeciency comparable to that of a conventional plane of the same size, depending upon its cruising speed.
Why the bell shaped lift distribution curve?
The subtle distiction
Horten wanted a flying wing that was aerodynamicaly stable and could be flown directly by hand.
Many attempts have been made to achieve aerodynamic stability with different lift distribution curves. Northrop tested such changes from Horten`s designs. In every case where the lift distribution was changed from a bell shaped
curve, the control characteristics were unsatisfactory. Bell shaped lift distribution is needed not only for best pitch stability, it results also in good yaw stability.
Different lift distributions
In 1982 the single seat flying wing glider "SB 13" (Arcus) with elliptical lift
distribution was tested. It was so difficult to control that it was considered unacceptable for general use. It was also determined that the Northrop B2 flying wing also with elliptical lift distribution would fall like a "stone from heaven"
if the computer that controlled it were shut down.
HORTEN wings fly safe and stable
Thus, for small aircraft used for private air travel, bell shaped lift distribution is
the most reasonable choice. This lift distribution has somewhat more induced drag than that of an ellipse. But a typical two seat aircraft flying at low altitude will cruise at speeds at which most of the drag is parasite drag and the induced
drag is a small fraction of the total drag. Elliptical lift distribution and the need for computer controls that costs several times as much as the aircraft itself, at best, offer only a few knots of extra cruising speed.
As has been verified by well known test pilots our flying wings have been safe and stable. At this time we await the flight test results from the H 3000 with its new optimization. We
intend to keep you informed.
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