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 AirFish-8
is
a 17m wing-in-ground craft constructed by the Airfoil Development
(AFD) in the Germany as a prototype craft for commercial
production. It is designed with a capacity of six passengers and
two crews or, alternatively, 750 kg payload and two crews. The
design is based on earlier AirFish design principles and features a
classic Lippisch's reverse delta wing
configuration. Classification of the craft
was first handled by Germanischer Lloyd in the Germany and later by
the Lloyd's Register in Australia. The
AirFish-8 provides efficient low cost transportation at intermediate speeds between that of the typical ocean going vessel and the
conventional aircraft.
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Certification
by International Authorities
Whilst out of ground effect capability is
very attractive to some operators such as the military, it is
unfortunately very much a "two edged sword" with regards ground effect
vessel registration, pilot qualifications and particularly "air traffic
control" considerations in the public sector. A ground effect vessel
which is capable of flying out of ground effect is legally defined as
an aircraft. This aircraft certification, whilst quite achievable,
considerably increases all construction and operational overheads when
compared to a marine craft.
The major capital cost advantage of ground effect vessels over aircraft
is their classification as marine craft. This classification applies to
all construction, registration, operator licensing and maintenance
requirements and allows a lower construction cost as opposed to an
aircraft or helicopters production cost.
The operating
capabilities of ground effect crafts (WIGs) have been divided into 3
categories by the United
Nations International Maritime Organization (IMO):
Type A WIGs being
operating in ground effect only, not exceeding one wingspan in height
above the surface.
Type B WIGs under the
joint jurisdiction of IMO and ICAO (International Civil Aviation
Organization), and being able to leap up to 150 meters into the air for
shot period of time using kinetic energy but not being able to sustain
flight at an
increased height.
Type C WIGs being an aircraft under
ICAO jurisdiction that has the capability of extended operation in
ground effect mode.
Under
the IMO
legislation, the AF8 is classified as a Type A WIG craft, in the
category of marine vessel. In
order for
the
technology to become widespread and accepted internationally, it is
imperative that AF8 is certified by an international certification
authority. Such certification is a powerful endorsement to the
technology's viability and safety. Our AF8-001
was previously certified by Germanischer Lloyd in Germany. This,
according to many, is indeed a
landmark in the development history of WIGs, since no other WIGs has
ever achieved that status.
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Strength
and Competitive
Advantages of AirFish-8 Ground Effect Crafts
High
Speed at a Lower Cost
Conventional aircraft in their various forms for
particular uses are generally very expensive. Boats on the other hand,
while having their advantages, are also plagued with limitations such
as speed limitation imposed by water drag with higher boat speed. AF8
ground effect craft however, functions as a boat at slow speeds and
cruises at air cushion ground effect at medium and higher speeds. AF8
has many distinct advantages over other conventional
maritime transport modes:
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High speed - AF8 take-off at 50
knots and cruises at 86 knots,
and can travel at a faster speed under special load and wave
conditions. It could
traverse the sea and
intervene for control of sea lanes at a speed just less than that of
contemporary patrol aircraft, but with greater endurance, as it could
set down on the ocean surface for a specific purpose such as search and
rescue or in an emergency.
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High lift-to-drag(L/D) ratio – In
general, WIG’s L/D ratio is
much higher than a turboprop aircraft in free flight, hence
significantly lesser
power is needed for the same payload. |
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Fuel
– AF8 uses a
V8 car engine with
unleaded Octane 91 fuel for low greenhouse effect. V8 Engines have been
around
for several decades and have been
fine-tuned to achieve maximal fuel efficiencies. The cruising speed of
AF8 is
approaching
the
speed of most small turboprop aircrafts, yet it consumes only a
fraction of fuel used by aircrafts. In contrast, the top speed of the
fastest
catamarans is
about 50 knots, though they usually cruise below 30 knots. This is
because at
their top speed the fuel consumption is three times more. |
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Low construction cost – AF8 is
certified as a marine
craft, therefore, many stringent Federal Aviation Administration (FAA)
restrictions are not applicable
such as pressurized cabins,
fatigue
tolerance, noise and heat insulation, etc.
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Low insurance cost – Insurance
premium is much cheaper than aircrafts since the AF8 is classified by
the International Maritime
Organization as
a marine craft. |
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No infrastructure needed – and
hence no airport or
seaport tax or fee to pay. The AF8 take-off and lands on the water,
and can be
hauled up the beach or a launching-ram when it is not in operation. |
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Low operation and maintenance cost - For the same cost of a
seaplane of the same capacity, roughly two AF8 can be purchased.
Furthermore it runs at a much reduced operating and maintenance costs.
The estimate
operating cost of AF8 will be in the range of US$ 0.15 toUS$ 0.25 per
pax
per nm which compare very favorably with US$ 1.50 for a helicopter, and
roughly US$ 0.50 for a 10 seater seaplane like the Cessna Caravan.
Further more, no anti
fouling as the hull is
out of water except during the short period of landing and take-off. On
top of that, only car engine
mechanics are
needed for servicing the engine. |
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No aircraft pilot needed – AF8 can
be operated by a
marine captain trained by WigetWorks in house
captain training school,
thus saving on operators cost. |
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Save time – Tourist commuters will
save a lot of time
by bypassing all the cumbersome check-in procedures at the airport,
avoid delay
in retrieving luggage, and no need to commute between the
airport
and their final destination, when the latter is located next to the
water. |
Safety
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If
the engine fails - the runway is always few meters below. The AF8
will
simply glide forward for a
descent of a mere 2
meters. Conventional aircrafts do not have
this
luxury, and thus the need to build in extra redundancy, at an increased
cost. If need be,
AF8 can land on water during an emergency in less
than 300m, much shorter if a water brake can be installed and applied.
Further more, AF8 can be equipped with a jump capability
which allows it to jump over low obstacles in emergency. |
The skipping
stone effect applies when any part of the craft
momentarily hits the water, for example in the event of a sudden high
(but not
freak) wave. There is very little risk of nose-diving which can be a
serious
problem for high speed boats of comparable
size
because the nose of such boats are a lot closer to the water than the
AF8.
The inherent stability of AirFish-8, due to its design that put the
center
of aerodynamic lift and the center of hydrodynamic lift at
substantially the same location. This insures AF8 stability in
transition from waterborne to airborne ground effect states of
operation, and that the
AF8 will not spin, pitch or nose dive in the event
that when the hull, winglet or sponsons touch the water's surface.
The AF8 reverse delta wing has an unique
lower
movement center of pressure while attaining a high lift to drag
ratio, this results in a smaller change in pitch stability that enables
the AF8 to operate in the
ground effect flight with inherent hands-off stability and be able to
maintain a constant angle of attack once set,
and not deviate in roll, pitch or yaw, without operator holding onto
the steering wheel or controlling the steering wheel in any manner.
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Stealth and Low Acoustic Signature
Some of the design features of AirFish-8
provide an inherent stealthiness. For instance, the constant flow of
the smooth air cushion underneath the wings reduces the hydro-acoustic
noise signature which makes it difficult to detect by submarines and
other surface vessels. The engine acoustic emission from the AF8 during
cruise is only 70dB at a distance of 100m, as compared to 95dB for a
typical diesel truck at the same distance, and more than 120dB for
aircrafts.
AirFish-8 is always water hugging hence low radar register, because of its ability to move at speed in
close proximity to the earth's surface. AirFish-8 low physical profile of 4.4m
and low crusing height of 2m reduces the distance at which other
surface crafts or ground stations can detect them using radar because
radar waves do not follow the curvature of the earth but travel in line
of sight. Therefore AF8 can remain in the radar shadow and thus
undetected.
This characteristics has
obvious military implications.
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| Comfort |
Because of the comfort of constant
steadily
flow of air cushion under the wings when the AF8 is cruising in ground
effect, there is hardly any rolling and pitching movement since the AF8
is not touching the waves, there is no sea sickness as associated with
typical
marine travel. There is no
pressure differential as experienced in
aircrafts when the aircraft is climbing or descending.
Because of
the huge saving in traveling time as compared to
boats, holiday makers traveling to far remote places will enjoy a much
less fatigued and smooth sea journey.
Environmental Friendliness
Once
airborne, the AF8 in flight does not disturb the marine life, since it
does not touch the water and there is minimum wake or disturbance of
the waves. When it is
stationary on mooring or on water displacement mode, the
water draft is minimal as compared with most marine crafts. The AF8's
water draft is
only 20cm. To add to environmental friendliness, the AF8 uses
regular unleaded octane 91 petrol
standard for car use, it produces less air pollution.
In addition, the acoustic noise incurred by AF8
during cruise is only 70dB at a distance of 100m, as compared to 95dB
for a
typical truck, and more than 120dB for seroplanes. Most of the
noise is
a result of the propeller’s shock wave. If there is a need for special
low noise requirement, this can be further reduced
using a
ducted fan. It is always water
hugging and hence low radar register. This characteristics has
obvious military implications.
Novelty
Factor
It is only human nature to
pursue speed and novelty. Boats and ships had existed for many
millenniums, but only very few maritime innovations have come about
since the invention of the hovercrafts and the hydrofoils in the 50s
and 60s. Catamarans and trimarans are not new innovations as
they have already existed hundreds of years – they just make them
faster
(though still not quite fast enough). There are now many private
individuals and nouveaux riches who would aspire to own their
aircrafts, or to own a “big boy’s toy” that are new, exciting and
unconventional. In this regard, the AF8 will surely satisfy a lot of
curiosity and pent-up demand for faster, fancier, queerer and
more-out-of-the-world mean machine.
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Weakness, Constraints
and Limitations
WIG
technology has been
around for almost half a century, and the few attempts to commercialise
it have
not been successful. We shall attempt to list as
many of the problems and obstacles to the successful commercialization
of WIGs and discuss partial solutions to alleviate, if not overcome,
them.
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Preconceived
prejudice and conservative mindset
towards new products.
Such prejudice is not uncommon whenever there is a new product or
new technology that threatens and challenges the status quo. When the
Wright brothers first flown in 1903, many would have thought that
commuting by aircrafts would be suicidal. Unfortunately such narrow
mindset and prejudice will always hinder the progress of the technology
and put them in a catch-22
situation. WigetWorks is working on a program to educate the general
public about the WIG technology, and to carry out extensive
demonstration using both AF3 and AF8-001 to show that the ground effect
technology is
safe, economical and exciting.
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Confusion
between aircrafts and marine crafts. The International Maritime
Organization has 3 classes of WIGs, namely Type A, B and C. AF8
belongs to class A and hence
it is strictly a marine craft even though it looks more like an
aircraft,
and possesses far more aircraft characteristics than the marine crafts.
Because of this confusion of air-versus-marine status, many aircraft
builders are reluctant to touch it because they think it is a marine
craft, and many ship builders are reluctant to touch it because they
think it is an aircraft. With sufficient education and publicity in
recent years, this confusion is slowly but surely being dissipated.
WigetWorks will continue to bring about more awareness of AF8 official
marine status.
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Design of
WIGs requires both aerodynamics as well as hydrodynamics expertise.
Because of AF8's hybrid and somewhat confused nature, the design and
development of WIGs require understanding and expertise in both
aircrafts and marine crafts. There are many competent aeronautical
engineers around the world, and there are many skilled naval architects
too. But there are very few who know both well enough to design WIGs
effectively. It is a vision of WigetWorks that 10 years from now WIG
will hopefully be a household word, and that mainstream universities
may start to offer courses in Bachelor in WIG engineering.
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Limitation
in high seas and rough weather. The limitations of WIG crafts
are primarily concerned with sea states. Theoretically Lippisch type
WIGs
are capable of clearing the water/ground by up to half the wing-span
during cruise. The AF8 can cruise at 2m clearance over 2m waves. While
with this cruise
altitude it is still barely enough to operate in rough seas where the
wave height often rise to more than 5m. There is no solution to this
limitation except to disallow the craft from operating in rough seas or
foul weather. In any case, most marine crafts of comparable size to AF8
would not sail in similar conditions anyway, so AF8 is not doing any
worse. In the tropical coastal water, it is estimated that AF8 should
be capable of operating at least 90% of the daylight hours. As and when
WigetWorks progresses to commercializing larger WIGs, the water
clearance altitude will improve with the larger wingspan, and it is
conjectured that by about the size of a 40 seater, it should be able to
fly across some open seas, such as that from Singapore to Medan or
Jarkata.
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Restriction
to no flying at night, at least for now. However, AF8 can be
equipped with search-lights, sophisticated radar and obstacles
avoidance devices, hence theoretically it can be flown at night. In its
early stage of adoption however, it would be unwise to operate it
without natural visibility. However, because AF8 can
fly so much faster than boats, it can cover 4 to 10 times the distance
that a boat can cover during the daylight hours, thus this
no-fly-at-night limitation is significantly mitigated.
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| AF8 Product
Specifications |
Dimensions
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Length,
overall
Length, fuselage
Width, overall
Width, fuselage
Height, overall
Length, cabin
Width, cabin
Height, aisle
Baggage compartment |
17.22 m
13.50 m
15.60 m
2.08 m
4.40 m
4.00 m
2.08 m
1.61 m
1.50 m3 |
Masses |
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Empty
MTOW
Useful load
Fuel
Crew
Payload
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3,215 kg
4,310 kg
1,095 kg
280 liters
1 or 2
750 kg
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General |
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Construction
material
No. of seats
Cabin interior
Draft hullborne
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FRP
2 to 8
Air-conditioned
0.20 m
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Propulsion |
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Main engine power
Fuel
Fuel consumption
No of propellers
Propeller diameter
Optional water drive
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505 hp
Unleaded 91
60 lliters/hr
2 nos.
2.2 m
25 hp
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Performance |
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Speed (Take-off)
Speed (Cruising)
Speed (Taxi mode)
Speed (Displacement)
Speed (Auxiliary drive)
Take-off wave
height
Max wave height
Max. cruise height
Range at max
cruise
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50 kts
80 - 90 Kts
40 kts
10 kts
6 kts
0.5 - 1 m
2 m
2 m
380 nm, 700km
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Certification |
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GL/LR
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Operational Limits |
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Max Operational Wind Speed
Waterborne maneuvering
Take-off (headwind only)
Cruise in ground effect
Landing (headwind only)
Mooring
Max
Sea
State
Take-off
Cruise in ground effect
Landing (normal)
Landing (emergency)
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25 kts
30 kts
30 kts
30 kts
45 kts
0.5 - 1.0 m
2.0 m
0.5 - 1.0 m
2.0 m
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AirFish-8 Standard Equipment
Fitout
Flight Systems
The
AF8 aerodynamic control systems incorporate dual aviation standard
manually powered cable linkages, pulleys and mechanisms for both low
maintenance and rugged reliability.
Avionics and
Navigation
The AF8
cockpit is well planned for efficiency and enhanced safety.
The fully integrated flight control system and avionics suite provide
state of the art instrumentation designed to ease the flare captain’s
workload within a comfortable, low fatigue environment.
Standard equipment includes single marine VHF radio, global positioning
system (GPS), radar collision avoidance navigation system, altimeter
and air speed indicator, magnetic heading system, navigation lights. 
Engine
Instruments
Tachometer, oil pressure indicator, oil Inlet
temperature, low oil
warning, DC voltmeters and ammeters for both main and emergency battery
circuits, generator charge and failure indicator, fuel level indicators
for each tank, fuel low level indicator, remote fuel shutoff system,
water detection system, fire protection system.
Flight
Instruments
Airspeed Indicator (ASI), clock, magnetic
compass, pitch and roll
indicators, laser altimeter and indicator, ground speed indicator.
Environmental
Fresh air vents to all seats , windscreen
demisting.
Electrical
Power
DC 12 Volt, dual circuit system, automatic
charge monitoring and
switching system.
Exterior
Lights
Searchlight controlled from captain’s
position, international
regulation navigation lights, and single yellow strobe high speed craft
light.
Fuel System
In the wing fuel storage with electric fuel
pumps and remote shut off
valves.
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Market Potential
• Tourist
resorts shuttle
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High speed water taxi
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Private transportation / recreational craft
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Oil rig shuttle
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Freight for high speed high priority distribution shuttle (hub &
spokes operations)
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Postal mail shuttle in under-populated areas
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High speed air/sea ambulance
• Disaster response
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Coast guards and marine police
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Combat search & rescue
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Special operations - infiltration & extraction
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Maritime surveillance & sovereignty control
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Fast response interceptor for piracy and illegal migrants
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Military reconnaissance missions
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Anti-submarine operations
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Fresh seafood transport
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Mine clearing and laying
The largest commercial market is obviously
found in tourists resorts, especially archipelago countries such as the
Maldives Islands, Phuket Islands in Thailand, the Indonesian and
Philippine islands, South Pacific/Oceania Island nations, the Greek
islands, Monaco/Nice, the Caribbean’s, etc. In most of these places,
infrastructures such as airports are not commonly available yet the
demand for high speed and comfortable transportation is high.
The second largest market segment is
likely to be government agencies such as law enforcement, coast guards
and the militaries. In the future, the largest market segment is
potentially found in the ferry and freight industries, which put WIGs
in direct competition with the current domination of high-speed
catamarans.
Potential Area of WIGs Operations
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AF8 Design
Characteristics
General
The craft is designed to set in the water
relatively flat when at rest on displacement mode with the low slung
fuselage, the sponsons
and the trailing edges of the wings acting as the float, and for the
center of pressure to substantially correspond to the center
of lift when
the craft is planing. The lower surface of the wings are bounded by the
two rear trailing edges, and when the craft is moving forward, an air
cushion is created beneath the wings. This air cushion formed when the craft is moving forward
on water, particularly when the trailing edges are still under the water, is in effect a stagnation pressure
area below the wings and is separated from the outer air flow by the
sealing-off effects of the trailing edges of the reverse delta wings.
Such a design also produces an aerodynamic seal when the craft is
cruising low in the ground effect operation region whereby the air
cushion is exerting a higher pressure on the lower surface of the wings
and aids in providing low induced drag for the craft.
As the forward speed increases, the water and air pressure under the
wings is building up. The craft is moving forward while the bottom of
the sponsons, the hull step and the
various area of the wings trailing edges are planing over water. This
occurs without
substantial shifting of the aerodynamic upward pressure center while
the craft is still in planing contact with the water. As the forward
speed increases further more, the wings will generate more lift and
because of ground effect, the air cushion under the wings will produce increased pressure with
increased speed to aid in lifting the craft.
Flaring
in Ground Effect 
The AirFish-8 was designed to flare only
in ground effect and will not maintain a constant flare height greater
than one wing span. Under standard conditions
with full load, the craft when flaring is inherently stable and will
not oscillate. The craft is designed with minimal vibration and is
generally comfortable for the passengers. The structure of the craft is generally
composite material with some sections to be light alloy material.
The inherent stability of AirFish-8, due to its design that the center
of aerodynamic lift and the center of hydrodynamic lift are at
substantially the same location. This insures craft stability in
transition from waterborne to airborne states of operation. Moreover,
in the event
that when the hull, winglet or sponson touches the water's surface, the
craft will not spin, pitch or nose dive; The craft will not stall or oscillate
during flaring,
taking-off or landing modes.
Flare
Controls
Under standard conditions, with full load,
the craft is designed to operate in the flare mode(cruising) with
hands-off and be able to maintain a constant angle of attack once set,
and not deviate in roll, pitch or yaw, without operator holding onto
the steering wheel or controlling the steering wheel in any manner. The combination of hydrodynamic
hull and the aerodynamic aircraft wings enable the AF8 to achieve an
equilibrium while cruising(flaring) in ground effect and thus the AF8
can be easily trimmed to flare without the necessity of constant undue
correction.
The height
from the surface to the craft, while flaring, is selected by trim and
throttle and is automatically held without further adjustment. Trim is
performed by means of a trim control with an adjustable stop device on
the steering wheel via spring loaded system, operated manually.
Steering is done by a steering
wheel which operates the control surfaces both on the vertical and
horizontal tail, and on the winglets by means of mechanical cables and
push rods. Operating of the control surfaces by the steering wheel for
a turn, is done in such a manner that the craft makes a coordinated
banking maneuver with the craft simultaneously reaching the altitude
required for such a turn.
Take-off and Landing
Take-off is
performed by increasing the throttle. The transition from displacement
mode (means the state when the craft is on the water) to step taxi mode
(means the state when the craft is moving at sufficient speed on the
water such that the hull and sponsons are planing), and then to the
flare mode occurs automatically, without any particular demands on the
operator.
Landing is
performed by reducing the throttle to lower the speed of the craft
enough to come out of the flare mode and enter the displacement mode.
Aero-Hydrodynamic
The
aerodynamic hull is designed to be both a displacement hull as well as
a planing hull when the AF8 is in contact with the water. The upper
surface of the hull, together with the main wings, are designed to
provides aerodynamic lift and assists in stabilizing the AF8 when
airborne within the ground effect region just above the water or ground
surface over which the AF8 is traveling. The AF8 hull has a
longitudinal axis coinciding generally with the fuselage of the craft.
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Copyright
Wigetworks Pte Ltd. All Rights Reserved
 123
Genting Lane #05-04 Yenom Industrial
Building Singapore 349574
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