Finally
A Tiny, But Practical
Ultralight
Helicopter! |
| Pilot Yasutoshi Yokoyama stands
by his GEN H-4 ultralight helicopter after a demonstration flight at he
Experimental Association's AirVenture 1998. Hundreds of people by the run-way
fence saw the flight. (Photo by Kerry Cartier) |
|
By
Kerry Cartier
Imagine having a new engine with one of the
highest power-to-weight ratios in the world. Imagine putting it on one
of the smallest helicopters in the world. Imagine an ultralight helicopter
that can carry a 185-pound pilot. Now, stop imagining, because this ultralight
helicopter flew at the Experimental Aircraft Association (EAA) AirVenture
1998 at Oshkosh, Wisconsin!
Weighing just 168 lbs. empty, the ultralight
helicopter has four GEN 125 engines that drive two sets of rotor blades.
Each 125cc engine weighs just 6.2 lbs. And develops 10 horsepower, or over
1.6 horsepower per |
| pound! These tiny two-stroke engines are air-cooled, two-cylinder,
and horizontally opposed, with magnesium crankcases and aluminum cylinders.
The tiny engine develops its 10 horsepower at 8,000 to 8,500 RPM, with
a 500-hour TBO. Gennai Yanagisawa, an automobile designer and engineer
who designed Japanese cars in the 1950s and 1960s, designed the GEN 125
engine. In 1970, he started his own business, Engineering System
Co. (ESCO), which produces ultra-precise automated assembly and inspecting
machinery. As a hobby in the 1990s, he developed the small, light, powerful
GEN125 engine. It has been used in motorized hang gliders, motor-ized paragliders,
a wind-powered bicycle-and now, on a successful ultralight helicopter. |
UNIQUE DRIVE SYSTEM
The unique GEN H-4 ultralight helicopter
is made by ESCO in the city of Matsumoto, in Japan. It has four engines,
each with its own clutch, starter, and CDI ignition system. The four engine
drive an integral reduction gear drive and counter-rotating rotor shaft
system operates two sets of coaxial rotor blades turning in opposite directions
to minimize torque.
Rather than use a heavy conventional
rotorhead with a swash plate and articulated rotor blades, the GEN H-4
ultralight helicopter has rotor blades that are ground adjustable. They
are fixed pitch or "rigid rotor" in flight. Instead of changing rotor blade
pitch to control direction and lift, the GEN H-4 takes a hint from gyroplanes
and tilts the whole engine, reduction |
| This close-up of the rotorhead
shows the GEN H-4 ultralight helicopter as flown at Oshkosh. It shows
the two contra-rotating 13. 1 foot diameter rotor blades, three of four
GEN 125 10 -horsepower engines, the exhaust collector ring, and part of
the airframe. (Photo by Kerry Cartier) |
|
| drive, and rotor blade assembly side-to-side and fore-to-aft. This
gives the controls the simplicity of a gyroplane and the capabilities of
a helicopter. |
| Seen from the right rear side,
the GEN H-4 ultralight helicopter has two contra-rotating 13.1-inch diameter
rotor blades, four GEN125 10-horsepower engines, an overhead control bar
like an old Bensen Gyrocopter, a gas tank, shoulder harnesses, seat, and
landing gear with knuckle rollers instead of wheels. (Photo by Engineering
System Co., Japan) |
|
UNIQUE CONTROL SYSTEM
The whole rotorhead is supported on a gimbal,
just as with a gyroplane. The rotorhead is tilted towards the direction
of travel by the control bar, which is placed in front of the pilot. When
the GEN H-4 control bar is moved to the left, the helicopter goes to the
right, just like the overhead stick on an old Bensen Gyrocopter.
An electrical yaw control system allows upper
and lower rotors to turn at different speeds, dynamically changing their
speeds so the helicopter does not drift in an unexpected direction. The
yaw control system eliminates the need for a rudder or tall rotor. |
| Additional stability comes from putting two curved rails under the
whole rotorhead, which make the ultralight helicopter so stable that it
can be flown handsoff! |
| Gennai Yanagisawa, designer
of the GEN H-4 ultralight helicopter, holds a 10-horsepower, 6.2 lb. GEN125
engine which he also designed. The helicopter has four GEN 125 engines.
(Photo by Engineering System Co., Japan) |
|
EIGHT YEARS OF RESEARCH
With innovations like these, it's obvious that
a lot of research has been done. The GEN 125 engine was first tested in
a model helicopter with counter-rotating, rigid rotor blades from 1990
to 1994. A carbon fiber/Kevlar composite rotor blade airfoil was developed
by an aerospace research institute in Japan.
The first prototype was the kind of helicopter
that all boys dream about, the "Boy's Dream Helicopter" or BDH-1, in 1994.
On this helicopter, the pilot hung from straps on the rotor mount. Twin
engines turned the coaxial rotors with long shafts, belt reduction, and
universal joints. With two GEN 125 engines in tandem, the 20-horsepower
BDH-1 was not powerful enough to fly. It was very popular at an aerospace
show in Japan.
A third engine was added on the BDH-2 prototype,
resulting in a flight on Dec. 26, 1996. The three engines were run in-line
on the same crankshaft,. es-sentially making a six-cylinder, 30 horse power,
375cc engine. This helicopter had five hours of restricted flight and more
than two hours of free flight, confining both rotor blade and engine reliability.
However, if any one of the three engines failed, there was no reserve power
to sus-tain flight. |
| A fourth engine was added to in-crease safety
on the BDH-3, the third prototype. The design of the power unit changed
from three in-line engines to four separate engines connected radially,
with power takeoffs in the center. Because of the compactness of the new
power unit, it was possible to put it above the pilot on the gimbal mount.
After four hours of Jump tests and almost two hours of free flight, this
helicopter was exhibited at EAA’s Oshkosh airshow in 1997. |
GEN H-4 IS FOURTH IN A SERIES
The fourth prototype, the BDH-4, was given the
name GEN H-4 for "Gen," the nickname of its designer and com-pany president,
Gennai Yanagisawa. In Japanese, "gen" means "generate" or “origin,” an
appropriate name for his fourth helicopter design. By September 30, 1998,
the GEN H-4 had been flown more than 50 times, with more than 10 hours
of free flight, including the flight at Oshkosh.
To date, most free flight has been conducted
at low altitudes and at low airspeeds. The GEN H-4 climb rate depends on
gross weight, and a service ceiling of 10,000 feet has been calculated.
Similarly, cruise at 75 percent power has been estimated at 55 mph with
a 185-lb pilot and would use less fuel with a lighter pilot. When asked
for more specific figures the manufacturer said they were not available
because further flight testing is needed to determine accurate performance
figures under actual flight conditions. Estimates, they said, could be
misleading.
Specifications for the GEN H-4 reveal that
it is a very tiny ultralight helicopter with 13’1” rotor blade diameter,
a very light aluminum tubing airframe, and very light knuckle rollers instead
of wheels. Since the empty weight of the GEN H-4 is only 168 lbs., it is
picking up 129 percent more than its own weight with five gallons of gas
(31 lbs.) and a 185-lb. pilot. |
SIMPLER CONTROLS THAN
TYPICAL HELICOPTER
The Japanese pilot who demonstrated
the GEN H-4 at Oshkosh, Yasutoshi Yokoyama, learned to fly the GEN H-4
in about three hours. This is significant because Yokoyama has no pilot’s
license of any kind and had no experience in flying a helicopter until
he learned to fly the GEN H-4. He is not a pilot; he is an engineer with
almost 20 years experience in aviation, specializing in airplane and powerplant
development maintenance. He knows the GEN H-4 well because he assembles
it and tunes the engines before flight.
Based on Yokoyama's experience,
the GEN H-4 helicopter should be easier to fly than a gyroplane. Because
it as an ultralight helicopter, a pilot would not need an expensive helicopter
rating. |
| From the pilot's viewpoint,
the GEN H-4 ultralight helicopter controls are: master or kill switch to
the left of the overhead control bar, digital engine tachometer to the
right; from the left, yaw control switch, four engine start buttons and
red engine-out lights, and throttle lever. (Photo by Engineering System
Co., Japan) |
|
Flight controls are simple. The
control bar moves the whole rotorhead for pitch and roll control. Yaw is
controlled with the left thumb, operating a switch for the electrically
controlled differential gear in the yaw control system. The master or kill
switch is above the yaw control switch. The throttle lever, which con-trols
altitude and climb rate, is operated with the right thumb. Starter buttons
and red engine-out lights for all four engines are in the center of the
control bar. A digital tachometer that samples one engine also is on the
control bar. Using these controls, Yokoyama skimmed the grass at Oshkosh,
hovering under perfect con-trol several feet up. Because the demonstration
was made at the end of the ac-tive ultralight runway, EAA officials lim-ited
the helicopter's flight to hovering about three feet high.
AUTOROTATION IS NOT NEEDED
An additional safety concern was the
fact that the GEN H-4 helicopter cannot autorotate to a landing because
it has fixed-pitch rotor blades. With separate clutches on each engine,
the helicopter can still fly if one engine quits. The dead engine would
simply drop out of the system, and the other three engines would produce
enough power to stay airborne. If a second engine quits, which is considered
very unlikely, there is still enough power to land safely. Since there
are tremendous odds against three out of four engines failing simultaneously,
there's no need to autorotate to a power-off landing, from the company's
point of view. So, the helicopter has been designed without autorotation
capability for simplicity.
In theory, all four engines could
stop at once, from fuel contamination, for example, so the manufacturer
plans to mount a ballistic recovery chute above the rotor blades. The support
for the chute would be stationary tubing inside the inner rotor shaft.
They are also considering an automotive airbag - under the seat, to cushion
an unexpected impact with the ground. |
SPECIFICATIONS / PERFORMANCE
| Engine.....................
Fuel.........................
Engine Limits...........
Carburetor..............
Rotor Limits............
Airspeed limits.........
Cruise speed...........
Empty weight...........
Maximum weight.....
Rotor diameter........
Height.....................
Length.....................
No. of seats.............
Maximum baggage...
Fuel capacity...........
Oil capacity.............
Fuel consumption..... |
Four (4) GEN125 10-horsepower engines;
125cc two-cylinder two-stroke air-cooled
Minimum 87 octane automotive gasoline
Maximum RPM 8500 (10 horsepower each)
GEN 125 carburetor
Power on, 8500 RPM (Engine tach)
1000 RPM (rotor tach); Power off, NA
Never exceed speed 120 MPH
At 75% power 55 mph
168 lbs.
385 lbs.
Two rotors, 13'1" diameter
8'
7'6"
1 (Pilot)
None
5 US gallons (31 lbs.)
None, mix 30:1 in fuel
5 gallons per hour |
DEVELOPMENT CONTINUES
Flight testing was done with a 160
lb. pilot and 10 gallons (63 lbs.) of fuel. In the ultralight configuration,
the helicopter carries only five gallons of fuel. Since the ultralight
helicopter carries 31 lbs. less fuel than the prototype, that means 31
lbs. more payload can be carried. So, the ultralight GEN H-4 helicopter
is rated for a pilot weighing up to 185 lbs., larger than the FAA’s "average
pilot weight" of 170 lbs. An upgrade that would lift a pilot weighing 220
lbs. is being considered for the American market.
In the U.S., the completed helicopter
would be fitted with one five-gallon fuel tank and flown in the ultralight
category. Engineering System Co., Ltd., plans to manufacturer the GEN H-4
as an ultralight kit that would take 30-40 hours to assemble. In December,
the com-pany broke ground for its new helicopter manufacturing facility.
The first kits should be available in July, 1999, with a projected price
of $25,000 US (3,000,000 Yen), FOB Japan.
According to the manufacturer,
the GEN H-4 should be a desirable helicopter because of low price, light
weight and small size, built-in stability that cuts training time significantly,
ease of trans-port to the flying site, and operation in the ultralight
category without needing to license either the helicopter or the pilot. |
Copyright 1999 by Kerry
Cartier. All Rights Reserved.
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