Tip Jet Helicopters. Hoyt Stearns' helicopter patents. Cross
flow fans. Pressure Jet helicopters.
Stearns' latest helicopter page (Mosquito ultralight helicopter --
unfortunately it has a tail rotor :-( )
This is a slide presentation I gave twice in 1986
to American Helicopter Society meetings in the Phoenix,
Arizona US area regarding
my torqueless electric air pressure jet tip propelled
helicopter designs and an advanced high speed
helicopter using the moments from an offset flapping hub and
shaft torque to unload the retreating blade. I was delighted
honored that Ray Prouty, Bob Head and other notables attended.
I was granted two US patents for these ideas:
4,702,437 and 4,720,059.
The patents are expired due to the high maintenance fees from the
patent office :-(.
You're free to develop these ideas. Please keep me informed of any work
you do in this area.
Thanks to Eugene K. Liberatore, Bruno Nagler's chief engineer for some
consulting on these projects.
patent for the blade tip electric cross flow fan driven helicopter
patent for using offset flapping hub moments to unload the retreating
Since there's no torque, there's no need for a tail rotor, however some
means of yaw control is required. In my design, a small
electric motor is coupled to the drive shaft. For a
conventional US left rotating from the top helicopter, envision it
To yaw left, just grab the shaft with a brake, for right yaw, power the
shaft a bit with a small motor. Practically, the motor is used
for both left and right yaw, acting as a generator for left yaw and
motor for right yaw.
Since there's no tail and the rotor shaft tilts for rotor plane
control, there's no chance for mast bumping or rotor/tail contact.
Since the main rotor shaft is free-wheeling, pitch axis trim
can easily be achieved by fore-aft movement of the shaft.
A backup battery could be used for about 30 seconds of power
at the end of an autorotation in case of
engine-alternator failure or fuel exhaustion.
The tip fans could also be constructed to lower the pressure inside the
blades allowing for boundary layer absorption, increasing the
efficiency still further.
A chart showing how new magnetic materials are so much stronger that
they, along with Metglas® amorphous iron, Kevlar®, and
nanotube fibers allow for electric motors to be designed with up to 8
horsepower per pound of weight!
Not in the chart: Neodymium Iron Boron (NeFeBo) magnets are even
better. These new magnets are spectacularly strong.
One inch cubical NeFeBo magnets are a real danger if not handled
properly -- they can easily crush a finger.
The latest semiconductor technology including insulated gate bipolar
transistors and power field effect transistors allow
for efficient electric invertors to drive these powerful motors.
Even for conventional shaft driven helicopters, motors of
such high power to weight ratio and efficiency could be used
drive a tail rotor, avoiding the failure prone tail rotor drive shaft,
gearbox and bearings.
An early Nagler torqueless helicopter
Helicopter pioneer Dr. Bruno Nagler
See my Bruno
Nagler web page
A torqueless pressure jet helicopter proposed by Nagler's company,
Note the T-bar stick that predates the Robinson R22.
A typical cross-flow fan blade.
I t seems other engineers think cross flow fans are practical.
An example of how electrically driven cross flow fans may be used in a
helicopter blade tip.
The speed of the fans can be modulated to inertially dampen blade tip
pitch variations, allowing higher speed forward flight.
The rotation direction of the fans is anti-coning, about 50 pound-feet
(68 Newton-Meters) of downward torque. This should increase
According to motor engineer Peter Campbell, two horsepower (1.5
KW) per inch (2.54 cm) of lengh for a one inch
diameter motor should be
achievable. The fans spin about 200,000 RPM bringing the fan
edge to the transonic region.
In a Nagler type pressure jet helicopter, most of the power is lost in
the air ejected from the trailing edge blade tip nozzle, so the
efficiency is rather low. With the fan-in-blade, theres ten
times the air flow, exiting at a lower velocity so the efficiency is
Some calculations about blade tip fan propulsion.
My three dimensional (spatial) extension to a Peaucellier mechanism to
create a virtual pivot. The idea is to simulate a spherical
bearing near the rotor hub, but keeping it well inside the fuselage and
out of the airstream. No swash plate would be required,
just tilting the rotor shaft as in a gyrocopter would work in a tip
Since fully half of the aerodynamic drag in a helicopter is due to the
hub and associated structures protruding into the airstream,
the virtual pivot should minimize that.
Two dimensional drawing of how a Peaucellier mechanism may be used as a
component of a perfect virtual pivot.
Parts you won't need in a torqueless helicopter.
Images of a high speed tip propelled helicopter. The moments created by
the offset flapping hub and some torque applied to the drive
shaft keep the helicopter suspended under the advancing blades.
This completely unloads the retreating blades. As
speed increases, the rotor rotation speed is reduced to keep
compressibility effects from occurring on the advancing blades.
The colored sticks represent the moment components of this
configuration: roll, pitch, yaw, and the sum, showing
how the helicopter can be maintained in equilibrium with this
As the forward speed increases, the hub is tilted more forward and
right and the rotor RPM is decreased.
The hub position may be moved laterally for different flight regimes.
Since there are five more control degrees of freedom in this rotor
configuration, it's likely a computer control system would