0832

Item 0832

OTHER: Aircraft - Gyro/Heli - (w/ 50/50 power split) & Two Propellers

Gyro/Heli II

Unified Gyrocopter & Helicopter (compound in future?)

Overview:

A theoretical and preliminary design for a hybrid helicopter/gyrocopter, where 50% of the engine power goes to the rotor and 50% to the 2 propellers.

Drawings:

Overall Conceptual Outline: The rotor and the two propellers are located together, between the pilot and the engine.

Varying the pitch of the port propeller offsets the torque of the rotor.

The engine is direct-coupled to the sun gear of a planetary reducer (primary reduction). The planet gear holder drives the pinion and ring (secondary reduction), which, in turn, drives the rotors. The propeller blades are drive by belt from the outside circumference of the ring gear.

There is a "tube' through the center of the transmission which is used to structurally connect the front and rear of the fuselage.

Features:

Power Splitting: The pilot's throttle controls the total amount of power being delivered. The planetary reducer automatically splits the power 50/50 between the rotor and the propellers.

Rotor Governor: A rotor governor automatically controls the rotor's collective pitch to maintain a constant 100% (operational) RRPM. DESIGN: Control - Flight - Governor - Hydraulic

Offsetting Rotor Torque: The pitch of the left hand propeller can be varied from reverse thrust to full forward thrust.

►Power Splitting between Rotors and Propellers:

General Gyrocopter Data from Homebuilt Rotorcraft:

If ship's gross weight is 650 lb then there must be 325 pounds of static thrust.

An efficient prop will develop around 5 pounds of thrust per horsepower.

It will take at least 65 HP to develop 325 pounds of thrust.

Torque Calculations based on 50% of power to Rotors and 50% of power to Prop:

Rotor [Torque x RPM] = Prop [Torque x RPM]

Engine is 65 HP

Operating Rotor RPM is 600

Assume; operating Prop RPM is 2400

Horsepower [HP] * 5250 = Torque [Q] x RPM [RPM]

Therefor Torque [Q] = (Horsepower [HP] * 5250) / RPM [RPM]

Rotor [Torque] [Q_R] = (Horsepower [HP_R] * 5250) / RPM [RPM_R] = (32.5 * 5250) / 600 = 284.4 lb-ft

Prop [Torque] [Q_P] = (Horsepower [HP_P] * 5250) / RPM [RPM_P] = (32.5 * 5250) / 2400 = 71.1 lb-ft

►Rotor Governor:

Maintain constant 100% (operational) RRPM by varying the collective blade pitch:

A mechanical rotor governor automatically controls the collective pitch of both blades. The minimum allowable pitch is that which will be appropriate for autorotation. The maximum allowable pitch is that which is appropriate for maximum power.

Alternative: This mechanical governor consists of small weights that move outward by centrifugal force. The centrifugal force is created by the rotational speed of the rotor hub. The movement of the weights on the governor is in the plane that is normal (at right angles) to the axis of the mast. This arraignment will eliminate changes in G-forces from effecting the governor. Springs hold the weights in and centrifugal force moves them out.

Offsetting Rotor Torque:

The torque of the rotor (profile and induced drag) must be offset by the propeller or vertical fin(s) or (???).

At zero forward velocity, all the drag is generated by the rotor (profile & induced drag).
At low, accelerating forward velocity, all the drag is generated by the rotor (profile and induced drag) but some of the propeller's thrust must be devoted to accelerating the helicopter mass, which is on the for-aft centerline.
At high forward velocity, most of the drag is from the fuselage (parasite drag) and it is inline with the fuselage. Some drag is still generated by the rotor (profile and induced drag) plus some drag from the H-force.

The propellers thrust must offset the thrust of the rotor. This thrust must be located approximately 2-1/2 feet to the right of the centerline during hover and move toward the centerline as the forward speed increases. Therefore, consider 2 propellers, one on each side of the mast. The starboard propeller has a fixed pitch and the port propeller to have a variable pitch. This variable pitch would not move to a feathered position but to a flat-on position or a reverse thrust position during hover.

Prop Pitch Control:

Prop pitch control is required to offset the yaw caused by rotor torque.

The values in next two lines come from the Power Splitting segment above:

The prop thrust is (1/2 of 500) = 250 pounds of static thrust.

The rotor torque is 656.25 lb-ft.

At the start of ground roll, when taking off, the propeller is required to

Offset the rotor torque of 656.25 lb-ft.
Direct all of its thrust backward, to build up forward speed as quickly as possible.

Therefor the length of the moment arm of the propeller will be 656.25 / 250 = 2.625 feet. If the center of thrust on the propeller blade is at 80% of its radius, then the propeller must have a 6.56 ft. diameter. Having a movable rudder (or twin movable rudders) linked in with the propeller pitch yaw control can reduce this diameter to a reasonable size.

Drag and Forward Velocity:

The drag (profile and parasite) will always be greater on the right hand side of the craft therefor in straight flight the starboard prop will be set at a slightly greater pitch then the port prop.

Overrunning Clutch:

A overrunning clutch will be required on the rotor mast to allow the rotors to continue turning in the event of a disabled drive. The rotor governor will automatically set the collective pitch of the rotors to the autorotative setting

Method of Operation:

Takeoff:

Lock wheels.

Set port propeller to 'reverse thrust' position for takeoff. A device for measuring forward velocity could do this automatically.

Hold down collective lever.

Increase to full power and wait for the power train to come up to maximum speed.

Release collective lever.

Pray.

Landing:

Jump

Advantages:

Vertical takeoff.

Faster forward speed then a gyrocopter and helicopter, because of its compound configuration.

Eliminate possible loss of operating RRPM.

Last Revised: February 2, 2001