ASSEMBLY
The Ultrasport 331 and 496 are available as quick build kits, taking approximately 400 hours of assembly time using basic tooling. The kits include an construction manual, flight manual and full set of engineering drawings.

THE DRIVE SYSTEM
The drive system is special in that the engine is vertically mounted to the seatback and connected to the clutches and main rotor drive shaft directly. There are no belts to slip or break. Light weight was achieved on the drive system by using an aluminium gearbox, main rotor hub and titanium main rotor shaft.

The main rotor gearbox is a 12:1 planetary gearbox which also turns the tail rotor at a 1:1 ratio. The gearbox is oil cooled and wet lubricated with an internal sump and pump and is manufactured to the American Gear Manufacturing Class I standards, rated for 2000 hour TBO time, by the company that also manufactures gearboxes for the AH-64 Apache, MacDonnell Douglas Hornet, and Eurocopter Dauphine. Engine start up is a breeze due to the centrifugal clutch which does not engage the rotors until the engine reaches 2000 rpm. The sprag clutch is a one-way clutch that enables the rotors to continue running in the event of a loss of engine rpm. The clutches, controls, and rotor hub are manufactured under the same aerospace specifications by the company that makes rotor hubs for the Bell 206, the UH-1H Huey, and the AH-1 Cobra helicopters.

FUSELAGE AND LANDING GEAR
The seatback is the strongback for the aircraft, and forms a strong torque box to which everything else is attached. This rigid structure is lightweight but far from fragile. The seat is assembled from sandwich panels of epoxy resin, graphite fabric and nomex honeycomb core. The forward fuselage is essentially a non-structural pilot fairing made from several layers of graphite. The landing gear bows are sandwich structures of aluminium honeycomb with fibreglass and epoxy laminate face piles. Ply thickness is tailored to provide maximum energy absorption and impact attenuation for 2.5 G ground contact without structural failure. The bow shape will bend and bounce back far better than traditional landing gear legs. The landing skids are pre-bent aluminium tubes with steel skid shoes. The fuselage and landing gear weigh approximately 50 pounds, yet provide superior performance and safety.

TAILBOOM
The tail rotor gearbox is a spiral bevel type and is driven by a one piece shaft (again no belts!) supported by hangar bearings inside the tailboom. The tailboom is made of aluminium. This small sacrifice in weight consideration was overridden by cost savings. The horizontal stabiliser is composite as is the vertical ring tail surrounding the tail rotors. The vertical ring tail protects the tail blades in the event of a tail strike upon landing.

DESIGN AND FABRICATION FEATURES FOR THE ULTRASPORT 331/496 FAMILY OF HELICOPTERS

MAIN ROTOR BLADES
All composite blade construction. Cambered airfoil section, modified inboard for improved aerodynamic and structural efficiency. 8° linear twist from root to tip for improved hover performance. Tungsten leading-edge weights in outboard 50% of radius for aeromechanical stability. Tungsten tip weights for high inertia in auto-rotation. T/K is higher than any helicopter currently being manufactured. Graphite, fiberglass, epoxy spar is precured in mold, nomex honeycomb trailing edge core structure is bonded to spar along with trailing edge reinforcement structure, assemby is wrapped with external fiberglass skin, and entire blade assembly is placed in heated aluminum mold for final cure process. After curing, blade is trimmed, polyurethane erosion strip is applied, and blade is finished and balanced. Rotor efficiency is very high with 14 lbs of lift for each horse power due to low disc loading.

MAIN ROTOR CONTROLS
Direct pilot control to swashplate through floor mounted cyclic stick. Control sensitivity may be tuned to pilot capabilities by utilizing interchangeable walking beams having different input/output ratios. Conventional collective/throttle lever includes owner-adjustable collective/throttle correlation feature. In-flight adjustable collective and throttle friction available.

MAIN ROTOR DRIVE AND TRANSMISSION
Engine power input through centrifugal clutch for ease of starting. Overrunning Sprag clutch in C.F. clutch disengages automatically for auto-rotation. Tail rotor is driven by main rotor during auto-rotation for precise heading control. Transmission designed for continuous operation at 6500 RPM input speed 2-Stage, planetary gear train with 12:1 speed reduction. Oil cooled and wet lubricated with internal sump and pump. All gears custom designed and fabricated to American Gear Manufacture Association Class 11 standards. Transmission power-to-weight ratio competitive with modern helicopter practice ( ~ 4:1 ).

TAIL ROTOR BLADES
Construction similar to main rotor blade, except trailing edge core is Rohacell structural foam. Rubber snubbers in inboard yoke assembly absorb/damp lead-lag blade motions. Thin low drag airfoil and parabolic swept tip contribute to very low tail rotor noise signature.

TAIL ROTOR DRIVE SYSTEM AND HUB
Tail rotor driven by main rotor transmission through 1-inch aluminum driveshaft supported by four hangar bearings inside tailboom. Tail rotor driveshaft connected to main and tail rotor transmission with small Thomas couplings that provide both end-float and angular misalignment capabilities. Tail rotor driven at engine speed through 90° gearbox mounted in end of tailboom. Gearbox is grease-lubricated and is cooled by external airflow - normal maximum operating temperature is 125° F. Tail rotor controlled by conventional pedals through quick-disconnect cable installation.

FUSELAGE AND TAILBOOM
Basic structure is robust pilot's seat which forms a strong torque box to which everything else is attached. Seat is assembled from sandwich panels made from epoxy resin, graphite fabric and nomex honeycomb core with local densification for mechanical attachments. The engine and drive train are bolted directly to the back face of the seat assembly. Forward fuselage is essentially a non-structural pilot fairing made from 2 layers of grahite fabric and epoxy resin.

One-piece formed windshield is free formed to provide maximum clarity. Landing gear bows are sandwich structures made from aluminum honeycomb with fiberglass/epoxy laminate face plies. Ply thickness is tailored to provide maximum energy absorption and impact attenuation for 2.5g ground contact without structural failure. Landing skids are aluminum tubes with steel skid shoes at each attachment point.

Please note: Ultrasport may change Specifications for the Ultrasport 331 and Ultrasport 496 helicopters at any time. To obtain the latest update in specifications contact: Helisport Australia on the 'Contact Us' page.