480B Technical Specifications
1. Design History The Enstrom 480B is a single engine, turbine powered helicopter derived from the Enstrom F28 family of helicopters. The original piston powered F28 received FAA type certificate number H1CE in 1963, and all subsequent Enstrom helicopters were developed as variants to the original type certificate. The F28A began rate production in 1965. In 1976 the F28A was upgraded to the F28C, and a restyled variant was introduced called the 280C. Subsequent upgrades led to the current models F28F and 280FX, which were introduced in 1981 and 1985 respectively. Enstrom began turbine aircraft development in 1985 with the 280FX-T. This prototype aircraft was essentially a 280FX with an Allison turbine engine installed. The helicopter was developed for an upcoming tender for a light turbine training helicopter for the US Army. Ultimately the 280FX-T was deemed not suitable for the competition, and a larger aircraft was developed using many of the same components. This aircraft, designated the TH-28, was certified in 1991, and a handful were produced and sold. The model 480 helicopter was certified in 1993 as a civilian variant of the TH-28. Rate production of the 480 continued until 2001, when the upgraded 480B model was introduced. Certified to the latest FAR 27 standards, upgrades to the 480B included a higher gross weight, more available power from the engine, and tuned mass dampers on the controls. 2. Overview The Enstrom 480B helicopter is a single-engine, turbine-powered helicopter certified for day and night VFR flight, and equipped for IFR flight. The 480B was developed for light commercial, municipal, training, personal, and military uses. It can seat up to 5 people using a flexible cabin design, and has a gross weight of 3000 lbs. The 480B carries 90 gallons of fuel and can stay in the air for over 4 hours at survey speeds. The large comfortable cabin offers the crew exceptional visibility and the large, slow turning, rotor system makes it a relatively quiet helicopter. The pilot and observer have unrestricted visibility from the cabin and the helicopter can be fitted with all of the most advanced surveillance and detection equipment.
The Enstrom 480B features a three-bladed, fully articulated main rotor system which has over 4,000,000 flight hours and has never had a catastrophic failure or thrown a blade. The tail rotor is two bladed and completely unblocked for exceptional effectiveness. Due to the high inertia rotor design, the helicopter possesses exceptional auto-rotational capabilities. In the event of a mishap, the 480B is extremely crashworthy. The basic landing gear and airframe feature an integrated energy absorbing system. In addition to being a versatile and crashworthy helicopter, the 480 is designed to be procured and operated for minimum costs. The basic modular design is simple and inexpensive to manufacture. The helicopter does not require hydraulic boost or a stability augmentation system. The entire control system consists of mechanical linkages. The avionics package is designed for easy installation and accessibility and the 480 is configured with five hinged doors and five removable panels for maintenance accessibility. The limited number of fatigue critical parts, the long overhaul intervals, and the low maintenance hour/flight hour ratio resulting from high reliability and easy maintenance combine to yield low operating and support costs.
3. Description 3.1. Primary Structure The basic helicopter structure consists of a steel tubular pylon assembly to which the cabin, fuel cells, transmission, engine, landing gear and tail cone are attached. The pylon assembly is a jig fabricated 4130 welded steel tube structure which serves as the backbone of the aircraft. The composite cabin assembly is attached to the front of the pylon structure, and the aluminum monocoque tailcone is attached to the aft of the pylon structure. The engine is installed in the center of the pylon, the main transmission on the top, and the landing gear on the bottom. The pylon tubing is painted with a light green epoxy primer in order to protect the steel against corrosion. The tailcone is a riveted, semi-monocoque aluminum assembly attached to the pylon. The fixed aluminum stabilizers have composite fins that also house the navigation and strobe lights. The tail rotor gearbox and the tail rotor are mounted on a stinger tube that is attached to the aft end of the tail cone assembly, and there is a light-weight tail-rotor guard that protects the tail-rotor assembly from inadvertent minor ground contact, and helps protect personnel. A tuned-mass damper attached to the rear of the tailcone reduces vibration in the helicopter significantly.
The cabin has two overhead windows, windscreens, ½ front windows, chin windows, door windows, and ½ rear windows. The windscreens are free blown acrylic Plexiglas for perfect optical clarity. All of the glass is blue tint, except the overhead windows which are smoked gray. The 480B has 22 cubic foot fully enclosed external cargo hold, capable of carrying 150 pounds, which allows ample room for the transport of equipment, personal items, and travel gear. The cargo door is located on the left side of the helicopter, and the hold stretches from the last bulkhead of the pylon area to the second bulkhead of the tailcone. The Enstrom 480B is configured with 5 hinged doors and 5 quickly removable panels for maintenance accessibility of the engine and aircraft systems in the pylon section. In addition, large panels are removable from the bottom of the cabin assembly for maintenance access to the avionics, wiring, and flight controls.
The Enstrom 480B comes standard with high skid landing gear which consists of aluminum skid tubes and nitrogen air-oleo struts to cushion ground contact. There are hardened steel wear strips attached to the bottom of the skid tubes to prevent wear. The landing gear is braced fore and aft, as well as side to side, in order to take the abuse of repeated run-on landings auto-rotations without failure. The landing gear was also designed to accept negative loads, such as a person riding outside the aircraft standing on the skid. Optional pop-out floats and snow shoes can be attached to the aluminum skids. The cabin consists of a composite shell with a built up aluminum keel structure and a nomex honeycomb panel floor. There is 114 cubic feet of enclosed passenger space, and no divider bulkhead between the crew and passenger sections of the cabin. The flight controls, wiring, and electronic equipment is installed underneath the floor. The keel structure is energy absorbing, and also serves to mount the forward landing gear cross tube. The floor and back wall structure are nomex core honey-comb structure for light weight, noise isolation, rigidity and strength. The nomex core also provides fire protection between the crew area and the engine compartment. The front seats are attached to the floor via trackable rails. The rear seats are attached to the back wall via bonded inserts. The 480B uses a single large door on each side of the cabin which allows loading from either side, and has a single door on the left side of the fuselage to access the separate baggage compartment. Both the cabin doors and the engine cowl doors are secured with pneumatic door openers for ease of use. The aircraft is certified for flight with both cabin doors removed. The doors are composite construction, with two forward hinges, and an internal 4 point latching mechanism. Adjustable vent windows are included as standard equipment, and a larger, downward sliding window can be installed for camera use.
3.2 Passenger Cabin and Cockpit The current factory standard seating consists of one pilot seat on the left side of the cockpit, three-abreast seating in the rear bench seat, and one dual-purpose passenger or co-pilot seat in the right front. The pilot and co-pilot seats are tracked, adjustable, conventional aircraft seats, and the passenger seats are mounted to the back wall of the cabin. The Enstrom 480B uses a ram air fresh air ventilation system and an optional overhead circulation fan for crew comfort. There are also sliding vent windows in the cabin doors, and pop out vents in the side windows for additional fresh air. An optional two or three evaporator air conditioning system can be installed, with the two evaporators mounted in the nose of the aircraft behind the instrument panel, and the third mounted on the back wall. The compressor is driven via a belt and electric clutch off of the engine, and the condenser is mounted in the tailcone. The heat and defrost are supplied by engine bleed air and the vents are positioned for maximum efficiency in keeping the windscreen clear and the crew comfortable. For environments that do not require a heater a demisting fan is installed to keep the windscreen clear. The 480B cabin is extremely quiet as the engine and gearbox assemblies are isolated from the cabin structure and separated by the nomex honeycomb structure.
The instrument panel assembly consists of an upper instrument section capable of holding a complete set of flight instruments, systems instruments, and multiple MFD s. This panel is customizable to the customer s specifications. The upper panel is offset to the left for better viewing by the pilot in command, and to provide more room and visibility for the copilot/passenger/observer. The lower console is designed to hold the radios and circuit breakers between the pilot and co-pilot at an angle to optimize ease of operation by the crew. The instruments are for the most part internally lighted while the radio panel is back-lighted. A removable glare shield surrounds the upper panel. The lower console is attached to the keel structure, while the upper section is shock mounted to the lower console to reduce vibration. 3.3 Flight Controls: The control system on the 480B is entirely mechanical. There are no hydraulics needed, and a powerful electro-spring trim system is used. Tuned-mass dampers installed on the cyclic bellcranks eliminate vibration in the cyclic. The controls are extremely smooth due to the use of ball bearings and heavy duty control rods.
The collective control system is mounted in ball bearings, for light and smooth operation. The collective forces are balanced out by an adjustable spring cartridge. The design of the rotor system and spring cartridge is such that the collective will remain in whatever position it is left in, with very little tendency to drift up or down. An additional pilot controlled friction system can be used to adjust the force necessary to operate the collective. The tail rotor is controlled via cables attached to adjustable pedals. The fly weights on the tail rotor blade retention plates unload the tail rotor feathering forces in flight. The weights are adjusted for pedals neutral flight at 55 psi (approx. 75%) of torque. This allows for cruise flight without the need to carry any pedal input, as well as a controlled descent and landing in the event of a tail rotor cable failure. The tail rotor assembly is located on a stinger behind the tailcone and stabilizers. This allows it to run in free air, giving it excellent authority. The 480B has demonstrated the ability to fly in winds up to 35 knots in any direction without loss of control. There have been no recorded incidents of a 480 series aircraft suffering from LTE (Loss of Tailrotor Effectiveness) that the factory is aware of.
Unique to Enstrom, the swashplate is installed on the bottom of the main transmission, and the control rods are installed inside of the main rotor shaft. This design protects the control system from the environment and foreign object damage. Walking beams on the rotor head transfer motion from the control rods down to the blade grips. 3.4 Rotor System The main rotor system on the 480B is a three bladed, high inertia, fully articulated rotor system. The main rotor hub assembly is composed of two opposing forged aluminum hub plates separated by an aluminum cylindrical spacer. Through bolts hold these items together along with steel spline adapters. Three steel universal blocks are mounted on roller bearing units that permit flapping and lead-lag motions. Laminated phenolic pads are used to limit blade travel in both the lead-lag and flapping axes. A thrust nut on the bottom of each universal block transfers vertical blade forces to both hub plates through the universal block. The rotor blades are secured to each universal block on the hub through a forged aluminum grip which is in turn secured to a steel spindle assembly through a tension-torsion strap (T-T strap). Adjustable pitch change links are used to individually tune the blade track. A single large hub retention nut secures the hub plates to the mast. The lead-lag dampers are air-oleo units with dual access reservoirs for easily bleeding the silicone damper fluid. Additional oil reservoirs are installed for the flapping bearings.
The main rotor blades are of hollow construction consisting of an extruded leading edge spar, with a 7 degree twist, to which is bonded upper and lower aluminum skins. The blade root is composed of a bonded doubler assembly. A single retention pin connects the blade root to the grip and a non-adjustable drag brace connects the trailing edge of the blade to the grip. A cap is bonded to the tip of each blade in which there are provisions for spanwise and cordwise balance weights. Two tracking tabs are riveted to the trailing edge of each blade. Each main rotor blade weighs 55 lbs, and the weight of the main rotor system is over 300 lbs. The minimum speed of the system is 334 rpm and the maximum 385 rpm. The optimum speed is 372 rpm. The main rotor blades have a fully symmetrical airfoil which gives it excellent autorotation and rpm recovery characteristics. The tail rotor is a two-bladed, wide chord, teetering, delta hinged rotor assembly. The blades are made utilizing the same construction methods as the main rotor blades. 3.5 Power Plant: The Enstrom 480B uses the Rolls Royce 250 series, C-20-W which is rated at 420 SHP. The engine is derated to 305 SHP for 5 minutes, and 277SHP continuously. Rolls-Royce Model 250-C20 Turboshaft Engine
The oil system uses a 4 quart oil tank, and the oil cooler is mounted just forward of the tail cone on the right side of the aircraft. Engine Oil System Schematic Diagram The Enstrom 480B has a closed loop fire detection system with a fire-warning indicator prominently displayed at the top of the instrument panel. Additionally, the turbine section of the engine is protected from the rest of the engine bay by a fire blanket. The engine uses bleed air for cabin heat, defrost, scavenge air and engine deicing. The controls are mounted on the aft end of the lower instrument console where they can easily reached by the crew. The engine is equipped with 150 amp starter-generator and an 18 amp/hour lead-acid battery allowing non-assisted starts The 480B has an engine wash system installed, allowing simple and easy compressor washes. The engine is fitted with a pilot adjustable governor, as well as a droop compensator controlled by the collective. When the collective is raised, such as during a power recovery to a practice autorotation, the droop compensator anticipates the power requirement and increases throttle ahead of the governor, helping to avoid the pilot getting behind the power curve. The engine exhaust exits out the bottom of the helicopter. An eductor mixes the hot exhaust with ambient air to cool it. Rigorous testing has shown that when landed in tall grass or brush, the exhaust and eductor remain cool enough not to ignite a fire.
The engine intake is above the fuselage, underneath main rotor head. Centri-sep swirl type particle separators are used to filter out the intake air. Bleed air can be used to purge the particle separators, and for anti-ice. 3.6 Fuel System: The fuel tanks of the Enstrom 480 series aircraft are mounted over top of the engine compartment eliminating the requirement for fuel boost pumps. The fuel system is gravity fed to the engine fuel pump.
The fuel system consists of two interconnected fuel tanks holding a maximum of 90 gallons ( 603 lbs ), with one hinged fuel cap in the left tank. The crossover line allows fueling of both tanks from one point on the aircraft. Each tank consists of a foam-filled bladder housed in a composite fuel cell. The 480B uses a capacitance fuel sender to measure fuel quantity, which is displayed, in pounds, on a gauge in the instrument panel. An additional float-type sender is used to indicate when a minimum quantity of fuel is left. This is displayed via a Low Fuel warning light on the instrument panel. A small tube is inserted into the foam inside the left bladder underneath the filler to allow the safe insertion of a dipstick to physically measure the fuel quantity when on the ground. In addition to the engine fuel filter, an auxiliary airframe mounted filter system is available. A static grounding port is mounted near the fuel filler port. 3.7 Transmission Systems: The main rotor gear box is a simple ring-and-pinion style gearbox, splash lubricated and using an electric pump to circulate the oil through an oil cooler and oil filter. The housing is equipped with a removable chip detector. The overrunning clutch system is mounted in the engine power shaft assembly. The power is transmitted from the engine to the main rotor gearbox via a single multi-rib belt. The belt is tensioned via a jackstrut assembly, and requires little maintenance. There has never been a recorded in-flight belt failure in an Enstrom helicopter. The tail rotor drive shaft system is mounted on five grease lubricated hanger bearings, and has no angle gearboxes. The tail rotor drive shaft is driven directly off the upper pulley input to the main rotor gear box.
The one-to-one right angle tail rotor gearbox is non-vented and splash lubricated. It is equipped with a sight glass and a removable chip detector. 4. Dimensions and Specifications 4.1 Dimensions:
4.2 Specifications: WEIGHTS Gross Weight 3000 lbs. 1361 kg Empty Weight (std. equip.) 1820 lbs. 826 kg Useful Load 1180 lbs. 535 kg FUEL SYSTEM 2 Interconnected Tanks 90 gal 341 liters POWER PLANT Rolls Royce 250-C20W Turbine Power Available 420 shp 313 kw Maximum (5 Min.) 305 shp 227 kw Continuous 277 shp 206 kw Particle Separator 93% Eff. 93% Eff. 4.3 Performance (Standard Day): Mission Weights 2500 lbs (1134 kg) 2800 lbs (1270 kg) 3000 lbs (1361 kg) Never Exceed Speed 125 kts (231 kph) 125 kts (231 kph) 124 kts (230 kph) Maximum Cruise Speed (TAS @ 3000 ft) 115 kts (213 kph) 113 kts (209 kph) 109 kts (202 kph) Service Ceiling 13,000 ft (3962 m) 13,000 ft (3962 m) 10,000 ft (3048 m) Max. Rate of Climb @ S/L 1600 fpm (8.1 m/s) 1475 fpm (7.5 m/s) 1375 fpm (7.0 m/s) Hover In Ground Effect (IGE) 15,600 ft (4755 m) 13,000 ft (3962 m) 12,300 ft (3749 m) Hover Out of Ground Effect (OGE) 14,000 ft (4267 m) 10,600 ft (3231 m) 5400 ft (1646 m) Maximum Range @ 3000 ft 370 nm (685 km) 360 nm (667 km) 355 nm (657 km) Maximum Endurance @ 3000 ft. 4.7 hrs 4.6 hrs 4.5 hrs
5. Performance Charts 5.1 Hover Performance
5.2 Endurance 5.3 Cruise Performance (sea level)