Robinson R22

USD $120,000.00

The R22 is a light, two-place, single reciprocating-engined helicopter with a semi-rigid two-bladed main rotor and a two-bladed tail rotor. The main rotor has a teetering hinge and two coning hinges. The tail rotor has only a teetering hinge.

The normal production variant has skid landing gear. The Mariner version — which is no longer manufactured — provided floats. Wheeled gear is not available.

The basic structure is welded chromoly steel tubing. The forward fuselage is made of fiberglass and aluminum with a Plexiglas canopy. The tailcone and vertical and horizontal stabilizers are aluminum. It has an enclosed cabin with side-by-side seating for a pilot and passenger. The doors may be removed for flight, as is often done for photographic flights, interior cooling in high temperatures, or a 10.4 lb weight saving.

The first version was produced as the R22, followed by the R22 HP, R22 Alpha, R22 Beta, and R22 Beta II. Superficially, the aircraft appear similar. The R22 HP was fitted with a 160 bhp Lycoming O-320-B2C engine, an increase of 10 bhp (7.5 kW) over the original R22. The steel tube frame on the R22 Alpha was modified by extending the aft landing gear mounting points, giving the ship a slightly nose-down attitude on the ground and better matching of the skids to the ground in a low altitude hover with two people on board. The R22 Beta added an engine speed governor (optional), rotor brake, and auxiliary fuel tank (optional). The battery was moved from below the instrument cluster to the engine compartment for better balance. The R22 has been offered as an instrument trainer version, with optional fixed floats as the R22 Mariner, and other special configurations for police work, electronic news gathering, and so on. The R22 Beta II received a larger Lycoming O-360 engine de-rated for sea level operation. It allows greater altitudes for hovering in and out of ground effect (HIGE/HOGE). The R22 Beta II also made the engine speed governor standard and included a carburetor heat assist which correlates adding carburetor heat with decrease in collective control. Only the basic skid style is currently being sold.

Controls

 
The R22's cockpit, showing its unique "T-Bar" control

Instead of floor-mounted cyclic sticks between the pilot's knees, the R22 uses a unique teetering "T-Bar" control connected to a stick that emerges from the console between the seats. This makes it easier for occupants to enter and exit the cabin and reduces chances for injury in the event of a hard landing. The teetering bar has a hand grip on both sides that hangs down between the pilots' legs. Thus, if teetered to the right, the right side pilot would be flying and the left grip would be about 12 inches above the left pilot's lap. R22 flight instructors quickly learn how to fly with their hand in the air. The left part of the bar, left collective control, and left tail rotor pedals can be removed if the left seat occupant is not certified to fly the R22 or if the space is needed for technical or observer duties. A floor-mounted foot-activated push-to-talk switch facilitates intercom communications for the left seat occupant, although some later models may be equipped with a voice activated intercom system.

The helicopter rotor system consists of a two-bladed main rotor and two-bladed anti-torque rotor on the tail, each equipped with a teetering hinge. The main rotor is also equipped with two coning hinges. Collective and cyclic pitch inputs to the main rotor are transmitted through pushrods and a conventional swashplate mechanism. Control inputs to the pre-coned tail rotor are transmitted through a single pushrod inside the aluminum tail cone.

To ease the pilot's workload, a mechanical throttle correlator adjusts the throttle as the collective pitch control is raised or lowered. The pilot needs to make only small adjustments by twisting the throttle grip on the collective throughout the flight regime. Later models are also equipped with an electronic governor which works to maintain RPM within normal operating limits (between 97% and 104% RPM); the governor is active only when the engine is running above 80% RPM, and is most effective in normal flight conditions. The governor can be switched on or off with a toggle switch located at the end of the pilot's collective pitch control. When the governor is not engaged, a yellow caution light glows on the instrument panel.[7]

Powerplant

 
Lycoming O-320 mounted in a Robinson R22 Beta
 
The R22 is a simple and tight design

The R22 uses a horizontally mounted Lycoming O-320 (O-360-J2A on the Beta II), four-cylinder, air-cooled, normally aspirated, carburetor-equipped piston engine. It is fueled with 100LL grade aviation gasoline. Cooling is provided through a direct drive squirrel-cage cooling fan. At sea level it is derated, or operated at less than maximum power, which has been attributed to the company wishing for the power unit to maintain the same performance at sea level as it does at altitude. As the air becomes thinner with increasing altitude, maximum available horsepower decreases, reaching a point where the throttle can be completely open and rotor RPM is controlled by collective position. By derating the engine at sea level, the R22 achieves acceptable high-altitude performance without use of supercharging or turbocharging, thus saving the weight, cost, complexity, unreliability, and shortened engine life of a forced induction system.

A carburetor is used to provide the air-fuel mixture. Carbureted engines are susceptible to carburetor icing, a condition most likely to occur in conditions of a low 11 °C (20 °F) difference between the outside air temperature and dew point (the "dew point spread"), as well as visible signs of moisture in the atmosphere. Icing can lead to loss of engine power and, if not corrected, total shutdown of the engine. A carburetor heat control is used to supply heated air to the carburetor; this can prevent or cure icing, but also causes a reduction in engine power output because hot air is less dense, enriching the fuel-air mixture. The carburetor heat control is a simple plunger-type control mounted on the center console near the collective pitch control lever. Pulling the control up slides a gate valve near the carburetor that admits warm air from a scoop on the exhaust system. The R22 employs a carburetor air temperature gauge, marked to indicate temperatures conducive to icing. The Beta II version of the R22 also includes a "carburetor heat assist" which automatically applies carburetor heat when the collective is lowered below a certain point. When icing conditions are present, carburetor heat is required to prevent icing around the butterfly valve from the pressure drop at that point. As the carburetor air temperature (CAT) indicator does not read correctly below 18 inches (46 cm) of intake manifold air pressure, icing conditions require applying full carburetor heat below 18 inches (46 cm) of manifold pressure. A placard indicating this requirement is located on the CAT indicator and in the Pilot's Operating Handbook (POH).

Power is transmitted from the engine to the drive system through drive belts. Originally, the R22 used four separate v-belts running on multi-groove sheaves. This system proved problematic, as individual belts would sometimes roll over in their groove and fail. As a temporary measure, in 1982, R22 operators received a kit from Robinson that was installed in the cockpit and on the belt tension actuator, isolating the tensioning circuits and locking the clutch/drive system at take-off tension. The problem was ultimately solved by replacing the four individual v-belts with two dual v-belts. The upper, driven sheave is mounted on the main/tail rotor drive shaft incorporating flexible couplings, and is raised and lowered relative to the engine-mounted, driving sheave by means of a belt tension actuator. During shutdown, the actuator is used to lower the upper sheave to loosen the drive belts. For startup, the engine is started with the belts loose, allowing the engine to run without spinning the rotor system. Immediately after engine start, the clutch switch located in the cockpit is closed by the pilot, powering the actuator to slowly raise the upper sheave to flight position, which tightens the belts. The actuator is thereafter controlled by pressure-sensing column springs, automatically maintaining proper belt tension during flight as the belts wear and stretch. The shaft on which the upper sheave is mounted drives both the main and tail rotors; the main gear box delivers power to the main rotor shaft through a set of splash-lubricated spiral bevel gears.

A one-way sprag clutch is built into the center of the upper sheave to allow the rotor system to continue to rotate in the event of engine failure, allowing the R22 to enter autorotation and land in a controlled manner. Because the main rotor has very little mass and inertia, autorotation in an R22 requires careful and proper execution to assure a successful outcome. Much time is spent in training practicing various types of autorotation. Target speed in an autorotation is 65 kn (120 km/h) and the glide ratio is approximately 4:1 in maximum-glide configuration.

 

Product Guide (RotorcraftPro_2016MediaPlanner_0909_Final.pdf, 2,012 Kb) [Download]

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