Robinson R22

The Robinson R22 is a two-bladed, single-engine light utility helicopter manufactured by Robinson Helicopter. The two-seat R22 was designed in 1973 by Frank Robinson and has been in production since 1979.

The R22 has a suggested retail price of $270,000,^[1] and is valued from $40,000 on the second hand market.^[2]

Development

Due to relatively low acquisition and operating costs, the R22 has been popular as a primary rotorcraft trainer around the world and as a livestock management tool on large ranches in North America and cattle stations in Australia. The R22 has a very low inertia rotor system and the control inputs are operated directly by push rods with no hydraulic assistance. Thus, the flight controls are very sensitive and require a light touch to avoid over correcting. A student that masters an R22 generally does not have a problem transitioning to a heavier helicopter. Due to the issues relating to a low inertia rotor-system and a teetering main rotor, operation by any pilot in the United States of the Robinson R22 or Robinson R44 requires a special endorsement by a certified flight instructor.^[3] Tip weights were added to increase rotor inertia,^[4] but the small rotor limits weight.^[5]

Maverick and Renegade UAVs

The R22 is the basis for Boeing's Maverick military unmanned aerial vehicle helicopter, and its Renegade version. In 1999, Frontier Systems developed a remotely piloted R22, the Maverick. This aircraft, along with the company, was later acquired by Boeing Phantom Works. In 2003 the U.S. Navy purchased four aircraft, equipped with Wescam EO/IR (Electro-Optical/Infrared) systems.^[6]

Boeing then modified one of the Mavericks further, calling it the Renegade, under contract with DARPA as a research testbed to develop software for its A160 Hummingbird.^[6] The software system, known as the Software Enabled Control (SEC) program, was developed by Boeing and teams from the University of California Berkeley, Georgia Institute of Technology and Massachusetts Institute of Technology, and was first flown on May 26, 2005. During the flight, the SEC assumed control of the aircraft to "execute autonomous maneuvering algorithms".^[7] The software allows the aircraft to autonomously select "optimal routes through a field of pop-up and already-known threats; flying low-level, terrain-hugging profiles to avoid detection; and determining safe landing zones by using vision-based algorithms to process landing site imagery and terrain height information."^[8]

Design

Robinson R22 hovering

The R-22 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 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, 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, and are often done so 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 0-320-B2C engine, an increase of 10 bhp (7.5 kW) over the original R22. The landing skid assembly on the R22 Alpha was modified by extending the rear struts, giving it a slightly nose-down attitude on the ground and better matching its attitude 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. It 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 added a Lycoming 0-360 engine, remade of lightweight materials and derated for sealevel 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 "carb heat assist" which correlates adding carb heat with decrease in collective control. Only the basic skid style is currently being sold. The R44 is available as the Clipper with floats, and as police and electronic news configurations.

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 teeter 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 certificated to fly the R22 or 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 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 only needs to make 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 only active 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.^[9]

Powerplant

Lycoming O-320 mounted in a Robinson R-22 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 capable of producing more power than the transmission and rotor system can safely handle, and to ensure maximum engine and transmission life the O-360 must be derated, or operated at less than maximum power. As the air becomes thinner with increasing altitude, maximum available horse power 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, 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 low (11°C) 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 from the exhaust muffler heat exchanger; this can prevent or cure icing, but also causes a reduction in engine power output because hot air is less dense, enrichening the fuel-air misture. The "carb heat" control is a simple plunger-type control mounted on the center console near the cyclic; pulling the control up slides a gate near the carburetor that admits warm air from a shroud surrounding the muffler. 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" of intake manifold air pressure, icing conditions require applying full carburetor heat below 18" 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 rotor system through drive belts. Originally, the R22 used four separate v-belts. This system proved problematic, as belt length variations due to manufacturing tolerances caused some belts to overstress and break. In 1982, R22 operators received a kit from Robinson that was installed in the cockpit and clutch worm-gear motor that isolated the tensioning circuits and locked the clutch/drive system at take-off tension, but this was only a stop-gap measure. The problem was solved by replacing the four individual belts with two dual-v belts, running on matching multi-groove sheaves. The upper driven sheave is mounted on the tail rotor drive shaft next to a flexible coupling and is raised and lowered relative to the engine-mounted driving sheave by means of a small electric gear motor. During shutdown, the gear motor is used to lower the top 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 gear motor to slowly move the top sheave up to flight position which tightens the belts. The gear motor is thereafter controlled by a pressure-sensing switch, automatically maintaining proper belt tension during flight as the belts warm up and stretch. The tail rotor drive shaft is also driven by the main transmission; the semi-conical gear box delivers power to the main rotor shaft through a pair of splash-lubricated spiral bevel gears.

The top sheave has a Sprague clutch built into the center of the sheave to allow the rotor system to continue to rotate in the event the engine stops. This allows the R22 to enter autorotation and land in a controlled manner after loss of engine power. Because the main rotor has very little mass and resulting inertia, autorotations in an R22 are exciting at best and require 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 angle is approximately 4:1 in max glide configuration.

Trailering

Robinson R22 on trailer. Trailer is 8 x 30-feet with a gross weight of 3500-lbs

The two-bladed rotor and the small size of the R22 make it possible to trailer the helicopter without blade folding or dismantling tasks. Trailering the R22 requires securing the tail boom and rotor blades to the trailer ^{[citation needed]}, which must be torsionally rigid to prevent motion and stresses being applied to the helicopter during transportation. It is possible to take off from and land directly onto the trailer.

Variants

R22

Initial production version powered by a Lycoming O-320-A2B or A2C piston engine.

R22 HP

Higher-powered version, powered by a 160-bhp Lycoming 0-320-B2C piston engine.

R22 Alpha

Improved version certified in 1983 powered by a Lycoming 0-320-B2C piston engine.

R22 Beta

Fitted with a more powerful engine, powered by a Lycoming 0-320-B2C piston engine.

R22 Beta II

Fitted with a more powerful engine, powered by a Lycoming O-360-J2A piston engine.

R22 Beta II Police

Police patrol version, equipped with searchlight and loudspeaker.

R22 Mariner

Designed for off-shore work, fitted with floats and wheels, powered by a Lycoming 0-320-B2C Beta piston engine. Limited to daylight operations when fitted with floats.

R22 Mariner II

Designed for off-shore work, fitted with floats and wheels, powered by a Lycoming O-360-J2A Beta II piston engine. Limited to daylight operations when fitted with floats.

R22 Police

Police version.

R22 IFR

Designed for IFR training with a larger 10-hole panel to accommodate additional instruments. Not IFR certified so training must be done with a safety pilot in VFR conditions.

Maverick UAV

Unmanned military version marketed by Boeing

Renegade UAV

Unmanned R&D version built for DARPA

Operators

The R-22 is operated by many private individuals, companies and flying clubs. In Australia, where there are 489 R22s registered as of mid-2011, a survey found that 62% of the fleet's flying time was in mustering operations, while 13% of hours were spent in training pilots. Many broadcasters used the R-22 until the mid-1990s when the financial landscape of radio broadcasting in the U.S. changed due to deregulation of the industry.^[10]

Military

 Dominican Republic

• Dominican Republic Army ^[11][12]

 Philippines

• Philippine Navy ^[13]

Accidents and incidents

Since the R22 received FAA certification in March 1979, Robinson has delivered 4620 R22 helicopters. The R22 had 182 fatal accidents between March 1979 and June 2010 from a total of 1230 incidents. In late 1981, the R22 had its type certificate temporarily revoked by the Federal Aviation Administration due to delamination of a main rotor blade. The cause of the delamination was determined to be contamination of one of the bonded parts during a priming operation performed at an outside vendor. In response, Robinson Helicopter Company instituted stringent quality procedures and requirements, and replaced all main rotor blades on the fleet of 33 helicopters in service at the time.^[14]

In the early 1980s, the R22 experienced a number of student-pilot related accidents due the R22’s use as a primary flight trainer. Believing the number of accidents was the result of insufficient training and lax standards, Robinson established the Robinson Pilot Safety Course in 1982 to educate Certified Flight Instructors transitioning from larger helicopters to the new, smaller R22.^[15] After the introduction of the Robinson Pilot Safety Course, the rate of fatal R22 accidents declined from 3.7 per 100,000 flight hours in 1983 to 0.97 per 100,000 flight hours for the 12 months preceding July 1995.^[16] Robinson’s statistics show the rate of fatal R22 accidents per 100,000 flight hours fell from 6.0 in 1982 to 0.7 in 1997.^[17] To date more than 17,000 students have gone through the course.^[18]

Specifications (R22)

Data from Robinson R22 Pilot's Operating Handbook.^[9] Current versions of the R22 vary slightly.

General characteristics

• Crew: 1
• Length: 28 ft 8 in (8.74 m)
• Rotor diameter: 25 ft 2 in (7.67 m)
• Height: 8 ft 11 in (2.72 m)
• Disc area: 497 ft² (46.2 m²)
• Empty weight: 796 lb (389 kg)
• Loaded weight: 920 lb (417 kg)
• Max. takeoff weight: 1,370 lb (635 kg)
• Powerplant: 1 × Lycoming O-320-A2B or -A2C flat 4 piston engine, 124 hp (93 kW)
• Main tank total capacity: 19.8 US gallons (75 liters)
• Main tank usable capacity: 19.2 US gallons (73 liters)
• Optional aux tank total capacity: 10.9 US gallons (41 liters)
• Optional aux tank usable capacity: 10.5 US gallons (40 liters)

Performance

• Never exceed speed: 117 mph, 189 km/h, 102 kts
• Cruise speed: 110 mph, 177 km/h, 96 kts
• Range: 240 mi (386 km)
• Service ceiling: 14,000 ft (4,267 m)
• Rate of climb: 1,200 ft/min (6.1 m/s)
• Disc loading: 2.61 lb/ft² (13.7 kg/m²)
• Power/mass: 0.095 hp/lb (0.147 kW/kg)
  
• Endurance: approx. 2 hours, with 30-minute reserve

See also

Related development

• Robinson R66
• Robinson R44

Aircraft of comparable role, configuration and era

• Brantly B-2
• Schweizer 300C
• Guimbal Cabri G2

References

External links

Wikimedia Commons has media related to Robinson R22.

• Robinson Helicopter Company web site
• Robinson Helicopter Owners Group
• Robinson R22 Beta II Performance, Specification and Photos
• Frank Robinson and development of the R22
• EASA Type Certificate Data Sheet - R22/R22 ALPHA/R22 BETA/R22 MARINER