AK-1  Mk3 Performance

In terms of generalized parameters (load-to-swept-area ratio G max / F versus Load-to-power ratio G max / N max relationship) the AK1-3 helicopter corresponds to the worlds best helicopters in this class.

The graph above shows the R22 Beta with the O320 160 hp Lycoming engine and has the Schweitzer at its maximum gross weight of 932 kg (2050 pounds)

In the table below comparisons are made with the R22 Beta II with the 180 hp engine and the Schweitzer at gross weight of only 773 kg (1,700 pounds = 2 persons)

Note: Robinson de-rates the 180 hp O360 Lycoming engine used to 131 hp, thus allowing it to maintain the 131 hp to higher altitudes.

1. Hover and vertical climb performance.

 

The employment of a rotor solidity ratio =0.0475, symmetrical variable-section blades NACA-63012-63015 and nonlinear twist of –9 has enabled to achieve the maximum thrust T-max at the lift off equal to 800kgf (Fig 2) with the engine’s take off power of 165Hp. This has also made possible to implement good characteristics of the helicopter’s vertical rate of climb.

 

 

 

Maximum main rotor thrust in kg of AK1-3 in hover (vertical) flight mode. Standard atmospheric conditions.

This graph also indicates the maximum Out of Ground Effect (OGE) hover ceilings at varying gross weights.

 

This graph also indicates the maximum Out of Ground Effect (OGE) hover ceilings at varying gross weights.

At 740 kg gross weight.  With crop spraying option

Helicopter’s maximum vertical rate of climb speed versus altitude, for two weight configurations.

Note that the above graphs are for a vertical climb with zero airspeed.

 

 

Under standard atmospheric conditions and at gross weight  = 650 kg, the helicopters OGE ceiling is 1820 m (5,970 ft) and in ground Effect Cushion (IGE) it is = 2320 m (7,610 ft)

2. Level flight, climbing and autorotation decent

 

 

The service level-flight altitudes and airspeeds of the Ak1-3  for two flying weights are shown below.

The maximum flight speed near sea level is 186 kmh (100 knots)

Cruising speed at 75% engine power is 155 – 160 kmh (85 knots)

The best endurance flight speed is at 82 kmh. (44 knots)

 

The helicopters service ceiling is 5150 m (16,890 ft), but for the absence of oxygen equipment it is limited to a maximum continuous flight of 3000 m (approx. 10,000 ft)

 

The helicopters maximum level flight speed at altitudes in excess of 2500 m (8,200 ft) is limited to an “indicated” 150 kmh provided the advancing blade does not exceed critical Mach speed.

The AK1-3  power curve.

 

Power required (N HB ) and power available (N p ) versus airspeed.

The best flying speed to ensure the maximum flight range is equal to Vng=120 km/h. The helicopters design dry-tank range at an altitude of H=1000m and the best speed is L=350Km. The maximum endurance at an economy speed of V=82km/h is 3.2 h.

 

The available thrust reserve factor (Fig 6) ensures the helicopter’s acceptable rates of climb are implemented at a flight speed of V=82 km/h. Fig 6 shows the helicopter’s vertical rates of climb vs. its flight speeds at different altitudes. The maximum rate of climb is achieved near the ground and equals V=9m/s.

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