Impact of SR/C™ Technology
At its core, SR/C™ Technology represents the simple yet elegant hybridization of airplanes and rotorcraft through remarkable innovations in engineering design. The extraordinary performance capabilities of this technology (1) have been developed and honed over nearly twenty (20) years, (2) have been independently verified by NASA, the U.S. Army, and the nation’s top Center for Rotorcraft Excellence at the Georgia Institute of Technology, (3) were first demonstrated by the CarterCopter Technology Demonstrator (the "CCTD"), and (4) are being demonstrated by the SR/C™ 4-Place Personal Air Vehicle (the "PAV"). While performance testing of the PAV remains ongoing – for the purpose of expanding the high-speed envelope – these two prototypes have proven the ability of SR/C™ aircraft to outperform the speed, range, service ceiling, and efficiency of any rotorcraft (or other VTOL aircraft), while retaining their VTOL capability.
Key Features of CarterCopters with SR/C™ Technology
- Speed – A slowed rotor allows the aircraft to fly at 450 kts without the rotor advancing tip speed exceeding Mach .95 (there are some business jets where the whole aircraft flies at mach .92+).
- Cruise Efficiency – The slowed rotor (no variable speed transmission required) reduces the rotational drag so dramatically that the rotor drag becomes only about 10% of the total aircraft drag – basically a function of the rotor wetted area. (Rotor drag is a function of rpm cubed – e.g. dropping the rotor rpm from 300 to 100 reduces the rotational drag by a factor of 27.)
- Vertical Takeoff and Landing – Both jump takeoff and hovering versions have the ability to operate without runways at low cost, which will revolutionize regional civilian air transportation.
- Small simple high AR wing – Since the rotor provides the lift for hover and slow speed flight, the wing can be sized for cruise flight – about ¼ the size of general aviation aircraft and consequently about ¼ the profile drag and without the need for high lift devices.
- Impossible blade stall – Since the wing provides the lift at cruise, the rotor does not need to provide any lift and therefore there are no retreating blade stall issues as with conventional helicopters at high speed. The rotor plane of rotation and blade angle of attack is nearly aligned with the airstream at cruise speeds – too low of angles of attack for retreating blade stall to occur. This also aligns the rotor hub fairing with the airstream for very low drag.
- No cruise rotor noise – The slowed rotor also reduces the noise so significantly that during a flyover at ~600’ (200 m) above the ground, you cannot hear the rotor noise over the engine noise – it is as quiet as a fixed wing aircraft.
- Hover and low speed efficiency - With the dramatic reduction in slowed rotor drag, SR/C aircraft can operate with a low disk loaded rotor, so the hover and or jump takeoff efficiencies are high.
- Fixed wing smoothness – With a tall tilting mast supported with flexible supports, the rotor loads are essentially isolated from the fuselage, even for 2-bladed rotors. The tall mast also handles large CG variations, optimizes wing AOA for best CL over a wide low/medium speed range, and controls rotor rpm from medium forward speed to cruise
- Unparalleled safety – Since the rotor is always in autorotation and has extreme tip weights for stability at high aircraft speed and low rotor rpm flight, it acts as a built-in parachute, but better because it can operate at any airspeed or altitude to provide a very soft zero roll landing for unparalleled safety – a total engine(s) failure is not necessarily a life threatening event, but could be more of an inconvenience.
- Landing Gear safety – Carter has developed a smart mechanical landing gear that can determine the impact velocity in the first inch of deflection and then apply a constant pressure/de-acceleration over a large stroke to provide safe 24 – 36 ft/sec impact landings. The gear can be light weight since the loads are nearly constant, spread over the entire stroke.
In no uncertain terms, this game-changing technology is fully capable – and on the brink – of emerging and taking hold in both the fixed-wing aircraft and helicopter markets.
As SR/C™ Technology pertains to the fixed-wing aircraft market:
SR/C™ aircraft are essentially fixed-wing aircraft; the difference being that SR/C™ aircraft utilize a very simple rotor as an extremely efficient high-lift device for vertical through intermediate-speed flight. As speed increases, more and more of the weight of the aircraft is transferred from the rotor to the wing. At cruise speed, the rotor is slowed to the slowest safe rpm to decrease the rotational drag. During high-speed flight, we are able to make the rotor all but disappear (from a drag standpoint) by slowing it down. In order to do this, Carter Aviation has identified and overcome no less than ten (10) technical issues – each of which has to be addressed before the rotor can be safely slowed and advance ratios (Mu) of 0.75 – and well beyond – can be achieved. These innovations comprise a significant portion of our patent portfolio.
Since the wing of an SR/C™ aircraft is sized for efficient cruise, the wing area can be much smaller than that of a comparably-sized fixed-wing aircraft. The result is substantially increased efficiency, range, speed, and service ceiling (conservatively up to 25,000 feet, and more like 35,000 feet, with the current prototype and up to 45,000 feet with a follow-on SR/C™ 6-9 Place Business Aircraft).
Thus, incorporation of SR/C™ Technology affords aircraft the ability to retain the speed, range and efficiency of a fixed-wing aircraft, but with the added benefit of VTOL.
As SR/C™ Technology pertains to the helicopter market:
Hovering SR/C™ aircraft are able to fulfill any mission currently performed by a helicopter, but with more than twice the speed and three times the range of existing helicopters. Jump takeoff SR/C™ aircraft are fully capable of satisfying the requirements of the vast majority of helicopter missions, without the added cost, complexity and weight inextricably intertwined with systems having full hover capability, e.g., heavy gearbox, complicated heavy rotor-head / swash plate system and counter-torque device. This is because the extreme inertia that can be stored in the rotor allows SR/C™ aircraft to hover for approximately ten seconds based on the maximum in flight rpm and fifteen seconds based on maximum takeoff rpm. (By using stored rotor inertia to drive the rotor, the need to counter the torque associated with extended hover is eliminated.)
Put into the context of offshore operations, a hovering SR/C™ aircraft would be able to reach platforms in less than half the time or at three times the distance compared to a helicopter. Even jump takeoff SR/C™ aircraft, with the ability to hover for ten seconds, will allow the aircraft to make safe approaches / landings on oil rigs and ships. The ability to land on floating structures is further facilitated by Carter Aviation’s patented lightweight extreme energy absorbing landing gear. The configuration used on our current prototype is capable of absorbing a twenty feet per second landing. Above is a video containing footage showcasing the capabilities of Carter Aviation’s landing gear system.
Jump takeoff SR/C™ aircraft are well-suited to serve much of the market currently served by conventional helicopters, while hover SR/C™ aircraft expand SR/C™ capabilities to those missions requiring hover, such as search-and-rescue and logging operations. All SR/C™ aircraft benefit from the advantages of the technology – being lighter and having more than twice the speed and three times the range of a comparably-sized conventional helicopter.