Method and apparatus for lifting a payload

A multi-rotor airframe comprising:

• a body portion;
• an energy storage device coupled to the body portion and configured to store electrical power;
• a first propulsion assembly mounted to the body portion and comprising a first internal combustion engine assembly, a first clutch, a first motor-generator, and a first rotor, wherein the first internal combustion engine assembly comprises a first internal combustion engine and a first internal combustion engine assembly output shaft, wherein the first motor-generator comprises a first motor-generator drive shaft having an input end and an output end, wherein the first rotor is configured to generate a first thrust in response to mechanical work transmitted to the first rotor by the first motor-generator drive shaft, wherein the first clutch is disposed between the first internal combustion engine assembly and the first motor-generator and operable to drivingly couple the input end of the first motor-generator drive shaft to the output end of the first internal combustion engine assembly output shaft and to drivingly uncouple the input end of the first motor-generator drive shaft from the output end of the first internal combustion engine assembly output shaft, wherein the first propulsion assembly is operable to rotate the first rotor via rotation of the first motor-generator drive shaft so that the first thrust is applied to the body portion in an upward direction relative to the body portion, and wherein the first motor-generator is operable to start the first internal combustion engine;
• a first motor controller configured to receive electrical power generated by the first motor-generator and direct the electrical power to the energy storage device;
• a second propulsion assembly comprising a second motor-generator and a second rotor, wherein the second motor-generator comprises a second motor-generator drive shaft having an output end, wherein the second rotor is configured to generate a second thrust in response to mechanical work applied to the second rotor via the second motor-generator drive shaft, wherein the second propulsion assembly is mounted to the body portion and operable to rotate the second rotor via rotation of the second motor-generator drive shaft so that the second thrust is applied to the body portion in a downward direction relative to the body portion, and wherein the downward direction is opposite to the upward direction;
• a second motor controller configured to receive electrical power from the energy storage device and direct the electrical power to the second motor-generator;
• an attitude sensor that is configured to generate an attitude signal according to an attitude of the multi-rotor airframe;
• and
• a flight controller that generates a first correction signal according to the attitude signal and an intended attitude value,
• wherein the first correction signal is directed to the second motor controller, and the second motor controller directs the electrical power to the second motor-generator in accordance with the first correction signal.