The US Army is has prioritized the development of a quieter helicopter design that will enable it to operate these vehicles for surveillance and cargo transportation without the noise of traditional helicopters. The military has zeroed in on eVTOL tech as its potential solution, meaning future Army helicopters may resemble drones.
Helicopters are vertical take-off and landing (VTOL) vehicles, meaning they rise straight up into the air and descend back down in the same way. This design is also used for consumer and many commercial drones, though there’s a very big, obvious difference: the rotors.
Whereas helicopters have a very large rotor that produces a loud noise, drones have multiple small rotors that reduce the noise level. The US Army is eyeing this type of design for future helicopters, ones that may feature an electric VTOL platform with multiple smaller rotors.
The result, the Army notes in its press release, will possibly be a different sound than we’re used to hearing from helicopters. A study was used to confirm that eVTOL will produce different noise, noting that stacked rotors may decrease noise and increase performance compared to traditional rotors with blades along a single plane.
Army research engineer Dr. George Jacobellis explained:
I do think that a stacked rotor can be beneficial for eVTOL applications. The added degree of freedom for the design will allow for gains in efficiency and control over the acoustic signature, which has been shown in the results. More investigation is needed, however, to quantify the noise reduction with axial spacing.