Check out the double-rotor helicopter that could be the US Army's next Black Hawk
The Osprey: Half-airplane, half-helicopter, totally badass
Are two rotor heads better than one? - Model Airplane News
Old Russian Double Rotor Helicopter K-26 Isolated Over White Stock Image - Image of rotor, military: 81407771
Birotor Coaxial High Capacity Helicopter - rpahelicopters
.jpg "Sikorsky's S-97 Raider Helicopter Is a Pirouetting Speedster | WIRED")
Sikorsky's S-97 Raider Helicopter Is a Pirouetting Speedster | WIRED
Twin rotor helicopters hi-res stock photography and images - Alamy
Sikorsky Exploring Third 'X2' Twin Rotor Military Helicopter | Aviation Week Network
Coaxial RC Helicopters
Sikorsky tests radical dual rotor helicopter that can reach 276 mph | Daily Mail Online
Piasecki YH-21 Work-Horse | This Day in Aviation
New UAE Firm Launches Light Twin-rotor Helicopter | News: Aviation International News
Lockheed Martin's K-MAX Helicopter Boasts Dual Crossing Rotors for Increased Precision, Here's an Up-Close Look - TechEBlog
Coaxial rotors - Wikipedia
Why do some Russian helicopters have two sets of rotor blades but such design could not be found in the West? - Quora
auto rotation - Is it possible to fly a tandem-rotor helicopter after a single rotor failure? - Aviation Stack Exchange
Kaman K-Max Dual Intermeshing Rotor Helicopter Demo – AIN - YouTube
Dual rotors could make the Defiant one of the world's fastest helicopters
Tandem rotors - Wikipedia
Boeing to build another six special forces MH-47G twin-rotor heavy-lift helicopters in $212.6 million order | Military Aerospace
Tandem rotor helicopter hi-res stock photography and images - Alamy
The two high speed dual rotor craft fighting to replace the Black Hawk revealed | Daily Mail Online
Helicopter Rotor Systems Configuration | SKYbrary Aviation Safety
Heavy Lift Helicopter Fleet | Columbia CH-47D, Columbia 234 UT, Columbia 234 LR, Vertol 107 - II | Overview, Learn More | Columbia Helicopters
Sikorsky, Boeing debut future vertical lift dual-rotor design with SB>1 DEFIANT helicopter
This Soviet Twin-Rotor Helicopter Design Was A High-Speed Rival To The Mi-24 Hind
