The Helicopter

Airplane (fixed-wing) and helicopter (rotorcraft) pilots are two sides of the same coin and the two enjoy a playful repartee.  Ask a Merlin One pilot and he’s likely to claim that a “helicopter doesn’t fly; it beats the air into submission.”

 

The idea of generating lift from rotation has been around since about 400 B.C. but the first helicopter didn’t become airborne until almost four years after the Wright brothers made history in Kill Devil Hills.  After its maiden flight, the development of the helicopter stalled.  It wasn’t until the 1920s and the invention of the “cyclic” and “collective” that substantive progress was made.

 

The cyclic is a control that allows the pilot to increase or decrease lift by warping, or changing the pitch angle of each rotor blade by differing amounts.  By manipulating the lift produced by each blade independently, the force differential can be used to maneuver the helicopter in the preferred direction.

 

The collective controls the pitch of all the rotor blades simultaneously as opposed to individually, and thus allows the vehicle to move (more or less) straight up and down.  Obviously, this separation of roll and pitch is one of the biggest differences between airplanes and helicopters.

 

Early helicopters struggled with stability even after the leap forward in cyclic and collective controls.  The aerodynamic drag associated with the torque of the rotor required an opposing force and it would be almost 20 years until such a solution presented itself.  On May 3, 1940, Igor Sikorsky’s VS-300 took off for the first time.  The VS-300 employed Sikorsky’s ground-breaking innovation of producing counter-torque through a small, vertical-plane tail rotor attached to the end of a boom.  The VS-300 paved the way for the first large-scale, mass-produced helicopter: the R-4 (131 units shipped).  The R-4 has the distinction of being the only helicopter used by the Allies in WWII.

 

 

Despite the improvement in stability and control, helicopters were almost uniformly underpowered until the 1950s.  In the late 1940s the turboshaft engine was invented and by the early ‘50s was adapted for helicopters.  Until that time, the weight of piston engines and their engine blocks made it very difficult to generate enough lift from the rotor.  Turboshaft engines were able to produce much more power without the same weight penalty.  By the time the Vietnam War rolled around, the helicopter, most notably, the venerable Huey had graduated from its role in an occasional search-and-rescue mission to becoming the new ‘horse’ of the U.S. Cavalry.

 

While Sikorsky developed designs within the military market, Bell Aircraft was focused on the commercial market.  Bell, led by Arthur Young, developed a weighted stabilizer bar which was placed perpendicular to the rotor blades.  The simplicity of the design and remarkable ease of use enabled the resulting aircraft, the Bell 47, to become the most popular helicopter model for almost 30 years.

 

From its humble beginnings, the helicopter market grew to $3.68 billion in 2017.  While airplane and helicopter pilots are likely to maintain their own biases and preferences, it’s not hard to see (objectively): the sky is big enough for both.  Just keep in mind, “If the wings are travelling faster than the fuselage, it’s probably a helicopter.”

 

David Mann


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