Frank Piasecki, a pioneer in helicopter engineering and design, passed away this week at 88. Piasecki successfully developed the tandem rotor helicopter, whose design heritage can still be seen flying today in the Boeing CH-47 Chinook (U.S. Army) and CH-46 Sea Knight (U.S. Marines) helicopters. His early tandem rotor designs were nicknamed the "flying banana" because of the shape of their main fuselage. Piasecki's tandem rotor design offered several advantages over conventional single rotor helicopters. Since the tandem rotors rotate in the opposite direction, they counteract each other's torque, so engine power doesn't have to be wasted to turn a tail rotor just for anti-torque purposes. All the engine power can be sent to the two large main rotor blades, thus allowing the tandem rotor helo to carry a large payload.  Also, the long tandem fuselage required to accommodate two main rotors also offers a wider center of gravity range, making the loading and transport of heavy cargo easier than single rotor helicopters.

Though not as well known to the general public as Igor Sikorsky (inventor of the first successful helicopter), working in the aerospace industry in the Philadelphia area, where Piasecki's companies were located, I was well aware of his vertical lift engineering exploits. One of his early companies, Vertol, was eventually sold and is today a division of aerospace industry giant Boeing. The Boeing engineering and manufacturing facility is located just south of Philadelphia International Airport, not too far from the location of the original Piasecki Helicopter Company.  This division of Boeing still manufactures the CH-47D/F models of the Chinook, along with components for the tilt-rotor V-22 Osprey. After selling the tandem rotor helicopter business, Piasecki formed another company to pursue other vertical lift concepts.  Some of those concepts, such as the flying Geep and the cargo hauler Heli-Stat, were rather unconventional.  The Heli-Stat mated four helicopters to a rigid frame slung under a large helium-filled blimp. The development of this lumbering leviathan was the result of a U.S. Forest Service requirement to look at concepts for lifting heavy loads of lumber from inaccessible forested areas.  Unfortunately the only prototype was destroyed in a spectacular crash at the the U.S. Naval Station in Lakehurst, N.J. in 1986.  Piasecki's latest company,  Piasecki Aircraft Corporation, is still doing vertical lift research and development outside of Philadelphia and is managed by two of his sons.