PIASECKI  PV-2

 Cuando Igor Sikorsky comenzó a publicitar su VS-300 en 1941, lo llamó el automóvil del futuro. La idea prendió rápidamente en el público. El 11 de abril de 1943, Frank Piasecki fue el segundo americano en volar su propio helicóptero, el Piasecki-Venzie PV-2. Lo construyo con menos recursos que el VS-300 pero así todo voló con gran suceso. Irónicamente, Frank Piasecki intentó que su primer diseño fuese la futura revolución en el transporte personal civil, pero su compañía fue la primera en venderle a los militares.

Piasecki comenzó en la industria aeronáutica cuando se asoció a Platt-LePage Aircraft Company en 1940 como ingeniero en el XR-1. Al mismo tiempo, comenzó una consultoría con Harold Venzie llamada Piasecki-Venzie Engineering Forum. Venzie y Piasecki habían estudiado ingeniería juntos en  la universidad de Pennsylvania. El primer diseño, el PV-1, no pasó de los papeles. Este diseño utilizaba conductos de aire para contrarrestar el torque producido por el rotor principal.

Piasecki abandonó rápidamente a Platt-LePage y comenzó a concentrar su esfuerzo en un nuevo proyecto, el PV-2, helicóptero convencional con rotor principal y rotor de cola. Debido a que estaban en guerra y tenían bajos fondos el grupo consiguió un fuselaje de un Curtiss-Wright CW-1 Junior y juntó otras piezas de rezagos de automóviles y en chatarrerías. Piasecki contrató también a estudiantes de ingeniería para dibujar los planos sin costo para la compañía. Un área donde no podía bajar costos era en el motor, este debía ser compacto, liviano y proveer suficiente potencia. El único modelo que la compañía consiguió fue un Franklin de 90 HP. Los ingenieros montaron el motor en forma vertical pero al no estar diseñado para trabajar en esta forma debieron realizarle algunas mejoras.

La transmisión consistía mayormente en descartes de partes de automóviles pero las palas del rotor fueron obras de arte de la ingeniería, las cuales contribuyeron en mucho a el éxito del PV-2. El ingeniero Elliot Daland fue el que supervisó la construcción de las tres palas del rotor principal, para eso utilizó mucho de los componentes utilizados en aviones. Utilizó un tubo de acero como larguero principal y las costillas de madera de abedul contrachapada. La mas importante modificación que realizó Daland fue el incorporar un peso ajustable para poder balancearlas dinámicamente. Sikorsky había descubierto que era muy importante balancear las palas estáticamente pero fue Piasecki el primero en descubrir que las palas debían tener todas el mismo centro de gravedad en el mismo punto.

En Piasecki también se impuso otra novedad para reducir las vibraciones, construyeron las palas para que el centro de gravedad estuviera por delante del centro de aerodinámico.

Una vez finalizada la construcción del PV-2, la aeronave fue pintada de color plata con rayas castañas, los colores oficiales de la universidad de Pennsylvania.

El primer vuelo libre del PV-2 fue por accidente. Una de la cuerdas que lo sostenían se cortó, pero Frank Piasecki, que estaba en los controles, aterrizó seguramente, a pesar de su ausencia de experiencia, ya que solo contaba con 14 horas de vuelo en aeronaves de ala fija. Debido a que la compañía estaba casi en la bancarrota y que lo único de valor era el PV-2, este se volaba solo para las pruebas. Esto fue el 11 de abril de 1943.

Para generar negocios, Piasecki decidió tratar de conseguir contratos entre los militares. Un gran adelanto sobrevino el 20 de octubre de 1943 cuando voló delante de muchos oficiales y gobernantes en el Washington National Airport. La marina mostró especial interés, entonces Piasecki los convenció de construir un prototipo que tuviese dos rotores en tamdem . Esta aeronave tendría la habilidad de realizar rescates y guerra antisubmarina utilizando un sonar bastante pesado. Así fue como nació el PV-3, conocido mas tarde como X-HRPX Dogship.

Después de la firma del contrato por el PV-3, Piasecki prosiguió a su propio riesgo con el desarrollo del PV-2, realizando presentaciones para promover a la compañía y al helicóptero. El helicóptero permaneció en la fabrica hasta 1965 cuando lo donaron al Smithsonian Institution.

 When Igor Sikorsky began to publicly demonstrate his VS-300 helicopter in 1941, he called it the automobile of the future. This idea quickly captured the public imagination and enthusiastic helicopter designers stepped forward to produce the next aerial version of the Model T. On April 11, 1943, Frank Piasecki became the second American to successfully fly a helicopter of his own design, the Piasecki-Venzie PV-2. He built it with far fewer resources than Sikorsky had available to construct the VS-300, yet the PV-2 flew with an unprecedented smoothness and stability. Ironically, Frank Piasecki intended his first helicopter design to be the forerunner of a revolution in personal transportation, but his company actually evolved into one of the foremost manufacturers of large cargo helicopters sold primarily to the military.

Piasecki started early in the helicopter industry when he joined the Platt-LePage Aircraft Company in 1940 as an engineer working on the XR-1 (see NASM collection). At the same time, he started a small consulting firm with Harold Venzie called the Piasecki-Venzie Engineering Forum. Venzie and Piasecki had studied engineering together at the University of Pennsylvania. The company's first helicopter effort, the PV-1, did not advance beyond the drawing board. This design employed ducted-air to counteract the torque produced by the main rotor. Although advanced, safer and potentially more efficient than a conventional tail rotor, the concept went beyond what was possible with available technology and Piasecki began to lay out a new design equipped with single main and tail rotors.

Piasecki soon left Platt-LePage in disgust over their haphazard approach to engineering and began to concentrate all his efforts on the P-V Engineering Forum's new single main and tail rotor model, designated the PV-2. This aircraft was only a small single-seat demonstrator. Piasecki and the P-V team hoped it would lead to a production personal transport sold to individual customers, or generate contracts for other models. While the small team of engineers focused on the design, finding actual components with little money and acute wartime shortages required expert scrounging. The group obtained a discarded Curtiss-Wright CW-1 Junior (see NASM collection) fuselage airframe and they found many of the engine accessories and transmission components in automotive dealerships or junkyards. Piasecki also enlisted the students at local engineering schools to draft blueprints - at no cost to the company. One area where Piasecki could not cut corners was the engine. It had to be compact, lightweight, and still provide sufficient power. The only suitable model that the company found was a 90 horsepower Franklin. The engineers mounted the motor vertically but it was not designed to operate in this position and the lubication system required some modification.

The transmission consisted almost entirely of junked automobile parts but the rotor blades were masterpieces of new engineering that contributed much to the ultimate success of the PV-2. At PV Engineering, Elliot Daland was a respected and experienced engineer who had also worked on the XR-1 at Platt-LePage. He oversaw construction of the three main rotor blades used on the PV-2. Daland designed and built each blade using many of the components found in a conventional airplane wing. This method followed standard practice in the helicopter industry. He used steel tubing for the main spar, solid spruce formed the leading edge, and the ribs consisted of pieces of birch plywood cut, glued, and nailed together. After final adjustments, workmen covered the rotor blades with fabric.

Daland's most important innovation was incorporating adjustable trim weights on these blades to allow easy dynamic balancing. Sikorsky had discovered the value in blades that weighed the same to minimize destructive vibration, but Piasecki first realized that the blades on a helicopter must have the same Centers of Gravity. Daland devised a relatively easy way to do this. He would balance the blades dynamically by hanging the blade from its root end and swinging it like a pendulum. Workmen then added or removed trim weights until the set of PV-2 blades swung the same way in frequency and amplitude. Sikorsky only balanced his early production helicopter blades statically, on the assembly line, but this did not cure chronic vibration.

The PV Engineering Forum introduced another innovation to reduce rotor vibration. Engineers built the blades so that the Center-of-Gravity fell at a point forward of the Center-of-Lift. By using this arrangement, any abrupt blade deflections caused by sudden turbulence forced the blade leading edge to pivot into the wind gust. This reaction worked to stabilize the blade and further reduce vibration. In a nod to the citizen pilot, PV Engineering ingeniously designed two of the blades to fold back over the tail. This feature allowed a pilot to stow the helicopter in a standard garage, or even tow it behind his car. Once the construction phase was complete, the entire aircraft was painted silver with maroon trim and lettering, official colors of the University of Pennsylvania.

The PV-2 first flew by accident. A frayed clothesline tethering the aircraft safely to the ground suddenly snapped and the helicopter became airborne. Frank Piasecki was at the controls and managed to safely land, despite his complete lack of previous flight experience in helicopters. He had only fourteen hours of flight time in fixed-wing aircraft. This brush with disaster did not deter the plucky pioneer and Piasecki remained the chief test pilot for the PV-2, in addition to his duties as chief engineer and company president. At that time, the company was not generating any income and it had not attracted any financial backing so the financial situation was dire. The PV-2 was PV Engineering's most valuable asset and the firm handled it with extreme care, flying only as necessary for testing.

To generate business, Piasecki decided to try capitalizing on wartime military contracts. A breakthrough came on October 20, 1943, when he flew the aircraft before a large crowd of military officials and government onlookers at Washington's National Airport. The Navy showed particular interest in Piasecki's demonstration. The service had come under Congressional scrutiny for largely ignoring helicopter developments generated by Army Air Force (AAF) investment and Navy leaders were looking for a company that could cater to their specialized needs. The Navy had purchased and toyed with several Sikorsky models, but these failed to meet fleet demands for a helicopter that could carry heavy sonar gear or pick up crewmen stranded at sea. Sikorsky was stretched to the limit trying to meet AAF orders, but the PV Engineering Forum could give full attention to Navy requirements. They were also the only other U. S. company to demonstrate a practical helicopter up to that time.

Piasecki convinced Navy leaders to fund his proposal to build and fly a prototype that featured two main rotors mounted in tandem. This large machine could perform rescue work or conduct anti-submarine warfare (ASW) using heavy sonar gear. PV designated the aircraft the PV-3, but it was later known as the X-HRPX Dogship. The Dogship attracted several outside investors and led to a production contract to build the HRP-1.

Long after the Navy and PV Engineering Forum signed a contract for the new tandem rotor design, Frank Piasecki continued to risk himself and the PV-2 during flight demonstrations to promote helicopters and the company. The PV-2 won national acclaim when it starred in the newsreel called "An Air Flivver in Every Garage." This short film included sequences of Piasecki landing at a golf course and a gas station. The latter locale was particularly risky as many light poles and other obstructions bordered the narrow landing area. The film enticed some to invest in the firm but thereafter, the PV-2 only flew rarely during special functions. The helicopter remained with Piasecki until 1965 when he donated it to the Smithsonian Institution.

Characteristics
Características

Information
Información

Characteristics
Características

Information
Información

1943

   1 Franklin
4 Cilindros
Opuestos

1

90 HP

720 Lb

Ft

Lb

Ft

Kts

 Ft

 Kts

NM