P-V Engineering Forum PV-2
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.
Gift of Frank Piasecki
- Country of Origin
- United States of America
- Piasecki Helicopter Corporation
- CRAFT-Rotary Wing
- Rotor Diameter: 7.7 m each (25 ft 2 in)
- Length: 7.7 m (25 ft 5.25 in)
- Height: 2.36 m (7 ft 9 in)
- Weights: Empty, 327 kg (720 lb)
- Gross, 454 kg (1,000 lb)
When Igor Sikorsky began to demonstrate his VS-300 helicopter, he presented it as the automobile of the future. This idea quickly captured the public imagination, and a number of enthusiastic 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. His PV-2 was constructed with fewer resources than Sikorsky's aircraft, yet it flew with a smoothness and stability that was lacking in the VS-300. Ironically, while Frank Piasecki's first helicopter design was intended as the shape of things to come in personal transportation, his company established itself as the foremost manufacturer of large helicopters sold primarily to the armed forces.
Piasecki had an early start 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, the P-V Engineering Forum. The company's first helicopter effort, the PV-1, did not advance beyond the drawing boards. That design was to have used ducted air as a safer and more efficient alternative to a tail-rotor. However, it became obvious that this could not be done efficiently with the current technology and plans were formulated for a new design along the lines of Sikorsky's tail-rotor equipped model.
Piasecki soon left Platt-LePage in disgust over their haphazard approach to engineering, and concentrated all his efforts on the P-V Engineering Forum's new model, designated the PV-2. This design was only intended as a small single-seat demonstrator, either as the basis for a production aircraft, or to generate contracts for other models. While the small team of engineers came up with a sound design, finding actual components with little money and acute wartime shortages required expert scrounging skills. Airplane parts were found at airports and junkyards, while those critical to a helicopter were designed and fabricated carefully. A Franklin 90-horsepower four cylinder airplane engine was shipped from the factory to be mounted under the rotor. To avoid complex gearing, the engine needed to be mounted vertically, but airplane engines were designed for horizontal installation. To solve the problem, tubes from the overhead valve rocker boxes drained the oil to an external oil tank rather than through the push rod covers. Engine oil also was collected at the back of the engine where the two magnetos are located. One magneto was removed and small fabricated gear box was installed. A shaft driven by the engine camshaft extended to an oil pump salvaged from a Packard automobile to scavenge the oil, pumping it to the external oil tank. A pair of bevel gears on the extension shaft drove the magneto connected to that gearbox. During the flight testing, oil temperature was excessive so that a radiator from a salvaged automobile cabin heater was installed in the oil return line. A clutch from a Chevrolet dealer connected the engine flywheel to a shaft with universal joints to the transmission. The rotor transmission consisted of a herringbone pinion and gear set with an overrunning clutch obtained from a Studebaker dealer attached to the pinion. The gear was attached to the hollow rotor shaft with pins to avoid the additional cost of splines. The rotor shaft was supported by a pair of angular contact ball bearings in the housing. The pinion was supported by a pair of needle roller bearings. The housing consisted of the frustums of two similar cones joined at the large diameter and the shaft bearing housings at the small ends. They were joined by sheet steel formed and brazed. The tail rotor gear box was the lower end of salvaged outboard motor. The wheels, pilot’s seat, ignition switch, and instruments were found at airports, while the blade lag dampers were found at a scrap yard near the Pitcairn Autogiro factory.
Elliot Daland, a venerable and experienced engineer, who had also worked on the XR-1, oversaw the design and construction of the three rotor blades. Steel tubing was used for the main spar. Solid spruce was bonded fore and aft of the spar, covered with thin birch plywood shaped to the NACA 0012 airfoil. The aft portion of the airfoil was formed by bass wood ribs and a plywood trailing edge. The most important innovation was the static and dynamic balancing of the blades with small trim weights before the final fabric cover was applied. Daland’s premise was that dynamic balancing was necessary for smoothest operation in forward flight where the advancing blade (the one swinging towards the front of the aircraft) encounters greater drag due to its higher velocity and the retreating blade encounters less drag due to its lower velocity. The varying forces drove a pendulum motion about the vertical pin. The blades were first teeter balanced against each other by attaching small weights to the back of the spar. All three blades were hung, supported by knife edge pins, with the blade chords parallel. All three were displaced and allowed to swing freely. The period of each blade's swing was noted. The balance weight on the blade with the longest period was replaced with a greater weight inboard and the opposite for the shortest period. The teeter and swing checks were repeated and the weights adjusted until criteria were met. Achieving this, the fabric cover was applied and several coats of dope applied.
The PV-2's first flight occurred by accident when a frayed clothes line that was intended to keep the aircraft tethered broke and the helicopter became airborne. Frank Piasecki was at the controls, and managed to safely land the aircraft in spite of the fact that he had no previous flight time in helicopters and only fourteen hours in fixed wing aircraft. He remained as the chief test pilot for the PV-2, in addition to his duties as chief engineer and company president. Because of the company's dire financial situation, resulting from no income or financial backing, the PV-2 was handled with extreme care and flown only as necessary for testing. To generate business that would result in essential income, Piasecki decided to try to capitalize on wartime military contracts. His breakthrough came on October 20, 1943, when he flew the aircraft at Washington's National Airport for a large crowd of military officials and government onlookers. In preparation for the demonstration, Piasecki gave the aircraft a more finished appearance with a silver and maroon color scheme, his favorite. The Navy was particularly interested in Piasecki's demonstration as it had come under Congressional scrutiny for largely ignoring helicopter developments generated by Army Air Forces (AAF) investment, and was looking for a company that would be more focused on their specialized needs. The Navy had purchased some Sikorsky models, but these did not meet its demands for a helicopter that could carry heavy sonar gear or pick up a number of stranded crewmen from a torpedoed vessel. Sikorsky was also stretched to the limit meeting AAF demands, and the PV Engineering Forum was the only other company to have demonstrated a practical helicopter. Additionally, the Navy could be guaranteed to have Piasecki's full attention.
The PV-2's demonstration allowed Frank Piasecki to successfully approach the Navy with his proposal for a prototype tandem rotor design that could serve as the basis for a large rescue and anti-submarine warfare (ASW) helicopter. This contract became the PV-3, later known as the X-HRPX (see NASM collection). Along with outside investors, the resulting HRP-1 production contract provided enough cash inflow to allow the company, in its various forms, to become the prime supplier of large transport helicopters for several decades.
Even though the PV-2 had accomplished its goal by demonstrating the PV Engineering Forum's ability to construct a practical helicopter, its useful days were not over. Once it appeared that a government contract would be guaranteed, Frank Piasecki began to take more risks with the aircraft to promote helicopters in general and his company in particular. The PV-2 achieved national acclaim when it starred in a newsreel entitled "An Air Flivver in Every Garage." The short film included sequences of Frank Piasecki landing at a golf course and a neighborhood gas station. The gas station sequence was particularly risky as many obstructions bordered the narrow landing area. After the film achieved its goal of enticing investment, the PV-2 was only flown for special functions, but it remained with Piasecki, until 1965 when he donated it to the Smithsonian Institution. The goal of mass-produced helicopters for suburban garages turned out be an unrealistic fantasy, but the diminutive PV-2 helped to demonstrate to the nation that helicopter were here to stay.
Rotor Diameter: 7.67 m each (25 ft 2 in)
Length: 7.75 m (25 ft 5.25 in)
Height: 2.36 m (7 ft 9 in)
Weight: Empty, 326.6 kg (720 lb)
Gross, 454 kg (1,000 lb)
Engine: Franklin, 90 h.p.