Alphonse Pénaud (French pronunciation: [alfɔ̃s peno]; 31 May 1850 – 22 October 1880) was a French inventor and engineer who worked on early airplane designs in the 1800s. He was the first to use twisted rubber to power model airplanes, and his 1871 model airplane, called the Planophore, was the first to stay in the air without help. He later designed a full-sized airplane with many new features, but he could not find support for his project. He died by suicide in 1880 at the age of 30.

Biography

Alphonse Pénaud was born in Paris to a family connected to the navy. His father, Charles Pénaud, was an admiral in the French Navy. Due to a hip condition, Pénaud used crutches to walk and could not attend the Naval School. At age 20, he began studying aviation and joined the newly created French Aeronautical Society. He became vice-president of the society in 1876 and helped publish a journal called L'Aéronaute.

In 1870, Pénaud built the first of several successful model helicopters. The idea of using rotating blades for flight was not new, as it had been shown to the French Academy of Sciences in 1784 by M. Launoy and M. Bienvenu, and later studied by Sir George Cayley. However, Pénaud was the first to use twisted rubber to power a flying model. Many later experimenters, including Lawrence Hargrave and A.V. Roe, used this method for their models.

The next year, Pénaud created the Planophore, which influenced early aircraft design. This model used a twisted rubber motor to turn a pusher propeller. It also introduced two important features: the wings curved upward at the tips (a design called dihedral), and the rear horizontal stabilizer was set at a smaller angle than the wings. These features helped the Planophore stay stable in the air. The idea of dihedral had been studied by Sir George Cayley, but Pénaud was unaware of this work at the time. The difference in angle between the wings and the stabilizer was a new idea from Pénaud. The Planophore was flown successfully in Paris on August 18, 1871, covering 131 feet (40 meters) and staying in the air for 11 seconds.

The Planophore was 51 centimeters (20 inches) long, with a wingspan of 46 centimeters (18 inches) and a wing area of 0.05 square meters (0.53 square feet). It had a two-bladed propeller 20 centimeters (8 inches) in diameter and weighed 16 grams (0.56 ounces), with 5 grams (0.17 ounces) from the rubber.

In 1872, Pénaud built a rubber-powered ornithopter, a model that flaps its wings like a bird. Both the helicopter and ornithopter were popular as toys. In 1873, he worked with engineer Paul Gauchot to design two full-sized aircraft, the first in 1874 and the second in 1876. The 1876 design included detailed drawings for a patent and featured advanced ideas, such as electrically controlled elevators, an enclosed cockpit for the pilot, a retractable landing gear, and two propellers spinning in opposite directions to reduce twisting forces.

Pénaud also worked on lighter-than-air flight and created tools like a differential barometer to measure the speed of rising or falling.

Alphonse Pénaud could not find financial support for his projects and died by suicide on October 22, 1880, at age 30.

Influence

• Octave Chanute detailed Pénaud's experiments in his book Progress in Flying Machines.
• In 1878, the Wright Brothers received a helicopter of the Pénaud type from their father. They later said it inspired their interest in flight.
• Pénaud is one of the aviation pioneers who did not achieve success and is named in Marc Blitzstein's composition The Airborne Symphony.