Parafoil

Illustrations from Jalbert's 1966 patent, showing the keels and the airfoil shape.

The NASA X-38 prototype makes a gentle lakebed landing at the end of a July 1999 test flight at the Dryden Flight Research Center.

A parafoil is a nonrigid (textile) airfoil with an aerodynamic cell structure which is inflated by the wind. Ram-air inflation forces the parafoil into a classic wing cross-section. Parafoils are most commonly constructed out of ripstop nylon.

The device was developed in 1964 by Domina Jalbert (1904–1991). Jalbert had a history of designing kites and was involved in the development of hybrid balloon-kite aerial platforms for carrying scientific instruments. He envisaged the parafoil would be used to suspend an aerial platform or for the recovery of space equipment. A patent was granted in 1966.

Deployment shock prevented the parafoil's immediate acceptance as a parachute. It was not until the addition of a drag canopy on the riser lines (known as a "slider") which slowed their spread that the parafoil became a suitable parachute. Compared to a simple round canopy, a parafoil parachute has greater steerability, will glide further and allows greater control of the rate of descent; the parachute format is mechanically a hang glider of the free-flight kite type and such aspects spawned paraglider use.

The air flow into the parafoil is coming more from below than the flight path might suggest, so the frontmost ropes tow against the airflow. When gliding, however, the angle of attack is lowered and the airflow meets the parafoil head on. This makes it difficult to achieve an optimum gliding angle without the parafoil deflating.

In 1984 Jalbert was awarded the Fédération Aéronautique Internationale (FAI) Gold Parachuting Medal for inventing the parafoil.

Parafoils see wide use in a variety of windsports such as kite flying, powered parachutes, paragliding, wingsuit flying and skydiving. The world's largest kite is a parafoil-variant.

Patents

• U.S. Patent 3,285,546 Multi-cell wing type aerial device, filed October 1964, issued November 1966

Domina told me he got the idea for the foil while a passenger on a Lockheed Electra while looking out the window. I met him years ago in Boca Raton when we had a fire on the envelope of our Hot Air Balloon that resulted from a propane leak. Domina came up and offered the use of his shop to repair our balloon. While at his shop I saw his Jalbert Aerial Sled and this was in the late 1960's. He deserves much more credit for Aviation safety and pioneering than he gets. My credentials are FAA Parachute Rigger, United States Parachute Association Life Member, FAA A&P Mechanic, USAF and ROTC Instructor. There are others, but the main source is "The Parachute Manual" by Dan Poynter as it is the technical manual for parachute equipment world wide, and my personal relationship with Domina Jalbert, a true gentleman, in every sense of the word. He is missed like all those that are the best of humankind, remarkable and gone too soon.

See also

• Foil kite