How Personal Air Vehicles Work

Fly-by-wire System

Springtail EFV-4A flight test held on March 16, 2005
Springtail EFV-4A flight test held on March 16, 2005
Photo courtesy

­A pilot could operate the original XFV prototype using two hand-control grips and ­control arms, and by shifting his or her weight from side to side. However, after applying that operations concept in the wind tunnel at the NASA AMES Research Center back in 2000, the testing team discovered that kinematic (body) movement was not going to allow the pilot sufficient control of the craft.

Currently, the Springtail uses fly-by-wire controls. In theory, this system is somewhat like the drive-by-wire systems designed for concept cars such as GM's Hy-wire. The operator controls the vehicle using two joysticks, one for each hand. The left joystick controls the rpm of the ducted fans (the altitude control). The right joystick controls forward and backward vehicle speed, left and right turns (roll), and turning the vehicle on its vertical axis (yaw). This is also known as a three-degrees-of-freedom control device.

As the operator uses the joysticks, his or her commands are fed to an onboard computer system. The computer system interprets this information and moves the ducts, control vanes and other control surfaces so that the vehicle moves to accommodate the operator's commands accordingly. The impressive onboard computer also gives the Springtail a sort of autopilot function. The operator can enter GPS coordinates for the vehicle to follow so that the Springtail's onboard computer system will "drive" him or her to the programmed destination.

In addition to regular flight movement, like a helicopter, the Springtail can hover in a stationary position. Hover-time really depends on wind conditions and altitude, but the average time is approximately two hours.

In the case of any catastrophic failure, the aircraft would automatically deploy a parachute to safely bring the craft and pilot down. In the event of initial main parachute malfunction, there's a back-up parachute for the pilot. It's designed to deploy automatically after the pilot has unbuckled himself from the Springtail and pushed away from the machine.

So, we've discussed the craft and its core technology, but does it work? Who's going to use it? And, how much does it cost? Let's find out.