ALFLEX(Automatic Landing Flight Experiment) vehicle

The ALFLEX vehicle is based on a 37% scale 1992 HOPE design. The size of the vehicle was chosen considering the volume required for onboard systems and to give representative dynamic characteristics.

In an automatic landing test flight, the vehicle is lifted to a predefined release point suspended from a helicopter, then released into gliding free flight. It then navigates autonomously to a runway and carries out a conventional landing. An overview of the landing flight path is shown on the right. The most unusual characteristic is the steep flight path angle of about 30 degrees, compared to the usual 3 degree glide path of a conventional aircraft making a power-on landing. This steep angle is a consequence of the fact that the vehicle is unpowered, the glide path angle almost corresponding to an equilibrium glide condition and reflecting the low lift-to-drag ratio. The steep approach makes achieving a smooth touchdown on the runway with just a single flare difficult, so a pre-flare is made to enter a 1.5 degree Shallow Glideslope phase just before the runway, with a final flare made just before touchdown.