Macross: Deculture~!: About Valkyries

A Variable Fighter is a series of fictional transforming aerospace fighter mecha primarily designed by Studio Nue's Shoji Kawamori for the animated series The Super Dimension Fortress Macross and later related projects. It is also known as Valkyrie in the Macross universe, due to the great popularity of the first known variable fighter model used during Space War I, the VF-1 Valkyrie.

Their most notable feature is the ability to transform—usually into a humanoid giant robot called Battroid and an in-between mode called GERWALK (Ground Effective Reinforcement of Winged Armament with Locomotive Knee-joint), in which the nose and wings have a pair of "chicken walker" legs extending underneath enabling VTOL, and two arms reaching forward from the sides.

Another prevalent (but not universal) design point is the use of a detachable gun pod instead of an internally mounted gun. This allows it to be used as a hand-held weapon in GERWALK and battroid modes. They usually also have one or more trainable head-mounted lasers in battroid mode, stowed internally or used as fixed armament in fighter and GERWALK modes.

In the original series, the reason behind the development of the variable fighters' Battroid mode was the discovery of the existence of the Zentradi race, giant humanoid aliens genetically engineered for military conquest. Although at the time the humans hadn't met any actual Zentradi, the discovery of the SDF-1 Macross and its accommodations for humanoid giants justified the development of a weapon that could enable mankind to fight the aliens on their own environment (Battroid mode), on the ground (Gerwalk mode), and the air (Fighter mode). Thus, research into alien Overtechnology culminated in the development of the variable fighters for the U.N. Spacy.

http://en.wikipedia.org/wiki/Variable_fighter