Warner Archives’ long-awaited DVD of Robert Altman’s rarely seen 1971 follow-up to his “MASH” breakthrough is an example of some of the best, but a lot more of the worst, of the great director’s filmmaking approach. Bespectacled Bud Cort (“Harold and Maude”) stars in the title role as a geeky but confident youth building a human-powered flying machine in a fallout shelter at the then new Houston Astrodome, looked over by a mysterious goddess-like earth mother/protector (Sally Kellerman). Meanwhile, assorted right-wingers in Brewster’s sphere are dying under never fully described or explained circumstances, including witchy Margaret Hamilton (“The Wizard of Oz”), complete with ruby slippers, and unrecognizable Stacey Keach under an enormous amount of age make-up as a greed-obsessed millionaire. A tough, plays-by-his-own rules San Francisco cop named Frank Shaft (Altman favorite Michael Murphy) is working the case, but the only thing connecting the deaths is the presence of bird feces on the corpses — which is, I guess, supposed to be hilarious and also meaningful. Meanwhile, the seemingly sex-negative Brewster bumps into a girl with a talent for wacky black comedy car chases (Houston-bred Shelley Duvall in her first film role). Altman discarded the original screenplay by Doran William Cannon, who wrote the infamous “Skidoo,” and so the writer can’t be blamed for the narration featuring Rene Auberjonois as a possibly half-bird ornithologist. It’s not all torture. The final few minutes find their way to a bit of actual movie poetry beneath the skylight of the Astrodome, but this bird doesn’t stay airborne for long.