The Pentagon's Flying Saucer Problem
The weapon system that could have made the enemy die laughing
- By Graham Chandler
- Air & Space magazine, May 2003
U.S. Army Transportation Museum, Fort Eustis, Virginia
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But the engineers predicted that as the Avrocar transitioned off its cushy ground bubble and picked up speed, it would be unstable in pitch. The pilot would be continually jockeying the stick back and forth to prevent it from stalling nose-up or pitching nose-down into the ground. In most conventional airplanes, the horizontal stabilizer looks after that. The Avrocar had no tail, so the team designed an ingenious mechanical connection that automatically deflected the control vanes up or down, simulating the effect of a tail. Slight horizontal motions in the spinning rotor would automatically control those vanes, so the pilot could occupy himself watching for the enemy.
So far, so good. After the rollout fanfare, Avrocar No. 1 was mounted in a test rig to put theory to practice. Engines were fired up. But as the throttles were advanced to full power, elation fizzled. The J69s’ combined thrust, 2,700-plus pounds of it, wasn’t producing the effect predicted.
The engineers deduced the problem: The air sucked in from the rotor was cold and the jet pipe exhaust was hot, and when the two were mixed, the resulting flow was turbulent and would not stick to the duct’s inside walls. The result: 30 percent of the thrust was lost.
The team tried various tricks, but nothing budged the Avrocar out of ground effect. Though the Army had firmly required that achievement, the company “decided to carry on and fly the Avrocar at a reduced thrust level in the ground cushion, and modify the duct at a later date to pick up the missing thrust,” Frost later wrote.
The team members pressed on toward a first flight. At least they’d have some kind of milestone to crow about. Avrocar No. 2 was chosen for the attempt. To prevent another surprise, the team used three stout cables to tether the saucer to within a few feet of the ground.
In September 1959, company test pilot “Spud” Potocki climbed in and lifted off for the first time. He spent the next six weeks feeling the Avrocar out on its leashes. By early December he was ready to throw off the tethers.
From a hover, he eased the stick forward. Canopy off (in case a quick exit was called for) and engines screaming, the Avrocar skittered over the tarmac, blasting dust and debris, rocking and dipping like a Frisbee in slow motion. It was an amusing spectacle, but not terribly impressive. Potocki could not get the saucer to exceed 30 mph, or to rise up more than three feet into the air and off its ground cushion.
The team faced a Catch-22. Avro could ask for more funds to cover a pricy redesign of the ducts, which might help the saucer lift out of the ground effect. But the effort would be wasted if the company couldn’t demonstrate stability. And how could the engineers determine stability if they couldn’t get the vehicle out of ground effect?