The Quiet Demise of the Cuties and the Yo-Yos

Day Stalkers A rare sunlit run for a YO-3A, whose mottled gray camo made it almost invisible at night. Doug E. Smith

View Photo Gallery

If Washington ran procurement programs the way it did the Lockheed YO-3A project, the words "billions" and "dollars" would never again have to be used by the Department of Defense in the same sentence.


But then I'll bet you've never heard of the YO-3A.


There’s an irony in that, I suppose, given that the so-called Yo-Yos and their immediate predecessors, the QT-2s, were the original stealth airplanes—ultraquiet, night-flying reconnaissance planes that served for a total of two covert years over Vietnam and Cambodia. “We never had an airplane come back from a mission without having [visual] contact with the enemy,” says Les Horn, then a young Navy officer who played a huge role in the development of what ultimately became an Army project. Their silent-stealth approach was an absolute success. “I don’t know of anybody who took a round,” adds George Walker, a YO-3A pilot who retired in 2000 as a brigadier general with 1,400 combat hours, 400 of them in Yo-Yos.


I met Horn, Walker and a number of other Night Stalkers, as they called themselves, last May at the first-ever big reunion of quiet-stealth people, in a hangar on Meacham Field, in Fort Worth, Texas. “Big” meant a couple dozen guys and their wives. A gathering of everybody who has ever flown, crewed, or worked on a Yo-Yo would require reservations for maybe 75.


The quiet-plane pilots and observers—the enlisted men who operated the reconnaissance gear—had never been recognized. Their missions and equipment were largely secret and, to many of their fellow combatants, a little goofy. Their airplanes were weird-looking, unarmed, had all the horsepower of a midsize Chevy, and were pretty much homemade. A few of the vets had convened in California a year earlier and decided it was time to come out of the woodwork.



The ex-Night Stalkers I met in Fort Worth looked to be in their 50s, although one—Wilbur Curtis, a Lockheed tech rep who had volunteered to go to Vietnam as a middle-aged man to help assemble the YO-3As when they came out of their shipping crates—was in his 80s. A couple of the others carried bags with airline-crew badges, but most of them probably hadn’t touched a flight control since they’d been discharged.


We got together for a day’s worth of technology and history presentations in a room furnished with folding steel chairs and a cranky PowerPoint projector perched on a stack of books. One wall was papered with a minutely detailed, ceiling-high map of Southeast Asia dotted with perhaps 75 little arrow-tabs marking places where North American Rockwell OV-10 Broncos had crashed—green for rescued crews, yellow for those taken prisoner, red for KIAs—for this was the club room of the national OV-10 Bronco Association.


Broncos had big guns and even bigger rockets and a pair of powerful turboprop engines and looked like a North Vietnamese Army truck driver’s nightmare. YO-3As, which sometimes worked in conjunction with the Broncos as their targeting aircraft, looked like skinny-winged, high-performance sailplanes with propellers. This is not surprising, since that’s basically what they were—highly modified Schweizer 2-32 gliders with six-cylinder Continental O-360 engines in the nose, the airframe totally remanufactured, strengthened, flush-riveted, and equipped for its new mission by Lockheed.


Les Horn had gone to Vietnam to see if it was possible to improve the effectiveness of the Navy’s riverine interdiction craft—including, incidentally, the kind of fast boats that John Kerry once conned. “They were jet-drive, pretty fast, but you could hear them coming from 15 klicks [kilometers] away,” Horn says. The Vietcong often melted into the villages and forests long before Kerry and his guys arrived.


Horn first thought of using observation balloons, but as he quickly realized, “They’re very quiet, but they’re also very hard to control.” He had a degree in physics and was also a Navy pilot, so he started analyzing what produced noise on an airplane—mainly the propeller, the engine exhaust, the mechanicals of the engine itself, surface cavities and protrusions, and form drag—and how to mask, attenuate, and dissipate it.


Oddly enough, a small group of engineers at Lockheed's Missiles and Space division had been thinking along the same lines, and in one of the ideal matchings of talent and task that the military occasionally achieves, Horn was plucked out of the paddies, flown back to California, and plugged into a Defense Advanced Research Projects Agency assignment at Lockheed.


Horn knew that the area to concentrate on was muffling midfrequency noise. Low-end noise was hard to hear until it was a lot louder than midrange noise, and we all know the truism that only dogs can hear very-high-frequency noise. Horn also found that just a small amount of background noise (insects, a little wind in the jungle trees at night) could mask the residual noise of a superquiet airplane. The key was to make the airplane superquiet by dampening that midfrequency noise.




Using Horn's research, Lockheed built an ungainly proof-of-concept vehicle called the QT-2, a Schweizer 2-32 with a little 100hp flat-four Continental O-200 engine in a soundproof box on top of the fuselage behind the pilot. QT supposedly stood for "Quiet Thruster," but the designation had to come from somebody familiar with the old-fashioned phrase "on the Q.T."

Everything was either off the shelf, handmade by Lockheed fabricators, or commissioned from individual outside craftsmen. The total budget for two QT-2s was $100,000, chump change in an industry that would soon become infamous for building $700 cargo-plane coffeemakers.


A prop shaft ran awkwardly above the cockpit, driven by rubber belts that both eliminated gear- and chain-drive noise and substantially reduced crankshaft-to-propeller rpms. It is, Horn points out, the "only full-size aircraft in the world driven by rubber bands." The shaft stretched to a four-blade wooden prop atop a big pylon on the nose of the airplane—a pylon that was, in effect, an extra vertical fin, which did little to enhance the handling qualities of the already awkward QTs.


The props (several were tried, including a six-blader) were handmade by a man named Ole Fahlin, whose reputation had been established not in the military-industrial complex but as a supplier of custom wood props to homebuilders and formula air racers. Fahlin would come out to the ramp between test flights of the original QT-2 and tune the prop by eye with a common wood rasp—take a little off here, reshape the blade there. “I don’t know how he did it,” Horn admits.