Army Aviation

Flying on the QT

Historical Perspective / By Mr. Mark Albertson: 1961-1973: Much of the American effort in Vietnam was devoted to counterinsurgency. Daylight saw the comings and goings of American troops and aircraft; the night, though, belonged to Charlie.1 An aircraft known as the QT2 was an effort to take the night away from Charlie.


The QT2 and its successor, the YO-3A, were attempts to circumvent a dilemma in Vietnam; that of noisy aircraft which alerted the enemy to their presence. Many of the aircraft employed in the Second Indochina War2 – with exceptions – were of the high performance type. Historical parallel here was World War II. Army Ground Forces’ concern with the aerial direction of artillery fire led to skepticism towards the stable of Army Air Forces’ aircraft; that of those aircraft being too speedy to spend the time over target necessary to coordinate the adjustments required for American gunners – hence the advent of the L-4 Cub. Like concerns surfaced 25 years later in Vietnam. In response, an effort to employ aircraft inaudible to the human ear emerged; a form of stealth based on acoustics-deadening technology.

Seeking a Solution

DARPA3, the scientific and technical branch of the Defense Department, assigned the covert aircraft program to the Missiles & Space Division of Lockheed Aircraft Company. The program was sponsored by the Army, Navy and Marine Corps.4 The airframe selected was the Schweizer SGS 2-32 Sailplane; AKA the X-26A, a two-seat glider, used by the Navy to instruct novice pilots on the dangers of yaw and roll coupling. Lockheed obtained – through the good graces of the Office of the Chief of Naval Operations – two X-26s for the QT2 program.5 The power plant chosen was the Continental O-200, 4-cylinder, horizontally opposed, air-cooled engine.6 Excessive engine noise was suppressed with an off-the-shelf Buick automobile muffler. The propeller was a large, four-bladed type, fixed-pitch, of laminated wood. A ten foot shaft ran from the engine aft the cockpit, over the canopy to a pylon forward of the pilot. Use of a V-beltspeed reduction system saw that “when the engine was running at 2,400 RPM, our prop tips were spinning at approximately 0.2 mach.

h 1507 brinquelMAJ Andrew Brinquel, USA flew a six-hour mission in 1968, landing his X26B in dense fog with a dry tank./ PHOTO COURTESY OF MAJ ANDREW BRINGUEL“Our prop speed reduction system (six V-belts): Beyond slowing the prop and shaft, it decoupled and insulated them from engine torque-pulse vibrations. (Comments of our aircraft being ‘rubber band powered’ were almost true!)7” The standard crew compliment was two, pilot forward, observer rearward. For nocturnal operations, the observer utilized the Starlight Scope for light intensification. The wingspan was 57 feet; and fuselage 30 feet, 9 inches.
QT2 flying qualities and stealth capabilities were evaluated at Tracy Municipal Airport, northern San Joaquin County and at Hunter Liggett AAF in the Santa Lucia Mountains in Monterey County, California. Prize Crew training was conducted at the USNAAS Crows Landing OLF and at the NAS at Moffet Field, Sunnyvale, California8. In January 1968, the two QT-2PCs9 were shipped to Vietnam, followed by pilots and maintenance crews, to Soc Trang in the Mekong Delta area. Among the moonlight missions to be flown were observation, reconnaissance, and the direction of artillery fire.

An important aspect for this unconventional mission to become operational was to ascertain the proper acoustics in the field. To this end, MAJ Douglas Schneeman observed how the Prize Crew determined the correct altitude for the QT-2PC to remain imperceptible to the human ear. One evening, GIs were asked to lie face down on the airstrip. Repeated passes were made over the field, at various altitudes starting at 10,000 feet. With each pass, the altitude dropped 50 feet; until at 750 feet, the QT-2PC betrayed itself to those on the ground. Missions, then, were to be conducted at altitudes no lower than 800 feet; en route altitudes were generally 1,200 to 1,500 feet.

The QT-2PC in Action

One of the pilots assigned to the Prize Crew was a former Army infantry officer, MAJ Andrew Bringuel. Bringuel attended flight school at Fort Rucker, graduating as a fixed wing pilot. In Nov-ember 1965, he was off to Vietnam, flying Caribous. He accumulated 847 hours before being rotated Stateside, November 1966. He was assigned to Lockheed and the Quiet Plane Project in May 1967. He would go on to log 99 hours flying the X-26B in Vietnam in 1968.

One evening, Bringuel and his observer, Lieutenant Karl Kiefer, flew a mission for IV Corps along a tributary of the Song Be River. The pair orbited their assigned area, engaging targets, adjusting coordinates for sweating gunners. Meantime, fog rolled across the landscape, an impenetrable veil that socked in everything for miles. Bringuel had few passive navigation aids; all of which proved lacking. He contacted Saigon for a vector to the field; the QT-2PC proved invisible to the controllers. A local operator picked him up and, passed along a vector; but, a Ground Control Approach (GCA) was beyond the operator’s capability. Then the “Low Fuel Warning” indicator added to the unfolding drama for Bringuel’s mission had surpassed the normal four-hour limit.

QT-2 Experimental aircraft

Bringuel knew he was near the field… he just had to find it. Suddenly there was an opening in the clouds. He dived in. There, in the distance, blue lights… then white lights… buildings, then the runway. He lined up the field, touched down, braked, and then taxied to his hangar. Just in time, for he and Kiefer had been running on fumes. The mission was estimated to have lasted six hours. Apparently the crew chief had fueled the QT-2PC beyond the standard capacity of 24 gallons!
Following a six-month deployment, the X-26Bs were withdrawn from Vietnam. They would be followed by the more sophisticated Y0-3A. Despite its shortcomings – frailty of the aircraft, marginal performance and limitation of the Starlight Scope – the QT-2PC proved an important step towards, and forerunner of, today’s stealth aircraft.

Author’s Note: This article would have been impossible without the invaluable assistance of members of the Prize Crew: MAJ Andrew Bringuel and COL Douglas Schneeman, both U.S. Army Retired; Mr. Dale Ross Stith, Lockheed (Retired); and CAPT Les Horn, U.S. Navy Retired.

1. Refers to the Viet Cong. Known to GIs as “Victor Charlie,” later shortened to “Charlie.”
2. The First Indochina War, 1946-1954, featured the fruitless French effort to reestablish their colonial agenda in Vietnam.
3. Defense Advanced Research Products Agency.
4. The Air Force was dedicated to the Pave Eagle (QU-22) aircraft for nocturnal surveillance of the Ho Chi Minh Trail.
5. “QT” for Quiet Thruster and “2” for two-seater.
6. To the Navy, the powered 2-32 glider was the X-26A; the QT2 became the X-26B.
7. “Taking the Night Away From Charlie,” Operation Prize Crew (QT-2PC).
8. Pilots, mechanics and other such personnel attached to the program were referred to by the Army codename, “Prize Crew.”
9. Planes were re-designated as QT-2PC when they were readied for night operations prior to transshipment to Vietnam.

Mark Albertson is an award winning historian and contributing editor to ARMY AVIATION magazine.

Sketch of QT2, featuring the V-Belt Speed Reduction System.