The Top Secret Tri-Service Operational Evaluation of the experimental Lockheed Quiet Aircraft in Southeast Asia combat from in Jan-March and July-Dec 1968.  The success of the QT-2PC paved the way for the development of the YO-3A. 

The last of the Vietnam Aviation Aircraft stories to be told.
Taking the Night Away From Charlie.

A paper (A Spoken Version) delivered to the 6th Triennial Vietnam Symposium a Texas Tech University in Lubbock, TX on 3/15/08 
Unable to upload the images to this site, I've edited the text, as needed. A full version will be submitted to our archives.
Author: Dale Ross Stith

Late one evening, Col. Walts told me that we might be attacked later that night.
Some believed that the attack was ON and others thought NOT.
Of those that believed it was so; some thought it would be serious and others thought it would be trivial.
It was January 30TH 1968: The start of the TET Offensive!
We had just arrived in ”Four Corps” South Vietnam for the Prize Crew Operational Evaluation.
Our Prize Crew Aircraft: It’s also known as QT-2, QT-2PC, QT-2PCII, and lastly as X-26B.
It’s a Schweizer 2-32 Glider Airframe equipped with a propulsion system:
- A muffled piston engine mounted behind the cockpit in the fuselage over the C.G. driving a large, slow-turning, propeller via a 10 ft. long overhead shaft.
- A flush-riveted aluminum semi-monococque fuselage with tandem aircrew and dual controls
- 57 ft. wingspan and unitized stabilator.
- Viewing Ports for the Tactical Observers.
- Minimum Comm/Nav Avionics, no armor, weapons, or redundant systems.
The Prize Crew Aircraft was designed for covert 4-hour night missions at 70 Knots and 1000 ft AGL.
How Quiet???
Simple statements are incomplete and somewhat meaningless without a full description of the aircraft noise, the ambient environment, and other factors; including human hearing.
So; I’ll just say, that if we were all out on the plains tonight and our Quiet Aircraft flew directly overhead 1000 ft above us in a starry sky, but not in front of the moon at the moment you happened to be looking in that direction; you wouldn’t know it! 
If you heard anything at all, you wouldn’t recognize it as an airplane.
The primary sources of general aircraft noise are:
Number 1. The propeller
We used a very large four-blade fixed-pitch design and kept the tip speed far below Mach by using a 3:1 reduction system.
So, when the engine was running at 2400 RPM, our prop tips were spinning at approximately 0.2 Mach.

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!)
Number 2.

The engine exhaust: 
So, we used an off-the-shelf Buick Automobile muffler.
It reduced our 100 Horse Power Continental O-200 engine exhaust noise by approximately 80%.
Number 3.

The airframe:
So, we used a lightweight, very clean, low-drag, aerodynamically efficient glider airframe
and high L/D High-Aspect-Ratio-Wings. 
Our sensors were First Generation Starlight Scopes and “MKVIII Eyeballs”:
A 4 Power 10 Degree Field-Of-View   (FOV), a 2 Power 20 or 40 Degree FOV, a 1.7 Power 30 Degree FOV,  and a 1.5 Power Aeroscope. 
Note:  The Aeroscope is Serial Number 1
Who we were and why we were there:
“We” were a Joint-Service military team and I was one of a few civilian Lockheed Tech Reps assigned to the team.
Our job was to evaluate the Quiet Aircraft concept in a tactical operational environment.
 I represent the non-profit Quiet Aircraft Association.
Our archives include hundreds of images and aural and video records of our project. Images of our aircraft in daylight flight are rare. Some of our images were exposed in twilight, but recently enhanced with computers and software.  We have very few night images.
I will show some images of our activities, but will leave most of the coverage of TET and Vietnam to other presenters.
I’ll use lots of acronyms to be brief and hope that they are familiar to you
I’ll also place a full version of this paper (with definitions to break the “tech speak” code) and other material in the Vietnam Center.  I’ll also place a version on one of our websites: prizecrew.org, quietaircraft.org, or YO-3A.com.

Vietnam was mostly a guerrilla war. So, fighting it required different equipment and strategies than previous conflicts:
Our enemies mostly operated and moved under the cover of darkness, then disappeared into the environment by day.
Our U.S. forces, however, mostly operated by day and were essentially “blind” at night.
The aural and visual signatures of our conventional aircraft exceeded the detection and recognition range of our sensors.
Typically, enemy combatants heard and/or saw our approaching forces and sought cover before we were able to detect them, or get close enough to take action against them. 
In 1965, DoD (Dr. John S. Foster) initiated development of what became the world’s first “stealth” aircraft
DDR&E asked the technical community for assistance in fighting the Vietnam War and designated DARPA as the technical lead. DARPA Project Agile (RACIC) then established the parameters of a covert airborne reconnaissance platform in response to an emergent military requirement.
In 1967, two independent activities, on opposite sides of our globe, converged at Lockheed Missiles and Space Co. (or Lockheed) to produce the QT-2 Aircraft. (“QT” for Quiet Thruster)
Number 1.

Lockheed (Advanced Concepts: Galbraith, Baumann, Schnebly, Hall, et al) studied Lighter-Than-Air Ships, balloons, etc.; then conceived a quiet aircraft using a single-seat glider airframe powered by a muffled automotive engine and a large slow turning propeller.
The concept was proposed to DARPA, but rejected in favor of a two-seat aircraft with a certified aero engine.
Lockheed then conceived and proposed the QT-2 Aircraft.
Number 2.
A Naval Officer (then Lt. Leslie J. Horn), evaluating Night Vision Devices for Riverine COIN warfare in the “Brown Water Navy”, suffered frequent random fire and occasional ambushes by Viet Cong forces hiding in vegetation that lined the waterways they patrolled.
He also observed the enemy fade away or flee at the sound of approaching naval units.
A Fleet Pilot and a scientist, he reasoned that his Night Vision Devices would be highly effective against this threat, if mounted in a covert airborne platform.
He, thus, conceived an essentially identical quiet aircraft.
He wrote a TSOR and routed it through his COC to NRL, who proposed it to DARPA.
The Lockheed and Navy proposals arrived at DARPA within months of each other: A rare and serendipitous confluence of an urgent military requirement and an independently formulated   “near-perfect” solution!
In April 1967, Lockheed was awarded a contract for the QT-2 Program:
Build and demonstrate two low-noise experimental aircraft within six-months.

The program was sponsored by the (Ft. Eustis based) Army Transportation Corps and was to be evaluated by (the Hunter-Liggett Military Reservation based) CDEC.

Lockheed set up a small covert development shop in their Executive Aircraft Hangar at the San Jose Municipal Airport using  “Skonk-Works, North Rules”
(with respect to Kelly Johnson):
Limited Access
Commercial parts and local vendors and shops allowed.
Many usual DoD & Lockheed requirements waived.
Minimum inspection, documentation, and reporting (everything!).
A very short Chain Of Command and direct government-contractor contact.
And most important, but often overlooked – trust.
A fictitious: “San Jose Geophysical” name was used and our phone was answered with “Stan’s Cleaning and Pressing”.
Lt. Horn was interviewed by Lockheed, DARPA, and NRL.  Then, with the recommendation of DARPA's Director of COIN Warfare (Leonard Sullivan), and with the concurrence of OPNAV and COMNAVFORV;  he was assigned to DARPA as Quiet Aircraft Project Officer and sent to San Jose to participate in the development and tests of the QT-2 Aircraft.
Two Schweizer 2-32 Glider Airframes were diverted from an existing Navy X-26 Purchase Order and expedited, with the help of CNO, to the QT-2 Program.
Not yet built, they were fabricated with thicker wing skins and spars, for the anticipated extra weight of the propulsion system, and with special attention to minimize surface ‘waviness.’
The glider airframes were then modified in our San Jose shop: The propulsion and other systems were designed, fabricated, and installed.
The first QT-2 was flown on August 15, 1967 for basic aero tests.
The second QT-2 was completed shortly thereafter and flown in an acoustic demonstration and fly-off competition with other modified aircraft .
The trials demonstrated that the QT-2 was markedly quieter than any other aircraft under consideration for the role.
During this time, tactical reverses near the DMZ confirmed the urgent need for a covert airborne reconnaissance platform.
The QT-2 was identified as a candidate to satisfy the requirement, if properly modified.
So, a decision was made to convert the experimental civilian aircraft into tactical military aircraft to satisfy the “DMZ” requirement and, further, to evaluate them in an operational environment.
The Prize Crew OpEval Plan included:.
Addition of IFR instrumentation, Comm/Nav Avionics, viewing ports for the Tactical Observers, and paint for low visibility night operations.
Training of the aircrews and deployment of the aircraft to Vietnam within 90 days.
Conduction of nightly surveillance missions in various Vietnam environments.
Evaluation of the quiet aircraft concept and, specifically, the Prize Crew Aircraft in a tactical operational environment.  
Lockheed was awarded a contract to implement the plan, so the aircraft were modified then renamed Prize Crew QT-2PCs (#1 and #2). “PC” for Prize Crew.
The aircrews were trained; first in gliders, then in daylight in the QT-2PCs at NALF Crows Landing in the San Joaquin Valley, and at night at NAS Moffett Field in the San Francisco Bay Area. 

The QT-2PCs were transported to Vietnam in Air Force MAC and TAC C-130s. 
The Prize Crew Aircraft arrived at Soc Trang on January 22.
Originally destined for Hue in I-Corps, they were re-routed to Soc Trang because of unfavorable monsoon weather “up north,” and  the growing need of dedicated aerial surveillance in support of IV Corps tactical operations

Soc Trang Army Airfield:
3500’ Long

130’ Wide
Near Sea Level
In the Mekong Delta Near Bassac R. and the South China Sea

The Prize Crew Aircraft  were off-loaded from the from the C-130, uncrated, reassembled, ground tested, and operationally certified by January 24.

We had Vietnamese Nationals working on the field and didn’t want them to see the aircraft. So we rarely brought them out in daylight and cleared the area before moving them out of the hanger.

The Prize Crew OpEvaL.
The goals of the Prize Crew Operational Evaluation (OpEval) were to determine Quiet Aircraft:
Appropriate missions and roles
Capabilities and limitations and, if the results justified further development of the Quiet Aircraft,
Define its (Future Quiet Aircraft) optimum configuration.
The plan also included additional objectives beyond the scope of this paper: Tactics, organizational structures, resources, and support for future quiet aircraft.
The Prize Crew OpEval had an unusual – and probably unique – Chain Of Command in Vietnam.
It was assigned to MACV (Fixed Wing Aviation at Nha Be); although, actual operational control was exercised by the Prize Crew Detachment OIC at Soc Trang. 
Administrative support for military personnel assigned to the project was provided by their respective service commands: COMNAVFORV, COMUSARV, and the 7th Air Force. 
Technical support was provided ACTIV and NRDUV; primarily for sensors, instrumentation, and test equipment.
Support for test design and interpretation of test results was provided by MACSA.
Two four-hour missions per night per aircraft were planned within a 70-mile radius of Soc Trang, with a crew change at turn-around.
On-station times were approximately half of the mission time and a one-hour a fuel reserve allowed for unplanned events.

The Prize Crew Operating Area extended from the Parrot’s Beak Area, West of Saigon, to the Southern tip of Ca Mau Peninsula: Three Sisters, U Minh Forest, Plain of Reeds, the Mekong Delta, and Rung Sat Special Zone 
The aircrews were briefed and debriefed in our "
Ops Shack": Assignments, Intel, etc.
QT-2PC Crew Stations:
Owing to weight and space limitations, our aircrews were initially limited to max height of 69” and max weight of 165 lbs.
Little room was available to maneuver the Starlight Scope. Map reading and stowage (more like “origami”) was difficult.
The Prize Crew Aircraft had no ownership ID “Markings”. Only a “1” or ”2” in outline on the empennage.
Flight operations, conducted only at night to preserve the covert nature of the mission, were coordinated with other military units and integrated into their operations on a need-to-know basis:
Call Signs were NIGHTHAWK or HAWK “1” or “2”, but no other information about aircraft type, location, or capabilities was provided.
This was a problem communicating with other “friendlies”. An example:
Prize  Crew observed a group of sappers digging near a bridge between a canal and road and called for an attack on them.
It was known that enemy interdiction teams were used to ambush, destroy infrastructure, limit usage, and collect “taxes”
A Seawolf Gunship responded and, as it approached along the canal, was told that the sappers were just beyond the bridge between the canal and the road .
Prize Crew was asked for its identity, location, etc; but could not answer, as it was operating “lights off” in covert mode.
The gunship made a run on the target, but did not attack. As it flew over the target area – an explosive charge “blew -up”!
The gunship made a 360 for a “gun  run” and exclaimed “I don't care who or where you are, but the next time you ask me to shoot – I'm shootin”!!!
Aircraft exterior lights were used only when operating in the Soc Trang control zone or when transiting in a non-operational t at higher altitude.

Mission Roles:
Hot Contact, Pre- and Post- Strike intelligence. 
Linear surveillance along roads, routes, trails, tree lines and waterways 
Area and perimeter searches around bases, camps, and outposts for defense and location of enemy attack positions.
Artillery support: Call of shot-fall and gunfire direction.
Pre-insertion reconnaissance for Special Forces and SEALs. 
Surveillance of traffic for Riverine and Coastal Naval Force Support.
Any vehicle or personnel movement during curfew  periods  was considered significant and assumed to be enemy.
Mission operating areas included all typical RVN environments: Mountainous, heavily vegetated, dry and inundated savanna, paddies, and other cultivated biomes. Canals, rivers, waterways, coastlines, surf zones, bays, tidal flats, marshes, and mangrove swamps.
Northeast monsoon weather prevailed throughout the evaluation period: Light to moderate monsoon winds, rain, but generally clear skies with some morning fog.
Ambient Noise Levels between 20 Hz and 4000 Hz were 30 to 60 dbA in Delta Terrestrial settings and at 48 to 70 dbA in Delta Riverine settings.
OpEval Results:
Mission effectiveness was gauged from analysis of "after action" reports, frequency and strength of enemy contacts, and improved utilization of friendly forces and assets.
A total of 263 sightings during 591 hours of night flight time were made from 24 January to 24 March of the OpEval.
Note: Prize Crew II continued from April to December period of the OpEval is not yet available.  
Sightings:                                                                                              Sightings/
Mission Role               
            % Total Flight Time      % Sightings       Flight Hour      
River/Canal:                                          35                          70                     0.9
Route:                                                    15                          20                     0.62
Area, Coastal, Perimeter & Strike       27.5                       12.5                  0.26
Enroute/Training                                   22.5                       ---                      ---
Average                                                 100                         ---                     0.49
More targets were detected during River, Canal, and Route linear surveillance than during other missions.
Motor vehicles, watercraft, and vehicular traffic were the most frequently detected objects.
The Prize Crew Aircraft was seldom detected when operating above 1000 ft AGL, but was fired upon (with automatic weapons), possibly because its long wings made it appear to be closer than it was.
In every case, it was after the Prize Crew Aircraft repeated passes in front of the moon.
Evasive or hostile actions occurred 14 times in 132 sorties (mostly due to visual detection). So, the operating altitude was raised to 1500 ft AGL, limiting the usefulness of the Starlight Scope to a small degree.
Capabilities Demonstrated
The QT-2PC was not completely quiet, but the noises that it made would not normally be associated with an aircraft, and ambient masking noises and limited human hearing made the aircraft difficult to detect.
Significant targets were detected, tracked, and reported. Hot targets were found in all mission areas.
Limiting Factors:
The limiting factors were the aircraft, avionics, and the sensor.
Immediate: Inspect, refurbish, upgrade the QT-2PC in CONUS and return them to RVN to continue the OpEval (Prize CrewII). 
Procure thirteen additional (upgraded) QT-2PCs: Ten for the Army (Some for each RVN CTZ) and three for the Navy.
Initiate a study for an improved quiet aircraft. To include:
Better aero performance:
- More engine power with a six-blade/variable pitch more efficient, quieter propeller.
- A less visible exterior: Camouflaged pattern, lighter shade, or mottled paint.
- Conventional landing gear (retractable preferred).
- A better sensor: Multiple FOVs, stabilized 360 Degree Azimuth and horizontal to nadir elevation with target marking (Laser Target Designator).
- Better aircrew viewing angles: Bubble canopy with Tactical Observer in front.
The recommendations were fulfilled with YO-3As in 1969
Perfect? No, we needed more of everything: Time, people, money, aircraft, etc.
We designed, built and flew two experimental QT-2 Aircraft for $500K in six months, upgraded them to QT-2PCs for $100K in three months, and operated them (through the TET Offensive) with very high availability
I suspect that our aircrews were told “they won't hear you or see you, so don't worry - they won't shoot you! Whatever, They did it.
We were pioneers and all of our crews deserve medals.
Our OpEval was the first combat use of night vision devices in an aircraft.
·  The X-26
Program is aviation history’s longest “X” Program
The QT-2PCs were the first military aircraft to survive a hostile environment by means of “low observables” – now called “Stealth”!  
We took the night away from Charlie!










 Free Web Counter

See quietaircraft.org for Quiet Aircraft Assn, Inc 2003, 2004 & 2005 Reunions