The Lockheed YO-3A Quiet Star; Charlie’s Silent Stalker

November 15, 2022

While the Vietnam War saw several very large conventional battles fought, probably the most iconic image of the war, and the experience of most of the belligerents, was of a grinding guerrilla conflict where the forces of the United States and their allies spent a frustrating amount of time trying to pin down their elusive enemy.

Patrols of the hinterland were the norm in an attempt to assert control and demonstrate to the local populace that the South Vietnamese government were indeed in control, not the Viet Cong guerrillas – nicknamed “Charlie” by their American opponents.

An important part of this policy was the garrisoning of fortified positions throughout contested areas. Indeed, this principle was recognised by the French – the former colonial rulers – and they had built small outposts all over the country which had been taken over by the South Vietnamese at independence and which they continued to use as part of their efforts to control the countryside.

Unfortunately for the Saigon government, the Viet Cong weren’t stupid and were generally careful to pick their targets wisely. To avoid the advantage that air power gave the South Vietnamese and their allies, particularly as the United States became more heavily involved in the conflict through the 1960’s, the communist forces became adept at using the night to launch their attacks and for moving their forces and supplies.

This represented a major issue for the United States. They generally had a massive firepower overmatch when they could pin down the enemy for an engagement, but operations at night significantly impacted that capability. Even if they could scramble aircraft to assist an outpost suffering night attack, these generally were armed helicopters which were the most useful for operating at night to provide close air support.

But helicopters are loud, and generally the VC would hear them coming and then melt away before the air support could get on station to attack. A similar problem occurred for night reconnaissance flights searching for communist insurgents or infiltrators, with the guerrillas often able evade spotters with good field craft.

All this meant that for the first half of the 1960s the night, as the American’s acknowledged, belonged to Charlie. And this, as can be imagined, was an unacceptable situation for the US military, who’s commitment to the conflict was rapidly ramping up.

The issue got to be such a concern that in 1966 the US Department of Defense tasked Lockheed to come up with a solution. They determined that the best remedy to the problem was to build an aircraft that was essentially silent to people on the ground whilst flying low enough to observe them.

Their first experiments took an existing sailplane glider – the Schweizer SGS 2-32 – and fitted it with a small Continental air-cooled engine that produced 57hp to provide it with a loitering capability. This, the QT-2, laid the way for further development of the idea into a two-seat aircraft with additional sensors and communications gear, the QT-2 PRIZE CREW.

This was fitted with a heavily muffled four-cylinder Continental engine that produced 100hp.

Two of these were sent to Vietnam for assessment and arrived in January 1968, just in time to get caught up in the surprise Tet Offensive launched by the Viet Cong and the North Vietnamese.

The aircraft proved extremely useful for conducting night reconnaissance and reporting enemy positions and movement during the hours of darkness, all achieved simply with an observer equipped with a standard four-power starlight scope. And, at a height of only one thousand feet (305m), they did this whilst remaining undetected by the troops on the ground they were observing.

The success of the QT-2 PRIZE CREW led to Lockheed creating another experiential model, the Q-Star, intended to develop more powerful and quieter engine installations. This work would go on to help create what is probably the quietest conventionally powered production service aircraft to ever fly.

The Lockheed YO-3A Quiet Star.

Though it still retained the basic glider airframe, it was substantially modified so that it appeared much more like a conventional light aircraft. Instead of the somewhat clunky looking propeller shaft over the cockpit of the earlier experimental types, the YO-3 had its engine mounted in a more standard location in the nose.

This, a six-cylinder Continental 360D, produced 210hp and drove a three-bladed propeller that gave the aircraft a top speed of 138 mph (222km/h). However, for minimal sound signature the Quiet Star would cruise at 70mph (113km/h) over the target zone, at which speed the aircraft had an endurance of six hours.

To further cut noise the engine compartment was surrounded with a fibreglass liner to absorb sound, and the propeller itself turned at a very slow rate of just 800 RPM, with drive via a belt-pulley rather than a mechanical geared system. Further, the exhaust was heavily muffled to both cut noise and flame signature.

The two-man crew sat in tandem, with the observer forward and the pilot rear, and they enjoyed excellent visibility through the huge canopy. However, the eyes of the aircraft were actually positioned underneath the cockpit, with the YO-3 having a custom-made night vision scope in a movable turret. This was supplemented with an active infra-red illuminator that could be used to both improve night vision or act as a spotlight for friendly forces equipped with passive infra-red equipment to highlight a target.

Consideration was given to equipping the aircraft with some armament, mainly air-droppable flechettes, but in the end it was acknowledged that the YO-3’s job was observation and communication, not attack and so it always operated unarmed.


The YO-3A’s completed their acceptance trials with the US Army in 1969 and in early 1970 nine were shipped to Vietnam for operational use.

Here they proved to be even better than expected. Mission profile was for the YO-3A to operate from 1,000 feet, from where its sophisticated night sights had little trouble spotting enemy troops. At that height the aircraft was essentially invisible and silent, especially amongst the background noise from the jungles over which the Quiet Star operated.

But in fact, pilots of the YO-3A reported that they could generally operate as low as 200 feet (61m) and normally remain undetected, so quiet was the aircraft.

Though only a tiny number, the YO-3’s provided sterling service directing friendly aircraft, artillery and ground forces onto enemy locations that they spotted. More to the point, though they were operating extremely close and right over the heads of the Viet Cong guerrillas, not a single aircraft was ever even hit by enemy fire, though three were lost in landing accidents.

All said, a pretty impressive achievement. Lockheed had delivered exactly what the customer required, and the YO-3 performed at least as well as had been hoped. Indeed, work was ongoing on an improved version that would have a laser designator for directing guided munitions.

But as with so many aircraft that have largely vanished into obscurity, the timing was bad. By 1970 the United States was already starting to rapidly draw down their troop levels in the country, pushing the “Vietnamisation” process as the US prepared to leave the conflict.

As a result, the YO-3’s only saw fourteen months of use before the six survivors were returned to the States. Some were used for a period by the Louisiana Department of Fish and Game for hunting poachers, and then by the FBI for covert surveillance and finally by NASA for recording the flight noise of other research aircraft.

But now all are retired and can be seen in various museums around the United States where I am sure their rather conventional appearance in amongst all the other old war birds can cause confusion amongst visitors who don’t appreciate what they are seeing – one of the most effective aircraft of their type ever built.


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