The United States Air Force, focused toward nuclear weapons and delivery of such munitions against static strategic targets had spent little effort in expanding its tactical capabilities since the end of the World War II. Operation Shed Light sought to rectify this by bringing together improved tactics and technology. The programs were subsequently centered on improved communication and navigation aids for all-weather and night flying, sensor equipment for seeing through clouds, foliage, and darkness, improved equipment and methods for target marking and battlefield illumination, and aircraft and tactics to utilize these developments. In the end, few of the programs would yield applicable results and most of the aircraft developed under its umbrella would largely fall into obscurity. The most applicable developments were those that could be mainstreamed such as the work done on navigation and

Origins

The United States Air Force had largely redirected its efforts to the matter of strategic deterrence in the period between the Korean War and deployment to southeast Asia. As a result it had few serious capabilities for the plethora of conventional missions that became readily apparent with the expanding US commitment to southeast Asia. Dedicated attack aircraft were virtually nonexistent, with the exception of the Korean War era A-1 Skyraider. The US Navy was still using the type at the time, and the US Air Force had itself been long interested in the type, with this further reinforced as a result of its advisory role in South Vietnam. The US supported Vietnam Air Force was in fact using it as their primary aircraft by 1965. These aircraft had directly replaced aging F8F Bearcats in 1962 and the decision was made in 1964 to transition to the type from the then standard T-28 Trojans.

As a result of the orientation toward nuclear war, tactical air strikes were flown almost exclusively by the US Air Force between 1964 and 1966 using a variety of fighter bombers intended initially for the delivery of small strategic and tactical nuclear weapons. These types included the F-100 Super Sabre, F-4 Phantom II, and even the F-104 Starfighter. The F-100 had two fighter bomber variants in service at the time, the F-100C and F-100D, both of which were capable of carrying a nuclear store, and only the latter of which was primarily for use as a strike aircraft and not a fighter. The F-100C had largely been passed to the United States Air National Guard and by 1965 less than two hundred of the aircraft were capable of using cluster bombs or even the largely standard AIM-9 Sidewinder air-to-air missile. The F-104C, a fighter bomber version of another fighter, though capable of utilizing conventional air-to-ground stores, was intended as a nuclear weapon delivery platform. Only the F-4C and F-4D were available as a true multirole aircraft, and the F-4C had still been used firstly as a fighter when deployed to the theater. The only other major non-fighter type in use early on in the conflict was the B-57 Canberra. Strikes in Laos were even conducted for a time using the F-102 Delta Dagger, modified with infrared sensors, and using its internal rocket armament. These strikes proved largely fruitless and were quickly discontinued.

Realizing the need for more dedicated attack aircraft the Air Force combed its inventory and looked to invest in new types. It found itself with an odd selection of obsolete, new, and experimental aircraft, and grasped for immediate solutions. To try and coordinate this effort, a task force was established by Lt. General James Ferguson, then Deputy Chief of Staff for Research and Development. Dubbed Operation Shed Light, it began on 7 February 1966 as a means of coordinating a wide variety of technological and other projects and programs that were being pursued in order to improve the United State Air Force’s night fighting capabilities. Outlined in the Task Force’s charter as of April were the following:

“1. Identify current equipment, techniques, and procedures being used by the USAF in Southeast Asia.

2. Identify planned modifications and new equipment being developed for Southeast Asia.

3. Survey exploratory, advanced development, and operational support projects having a potential application to the problem, indicating current programs or schedules.

4. Identify voids in our capabilities or efforts.

5. Recommend courses of action to improve and/or provide new attack capability in 1966, 1967, and the longer term.”

In all, the Shed Light Task Force identified nine new weapon systems and seventy-seven research and development “tasks” in the first five months of operation. Over the next 5-10 years it hoped to have a fully functional "self-contained night attack aircraft," a single type that would meet the operational need and would be functionally useful in other similar situations.

Initial programs

Shed Light’s initial programs were broken down into a number of categories, the most important being communication and navigation systems, sensors, and illumination and target marking equipment. Also detailed were proposed aircraft modifications and tactics.

Communication and navigation

Issues of communication and navigation were identified under Shed Light. That air strikes could not be called in effectively and/or guided to the target reduced the effectiveness of air power overall. A variety of communication system improvements and navigational aids, including improvements to the Long-Range Navigation (LORAN) system (specifically LORAN-D) were incorporated into the Shed Light mission.

Sensors

^{The sensors to be developed under Shed Light were broken into three categories, Low Light Level TV (LLLTV), Forward Looking Infrared (FLIR), and Forward Looking Radar (FLR).}

^{Two LLLTV systems were in development initially. Both were podded, designed to be added to aircraft already in USAF inventory. The first, produced by Dalmo-Victor under Project 1533, was LLLTV only, but had provision for a laser range finder. It was intended for the A-1E Skyraider. The second, produced by Westinghouse under Project 698DF, contained both the LLLTV and a laser ranger finder. It was intended for either the A-1E or B-57 Canberra series. The second unit would eventually be fitted to the B-57B. The two programs were named Projects Tropic Moon I and II respectively. The Tropic Moon I system was essentially obsolete before it was deployed, and tests quickly confirmed this. Only 4 A-1Es were so equipped. The results from the Tropic Moon II B-57Bs were almost as discouraging, with 456 trucks detected on 182 sorties, for only 39 confirmed kills. Both systems were removed from the theatre by the end of 1968.}

^{"A prototype FLIR unit had been tested under Project Red Sea in a DC-3 at Eglin AFB, and later in an AC-47 in South Vietnam in September of 1965. Using technology developed from those tests, Project Lonesome Tiger was initiated, testing a FLIR unit on two B-26 Invader aircraft. Climate was found to have serious effects on the units, especially humidity, and this fit was not to be put into widespread use. Improvised mounting of “starlight scope[s]” in the bomb bay of the B-26 is also mentioned in oral history reports, and this fit was found to be largely impractical."}

^{Illumination equipment and target marking}

^{Battlefield illumination was of key importance within the original Shed Light programs. The dominant aerial flare at the time was the Mk 24 Mod 0, developed by the US Navy. Reliability of the units, however, were in question, as was availability. Perhaps of greater concern was existing test data in 1966 that suggested pilot disorientation and flare placement were serious issues. Project Night Owl, conducted in 1954, testing flares dropped from F-86 Sabre aircraft, led to twenty-five percent of pilots reporting experiencing some level of vertigo. Ironically, initial studies showed that in correcting this problem, issues of insufficient illumination were experienced.}

^{A new flare, designated MLU-32/B99, also referred to as Briteye, was put into development. The new flare burned at 5 million candle power for over five minutes and produced a signal that could be heard by pilots indicating when it was about to burn out. Additionally, the Navy’s Mk 33 Mod 0 flare warhead for the 5” Mk 16 “Zuni” rocket motor was tested under Shed Light task Force Projected delays in the procurement of the MLU-32/B99 led to a proposal to test the Swedish Lepus flare as an interim measure. The Lepus flare was tested, but found to be inferior to the MLU-32/B99.}

^{The issues surrounding flares led to exploration of other methods of battlefield illumination. The Battlefield Illumination Airborne System or BIAS, employed two banks of Xenon ARC lamps (28 total) fitted to a modified C-123B aircraft. A cooling system was installed on the left side of the aircraft to help dissipate the heat generated. The system was deployed to Vietnam, but it was found that the lamps provided a perfect target for enemy gunners and the system was discontinued. Initially it had been proposed that a similar system be installed on the more capable C-130, but the experience during the operational trials brought the whole program to a halt.}

^{More unorthodox methods were also explored. Astrosystems International developed a so-called “Quartz Chamber” which burned pure oxygen and aircraft fuel, converting the chemical energy into light. The system was planned to be evaluated within a year, and installed in a similar arrangement to the more conventional BIAS. A plan, codenamed Moonshine, was also put forward. Moonshine was to be a joint effort with NASA to determine the feasibility of a geosynchronous satellite that could in project light directly down on any desired location.}

^{Ground target marking, which was a key tactic for day time strikes, was investigated. Project 2531 was to investigate target marking munitions, and looked into warheads for the Mk 40 2.75” rocket motor, using a variety of chemiluminescent materials. These were to be loaded with compounds developed under the US Navy's Target Illumination and Recovery Aid (TIARA) program. Initially they used modified M151 high-explosive warheads, but found the amount of compound that could be contained provided poor results. The Shed Light Task Force noted that a lighter case for these compounds was in development. A combination of red phosphorus and a flare was investigated in an attempt to provide a system that could be used at night or during the day.}

^{Aircraft and tactics}

^{The key aircraft intended to be developed under Shed Light was to be a “Self Contained Night Attack” aircraft or SCNA. The SCNA would have “the necessary night sensors and weapon delivery capability to find and strike targets at night one the first pass without the use of visible artificial illumination.”}

^{However, to provide an interim capability, the idea of using a “Hunter-Killer” concept using aircraft capable of spotting targets at night and more or less unmodified conventional strike aircraft was proposed. This method had many identified disadvantages, including the need for specialized aircraft and capability differences between the hunter and the killer that might affect their combined operation. The need for specialized aircraft was further exposed by the fact that only three aircraft at all suitable for the hunter role were available to the US military in southeast Asia as of 1966. These included the Army’s OV-1B Mohawk, and the USAF’s RF-4C Phantom II and RB-57E Canberra aircraft. There were only two RB-57E aircraft in country at the time, under a special reconnaissance project codenamed Patricia Lynn, and the aircraft were essentially experimental. They also featured Reconofax VI FLIR units, which was an older technology than those being developed under Shed Light. The RF-4C had the benefit of being of a similar capability to strike aircraft at the time, and a modified hunter version, given a designation RF-4C(H) was to be developed, replacing the camera equipment with LLLTV, FLIR, and Side-Looking Radar (SLAR) units.}

^{A three-phase program had been outlined as early as 1966 for development of the SCNA. The first would be a slower bomber or cargo aircraft, followed, by a jet aircraft of some type. The F-111 was originally slated to become the key SCNA aircraft. It was ultimately hoped it would incorporate the final versions of all three types of sensors (LLLTV, FLIR, and FLR) developed under the program. In the initial study, an “RF-111” was also supposed to be available in the 3-7 year time frame for use in the hunter-killer pairing. This time frame led the initial study report to propose using the OV-10 Bronco aircraft in the interim measure, but decided against it because of the inability of the OV-10 to carry all the desired sensor equipment. As it turned out that while the RF-111A did enter testing in December 1967, it was not easily convertible to and from the existing F-111A configuration. The Air Force looked for alternatives, but the revised RF-111D program was terminated because of a funding shortage in September 1969 and the RF-111A program was cut for good by March 1970.}

^{With the decision not to use the OV-10 and the desire for an immediate capability, the USAF decided to investigate using the S-2 Tracker aircraft. The proposed aircraft would incorporate the three main sensors under development in a revised aircraft that provided operators for all major systems. The S-2’s built-in search light was to be slaved to the LLLTV, crew protection would be provided, and the armament system would be primarily 10 SUU-24/A munitions dispensers in a revised bomb bay. Six wing hard points would be available for additional conventional munitions including bombs, rockets, cluster munitions and dispensers, and gun pods. Interestingly enough, the program package documentation suggests that the “XM-9” would be the primary under-wing store. The XM9 designation is the US Army designation for the SUU-7/A low-drag dispenser pod modified for use on the UH-1B/C Iroquois helicopter. The two planned pre-production aircraft were to be designated YAS-2D, while the production aircraft would have been AS-2D. Difficulties in funding, getting the aircraft from the US Navy, and delays in completing the modifications led the USAF to scrap the S-2 based SCNA in January 1968.}

^{The F-111 would have mixed record in southeast Asia at best, and operations were suspended more than once following its eventual deployment to first for operational evaluation in 1968 under Operation Combat Lancer. The aircraft were returned to the United States in November 1968 after three of the six aircraft had been lost in combat. Actual combat deployment to the theatre came in 1972. The aircraft suffered a number of losses due to non-combat reasons in addition to losses to ground fire. By the time of its deployment to theatre, it was no longer earmarked for conversion into the SCNA role.}