In 1968, the US Joint Chiefs of Staff needed an answer. The US Air Force then operated two vastly different types of aircraft to attack North Vietnamese trucks moving reinforcements and supplies down the Ho Chi Minh Trail.

The Joint Chiefs wanted to know how well each type of aircraft –the fast, modern jets with high wing loadings and slow propeller-driven fighters with lightly loaded wings – performed that mission.

So the study evaluated the record of the McDonnell F-4 Phantom, the USAF's most versatile and sophisticated fighter, on day and night attacks against North Vietnamese trucks over a 10-month period in 1967. Then the Joint Chiefs compared that with the record of the World War II-era Douglas A-1 Skyraider, which was performing the same function.

The results of that study still resonate in USAF budget debates 50 years later. According to a Joint Chiefs memorandum dated 28 February 1968, the World War II-era A-1 proved nine times more effective at destroying moving trucks on the Ho Chi Minh Trail than fast-moving F-4s. That single metric seemed to make the Skyraider a no-brainer for the light attack role, except for another, more disturbing finding in the report. The vulnerable A-1 suffered five times as many losses as the F-4 while performing the same mission.

A new USAF demonstration known as Combat Dragon III is under way this month at Holloman AFB, New Mexico. Three aircraft – Embraer’s A-29 Super Tucano, Textron AirLand’s Scorpion and Beechcraft’s AT-6 Wolverine – will be evaluated in the light air support role, a broadly defined mission that includes light attack, armed reconnaissance and pilot training.

The USAF has not disclosed details of the evaluation criteria, but it is likely to compare how two turboprops – the A-29 and AT-6 – and the Scorpion light twinjet perform that mission compared with the survivability, cost and effectiveness of using existing aircraft, such as Boeing F-15s and Lockheed Martin F-16s and F-35s.

In 1968, the memo drafted by the Joint Chiefs ultimately recommended a mixed fleet for the light attack mission, with F-4s used to attack vehicles in defended airspace and A-1s reserved for undefended stretches of the Ho Chi Minh Trail in Laos.

The USAF is required to submit a report on the results of Combat Dragon III to Congress by December, but it remains unclear whether the service will proceed, even if the report recommends an acquisition.

Combat Dragon III is the latest action created by a 2008 USAF planning document called the Observation/Attack (O/A)-X Enabling Concept, which called for acquiring a fleet of aircraft for the light attack and armed reconnaissance (LAAR) missions. The USAF initially planned to buy as many as 100 aircraft to stand up a LAAR wing, but later reduced the idea to acquiring light air support (LAS) aircraft for nascent air forces that lacked the resources and expertise to manage the acquisition on their own.

The USAF still has no funding or standing requirement for a dedicated LAS fleet, but launched Combat Dragon III in response to new legal authorities that could make for a smoother acquisition process. In 2015, Congress expanded the definition of the “other transaction authority” for acquiring weapon systems, allowing the Department of Defense to bypass the complex and time-consuming standard acquisition process. As a new capability, the OA-X programme is a potential candidate to take advantage of the expanded OTA definition.

A-29 at Dubai

Embraer A-29 combines light-attack and pilot training capabilities


Taco Gilbert, vice-president for integrated tactical solutions at Sierra Nevada, says: “The OTA actually has some special language that would allow them, if they so desired, at the end of [Combat Dragon III] they could award a contract, but they don’t have to, as long as they observe the right processes in selecting people to compete that they would have if they selected someone from a competition. Basically, be fair up front just like they would in a competition. But right now there is no programme. So we’ll see how it goes forward.”

Contract values for LAS aircraft pale in comparison with most USAF weapon systems, such as the F-35A or Boeing KC-46, but the legal disputes arising from the competitions are no less heated. When the Sierra Nevada/Embraer team claimed the LAS programme contract four years ago – to supply 20 Embraer A-29 Super Tucanos, to be built in Jacksonville, Florida for the Afghan air force – Beechcraft executives mounted a lengthy legal challenge that they eventually lost. The outcome of an OA-X competition under traditional USAF acquisition rules could be similar.

“I think they’ve learned procurement is hard to do," Gilbert says. "And if they keep doing it the same way they’ve always done it we might buy an airplane 10 years from now but instead if we take advantage of some of the new acquisition authorities, the OTA’s that we have, there’s a chance to go in, truly validate what the requirements are instead of an iterative process over time and accelerate this if we decide it has merit as an air force. Then we can move forward in a way that we could not with a traditional acquisition programme.

"Knowing that the entire Department of Defense has struggled with acquisition for decades, I applaud the fact that they’re trying something different this time and we’re happy to be a part of that."

For Textron, Combat Dragon III offers a chance to prove the capabilities of the AT-6 and the Scorpion jet, a project that was launched four years ago but still lacks a customer. In a way, it is a return to form for Textron, the parent of Cessna. The original Combat Dragon demonstration was staged during the Vietnam War, confirming the readiness of the Cessna A-37 Dragonfly for the light attack mission. The USAF would go on to buy hundreds of A-37s, including several hundred donated to the South Vietnamese air force.

Textron chief executive Scott Donnelly told analysts on 21 July: “The experimentation programme will really put these aircraft through their paces as they have got a bunch of different mission scenarios that includes flight envelope [and] ordinance missions that are going to be run over the course of August and maybe into the beginning of September.

“They don’t have a specific criteria or pass, fail. They want to see what the aircraft are capable of. Obviously, you have things like Scorpion and then AT-6 which are both very, very capable platforms, very different in terms of their performance envelope and they want to see what each of those aircraft can do as well as A-29, which we expect is also in there,” Donnelly adds. “So that would be the first step in a process here and as the Air Force has said, that will kind of inform them as to what they think their next step is.”

What that next step will be remains unclear. Although the USAF has the expanded acquisition authority, it has not budgeted funds to buy the aircraft. In the absence of a funded requirement, Congress could step in. In the 1990s and early 2000s, Congressional funding add-ons paid for the acquisition of 49 of the first 50 Lockheed Martin C-130Js for the USAF, allowing the programme to survive until it entered the service’s budget.

The OA-X also has supporters in Congress, particularly Sen John McCain. The influential chairman of the Senate Armed Services Committee released a blueprint for military modernisation last January that included a proposal to acquire 300 OA-X aircraft by 2022. The blueprint was moved forward by McCain’s committee, which inserted authorisation for the USAF to spend $1.2 billion to launch the OA-X acquisition in fiscal 2018.

But the real impact of the proposal is still murky. The House Armed Service Committee’s version of the same authorisation bill contained no funding provision for OA-X. Neither the Senate nor House appropriations committees have inserted any funds for the programme. And McCain recently revealed that he has a glioblastoma, an aggressive brain tumour, leaving the fate of the OA-X programme’s biggest legislative champion in doubt.

Despite the obstacles that remain, Sierra Nevada’s Gilbert, a former USAF pilot and requirements director, believes the training and cost issues confronting the USAF will eventually drive support for the OA-X programme.

“The US Air Force is facing several major challenges,” he says. “They don’t have enough fighter pilots – they’re already 600 short. They are forecast to go up to 4,000 [pilots] short. They don’t have the cockpits to train and season pilots, and they don’t have the money. They have a limited number of airframes, so they can’t burn up service-life on training.

“That recommends the A-29,” he adds. “It performs all the fighter missions. It can take over those missions in that permissive environment. If that environment becomes non-permissive or overly threatening then you’ve still got that higher-end [capability] and you’ve preserved the life of those assets. And you can roll them in rather than squandering the hours when they weren’t needed.”

In the past, the USAF has used Northrop T-38 trainers to keep Boeing B-52 first officers current despite a lack of available flying time for bombing missions. In the future, the USAF could redeploy the T-X trainer in a similar role, although it has not committed to use that aircraft for any role besides lead-in fighter and bomber training. Alternatively, the USAF could use OA-X jets or turboprops equipped with advanced mission systems.

Ultimately, however, the USAF would be obliged to use the OA-X fleet in its primary role of light attack and close air support. Echoes of the Vietnam-era DoD study still arise. In 2008, in fact, a senior USAF official told journalists that aircraft such as the A-29 and AT-6 were too vulnerable to emerging threats, such as shoulder-fired, heat-seeking missiles. In current operations, such as Operation Inherent Resolve in Iraq and Syria, videos have surfaced showing rebel forces shooting down Syrian government fighters and helicopters with such weapons.

“They’re serious [threats] but they all have mitigation,” Gilbert says. “When you look at a manpad against an airborne platform it’s looking at that heat signature and when you’re flying a jet you’ve got a really big one at the back of the airplane. When you’re flying a prop it is a heat signature, but it’s not nearly as significant, plus it’s blanked by the wings quite a bit. Most of the threat is a ground-fire threat, and we’ve armoured up the airplane. The airplane is very durable.”

He adds: “I won’t go into the all things that you can do, but you’re not defenceless against those threats. Right now we’re flying F-15s, F-16s in Afghanistan and the Afghans are flying A-29s and they’re doing just as effectively. It has 38,000 combat hours on it. It’s not meant to fly in a high-threat environment. But it also has the ability to fly at high altitude and employ munitions from standoff. You have to be smart about the way you employ and where you employ.”

Ultimately, the OA-X competitors argue that the recommendations of the Vietnam-era analysis between the A-1 and F-4 still holds. The USAF needs both types of aircraft for the mission – not just a modern equivalent of an F-4.

“What we’ve seen over the past two decades is the air force stepped aside from the O-1s and OV-10s and those types of capabilities and went more towards the F-15s and the F-16s and now the F-35s and the F-22s,” Gilbert says. “They’re seeing that there is an overkill issue potentially. Certainly in addition to that they don’t have the financing to train and season fighter pilots in those airplanes because they are very expensive. So you can address the operational needs along with the training need along with the budget needs and the same time preserve service life of those expensive airplanes and scratch all those issues at one time.”