The Martin B-57G; Laid the Groundwork

February 9, 2023

The English Electric Canberra is, in my opinion, a graceful and good-looking aircraft. Is it the sleekest aircraft? No. But there is something about those lines, the elegance of the Canberra, that just makes it look right.

 

And I’d go further and say that the later, American built version, the Martin B-57, is even better looking. That raised cockpit and all-encompassing canopy really tops it off, in my opinion.

 

Sure, the wingtip tanks look like an afterthought, but that’s what they were and don’t impact too much on the aircraft’s looks.

So yeah, the Canberra…a fine-looking aircraft.

Except…

This is the Martin B-57G. This aircraft evolved out of a rather desperate requirement of the United States military to do something about the major supply routes running through Laos that the North Vietnamese were using to run logistics down into South Vietnam – the so-called Ho Chi Minh Trail.

This network of routes bypassed the formidable defences of the demilitarized zone on the two Vietnam’s respective borders and was recognized as a principal target for the United States in its war against the communist insurgency raging in the south. Indeed, if you’ve read my previous article on the B-26K, you’ll know that aircraft had been developed to provide the semi-covert operations running in Laos with an interdictor for hitting the same supply routes.

But the North Vietnamese were experts at avoiding aerial attack, and so as first South Vietnamese air power improved due to American aid, then the vast resources of the USAF came to bear the Ho Chi Minh Trail became primarily a night operation, with trucks and men in the thousands streaming down it throughout the hours of darkness.

But despite the huge sums that the USAF had spent on new technologies since the Second World War, none of it was really intended for use in night interdiction. Their myopic focus on supersonic and nuclear operations throughout the 1950s had left them essentially incapable of blowing up trucks driving on a road at night.

One case study by the USAF found that in one incidence ground observers had counted and reported 154 trucks on a particular stretch of road, but the USAF strike aircraft sent to attack them had been unable to identify or hit a single one. The report also states that in 514 night missions flown by USAF aircraft over Laos in one limited period, they only managed to destroy eight trucks.

So desperate did the USAF get that they tried employing F-102 interceptors, as these were equipped with infra-red detectors for their role of engaging Soviet bombers.

 

Yep, using supersonic interceptors designed for high-altitude engagements to try to identify and attack trucks driving in the jungle. Says it all really, and worked about as well as you’d expect.

Somewhat ironically the US Army was better equipped for night missions with aircraft, with a couple of versions of the OV-1 Mohawk being equipped in turn with sideways looking radar and infrared scopes.

But the OV-1 was no long-range interdictor, and its nocturnal capability helped show up the Air Force’s deficits even more.

Obviously, something needed to be done and in December 1965 Lyndon B. Johnson, the President of the United States, got so concerned by the reports of the largely unimpeded supplies coming down through Laos that he ordered the Air Force to pull their finger out and do something about it.

Thus in early 1966 was born Operation “Shed Light”, which was intended to overhaul the USAF’s night attack capabilities. This would ultimately develop and improve technologies such as Low-Light-Level Television (LLTV), Forward Looking Infrared (FLIR) and Forward Looking Radar (FLR) which are all very much standard in attack aircraft and even in civilian usage today, but in the mid-to-late sixties were truly revolutionary.

Of course, development of such advanced technology didn’t progress entirely smoothly, and the US Air Force used the conflict in Southeast Asia as a proving ground to figure out the best way to deploy them, with initial development aircraft flying as aerial spotters and designating and/or illuminating targets for conventional strike aircraft.

The USAF had intended to build a dedicated night attack version of their latest bomber, the F-111, but this proved expensive and the equipment too bulky to integrate into the Aardvark. The Air Force then gave consideration to converting US Navy S-2 Tracker’s into night attack aircraft with Shed Light equipment, but that seems to have been a bit of a half assed affair that came to nothing.

So, the USAF had another look at inventory and figured that the B-57 might make an suitable candidate for conversion to a specialist night attacker. The American license produced version of the Canberra had been in service with the USAF since 1954 with some 403 having been built by Martin.

As such it was a well understood aircraft with the USAF, had been used widely over Vietnam in combat already and there was a large inventory of spare aircraft available, especially as the type was in the process of being phased out.

In late 1967 three B-57Bs had been experimentally fitted with a pod-mounted low light level television system underneath their port wing as project “Tropic Moon II”. These were used for operational testing over Laos between December 1967 and August 1968, but proved disappointing.

Though the results were really not very good the USAF decided that a new model that integrated both night sensors and attack capability into a single airframe might be the best approach – the B-57G.

 

In July 1968 Westinghouse were given the contract to alter sixteen Canberra’s to the new configuration, codenamed by the Air Force “Tropic Moon III”. This saw the nose of the -57G substantially modified to include new state-of-art forward-looking radar with Moving Target Indicator (MTI), below which was fitted Low-Light Television and FLIR systems, along with a laser designator. This was all controlled by a sensor operator who occupied the back seat.

Target engagement was theoretically for the system operator to use the radar to pick up targets, which could then be identified through the visual systems. He would then relay information to the pilot, who could then select the most suitable weapon for engaging the target.

In reality, the MTI never seems to have worked properly, which no doubt is part of the reason that crews complained a fair bit about the aircraft. But, should it manage to find something to attack, the B-57G could carry bombs and incendiary ordnance to deal with it.

 

And because the night vision gear had a slaved laser designator, the B-57G was able to carry four laser-guided 500lb bombs on its wing racks for precision engagements.

There was also a subsidiary weapon experiment that went alongside the development of the B-57G. “Pave Gat” saw the idea of a turret gun system being mounted in the B-57Gs bomb bay that housed a 20mm Vulcan rotary cannon.

 

This was linked to the night vision gear and could be aimed by the sensor operator as the aircraft overflew enemy vehicles, allowing for aimed strafing runs on individual targets while the B-57G flew an evasive or offset pattern. The idea was recognized as potentially more effective than using other ordnance and so two experimental weapon stations were built.

Testing did indeed show that the system was more efficient, with the Pave Gat aircraft being loaded with 4,000 rounds of 20mm capable of destroying twenty vehicle targets on a mission, in contrast to six or seven of a bomb equipped B-57G.

But Pave Gat fell victim to the delays that beset the B-57G and by the time it was ready for possible combat use it was not considered necessary.

All told, the B-57G conversion program was anticipated to cost a not inconsiderable $78.3 million, and there was quite a row within the Air Force and with the bidding contractors over this, but such was the urgent need now in the face of growing conflict in Southeast Asia and the requirement to start really putting pressure on the North Vietnamese that the money was eventually authorized directly by the Secretary of the Air Force.

Despite this, the conversions proceeded quite slowly, mainly due to issues developing the advanced technology, and so the first B-57Gs didn’t deploy for combat to the USAF in Thailand until September 1970.

But while they were certainly not good looking, they proved to be much more successful than the previous efforts by the USAF to field high performance night interdictors. The B-57Gs of the 13th Bombardment Squadron participated in Commando Hunt V, which ran from October 1970 until the end of April 1971 and hunted North Vietnamese logistic routes running through North East Laos.

In that time, the -57Gs flew 1,202 sorties during which they attacked 2,841 trucks, of which they were credited with destroying or damaging 1,931.

By previous standards this would have been considered an excellent result. But by now, the USAF had another, even more lethal concept in operation.

The AC-130 and AC-119 gunships.

While these aircraft had been developed under a separate program, they had benefitted from the advances in technology made by the Shed Light program and combined it with a comparatively huge ammunition loadout that meant they could not just kill trucks in vast numbers but stay on station far longer than conventional attack aircraft.

For example, the B-57G could loiter looking for targets in the operational area over Laos for an hour, and normally carried a maximum of six bombs. The AC-130 could hang around the same operational areas for four hours and engage many more targets.

As a result, the gunships used alongside the B-57Gs in Commando Hunt V were credited with killing at least 6,000 vehicles.

In fact, and as is pointed out in a very thorough report on the B-57G by the USAF, there were a number of operational reasons for the gunships doing better than the B-57Gs. But that was kind of irrelevant. The B-57G was an improvement, though still beset by a number of technical problems, but there were better weapons available for the very specific job they were being called on to perform.

So the B-57Gs served only eighteen months in theatre, during which one was lost to enemy action, before being returned to the United States in May 1972. They then served a couple of years in the Air National Guard, but cuts saw them go to the storage yards in early 1974 and one assumes they have long been scrapped.

And that would seem to be it for the B-57G, a failed ugly duckling.

But perhaps the biggest impact from the whole program wasn’t the success, or perceived lack of, of the B-57G, it’s the groundwork that the type laid.

For starters, while the gunships would eclipse the B-57G in the role of truck hunter, one mission profile was tested that proved extremely useful. This saw an AC-130 team up with a B-57G, with the gunship acting as spotter while the Canberra, with its better performance, went in for the kill.

These missions were remarkably successful and demonstrated to the USAF that the combination was a case of achieving results greater than the sum of the parts. And this is still a standard tactical employment by the USAF to this day, with AC-130s teaming up with tactical aircraft in nighttime operations.

But the B-57G also demonstrated the future of air support, and clearly demonstrated that tactical aircraft needed to have advanced sighting and acquisitions systems. Indeed, the failures of development program and the issues faced in developing and integrating the new technologies used by the B-57G would pay handsome dividends in creating future generations of attack aircraft, which benefitted from all of the efforts poured into Shed Light and Tropic Moon III.

So, while the B-57G was certainly plug ugly, and arguably a partial failure, it probably should be better remembered for the part it played in developing the attack aircraft that are flying now.

Sources/Related:

Air Power History; Vol. 66, No. 1 (SPRING 2019), pp. 5-18 (https://www.jstor.org/stable/26652282)

https://www.afhra.af.mil/Portals/16/documents/Studies/151-200/AFD-090521-101.pdf

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