Sikorsky’s H-60 series of Black Hawk helicopters have become legendary for their prowess on the battlefield, but almost a decade before the first UH-60 entered service, Sikorsky had a different sort of Blackhawk in mind: The S-67 attack helicopter.
By coupling incredible speed and maneuverability with the ability to carry over 7,000 pounds of firepower or a half dozen fully-kitted special operators, the S-67 attack helicopter was not only a powerhouse in its day, it would still be among the most capable attack helicopters on the planet if had ever entered service.
The Advanced Aerial Fire Support System (AAFSS) Program
One year before the United States entered the Vietnam War, the U.S. Army solicited proposals for the Advanced Aerial Fire Support System (AAFSS) program, which aimed to be the first program in history to design a helicopter from the ground up for armed military applications. By February of 1965, the Army awarded contracts to both Lockheed and Sikorsky for further development on their respective designs, with Sikorsky fielding an entrant they called the S-66, and Lockheed submitting their own CL-840 Cheyenne.
Ultimately, Lockheed’s proposal would win out and secure a developmental contract for 10 of their combat helicopters, only to have the program unceremoniously scrapped in 1969 after Lockheed failed to make satisfactory progress addressing a list of eleven technical issues that had surfaced, including a serious concern that the helicopter had grown too heavy for the Army’s purposes.
Following the failure of the Cheyenne, the Army was left with no option but to resort to their backup-plan: the less advanced and as such, less complex and expensive, Bell AH-1G Cobra that would go on to earn renown for the Army and Marine Corps over its decades of service to follow.
But back in the Sikorsky offices, the firm whose namesake invented the first practical helicopter in history, went back to work on their designs, undeterred in their goal to field the most capable attack helicopter the world had ever seen.
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An attack helicopter without a defense contract
Knowing full well that the United States was rapidly learning the value of capable military helicopters like the UH-1 Iroquois (better known today as the “Huey”) in Vietnam, Sikorsky set about work on yet another attack helicopter design, dead set on ending their military rotorcraft losing streak.
Despite steady sales of the brand’s other production helicopters, Sikorski’s failure to secure the AAFSS contract was just the latest in a series of missed opportunities to get a new helicopter into Army hangars. Sikorski had already lost the Army’s utility helicopter contract to Bell, the Light Observation Helicopter contract to Hughes, the Large Utility Helicopter contract to Vertol, and the Heavy Lift Helicopter effort to Boeing-Vertol. With no new production programs on the horizon for Sikorski, they began their new effort without any Pentagon funding.
This new rotorcraft would leverage the hard lessons they’d learned developing the S-66, with the Sikorski team also aiming to benefit from what they were able to glean observing the Cheyenne’s subsequent failure. By mid-1969, Sikorsky announced initial development on their new high-speed helicopter gunship they chose to call the S-67 Blackhawk.
In January of the following year, Sikorsky’s executive vice president, John A. McKenna, was tasked with overseeing the new effort. His challenge at the onset was simple enough in theory: design a helicopter that weighed between 18,000 and 20,000 pounds and could reach speeds as high as 200 knots (or around 230 miles per hour) in a shallow dive. While armament and other variables were obviously of import, this new platform had to be an incredible helicopter above all else.
With a limited amount of both money and time, McKenna expediting development by combining new design elements with the old, making what was essentially a new helicopter, despite a heavy reliance on previous designs and methodologies that had already proven themselves successful in past programs.
It may come as little surprise then, that a number of design elements from the failed S-66 found their way into this new helicopter design. McKenna also included elements of the S-61F compound helicopter program as well, which incorporated wings and an auxiliary propulsion system. In some regards, the S-67 Blackhawk could really be seen as the progeny of the S-61 and S-66 programs as a result.
“The S-67 is a combination of proven components and new design concepts,” a Sikorsky fact sheet stated.
“The result is a new helicopter weapons system at greatly reduced cost and technical risk; high performance, ease of maintenance, and early availability.”
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Sikorsky built the S-67 Blackhawk in just seven months
McKenna’s design approach resulted in an incredibly rapid development cycle, with his team producing their first working prototype just seven months after he took over development. Their new S-67 Blackhawk had swept wings and a large cambered vertical fin for stability, a narrow fuselage with a cockpit built for two, and plenty of power to spare. And while the lines of the helicopter may have been somewhat familiar, not everything about the design came off Sikorsky’s shelves. In fact, the S-67 was the first helicopter ever to use a large, cambered vertical fin to benefit directional stability, effectively proving the concept sound.
The tail rotor managed torque compensation while hovering and during low-speed flight, but the vertical fin’s design was so capable that it could provide all the stability the helicopter needed at speeds as low as 46 miles per hour. This design didn’t only lend itself to good maneuverability; it also made the platform far more survivable in contested airspace. As you can see in dramatic fashion in the movie “Black Hawk Down” (about some very different helicopters), a damaged tail rotor would usually mean disaster for most combat helicopters. The S-67 Blackhawk, however, could continue on its way as long as the tail’s basic shape remained intact.
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An incredibly stable and acrobatic design
The helicopter’s wings, which could be removed for different mission load-outs, came equipped with extendable airbrakes that could be fully opened or closed in less than three seconds. These air brakes literally cut the time it took the Blackhawk to stop in half under most circumstances, giving it unprecedented maneuverability when compared to other similar helicopters. Between the air-brakes, 27-foot wingspan, and stabilizing fin, the S-67 Blackhawk also proved extremely stable at nearly all speeds, making it exceptional for target acquisition and engagement (aiming and firing at the bad guys while moving).
The fuselage of the helicopter itself was rather narrow, with the pilot and gunner sitting in tandem within the three-foot-10-inch-wide cockpit. That narrow-body gave the S-67 a slimmer profile than most helicopters, making it harder to target when faced head on, while also benefiting the aircraft’s overall goal of being both fast and nimble.
And in order to ensure the S-67 was indeed fast, McKenna’s team mounted two General Electric T58-GE-5 1,500 horsepower turbine engines beneath the rotors. These powerful engines combined with its sleek design was enough to earn their Blackhawk a new world speed record in December of 1970, achieving 216.8 mph over a 1.86-mile course.
Incredibly, the Blackhawk would set another new world speed record just five days later, hitting a blistering 220.9 miles per hour on a longer course.
That second helicopter speed record would stand for nearly a decade to follow, and it’s worth noting, remains faster than any combat helicopter in service anywhere around the globe today, with the possible exception of the V-22 Osprey, if you’re inclined to count that as a rotorcraft.
Quick, nimble, and packing a whole lot of firepower
But the S-67 Blackhawk wasn’t just fast, it also packed one hell of a punch. When on an attack mission, the helicopter could carry more than 7,000 pounds of weapons and ammunition–including a turret-mounted 7.62 machine gun, 20 and 30mm cannons, 40mm grenade launchers, and even wing-mounted rockets or TOW missile pods to engage heavy armor or tanks.
Despite being a sleek and narrow aircraft, the cabin of the S-67 was modified to be able to transport as many as six fully kitted Soldiers in the space behind the cockpit, and it could reach speeds in excess of 165 miles per hour while doing it. If tasked with search and rescue operations, auxiliary fuel tanks could be mounted on the helicopter’s wings, giving it a range of 600 miles at high speed. The same cabin that could be used to ferry troops could also be filled with electronic equipment for observation and surveillance mission sets, making for a rather adaptable platform.
Despite being capable of carrying a significant payload into combat, the helicopter remained incredibly nimble. Test pilots had no trouble performing rolls, split-S maneuvers, and even loops in the helicopter.
The S-67 Blackhawk was a jack of many trades, all of which interested in the Army, who were now once again on the market for a replacement for the failed Cheyenne. McKenna’s design seemed like such a dead ringer for the Army’s needs, in fact, that they gave Sikorsky a list of small things they’d like changed and then offered up four small developmental contracts, each for around $100,000 (or around $675,000 in 2021 money), for further testing.
Defeated by an Apache
The Army was impressed with the S-67’s performance and soon began pitting it against the Bell Model 309 King Cobra–both of which were considered as potential replacements for the troubled Cheyenne, but these programs don’t exist in a vacuum, and the Army was beginning to have other concerns.
The Army ultimately chose to dump the Cheyenne program entirely, with it’s combat role filled to varying degrees by the U.S. Air Force’s A-10 Thunderbolt II and the Marine Corps’ Harrier programs. The Army wanted its own aircraft that could deliver more firepower, speed, and range than a Cobra, but because of a decades-old agreement between branches, it was barred from procuring a fixed-wing aircraft for the job. There was no way around it; the Army needed a new helicopter.
So, just eight days after closing the door on the Cheyenne program or any hope for a replacement, the Army announced its plans to procure yet another new helicopter in an effort dubbed the Advanced Attack Helicopter (AAH) program.
Sikorsky’s S-67 Blackhawk once again seemed well suited for the job, as was Bell’s King Cobra, but they weren’t the only platforms in the running. Joining the competition were designs from Boeing Vertol and Grumman, Hughes, and Lockheed, and by the following year, all had been eliminated from the running except the Bell and Hughes submissions. Among these potent challenges, it was Hughes’ Model 77/YAH-64A prototype that ultimately won out. This rotorcraft would go on to become the legendary AH-64 Apache.
But Sikorsky was still undeterred. They knew they had a capable combat helicopter, and if the United States wasn’t interested in purchasing them, it seemed entirely feasible that a friendly foreign government might. So in late 1972, the S-67 was packed up and sent to Europe, before going on to the Middle East to give different nations an opportunity to see the Blackhawk in action and drum up some interest in purchases. Upon returning, the Army once more expressed interest in the helicopter, even funding a series of new modifications to the platform, including a modified fan-in-fin, though that modification was later removed.
In 1974, the S-67 Blackhawk was once again boxed up for a European tour, where it was slated to perform alongside Sikorsky’s CH-53 Super Stallion, which had made its first flight earlier that year. Unfortunately, during a press-preview flight, Sikorsky’s only working prototype of the helicopter clipped the ground while executing a low altitude roll. The helicopter was destroyed and both men on board ultimately died of their injuries.
Despite the progress Sikorsky made with the S-67 Blackhawk, the tragic death of two Blackhawk pilots coupled with a lack of interest from military buyers prompted Sikorsky to unceremoniously end the program. But even that wasn’t quite the end of this story.
In October of the same year, Sikorsky’s new utility helicopter, the H-60, would make its first flight, and by 1979 it would enter service for the Army as the UH-60 Black Hawk... because a cool-sounding name is a terrible thing to waste.
The nearest Super Stallion was about 3500 miles away from Farnborough the day of the S-67 crash.
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The Cringebag says
Sorry. Don’t know what that means.
What really killed the S-67 and the AH-56 was neither expense or accidents. It was tactics.
Both were intended to attack in a shallow dive at a TAS of about 160 KTS. This was considered optimum for engaging tanks on the ground with the TOW wire-guided missile, and strafing other targets with the then-new Hydra 70 unguided rocket (a developed version of the 2.75in FFAR dating to the late 1940s, and itself a development of the 7 cm Fohn rocket used by the Luftwaffe against USAAF bombers in 1944-45), plus its turretted 20mm gun.
Unfortunately, this attack profile put both the S-67 and the AH-56 right in the middle of the engagement basket of Russian mobile SPAAG (Self-Propelled Anti-Aircraft Gun) systems, notably the ZSU-23-4 that was just entering service. They might have been able to dodge fire from the older, slower-reacting ZSU-57-2, but the “Zeus Twenty-Three” would have blown them out of the sky.
The end result was the development of both the AH-64 and the advanced versions of the Cobra, which to this day fly nap-of-the-earth and “pop up” to fire, then duck back down behind high ground and scoot off to hit the target again from a different angle. The motto of the “snake drivers” is basically “never linger where you have killed”.
Along with W.C. Fields’ axiom, “Never give a sucker an even break”.
The Cringebag says
taiwo popoola says
Crazy machine, I wonder if Sikorsky will open source the technology 😂
I barely remember these prototypes, and the competition, but I do remember ogling the slim designs and feats of acrobatic maneuvers like loops. Thanks for putting this together and bringing it all back to life. I had forgotten what happened to the S-67, and a bit surprised that ended its run. Tragic, very much so, but it wasn’t due to a technical failure or flaw in the airframe (I am assuming).
Great write up!
Jim Reed says
Thanks for the story. My father worked at Sikorsky from the early 60’s until he retired in 1976. I remember seeing the S-67 outside the factory when it was being tested as well at a family day tour of the plant. It was a very cool looking helicopter for Sikorsky at that time. He was always telling us stories about the S-67 and how it performed, and we were disappointed after the crash that it was never to be built. When the Blackhawk name was used on the Uttas, I remember all of us saying, they can’t call that a Blackhawk! Thanks for the memories.