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RAH-66 Comanche

Written by Matthew Copes 

https://flic.kr/p/hCsdeZ

One-size-fits-all.

Jack of all trades.

Multi-purpose tool.

The Swiss Army Knife of combat rotorcraft.

Stealthy, armed reconnaissance and attack helicopter.

We could go on, but whatever you choose to call it, Boeing-Sikorsky’s RAH-66 Comanche was – or might have been – a truly revolutionary machine.

Nearly four decades ago when the Cold War was still in full swing and Magnum PI was the hottest thing on primetime television, the US Army began developing an advanced multi-role helicopter intended to reduce cost and redundancy, while making the Army a leaner, meaner, and far more efficient fighting force.

But like the cost-cutting, intraservice programs championed by Robert McNamara before and during the Vietnam War, the Comanche would ultimately end up as yet another development debacle, despite being fast, agile, lethal and technologically advanced.

Now, the story of the Boeing–Sikorsky RAH-66 Comanche – the $30 billion “Super Copter” that never was.

Development

The Comanche story began all the way back in 1982, when the Army set out to streamline its burgeoning helicopter inventory.

This lofty and potentially cost-saving endeavor was to be achieved by scrapping hundreds of Vietnam-era light attack and reconnaissance helicopters like Bell UH-1 “Hueys” and Hughes OH-6 Cayuses, all of which would be replaced by newer, more efficient, and more well-rounded rotorcraft.

In the jargon of the day, the Army wanted to do more with less.

Hence, the Light Helicopter Experimental (LHX) program was born, but the RFP that ultimately led to the development of the RAH-66 didn’t reach manufacturers until 1988.

This was the dawn of the Stealth Age.

International tensions ran high, defense budgets were growing by leaps and bounds, and next-generation helicopters were seen as necessary bulwarks against the ever present communist threat.

After reviewing and evaluating design proposals submitted by rival manufacturers, the Army announced that Bell-McDonnell Douglas and Boeing-Sikorsky’s aircraft had been selected to proceed to the next level. 

Due to the project’s scope and technological demands, both of the aforementioned bidders were multi-company conglomerates that had joined forces to share technology and the financial and logistical burdens associated with developing an all new aircraft.

Then in 1991 the Soviet Union Collapsed.

Shortly thereafter Boeing-Sikorsky was declared the winner and awarded a $3 billion contract to build six prototypes, but only two were ever produced. 

Dubbed the Comanche, the revolutionary new helicopter was designed from the outset to serve in both light attack and reconnaissance roles.

As such, Comanches would need to penetrate deep into unsecured enemy airspace, find out what opposing forces were up to, and identify ground targets that could either be destroyed using on board weapons, or neutralized by even more potent helicopters like AH-64 Apaches.

Due to the dangers associated with loitering over enemy airspace for prolonged periods at relatively low speeds, RAH-66s needed to be far more survivable than their predecessors.

To this end, they’d rely not only on sophisticated avionics and weaponry, but a relatively new technology that allowed them to be far less visible on the battlefield.

This groundbreaking stealthiness would allow the helicopters to elude air-to-air and surface-to-air missiles, as well as AAA fire directed from radar-controlled batteries on the ground.

Both visually and technologically, many of the design elements first incorporated into Comanches are now found on contemporary fixed-wing aircraft like F-117 Nighthawks and F-35 Lightnings.

With a promising design on its hands, in late 1992 Boeing-Sikorsky got to work building the first two prototypes at manufacturing facilities in Connecticut and Pennsylvania.

Then just before Christmas in 1994, the program was rocked by a huge setback when the Army reduced its initial order of more than 1,200 units to less than 700, purportedly to offset the cost of increased salaries for rank-and-file soldiers.

But though this and other reasons were cited for the reduction, after the fall of the Soviet Union it had become common knowledge that the program’s future was far from certain.

Nonetheless, the first prototype was unveiled in the spring of 1995, after which it was transferred to South Florida to undergo intensive ground and flight testing.

The uneventful 45-minute maiden flight occurred on January 4 of 1996.

Behind schedule and plagued by serious software and airframe issues, the second prototype made its debut later that year.

Over the next eight years both aircraft received significant upgrades and modifications that included more powerful engines, more advanced avionics, and state-of-the-art night vision systems.

By late 2004 the prototypes had collectively racked up more than 500 flight hours, but projections indicated that if the Army purchased 650 Comanches, total development and procurement costs would likely exceed $27 billion, or about $45 billion today.

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Specifications and Performance

Crewed by a pilot and a dedicated weapons officer, Comanches were approximately 47 feet (14 m) long and would have weighed about 9,300 pounds (4,200 kg) with standard fuel and weapons loads. 

Powered by two 1,500-horsepower LHTEC T800-LHT-801 turboshaft engines co-developed by Honeywell and Rolls-Royce, both engines drove a fully-composite, five-bladed main rotor with a diameter of about 40 feet (12.2 m).

Instead of standard tail rotors, each Comanche prototype had fully enclosed ducted fans that reduced drag in level flight and made the helicopters quieter and more maneuverable.

Though internal fuel was limited to about 300 US gallons (1,140 L), optional tanks could be installed both in the internal weapons bays and on exterior pylons, which depending on mission requirements could triple overall fuel load.

With the optional radar mast installed over the main rotor, top speed was approximately 190 miles per hour (305 km/h), while Comanches could exceed 200 miles per hour (324 km/h) in level flight without the domes. 

At standard operating weight, cruise speed was expected to be between 155 and 170 miles per hour (250 and 273 km/h), and combat range would have been roughly 150 miles (240 km). 

To ensure that they spent the majority of their time where they were needed most, Comanches would have been capable of lingering over battlefields for four nearly three hours, after which they could have landed in remote areas and refueled via truck, instead of wasting time and fuel returning to base.

To increase survivability and efficiency, Comanches featured triple-redundant fly-by-wire systems and automated avionics, the latter of which was capable of holding the aircraft in nearly any position with minimal input from the pilot.

Even by today’s standards, Comanches were particularly futuristic looking, thanks largely to their combination of curved and angular surfaces fashioned from matte gray composite materials that absorbed and reflected radar.

The result was a helicopter so stealthy and advanced, that on average its radar cross-section was nearly 200 times smaller than the rotorcraft it was intended to replace.

Likewise, the Comanche’s infrared signature was significantly reduced because exhaust gasses from the turbines were vented through a shrouded portion of the tail section which allowed them to cool sufficiently before being emitted into the air.

Together, these and other features would have made Commanches relatively safe to operate, though trade offs would have included high per-unit cost and overall system complexity.

What’s not so well-known is that Comanches made far less noise than nearly any other known helicopter of the era – a feat achieved largely by main rotor blades canted downward at the tips.

In addition, the uncharacteristically short rotor blades actually moved more air than traditional setups, which allowed them to operate at relatively low speeds.

Comanches were as much as 50% less likely to be detected by ground-based acoustical systems, not to mention the ears of enemy soldiers and missile operators intent on shooting them down.

Protection was also bolstered by an advanced radar jamming system, flares and chaff dispensers, and a sealed and pressurized crew compartment that would have been nearly impervious to chemical and biological threats.

As necessitated by its low-altitude front line role, vital engine and avionics components and the crew compartment were also protected by strong, lightweight armor plate made from graphite-Kevlar laminate that was purportedly capable of shrugging off direct hits from infantry weapons and heavy machine guns, and glancing blows from 20 and 30 mm cannons.

All told, Comanches were designed to be quiet, lethal, stealthy, easily transportable, and capable of operating at night and in adverse weather conditions when other rotorcraft would have been grounded.

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Weapons

Comanches were the first helicopters to ever actually fly that featured internal weapons bays, one of which was located on either side of the aircraft below and beside the central engine compartment.

Each bay could accommodate three Hellfire air-to-ground missiles suitable for taking out lightly armored vehicles and trucks. 

On the downside, the weapons bays took up tons of space that may have otherwise been used for much-needed fuel, and the retractable pylons on which the missiles were mounted were heavy and prone to mechanical issues.

However, carrying weapons internally had big payoffs as well – namely increased stealthiness and reduced drag, both of which improved survivability and performance. 

Additional removable external pylons could collectively carry eight more missiles, including AIM-92 Stingers used for air-to-air defense.

When at particularly low altitudes, ground targets could be destroyed with the light weight, 3-barrel, XM301 20 mm rotary cannon mounted in a turret below the cockpit.

With a 500-round capacity, a rate of fire greater than 750 rounds per minute, and a muzzle velocity approaching 3,400 feet per second (1,030 m/s), direct fire range exceeded 2.3 miles, or about 3.7 km.

To manage the various systems, pilots and weapons officers relied on a complex yet user-friendly combination of cockpit and helmet-mounted screens akin to the “heads-up”  displays found on many contemporary helicopters and fixed-wing aircraft.

To assist with acquiring and tracking long-distance targets at night and in bad weather, Comanche crews relied largely on Forward-Looking Infrared (FLIR) sensors.

In addition, Longbow radar pods could be attached on the hub above the main rotor shaft.

Though this decreased speed and increased radar signature, it allowed Comanches to hover behind obstructions like trees and hills, while the protruding radar surveyed the area.

https://flic.kr/p/hCskJQ

Flaws

During the Cold War the Soviets enjoyed numeric superiority in regard to everything from tanks and troops to artillery and aircraft.

As such, attack and reconnaissance helicopters were vital if NATO had any hope of leveling the proverbial playing field. 

That said, when the decades-old Soviet threat vanished nearly overnight, the Comanche began looking less like a worthwhile weapon system and more like an epc money pit. 

There’s little denying that Comanches were chock full of weapons and advanced systems that may have made them lethal on the battlefield, but much of the new technology was untested and even experimental in nature.

Another persistent problem was the helicopter’s ever increasing weight.

In fact, the two prototypes became so heavy due to upgrades and add-ons, that it appeared entirely likely that the original power plants would no longer be able to produce enough “umph” to get the helicopters airborne, let alone propel them past 200 miles per hour.

Then there was a long list of head-scratching requirements that added to overall cost and complexity.

One of the most notable and infamous of which was the insistence that Comanches be capable of ferrying themselves across the Atlantic Ocean.

This was obviously meant to ensure that they could be deployed to Europe at the drop of a hat if the Cold War turned hot.

In hindsight however, it made little sense considering that Air Force C5 Galaxies would have been able to transport about eight Comanches at 550 miles per hour (805 kh/h) far more efficiently and with less risk.

Difficult to diagnose and fix software bugs were also persistent issues, and the weapons target acquisition systems proved to be overly complex and unreliable as well.

Perhaps most of all however, the Comanche’s biggest downfalls may have been excessively optimistic expectations, poor management and oversight, and “program drift,” the latter of which added significant cost and development time because the aircraft was expected to wear too many hats.

https://flic.kr/p/hCsoS3

Cancellation

These issues may have been resolved given ample time and resources, but more than a decade in the Army had lost interest not only in the program, but in the concept itself. 

The year after the first prototype flew, the Government Accountability Office (GAO) concluded that the Comanche program had lost its way.

The GAO also estimated that if the program were allowed to continue, Comanches alone would account for nearly three-quarters of the Army’s annual aviation budget by the late 2000s.

In response, the Army once again cut its order, and as a consequence, per-unit cost soared.

Likewise, in the years following the attacks of September 11, America’s defense priorities had changed drastically.

Because they were less expensive, more adaptable, and far less risky to operate, unmanned aerial vehicles became bigger priorities.

The Comanche program was officially terminated in 2004 after more than two decades of development.

Adding insult to injury, the Defense Department was forced to pay nearly $700 million (more than 1 billion USD today) in contract cancellation fees to Boeing-Sikorsky.

Ultimately, the Army decided that it made more sense to upgrade its existing utility, reconnaissance and attack helicopters, which is probably what should have been done in the first place.

But though the Comanche died a slow and unglamorous death, many of its most noteworthy design elements ultimately found their way into newer, more advanced rotorcraft.

At least in that respect, many Army and Defense Department insiders still view the program in a surprisingly positive light.

Now decades later, stealth and noise-canceling technologies pioneered during the development of the Comanche are commonly found on contemporary rotorcraft like Blackhawks – especially the ominously black ones that fly America’s “special operators” to clandestine hotspots around the globe.

Those who’ve seen them in action have reported that the helicopters are capable of flying low to the ground at full throttle nearly silently, with the exception of a light whooshing sound not much louder than a flight of pigeons would make.

Despite the ultimate failure of the Comanche program, in the not-too-distant past the Army developed yet another battlefield scout rotorcraft under the Armed Reconnaissance Helicopter Program.

This program resulted in the Bell ARH-70, which like its predecessor, was also canceled due to technical glitches, cost overruns, and the fickle nature of Army brass.

More recently, Sikorsky developed another high-speed scout and light attack helicopter – the S-97 Raider.

Clocked at more than 250 miles per hour (402 km/h), it’s significantly faster than the Comanche would have been, thanks to more powerful engines, dual counter-rotating main rotors, and a unique tail rotor that produces thrust like a propeller.

The verdict is still out on whether the S-97 will fare better than the Comanche, or whether it too will suck billions of dollars out of the defense budget and only produce two issue-prone prototypes.

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