• Visit our partners: Our Partners:
  • Visit our partners: Our Partners:

Boeing CH-47 Chinook

By the mid-1950s the transition from piston to jet engines was well underway among the world’s major air powers. 

Due largely to the introduction of revolutionary aircraft like Messerschmitt Me-262s and Arado Ar 234s, even by 1944 it was abundantly clear that the days of once vaunted engines like Rolls-Royce Merlins were numbered.

Early jets were unreliable and relatively underpowered but huge advances were made quickly, and by the following decade they were standard issue on nearly all fighters and interceptors, as well as some bombers like subsonic B-52s Stratofortresses and supersonic B-58 Hustlers.  

Gas-turbine helicopters had been developed years earlier in France and elsewhere, but most never got past the prototype phase, and those that did were produced in small numbers. 

Most helicopters of the day were powered by big radial engines, but that was destined to change when in 1956 the US Army announced its intention to replace its aging CH-37 Mojaves with newer and more advanced twin-rotor machines with dual gas turbine engines.  

Featuring one large rotor measuring 72 feet (22 m) from tip to tip, Mojaves were powered by a pair of Pratt & Whitney R-2800-54 Double Wasp 18-cylinder radial engines, each of which produced about 2,000 horsepower. 

Able to carry more than two dozen troops and their gear or about 10,000 pounds (4,535 kg) of cargo at 120 miles per hour (190 km/h), Mojaves were capable machines, but they were reaching the end of their services lives, and the Army was looking for a serious upgrade. 

Development

Turboshaft engine on the rear of a CH-47 by Mr.Z-man is licensed under CC-BY-SA

Originally developed by Vertol which later became Boeing Rotorcraft Systems, design work on the new helicopter that would eventually become the CH-47 began in mid-1957. 

Designated V-107, Vertol’s ambitious twin-rotor machine won a joint Army-Air Force design competition in the fall of 1958. 

Having beat out proposals from other more well-known manufacturers like Sikorsky, by all outward appearances Boeing had a real winner on its hands, and the following year the Army ordered a number of prototypes for testing and evaluation.  

Boeing delivered the aircraft in short order, but though they performed well Army brass considered them too heavy for the assault role and too small and underpowered for the medium and heavy-lift roles. 

However developing an entirely new aircraft from the ground just wasn’t an option because the Army was anxious to get its new helicopters into service sooner rather than later. 

To speed things up they ordered an enlarged variant known as the Model 114, which shared many components and design elements with its predecessor. 

The new and improved 114 made its maiden hovering flight in September of 1961, shortly after which it was designated CH-47 Chinook.  

The letters and numbers were assigned in accordance with the Tri-Service Aircraft Designation System, while the name referenced Native American peoples from the Pacific Northwest. 

But though the Army was ready to place its first order the following year, funding wasn’t available, and it appeared as though they’d have to make do with less capable V-107s.  

Like it usually does however, the Army eventually found the money it needed, and CH-47 production began in 1962.

Boeing’s CH-47 Chinooks and Bell’s UH-1 Hueys were the first mass produced turbine powered helicopters, but though the former would play as significant a role as the latter the Southeast Asian conflict, Hueys would go on to become one of the most persistent and recognizable symbols of America’s military exploits in Vietnam. 

Design and Specifications

Excluding rotors, Chinooks are 52 feet (16 m) long, 12 ½ feet (3.8 m) wide and about 19 feet (5.8 m) tall. 

Each is crewed by a pilot, copilot, flight engineer or loadmaster, and between two and three gunners depending on variant and mission.  

Capable of lifting off at nearly 50,000 pounds (22,680 kg), Chinooks have such high power-to-weight ratios that their cargo capacity is roughly equal to the mass of the aircraft itself. 

Typical internal loads include 33 soldiers and their gear, 24 stretchers with attending medics and equipment or some combination of these. 

Most loading and unloading is done via wide ramps in the rear of the fuselages, though various side doors can be used as well. 

CH-47s are also capable of carrying bulky items like M198 155 mm towed howitzers which weigh about 16,000 pounds (7,300 kg), slung from hardpoints under the fuselage.  

If you watched the video on Operation Mount Hope III over on Side Projects, you already know that this is how a partially disassembled Russian Mi-35 attack helicopter was taken from Libyan forces in Chad by American “Nightstalkers” in 1988. 

Their aircraft of choice – the MH-47E – has been used by US special forces since the ‘90s. 

Derived from CH-47C airframes, MH-47Es have more fuel capacity and greater ranges, as well as more powerful radars that allow them to fly close to the ground at high speeds at night and in poor weather. 

Regardless of variant, all CH-47s are powered by twin turboshaft engines housed in nacelles protruding from either side of the rear rotor pylon. 

Power is delivered to the fore and aft rotors by driveshafts, and if one engine fails the other can supply power to both through a central gearbox. 

Each rotor measures nearly 60 feet (18 m) in diameter, nearly half of which overlaps in the middle of the aircraft.  

To ensure that they don’t slam into one another even in the event of an engine loss, the rotors are mechanically synchronized. 

Though the Lycoming T55 turboshaft engines on early variants produced about the same horsepower as the radial engines in the Mojaves they replaced, later versions got significant engine upgrades that nearly doubled total horsepower.  

One of the most noticable differences between CH-47s and traditional copters like Hueys, Blackhawks and Sea Stallions, is that Chinooks have two main rotors instead of one.

Since their rotors spin in opposite directions each cancels out the other’s torque, thereby making tail rotors for stabilization unnecessary. 

This also makes CH-47s less sensitive to shifts in center of gravity, which they often experience when loading, unloading, and airdropping cargo and troops. 

In addition, twin-rotor designs allow more power to be used for lift and thrust, which makes CH-47s surprisingly speedy for their size. 

When they entered service in the early ‘60s they were among the world’s fastest helicopters, and more than a half a century later they’re still one of the speediest in the US inventory. 

In fact they’re capable of exceeding 200 miles per hour, (310 km/h), only slightly slower than Boeing’s Apache attack helicopters. 

CH-47s in Vietnam

Image by TheOtherKev from Pixabay

By the mid-’60s nearly 170 Chinooks had been built, most of which were sent to Vietnam where they became the Army’s standard medium-lift cargo copter. 

But though pilots and crews had been trained extensively, there were a number of teething issues. 

Due to the cavernous interior cargo area, inexperienced personnel often overloaded Chinooks, sometimes with disastrous consequences. 

Likewise, sling loads were particularly precarious because the cargo often swung like giant pendulums beneath the helicopters, and evenly distributing the weight of awkward and bulky items like artillery pieces was often nearly impossible.  

Nonetheless, crews learned through trial and error and Chinooks proved themselves invaluable to the war effort, especially in regard to getting much needed supplies to out-of-the-way hot spots quickly and evacuating wounded troops, both of which made them particularly susceptible to ground fire. 

Due to their significant advantages in speed and cargo capacity, CH-47s didn’t generally haul troops as frequently as Air Cav Hueys, and since they were usually escorted by helicopter gunships or propeller-driven aircraft like Douglas A1 Skyraiders, early models weren’t armed. 

However they presented relatively slow targets for Vietnamese gunners on the ground, and to give themselves some measure of self-defense, crews began mounting M60 machine guns in the side and cargo doors.  

These improvised setups did help, but on more than one occasion frenzied gunners actually fired into the rotors of their own aircraft. 

To eliminate this potentially fatal scenario, later variants were equipped with door guns that had limited ranges of motion upwards.    

Shortly into the conflict it was also discovered that CH-47s couldn’t carry as much weight in mountainous areas, where in the relatively thin air their engines didn’t make as much power and their rotors didn’t produce as much lift. 

Similar problems were encountered in the lowlands too, where high heat and humidity meant that loads often had to be reduced by as much as 20%. 

The ingestion of dust into the engines was another constant problem that drastically accelerated turbine blade wear, increased downtime and lessened overall engine life.  

To address these and other issues, later C variants got more powerful engines equipped with better filters to remove dust and sand before it was sucked into the compressor.

At the height of the war the Army had 21 Chinook companies in Vietnam totalling nearly 700 aircraft. 

Of them about 200 were lost in enemy fire or combat related accidents. 

Middle East and North Africa

Standing by on a hill top, Soldiers with the 101st Division Special Troops Battalion, 101st Airborne Division watch as two Chinook helicopters fly in to take them back to Bagram Air Field, Afghanistan Nov. 4, 2008. The Soldiers searched a small village in the valley below for IED making materials and facilities. (Photo by Spc. Mary L. Gonzalez, CJTF-101 Public Affairs)

Over the years CH-47s have been used extensively in the Middle East and North Africa, often by both sides in a single conflict.  

In the mid-’70s the Libyan Air Force purchased two dozen CH-47Cs manufactured under license by Agusta in Italy, and they recruited Western pilots and service technicians to fly and maintain them.  

Libyan Chinooks flew transport and support missions into Chad during the Chadian-Libyan conflict between the late ‘70s and ‘80s. 

In addition, back when the two countries were on friendly enough terms to swap weapons for money, Iran bought dozens of Chinooks from both Boeing and Agusta with the blessing of the American government, most of which served during the Iran-Iraq War between 1980 and 1988. 

Falklands War

When war broke out in the Falklands in early April of 1982, Chinooks were in service with both Argentine and British forces.

Argentina had four CH-47s, one of which was destroyed early on by 30 mm cannon fire from an RAF Harrier, while two more were captured and pressed into service on the British side. 

Of the Chinooks in service with Great Britain, three were destroyed when two Exocet anti-ship missiles fired from Argentine Super Étendards slammed into the merchant ship Atlantic Conveyor.

On one occasion a single Chinook airlifted more than 80 British troops to safety, and many of the Chinooks that participated in the campaign are still in service today. 

Iraq and Afghanistan 

Hundreds of CH-47s have been deployed to the Middle East since Operation Desert Storm got underway in the summer of 1990. 

Since then they’ve played significant roles in the United States’ Global War on Terror up until the rather abrupt departure from Afghanistan in late 2021. 

Like in Vietnam, Chinooks were used extensively for heavy transport, air assault missions and for ferrying troops to far flung corners of the mountainous and largely inaccessible country. 

Again, due to their twin-rotor design, they were often able to operate in high altitude areas where newer UH-60 Blackhawks couldn’t, and by some estimates one CH-47 could do the work of five UH-60s. 

Though they were typically escorted by attack helicopters like AH-64 Apaches, a number of Chinooks were shot down by the Taliban, including one that took a direct RPG hit just outside Kabul in the summer of 2011. 

All 36 soldiers and crewmen including special forces members from the American Army, Navy and Air Force, as well as a few from NATO allies were killed, marking the event as the single deadliest helicopter incident of Operation Enduring Freedom. 

Variants

New variants like CH-47Ds which entered service in the early ‘80s featured more powerful engines and transmissions, composite rotor blades, redundant electric and hydraulic systems and redesigned cockpits that reduced the crewmember’s workloads. 

Military versions have been exported to nations around the world including England, Morocco, Thailand, Greece, Japan and the Netherlands to name just a few. 

Far and away however, the US Army and RAF are the largest users of CH-47s. 

Whereas early variants’ engines collectively produced about 4,000 horsepower, new Honeywell turboshafts in contemporary F models crank out nearly 10,000 horsepower in total, hence over the years maximum takeoff weight has increased by nearly 20,000 pounds (9,070 kg).   

In addition, some Chinooks were converted into ACH-47As, in which the first A stands for “attack.” 

These featured two fixed 20 mm cannons in the nose, one turret mounted 40 mm grenade launcher, multiple .50-caliber machine guns housed in pods on the sides of the fuselage alongside 70 mm rockets or .30-caliber Gatling gun-style “miniguns.” 

Needless to say they packed a huge punch, but conversion and maintenance costs were prohibitively expensive, and in the end the copters were in greater demand as transport aircraft, so the program was eventually scrapped.   

Of the four that were made, one collided with another CH-47 on the tarmac, one was downed by groundfire, and another was lost to “friendly fire” when one of its 20 mm cannons threw a restricting pin and shot off its own front rotor. 

Other B, or “bomber” models were tasked with hovering over stubborn ground targets like Viet Cong bunkers and dropping either napalm or tear gas canisters onto them. 

Another variant of which about 100 were built, was a dedicated recovery model that served almost exclusively in retrieving downed aircraft either intact or in pieces. 

Some estimates suggest that in this role alone CH-47s recovered thousands of airplanes and helicopters worth billions of dollars. 

Disaster Relief

Arguably, CH-47s have assisted in disaster relief around the world more than any other helicopter in recent memory. 

This is largely due to their twin-rotor design and ability to transport heavy loads slung from hooks under their fuselages, the latter of which allows them to carry large water bladders used to combat forest fires. 

During both Hurricanes Andrew and Katrina they were the backbone of relief efforts, especially in areas that were inaccessible to vehicles due to road damage and flooding. 

Japanese CH-47s were also used to drop sea water on overheating reactors after the Fukushima Nuclear incident in 2011. 

To protect crews from radiation levels, each was outfitted with lead plates in their floors. 

Even so, flight times were limited to just 45 minutes, and in the end they were never able to deliver enough water to keep reactors 3 and 4 cool. 

The End? 

Despite their age, Chinooks are still in high demand around the world, and they may remain in production and service for another three or four decades. 

If so, they’ll become members of a very exclusive club composed solely of aircraft and weapons systems – like the Black Dragon Howitzer – that remain in service for a century or more.  

Though the US Army is currently considering other options through the Future Vertical Lift Program, most designs haven’t progressed past the concept phase. 

To date nearly 1,400 CH-47s of all variants have been produced, and in both developed and developing countries, many of those built in the ‘70s and ‘80s are still in use today in military as well as civilian applications like construction, mining and oil extraction. 

Related Articles

LEAVE A REPLY

Please enter your comment!
Please enter your name here

Stay Connected

51,032FollowersFollow
868,000SubscribersSubscribe

Random Article

Confederation Bridge: The Longest Over-Ice Bridge in the World

Written by Matthew Copes With the development of railways in the latter part of the 19th century, the movement of freight in Eastern Canada became...

Latest Articles