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Big Hummer – CH-37C
When first publicly unveiled in January 1954, the Sikorsky H-37 was introduced by its manufacturer as a "giant, twin-engine transport” that represents a "tremendous advance in the art of designing and building helicopters".
In fact, the H-37 was the biggest, fastest and most powerful production helicopter in the free world until the introduction of Boeing Vertol's turbine-driven Chinook in 1961. Originally developed for the United States Marine Corps for transport of cargo and troops and for the evacuation of casualties, the H-37 had a gross weight of 31,000 pounds, more than four times that of its predecessor, the Sikorsky H-19 (S-55).
Short Development Period
After a relative short development period of only three years, the first H-37 prototype carried out its maiden flight with Sikorsky test pilot Jimmy Viner at the controls in Stratford, Connecticut, on December 12, 1953. A total of four pre-production versions, Serial No. 133732 to 133735, were built and underwent extensive evaluation under the military designation of XHR2S-1. Military production versions of the H-37 were designated by the Marine Corps as HR2S-1. The leading ‘X’ of the first four helicopters indicated that they were prototypes. Since the HR2S-1 was the second version of the transport helicopter, a ‘2’ was inserted in its name to indicate this. The Marines, being big on card playing and the ‘2’ card being called a ‘Deuce’, they nicknamed the HR2S-1 the ‘Deuce’.
The United States Army also noticed the potential of the H-37 and, in 1954, began to fly one of the four prototypes under the new designation YH-37. Later production versions were designated as H-37A. Following the Army's practice to name helicopters in honor of the American Indian tribes, they christened their H-37A the ‘Mojave’
Advanced design features...
The H-37, a very complex and advanced design helicopter, had incorporated into it many new features, such as 'clamshell' nose loading doors, similar to the Bristol 170 fixed-wing freighter, and a retractable main landing gear. It was also the first helicopter with a hydraulic main rotor blade fold system, automatic stabilization equipment (ASE), and the first twin-engine rotorcraft in U.S. military service. The airframe of the H-37 was an all-metal design consisting of the fuselage, main gearbox cowling, also referred to as the 'doghouse', stub-wings, engine nacelles, horizontal stabiliser and tail rotor pylon. The nacelles also accommodated the helicopter’s fully retractable main landing gear. The two-cell, 400-gallon capacity fuel tanks for each engine were located in the aft portion of the engine nacelles and in the adjacent stub-wing sections. This innovative arrangement made the 30-foot long cargo cabin clear for loading and unloading of troops or cargo up to a 105 mm howitzer and trailer. A cargo hatch, also referred as the ‘hellhole’, was located in the centre of the reinforced cabin floor and a cargo sling capable of carrying 10,000 pounds could be attached to hardpoints around the hellhole. In order to further assist in loading, an electric hoist, capable of lifting 2,000 pounds, was mounted on a monorail attached to the cabin ceiling.
...with Archaic engines
In contrast to its rather advanced design features, the H-37 was powered by archaic Pratt & Whitney Double Wasp R-2800 piston engines. It was used in many aircraft, including the famous Douglas DC-6 fixed-wing transport and even in World War II veterans like the Corsair and Thunderbolt.
The design of the H-37 helicopter called for the engines to be mounted in separate nacelles at the outboard end of each stub-wing, with driveshafts pointing inboard at an angle of approximately 80 degrees and upward at an angle of approximately 12.5 degrees. A hydro-mechanical clutch was splined to the output of each engine and a driveshaft connected the clutch to the main gearbox in the upper center of the fuselage. The main gearbox transferred power to the intermediate and tail rotor gearboxes and provided the correct gear reduction for the main and tail rotors.
There were two types of throttle controls in the pilot's compartment, the overhead throttle quadrant and a twist-grip throttle on each of the collective pitch controls. The quadrant throttles were used for engine starting, ground operation, clutch engagement and to synchronize the engines. Normally, during flight, the quadrant throttles were not used except for minor engine synchronization adjustments or for single-engine operation. The twist-grip throttle was used during flight and automatically synchronized the power setting of both engines whenever changes in the collective pitch occurred. The R-2800 radials powered the H-37 quite well and were very responsive to the throttles, but due to the inertia of this massive helicopter, pilots had to fly with much anticipation. It was said that maneuvers near the ground were indeed thrilling until the pilot mastered the twist grip throttle.
New World Records
In determining the maximum capabilities of the HR2S, the naval version of the H-37, two new weight lifting records and a new speed record were established at Bradley Field, Connecticut, between November 9 and 11, 1956. Piloted by Major Roy L. Anderson of the Patuxent River Naval Air Test Center and Sikorsky test pilot Robert Duke, the HR2S lifted a payload of six metric tons (13,260 pounds) to an altitude of 7,000 feet and a payload of five metric tons (11,050 pounds) to maximum altitude of 12,100 feet. The former weight record was 8,820 pounds at an altitude of 6,560 feet set in 1955 by a Russian Yakowlev Yak-24 tandem helicopter. Only one day after establishing the new records, Major Anderson reached a maximum speed of 162.743 miles per hour (142 knots) with an empty HR2S and set a new world speed record for helicopters. This topped the old speed record of 156.005 miles per hour (136 knots) set in 1954 by a turbine-driven Sikorsky XH-39 experimental helicopter.
Trials and troubles
The Marine Corps set great expectations on the brand new H-37 ‘Deuce’ which was designated as HR2S at that btime. In late 1956, Marine Corps Experimental Helicopter Squadron HMX-1, stationed at Quantico, Virginia, received its first two dark blue H-37 for squadron experimental evaluation. In the interim, new members of the Marine Medium Helicopter Squadron 461 HMH-461 attended ground school at the Sikorsky factory in Stratford Connecticut.
One of them, First Lieutenant Michael Leahy, now a retired Lieutenant Colonel, recalls, ”the first pilots came to Quantico in January of 1957 for the Fleet Introduction Program (FIP).” Awaiting them were four brand new green Deuces, serial numbers 140314 to 140318. In contrast to the already existing blue Deuces with serial numbers beginning with 138 and lacking dorsal fin at the base of the tail rotor pylon, the green Deuces were the full production configuration. The FIP was officially intended as a three-month evaluation of the HR2S helicopters under realistic conditions. According to Leahy, the squadron pilots, almost akin to test pilots, were to help weed out and correct discrepancies, which were certain to show up in the FIP. "For instance", he recalls, "there was a round main oil cooler in the original models of the Deuce, one in each engine pod. We found that they were not doing the job and the engines were overheating. Sikorsky replaced the offending coolers with more efficient square coolers which then became standard."
Another experience of Deuce pilot Leahy involved an engine clutch failure. As a senior First Lieutenant with a lot of helicopter time, compared to those who came to 461 immediately upon graduation from flight training at NAS Pensacola, he was flying with a new Second Lieutenant, doing touch-and-go landings. As they came to a hover just before touch down, the aircraft lurched rather violently down on the port side. The clutch on the port engine failed. Leahy recalls: ”I got the ship down okay, but noticed that the engine tachometer had pegged, indicating an overspeed. I quickly reached up for the offending throttle control lever on the overhead quadrant and gently pulled it back to idle. We then sat there until a crash truck arrived as a safety precaution.” A few of months earlier a Deuce burned up after a clutch failure at Quantico. ”In that instance, with a load on, the engine clutch assembly failed, causing the engine to overspeed”, recalls Leahy. ”The pilot yanked the throttle back post haste, causing a huge backfire and igniting fuel that was pouring from the punctured fuel cells, caused by flying debris from the cooling fan rotor buckets”.
Many problems of the Deuce were caused by vibration. Broken wires on the instrument panel were very common. John R. Tay, a former Deuce helicopter electrician, states that ”the biggest culprit was the automatic blade fold system. There was a switch on each blade that would indicate when the blades were locked into flight position. Vibration would cause a wire to break on one of these switches, opening the circuit, thereby indicating that the blades were still in the folded position. I sometimes think that Sikorsky put the AC inverters in the doghouse just so that we would have electrical power to repair these switches.”
During the FIP the Deuce pilots had carried out about 200 flight hours including instrument flying, single engine operations, and emergency procedures. The latter two, however, were not always scheduled. They also had hauled howitzers, jeeps and trucks, as well as external sling loads like fuel cells and concrete blocks up to 4,500 lb. When the FIP was completed in May 1957, the squadron pilots flew the green Deuces to New River, North Carolina, for full-scale squadron training.
Marine Deuces
The first operational Marine helicopter squadron using the HR2S, HMR(M)-461 (later redesignated HMH-461), was commissioned at the Marine Corps Air Facility, New River, North Carolina, on January 12, 1957. This new squadron was designed to support the operations of the Second Marine Division stationed at Camp Lejeune, N.C. but, according to Leahy, was like a continuance of the FIP for much of the first year. ”The Deuce didn't do much practical work because the Commanding Officer was an engineering zealot who just had to have everything perfect before he would commit the Deuce to duties as a prime mover”.
This attitude was replaced in spring of 1958 when Marine Air Group 26 (MAG-26) sent a detachment of HUS and HR2S helicopters on maneuvers aboard an aircraft carrier. Leahy adds, "The Deuces flew day and night, doing a whale of a lot of the 'dog work' in an amphibious landing." The Deuces proved themselves by having carried a huge tonnage of supplies and troops ashore during an operation known as PHIBEX 58, just off the coast of North Carolina. This operation finally proved their worth as a heavy transport helicopter.
Beside HMH-461, the only other operational Deuce squadron was HMH-462, stationed at the Marine Corps Air Station, Santa Ana, California. Originally the Marine Corps intended to have nine squadrons equipped with twenty HR2S helicopters each, but then chose the smaller but more reliable, single-engine Sikorsky HUS (S-58) as their standard transport. Therefore only 55 Deuces were delivered to the Marine Corps between July 1956 and February 1959. In September 1965, a detachment of eight Deuces were sent to Vietnam to support Marine Air Group 16 (MAG-16) at Marble Mountain in general transport duties. Although this detachment had only ten pilots for the eight aircraft, they flew about 5,400 hours in 1,500 missions and hauled more than 5,700 tons of cargo as well as some 31,000 passengers without an air accident.The Deuces in Vietnam saw their share of action and caught their share of enemy fire on supply runs up to the lip of the Demilitarized Zone, Dong Ha, and Con Thien. During Operation Hastings in autumn of 1966, one Deuce got 43 hits on a single mission, all from automatic weapons. Two of the Deuces carried 100,000 pounds of supplies during the Hastings mission alone. In early 1967, the first Sikorsky CH-53As arrived in Vietnam and the tough, noisy Deuces that had faithfully served the Marine Corps for ten years were shipped back to the states for storage.
Army Mojaves
The Army’s evaluation of the H-37 at Fort Rucker, Alabama included not only operational trials, but also maintenance and logistic activities. The results of the evaluation lead to an order of nine H-37A Mojave production versions in late 1954 which arrived at Fort Rucker during summer 1956.
The early Mojave version, not as complex as the Marines Deuce, had no automatic blade fold or pylon folding system, although it could be done manually, and also lacked the complicated ASE. Because of that, the Army Mojave was more reliable and easier to maintain than the Marine Deuce, but was limited to clear weather operations and was slightly harder to fly.The Mojave soon demonstrated what could be done with large transport helicopters when it lifted an M-56 tank with a 106 mm rifle weighing 5 tons at Fort Benning. The idea was that helicopter-borne tanks could quickly leap water, swamps or other areas that normally would present crossing problems.
In February 1958 Fort Benning also became home of the first operational Army Mojave unit, the 4th Helicopter Transportation Company. The 4th was also the first unit to take the Mojave overseas when it went to Germany in 1959 to support U.S. Forces in Europe. By May 1960, The Army received a total of 94 Mojaves and during the next two years returned 90 of them to Sikorsky where they were upgraded with reinforced retracting landing gear systems, crashworthy fuel tanks, and improved nose doors for unloading in hover. Also, the first Mojaves, lacking the ASE, were then equipped with a Lear Autostabilization System. All upgraded Mojaves were redesignated as H-37B and later as CH-37B.
Like the Marine Deuces, the Army Mojaves saw their share of action in Southeast Asia when a detachment of the 19th Transportation Company was sent to Vietnam to fulfil the heavy helicopter recovery role in 1963. By October 1964, nine Mojaves were in-country. The Mojaves demonstrated that they were capable of recovering intact aircraft up to the size of a Vertol H-21 with reduced disassembly time in hostile areas.
Nevertheless, maintenance personnel had always to work hard, usually under rough conditions in rice paddies or jungle clearings and often under fire, to remove rotor blades and engines from the crashed aircraft to prepare them for recovery. When the preparation work was done the Mojave came in and hovered over the downed aircraft while the crew hooked up the external sling under the watchful eyes of the Mojaves door gunners at their M60s. This was the most critical moment in a recovery operation since a low hovering Mojave naturally offered a rewarding target for enemy gunners.
At least one Mojave crashed, even without hostile activities, while attempting to sling-lift a downed UH-1B Huey from a clearing near Bien Hoa Airbase in September 1965. However, these dangerous jobs paid off. During summer and autumn of 1963, the first four Army Mojaves employed in Vietnam recovered downed aircraft with an estimated worth of more than 7.5 million U.S. Dollars.
That the Mojave did not see more extensive service in Vietnam is the result of its replacement in the Army inventory by more powerful turbine-driven helicopters like the CH-54 'Tarhe' and the CH-47 'Chinook' in the mid-sixties. In the late sixties all Mojaves were withdrawn from active Army service and handed over to Army National Guard units in Alabama, California, Iowa, Kansas and Texas where they still served until 1974.
Commercial service
In view of the accelerated interest in scheduled helicopter service by the airline industry, Sikorsky had endeavored to include in their developments the general requirements requested by commercial operators.
Regarding the H-37, sales representative R. B. Muir announced to the industry on January 19, 1954 that "The H-37 twin-engine transport development has received only limited publicity due to its classified nature, and we have been unable to determine just how soon general information can be released. However, it is a matter of public record that it is a single 5-bladed main rotor configuration, powered by two Pratt & Whitney R-2800 engines which will permit single engine operation over a major portion of its speed range". Muir asked the airline industry for indulgence and added that by late 1956 commercial modifications of the H-37 would be available, providing that the military planning is carried through. However, Sikorsky's hopes to sell the H-37 on the commercial market were never fulfilled. One major reason seemed to be the operating costs of these large piston-engine helicopters with their high consumption of expensive aviation gasoline. Future plans to modify existing H-37 helicopters with turbine engines for scheduled flights and other commercial activities were dropped in favor of newer turbine-driven helicopter designs.
Between 1971 and 1973 Keystone Helicopter Corporation of Philadelphia, PA, purchased all of the remaining H-37 helicopters in government storage. Keystone obtained FAA certification for these ex-military aircraft and successfully used a number of them commercially for external load construction work for several years. Stripped of all non-essential equipment, the FAA licensed H-37 was permitted to lift up to 10,000 pounds on the cargo hook. One typical working area of Keystone's former Deuces was the transportation and erection of wooden poles for power companies.
In late 1980, Keystone Aircraft reassembled and overhauled one of their stored H-37s, putting it into an airworthy condition again. This refurbished Deuce was painted in the colours of The U.S. Marine Corps and departed Tucson, Arizona, for it's final flight to the Naval Aviation Museum in Pensacola, Florida, on February 25, 1981.
Other H-37s can be found in The Army Aviation Museum at Fort Rucker, Alabama, The Army Transportation Museum at Fort Eustis, Virginia, and The Pima Air and Space Museum in Tucson, Arizona. The only European Museum owning an H-37/CH-37 is the International Helicopter Museum (IHM) in Weston-super-Mare, England. Unfortunately, the IHM’s CH-37 is still stored in the USA and due to its large size there is no feasible way of transporting it across the Atlantic at the moment.
adapted from Flugzug Classics article
Posted : 2002-09-25 16:11
Topic starter
Heavy Hauler The HR2S, Sikorsky's Deuce
Heavy Hauler
The HR2S, Sikorsky's Deuce
By Frank Colucci
Despite its imposing size and noisy power, the Sikorsky HR2S or CH-37 never lived up to the hopes of Marine planners who wanted a big, fast assault helicopter. The Deuce served with only two Marine squadrons and deployed in squadron strength aboard ship only once. The temperamental giant was nevertheless the biggest, most powerful helicopter in the free world for a decade. It marked the highpoint of piston engined rotorcraft development. Most important, the Deuce built the technical and operational foundation for Marine heavy lift cargo helicopters to come.
The HR2S was the first twin-engined helicopter in U.S. military service. It was the first helicopter with retractable landing gear, the first with power blade folding, and the first with autostabilization equipment (ASE). According to Deuce pilot Lt. Col. John Pipa, USMC (ret), It was the aircraft which advanced the art of instrument flying for helicopters in the Marine Corps.
The first composite squadrons aboard amphibious assault ships in the late 'fifties and early 'sixties included heavy lift detachments of CH-37s to augment CH-34 troop carriers and HOK observation helicopters. Early in the Vietnam war, the CH-37 moved tons of ammunition, rice, chickens and people with plodding efficiency and the callsign Junkman. We pioneered heavy lift, explains Vietnam Deuce pilot Bob Carlson. The technology of the Deuce became the H-53. The lessons we learned from the Deuce went into the '53.
Vertical Envelopment
Fifty years ago, the atomic bomb threatened to make the amphibious assault mission of the U.S. Marine Corps impossible. The Marine Corps Schools at Quantico in 1946 considered flying LSTs, enormous amphibious cargo planes or flying boats like the Convair Tradewind, to extend the standoff range of assault forces. They also looked at shipboard helicopters to launch assaults at greater distances from the enemy beach.
In February 1947 a report emerged on Military Requirements Of Helicopters For Ship-To-Shore Movement Of Troops and Cargo. The report called for two aircraft, a small assault helicopter carrying 15 to 20 infantrymen, and a bigger cargo helicopter for heavy equipment.
The assault helicopter had to carry 3,500 to 5,000 lb. payloads and needed a 200 to 300 mile range to launch and recover from a ship 50 to 100 miles off the beach. The first Marine helicopter was the Sikorsky HO3S-1 delivered in 1948, and it struggled with a 350 lb payload. Helicopter pioneers Igor Sikorsky and Frank Piasecki stated confidently rotorcraft with 5,000 lb payloads were within the reach of existing technology.
Vulnerable flying boats slipped into oblivion. Shipboard helicopters fit the concept of vertical envelopment where combat forces could outflank and encircle defenders ashore. The Navy ordered the HRS (Sikorsky S-55 or H-19) for the Marines to explore the assault helicopter concept. On 9 May 1951, the Navy issued a contract for the definitive Marine assault helicopter, the HR2S (Sikorsky S-56 or H-37).
Big And Bold
The XHR2S, first flown on 18 December 1953, was a monster of a helicopter. The five-bladed main rotor was 68 ft in diameter, and the four-bladed tail rotor was 15 ft across. Main rotor blades and tail rotor pylon folded automatically for shipboard operations. The round nose was split by two hydraulically operated doors opening on a cabin 30 ft 4 in. long, 7 ft 8 in. wide and 6 ft 8 in. high. The cargo cavern was unobstructed except for a removable auxiliary power unit. A 2,000 lb capacity cargo winch rode a monorail stretching from the nose doors to a 6 ft square cargo door on the right side of the aft cabin. The winch could stop over the hellhole in the floor to lift external cargo or slide out the aft door to double as a rescue hoist. Hardpoints around the hellhole could carry cargo slings with 10,000 lb external loads.
The pilot and copilot of the new helicopter sat on a flight deck reached from the cabin by a folding ladder. The cabin had space for 26 Marines, equal to two combat assault squads. It could be configured for 24 casualty litters. Ramps in the nose doors and reinforced tracks in the floor allowed jeeps and other vehicles to drive in and out. The bulbous nose doors even had windows and gun ports for the Marines aboard to provide their own forward fire support.
The XHR2S was designed to be fast. The landing gear retracted. The stub wings generated some lift in cruising flight to offload the main rotor. Their trailing edges dropped like airplane flaps to minimize downwash losses when hovering. The horizontal tailplane had airplane-like elevators to improve handling at speeds up to 130 kt.
, the HR2S needed the combined output of two Pratt & Whitney R-2800-54 reciprocating engines. The 18-cylinder Double Wasp radials were the same powerplants used in World War II Thunderbolt and Corsair fighters. On the helicopter, they were mounted sideways in pods on stub wings high on the fuselage. The driveshafts were inclined 80 degrees inboard and 12.5 degrees up to converge on the main gearbox. Engine ratings were 2,100 bhp at 2,700 rpm for takeoff and 1,900 bhp at 2,600 rpm for cruise. Sikorsky restricted the Double Wasp to 1,725 bhp normal power and 1,380 bhp in cruise. The HR2S flight crew had two sets of throttles. Twist grips let the pilot and copilot coarse power adjustments while the overhead throttle quadrant enabled the copilot to set throttle authority and balance the torque of the engines.
To keep the cargo cabin clear, Sikorsky engineers confined the 400 gal of internal fuel in the HR2S to the stub wings and engine nacelles. Two 300 gal drop tanks could hang from braced mounts on the fuselage. Emergency procedures called for them to be jettisoned immediately if an engine failed. One Deuce pilot remembers losing an engine over the water and stabbing the jettison switch. It ultimately took the ground crew about 30 minutes after landing to remove the tank by hand. The external tanks were rarely used in shipboard deployments or in Vietnam.
The HR2S was the first helicopter with automatic stabilization equipment (ASE), and main and tail rotor deicing. When first shown publicly on 18 January 1954 it gave meaning to the Marine Corps' vision of vertical envelopment. It was a fast, long-ranged, night/IFR helicopter with the lift capacity to take assault forces behind the enemy and capitalize on the advantages of terrain and surprise. The lessons learned with the HRS in Korea were aimed at the day when the HR2S joined the fleet. The potential of the big, powerful helicopter was not ignored by the U.S. Army, and in 1954 the Army began flying one of the four XHR2S prototypes under the designation YH-37.
Unfortunately, development of the big S-56 did not proceed smoothly. The heavily loaded rotor disc was extended to 72 ft diameter. Sikorsky found it necessary to add a dorsal fin at the base of the tail rotor mast. The transmission fairing below the main rotor was refined in shape. Airplane-like elevators gave way to an all-moving tailplane which drooped to the vertical in a hover and returned to horizontal trim as the helicopter picked up cruising speed. The single-wheeled main landing gear changed to twin-wheeled bogeys. The engines nacelles were redesigned with dual exhausts and air cooling grilles.
By the time the first HR2S-1 was delivered to Marine Corps Experimental Helicopter Squadron HMX 1 on 26 July 1956, the big helicopter was near production configuration. However, it was far from ready for fleet squadrons. The folding rotor system was complicated and often failed with red geysers of hydraulic fluid. The sophisticated ASE was initially touchy and unreliable. Engines drank oil almost as fast as they burned high octane avgas.
For The Fleet.
Plans called for nine HR2S squadrons with 20 helicopters each, but the Marines acknowledged the problem and limitations of the new helicopter soon after the first machines entered testing. The turboshaft engine promised power-to-weight ratios far better than reciprocating powerplants. In 1955, the Navy ordered the HUS (Sikorsky S-58 or H-34) on behalf of the Corps, and the smaller, more reliable helicopter would bear the burden of the assault mission until the introduction of the turbine-powered CH-46.
The HR2S was nevertheless a superb performer. On 10 November 1956, Major Roy Anderson and Sikorsky pilot Robert Duke flew an HR2S to 7,000 ft with a 13,250 lb payload and 12,000 ft with an 11,050 lb payload. They broke the record set a year earlier by the tandem-rotor Soviet Yak-24. Nine days later, an empty HR2S-1 established a new world's helicopter speed record reaching 162.7 mph (142 kt).
The Bureau of Aeronautics embarked on an ambitious Fleet Introduction Program (FIP) at Quantico. The FIP was officially intended not to prove the HR2S but to familiarize Marine pilots and maintenance crews with the complicated new helicopter. Plans called for four aircraft to fly 100 hours each and included operations from rough terrain and landing mats. During the FIP, the HR2S's flew with 2,800 lb. concrete blocks and 4,500 lb. (500 gal) fuel cells in external slings. They swallowed 75 mm howitzer jeeps, 105 mm guns, Mechanical Mule trucks, and Mighty Mite 106 mm recoilless rifles. Marine pilots practiced taxiing, hovering, single engined operations, instrument and night flying, and emergency procedures.
The FIP accumulated just 200 flight hours, but the experience was enough for the HR2S to begin full scale squadron training with Marine Medium Helicopter Squadron 461 at New River, North Carolina. (The Heavy lifter was evidently still in the future.) HMRM 461 enabled the 2nd Marine Division at Camp LeJeune to demonstrate vertical envelopment. In November 1957, HMRM 461 airlifted 400 Marines from Camp Lejeune to attack a simulated missile site at abandoned Bogue Field. The helicopters inserted each 20-man assault team in less than a minute. With 20 troops and one external tank, the HR2S-1 had a combat radius of 100 miles.
The HR2S flew its shipboard trials aboard USS TARAWA. The shipboard capability of the big helicopter gave rise to a special purpose version for the Navy. In the summer of 1955, the Navy began work on an Airborne Early Warning version of the S-56. The first of two HR2S-1Ws flew in late 1956 with a huge plastic radome in place of the cargo doors. Behind the dome was a General Electric AN/APS-20E radar intended to warn battlegroups of low-flying aircraft. The picket helicopter had a crew of four and could double fleet radar coverage compared to shipboard radars. One of the AEW testbeds crashed at Patuxent River in 1958. The other continued test work into 1959 and last appeared at Lakehurst Naval Air Station wearing U.S. Army markings.
Flying Deuces
HMRM 462 was commissioned at Marine Corps Air Station Santa Ana, California as the West Coast Deuce squadron. It had a highly experienced complement including former test pilots from HMX 1 to overcome for the new giant's teething pains. As a young Lieutenant with ample flight hours as an instructor at Pensacola, Lt Col John Pipa, USMC (ret) transitioned from fixed-wing to helicopters at Whiting field and went immediately to the HR2S in the spring of 1958. He was one of the pilots ferrying new Deuces from the Sikorsky plant in Connecticut to California. With the aircraft then restricted to 70 kt and the crews forced to land repeatedly to add oil to the engines, the flight took some time. We used to kid the refueling crews by telling them to fill the oil and check the gas, he recalls. All through its career, the HR2S leaked oil profusely. A bucket was usually hung under the main transmission to collect routine seepage.
Oil consumption was finally brought under control when baffles were added to the oil tanks, and HMRM 462 worked hard to fix other problems with the Deuce. Electrical shorts in the cargo hook system caused embarrassing fumbles. During maneuvers at Camp Pendleton, Deuces accidentally dropped two 105 mm howitzers from 1,500 ft. The regimental commander was ready to be institutionalized.
Despite the problems, the flying qualities of the big helicopter were good, and the Deuce made a major advance with its ASE. John Pipa recalls, It was a good system generally. Without it, it was extremely difficult to fly the aircraft. You could takeoff, land, and cruise, but it was almost impossible to accomplish a task like external hookups or confined area landings.
The vibration environment of the Deuce was so bad the instrument panel was not rigidly attached to its frame in an attempt to damp the shaking and help crews read the dials. The sustained shaking affected pilots in different ways. I used to wear a jock strap when I flew because it made my testicles hurt, says John Pipa. Other people found it made their noses itch. That was a real problem because you needed two hands to fly the thing.
A vibration suppressor later installed above the clamshell doors in the nose worked well, but the continuous vibration finally caused the suppressor springs to snap and throw shrapnel around the cargo cabin. The suppressor was finally wrapped in heavy mesh to contain fragments.
The HR2S-1 could indeed transport 26 Marines, but the big helicopters could not be the assault aircraft the Corps wanted. John Pipa explains, They were so new and so delicate they were used very, very judiciously. For a long time the only thing we did was train with them. With availability low, Deuces usually flew only alone or in pairs. HMRM 462 eventually took its big birds aboard ship in a heavy lift detachment on USS THETUS BAY to complement a squadron of H-34s. We hauled cargo like the Marine Corps never hauled before, says John Pipa. The Deuce could accommodate two jeeps or other vehicles with ease, and most loads were carried internally. The blade fold system worked well aboard ship and was cleared to operate in winds up to 65 kt. However, the huge nose doors could not be opened with a stiff wind over deck for fear of damaging or losing them.
Pilots Of The Caribbean
Sikorsky built four XHR2S prototypes and delivered the last of 55 production HR2S-1s to the Marines in 1959. The Department of Defense standardized aircraft designations in 1962. The Army received 94 CH-37As and remanufactured 90 as CH-37Bs. The Marines had the CH-37C, but still called their big helicopter the Deuce. In 1962, young Lieutenant Bob Carlson got his wings and came to New River expecting to fly the H-34. He was assigned instead to HMRM 461 with the Deuce and almost immediately left with a two-aircraft detachment aboard an LPH in the Caribbean Amphibious Force. The CH-37s were aboard with a squadron of UH-34s to carry radio jeeps, ambulances, and palletized cargo.
Lt Carlson transitioned to the big helicopter with little difficulty and soon earned how to fly it from a ship. Everybody thought it was cumbersome, but once you got comfortable with the airplane, except for the fact you needed more room on deck, we amazed ourselves with nice, tight approaches. The Deuce pilot went on to be maintenance officer for the redesignated HMH 461 on the GUADALCANAL when the Heavy lift CH-37s made their one and only squadron-size deployment. A lot of things on the H-37 were technologies they were trying out, he recalls. Automatic blade fold was a nightmare to maintain.
Fixed wing engines designed to go 2,000 hours between overhauls lasted just 350 hours straining under helicopter abuse. With spare parts in short supply for the small Deuce fleet, Mr. Carlson recalls Cannibalization was a high art. However, with H-34s destined for Vietnam, the H-37 was called upon to support the standing Marine Caribbean Ready Force. To prove the unit's readiness, HMH 461 flew all 12 of its Deuces in formation one day, although some were still on maintenance test flights.
Another pilot aboard the GUADALCANAL had transitioned to the Deuce from the H-34. As a Second Lieutenant with HMM 461, Mr. Keeler recalls, It was a great airplane to fly. It had lots of power in those 18-cylinder radials. Empty, the airplane would just roar. Of course, you didn't do any good flying it empty. From the Guadalcanal, the CH-37 hauled both troops and cargo, mostly in internal loads. Crews learned how to place the big helicopter on a relatively small ship. It was a huge airplane to be landing on a deck spot. You felt like you were mighty close to other airplanes and the superstructure.
Former HMH 461 pilot Lewis Watt remembers, Bringing this thing aboard ship was a handful. You had so much more mass and size, there was more to pay attention to. And you didn't have the response of the H-34. We also didn't have any power margin. You just had those engines near the ragged edge the whole time you were flying the machine.
The autostabilization equipment of the CH-37 provided attitude and heading hold functions. Mr. Watt recalls with ASE operational, the H-37 was more stable than the smaller H-34. HMH 461 commanding officer Major Dick Hawley was determined to have pilots exploit the IFR capability of the Deuce. When everything was working, it was a fine instrument machine, says Mr. Watt. However, one dark night on an instrument approach, the springs in the vibration suppressor failed. Mr. Watt's co-pilot had to brace the shaking main panel with his feet so the pilot could read the instruments and land.
Junkman In Vietnam
Most pilots from the Caribbean deployment transitioned to H-34s to relieve the first Marine pilots due for rotation back from Vietnam. In 1966, Lew Watt, Bob Keeler, and Bob Carlson were all sent to Headquarters And Maintenance Squadron 16 (H&MS 16), Sub-Unit 1 at Marble Mountain to inherit nine CH-37Cs and the callsign Junkman from the West Coast pilots going home.
The U.S. Army began using CH-37Bs in Vietnam in 1963 for downed aircraft recovery. The Marines followed the Army example when in September 1965, two weeks after arriving in country, a Deuce recovered another helicopter down about 15 miles from Chu Lai. In October, an H-34 on the ground about 8 miles from Danang was stripped by Marine maintenance crews and picked up by two CH-37s. One Deuce sling loaded the airframe and the other the transmission. The helicopter carrying the airframe was hit by groundfire and forced to set down. Another CH-37 came out to pick up H-34 carcass, and the damaged Deuce was repaired and flown back to base.
Marine CH-37s recovered downed aircraft only infrequently. Their primary mission was resupplying troops in the field. Two aircraft, hauling cargo and people, flew a regular run between Marble Mountain and Dong Ha with a stop at Phu Bai. A detachment of two or four aircraft also operated out of Dong Ha in the northern portion of the I Corps region of South Vietnam. The earlier emphasis on instrument flight paid off when Deuces flew from Phu Bai to Danang under 200 ft overcast in 1/4 mile visibility.
Marine CH-37s hauled tons of bullets, C-rations, troops, and livestock, mostly in mixed random loads carried internally. The size of the load depended on the time of day and amount of fuel remaining in the aircraft. On one occasion, a Deuce low on fuel lifted off with 28 Marines aboard after a long, rolling takeoff. Resupply or medevac missions under fire were generally flown by the H-34s. Vietnam Deuce pilot Bob Keeler explains, Normally, we didn't get sent into hot zones. If the shooting had started, we would be diverted because it would take too much time to unload us. No one wanted to be unloading a big old Deuce with a firefight going on.
The missions were not however always safe. When we got into a real mess, we stumbled into it. On the ground, we were a very attractive target for VC mortar teams. Two Deuces received significant mortar damage one day. The executive officer of H&MS 16 Sub Unit 1 was wounded by groundfire at the controls of his Deuce. His copilot brought the aircraft home.
The original 'milk run' to Khon Tien became a dangerous gauntlet. Enemy fire enabled H&MS 1 Sub Unit 16 operations officer Lew Watt to prove the aircraft could indeed fly with its nose doors open. When you were unloading with the doors open and the ramp down, and a mortar round landed nearby, it became time to get the hell out of there.
On a mission to pick up C-rations abandoned near the demilitarized zone by a Marine Company moving on to another area put a Deuce on soft ground. As the load got heavier and the landing gear oleos compressed, the open clamshell doors dug into the ground just enough to jam and blow the hydraulic seals. The CH-37 sat on the ground fat and vulnerable until spare parts arrived. Given the reliability of Deuce systems, CH-37 crews rarely retracted their landing gear or folded their rotors. Likewise, with the longest missions lasting only two hours, the Deuces never flew with external tanks.
The size and variety of loads was impressive. We just astounded everyone with these greasy old helicopters, says Lew Watt. Resupplying ARVN (South Vietnamese) troops meant hauling tons of fish oil, rice, and livestock. The crewchief of one Deuce decided to use the chickens to peck the rice out of the helicopter's cabin floor. The idea worked well until the chickens were frightened by the helicopter's noise and unloaded their own contents in flight.
The threat of groundfire changed the way the Deuce was flown. Pilots learned to spiral into landing zones rather than follow the long, straight approaches common to the big helicopter. Escort tactics taught Deuce crews to work with Huey gunships, and in at least one instance Crusader jets. CH-37s in Vietnam usually had 50 caliber machine guns in waist positions to provide some self-defense.
The Deuce effectively ended its career in Vietnam. As the turbine-powered CH-46 and CH-53 debuted in-country, the CH-37 crews were told their war was over. However, as the Sea Knight and Sea Stallion worked through their teething problems, it became clear the old Deuce would have to fly on. Bob Carlson remembers, These airplanes were old in terms of vibration. They aged a lot quicker than airplanes do now. We'd get fuselage cracks, but they didn't fall apart. He adds, The grunts were afraid of us until we hauled in the stuff they needed. They still didn't want to fly with us, but that was all right.
By May 1967 when the CH-37Cs stopped flying in Vietnam, the Marine Deuces had accumulated 5,300 flight hours and carried 32,000 passengers and 12.5 million pounds of cargo in the war zone. Some of the aircraft were apparently abandoned in country. An Air America pilot later told Bob Keeler some Deuces were serving as multi-family housing. Others returned to the United States, inexplicably overhauled at Jacksonville, Florida, then flown to final desert storage at Davis Monthan Air Force Base in Arizona.
Lewis Watt accumulated about 850 hours in the Deuce and believes he was one of the last Marine pilots to fly the CH-37. In the I Corps in '66 and '67, we played a very significant role in the Marine Corps war during those years until the H-53 came along. For the vintage of the helicopter, the Deuce was a wonderful flying machine.
Posted : 2002-09-25 16:19
Very good history of the Deuce, I remember it well. I served with HMH-461 62-65 & H&MS-16 SU-1 1966.
I disagree with two pionts in your history. As I recall we did carry aux tanks on the Junkmen (see photo gallery) and we were armed with M-60's.
I served as 1st Mech (door gunner) on Junkman 6, we were one of the first two Deuces in Dong Ha. When we arrived thier were no facilities, we slept in the aircraft and survived off of C rations "borowed" from the grunts.
Posted : 2004-03-02 16:29
CH-37
I'd like to see dsilver's CH-37 photo gallery. I remember the last 37 squadron returning from a Carib. Cruise in late 65 or early 66 at New River. I don't know how many of them they had up maybe 10 or 12 in formation; but it shook the whole base! Fond memories.
S/F
Tim
Posted : 2004-03-07 09:54
FYI
some members photos here
https://www.popasmoke.com/visions/index.php?page=view&category=98
George T. Curtis (RIP. 9/17/2005)
Posted : 2004-03-07 12:44
Short video of a Deuce at MMAF (3.4MB, 19 seconds)
Posted : 2004-03-07 16:11
H-37
Great pictures George. I'm sending them to my Igor friends.
S/F
Tim
Posted : 2004-03-07 17:23
I don't remember how many we had up on our return to New River but we did fly all 16 aircraft in formation over the base a few days before we left.
semper Fi
Posted : 2004-07-25 17:19
Thank you Al for posting my article "Big Hummer" which was published in Flugzeug Classic issue 3/2001.
Please let me know if anybody would be interested in my original article with photos so that I can send a copy.
Regards,
Gunther Winkle
Posted : 2004-09-12 09:59
461 Squadron Fly By
I remember getting up 13 at one time in 65 at new river as nwe had 3 that had been cannabilized to do that(I have a picture of that still) we had just come out of reinforceing the wing spar as they we all cracking and we took some of them down a veiques cruise ended up going to Santo Domingo and the a couple of the duces couldnt make it so they sat a rosy roads until the spars could get repaired again.
It was the most interest work I have every done was on those old things and also my favorite squadron of all times
Posted : 2004-09-16 06:59
