United States of America (1974)

Anti-Submarine & Utility Helicopter

190 total airframes built: 85 converted to SH-2F w/ 48 new airframes.

Introduction

Kaman’s SH-2 proved an exceptional asset for the US Navy through the mid to late Cold War, serving a variety of roles across nearly the entirety of the surface fleet. Beginning its service as a multipurpose naval helicopter designed to ferry equipment and rescue downed fliers, the light helicopter soon played an even greater role as an anti-submarine aircraft. Replacing the outdated and clumsy DASH drone, the Seasprite incorporated cutting edge sensors to become a sub chaser that could fit on even the lightest modern frigates in the US Navy. Spanning the early sixties to the new millenium, the Seasprite served as an able light transport, search and rescue, and anti-submarine helicopter before finally being phased out by the UH-60 Seahawk.

Whirlybirds

Of all the world’s navies, that of the United States was the first to employ helicopters enmasse. While helicopters had undergone considerable development since the first usable designs had been conceived in the 1920s, they remained a clumsy novelty into the 1940s. This was until the Sikorski R-4 was developed. Igor Sikorski, born in the Kiev Governorate in the reign of Alexander II, was already an aviation legend before the Russian Civil War saw him emigrate to the United States in 1919. Having previously designed four engine biplane airliners in the Russian Empire, and several of the flying boats that saw Pan Am span half the globe, Sikorski was a name known for breaking new ground. His R-4 helicopter would build this reputation further. The greatest advantage the R-4 had over its foreign contemporaries, most notably the Focke-Anchleis 223, was its simplicity and ruggedness. The use of a main lifting rotor and anti-torque tail rotor would prove a far lighter, and more robust method of control than the transverse and intermeshing rotors that drove a number of contemporary types.

The R-4 reached the notice of the US armed forces through Commander William J. Kossler of the Coast Guard, after the officer had seen the XR-4 undergo a test flight in April 1942. Impressed, he invited fellow officer CDR W.A. Burton to see the helicopter. The report on the aircraft took note of its ability to conduct patrols at low speeds, and unlike US Navy airships, did not require a large hangar for storage. Initially skeptical, the Navy was later convinced of the aircraft’s anti-submarine and convoy surveillance properties. Limited production began in 1942 and testing was conducted through 1943 and ‘44, though its sub chasing capabilities were not pursued. Instead, the helicopter proved itself as an air rescue vehicle. Its first trial came on January 3, 1944, when it delivered vital blood plasma from New York City to Sandy Hook, New Jersey, through a violent storm, in order to treat sailors after a fire had sunk the destroyer USS Turner. In all, several dozen R-4s would be delivered to the Coast Guard and Navy, where they took part in a number of rescue missions across North America and the Pacific.

While the R-4 was still limited in its carrying capacity and presented pilots with challenging flight characteristics, it demonstrated the utility of helicopters to every branch of the US armed forces. Sikorski would capitalize on this over the coming decade with their heavy H-19 and H-34 helicopters. Entering service in the early fifties, these helicopters were all metal and equipped with heavy radial engines. In civilian and military service, they would prove exceptional, capable of airlifting cargo to otherwise unreachable areas. However, a new, revolutionary advancement would soon render them obsolete. In 1955, the French Allouette II became the first production helicopter to feature a geared gas turbine. The turbine provided a far better power to weight ratio than the radial engines, and it was compact, allowing it to be placed at the center of the helicopter and thus avoided the forward engine placement that made some earlier helicopters nose heavy. This engine also allowed the nimble Alloutte to possess a speed and range far beyond comparable piston engined models. From then on, it was clear that turbine power would be the future of helicopter design.

 

In the US, the first experiments for this type of helicopter propulsion were pioneered by Charles Kaman’s aircraft company. The first successful experiment was achieved through combining the Boeing 502 turbine with his company’s K-225. Kaman, a former employee of Sikorsky, would develop this new helicopter along with his head designer, Anton Flettner, a German engineer who pioneered the use of intermeshing rotors. The experimental K-225 proved promising enough to warrant further development, and soon, the Kaman Aircraft company would produce a new utility helicopter along its lines. The firm’s HH-43 Huskie fire fighting and rescue helicopter fit the bill, and its later models were equipped with turboshaft engines in the late 50s.

 

However, the firm’s greatest success was soon to arrive, when the navy sent out a request for a new carrier-borne, lightweight helicopter.

Seasprite

The US Navy’s request for a light multipurpose and rescue helicopter was soon met with Kaman’s newest design, the Kaman Seasprite. The helicopter would settle the requirements, being capable of carrying up to 12 people, remaining compact and fuel efficient, and taking up little space aboard aircraft carriers. In the 1956 competition, Kaman’s design won handily and the next year saw a contract issued for procurement. The helicopter was the first Kaman design to feature a single main rotor, and in conjunction with the servo-flap rotor system, it was cutting edge, reliable, and possessed smooth flight characteristics.

The design, then named HU2K, first flew on July 2, 1959, and was introduced fully in December 1962. It proved to be robust with good handling, however, the single General Electric T58GE turbine left it fairly underpowered. This prevented it from taking on any new missions, but it was sufficient for the basic role it was designed for. These helicopters, later designated UH-2A and UH–2B, though largely identical, were produced until 1965, with a total of 142 airframes built.

The Seasprites, supplied to utility helicopter squadrons, were distributed amongst US aircraft carriers and saw widespread use during the Vietnam War. There, they served largely as plane guards, where they took up a position alongside aircraft carriers when large scale air operations were underway. In case of an accident during take off or landing, the Seasprites would move in quickly to recover downed pilots. Search and rescue also fell under their purview, and alongside a number of other models, they pulled hundreds of airmen from the sea. As a fleet utility helicopter, they also flew ashore and between various vessels in order to transfer personnel and equipment. Medical evacuations were also among tasks these helicopters performed, moving injured personnel to ships with more substantial medical facilities. The small size and smooth controls of the Seasprite made landing on the basic helicopter facilities of most ships an easier affair compared to the bulkier Sikorsky Sea King. Its only drawback was the relatively little power offered by its small turbine engine. It could make for tricky takeoffs as the small helicopter was slow to climb.

In spite of it being underpowered, it proved to be a valuable asset to the fleet and was respected by its pilots. Naturally, the Navy wished for improved models. Kaman’s first move was to add a second turbine engine to the helicopter, the improved model being the UH-2C. As the production run had already been completed, the Navy sent Kaman the older A and B models back to the company in order to receive the upgrade. The C model was introduced in 1966, though now with its much higher speed and carrying capacity, it was soon deemed that the Seasprite was to take on a much wider scope of duties.

Sub Chaser

During the late sixties, the increased threat posed by ever more advanced models of submarines was of great concern to the US surface fleet. Even more concerning was a lack of long range anti-submarine weapons. While many ASW vessels did carry the ASROC missile, tipped with either a nuclear depth charge or a Mk 46 torpedo, there was some concern of submarines attacking from beyond the 6 to 8 mile range of this weapon. The existing long range anti-submarine weapon was the Gyrodyne DASH drone, a small drone helicopter capable of carrying depth charges and torpedoes. While it was compact, it was inflexible, and with no means of collecting additional data in the area of the suspected submarine, accuracy was very poor.

This left most of the US Navy’s light surface forces, which often operated too far from the carrier to be covered by its airborne ASW umbrella, under threat from more modern submarines. The solution was found in the re-engined Seasprite. The new SH-2D represented the greatest change thus far, with the new aircraft sporting a chin mounted surface search radar, a rack to carry a Mk 46 lightweight torpedo, and a 15 chute sonobuoy rack. The small size of the helicopter would allow it to operate aboard some of the lightest frigates in the fleet, these being the Garcia-class.

The performance of the helicopter, and its ability to operate on nearly every major surface combatant, would see this mission expanded even further. Thus came the Light Airborne Multi-Purpose System, a fleet-wide program to equip most warships with helicopters in order to boost their anti-submarine and anti-surface capabilities. LAMPS I would place a now standardized SH-2F aboard nearly every frigate, destroyer, and cruiser in the fleet. In addition to the long standing utility missions, the helicopters were datalinked to their host ship to allow them to prosecute possible submarine contacts, provide long range surface surveillance, and allow for more effective over the horizon targeting of enemy surface threats.

The new SH-2F was largely the same as the proceeding UH-2D model, though it standardized the use of composite rotor blades which existed on some previous models, and its tail wheel was moved forward to enable it to better operate off of smaller ships. Some 85 Seasprites were converted to this type, and a further 48 were produced in the early 80s in order to cover a shortfall before the introduction of the SH-60B Seahawk. The new, standard LAMPS helicopter entered service in 1973.

LAMPS I

The LAMPS I program vastly increased the offensive and surveillance capabilities of participating vessels. This encompassed some half dozen ship classes ranging from the workhorse frigates of the fleet, such as the Knox and Oliver Hazard Perry, to the nuclear guided missile cruiser, Truxton. In the ASW mission, on detecting a suspected submarine, whether attacking or transiting, the ship would launch its SH-2F. Capable of using sensor data from the ship, the helicopter would move in and begin to deploy its sonobuoys, being either passive AN/SSQ-41’s or active AN/SSQ-47’s. The helicopter then relayed the sonobuoy data back to the ship for processing, and if the contact was found and classified, the helicopter would move in to attack with its Mk 46 torpedo. The onboard magnetic anomaly detector could also mark the position of a submarine if over flown by the helicopter. A ship equipped with ASROC could also join the helicopter in the attack, provided the target was in range. In the ASW role, the helicopter was a largely reactive measure, as it was unable to process its own sonobuoy data and lacked a dipping sonar, and thus required other platforms to detect the submarine first. This is not to say it lacked considerable offensive potential, as the powerful hull mounted sonar arrays aboard the Knox class frigates and Spruance class destroyers, and the OHP’s short range but highly sensitive sonar, were among the most advanced systems of their kind and could give early warning to submerged threats. The presence of the helicopter thus allowed ships to prosecute, classify, and engage submerged contacts that would otherwise be beyond the effective range of their sensors and weapons.

The Spruance class in particular could prove very dangerous to submarines at range thanks to its convergence zone sonar. The AN/SQS-53 could make use of the aforementioned phenomenon, and under ideal conditions, detect submarines at extreme ranges. These zones are where sounds are bounced off the seafloor or thermal layers into a concentrated area and are thus made dramatically louder. Convergence zones are exploited by all ASW vessels, though the specialized sonar aboard these ships allowed them to exploit sound propagated at distances far in excess of the norm. A Spruance class ship making use of a convergence zone could dispatch helicopters against submarines potentially dozens of miles away, making them among the most capable ASW vessels of the Cold War. In the absence of a convergence zone, it switched to a short to medium range mode. It shared this system with the Ticonderoga class guided missile cruiser, and the Kidd class destroyer, both of which used the same hull, however their role was air defense. These ships all transitioned to LAMPS III once it became available in the mid 1980s.

The LAMPS system featured most prominently in escort and screening vessels, namely the Knox and Oliver Hazard Perry (OHP) class frigates. The Knox class was an anti-submarine frigate with limited anti-surface capability that entered service in 1969, with 46 vessels being commissioned in all. These ships carried a single Seasprite and were armed with an ASROC launcher, which later received the capability to launch Harpoon anti-surface missiles. The OHP class carried no ASROC launcher, though they instead carried two helicopters. The last 26 of the class were LAMPS III ships and carried the heavier and more capable Sikorski Seahawk. In place of the ASROC launcher was a Mk 13 mod 4 launcher for Standard missiles and Harpoons. Both frigates carried hull sonar and towed arrays, the Knox possessing a larger hull array, and the OHP carrying a short range, high resolution hull sonar system, with a towed array being used for longer range surveillance. The difference in systems was due to the OHP being designed as a fast escort, and needed the capability to conduct passive sonar searches at speeds faster than a typical surface group. The resulting hull sonar system was thus highly sensitive, but had a decreased maximum effective range.

In addition to the added anti-submarine mission, the Seasprite performed anti-surface support and anti-ship missile defense roles. In performing these missions, the Seasprite used its search radar to track and identify potentially hostile surface vessels. This allowed the host vessel to build a picture of enemy forces while putting itself in comparatively little direct danger. With this information, any LAMPS I vessel had early warning against potentially hostile surface vessels, and could also use the relayed information to more accurately fire Harpoon and Standard missiles over the horizon, without using its own radar and revealing itself. The extended surveillance range of a LAMPS vessel was pushed beyond 170 miles with the use of the Seasprite.

LAMPS I thoroughly improved the anti-submarine and anti-surface capabilities of much of the US fleet, with the Seasprite itself being an almost perfect off the shelf solution. While there were limitations, like the inability to perform an independent ASW search, the overall benefit of the ship not needing to prosecute sub surface contacts alone or having to reveal itself to perform a radar search in its patrol area was well worth the resources devoted to the Seasprite.

Late Career

By the end of the Cold War, the Seasprite had incorporated a number of improvements. These comprised a number of on board and weapon systems, perhaps most notably the introduction of the Mk 46 Mod 5, or NEARTIP, lightweight torpedo. The new model was designed to counter the latest advancements in Soviet nuclear submarine design, with the torpedo possessing an improved engine to make for a higher speed, an improved sonar transducer to increase the effective detection range of the weapon and add better countermeasure resistance, and had a new guidance and control group. The new weapon entered service in 1979, with kits being produced to convert old stocks to the new standard.

An improved model of the helicopter equipped with T700-GE-401 engines was also developed in 1985, though few were procured, as the Navy sought to increase supplies of the SH-60 Sea Hawk. Some of the improvements from the scaled back Super Seasprite did however make their way into the SH-2F. A number of LAMPS I helicopters during the mid 80s were equipped with FLIR pods for IR searches, IR jammers, chaff and flare dispensers, and an infrared sea mine detection system. Their service during the Gulf War saw them mostly perform ship to ship material and personnel transfers, mine detection, and medical evacuation roles, as Iraq possessed no submarines. Their primary mission in the theater was mine hunting duties, for which they used IR sensors in their search. They were only carried aboard lighter surface combatants during Operation Desert Storm, and weren’t present among the air wings of any of the aircraft carriers during the conflict.

After almost thirty years of service, the SH-2F was withdrawn along with most of the vessels that carried them. Its end was hastened by the withdrawal of the Knox class frigates from service and the sale of most of the short hull OHP frigates to foreign navies. The Navy would fully transition over to the Sikorsky Seahawk, a much larger and more powerful helicopter which carried two torpedoes, a dipping sonar, and incorporated sonobuoy processing capabilities.

Construction and Flight Characteristics

The Kaman SH-2F Seasprite was compact, and while conventional for a modern helicopter, was very advanced for its day. Its fuselage was watertight, possessed forward retractable landing gear, and was equipped with a variety of onboard sensors. While it could not perform waterlandings, its sealed canopy allowed it to float until the helicopter’s crew could be recovered. The pilot sat on the port side of the cockpit and the copilot/tactical coordinator, who operated the weapon systems, was seated starboard. The systems operator sat behind the pilot and operated the sonobuoy dispenser, the magnetic anomaly detector, and radar system. The systems operator lacked the equipment to process the sonobuoy data, which was instead processed aboard the LAMPS I host vessel and sent back via a data link.

At the nose of the helicopter was the LN-66 surface search radar, designed for detecting both surface vessels and submarine snorkels. On the starboard pylon was the MAD streamer which worked in conjunction with an extendable antenna on the underside of the helicopter. This system worked by measuring the local strength of Earth’s magnetic field, and would spike if it encountered a large magnetic object, or in other words, a submerged submarine. Triggering a readable detection required the aircraft to over fly the contact and was thus typically used to pin the exact position of the submarine while preparing to attack after closing in during the sonobuoy search. The Seasprite carried a mix of AN/SSQ-41A passive and AN/SSQ-47B active sonar sonobuoys. The AN/SSQ-41A omni-directional passive sonobuoys operate at a depth of 60 ft for shallow searches and 300 ft for deep, and have a frequency range of 10 Hz to 20 kHz. Depending on their settings, they lasted between one to eight hours. The SSQ-47B active sonobuoy provided ranging information and operated at either 60 or 800 ft and possessed a maximum endurance of thirty minutes. Sonobuoy data was processed aboard the supporting ship and was used to localize submarine contacts that were otherwise too distant or quiet to be effectively tracked by the ship’s sensors alone. The information provided from the data link allowed the helicopter to detect, classify, and engage subsurface contacts in cooperation with the host vessel.

Re-detecting a submarine at longer ranges from the ship was difficult, as passive sonobuoys laid out in a large search pattern gave little chance of success. The best chances of re-detection on a lost contact was when it was near the surface, transiting, or maneuvering to avoid attacks from other vessels and aircraft. The standard procedure for sub chasing was to head down the azimuth of the ship’s sonar contact and to begin to lay a sonobuoy field to uncover its exact location.

The Seasprite was initially powered by a single General electric T58-GE-8F turboshaft before a second was installed on the UH-2C. These each produced up to 1,350 shp and allowed the SH-2F to travel at a top speed of 152 mph at sea level and allowed the small helicopter to carry up to 2000 lbs worth of equipment in the vertical replenishment role, with a maximum cargo hook capacity of 4000 lbs. To save fuel during emergencies, the helicopter could run on one engine on the way back to the ship. These engines were well regarded and considered very reliable.

The helicopter’s lift was provided by a 44 ft main rotor which used composite blades which were directed with servo operated flaps. These flaps are easily visible on the rotors, each having a wider chord than the rest of the blade. The flap is used to change the angle of attack of the rotor in flight and allows for smooth altitude adjustment. The anti-torque rotor at the rear of the helicopter had its blades increased from three to four going from the C to D model. The Seasprite handled well and was easy to perform a hover in, an important capability when it comes to search and rescue, and transfers to vessels without any landing areas. This was particularly important when landing on Knox class frigates, which both had significant air disturbance aft of the ship, and a very claustrophobic landing area.

In the air rescue role, the copilot would coordinate with divers and rescue crew. The cargo space of the helicopter could fit two stretchers or three seats. For water recovery of personnel, divers were carried aboard and recovered downed airmen through the use of a rescue hoist mounted on the starboard side of the helicopter. Mechanically driven, it had a capacity of 600 lbs.

The Seasprite could carry a variety of unguided weapons, but rarely carried anything other than the Mk 46 torpedo, being either the Mod 0, or Mod 5 NEARTIP during the 1980s. On paper, the Seasprite could carry two torpedoes, but in practice, the second equipment position was taken up by an external fuel tank on ASW patrols. Both torpedo types measured 8.5 ft long with a diameter of 12.75 inches. The Mod 0 weighed 568 lbs, and both carried a 95 lb warhead. The Mod 0 possessed a maximum speed of 45 kts, with the NEARTIP being considerably faster. The NEARTIP provided better tracking of faster targets and better countermeasure rejection, having incorporated a new sonar transducer, control and guidance group, and a new engine which switched from solid propellant to liquid monopropellant. Prior to the introduction of the Mod 5, there was little hope for successful attacks against the fastest nuclear submarines of the 1970s. However, in confirming the location of a submarine, its position also became revealed to long range ASW aircraft which could make follow up attacks.

Other weapons included unguided 2.75 inch unguided rockets, and some rare, late examples possessed FLIR optics and could carry AGM-65 Maverick missiles. These weapons, however, were rarely ever carried. Later Seasprites carried a variety of countermeasures including an ALQ-144 tail mounted IR jammer and an ALE-39 flare and chaff dispenser. A considerable number of these helicopters were equipped with infrared jammers and flares during the 1980s.

Conclusion

The Kaman Seasprite can be said to be among the most versatile aircraft ever operated by the US Navy. Entering service as a plane guard, the number of roles it served grew considerably over the years to encompass everything from medical evacuation, to anti-submarine duties. As the core of the LAMPS program for nearly 10 years, it gave US warships a boost in their offensive and defensive qualities against both surface and subsurface opponents.

Specification

SH-2F Seasprite	Specification
Engine	2x General Electric T58-GE-8F
Output (maximum)	2300 SHP (2700 SHP)
Maximum Weight	12800 lbs
Empty Weight	8652 lbs
Range for Utility	234 N.MI
Radius of Action for Utility	111 N.MI
Endurance for Utility (ASW) [Ferry]	2 hours (1.9 hours) [2.8 hours]
Standard Armament	1 Mk 46 Mod 0/5 Lightweight torpedo
Crew	Pilot, copilot/tactical coordinator, systems operator
Length of fuselage	40.5 ft
Width of fuselage	10 ft

Designation	Sub type
HU2K/UH-2A	Basic single engine utility helicopter
UH-2B	Minor differences in avionics, later made identical to A model
UH-2C	First two engine model
H-2	Army project, single engine
HH-2C	Combat rescue model, 7.62 side door gun emplacements, M134 rotary gun turret. Two engines.
HH-2D	Same as HH-2C but without armament. Used to test ASW equipment and loading. Two engines.
NUH-2C/D	Test helicopter, two engines.
YSH-2E	Testing helicopter for radar and ASW gear for canceled LAMPS II program
SH-2D	Early ASW model
SH-2F	Standard LAMPS I helicopter
SH-2G	SH-2F with T700 turboshaft engines, improved avionics. Small production run.

Avionics	Type
Surface Search Radar	LN-66HP
IFF	AN/APX-72
Transponder Computer	KIT-1A/TSEC
UHF Radio Set	AN/ARC-159
Secure Speech	KY-28
ICS	AN/AIC-14
TACAN	AN/ARN-52
Doppler Radar	AN/APN-182
Attitude Heading	AN/ASN-50
NAV Computer	AN/AYK-2
Plotting Board	PT-492
UHF Direction Finder	AN/ARA-25
OTPI	R1047A/A
Radar Altimeter	AN/AP-171
RAWS	AN/APQ-107
Sonobuoy receiver	AN/ARR-52
Acoustic Data Processor	AN/ASA-26B
Data Link	AN/ASK-22
Magnetic Anomaly Detector	AN/ASQ-81
Radar Warning Receiver	AN/ALR-54

Profile:

Gallery:

 

Credits: 

• Article written by Henry H.
• Edited by  Stan L. and Henry H.
• Ported by Henry H.
• Illustrations by Godzilla

Sources

Primary:

Standard Aircraft Characteristics Navy Model SH-2F aircraft. NAVAIR 00-110AH2-8. Commander of the Naval Air systems Command. July 1974.

Andrews, Harold. Sea Sprite. Naval Aviation New 1983 (Feb).

Naval Aviation News 1985 (May-June)

Naval Aviation News 1983 (Jan-Feb & May-Aug)

Department of Defense authorization for appropriations for fiscal year 1982 : hearings before the Committee on Armed Services, United States Senate, Ninety-seventh Congress, first session, on S. 815.

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Department of Defense authorization for appropriations for fiscal year 1986 : hearings before the Committee on Armed Services, United States Senate, Ninety-ninth Congress, first session, on S. 674.

Department of Defense authorization for appropriations for fiscal year 1979 : hearings before the Committee on Armed Services, United States Senate, Ninety-fifth Congress, second session, on S. 2571

Department of Defense authorization for appropriations for fiscal year 1980 : hearings before the Committee on Armed Services, United States Senate, Ninety-sixth Congress, first session, on S. 428.

CDR Rausa Rosario. LAMPS MK III. Naval Aviation News 1980 (June).

Defense Department authorization and oversight hearings on H.R. 5167, Department of Defense authorization of appropriations for fiscal year 1985, and oversight of previously authorized programs before the Committee on Armed Services, House of Representatives, Ninety-eighth Congress, second session.

Secondary:

Polmar, Norman. Ships and Aircraft of the U.S. Fleet. Fifteenth Edition. US Naval Institute Press. 1993.

Sikorsky HNS-1 “Hoverfly”. United States Coast Guard.

Stuyvenberg, Luke. Helicopter Turboshafts. University of Colorado at Boulder, Department of Aerospace Engineering. 2015.

Garcia Class Frigate. NAVsource online.