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Sikorsky S-58 / H-34 / HSS / Seabat / Seahorse / Choctaw
Westland Wessex

UH-34D

Designed to overcome the range and offensive payload deficiencies of the anti-submarine HO4S version of the S-55 / H-19, the Sikorsky S-58 was developed to a US Navy order for a prototype XHSS-1 placed on 30 June 1952. The nose engine position was retained for the 1525hp / 1137kW Wright R-1820 engine, but a completely new semi-monocoque fuselage, larger-diameter four-bladed main and four-bladed tail rotors, and transmission system were introduced, together with main rotor and rear fuselage folding to facilitate shipboard stowage. The tail rotor has servo control and both main and tail rotors have brakes. Fuel capacity is from 750 litres to 1,164 litres depending on model.

With a completely redesigned, downward-sloping tail section, the S-58 also differed from the S-55 in having a three-point, tail-wheel landing gear. Air-oil shock-absorber struts. Mainwheels have rotating struts to reduce drag and weight and toe-operated brakes. Tailwheel is fully castoring and self-centring, with an anti-swivelling lock. Mainwheel tyres 11.00 x 12. Tailwheel tyre 6.00 x 6. Toe-operated mainwheel brakes. Track 3.66m. Wheelbase 8.75m.

Pilot's compartment above main cabin seats two side by side with dual controls. Cabin normally seats 12 passengers. Up to eight stretchers can be carried. Sliding windows of pilot's compartment removable in an emergency. Cabin and cockpit air conditioned and soundproofed.

Designated XHSS-1, it flew for the first time on 8 March 1954.

The first production HSS-1 flew on 20 September 1954, and the type became operational in August 1955. Now designated SH-34G, it has the name Seabat and carries either dunking sonar search equipment or weapons for attacking submarines. Later Seabats includes the 'winterised' LH-34D (formerly HSS-1L). These models in U.S. Navy service were replacement by the SH-3 Sea King and many were converted to utility transports with UH prefixes.

The HSS-1N (SH-34J) was developed for night operations, equipped with Doppler for navigation, automatic stabilisation and automatic hover coupler, while a single HSS-1F (SH-34H) flown on 30 January 1957, was powered by two General Electric T58 turboshafts. In 1960 five HSS-1Z (VH-34D) helicopters joined the Executive Flight Detachment for Presidential and VIP transport duties. Seabats stripped of ASW equipment for utility duties were designated UH-34G and UH-34J.

In 1959 a US Marine Corps HUS-1 served as a launching platform for the Martin Bullpup air-to-surface missle during a series of tactical assault trials at Chesapeake Bay.

The Bullpup was claimed to be the largest radio-controlled missile ever fired from a helicopter.

A troop transport variant was simultaneously acquired by the Marine Corps as the HUS Seahorse. One example of this type was loaned to the Army for service test and evaluation. The Army had placed preliminary orders for production H-34A troop transport variants of the Navy XHSS-1 in April 1953 and the performance of the borrowed Marine Seahorse, essentially identical to the H-34 version, confirmed the Army's belief that the type would be a vast improvement over the H-19s then in service.

The US Marine Corps ordered the HUS-1 Seahorse (UH-34D) version on 15 October 1954; able to carry 12 Marines or a 1350kg load, this variant entered service in February 1957. The Marines received about 500 of the S-58 in the utility version (HUS-1 / UH-34D and -1A) and have used the type since 1957 primarily for utility transport and for recovery duties connected with the U.S. satellite programme. The 12-passenger UH-34D and UH-34E (formerly HUS-1 and HUS-1A / UH-34E) are basically alike, the latter being an amphibious version with pontoons for landing on water. Inflatable flotation gear identified the US Marines' HUS-1A and the US Coast Guard's HUS-1G (HH-34F). Four HUS-1L (LH-34D) helicopters were modified for operation in the Arctic.

A total of 603 S-58s were delivered to the US Marines.

The US Army ordered several hundred H-34A, H-34B and H-34C Choctaw helicopters powered by 1063kW R-1820-84 engines and each carrying 16 troops or eight stretchers in the medevac role.

The Army accepted the first of 437 new-construction H-34As in April 1955, the first unit being equipped in September 1955. An additional twenty-one HUS-1 aircraft transferred from the Marine Corps during Fiscal Year 1955 were also designated H-34A (though at least five further USMC Seahorses operated by the Army between 1955 and 1957 retained their original Navy Bureau numbers).

In 1956 an early production example flown by Army Captains Claude E. Hargett and Ellis Hill set new world helicopter speed records on courses of 100, 500 and 1000km.

The H-34A was also the first helicopter judged safe enough for routine use by the U.S. President, and in 1957 the Army organized an Executive Flight Detachment equipped with specially modified Choctaws. These aircraft were fitted with extensive soundproofing, plush VIP interiors, and upgraded communications equipment, and were designated VH-34A.

The US Army H-34A, H-34B and H-34C Choctaw helicopters were powered by 1063kW R-1820-84 engines and each carrying 16 troops or eight stretchers in the medevac role. US Army CH-34s maintained a constant patrol along the border of West Germany with Czechoslovakia and East Germany. Army S-58's have the name Choctaw, the CH-34A and CH-34C differing only in the equipment carried.

In 1960 Sikorsky began modifying Army H-34As (and Air Force H-34As and -Bs) to -C model standard through the addition of automatic flight stabilization systems and other detail changes including relocation of Battery, Invertors, and Aux Hyd Reservoir. By January 1962 the Army had 190 H-34Cs and 179 H-34As in its inventory; under the Tri-Service designation system introduced later that year the aircraft were redesignated as, respectively, CH-34C and CH-34B. Several -C model aircraft were subsequently modified to VH-34C standard for VIP transport duties. The VH-34D is a VIP transport.

In 1964 U.S. Marines flying the HUS-1 version of the S-58 saved 1,500 Vietnamese villagers from floodwaters. The aircraft also was used to recover the space capsule of Alan B. Shepard, Jr., America's first astronaut in space.

Sik-HSS-1
HSS-1

The CH-34 did not see extensive Army service in Vietnam. The Army's 1962 decision to deploy the Vertol CH-21 Shawnee to Southeast Asia instead of the faster and more capable Choctaw was based on two considerations. First, in accordance with then-current Army doctrine regarding the area-standardization of aircraft types, the CH-21 was already widely deployed in the Pacific area and the continental United States, whereas all but about thirty of the Army's CH-34s were based in western Europe. US Army CH-34s maintained a constant patrol along the border of West Germany with Czechoslovakia and East Germany. It was therefore logical and logistically preferable that the CH-21, which was considered acceptable if somewhat past its prime, should be chosen for deployment to Southeast Asia. The Army's second reason for sending the Shawnee rather than the Choctaw was a somewhat negative opinion of the Choctaw's combat survivability, a belief based on French experience in North Africa. French forces had used both the CH-21 and the CH-34 in Algeria, the former flown by the Army and Air Force and the latter by the Navy, and official evaluations had indicated that the Shawnee was more likely to survive multiple hits by ground fire than was the CH-34. The French belief that the location and 'fragile' construction of the Choctaw's fuel tanks made the craft extremely vulnerable to ground fire seemed to validate the U.S. Army's decision to deploy the Shawnee to Vietnam pending the introduction into widespread service of the UH-1 Iroquois. The approximately twenty Army H-34s that did eventually reach Vietnam proved no more vulnerable than any other aircraft in the theatre, however, and ably carried out missions ranging from combat assault to aeromedical evacuation and general cargo transport. Most of these twenty aircraft were turned over to the South Vietnamese during the course of the war, though a few were ultimately reclaimed by the Army prior to the final collapse of the Saigon Government.

The CH-34 Choctaw remained in frontline Army service well into the late 1960s, and was standard equipment in many Army Reserve and National Guard aviation units for considerably longer. The last Choctaw was not officially retired until the early 1970s, by which time the type's duties had been divided between the UH-1H Iroquois and the CH-47 Chinook.

The commercial S-58B and S-58D are passenger/cargo transport helicopters comparable with their military counterparts. The 12-seat airline version, certificated by the FAA in August 1956, was built for Chicago Helicopter Airways (eight), New York Airways (three) and Sabena (eight). First commercial deliveries of S-58C were made in 1956-57.

Sikors-S58-01

Substantial numbers of military S-58 variants have been exported, and in mid-1967 were serving with the Federal German Army (one hundred and forty-four); the navies of Argentina (five), Brazil (five), France (twenty-six), Germany, Indonesia, Italy (eighteen), Japan (fourteen) and the Netherlands (twelve); and the air forces of Belgium (nine), Cambodia (three), Canada (four), France (one hundred and ten), Germany, Israel (twelve), Thailand (twenty) and South Vietnam (sixty). Those in French and Belgian service were manufactured in France by Sud-Aviation.

Production of the S-58 ended in December 1965 after one thousand seven hundred and sixty-six had been built by Sikorsky, but started again to fulfil additional U.S. orders and one from the Italian Navy for six SH-34J's.

In January 1970, Sikorsky announced the design of kits for the conversion to turbine power by the installation of the Pratt & Whitney PT6 Twin-Pac. First flight of the S-58T took place 19 August 1970 and in April 1971 Sikorsky received FAA approval for the S-58T PT6A Twin Pac-powered turbine conversion for H-34 airframes. One hundred and forty-six conversions, or conversion kits, were produced until, in 1981, the rights were sold to California Helicopter International. Since then customers for the California Helicopter (Sikorsky) S-58T included New York Airways, the Indonesian and South Korean air forces (now retired) and the government and air force of Thailand. The S-58T is also in service in Argentina with the Presidential Aircraft Squadron. Small numbers were built of S-58B and S-58D civil passenger and cargo transport helicopters, a 12-seat airline version being operated by Chicago Helicopter Airways, New York Airways and SABENA. When he checked in for a Sabena S-58 flight, Igor Sikorsky was asked if his name was spelt like the helicopter's.

When production was terminated in January 1970, Sikorsky had manufactured a total 1,820 S-58s of all versions.

The S-58T is a turbine conversion of the normally piston engined military H-34, or civilian S-58, with the Curtiss-Wright R-1820 piston radial engine removed from the nose and replaced by a pair of turbines fas-tened to a common drive transmission as the PT6T Twin Pac.

The PT6T Twin Pac unit fitted to the S-58T is basically two PT6 turboshaft engines mounted side-by-side and driving into a combining gearbox. Of the total 1800 shp available, only 1505 shp can be absorbed by the transmission during take-off and for continuous operations this is limited to 1254 shp. Should one engine fail, sensors automatically increase the good engine’s output up to the maximum 900 shp. Fuel is carried in 12 under-floor cells.

The useful load rose about 200 pounds on the Standard S-58T, it actually went down by some 80 pounds on the Mark II version, which has airline seating and win-dows. This increased power from 1,525 hp to 1,875 shp. Since the basic rotor-blade system has been retained, there would also seem to be a speed handicap there that no amount of extra power could overcome.

By 1975 more than a hundred S-58Ts had been delivered or are under contract, more than half of them in the form of retrofit kits.

Sik-S58-T-1
S-58T

The S-58T was first flown on 26 August 1970 with P&WC PT6T-3 twinpack turboshaft engine. Kits were built by Sikorsky but 160 conversions were carried out by California Helicopter International.

Sik-S58-T-2
S-58T

Offering a 5,000-pound sling load, the Sikorsky S-58T has a 110 knots normal cruise, a 10-knot edge on both the 212 and the 205A. Furthermore, while all three aircraft can hoist a 5,000-pound sling load, the -58T can do it at higher altitudes. The S-58T manages a gross lift at 6,500 feet.

When properly equipped, it's IFR for two. Outsized wheel hubcaps house automatically inflatable bubbles for inadvertent oceanic dunking. With an engine out, though, the aircraft can hold onto a service ceiling of 4,300 feet.

While it turns out that the 430-pound weight saving gained by substituting the twin turbines for the old recip engine was pretty well swallowed by updating modifications, there was no loss of range with the same 283 gallons of fuel. Though the new turbines consume an extra 22 gph in cruise, the higher 110-knot cruise (versus 85 knots for the piston model) yields almost exactly the same 243-nm range at sea level.

Furthermore, the hovering altitude in ground effect on a warm day (ISA + 20) went way up from 2,600 feet in the piston model to 7,700 feet in the S-58T.

Whereas the "old" rotor-blade system the -58T is saddled with might have seemed a handicap, the engineers at Sikorsky finessed their way around that by smoothing out the vibration levels, and that, in turn, permitted the boost in cruise speed, rather than the addition of brute power.

Instead of adopting the "Nodamatic" vibration-damping technique used by Bell, where the cabin is "suspended" at harmonic vibration points, Sikorsky used something called a Bifilar vibration absorber. This consists of weights fastened to the main rotor hub between the rotor blades - more specifically, "pendular dynamic masses." The 120-pound installation not only pro-vides a five-to-one reduction in vibration levels, according to Sikorsky engineers, but it greatly reduces tail stresses, mechanical failures and overall maintenance.

In addition to the California Helicopters version, Orlando Helicopters also offers S-58 conversions. An S-58 Heli-Camper, similar in fit to the OHA-S-55 Heli-Camper is available, powered by a Wright Cyclone R-1820-84 engine. A further Orlando S-58T conversion is the Orlando Airliner, an 18-seat all-passenger version with nine additional tinted windows fitted on each side of the cabin. By 1997 nearly 30 conversions have been completed.

Total of 166 also produced under licence by Sud-Aviation in France. Sud-Aviation were completing two modified examples of the Sikorsky S-58, each of which was fitted with a 1900shp Turbomeca Bi-Bastan shaft turbine engine, and the first of these machines flew on 5 October 1962. The S-58 development was not pursued.

After acquiring a licence in 1956 to manufacture the Sikorsky S-58 helicopter, Westland imported one of these aircraft in HSS-1 configuration. Given the British serial number XL722, this aircraft was test-flown for a time with its original 1525hp Wright R-1820-84 engine before being modified to accept a 1100shp Napier Gazelle NGa.11 gas turbine.

Napier Gazelle powered Wessex first flight 17 May 1957 at Yeovil

In its new form it was flown for the first time on 17 May 1957, and was later joined by two pre-production Wessex HAS Mk.1's for Naval trials; the first of these flew on 20 June 1958.

Wessex features - Main and tail rotor each have four blades. Blades attached to hub by taper bolts. Main rotor blades fold manually. Rotor brake fitted. Shaft drive to main rotor through double epicyclic gear. Shaft drive to tail rotor through intermediate and tail gearboxes. Tail end folds to port and forward for stowage. Tail rotor carried at tip of vertical stabilising fin. Small horizontal stabiliser inset in leading-edge of fin.

All blades of light-alloy extruded spar and light-alloy bonded trailing-edge structure. The fuselage is a light-alloy semi-monocoque structure, with steel tube support structure for main rotor gearbox.

Landing gear is a non-retractable tailwheel type. All three units fitted with Westland oleo-pneumatic shock-absorber. Dunlop wheels, tyres and hydraulic disc brakes. Tubeless treaded mainwheel tyres, size 6.00 x 11. Tailwheel tyre size 6.00 x 6.

Compressor bleed air for heating. Ambient air circulation by fan. High-pressure hydraulic system for powered flying controls and 272kg capacity hoist. 24V DC electrical system, with two 6kW generators.

The HAS Mk.1, powered by a Napier Gazelle of 1,450shp (1081kW), went into production in 1959 for the Royal Navy as a submarine search and strike helicopter equipped with dipping Asdic and provision for one or two homing torpedoes. Powered by a 1450shp Gazelle Mk.161 engine, it began service trials with No.700H Flight in April 1960 and has since been delivered to Nos. 706, 737, 771, 815, 819 and 848 Squadrons. The first of these to commission, in July 1961, was No.815; the Wessexes of No.848 Squadron were for commando assault duties aboard H.M.S. Albion, having the ASW gear removed to make room for 16 troops or 8 stretchers and a medical attendant in the main cabin. Alternatively, a slung load of 1814kg can be suspended from an under-fuselage hook.

The original version was the Wessex HAS.Mk1, powered by a Napier Gazelle of 1,450shp (1081kW). The HAS.1 was undergoing service trials with No.700H Sqn during 1960, during which it first landed on an aircraft carrier.

The HAS.1 was supplanted by the Wessex HAS.Mk3 version popularly called the Camel because of its humpbacked search radar above the rear fuselage.

HAS.1

The most extraordinary feature of the Wessex HAS.3 is the stack of avionics and anti-submarine gear that the Royal Navy has fitted it with; the latter consisting of radar and sonar equipment linked together by a small computer to give a “total picture”. All this is operated by a third crewman seated at the rear of the aircraft, in an area which looks like a second cockpit. The sophisticated radar is used for navigation as well as sub hunting.

In August 1964 it was announced that the Iraqi Air Force was acquiring 12 Wessex HC.2. The cost was to be $8m including spares. The Ghanaian air force ordered two Wessex Mk.53.

Much more important numerically is the Wessex HU.Mk 5 version, the Royal Marine Commando assault version. These twin-engine machines once numbered almost 100. The Navy's HU Mk.5, for which two orders were placed, entered service in summer 1964 as a commando-carrier assault transport.

In the early 1960s the RAF required a powerful general-purpose helicopter capable of troop-carrying, air ambulance and ground attack roles.

Following the first flight of the true prototype (XR588, this being preceeded by one of the Royal Navy pre-production variants which was later partly converted to an HC.2 version) on 5 October 1962, seventy-one examples of the Wessex HC.2 variant were delivered to the RAF, which first entered RAF service with No.18 Squadron, based at RAF Odiham, Hampshire, in January 1964, replacing the Whirlwind and Belvedere types. The HC Mk.2 was built as a transport helicopter for up to 16 troops, with redesigned gearbox and strengthened airframe.

And doors on each side of flight deck and on starboard side of cabin. Two flexible fuel tanks under cabin floor, total capacity 1,409 litres. Provision for carrying two 500 litre auxiliary tanks in cabin for ferry purposes. Refuelling point in starboard side of fuselage. Oil capacity 9 litres per engine, 19 litres in main gearbox.

Towards the end of 1959 two Whirlwinds joined the Queen’s Flight, designated HCC Mk.8, they had Alvis Leonides Major engines and special interiors.

HCC Mk.8

Westland Wessex HC Mk.2

In 1968 Westland Helicopters received an order for two Wessex aircraft to equip The Queen's Flight. These were designated HCC4. The aircraft were built to HC2 standard but with the main cabin having a VIP interior finish, furnishings and sound proofing plus an external folding step below the cabin door. Additional Decca navigation equipment was installed on the flight deck. The first flight took place on 17 March 1969. The first official flight was on 1 July 1969 in support of the Investiture of the Prince of Wales at Caernarfon Castle, Wales. The helicopters in their distinctive red/dark blue paint scheme operated for many years from RAF Benson. From 31 March 1995 they moved to RAF Northolt and became part of No.32 (The Royal) Squadron.

The Wessex HCC4 was retired in 1998 and No.32 (The Royal) Squadron gave up the task of providing helicopters for the Royal Family.

A commercial version was known as the Srs.60.

The RAAF ordered 27 Westland Wessex Mk31B carrier-borne anti-submarine/search & rescue helicopter from Westland Aircraft Ltd in July 1961. The first was delivered on 1 Nov 1962 and the last on 4 Nov 1963. The HAS Mk.31's are similar to the HAS Mk.1 apart from their 1540shp Gazelle Mk.162 engines. Australia's navy anti-submarine duties started in August 1962.

Westland built 356 Wessex in all (including those for the civil market): the HAS Mk.1 version for the Royal Navy; the HC Mk.2 tactical transport version for the RAF; the HAS Mk.3 antisubmarine version with 1550shp Gazelle NGa.18 turbine; the HU. Mk.5 for various roles on the Navy's commando carriers; the HAS Mk.31 for the Royal Australian Navy; the Wessex Mk.52 for the Iraqui Navy (12); the Wessex Mk.53 for Ghana (3); the Wessex Mk.54 for Borneo and the Wessex Mk.60 commercial version. Seven Wessex Mk.60's have been built for Bristow Helicopters Ltd. These are 10-passenger commercial equivalents of the Mk.2 and operate in support of the oil and gas drilling rigs in the North Sea.

Gallery

Versions:

CH-34A/H-34A Choctaw

Transport and general purpose helicopter for US Army.

CH-34C (formerly H-34C) Choctaw

Similar to CH-34A, but with airborne search equipment.

LH-34D (HSS-1L)

Winterised version of Navy Seabat.

SH-34G (HSS-1) Seabat

Anti-submarine version ordered by US Navy 30 June 1952; accepted for service in February 1954.

SH-34J (HSS-1N) Seabat

Improved version of SH-34G.

UH-34D (HUS-1) Seahorse

Utility version for Marines; ordered 15 October 1954 and accepted for service January 1957.

UH-34E (HUS-1A) Seahorse

Version with pontoons for emergency operation from water.

VH-34D (HUS-1Z)

VIP transport version of Seahorse.

S-58B

Commercial passenger/freighter version.

S-58C

Commercial passenger-carrying version with two doors on starboard side of cabin.

S-58D

Commercial passenger/freighter version.

S-58T

Turbine conversion with Pratt & Whitney PT6 Twin-Pac, comprising two PT6 engines and combining gearbox; improved performance includes greater speed and lifting power, and better hot-and-high operation.

Westland Wessex HAS. Mk 1

Initial production version, developed for the Royal Navy, with one 1,450shp Napier Gazelle 161 turboshaft engine. Re-engined with a 1,100shp Gazelle NGa.11, flew for the first time 17 May 1957.

Westland Wessex HC. Mk 2

High-performance development of the Mk 1 with two coupled 1,350shp Bristol Siddeley Gnome Mk 110/111 turboshaft engines. Power limitation of 1,550shp at rotor head. Prototype converted from Wessex 1, flew for the first time 18 January 1962, and the first production model (XR588) 5 October 1962.

Westland Wessex Mk 3

Similar to Mk 1, but with 1,850shp Gazelle NGa.18 165 turboshaft engine.

Westland Wessex HCC. Mk 4

Queen's Royal Flight helicopter.

Westland Wessex HC. Mk 5

SAR helicopter of the Royal Air Force based in Cyprus.

Westland Wessex HU. Mk 5

Similar to Mk 2, for Commando assault duties from carriers of the Royal Navy. Design work began in April 1962 and construction of the prototype was started in May 1962. In service with A&EE (1) and 84 Squadron Akrotiri Cyprus (5).

Westland Wessex HAS. Mk 31

Generally similar to Mk 1, but with a 1,540shp Gazelle Mk 162 engine. Ordered for the Royal Australian Navy for anti-submarine duties from HMAS Melbourne.

Westland Wessex Mk 52

Similar to Mk 2, for Iraqi Air Force.

Westland Wessex Mk 53

Similar to Mk 2, for Ghana Air Force.

Westland Wessex Mk 60

Civil version in service with Uruguayan Navy.

Specifications:

Sikorsky S-58 / H-34 Choctaw

Engine: 1 x Wright R-1820, 1137kW / 1504 hp

Main rotor diameter: 56 ft / 17.1m

Length: 17.3m

Height: 4.9m

Max take-off weight: 6350kg

Empty weight: 3754kg

Max speed: 178 km/h / 150 kt

Cruising speed: 158km/h

Rate of climb: 5.6m/s

Service ceiling: 2900m

Range: 450km

Crew: 2

Passengers: 12-18

CH-34A/H-34A Choctaw

Transport and general purpose helicopter for US Army.

Engine: 1,525 hp Wright R 1820 84B/D piston.

Rotors: 4-blade main; 4-blade tail.

Operating speed: 40 - 128 knots

Mainwheel tyres 11.00 x 12

Tailwheel tyre 6.00 x 6

Wheel track 3.66m

Wheelbase 8.75m

Cabin length: 13 ft

Seats: 20

CH-34C / H-34C Choctaw

Similar to CH-34A

Operating speed: 40 - 128 knots

Mainwheel tyres 11.00 x 12

Tailwheel tyre 6.00 x 6

Wheel track 3.66m

Wheelbase 8.75m

Cabin length: 13 ft

LH-34D / HSS-1L
Winterised version of Navy Seabat.
Mainwheel tyres 11.00 x 12
Tailwheel tyre 6.00 x 6
Wheel track 3.66m
Wheelbase 8.75m
Cabin length: 13 ft

SH-34G / HSS-1 Seabat

Anti-submarine version ordered by US Navy 30 June 1952; accepted for service in February 1954.

Engine: 1,425 hp Wright R-1820

Mainwheel tyres 11.00 x 12

Tailwheel tyre 6.00 x 6

Wheel track 3.66m

Wheelbase 8.75m

Cabin length: 13 ft

SH-34J / HSS-1N Seabat
Improved version of SH-34G.
Mainwheel tyres 11.00 x 12
Tailwheel tyre 6.00 x 6
Wheel track 3.66m
Wheelbase 8.75m
Cabin length: 13 ft

UH-34D / HUS-1 Seahorse
Utility version for Marines; ordered 15 October 1954 and accepted for service January 1957.
Mainwheel tyres 11.00 x 12
Tailwheel tyre 6.00 x 6
Wheel track 3.66m
Wheelbase 8.75m
Cabin length: 13 ft

UH-34E / HUS-1A Seahorse
Version with pontoons for emergency operation from water.
Cabin length: 13 ft

VH-34D / HUS-1Z
VIP transport version of Seahorse.
Mainwheel tyres 11.00 x 12
Tailwheel tyre 6.00 x 6
Wheel track 3.66m
Wheelbase 8.75m
Cabin length: 13 ft

S-58B
Commercial passenger/freighter version.

S-58C
Commercial passenger-carrying version with two doors on starboard side of cabin.
Engine: 1 x Wright R-1820-84, 1137kW
Main rotor diameter: 17.1m
Length: 17.3m
Height: 4.9m
Max take-off weight: 6350kg
Empty weight: 3754kg
Max speed: 198km/h
Cruising speed: 158km/h
Rate of climb: 5.6m/s
Service ceiling: 2900m
Range: 450km
Crew: 2
Passengers: 12-18

S-58D
Commercial passenger/freighter version.

S-58T
Turbine conversion with Pratt & Whitney PT6 Twin-Pac.
Engine: P&W PT6T-3 coupled turboshaft, 1525 shp
Length: 50 ft 11 in
Width: 5 ft 8 in
Height: 15 ft 11 in
Rotor dia: 56 ft
MTOW: 13,000 lb
Useful load: 5600 lb
Slung cap: 5000 lb
Fuel cap (useable): 286 USG
Endurance: 2 hr 40 min
Max cruise: 110 kt
Max speed: 124 kt
Fuel consp (cruise): 106 USG/hr
Range (cruise speed, 20 min res): 260 nm
HIGE: 8950 ft
SE ceiling; 2100 ft
Crew: 2
Pax cap: 17

S-58T Mark II
Engine: UACL PT6T-6, 1,875 shp
Main rotor dia: 56 ft
Length: 50 ft. 11 in
Height: 15 ft. 11 in
Disc loading: 5.28 lb/sq.ft
Seats: 10-16
Empty weight: 8,354 lb
Useful load: 4,446 lb
Payload with full fuel: 1,924 lb
MTOW: 13,000 lb
Power loading: 8.54 lb/hp
Fuel capacity (standard): 283 USG/1,910 lb
Fuel capacity (optional): 433 USG/2,923 lb
ROC: 1,275 fpm
Service ceiling: 12,000 ft
Single-engine service ceiling: 4,200 ft
Vne @ 2,000 ft: 124 kt
Normal cruise @ 2,000 ft: 110 kt
Range @ normal cruise (45-min res. std tanks): 200 nm
Endurance @ max cruise (no res, std tanks): 2.6 hr
Range max fuel/ cruise: 401 nm/ 3.2 hr
Range max fuel / range: 346 nm/ 3.2 hr
ROC: 1260 fpm
Max sling load: 5000 lb
Hovering ceiling in ground effect: 10,400 ft
Hovering ceiling out of ground effect: 6,500 ft

Westland Wessex
Licence-produced UK version.

Westland Wessex HAS.3
Engine: RR Gazelle 165 turbine.
MAUW: 13,500 lbs
Operating weight: 11,000 lb
Fuel capacity: 1,710 lbs (approx 240 gals)
Fuel consumption (average): 700-800 lbs/hr
Max speed: 120 kts
Normal cruise: 90 kts

Westland WessexHC Mk.2

Engine: 2 x Bristol Siddeley Gnome Mk.110 or Mk.111 turboshaft, 1007kW / 1350 shp total

Type 10 coupling gearbox

Rotor head rating: 1,550shp

Main rotor diameter: 17.07m

Length rotors turning: 20.04m

Height: 4.93m

Max take-off weight: 6123kg

Empty weight: 3767kg

Max speed: 212km/h

Range with max fuel: 769km

Crew: 1 -3

Capacity: 16 seats

Westland Wessex HC Mk.5

Engines: One Bristol Siddeley Gnome Mk 112 and one Gnome Mk 113

Type 11 coupling gearbox

Main rotor diameter: 17.07m

Length rotors turning: 20.04m

Height: 4.93m

Crew: 1 -3

Capacity: 16 seats / 1814 kg

Westland Wessex HU.Mk 6
Engine: one Rolls-Royce Coupled Gnome twin-turboshaft with two pow-er sections each rated at 1,350 shp (1007 kW), combined output limit 1,550 shp (1156 kW).
Main rotor diameter 17.07 m (56 ft 0 in)
Length overall 20.03 m (65 ft 9 in)
Height 4.93 m (16 ft 2 in)
Main rotor disc area 228.81 sq.m (2,463.0 sq ft).
Empty weight 3927kg (8,6571b)
Maximum take-off weight 6120 kg (13,500 lb)
Maximum speed 214km/h (133mph)
Cruising speed 195 km/h (121 mph)
Range 769 km (478 miles)
Armament: role kit can include two 7.62-mm (0.3-in) GPMGs firing ahead, one or two 20-mm cannon, two or four AS. 11 wire-guided missiles, or rocket pods.

Westland Wessex Mk.31B
Engine: 1 x 1,575 shp Napier Gazelle 161 free turbine
Rotor diameter: 56 ft
Length 65 ft 10.5 in
Folded length: 38 ft 6 in
Height: 14 ft 10 in
Empty weight: 8,000 lb
Loaded weight: 13,500
Initial Rate of Climb: 1,540 ft/min
Ceiling: 14,100 ft
Speed: 108 knots
Range: 262 nautical miles
Bomb load: 2 x torpedoes (external)
Crew: 4

Westland Wessex Srs.60

Sik-S58-ld

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