S-65/H-53A/D Sea Stallion/ H-53E Super Stallion
In January 1961, The Department of Defense issued a Request for Proposals for the Tri-Service Assault Transport Program, a medium sized Vertical Take Off and Landing (VTOL) aircraft. This project was initiated to provide a replacement forSikorsky S-56 (HR2S-1) helicopter and the competition was won by the Ling Tempco Vought (LTV) XC-142A VTOL Transport. The Marine Corps was concerned with the XC-142A prop-rotor downwash which was considerably higher than the HR2S-1 (S-56), decided it was unsuitable for shipboard operations, and decided to make their own request for a new heavy lift helicopter.
On March 7, 1962, the Bureau of Naval Weapons (BuWeps) issued a Request for Proposals for a ship based helicopter able to lift an 8,000 pounds (3630 kg) payload over a radius of 100 nm (115 miles, 185 km) at a speed of 150 knots (172 mph, 278 km/h). Its mission was ship-to-shore transport, downed aircraft recovery, personnel transport, and Medical Evacuation. Three proposals were submitted to BuWeps: Vertol proposed a version of the HC-1B (CH-47A Chinook), Kaman proposed a development of the British-designed Fairey Rotodyne, and Sikorsky proposed the S-65. In July 1962 Sikorsky was chosen as a result of technical, production capability, and cost considerations. However, insufficient funds prevented a contract award. Sikorsky negotiated to lower theResearch and Development (R&D) costs and reduce the number of prototype helicopters to two instead of the original four prototype helicopters. On September24, 1962Sikorsky was awarded a contract to design and develop a mock up, a static test airframe, and two YCH-53A prototype helicopters for $9,965,635. First flight of the YCH-53A occurred on October 14, 1964
The S-65 helicopters featured a 72 foot 6 bladed fully articulated main rotor and a 4 bladed tail rotor powered by two 2,850 shp General ElectricT-64-6 free turbine turboshaft engines. All fuel was carried in external sponsons. With a crew of 3,it was capable of carrying 38 fully-equipped troops or 24 litter patients and 4 medical attendants. Internally 8,000 pounds of cargo could be carried or 13,000 pounds externally.
The S-65 helicopter design was based on previous designs. The S-56 and S-64 models contributed the basis for dynamic components and the S-61R provided a basic shape for the S-65
In January 1965,a MarineCH-53A flew at speeds as high as 170 knots (196 mph) at gross weights of up to 35,000 lbs. making it the free world’s fastest production helicopter.
S-65 Model Designations
S-65 Development Timeline
S-65 Two Engine Models
U.S Marine Corps heavy lift helicopter featured a six blade 72 foot main rotor and a 4 bladed 16 foot anti torque tail rotor. The fuselage was watertight allowing water landings in an emergency.
Fifteen CH-53A helicopters modified for the U. S. Navy airborne minesweeping mission.
U.S. Air Force modelbased on the CH-53A helicopter modified for the Combat Search and Rescue (CSAR) mission. Air-to-Air Refueling capability and jettisonable external auxiliary fuel tanks, a rescue hoist above the crew door were added. The engines were upgraded to T64-GE-3 engines (3,080 shp).
U.S. Air Force follow-on to the HH-53B CSAR helicopters with increased engine power (T64-GE-7 engines 3,435 shp).and cantilevered external auxiliary fuel tank mounts.
CH-53D helicopters builtin a Co-Production Program for the German Army(Heersflieger) by VFW/Fokker in Speyer, Germany. The German Government has modernized the fleet of helicopters over the years and they remain in service 44 years, as of 2013, after the first delivery. The latest upgrade to the CH-53GA configuration equips the helicopters for an operational lifetime lasting beyond 2030. In January 2013, all CH-53 helicopters were transferred from the German Army (Heersflieger) to the German Air Force (Luftwaffe).
Two S-65C-2 (CH-53D) helicopters were delivered to Austria. Although they performed well in high altitude operations, high operating costs eventually lead to the sale of the 2 helicopters to Israel.
S-65C-3 CH-53 Yasur (Petrel)
Forty two CH-53D helicopters sold to the Government of Israel. Israel also acquired additional used H-53 helicopters from Austria and the U.S. Government. They have been upgraded several times and are projected to remain in service until at least 2025.
Six VH-53F helicopters were ordered for the Presidential support program. Trial landings at the White House revealed that the downwash from the H-53 rotor system was not compatible with the White House shrubbery. The plan was cancelled by the White House groundskeeper. Two CH-53D helicopters modified with Glossy “Marine Green” paint and more comfortable interiorswere assigned to VX-1 as VH-53D helicopters to carry the press corps and spare parts in support of the Executive Transport mission.
The CH-53A helicopters featured extensive use of Titanium which at the time was considered an exotic metal with limited applications.
The S-65 fuselage was constructed of an aluminum structure with aluminum skins and composite removable panels. The sharp break in the fuselage for the rear ramp caused significant drag. The engineering solution to this problem was to add strakes, known as “Elephant Ears”, to the fuselage at the ramp.
The fixed stabilizer was located on top of the tail rotor pylon on the right side. This 24.5 sq. ft. stabilizer had 10 degrees of dihedral and a zero degree angle of incidence.
Main Rotor Assembly
A 6 bladed fully articulated oil lubricated main rotor head was installed on the S-65 helicopter. The 72 foot 2.7 inch diameter main rotor was controlled by a 2 stage hydraulicirreversible servo control system.
A Government funded design program was initiated to greatly reduce maintenance of the main rotor head while increasing reliability. All lubrication requirements were eliminated to solve a persistent oil leakage problem The elastomeric head went through extensive bench and whirl stand testing and achieved first flight in early 1972. A retrofit program for the CH-53D fleet replaced the oil lubricated main rotor with a lower maintenance elastomeric rotor head. It featured a cone-shaped spherical bearing for pitch, flap, lead and lag changes. The elastomeric bearing was constructed of a sandwich of rubber and metal laminates with no lubrication required.
Main Rotor Blades (Aluminum Spar)
The all metal main rotor blades were constructed of aluminum alloy except for titanium cuffs. The main rotor blade was constructed of a hollow extruded aluminum spar pressurized with nitrogen (Blade Inspection System(BIM)) to detect cracks withhoneycomb filled, aluminum skinned pockets bonded to the spar. A cockpit warning system advised the flight crew if spar pressure was depleted.The H-53 fleet was retrofitted by the U.S. Government with the IBIS (Inflight Blade Inspection System) which used radioactive Strontium 90 to detect a loss of pressure in the blade spar. A detector assembly picked up the radiation signal which sent a signal to a signal processor. The signal processor picked up the message which illuminated the caution lights in the cockpit.
Improved Main Rotor Blades (Titanium Spar)
In May ,1970 Sikorsky initiated a company funded Research and Development (R&D) project prior to receiving Government funding to increase the CH-53D helicopter lift and performance with a titanium spar main rotor blade identified as the Improved Rotor Blade (IRB). Titanium was the metal of choice due to its strength and light weight. In order to economically produce the 33 foot titanium spars new manufacturing techniques were developed. The spars were constructed of a long and narrow sheet of titanium. The sheets were cold formed in a four step process using a 40 foot long 2,000 ton hydraulic press into a round shape with the gap closed by plasma arc welding. The titanium root attachment was inertially bonded to the end of the spar. The assembly was then placed in heated dies and creep formed into the final oval shape. The Nomex honeycomb pockets were bonded to the spar and the entire assembly wrapped in fiberglass epoxy to produce the complete blade. . The IRB, with a larger chord, improved SC1095 airfoils and a higher 16 degree twist, allowed a gross weight increase from 36,693 to 42,000 pounds. The first flight of a CH-53D with the IRB installed was September 29, 1971. The same blades were used on the CH/MH-53E helicopter with 3 foot extenders to increase the main rotor diameter. Blades of similar construction were used for both the S-70 and S-76 model helicopters.
Cruise Guide Indicators
The cruise guide indicators, one for the pilot and one for the copilot were mounted on the instrument panel to assist the pilot in obtaining optimum performance from the helicopter by providing a direct indication of the degree of main rotor blade stall.. This was accomplished by a transducer mounted within the piston of the aft lateral main rotor servo which measured the vibratory loads imposed on the stationary swashplate. Thevibratory loads on the stationary swashplate were influenced by varying conditions of main rotor speed, gross weight, altitude, temperature, load factor, airspeed, andcenter-of-gravity position. These loads were a direct indication of the onset of blade stall or the degree of blade stall encountered during a flight.The indicators were graduated in percent, from 0 to 100 percent. Normal operation was between 0 and 30 percent with a maximum of 70 percent. Transient operations between 30 and 70 percent were permitted. If one indicator failed, the other indicator would read double.
The transmission system consists of two nose gearboxes, a main gearbox, accessory gearbox, intermediate gearbox and the tail rotor gearbox.
The nose gearbox rotates the output of the engine 135 degrees to align with the main gearbox inputs and reduces engine rpm from 13,600 rpm to 6,023 rpm through high speed bevel gears
The main gearbox couples the two nose gearboxes and provides output power for the main rotor, tail rotor, and accessory gearboxes. The main gearbox bevel gears and a two stage planetary reduction to reduce main rotor speed to 185 rpm and the tail drive shaft speed to 3,011 rpm. The main gearbox also drives the main gearbox oil cooler (7,070 rpm), the main gearbox oil pump, freewheeling units, No. 1 generator, main rotor tachometer-generator, first-stage hydraulic pump, and the accessory gearbox (6,144 rpm) when it is not being driven by the Auxiliary Power Plant (APP).
The accessory gearbox drives the No. 2 generator, second-stage servo hydraulic pump, winch hydraulic pump, and the accessory gearbox oil pump. The accessory gearbox is driven by the main gearbox when the main rotor is turning and the APP when the main rotor is stopped.
Tail Rotor Assembly
A 4 bladed 16foot diameter all metal semi-articulated tail rotor was installed. The tail rotor pitch change was accomplished by a 2 stage hydraulic servo.
Engine Air Particle Separators (EAPS)
To extend engine life in hostile environments based on experience in Vietnam, EAPS was installed on most H-53 model helicopters. The engine air particle separators were designed to remove visible moisture, sand, dust, and other foreign particles from the engine inlet air.Each EAPS unit contained 759 STRATA tubes. As the inlet air traveled through the STRATA tube it traveled in a cyclonic motion which caused foreign particles to migrate towards the walls of the tube and pass into the scavenge ducting. The clean air continued into the engine and the scavenge blowers exhausted the particle laden air overboard. The EAPS units were hinged to swing away to allow normal access to the engine inlet and servicing of the nose gearbox. Bypass doors opened in the event of EAPS clogging and at airspeeds above 60 knots. The electric power for the EAPS was provided by the power normally used for the nose gearbox fairing anti-ice controllers.
Auxiliary Power Plant (APP)
Main Fuel Tanks S-65 helicopters were equipped two 319 gallon main fuel tanks in sponsons attached to the cabin. Each tank consisted of a single bladder type fuel cell with the bottom third of each cell being self-sealing. No boost pumps were installed in the tanks. Fuel was sucked from tanks using a “Soda Straw” technique by boost pumps above the cabin. A crashworthy fuel system could be installed by a modification kit which included self-sealing breakaway valves where fuel lines passed through the fuel cell wall. Contamination traps were installed in the vent lines to remove sand and other contaminates.
Internal Range Extension Tanks S-65 helicopters modified with a retrofit kit could install up to seven 285 gallon tanks in the cabin. For safety, these tanks were filled with reticulated foam to prevent an explosive fuel/air mixture from forming in an empty or partially filled tank. Internal tanks contained fuel transfer pumps to transfer fuel to the main tanks. Each empty tank including tiedown chains, electrical harness, and hoses weighed 340 pounds.
External Auxiliary Fuel Tanks Jettisonable 650 gallon external tanks were installed on a pylon attached to the sponsons on CH-53D and HH-53C helicopters. Theses tanks were fabricated by winding a fiberglass-composite filament over a thin aluminum shell. For cg (center of gravity) control the tanks contained two compartments. During fueling the forward compartment filled first and then the aft compartment. Engine compressor bleed air was used to force fuel from the auxiliary fuel tanks to the main tanks.
General Arrangement Drawing
General Characteristics and Performance S-65(CH-53D)
S-65 Three Engine Models
CH-53E Super Stallion
The CH-53E design was a combination of a company funded S-64B three engine Super Skycrane and the RH-53D helicopter. The S-64B was envisioned as an 18 ton heavy lifter. To reduce development costs, it was based on CH-53D components. Three T-64 engines were used and extenders were used to increase main rotor diameter without designing new blades. Significant development was done on the S-64B including wind tunnel testing and a Power System Test Bed (PSTB) which was used for endurance testing of the CH-53E powertrain.
In order to avoid a full scale competition for a heavy lift helicopter, the CH-53E was procured as an Engineering Change Proposal (ECP) to the RH-53D helicopter to add a third engine and a seventh main rotor blade to double the external lift capability (CH-53A, 16,000 lbs. vs. 32,000 lbs.). During the design phase one system after another required major modification with the final result being essentially a new helicopter. Six feet were added to the main rotor diameter by adding 3 foot extensions to the main rotor spindles. This created a 79 foot main rotor diameter while allowing use of the CH-53D Improved Rotor Blades (IRB) already in the inventory.
The tail rotor was increased to 20 foot diameter canted 20 degrees to the left to provide lift as well as anti-torque functions. The fuselage was extended 6 feet 2 inches to accommodate the third engine.
The CH-53E prototype helicopter, the western world’s most powerful helicopter, during testing at the Naval Air Test Center Patuxent River, Maryland
The design goal of doubling the lift capability of the helicopter was accomplished with only a 10% increase in size of the helicopter.
CH/MH-53E Transmission System
Tail Rotor Gearbox
Tail Rotor Pylon
CH-53E Fuel System
External Cargo Hooks
General Arrangement Drawing
MH-53E Sea Dragon
As the number of H-53E airframes available has diminished due to attrition and requirements have increased, a number of MH-53E helicopters have been modified to a utility configuration and attached to Marine squadrons for combat assault duties.
General Characteristics and Performance S-65 (CH-53E)
Sikorsky Aircraft S-65 production consisted of 737 helicopters.
The replacement for the CH-53E is presently (2013) in development. In April, 2006 a $3.6 billion contract was awarded by the Naval Air Systems Command to design and develop the CH-53K Heavy Lift helicopter for the USMC. The contract provided for one Ground Test Vehicle (GTV) and four flight articles designated as Engineering Development Models (EDM). In addition, 2 additional GTV helicopters were built for laboratory structural testing, one static test article and one fatigue test article. The design goals for the CH-53K were to increase the lifting ability to three times the CH-53E (27,000 pounds) with a 110 mile radius under USMC hot and high conditions while maintaining the same “footprint” as the CH-53E for shipboard operations. Other design parameters are a 23% reduction in maintenance man-hours, increased survivability, and a 20% reduction in fuel consumption.
The Rockwell Collins Avionics Management System (AMS) advanced cockpit incorporates fully integrated flight and navigational displays.
On December 4, 2012 the CH-53K GTV was rolled out at the Sikorsky Florida Assembly and Flight Operations (FAFO) facility in West Palm Beach Florida and delivered to the Sikorsky flight test team.
On June 6, 2013 Sikorsky Aircraft Corp. received a $435 million U.S. Navy contract amendment to build four production-representative CH-53K heavy lift helicopters for the U.S. Marine Corps. Designated as System Demonstration Test Articles (SDTA), the four aircraft will enable the Marines to conduct operational evaluation of the new helicopter system in support of Initial Operational Capability scheduled for 2019.
Sikorsky Archives News October 2007 “S-65”
Prepared by Vinny Devine
LAST UPDATE SEPTEMBER 4, 2013
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