[2.0] Sikorsky S-80

v1.1.5 / chapter 2 of 2 / 01 dec 17 / greg goebel

* The success of the twin-engine S-65 led to consideration of a derivative with three engines, which emerged as the "S-80". It was also very successful, and remains in production in the 21st century.

Sikorsky CH-53Es tanking up

[2.2] S-80 UPGRADES / CH-53K


* Although the S-65 proved a better solution to military needs than the S-64, the S-65 still lacked adequate lifting power for really satisfactory use as a flying crane. Lifting aircraft could be troublesome, and it didn't have as much power as desired for the minesweeping role. Towing a sled could be troublesome, particularly through rough seas.

In October 1967, the Marines issued a Specific Operational Requirement (SOR-14-20) for a helicopter with a lifting capacity 1.8 times that of the S-65 that could still fit on amphibious assault vessels. The Navy was also interested in such a machine for the "vertical replenishment (vertrep)" role, to resupply ships at sea by air. At roughly the same time, the Army began looking for a "Heavy Lift Helicopter (HLH)" to replace the CH-54.

Sikorsky had been working on an enhancement to the S-65, which acquired the company designation of "S-80", even before issue of the requirement, with this configuration featuring a third turboshaft engine and a more powerful rotor system, and proposed this solution to the USMC in 1968. The Marines liked the idea, since it promised to deliver a good solution with a minimum of delay, and funded development of testbed machine for evaluating the more powerful rotor system.

The Army was working on their HLH in parallel, focusing on a Boeing Vertol proposal that was something like a scaled-up Chinook. There was political pressure for all three services to obtain a common solution. In September 1970, US Defense Secretary Melvin Laird dictated that the services would all acquire the Army HLH candidate -- but the Marines and Navy protested that the giant Army HLH was simply too big to operate off of landing ships. That was obviously true on the face of it, and so at the end of 1971, Congress gave the Marines and the Navy the approval to go their own way and acquire the Sikorsky proposal; a contract for two "YCH-53E" prototypes was quickly issued. The Army HLH would be axed in late 1974.

* The first of the two YCH-53Es performed its initial flight from the Sikorsky plant in Stratford on 1 March 1974. The airframe was basically that of the S-65, but with three T64-GE-415 turboshafts, the third engine being nested on the back of the machine behind the rotor shaft, the engine intake sitting to the left of the rotor shaft. The engines featured anti-icing systems, and a Solar gas-turbine auxiliary power unit (APU) was fitted between the forward engine inlets for engine starting and ground power. It is unclear if S-65s had an APU as well. The S-80 also featured:

The S-80 could carry up to 55 troops, though it was generally assigned the heavy cargolifting role. It had an internal cargo capacity of 13,610 kilograms (30,000 pounds), and a sling load capacity of 16,330 kilograms (36,000 pounds). Sling loads could be carried by either the traditional single center-mounted cargo hook, or by a new twin cargo hook arrangement, with a hook fore and aft.

Sikorsky CH-53E Sea Stallions

The first prototype was wrecked in a ground accident. Although the prototypes were built with a wide-span, low-mounted symmetrical tailfin, flight control problems led to refitting the second machine with of a distinctive new tail assembly, with the tailfin canted to the left by 20 degrees, and an inverted-gull asymmetric tailplane mounted on the right. This change was used in production S-80s.

The initial preproduction "CH-53E Super Stallion" flew on 8 December 1975. This was the first machine in the S-65 / S-80 series to feature a digital instead of analog flight control system; the digital system would be used in all following S-80s. The initial production contract was awarded in 1978, with service introduction following in February 1981. The USMC built up inventory of the machine and found it very useful for aircraft recovery, as well as transport of artillery, light armored vehicles, and the like.

Despite its size, thanks to its excess of power the CH-53E's speed and agility were regarded as outstanding. The digital flight control system prevented the pilot from overstressing the machine. The CH-53E provided excellent service during the Gulf War. The US Navy also liked the CH-53E and acquired it in small numbers for shipboard resupply. The Marines and Navy acquired 177 S-80s between them.

   _____________________   _________________   _______________________
   spec                    metric              english
   _____________________   _________________   _______________________

   main rotor diameter     24.08 meters        79 feet
   tail rotor diameter     6.10 meters         20 feet
   fuselage length         22.35 meters        73 feet 4 inches
   footprint length        30.19 meters        99 feet
   folded length           18.44 meters        60 feet 6 inches
   height (tail rotor)     8.66 meters         28 feet 5 inches
   height (rotor head)     5.32 meters         17 feet 6 inches

   empty weight            15,070 kilograms    33,225 pounds
   max loaded weight       31,640 kilograms    73,500 pounds

   maximum speed           315 KPH             195 MPH / 170 KT
   service ceiling         5,640 meters        18,500 feet
   ferry range             2,075 kilometers    1,290 MI / 1,120 NMI
   _____________________   _________________   _______________________

CH-53Es could carry twin-gun armament and were fitted with the AN/ALE-39 chaff-flare dispensers, just as with the RH-53D. Most or all CH-53Es were later refitted with cockpit lighting for NVG compatibility; a Hughes AN/AAQ-16 FLIR AKA "Helicopter Night Vision System (HNVS)", on a somewhat "tacked-on" mount on the left side of the nose; new radios and a GPS receiver; and pilot seats with improved crash protection. Interestingly, apparently CH-53Es were evaluated with air-to-air missiles (AAMs) for self-defense, with one Sidewinder or two Stinger AAMs carried at the end of each sponson. Details of the evaluation are unclear, and this fit has apparently never been used operationally.

The CH-53E has been heavily tasked in recent years, with helicopters in the fleet starting to time out on airframe life from 2011. Machines retired by the Navy have been refurbished for Marine use, with an overhaul program for the fleet begun in 2016; but the type is in need of replacement, a matter discussed later.

* The Navy was very interested in the S-80 for the AMCM role, and acquired a variant optimized for that task, designated the "S-80M" or "MH-53E Sea Dragon". It differed from the CH-53E most visibly in having absurdly enlarged sponsons to provide substantially greater fuel storage and endurance. It also retained the inflight refueling probe of the CH-53E, and could be fitted with up to seven 1,136-liter (300 US gallon) ferry tanks internally, though it couldn't carry external tanks.

The MH-53E digital flight-control system included features specifically designed to help tow minesweeping gear. The Sea Dragon was equipped with mine countermeasures systems like those of the RH-53D, including the twin machine guns, with modern additions such as the AN/ALQ-160 acoustic countermeasures system; an AN/ALQ-166 magnetic mine hydrofoil sled; and a Northrop Airborne Laser Radar Mine Sensor (ALARMS).

The initial "YMH-53E" prototype was a conversion of a pre-production CH-53E, without the oversized sponsons, and performed its first flight on 23 December 1981. The first pre-production machine performed its initial flight on 1 September 1983, with service deliveries beginning in June 1986 and service introduction in April 1988. The Navy obtained a total of 46 Sea Dragons, with these machines operating almost exclusively in the AMCM role, since the Navy had acquired CH-53Es for the transport role. Most or all of the surviving RH-53Ds were also converted back to the transport role.

Sikorsky MH-53E towing minesweeper sled

There was a plan at one time to acquire six S-80s as VIP transports for the Presidential flight, with these machines to be designated "VH-53F". However, the contract was canceled, and no VH-53Fs were ever built.

* Although Sikorsky promoted an "S-80E" export variant of the CH-53E, the "S-80M-1" export variant of the MH-53E was the only variant of the S-80 series that found a foreign buyer, with 11 obtained by the Japanese Maritime Self-Defense Force (JMSDF). The initial buy was ordered in 1983, but due to political problems the first one was not delivered until 1989. The Japanese Sea Dragons were very similar to their US Navy equivalents, but lacked the inflight refueling probe. The Japanese Sea Dragons had a secondary transport capability and could be assigned to disaster-relief missions, a high priority for the Self-Defense Forces.


[2.2] S-80 UPGRADES / CH-53K

* The US Marines have obtained improved armament for their CH-53Es, purchasing a quantity of M3M GAU-21 12.7-millimeter machine guns from FN Herstal of Belgium. The GAU-21 can fire all available 12.7-millimeter ammunition, while offering a higher rate of fire and greater reliability than the venerable Browning M2. The Marines have plans to use the M3M GAU-21 on their other helicopters. In another upgrade program, Marine CH-53Es are being fitted with an AN/AAQ-29A FLIR imager with three levels of zoom magnification, for use in piloting at night or in bad weather.

The Marines had been planning to upgrade most of the their CH-53Es to keep them in service, but this plan stalled. Sikorsky then proposed a new version, originally the "CH-53X", and in early 2006, the USMC signed a contract for 156 machines as the "CH-53K", with the order later expanded to 200 helicopters. Five CH-53K prototypes, including a ground-test machine, were built, with initial flight of the first prototype on 27 October 2015, followed by the second on 14 March 2016. Low-rate production was initiated in 2017, with two pre-production machines being built. Introduction to service and full production is scheduled for 2021.

The CH-53K, named the "King Stallion", is a "clean-sheet" redesign of the S80. The main improvements are new engines, cockpit layout, and an airframe made mostly of composites. The engines are GE38-1B / T408-GE-400 turboshafts providing 5,595 kW (7,500 SHP); they dictated design modifications of the helicopter's intakes and exhaust, and are complemented by a new elastomeric hub system and composite rotor blades with swept tips. The end result is much-improved "hot and high" performance.

The new cockpit is based on the "Joint Interoperable Cockpit", which defines a digital "glass" cockpit scheme like that of the Bell UH-1Y Huey, now going into USMC service. The digital cockpit is complemented by a triple-redundant fly-by-wire flight control system. Other changes for the CH-53K include an improved external cargo handling system, and improvements to extend service life. The CH-53K is more economical to operate than the CH-53E, as well easier to maintain and service; it has over twice the radius of action and lift capacity -- 12.25 tonnes (13.5 tons).

   _____________________   _________________   _______________________
   spec                    metric              english
   _____________________   _________________   _______________________

   main rotor diameter     24.08 meters        79 feet
   tail rotor diameter     6.10 meters         20 feet
   fuselage length         22.29 meters        73 feet 1 inch
   footprint length        30.19 meters        99 feet
   height (tail rotor)     8.66 meters         28 feet 5 inches

   max loaded weight       31,640 kilograms    88,000 pounds
   maximum cruise speed    315 KPH             195 MPH / 170 KT
   service ceiling         4,385 meters        18,500 feet
   hover ceiling           970 meters          3,180 feet
   loaded mission radius   370 kilometers      230 MI / 200 NMI
   _____________________   _________________   _______________________

   Max loaded weight is with sling load, reduced to 33,565 kilograms 
   with internal load.  Hover ceiling is out of ground effect.

The CH-53K can carry two Humvee or similar tactical vehicles, or a single light armored vehicle, as sling loads. It has cargo hold 30 centimeters (a foot) wider than the CH-53E's to allow it to carry a Humvee internally, or standard-sized USAF 463L pallets as used on the C-17 transport; neither will fit inside a CH-53E. However, the CH-53K features new composite sponsons -- taller and longer than those of the MH-53E, but shorter in span -- to cut overall width by 1.83 meters (6 feet), giving the machine a narrower footprint for shipboard operations.


The CH-53K is fitted with defensive countermeasures and armor; it can mount a GAU-21 machine gun, or the like, on each side and in the rear. Standard personnel load is 33 troops, or 55 if center seating is installed, the seats being crashworthy. The Germans and the Israelis are very interested in acquiring the CH-53K to replace their S-65s.



* The following table gives the types and numbers of Sikorsky giant helicopter variants:

   variant built converted  notes 


   S-60        1            Sikorsky piston-powered demonstrator.
   S-64        3            Three protos, one for West Germany.
   S-64E     ~10            Commercial variant. 
   YCH-54A     1            US Army evaluation machine.
   CH-54A     54            US Army production machines.
   CH-54B     37            More powerful US Army variant.

   subtotal  106            Including S-60 demonstrator.


   YCH-53A     2            S-65 prototypes.
   CH-53A    141            USMC transport.
   RH-53A      -        15  CH-53As loaned to US Navy for AMCM.
   TH-53A      -         6  CH-53As passed on to USAF as trainers.

   HH-53B      8            USAF Super Jolly CSAR machines.
   HH-53C     44            Improved USAF Super Jolly CSAR machines.
   CH-53C     10            USAF transports, similar to HH-53C.

   CH-53D    124            More powerful USMC transport.
   VH-53D      2            CH-53D VIP transports.
   RH-53D     36            AMCM variant, 30 for USN, 6 for Iran.

   YHH-53H     -         1  HH-53B modified with all-weather avionics.
   HH-53H      -        10  All-weather Super Jolly upgrades.
   MH-53H      -         8  Upgraded HH-53H.
   MH-53J      -        41  Improved MH-53H configuration machines.
   MH-53M      -        25  MH-53Js with further improvements.

   CH-53G    112            CH-53D for German service.
   S-65C-2     2            CH-53Oe for Austrian service.
   S-65C-3    33            HH-53C for Israeli service.

   subtotal  514            


   YCH-53E     2         -  S-80 prototypes.
   CH-53E    177         -  Transports for USMC & US Navy. 
   CH-53K      -         -  Future S-80 for USMC.
   MH-53E     46         -  Sea Dragon AMCM machines for US Navy.
   VH-53F      -         -  VIP transport, not built.
   S-80M-1:   11         -  Sea Dragons for Japanese JMSDF.

   subtotal  236            

   TOTAL     856



* As is so often the case, I thought this would be a fairly straightforward writeup, and it turned out to be about twice as long as I expected it to be.

I can only recall seeing an S-65 once, or at least I think it was an S-65. I was down at Fort Hood, Texas, in 1973 and 1974, and was wandering around on the post when I got to witness a huge helicopter taking off. I wasn't that familiar with the Sikorsky family at the time and all I knew was that it was a Sikorsky Green Giant of some sort, but though the memory is vague I don't think it was an S-61R. I do remember the awesome threshing of its big main rotors.

I've much more recently seen an Ericson S-64F being prepped for fire fighting operations in Montana. Incidentally, those readers who took notice of the term "gremlin nest" in the text should be aware that this is not military slang -- it's my own little phrase.

* As concerns copyrights and permissions for this document, all illustrations and images credited to me are public domain. I reserve all rights to my writings. However, if anyone does want to make use of my writings, just contact me, and we can chat about it. I'm lenient in giving permissions, usually on the basis of being properly credited.

* Sources include:

* Revision history:

   v1.0.0 / 01 jun 04 
   v1.0.1 / 01 may 06 / CH-53K.
   v1.0.2 / 01 mar 08 / Review & polish.
   v1.0.3 / 01 apr 09 / Review & polish.
   v1.1.0 / 01 dec 09 / Went to two chapters, added corrections.
   v1.1.1 / 01 may 10 / Review & polish.
   v1.1.2 / 01 mar 12 / Review & polish.
   v1.1.3 / 01 feb 14 / CH-53K status updates, CH-53D retirement.
   v1.1.4 / 01 jan 16 / Review & polish.
   v1.1.5 / 01 dec 17 / Review & polish.