Sikorsky H-34 Choctaw/Seabat
/Seahorse
With its distinctive hump, the Sikorsky H-34 is one of the most recognizable helicopters in history. Historically, it was a transition helicopter.
Bullet Points
- Last of the large piston-engine military helicopters (along with the Piasecki H-21 Flying Banana).
- Used by the U.S. Navy, Army, Marines, Coast Guard, and Air Force Reserves.
- First flight March 8, 1954. Entered Navy and Army service in 1955. Entered Marines service in 1957.
- Used by the French in the Algerian War, where combat assault evolved
- CH-34D (The “Dog”) used heavily by the Marines in Vietnam for combat assault
- Big and vulnerable, especially for pilots in their high cockpit
- Comparable in performance to the UH-1 Huey but with greater capacity
- Approximately 1,800 built by Sikorsky. Another 600 manufactured in England, France, and Italy. Production ended in 1970.
- Our HH-34J (58-1366) began life as a Navy HSS-1 antisubmarine warfare (ASW) helicopter. After it was retired, the USAF refurbished it for search and rescue (SAR) activities. In 1971, the Air Force gave it and some other converted HSS-1s to Air Force reserve squadrons. They remained in service only three years. The Air Force redesignated these helicopters as H-34Js and renamed them Choctaws.
Perspective
With its distinctive hump, the Sikorsky H-34 is one of the most recognizable helicopters in history. Historically, it was a transition helicopter. The H-34 and the Piasecki H-21 were the last major piston-engine military helicopters before turbine engines dominated helicopter design. These two might have passed into history with little notice, but wars in Algeria and Southeast Asia brought them to prominence. Both pioneered troop assault, gunship roles, cargo hauling, and other operations that have defined the war roles of helicopters ever since. In Algeria, the French used both helicopters heavily. In Southeast Asia, the H-21 Shawnee was the Army’s initial big bird, while the Marines used the UH-34D, which they called the Seahorse. The Army replaced its H-21s in Vietnam quickly, using UH-1 Hueys for most of the Shawnee’s tasks. Marine Seahorses, in contrast, served until fairly late in the war, when the bigger and faster H-46 Sea Knight gradually replaced them.
The museum’s HH-34J Choctaw had an unusual history. The Navy originally purchased it as an anti-submarine warfare (ASW) helicopter. The Navy retired our bird and sent it to the boneyard at Davis-Monthan. However, when some Air Force Reserve units needed some search and rescue helicopters in 1972, the Air Force refurbished several of them, removing their ASW equipment. As anti-sub helicopters, these helicopters had auto-hover capability, making them ideal for rescue work. The Air Force designated its small fleet HH-34Js and named them Choctaws. Although these birds served the Air Force Reserves well, they were only interim aircraft. In 1974, the Air Force Reserves retired them again and sent them back to the boneyard or gave them to museums. They were the last H-34s to fly. Our HH-34J was displayed at the Museum of Aviation at Robins AFB before coming to Pearl Harbor Aviation Museum in 2013.
How To Build A Bigger Helicopter
The first helicopters were tiny. They resembled the Bell H-13s seen on M*A*S*H. The engine sat behind the cockpit. Figure 2 shows an H-13 with its flat six “boxer” internal combustion engine. There are three pistons on each side. The engine sits vertically, and the driveshaft leads directly to the rotor hub. This arrangement makes the driveshaft unit simple to build. Unfortunately, if the manufacturer wanted a larger cabin in front of the engine, it would have to add balancing weight to the back. For large cabins, this would not make engineering or economic sense.
Unfortunately, if the manufacturer wanted a larger cabin in front of the engine, it would have to add balancing weight to the back. For large cabins, this would not make engineering or economic sense.
Seeking ways to build helicopters with larger helicopters, manufacturers took two different design approaches. One was to have twin rotors placed at the front and back of the helicopter. Typically, a single engine in the tail turned both rotors. One advantage of this approach was that there was no need for a tail rotor to deal with the torque of the overhead rotor. With a strong enough engine, manufacturers could create helicopters with substantially larger cabin. Piasecki (later Vertol, Boeing Vertol, the Boeing Helicopter Division) pioneered this approach with its series of “flying banana” helicopters. Figure 3 shows a Piasecki H-21, which the U.S. Army called the Shawnee and which the USAF called the Workhorse.
Sikorsky took a different approach to building larger helicopters. It kept the rotor head and blades in the middle of the aircraft, at its center of gravity. However, it placed the engine in the front of the helicopter. The engine connected to the rotor hub through an angled transmission line. Figure 4 shows the radial piston engine in the nose of a Sikorsky H-34.
A U.S. Marine Corps Sikorsky UH-34D Seahorse of Marine Medium Helicopter Squadron HMM-362 in the Vietnam War in 1967. Due to the pre-1962 designation “HUS-1”, the UH-34 was often named “Huss”. Source: USMC. http://en.wikipedia.org/wiki/File:H-34_in_Vietnam.jpg.
For forward vision, Piasecki raised the cockpit 15 feet in the air. This gave a commanding view, but it made pilots prominent targets for ground fire while they sat on the ground loading or unloading. In addition, the only practical way to enter and exit the cockpit was through steps on the outside of the aircraft. Getting injured pilots down from the cockpit was very difficult.
Although these two design patterns for building large helicopters were conceived in the 1950s, Sikorsky and Piasecki/Boeing kept these approaches in subsequent helicopters. Sikorsky helicopters such as the H-34, SH-3, and the CH-53 retained the single-rotor design. Piasecki/Boeing’s later H-46 and H-47 had dual rotors.
H-19
Sikorsky’s first “big” helicopter with the engine in its nose was the H-19 Chickasaw, which saw service in Korea. When people think about Korean War helicopters, they typically envision the small H-13 helicopters used by MASH units. These were certainly important, but they their minimal carrying capacity severely limited their uses. Even in the medical evacuation rule that these helicopters were famous for, size and weight limitations meant that wounded evacuees had to lie outside the cabin. Sikorsky’s H-19 offered the first useful carrying load for a military helicopter. This allowed the Army and other services to explore the usefulness of cargo and troop carriage, especially in the combat assault role. With only 600 hp, however, the H-19 was still quite limited.
AMMO PICKUP–Marines of the Air Delivery Platoon, hook a cargo net loaded with boxes of ammunition under the helicopter to be airlifted to the front lines. The helicopters from HMR-161 airlifted all supplies to the front for 7 days during Operation Haylift.” Source: U.S. defenseimagery.mil photo no. HM-SN-98-06668.JPEG/127-GK-13-A170051. February, 1953. Photographer: Sgt. Robert E. Kiser, USMC.
| Category | H-19 Chickasaw | H-34 Choctaw / Seabat / Seahorse | H-21 Workhorse / Shawnee | CH-46 Sea Knight |
|---|---|---|---|---|
| Weight, empty (lb) | 4,795 | 8,230 | 8,950 | 11,585 |
| Weight, gross (lb) | 7,900 | 13,300 | 15,200 | 24,300 |
| Difference (lb) | 3,105 | 5,070 | 6,250 | 12,715 |
| Power (bhp or shp) | 600 | 1,525 | 1,425 | 3,740 |
| Maximum speed (mph) | 101 | 120 | 127 | 166 |
H-34
Almost as soon as Sikorsky designed the H-19, it began working on a similar but larger helicopter. Internally, Sikorsky had designated the H-19 the S-55. Internally, Sikorsky designated the new helicopter design the S-58. In military use, this bigger bird became the H-34 in 1962 under the United States Tri-Service aircraft designation system. Table 1 compares the H-19 and the H-34 (as well as the H-21, which was a contemporary of the H-34, and the Vietnam Era CH-46 Sea Knight that replaced the H-34 for the Marines).
The S-58 was powered by a World War II era Wright R-1820-84 radial piston engine. This engine powered early WW II aircraft such as the B-17 and the SBD Dauntless dive bomber. Unlike the gas turbine engines that began to power new helicopters that followed the H-34, piston engines were heavy for its weight. Consequently, the big H-34 cruised at only 97 mph. In addition, engine weight meant that the H-34 had limited cargo capacity. On the positive side, the engine’s 1,525 horsepower was higher than the early UH-1s Hueys that came to Vietnam after the H-34, so performance was actually comparable.
To lighten the aircraft, parts of the H-34’s skin were made of magnesium. Magnesium corrodes in salt air, so the Navy and Marines had to be very careful to wash it constantly. In addition, magnesium burns easily. This is undesirable in a war helicopter.
Adoption
The H-34 has one of the most familiar profiles of any helicopter, but the H-34 almost failed to find a buyer. It tended to place second in selection decisions. In the end, however, the U.S. Navy, Army, Marines, Coast Guard, and the Air Force Reserves adopted the Sikorsky S-58.
These adoptions took place before the United States Tri-Service aircraft designation system in 1962. Consequently, early versions of the H-34 were given different designations by the different services. Table 2 shows the designations that the services gave the H-34 before and after the Tri-Service system.
| Tri-Service | Original | Operator | Name | Description |
|---|---|---|---|---|
| CH-34A | CH-34A | Army | Choctaw | Cargo, combat assault, medevac |
| CH-34C | CH-34C | Army | Choctaw | Cargo, combat assault, medevac |
| UH-34D | HUS-1 | Marines | Seahorse | Cargo, combat assault, medevac |
| UH-34E | HUS-1A | Marines | Seahorse | Amphibious version of UH-34D |
| HH-34F | HUS-1G | Coast Guard | Seahorse | Search and Rescue |
| SH-34G | HSS-1 | Navy | Seabat | Antisubmarine warfare |
| UH-34G | NA | Navy | Seabat | Cargo |
| SH-34J | HUS-1N | Navy | Seabat | Night-capable version of SH-34G |
| UH-34J | NA | Navy | Seabat | Cargo |
| HH-34J | NA | Air Force | Choctaw | Restored SH-34J, used briefly for search and rescue in reserve units |
NAVY HSSS SEABATS
In World War II, dive bombers patrolled around the fleet to find threatening submarines. They carried bombs or depth charges to attack the submarines they found. The Navy saw the helicopter as a way to put an anti-submarine warfare (ASW) aircraft not only on carriers but also on cruisers. These helicopters received the Navy designation HS, for helicopter, anti-submarine. Anti-submarine warfare helicopters located submarines with dipping sonar listening systems. The helicopter would fly to an area, hover, lower its sonar, and listen for submarines. If the area was “clean,” the helicopter would fly to the next area in its patrol pattern and repeat the cycle. These versatile helicopters also handled cargo loading between ships, rescue, plane guard duty for carriers, and other Navy roles.
After trying several interesting but unsatisfactory helicopters, the Navy held a design competition in 1954. Bell offered its HSL-1 (Helicopter, Antisubmarine, Bell), while Sikorsky offered its S-58 as the HSS-1 (Helicopter, Antisubmarine, Sikorsky). To Sikorsky’s chagrin, Bell won the competition.
A U.S. Navy Bell XHSL-1 (Bell Model 61) prototype in flight. This was the first USN helicopter fitted with a dipping sonar, although mostly only the prototypes (BuNos 129133-129136) were used for flight test. Most production models were stored directly. Source: U.S. Government photograph.http://en.wikipedia.org/wiki/File:Bell_XHSL-1_prototype_in_flight_c1953.jpg.
Almost immediately, however, the Navy began to have second thoughts. It soon became apparent that the HSL-1 would be too large to fit comfortably on carriers, much less cruisers. Worse yet, the dual rotors were so loud that sonar operators could not hear their dipping sonar’s signals. The Navy began procuring HSS-1s, which they called the Seabat. The S-58 was no longer in danger of being a might-have-been aircraft.
The HSS-1 entered squadron service in 1955. In 1958, HSS-1Ns began to appear. These new Seabats were capable of operating at night, so they could provide 24-hour protection for the fleet. In the Tri-Service designation that came into place in August 1962, the HSS-1 became the SH-34G, and the HSS-1N became the SH-34J. The Navy also bought cargo versions of these helicopters, which became the UH-34G and the UH-34J.
Army CH-34 Choctaws
The Army needed a larger utility and combat assault helicopter, and the USAF needed a cargo helicopter to lift components to the Distant Early Warning line radar stations in the Arctic. This time, the Sikorsky S-58 squared off against the Piasecki H-21. Sikorsky lost again. The Army and Air Force began to procure large numbers of H-21s, which the Army called the Shawnee and the Air Force called the Workhorse. Later, under the Tri-Service Designation system, the H-21 became the CH-21.
Unfortunately for the Army but fortunately for Sikorsky, Piasecki could not produce H-21s quickly enough to meet the needs of the Army and the Air Force. Also unfortunately for the Army, the Air Force had higher priority for the aircraft that Piasecki was producing. The Army turned back to Sikorsky and purchased a large number of the S-58s, which the Army designated the H-34 Choctaw. In the Tri-Service Designation system, Army versions became the CH-34A and CH-34C.
To simplify logistics, the Army segregated its two large helicopters geographically. The CH-34s served the eastern United States and Europe. The CH-21s served the western United States and Asia. When the war in Southeast Asia began, the Army sent CH-21s to support operations because Southeast Asia was in the CH-21 region. This kept Army Choctaws out of the war. In any case, the Army moved quickly to replace its Choctaws and Shawnees with UH-1 Hueys.
Although the Army kept its CH-34s in Europe and the Eastern United States, it is useful to talk about the ArmyChoctaws because the Army mounted both defensive and offensive weapons on its birds. The Army’s weapons experience showed that the CH-34 was marginal as an offensive weapons platform because of its relatively weak structure. Later, UH-1 Hueys were did have the strength to be effective offensive gunships.
Marine HUS Seahorses
After atomic bomb tests in the Pacific, it became clear to the Marines that future beach landings against nuclear adversaries would be suicidal. Paratroop drops behind enemy lines were possible but difficult to achieve successfully. The Marines focused instead on helicopter assault. The Army liked the small UH-1 Huey for its ability to land in restricted spaces. The Marines wanted to move troops en masse, so they selected larger helicopters.
Seahorse helicopters of Marine medium helicopter transport squadron HMM-362 in flight over the Mekong Delta, Vietnam, 1962. Source: U.S. Navy National Museum of Naval Aviation photo No. 2000.243.021. U.S. Navy. http://en.wikipedia.org/wiki/File:HUS-1s_HMM-362_in_flight_Vietnam_1962.jpg.
The Marines’ first choice was the enormous Sikorsky HR2S-1, which would become the CH-37 under the Tri-Service aircraft designation system. It was nicknamed the Deuce because of its two big Pratt & Whitney R-2800 Double Wasp radial engines that drove a single rotor. The big CH-37C could seat 26 troops or a large amount of cargo internally or as a slung load. The Marines ordered 60 of the aircraft in 1953, but they did not begin receiving production aircraft until 1956. By then, the Marines realized that the Deuce was a disappointment. It was reasonably serviceable, but it was not the helicopter the Marines wanted. Although the Deuce saw service in Vietnam, its small numbers consigned it to the list of historical oddities among helicopters.
Unable to have the big helicopters they really wanted, the Marines decided to procure a medium-size helicopter. They settled upon a version of the Navy’s HSS-1 ASW helicopter. However, the Marine version, called the HUS-1 (Helicopter, Utility, Sikorsky) Seahorse, was not approved until 1955. Operational units began to receive them in 1957. In time, the Marines procured 462 CH-34Ds and 40 CH-34Es with pontoons. Given military parlance, the predominant CH-34D was called the Dog. This was not a term of derision. The Navy also bought HUS-1 Seahorsesfor cargo duty.
Operation “Jackstay”, Vietnam, 1966, Marine UH-34 Helicopters lift off from USS Princeton (LPH-5) to land “Leathernecks” in the Republic of Vietnam during Operation “Jackstay”, 26 March 1966. Source: Photographed by Journalist 1st Class E.J. Filtz, USN. http://www.history.navy.mil/photos/images/k30000/k31422.jpg
United States Coast Guard
The United States Coast Guard saw the potential of the H-34 as a search and rescue helicopter. It bought six HUS-1Gs, which were very similar to Marine versions of HUS-1. In 1962, they were designated HH-34Fs. The Coast Guard’s experience was not entirely a happy one. Three of the aircraft were lost in accidents. Buying no more, the Coast Guard transferred the three survivors to the CIA’s Air America. Air America lost one of them in Southeast Asia.
United States Air Force Reserves
The only service that did not adopt to H-34s when it first came out was the United States Air Force. In 1971, however some Air Force Reserve units needed an interim rescue aircraft. The Air Force restored a number of UH-34J Seabats from the 309th Aerospace Maintenance and Regeneration Group (AMARG) “boneyard” at Davis-Monthan Air Force Base in Arizona. They renamed them HH-34Js and referred to them as Choctaws, embracing the Army name.
In Combat
In the 1950s and 1960s, while top-level military strategists focused on nuclear war, command-level military leaders had to fight a number of limited conventional wars. These were sometimes referred to as brushfire wars, but two were far too big for that adjective. The Algerian War from 1954 to 1961 and the war in Southeast Asia were both limited but large conventional wars. Together, they developed and refined technology, tactics, and training for helicopter assault and other combat roles.
Algeria
The war in Southeast Asia has been called the first helicopter war. It was not the first war to use helicopters, but it brought the use of helicopters to a high state of development. However, the French war in Algeria from 1954 to 1962 also has a claim in the title. It pioneered many of the roles later seen in Southeast Asia and brought them to a considerable level of development.
During World War II, the French had promised independence to Algeria. After the war, pressure from non-African colonists led the government to renege on that promise. This led to an indigenous Muslim war for independence. After the French were defeated in Indochina, they were determined not to lose their fight Algeria. The war that resulted eventually involved a million French troops. In the 1950s and the beginning of the 1960s, Europe’s attention was riveted by the messy and brutal war to put down native revolutionaries. In many ways, it was to Europe what the war in Southeast Asia was to the United States. In fact, the Algerian War was even more unsettling to France. It resulted in a military coup attempt against Charles De Gaulle.
Like America, France had three air arms. In the regular French military, France had the French Air Force (Armée de L’air), the French Navy’s air arm (Aéronavale), and the Aviation Légère de l’Armée de Terre, (ALAT), which was the light air arm of the Army. All three used helicopters, beginning with Korean War era Bell 47s (H-13s) and Sikorsky H-19 Chickasaws. They soon began upgrading to the newer H-21s and H-34s. The Navy and ALAT primarily adopted the H-21, while the Air Force mostly procured the H-34. However, all services sometimes used both types.
With these modern birds, the French forces pioneered troop assault, large-scale resupply, and especially the gunship role. The H-34 sometimes had forward-firing rockets and machine guns, as well as side-firing 50 caliber machine guns and even a 20 mm cannon firing through the door on the port side.
Without the forward-firing weapons, it was common to have two 50-caliber machine guns firing out left-side windows, a 50-caliber machine gun, and a 20 mm cannon firing from the right side. The French also saw the need to armor the pilots’ seats.
Adopting a pattern that Americans would adopt in Southeast Asia, large aircraft were centrally controlled by the Air Force and the Navy, while helicopters were often assigned to specific ground units, giving these units in effect organic air support.
A critical mission for all combat helicopters is medical evacuation. Although services have dedicated medevac helicopters, every combat helicopter was used to evacuate the wounded. The French engaged heavily in this helicopter role in Algeria.
During the war, the French became major builders of H-34s. They initially purchased some H-34s from Sikorsky. After these aircraft proved effective, Sud Est assembled 134 helicopters from Sikorsky kits, then built another 166 domestically.
Southeast Asia
By the time the war began in Southeast Asia, the H-34 was past its prime. The Army still used it heavily in Europe, but its days in Army use were numbered. The smaller UH-1 and the bigger CH-47 were the direction of the future. In any case, as noted earlier, the Army only sent H-21s to Southeast Asia. The Navy had retired all of its Seabats or sent them to reserve units. The Marines, who rarely got new shiny equipment, would eventually get the big CH-46Sea Knight. In the meantime, they had to begin the war with their trusty old H-34s.
Marine involvement began in early 1962. Marine Medium Helicopter Squadron (HMM) 362 had been conducting exercises around the Philippines aboard the USS Princeton (LPH-5) when it was ordered to Soc Trang, which was an old Japanese airfield in Vietnam’s delta. This base was also called Marble Mountain based on a nearby geographical formation. HMM 362 had 24 HUS-1s, which would be redesignated UH-34Ds before the end of this year. HMM 362 would be the first significant Marine unit in Vietnam. Others soon followed on a rotating basis.
Within a week, HMM 362 was in action. Its mission, which was also undertaken by other nine HMM squadrons on a rotation basis, was code-named Shufly. The main job of these UH-34D squadrons would be to airlift Army of Vietnam (ARVN) troops in combat assaults. They also served the usual assortment of generic helicopter combat roles, including rescue and resupply, as well as some unusual roles, such as the transfer of livestock.
As soon as Shufly began, pilots dropped their international orange flight suits for khakis to make them less irresistible targets. Second, they welded on a lower set of steps to help their ARVN comrades embark and disembark.
Some aspects of the Sikorsky could not be fixed, however. One was the aircraft’s skin, which was made of magnesium. Magnesium was very light, but it also caught fire and burned at very high temperature. In addition, the relatively weak structure of the H-34 meant that the Sikorsky never became a great gunship like the UH-1 Huey. The Marines only used Hueys as gunships to support H-34s troop and cargo operations.
The Marines time at Soc Trang was limited. Later that year, they swapped bases with an Army H-21 helicopter unit located in the high country in the northern part of Vietnam. H-34s had better performance in the high and hot conditions to the north. The Marines’ new home was Da Nang, which was just below the demilitarized zone. This would be one of the hottest regions in the war.
In 1965, U.S. Marines came to Vietnam for combat duty. Now the Marine Dogs mostly carried American Marines instead of ARVN soldiers. The Marines would engage in a long series of prolonged pitched battles against North Vietnamese regulars. The Dog would be their major vehicle for moving quickly to confront the enemy quickly and spoil enemy tactics.
The UH-34D was intended to be an interim helicopter until the larger and faster Boeing CH-46 Sea Knights could be brought in to replace them in the medium helicopter role. That did not happen until March, 1966. In addition, after the CH-46 “Phrogs” appeared, a series of crashes due to weak tail pylons grounded them until repairs could be made and the Boeing fixes certified. The U.S. gave the last Marine UH-34Ds to the Vietnamese Air Force (VNAF), where the Dogs continued to serve.
Even when the CH-46 was reinstated, it still took a long time to replace Marine CH-34s. UH-34Ds remained in Vietnam until August 1969. This ended over seven years of service, during which 134 of the Marine’s fleet of 462 Dogs were lost in country.
Our HH-34J (58-1366)
In 1971, a few USAF Reserve squadrons had a temporary need for a search and rescue aircraft. To meet this need, the Air Force looked at Navy SH-34Js and liked what they saw. The SH-34J Seabat could operate at night and in any weather. In addition, SH-34Js had an Automatic Stabilization Equipment (auto-hover), which would be invaluable in SAR work. Of course, the ASW equipment would have to be removed, but this would be relatively inexpensive to do. The Air Force redesignated the SH-34J Seabats as HH-34J Choctaws, following Army naming.
Most of the SH-34Js that the Air Force procured for its reserve units came from the Davis-Monthan “boneyard.” They began to reach USAF reserve squadron service in June 1971. In total, the Air Force procured about two dozen. The exact number varies among sources in part because there were transfers among squadrons that confused the count.
Our HH-34J (58-1366) has serial number 148963. During is approximately three years of service, our bird flew with the 301st Aerospace Rescue and Recovery Squadron at Homestead AFB, Florida. This unit engaged in numerous SAR missions. It also performed presidential missions and provides security services for NASA at Cape Kenney.
Characteristics
| UH-34D (Marines) | SH-34J (Navy) | |
|---|---|---|
| Crew (minimum) | 2 | 2 |
| Length | 45’ 9” (14.25 m) | 45’ 9” (14.25 m) |
| Rotor diameter | 56’ 0” (17.07 m) | 56’ 0” (17.07 m) |
| Number of rotor blades | 4 | 4 |
| Height | 15’ 11” (4.85 m) | 15’ 11” (4.85 m) |
| Disk area | 2,463 ft2 (228.85 m2) | 2,463 ft2 (228.85 m2) |
| Empty weight | 7,900 lb (3583 kg) | 8,275 lb (3753 kg) |
| Useful load | 6,100 lb (2967 kg) | 5,725 lb (2597 kg) |
| Maximum take-off weight | 14,000 lb (6350 kg) | 14,000 lb (6350 kg) |
| Powerplant | 1x Wright R-1820-84 | 1x Wright R-1820-84 |
| Power | 1,525 hp (1,137 kW) | 1,525 hp (1,137 kW) |
| Maximum speed | 122 mph (106 kt, 196 km/h) | 121 mph (105 kt, 194 km/h) |
| Cruise speed | 97 mph (84 kt, 156 km/h) | 97 mph (84 kt, 156 km/h) |
| Range | 215 mi (346 km) | 255 mi (410 km) |
