Tag Archives: Helicopter

22 May 1968

Los Angeles Airways’ Sikorsky S-61L N300Y at Disneyland Heliport, Anaheim, California. This is the sister ship of N303Y, and it would also be destroyed in a catastrophic accident, 14 August 1968. (Sikorsky Historical Archives)
Los Angeles Airways’ Sikorsky S-61L N300Y at Disneyland Heliport, Anaheim, California. This is the prototype S-61L and the sister ship of N303Y. It would also be destroyed in a catastrophic accident, 14 August 1968. (Sikorsky Historical Archives)

22 May 1968: Los Angeles Airways Flight 841, a Sikorsky S-61L, N303Y, was enroute from Disneyland, Anaheim, California, to Los Angeles international Airport (LAX). Captain John E. Dupies and First Officer Terry R. Herrington were in the cockpit, while Flight Attendant Donald P. Bergman was in the passenger cabin with twenty passengers. The flight was cruising on a westerly heading at 2,000 feet (610 meters) when the five main rotor blades “underwent a series of extreme over-travel excursions in their lead/lag axis.”

The five main rotor blades are identified by color markings: red, black, white, yellow and blue (clockwise as seen from above). As the black blade oscillated fore and aft, the geometry of the pitch change control rods to the blades changed, rapidly varying the blades’ pitch angle and therefore, the lift and drag they produced. This put extreme overloads on the pitch control rods and and the rod controlling the yellow blade failed. The yellow blade was no longer in control. The extreme dynamic changes in the blade’s motion was transmitted to the white blade which also went out of control, followed by the other three blades. All five blades diverged from the normal tip-path plane and began to strike each other and the helicopter’s fuselage. The yellow blade was driven out of its normal sequence between the white and blue blades and struck the fuselage at the baggage door with its top flat against the fuselage side. It broke into five sections then wrapped around the rotor mast. All blades were destroyed. The helicopter, completely out of control, fell nearly vertically to the ground. The crew radioed, “L.A., we’re crashing. Help us.”

At 5:51 p.m., Pacific Daylight Time, Flight 841 crashed on Alondra Boulevard near Minnesota Street in the city of Paramount. The aircraft was completely destroyed by the impact and post-crash fire. All 23 persons on board were killed.

The crash scene of Los Angeles Airways Flight 841, along Alondra Blvd, Paramount, California, 22 May 1968. One main roto rblade can be seen protruding from a building's roof, nearby. (Unattributed)
The crash scene of Los Angeles Airways Flight 841, along Alondra Blvd, Paramount, California, 22 May 1968. One main rotor blade can be seen on a building’s roof, nearby. (Unattributed)

The National Transportation Safety Board (NTSB) investigation determined that the probable cause of the accident was a failure of the black blade’s lead/lag hydraulic damper or a loss of effectiveness of the white blade’s damper. The reason for this failure was not determined.

Captain “Jack” Dupies was a veteran pilot with Los Angeles Airways, having worked for the airline since 1953. He had a total of 12,096 flight hours with 4,208 hours in the S-61. First Officer Herrington had a total of 872 flight hours with 589 hours in helicopters. He had joined Los Angeles Airways in January 1968.

Sikorsky S-61L N303Y, s/n 61060, was completed in June 1962. At the time of the crash, it had accumulated 11,128 total hours on the airframe. It had undergone a complete 2,400-hour overhaul approximately 6 months earlier.

The Sikorsky S-61L was a civil variant of the United States Navy HSS-2 Sea King, and was the first helicopter specifically built for airline use. The prototype, N300Y, first flew 2 November 1961. It is a large twin-engine helicopter with a single main rotor/tail rotor configuration. Although HSS-2 fuselage is designed to allow landing on water, the S-61L is not amphibious, having standard fixed landing gear rather than the sponsons of the HSS-2 (and civil S-61N). The S-61L fuselage is 4 feet, 2 inches (1.270 meters) longer than that of the HSS-2. The S-61L is 72 feet, 7 inches (22.123 meters) long and 16 feet, 10 inches (5.131 meters) high, with rotors turning.

The main rotor has five blades and a diameter of 62 feet (18.898 meters). Each blade has a chord of 1 foot, 6.25 inches (0.464 meters). The tail rotor also has five blades and a diameter of 10 feet, 4 inches (3.149 meters). They each have a chord of 7–11/32 inches (0.187 meters). At 100% r.p.m., the main rotor turns 203 r.p.m. and the tail rotor, 1,244 r.p.m. The main rotor turns counter-clockwise, as seen from above. (The advancing blade is on the helicopter’s right side.) The tail rotor turns clockwise, as seen from the left side. (The advancing blade is below the axis of rotation.)

N303Y was powered by two General Electric CT58-140-1 turboshaft engines, each of which had maximum power rating of 1,400 shaft horsepower for takeoff and 1,500 SHP for 2½ minutes. The main transmission was rated for 2,300 horsepower, maximum.

The S-61 has a cruise speed of  166 miles per hour (267 kilometers per hour).  The service ceiling is 12,500 feet (3,810 meters). The maximum takeoff weight is 20,500 pounds (9,298.6 kilograms).

Between 1958 and 1980, Sikorsky built 794 S-61 series helicopters. 13 were S-61Ls. As of September 2013, two remained in service.

Diagram of Sikorsky S-61L rotor head. (NTSB)
Diagram of Sikorsky S-61L rotor head. (NTSB)

© 2015, Bryan R. Swopes

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21 May 1949

Captain Hubert D. Gaddis, USAAF with teh Sikorsky S-51-1. NAA representatives check baraographs. (Sikorsky Archives)
Captain Hubert D. Gaddis, United States Army, with the Sikorsky S-52-1 NX92824. NAA representatives Walter Goddard and Charles Logsdon check the barographs. (Sikorsky Archives)
Captain Hubert D. Gaddis, Artillery, United States Army. (FAI)
Captain Hubert Dale Gaddis, Field Artillery, United States Army. (FAI)

21 May 1949: Captain Hubert Dale Gaddis, Field Artillery, United States Army, flew a prototype  Sikorsky S-52-1 helicopter, registration NX92824, to a Fédération Aéronautique Internationale (FAI) World Record for Altitude Without Payload of 6,468 meters (21,220 feet)¹ at Bridgeport, Connecticut.

The Sikorsky S-52-1 was an completely new design helicopter based on the company’s experience with the earlier R-4 and R-5/S-51 models. It was of all metal monocoque construction, using primarily aluminum and magnesium.

The three-bladed fully-articulated articulated main and two-bladed tail rotor were also of all metal construction. The main rotor had a diameter of 33 feet (10.058 meters) and rotated counter-clockwise as seen from above. (The advancing blade is on the right side of the helicopter.) The semi-rigid tail rotor was mounted on the left side of the tail boom in a pusher configuration. It had a diameter of 6 feet, 4 inches (1.930 meters) and rotated counter clockwise, as seen from the helicopter’s left. (The advancing blade is at the top of the tail rotor arc.)

The S-52-1 was powered by a 425.29-cubic-inch-displacement (6.969 liter) air-cooled Franklin 6V6-245-B16F (O-425-1) vertically-opposed 6-cylinder engine, which produced 245 horsepower at 3,275 r.p.m.

On 27 April 1949 Sikorsky test pilot Harold E. “Tommy” Thompson flew the same helicopter to an FAI speed record of 208.49 kilometers per hour (129.55 miles per hour) over a 3 kilometer straight course (Record File Number 13097), and on 6 May, to 197.54 kilometers per hour (122.75 miles per hour) over a 100-kilometer closed circuit (Record File Number 13146).

Sikorsky S-52-1 NX92824 (FAI)
Sikorsky S-52-1 NX92824 (FAI)

¹ FAI Record File Number 2181

© 2016, Bryan R. Swopes

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17 May 1942

Sikorsky XR-4 41-18874 at Wright Field, Ohio, 17 May 1942. (Sikorsky Historical Archives)
Sikorsky XR-4 41-18874 at Wright Field, Ohio, 17 May 1942. (Sikorsky Historical Archives)

17 May 1942: After a 761 mile (1,224.7 kilometer) flight over five days, test pilot Charles Lester (“Les”) Morris and Igor Sikorsky arrived at Wright Field, Dayton, Ohio, to deliver the U.S. Army’s first helicopter, the Sikorsky XR-4. Morris hovered directly up to the base administration building and landed there. He and Sikorsky were greeted by a large group of people which included Lieutenant Colonel Hollingsworth Franklin (“Frank”) Gregory, the Army’s designated rotorcraft expert, and pioneer aviator Orville Wright.

The Sikorsky XR-4 41-18874 at Wright Field, 17 May 1942. Left to right: E. Walsh, A. Planefisch, Igor Sikorsky, Orville Wright, R. Alex, Les Morris, B. Labensky. (Sikorsky Archives)
The Sikorsky XR-4 41-18874 at Wright Field, 17 May 1942. Left to right: E. Walsh, A. Planefisch, Igor Sikorsky, Orville Wright, R. Alex, Les Morris, B. Labensky. (Sikorsky Historical Archives)

From the Sikorsky factory at Stratford, Connecticut, to Wright Field, Ohio, was 761 miles (1,224.7 kilometers), direct. Because of the XR-4’s low speed and short range (weight limitations restricted the quantity of gasoline it could carry) the distance was covered in sixteen separate flights with a total flight time of 16 hours, 10 minutes. The longest single flight lasted 1 hour, 50 minutes, a new world’s record for helicopter flight endurance. Igor Sikorsky joined Les Morris for the final leg of the flight.

The XR-4 was derived from Igor Sikorsky’s experimental VS-300. The company designation was VS-316A. When turned over to the Army, it was assigned serial number 41-18874. At Wright Field the new helicopter was used for flight testing. The Army, Navy and Coast Guard each ordered several production R-4Bs. After an engine upgrade, the XR-4 was redesignated XR-4C. Today, the first military helicopter is at the Smithsonian Institution National Air and Space Museum’s Steven F. Udvar-Hazy Center.

Sikorsky XR-4C 41-18874 at the National Air and Space Museum. (NASM)

© 2015, Bryan R. Swopes

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16 May 1977

Sikorsky S-61L N619PA
New York Airways’ Sikorsky S-61L, N916PA. (Photograph by Stefan Sjögren, used with permission.)

16 May 1977: At approximately 5:32 p.m. Eastern Standard Time, New York Airways Flight 971, a Sikorsky S-61L helicopter, landed at the Pan Am Building rooftop heliport (JPB) in New York City. Flight 971 had originated at John F. Kennedy International Airport (JFK) and carried 20 passengers and a crew of three. The helipad was 855.23 feet (260.67 meters) above Sea Level.

In the cockpit’s right seat was Captain Lee G. Richmond. Captain Richmond had 11,721 total flight hours with over 9,000 in helicopters and approximately 2,200 in the Sikorsky S-61. He had worked for New York Airways since 1964. The co-pilot was First Officer John F. Flanagan had worked for NYA for about five weeks. He had 1,768.4 flight hours with 1,339.2 hours in helicopters. Both pilots had flown 3 hours, 33 minutes on 16 May. Flight Attendant Lammie Chevalier had been employed by NYA for four years.

A Sikorsky S-61L hovers over the Pan Am Building heliport. (Unattributed)
A New York Airways Sikorsky S-61L hovers over the Pan Am Building heliport. (Pan Am)

Captain Richmond taxied the S-61 into position on the 131-foot × 131-foot (39.9 × 39.9 meters) concrete helipad. While parked at the gate, Richmond kept the rotors turning at 100%, keeping the cyclic control centered and the collective full down (negative pitch). The Automatic Flight Control System (AFCS) was engaged. Flanagan kept his left knee against the collective pitch lever to ensure that it remained full down. Flight Attendant Chevalier stood inside the passenger cabin, supervising departing and boarding passengers.

The return flight to JFK was designated Flight 972.

Aerial photo of the wreck of Flight 972 atop the Pan Am Building, 16 May 1977. (Neal Boenzi/The New York Times)
Aerial photo of the wreck of Flight 972 atop the Pan Am Building, 16 May 1977. (Neal Boenzi/The New York Times)

2 minutes, 21 seconds after touch down, at approximately 5:35 p.m., the right main landing gear of the helicopter failed and the S-61 rolled over to the right. All main rotor blades struck the concrete helipad. Four passengers who were waiting to board were struck by the blades and killed. One of the blades, 28 feet, 10 inches (8.787 meters) long and weighing 209.3 pounds (94.9 kilograms) flew out over the building’s railing and fell alongside the building before crashing through an office window on the 36th floor. The main rotor blade broke into two segments, one of which fell to the street below, striking a pedestrian and killing him. Additional pieces of the main rotor blades were found up to four blocks north of the Pan Am Building.

Wreck of S-61L N619PA at the Pan Am Building rooftop heliport, 16 May 1977. (Unattributed)
Wreck of S-61L N619PA at the Pan Am Building rooftop heliport, 16 May 1977. The Chrysler Building is in the background. (Unattributed)

The helicopter assigned to Flight 971/972 was a Sikorsky S-61L, s/n 61427, registered N619PA. At the time of the accident, the helicopter had a total of 6,913:15 hours on the airframe. Just 7 hours, 22 minutes had elapsed since the last major inspection.

The National Transportation Safety Board (NTSB) investigation determined that the probable cause of the accident was: “. . . the fatigue failure of the upper right forward fitting of the right main landing gear tube assembly. Fatigue originated from a small surface pit of undetermined source. All fatalities were caused by the operating rotor blades as a result of the collapse of the landing gear.”

The NTSB determined that the flight crew had performed correctly, and that the aircraft was properly certified, maintained and operated. The Board speculated that the four boarding passengers would have been killed by the helicopter rolling over, even if the engines had been shut down and rotors stopped.

Sikorsky S-61L N619PA lies on its right side at the Pam Am Building heliport, May 1977. The Empire State Building is in the background. (Unattributed)
Sikorsky S-61L N619PA lies on its right side at the Pam Am Building heliport, May 1977. The Empire State Building is in the background. (Unattributed)

A similar accident had occurred when a Los Angeles Helicopters Sikorsky S-61L suffered a fatigue fracture of its right landing gear and rolled over at Los Angeles International Airport (LAX) in 1963. This accident had resulted in a change in the material used to manufacture the parts.

The Sikorsky S-61L was a civil variant of the United States Navy HSS-2 Sea King, and was the first helicopter specifically built for airline use. The prototype, N300Y, first flew 2 November 1961. It is a large twin-engine helicopter with a single main rotor/tail rotor configuration. Although HSS-2 fuselage is designed to allow landing on water, the S-61L is not amphibious, having standard fixed landing gear rather than the sponsons of the HSS-2 (and civil S-61N). The S-61L fuselage is 4 feet, 2 inches (1.270 meters) longer than that of the HSS-2. The S-61L is 72 feet, 7 inches (22.123 meters) long and 16 feet, 10 inches (5.131 meters) high, with rotors turning.

The main rotor has five blades and a diameter of 62 feet (18.898 meters). Each blade has a chord of 1 foot, 6.25 inches (0.464 meters). The tail rotor also has five blades and a diameter of 10 feet, 4 inches (3.149 meters). They each have a chord of 7–11/32 inches (0.187 meters). At 100% r.p.m., the main rotor turns 203 r.p.m. and the tail rotor, 1,244 r.p.m. The main rotor turns counter-clockwise, as seen from above. (The advancing blade is on the helicopter’s right side.) The tail rotor turns clockwise, as seen from the left side. (The advancing blade is below the axis of rotation.)

N619PA was powered by two General Electric CT58-140-2 turboshaft engines, each of which had maximum power rating of 1,400 shaft horsepower for takeoff and 1,500 SHP for 2½ minutes. The main transmission was rated for 2,300 horsepower, maximum.

The S-61 has a cruise speed of  166 miles per hour (267 kilometers per hour). The service ceiling is 12,500 feet (3,810 meters). The maximum takeoff weight is 20,500 pounds (9,298.6 kilograms).

Between 1958 and 1980, Sikorsky built 794 S-61 series helicopters. 13 were S-61Ls. As of May 2017, two remained in service.

© 2017, Bryan R. Swopes

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6–7 May 1943

Colonel Frank Gregory lands the Vought-Sikorsky XR-4, 41-18864, aboard SS Bunker Hill, 6-7 May 1943. (Sikorsky Historical Archives)
Colonel Frank Gregory lands the Vought-Sikorsky XR-4, 41-18874, aboard SS Bunker Hill, 6-7 May 1943. (Sikorsky Historical Archives)

6–7 May 1943: To determine the feasibility of operating helicopters from the decks of merchant ships for antisubmarine patrols, Colonel Hollingsworth Franklin (“Frank”) Gregory, U.S. Army Air Corps, made 23 landings and takeoffs from the tanker SS Bunker Hill in Long Island Sound, flying the Army’s Vought-Sikorsky XR-4, 41-18874.

According to an official U.S. Coast Guard history of the tests,

The tanker BUNKER HILL was made available for the tests and a deck 78 feet [23.8 meters] long, with obstructions at both ends, was put in place. An eight foot [2.4 meters] bullseye in the center of a square was painted in the middle of the platform. Colonel Frank Gregory arrived on 6 May to fly the Army XR-4 provided for the tests. The entire helicopter project rested on the XR-4’s ability to land on a ship. Gregory was concerned at first. His “shipboard” experience was limited to a 20 foot [6.1 meters] platform at Wright Field. He immediately set about getting “additional experience.” Gregory noted with reference to his first attempt:

Igor Sikorsky and Colonel Frank Gregory with the Vought-Sikorsky XR-4. (Sikorsky Historical Archives)
Igor Sikorsky and Colonel Frank Gregory with the Vought-Sikorsky XR-4. (Sikorsky Historical Archives)

“The space on the deck looked even smaller—it didn’t look like the helicopter would fit. The cabin superstructure towered up like a two story building, and the people on it had that “it can’t be done” look on their faces—yet the big white bullseye stuck out like a target—the XR-4 came true to the white marker as though being pulled by a powerful magnet, and a minute later the floats touched the deck.”

He continued to practice landings and takeoffs that afternoon with the ship at anchor, then underway at five, seven and one-half, ten and fifteen knots. As the speed increased the landings became more difficult because of increased turbulence over the superstructure but the helicopter proved to be completely controllable.

The next morning guests were ferried out to the BUNKER HILL . . . A total of 97 names were on the guest list. Gregory put on an impressive and flawless performance as the ship cruised at various speeds up to 15 knots and on various headings with relation to the wind which was blowing at 12 knots. . . .

—”The Helicopter as an Anti-Submarine Weapon,” A History of Coast Guard Aviation, The Growth Years (1939–1956).

SS Bunker Hill, a Type T2 tanker, with a tugboat alongside. (Unattributed)
SS Bunker Hill, a Type T-2 tanker, with a tugboat alongside. (Unattributed)

SS Bunker Hill was a 10,590 gross ton Type T-2 tanker owned by the Keystone Tankship Corporation. It was  504 feet (153.6 meters) long, with a beam of 68.2 feet (20.8 meters) and drawing 39.2 feet (12 meters). Its engine developed 7,000 horsepower.

On 6 March 1964, Bunker Hill was enroute from Tacoma to Anacortes, Washington when it suffered a vapor explosion in the Number 9 cargo tank which broke the ship in half. It sank in Rosario Strait in less than one hour. Five members of the crew of thirty-one, including the captain, chief mate, third mate, quartermaster and steward, were lost.

The Vought-Sikorsky VS-316A (which was designated XR-4 by the U.S. Army Air Corps and assigned serial number 41-18874), established the single main rotor/anti-torque tail rotor configuration. It was a two-place helicopter with side-by-side seating and dual flight controls. The fabric-covered three-blade main rotor was 38 feet (11.582 meters) in diameter and turned counter-clockwise as seen from above. (The advancing blade is on the helicopter’s right). The three-blade tail rotor was mounted to the right of the tail boom in a tractor configuration, and rotated clockwise when seen from the helicopter’s left side. (The advancing blade was below the axis of rotation.)

The XR-4 was 33 feet, 11.5 inches (10.351 meters) long and 12 feet, 5 inches (3.785 meters) high. It weighed 2,010 pounds (911.7 kilograms) empty and the maximum gross weight was 2,540 pounds (1,152.1 kilograms).

The VS-316A had originally been powered by a 499.8-cubic-inch-displacement (8.19 liter) air-cooled Warner Scarab SS-50 (R-500-1) seven-cylinder radial engine, rated at 145 horsepower at 2,050 r.p.m. In the XR-4 configuration, the engine was upgraded to an air-cooled, direct-drive 555.298-cubic-inch-displacement (9.100 liter) Warner Super Scarab SS185 (R-550-3) seven-cylinder radial engine with a compression ration of 6.20:1. The R-550-3 was rated at 185 horsepower at 2,175 r.p.m. at Sea Level, and 200 horsepower at 2,475 r.p.m (five minute limit) for takeoff. The engine was placed backwards in the aircraft with the propeller shaft driving a short driveshaft through a clutch to a 90° gear box and the transmission. The R-550-3 weighed 344 pounds (156 kilograms).

The XR-4 was redesignated XR-4C. This would be the world’s first production helicopter. It is at the Steven F. Udvar-Hazy Center of the Smithsonian National Air and Space Museum.

Vought-Sikorsky XR-4 41-18874 during shipboard testing, June 1943. (Sikorsky Historical Archives)
Vought-Sikorsky XR-4 41-18874 during shipboard testing, June 1943. (Sikorsky Historical Archives)

© 2017, Bryan R. Swopes

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