Welcome to This Date in Aviation History, getting of you caught up on milestones, important historical events and people in aviation from April 22 through April 24.
April 22, 1958 – The first flight of the Boeing Vertol CH-46 Sea Knight. From the earliest days of the single-rotor helicopter, designers were faced with the significant problem of yaw caused by the single large spinning rotor disc. Ultimately, that problem was solved by the use of a smaller vertical rotor disc affixed to the tail. This eliminated the yaw induced by the main rotor, and provided control over the direction that the fuselage faced in hover and flight. But that wasn’t the only solution. Another is a tandem tandem rotor helicopter. In a tandem rotor helicopter, two main rotors provide lift rather than just one, and yaw is canceled by having the discs turn in opposite directions. This arrangement has the benefit of a larger center of gravity and greater lift capacity, but it also requires a complex transmission system to turn the rotors in opposite directions.
American designer Frank Piasecki pioneered the use of the tandem rotor helicopter with the HRP Rescuer, and his company, Piasecki Helicopter, went on to create two other tandem rotor designs, with the H-21 Shawnee seeing service early in the Vietnam War. When Piasecki left the company that bore his name in 1955, his old company took the name Vertol the following year. One of their first projects was a new tandem rotor helicopter that received the company designation Vertol Model 107, or V-107. By this time, turboshaft engines had replaced radial engines in many helicopters, and the Model 107 was powered by a pair of Lycoming T53 turboshaft engines, though the early production helicopters were powered by General Electric T58 engines which provided more power. The engines were mounted on either side of the rear rotor pedestal, and were coupled together so that one engine can drive both rotors in the case that one engine fails.
The US Army initially showed interest in the new cargo and transport helicopter, and ordered three prototypes designated the YHC-1, though they soon lost interest in the project. However, the YHC-1 proved the perfect fit for a medium-lift twin-engine helicopter for the US Marine Corps, and they selected Vertol’s helicopter as the CH-46A Sea Knight. The Sea Knight was capable of carrying up to 4,000 pounds of cargo or 17 passengers, and later variants could accommodate up to 25 passengers or 7,000 pounds of cargo. A rear cargo door served as a loading ramp, and could be left open in flight or removed entirely to facilitate parachute drops of troops or materiel. A sling hook attached to the belly can lift up to 10,000 pounds of external cargo. When flying on combat missions, armor plating and guns can be added for self defense.
Though the Sea Knight was also used by the US Navy as their standard utility helicopter, it was in the hands of the Marine Corps where the Sea Knight showed its mettle in battle. By late 1967, the Sea Knight was in action in Vietnam, where it earned its nickname “Phrog” and became the primary Marine Corps utility helicopter, providing troop transport, medevac, search and rescue, vertical replenishment, and basically anything else the Marines could throw at it. But that heavy use came at a cost. By the end of the Vietnam War, more than 100 Sea Knights had been lost due to enemy fire.
The end of the war in Southeast Asia was by no means the end of service for the doughty Sea Knight. It continued to serve the Marine Corps into the 21st century, and took part in all Marine Corps missions from Operaion Urgent Fury on the Island of Grenada to the invasion of Iraq in 2003, where it performed vital combat casualty evacuation (CASEVAC) missions. The Navy retired their fleet of Sea Knights by 2004 in favor of the Sikorsky SH-60 Seahawk, but the Sea Knight flew on for the Marine Corps as it awaited the introduction of the Bell Boeing V-22 Osprey. The Marines finally retired the last of their CH-46s in an official ceremony on August 1, 2015.
April 24, 1980 – US forces launch Operation Eagle Claw to rescue American hostages held at the US Embassy in Iran. Though the United States now considers Iran as an enemy, that wasn’t always the case. Friendly relations between Iran and the US date all the way back to 1856, when the two nations signed a treaty governing commerce and navigation. Iran was neutral during WWII, but an invasion by the British and Soviets forced Reza Shah, the first member of the Pahlavi Dynasty, to abdicate the throne over fears he might support the Axis powers. He was replaced by his young son, Mohammad Reza Shah, known to modern history simply as the Shah of Iran. Throughout the Shah’s 38-year reign, Iran remained a staunch US ally, but that relationship came to an end with the Islamic Revolution of 1979, when the Shah was overthrown and the country was transformed into an Islamic Republic lead by the Ayatollah Khomeini.
Following the Shah’s ouster, the US allowed the exiled ruler to come to America for cancer treatments, but the Ayatollah and his followers wanted the Shah returned to Iran for trial and execution. On November 4, 1979, a group of Iranian students invaded the US Embassy in Tehran and took 52 members of the embassy captive. As the hostage drama dragged into April 1980 with no resolution in sight, US president Jimmy Carter broke off diplomatic negotiations with the Iranian government and decided to mount a military mission to rescue the hostages. The tremendously complex mission involved all four branches of the US military along with the CIA, but ended in a debacle for the US military and a humiliating embarrassment for the US government.
The mission faced many challenges, but perhaps the greatest was distance. Tehran is located far to the north of Iran, and American helicopters from USS Nimitz (CVN 68) had to fly from ships stationed far to the south in the Gulf of Oman. The two-night operation called for eight US Navy Sikorsky RH-53D Sea Stallions to take of from Nimitz and land at a remote location in the desert called Desert One. There they would meet four US Air Force Lockheed EC-130 transports scheduled to arrive the previous day from Masirah Island off the coast of Oman. Three of the transports would be carrying bladders of fuel, while the fourth would carry tactical supplies and soldiers of the US Army’s elite Delta Force, who would be carrying out their first-ever rescue mission. The EC-130s also carried 12 US Army Rangers and Persian-speaking Americans who would act as truck drivers.
After refueling, the plan called for the helicopters to fly the Delta Force commandos to a second staging area known as Desert Two, where they would hide until the following night. Then, CIA agents would pick up the troops and drive them to Tehran in trucks while US Army Rangers flying aboard Lockheed C-141 Starlifters would arrive at the nearby Manzariyeh Air Base and capture it. The Sea Stallions would then fly to a soccer stadium across the street from the embassy while the Delta Force commandos stormed the embassy compound, eliminated the guards, and rescued the hostages. Once everybody was back at the stadium, the helicopters would fly everybody to the captured air base to be evacuated by the waiting C-141 transports. Fighter cover for the mission would be provided by Navy A-7 Corsair IIs and Marine Corps F-4 Phantom IIs flying from Nimitz and USS Coral Sea (CV 43) stationed in the Gulf of Oman.
The extremely complex plan went awry almost from the beginning. While the EC-130s arrived at Desert One without serious incident, the eight helicopters fared much worse. One landed in the desert and was abandoned for mechanical reasons, and its crew was picked up by one of the other helicopters. A second got lost in a sandstorm and returned to Nimitz. Only six of the eight helicopters reached Desert One, and one of those was deemed unserviceable, leaving just five helicopters, too few for the mission. After much debate, commanders on the ground and in Washington decided to abort the rescue attempt.
In preparation for leaving, the helicopters and one of the EC-130s had to be refueled, which meant that both helicopters and fixed-wing aircraft had to be repositioned. Moving the helicopter required a hover taxi, or moving while hovering slightly above the ground. While one of the Sea Stallions was trying to maneuver to a position behind one of the EC-130s, its rotor struck the aircraft’s vertical stabilizer and the helicopter crashed into the wing root of the Hercules. The crash and ensuing fire killed eight US servicemen and one Iranian civilian. The rest of the personnel boarded the remaining helicopters and transports and left, leaving behind two intact Sea Stallions that now serve with navy of the Islamic Republic of Iran. Once the Iranians became aware of the failed rescue attempt, the hostages were dispersed around the country to prevent a second rescue attempt and, though the US prepared and rehearsed for another attempt at rescuing the hostages, it was never carried out. After 444 days in captivity, the Americans were finally released on January 20, 1981, the first day of the administration of President Ronald Reagan.
Analysis of the debacle led to much soul searching in the US military. The lack of effective coordination between the four branches of the armed forces resulted in the creation of the US Special Operations Command (SOCOM) in 1987 to coordinate future missions of special operations forces. To address the difficulties of flying helicopters in nighttime and low visibility, the Army created the 160th Special Operations Aviation Regiment (SOAR), better known as the Night Stalkers. But the mission also demonstrated the need for a new type of aircraft, one that could fly great distances at high speed, yet be able to land vertically while still carrying a useful payload of troops or cargo. That necessity led directly to the development of the Bell Boeing V-22 Osprey tiltrotor.
April 22, 1965 – The first flight of the Transavia PL-12 Airtruk, an agricultural aircraft that was developed from the Bennett Airtruck. The Airtruk’s main duty is to provide aerial topdressing of farm fields, but it has also been converted for use as a cargo aircraft, aerial ambulance, or passenger aircraft, with pilot and one passenger above and four passengers below. The Airtruk is powered by a single six- or eight-cyinder engine, and has the capacity for up to one metric ton of cargo. Transavia built 118 Airtruks between 1966-1993, though only a small number remain airworthy today.
April 23, 1988 – The U.S. government bans smoking on flights of two hours or less. Championed by consumer advocate Ralph Nader, the smoking ban was first put into effect voluntarily by United Airlines in 1971. But with airlines and the tobacco industry fighting any regulation limiting smoking, the US Congress stepped in. The original 1988 ban was later extended to flights of six hours or less in 1990, then extended to all domestic and international flights in 2000. Violating the smoking ban can lead to a fine of as much as $5,000. In 2016, the Federal Aviation Administration also banned the use of electronic cigarettes on all domestic and international flights.
April 23, 1956 – The first flight of the Douglas C-133 Cargomaster, a large cargo aircraft designed to replace the Douglas C-74 Globemaster and the Douglas C-124 Globemaster II. Unlike its traditional, low-winged predecessors, the high wing of the Cargomaster, along with its external landing gear blisters, removed internal obstructions and allowed for greater cargo capacity in the pressurized fuselage. The C-133 was the Air Force’s only production turboprop-powered strategic airlifter (the smaller Lockheed C-130 Hercules is considered a tactical airlifter), and it went straight into production without the construction of any prototypes. Fifty were built, and Cargomasters provided critical airlift duties during the Vietnam War. The C-133 was replaced in the early 1970s by the turbofan-powered Lockheed C-5 Galaxy.
April 24, 2001 – An unmanned Northrop Grumman RQ-4 Global Hawk flies autonomously from Edwards Air Force Base in the US to Australia non-stop and unrefuelled. This flight marked the longest point-to-point flight ever completed by an unmanned aircraft, and took just over 23 hours to complete. The Global Hawk is also the first autonomous aircraft to cross the Pacific Ocean. The Global Hawk has proven to be a versatile and powerful surveillance platform, flying at altitudes of up to 65,000 feet for as long as 35 hours and capable of imaging an area the size of Illinois on a single mission.
April 24, 1990– The Space Shuttle Discovery launches on STS-31 to deploy the Hubble Space Telescope (HST). Named after American astronomer Edwin Hubble, the HST has a 7.9 foot diameter mirror and instruments to observe near ultraviolet, visible and near infrared spectra. Though the HST is not the first space telescope, it is the first designed to be serviced in space by astronauts, and four Space Shuttle missions have performed repairs or upgrades since it was placed in orbit. A fifth mission was canceled after the Space Shuttle Columbia disaster, but one final servicing mission (STS-125) was undertaken by Space Shuttle Atlantis in 2009. The HST is still operating and providing astounding images of deep space, and will hopefully continue to operate until at least 2020. It is scheduled be replaced by the James Webb Space Telescope in 2021.
April 24, 1971 – Soyuz 10 performs the world’s first docking in space. Once the United States had put a man on the Moon in 1969, the Russian space program shifted its emphasis from the Moon to orbital space stations. Salyut 1, the world’s first orbiting space station, was launched on April 19, 1971. Three days later, Soyuz 10 was launched with a crew of three cosmonauts on a mission to rendezvous with the orbiting station. While the Soyuz 10 achieved a soft docking, a malfunction of the automated alignment system prevented a hard docking and the astronauts were unable to transfer to the station. The following Soyuz 11 mission was able to dock successfully, but a malfunctioning air valve on the Soyuz 11 capsule caused the death of the cosmonauts during re-entry to the Earth’s atmosphere.
April 24, 1967 – The death of cosmonaut Vladimir Komarov. Komarov was the sole cosmonaut on board Soyuz 1, the first flight of the Soyuz spacecraft, which had launched from Baikonur on April 23. He was supposed to rendezvous in space with Soyuz 2, but that spacecraft never launched due to thunderstorms. While orbiting the Earth, Komarov’s spacecraft suffered numerous failures of electrical systems, solar panels, and guidance gyroscopes, and he was forced to manually orient his spacecraft for reentry. During descent, the capsule’s parachute failed to open and the spacecraft impacted the ground at speeds estimated as high as 400 mph. Komarov was killed in the crash, becoming the first fatality of any manned space program.
April 24, 1946 – The first flight of the Mikoyan-Gurevich MiG-9, the first jet fighter developed by Mikoyan-Gurevich following WWII. The MiG-9 was powered by a pair of reverse engineered BMW 003 turbojet engines which had powered the German Heinkel He 162. The MiG-9 was a modestly successful first generation fighter, but continuing problems with the engine plagued the project, and the ingestion of gases from the weapons caused frequent engine flameouts at high altitude, a problem that was never fully solved. Nevertheless, Mikoyan-Gurevich produced 610 MiG-9s between 1946-1948, with roughly half of them sent to China.
April 24 , 1946 – The first flight of the Yakovlev Yak-15, a early Soviet jet fighter developed from the Yakovlev Yak-3 piston powered fighter following WWII. The Yak-15 was powered by a reverse-engineered Junkers Jumo 004 turbojet and, with the Saab 21R, the Yak-13 was one of only two piston powered aircraft to enter production after conversion to jet power. The engine was placed under the forward fuselage of the fighter, with the exhaust exiting beneath the pilot, and the removal of the propeller spinner allowed for an air intake in the front. The Yak-15 had numerous problems, particularly kerosene and oil smoke which often filled the cockpit, but the relative ease of flying meant that the aircraft served well as a transition trainer for pilots moving from piston fighters to jet fighters. A total of 280 were built during its brief production run from 1946-1947.
April 24, 1933 – The first flight of the Grumman JF Duck, an amphibious biplane that entered US Navy service in 1935. The JF featured landing gear that could be retracted into the main centerline float which allowed the aircraft to land on water then taxi up onto land. Early versions of the aircraft had provisions for a rear-firing machine gun and a single bomb rack under each wing, but the Duck was used primarily for photographic missions, target towing, scouting, and search and rescue. The JF was only manufactured for two years before production switched to the improved J2F Duck, and only 48 were built.
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