21 September 1961: Boeing Vertol YCH-1B-BV, serial number 59-4983, a twin-turboshaft, tandem-rotor heavy lift helicopter, flown by test pilot Leonard Joseph (“Len”) LaVassar, made its first flight at Morton Grove, Pennsylvania. This aircraft was the number two prototype. (The first aircraft, 52-4982, had been damaged 12 July 1961 when the rotors went out of phase during ground testing. It was repaired but never flew.) In 1962, the YCH-1B was was redesignated YCH-47A.
The YCH-1B fuselage was 51 feet, 0 inches (15.545 meters) long and had a maximum width of 12 feet, 5 inches (3.785 meters). The helicopter’s overall length, with rotors turning, was 98 feet, 3.25 inches (29.953 meters), and its maximum height (to the tip of the uppermost blade) was 18 feet, 6.6 inches (5.654 meters). Empty weight of the production CH-47A is approximately 25,500 pounds.
The counter-rotating fully-articulated three-bladed rotors each had a diameter of 59 feet, 1.25 inches (18.015 meters). The forward rotor turned counter-clockwise, as seen from above. (The advancing blade is on the helicopter’s right side.) The rear rotor turns the opposite direction. They rotate at 215 r.p.m.
The prototypes were powered by two Lycoming LTC4B-3 (T55-L-5) turboshaft engines. These were free-turbine engines using a 7-stage axial-flow, 1-stage centrifugal-flow compressor section with a single-stage high-pressure turbine and two-stage low-pressure power turbine. The T55-L-5 was rated at 1,870 shaft horsepower at 14,430 r.p.m. N2. It was 3 feet, 8.1 inches (1.120 meters) long and weighed 560 pounds (254 kilograms).
The helicopter had a maximum speed of 153 knots (176 miles per hour/283 kilometers per hour) at Sea Level. Its hover ceiling, out of ground effect (HOGE), was 11,650 feet (3,551 meters), and in ground effect (HIGE), 14,500 feet (4,420 meters). The helicopter’s service ceiling was 18,600 feet (5,669 meters).
The Chinook remains in production as the CH-47F Block II and MH-47G, and is used by the military services of several nations.
19 September 1969: After four days of testing in a tethered hover, OKB Mil Design Bureau test pilot Herman V. Alferov made the first free flight of the prototype Mil Mi-24 attack helicopter, V-24.
Designed by a team led by Chief Project Engineer V. A. Kuznetsov, the Mi-24 used the drive train of the Mil Mi-8 Hip-B/C transport and Mi-14 Haze-A anti-submarine helicopters. It had a five-blade main rotor. a three-blade tail rotor and was equipped with retractable tricycle landing gear.
The Mi-24 (named “Hind” by NATO forces) was operated by a pilot and a weapons system operator seated in tandem configuration, with the pilot slightly offset to the left. The gunner is in the forward position. It differed from the American Bell AH-1G Cobra attack helicopter in that it could carry 8 troops or 1,500 pounds (680 kilograms) of cargo in a center fuselage compartment.
The Mi-24 is 17.5 meters (57 feet, 5 inches) long, 6.5 meters (21 feet 4 inches) high, with a main rotor diameter of 17.3 meters (56 feet, 9 inches). As is standard practice with Soviet helicopters, the five-blade main rotor turns clockwise as seen from above. (The advancing blade is on the left.) The tail rotor diameter is 3.9 meters (12 feet, 9½ inches).
The entire fuselage is tilted 2° 30′ (and thus, the transmission, mast and main rotor) to the right to counteract the rotor system’s translating tendency, and helps with high-speed stability.
In early versions, the tail rotor was mounted on the right side in pusher configuration and rotated counter-clockwise as seen from the left. (The advancing blade is above the axis of rotation.) Because of poor handling conditions, the tail rotor was changed to the left side in tractor configuration, with the advancing blade below the hub.
The helicopter’s empty weight is 8,500 kilograms (18,739 pounds) and loaded weight is 12,000 kilograms (26,455 pounds).
Power is supplied by two Isotov TV3-117 turboshaft engines rated at 1,700 shaft horsepower, or 2,200 horsepower for takeoff or one engine inoperative emergency operation.
The Mi-24 has a maximum speed of 335 kilometers per hour (208 miles per hour) and range of 450 kilometers (280 miles). The service ceiling is 4,500 meters (14,764 feet).
Armament consists of a turret-mounted Gryazev-Shipunov GSh-23 23mm cannon with 450 rounds of ammunition. Air-to-air and air-to-ground missiles are carried on pylons mounted under the helicopter’s stub wings.
More than 5,200 Mi-24 attack helicopters have been built, many of them exported. It is estimated that the cost of an individual helicopter is $32,500,000.
Herman V. Alferov (Алфёров Герман Витальевич)—also known as G.V. Alferov or German V. Alferov—was born at Moscow, Russia, U.S.S.R., 11 April 1934. He graduated from the 3rd Moscow Flying Club in 1950, and from 1952 to 1954 was a flight instructor at the Central Aeroclub Chkalov. In 1954, He graduated from the Voluntary Society of Assistance to the Air Force (DOSAAF) central flight technical school at Saransk in the Mordovian Autonomous Oblast.
Alferov was employed as a test pilot at OKB Mil in Moscow from 1954 until 1982, and remained with the flight test center until 1992. He participated in setting 11 Fédération Aéronautique Internationale (FAI) world helicopter records, and was named an Honored Test Pilot of the Soviet Union, 16 November 1973. In 1977, he was awarded the Order of the October Revolution, twice received the Order of the Red Banner of Labor, and twice the Order of the Red Star.
14 September 1939: At Stratford, Connecticut, Igor Sikorsky made the first tethered flight of the Vought-Sikorsky VS-300 prototype helicopter. The duration of the flight was just 10 seconds but demonstrated that the helicopter could be controlled.
The Vought-Sikorsky VS-300 was the first successful single main rotor, single tail rotor helicopter.
The three-bladed main rotor had a diameter of 28 feet (8.534 meters) and turned approximately 255 r.p.m. The rotor turned clockwise as seen from above (the advancing blade is on the left). This would later be reversed. A counter-weighted single blade anti-torque rotor with a length of 3 feet, 4 inches (1.016 meters) is mounted on the left side of the monocoque beam tail boom in a pusher configuration and turns counter-clockwise as seen from the helicopter’s left (the advancing blade is above the axis of rotation).
In the initial configuration, the VS-300 was powered by an air-cooled, normally-aspirated, 144.489-cubic-inch-displacement (2.368 liter) Lycoming O-145-C3 horizontally-opposed, four-cylinder, direct-drive engine with a compression ratio of 6.5:1. It was rated at 75 horsepower at 3,100 r.p.m., using 73-octane gasoline. It was equipped with a single Stromberg carburetor and dual Scintilla magnetos. The dry weight of the O-145-C3 was 167 pounds (75.75 kilograms). Later in the VS-300’s development, the Lycoming was replaced by a 90-horsepower Franklin 4AC-199 engine.
On 19 December 1939, the VS-300 was rolled over by a gust of wind and damaged. It was rebuilt, however, and developed through a series of configurations. It made its first free (untethered) flight 13 May 1940.
Test flights continued for several years. After 102 hours, 32 minutes, 26 seconds of flight, the VS-300 was donated to the Henry Ford Museum, Dearborn, Michigan.
7 September 1965: First flight of the prototype Bell Model 209 attack helicopter. Test pilot William Thomas (“Bill”) Quinlan was in command. The duration of the flight was twelve minutes.
The Model 209 was a private venture, built in just seven months and rolled out at Fort Worth, Texas, 2 September 1965. The prototype aircraft combined the drive system, rotors and tail boom of the production UH-1C gunship with a streamlined fuselage which placed the two pilots in tandem.
The prototype was equipped with retractable landing gear which gave the 209 increased speed, but the expense and complexity were enough that this feature was not included on production aircraft.
This helicopter would be developed into the famous AH-1G Huey Cobra.
The second prototype, AH-1G 66-15246, was used by the Army for flight testing at Edwards Air Force Base, California, from 3 April to 21 April 1967.
66-15246 had an overall length of 52 feet, 11.65 inches (16.146 meters) with rotors turning. The fuselage was 44 feet, 5.20 inches (13.433 meters) long, and it was 3 feet, 0 inches (0.914 meters) wide. The HueyCobra had a short “stub wing” with a span of 10 feet, 11.60 inches (3.343 meters). Its angle of incidence was 14°. The wing’s area was 27.8 square feet (2.6 square meters). 66-15426 had an empty weight of 5,516 pounds (2,502 kilograms) and maximum gross weight of 9,500 pounds (4,309 kilograms).
The two-bladed Model 540 “door-hinge” main rotor was 44 feet, 0 inches (13.411 meters) in diameter. The blades had a chord of 2 feet, 3 inches (0.686 meters) and 10° negative twist. The main rotor turned counter-clockwise when viewed from above. (The advancing blade is on the helicopter’s right.) Normal rotor r.p.m. (power on) was 314–324 r.p.m., and power off, 304–339 r.p.m. The minimum transient rotor speed, power off, was 250 r.p.m.
The two blade tail rotor assembly had a diameter of 8 feet, 6 inches (2.591 meters) with a chord of 8.41 inches (0.214 meters). There was no twist. It was mounted on the left side of the pylon in a pusher configuration and turned counter-clockwise as seen from the helicopter’s left. (The advancing blade is above the axis of rotation.) The tail rotor pylon was cambered to allow aerodynamic forces in forward flight to “unload” the tail rotor.
The AH-1G was powered by a Lycoming LTC1K-4 (T53-L-13) turboshaft engine rated at 1,400 shaft horsepower, though it was derated to the helicopter’s transmission limit. The T53-L-13 is a two-shaft free turbine with a 6-stage compressor (5 axial-flow stages, 1 centrifugal-flow stage) and a 4-stage axial-flow turbine (2 high-pressure stages, 2 low-pressure power turbine stages). The T53-L-13 is 3 feet, 11.9 inches (1.217 meters) long, 1 foot, 11.0 inches (0.584 meters) in diameter and weighs 549 pounds (249 kilograms).
The speed of the Cobra was effected by the armament configuration, whether “clean,” light or heavy scout, or “heavy hog.” At 5,000 feet (1,524 meters), the cruise speed in the clean configuration was 138.0 knots (158.8 miles per hour, 255.6 kilometers per hour); light scout, 134.0 knots (154.2 miles per hour, 248.2 kilometers per hour); and heavy hog, 127.0 knots (146.2 miles per hour, 235.2 kilometers per hour). The maximum airspeed in level flight was 149.0 knots (171.5 miles per hour, 276.0 kilometers per hour); 144.0 knots (165.7 miles per hour, 266.7 kilometers per hour); and 136.5 knots (157.1 miles per hour, 252.8 kilometers per hour), respectively.
The limiting airspeed (VNE) was 190 knots (KCAS) (219 miles per hour, 352 kilometers per hour) below 3,000 feet (914 meters) density altitude.
In autorotation, the airspeed for the minimum rate of descent was 74.0 knots (85.2 miles per hour, 137.1 kilometers per hour) with the main rotor turning 294 r.p.m., resulting in a rate of descent of 1,750 feet per minute (8.89 meters per second).
The basic armament for the AH-1G Cobra was an Emerson M28 turret which could be equipped with one or two General Electric M134 Miniguns, or a combination of a Minigun with a Philco Ford M129 automatic grenade launcher, or two grenade launchers. Each Minigun was supplied with 4,000 rounds of 7.62 NATO ammunition, while a grenade launcher had 300 rounds of 40 × 53 millimeter high-velocity explosive ammunition.
Four hardpoints on the stub wing could be loaded with M18 7.62 NATO Minigun pods; XM35 pods, containing a short-barreled General Electric XM195 20 millimeter Gatling gun (a variant of the M61 Vulcan); rocket pods with seven or nineteen 2.75-inch unguided rockets.
The prototype Cobra, Bell Model 209 N209J, is in the collection of the U.S. Army Aviation Museum, Fort Rucker, Alabama, as is the second prototype, 66-15246.
27 August 1990: Four Bell JetRanger helicopters operated by Omniflight Helicopters Inc., arrived at a golf course near Elkhorn, Wisconsin, to pick up various musical artists after a concert at the Alpine Valley Music Theater and to return them to Chicago. They departed at 0040 hours, CDT.
The number three helicopter, Bell JetRanger III (Model 206B-3) serial number 2338, civil registration N16933, was piloted by Jeffrey William Brown of East Chicago, Indiana.
A last minute addition to the passenger complement was electric blues guitarist Stevie Ray Vaughan. Another passenger, Vaughan’s brother, Jimmie Vaughan, switched places with him and boarded a different aircraft.
A first-quarter Moon rose at 12:12 a.m. CST. It was very dark, with thick, patchy fog. The temperature/dew point spread was such that the pilots had to continually wipe heavy condensation from the windshields. Another of the Omniflight pilots later said that the stars were visible when looking up, but that horizontal visibility was variable, with a maximum of about one mile.
Brown, who was not familiar with the area, took off and after about 300 yards, his helicopter banked sharply to the southeast and disappeared into the fog.
The JetRanger impacted a 150-foot hill (45 meters), 0.6 miles away (1 kilometer). It was completely destroyed. All on board were killed. In addition to Brown and Vaughan, the others were Bobby Brooks, Nigel Browne and Colin Smythe, members of Eric Clapton’s tour.
Although the weather was such that the pilot could have reasonably expected to encounter instrument meteorological conditions, Brown did not have an Instrument-Helicopter rating and the Bell 206-series helicopters were not certified for instrument flight.
Below is the accident summary from the National Transportation Safety Board:
NTSB Identification: CHI90MA244 .
The docket is stored on NTSB microfiche number 43569. Nonscheduled 14 CFR Accident occurred Monday, August 27, 1990 in ELKHORN, WI Probable Cause Approval Date: 09/11/1992 Aircraft: BELL 206B, registration: N16933 Injuries: 5 Fatal.
NTSB investigators traveled in support of this investigation and used data obtained from various sources to prepare this aircraft accident report.
FOUR HELICOPTERS WERE BEING USED AT NIGHT TO TRANSPORT A CONCERT GROUP FROM A GOLF COURSE AREA NEAR ELKHORN, WI, TO CHICAGO, IL. AS THE THIRD HELICOPTER (N16933) WAS DEPARTING, IT REMAINED AT A LOWER ALTITUDE THAN THE OTHERS, AND THE PILOT TURNED SOUTHEASTERLY TOWARD RISING TERRAIN. SUBSEQUENTLY, THE HELICOPTER CRASHED ON HILLY TERRAIN ABOUT 3/5 MI FROM THE TAKEOFF POINT. ELEVATION OF THE CRASH SITE WAS ABOUT 100 FT ABOVE THE GOLF COURSE AND 50 FT BELOW THE SUMMIT OF THE HILL. NO PREIMPACT PART FAILURE OR MALFUNCTION WAS FOUND DURING THE INVESTIGATION. PILOTS OF THE OTHER HELICOPTERS REPORTED VFR FLIGHT CONDITIONS WITH SOME FOG. A GROUND WITNESS NEAR THE CRASH SITE REPORTED HAZE AND GROUND FOG OF VARYING INTENSITY WITH PATCHES OF LOW CLOUDS, BUT SAID STARS COULD BE SEEN THROUGH THE FOG.
The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
IMPROPER PLANNING/DECISION BY THE PILOT, AND HIS FAILURE TO ATTAIN ADEQUATE ALTITUDE BEFORE FLYING OVER RISING TERRAIN AT NIGHT. FACTORS RELATED TO THE ACCIDENT WERE: DARKNESS, FOG, HAZE, RISING TERRAIN, AND THE LACK OF VISUAL CUES THAT WERE AVAILABLE TO THE PILOT.