A flight of two U.S. Army OH-58D Kiowa Warrior scout helicopters. (Bell Helicopter)
6 October 1983: First flight of the Bell Helicopter Company Model 406/OH-58D Kiowa reconnaissance helicopter. Developed from the earlier Model 206/OH-58A and OH-58C Kiowa, the D model features a four-blade composite main rotor, an upgraded engine and transmission, and improved avionics. The most visible features are the spherical mast-mounted sighting system above the main rotor and much larger engine/transmission cowling, or “dog house.”
The helicopter was designed with very low level, “nap-of-the-Earth,” (NOE) flight, using terrain and trees for cover. The four-bladed rotor provides more lift and increased responsiveness over the two-bladed semi-rigid rotor of the OH-58A and C.
The mast-mounted sight allows the helicopter to hover behind terrain or trees with just the sight exposed. The sight contains television, thermal imaging and laser range-finding and target designation equipment.
The instrument panel of a Bell OH-58D Kiowa. (Bell Helicopter)
Operated by two pilots, the Bell OH-58D Kiowa is 42 feet, 2 inches (12.852 meters) long, with rotors turning. The four-bladed composite main rotor has a diameter of 35 feet (10.668 meters). As is customary with American-designed helicopters, the main rotor turn counter-clockwise as seen from above. (The advancing blade is on the right side of the aircraft.) The two-blade semi-rigid tail rotor is mounted on the left side of the tail boom and turns clockwise when seen from the left. (The advancing blade is below the tail boom.) The overall height of the OH-58D is 12 feet, 10–5/8 inches (3.928 meters). Empty weight of the helicopter is about 3,500 pounds (1,588 kilograms), depending on installed equipment. This is approximately 15% greater than the maximum gross weight of the OH-58A. The OH-58D has a maximum gross weight of 5,500 pounds (2,495 kilograms).
Power for the Kiowa is supplied by a Rolls-Royce T703-AD-700A (Allison 250-C30R3) turboshaft engine which produces 750 shaft horsepower. The main transmission is limited to transient input of 637 shaft horsepower.
The helicopter can be armed with a fixed, remotely-fired, M3P .50-caliber (12.7 mm) machine gun, a pod carrying seven 2.75-inch (70 mm) rockets, or two AGM-114 Hellfire antitank guided missiles.
The OH-58D has a cruise speed of 95 knots (109 miles per hour/176 kilometers per hour) when armed. Its range is 140 nautical miles (161 miles/259 kilometers). The hover ceiling in ground effect (HOGE) at +15 °C. is 7,500 feet MSL (2,286 meters).
An OH-58D Kiowa decelerates as it approaches trees during gunnery exercises at Fort Lewis, Washington. A .50-caliber machine gun is mounted on the left side of the helicopter. (U.S. Army)
2 October 1970: The U.S. Air Force 1st Special Operations Wing at Hurlburt Field, Florida (Eglin AFB Auxiliary Field #9), took possession of the very first Bell UH-IN Iroquois, UH-1N-BF 68-10772 (Bell Helicopter Co. serial number 31001).
Also known as the “Twin Huey,” the medium-lift helicopter is a two-engine version of the Bell Model 205 (UH-1H). Originally developed for the Canadian Forces as the Bell Model 212, the UH-1N is powered by a Pratt & Whitney T400-CP-400 (the military designation for the commercial PT6T-3 “Twin-Pac”) which consists of two PT6 turboshaft engines mated to a combining gearbox to drive a single output shaft to the helicopter’s main transmission. The combined unit can produce a maximum 1,800 shaft horsepower. If one engine fails, the remaining engine can operate at 900 shaft horsepower for 30 minutes. The T400 is de-rated to the main transmission limit of 1,290 shaft horsepower.
Bell UH-1N 69-6607
The helicopter has other improvements over the Model 205/UH-1D/H Huey. The main rotor blades have a wider chord, producing greater lift. The main transmission is rated for greater power input. The tail boom and tail rotor pylon are strengthened, and the tail rotor has been moved to the opposite side of the pylon, in a tractor configuration instead of the previous pusher configuration. The tail rotor blade rotation is reversed with the advancing blade moving upward into the down flow of the main rotor, making it more efficient. Visual differences are the streamlined nose and the reshaped “dog house” covering the twin engine installation.
Cockpit of a U.S. Air Force/Bell UH-1N Iroquois during a 60° right bank. (A1C Nigel Sandridge, U.S. Air Force)
The U.S. Air Force normally operates the UH-1N with two pilots and a flight engineer, but it can be flown by a single pilot under visual weather conditions, if necessary. It is capable of transporting up to 12 passengers in addition to the three-man crew.
The Bell Helicopter Co. UH-1N Iroquois (Model 212) is 57 feet, 3 inches (17.450 meters) long, with a main rotor diameter of 48 feet, 0 inches (14.630 meters) and tail rotor diameter of 8 feet, 6 inches (2.591 meters). The overall height of the helicopter is 12 feet, 10 inches (3.912 meters) and the fuselage has a maximum width of 9 feet, 5 inches (2.870 meters). The helicopter’s empty weight is 6,032 pounds (2,736 kilograms), depending on installed equipment. The maximum takeoff weight is 10,500 pounds (4,763 kilograms).
The Pratt & Whitney Canada T400-CP-400 has a maximum continuous power rating of 1,530 shaft horsepower at 6,600 r.p.m. at Sea Level.
The helicopter’s cruise speed is 110 knots (127 miles per hour/204 kilometers per hour) and the maximum speed is 128 knots (147 miles per hour/237 kilometers per hour) at Sea Level. The UH-1N has an out-of-ground-effect hover ceiling (HOGE) of 13,000 feet (3,962 meters). The service ceiling is 21,600 feet (6,584 meters). The combat radius is 105 nautical miles (121 statute miles/194 kilometers) maximum ferry range is 565 nautical miles (650 statute miles/1,046 kilometers).
U.S. Air Force Bell UH-1N Iroquois helicopters deploy security personnel. (U.S. Air Force)
The UH-1N can be armed with GAU-16 .50-caliber machine guns or GAU-17 7.62mm “miniguns.”
The UH-1N is operated by the Air Force, the U.S. Navy and Marine Corps, as well as many foreign military services. In civil use, the Bell 212 is the most common medium lift helicopter worldwide and has been for 54 years.
Of the 79 UH-1N helicopters ordered by the U.S. Air Force in 1968, 59 remain in active service (as of September 2015). On 18 March 2024, a UH-1N assigned to the 58th Operations Group, Det 2, at Kirtland Air Force Base, New Mexico, the Air Force’s UH-1N training unit, 69-6650 logged its 20,000th flight hour.
On 24 September 2018, the U.S. Air Force announced that it would replace the UH-1N fleet with 84 Boeing/Leonardo MH-139A Grey Wolfs, with the first aircraft being delivered in 2021. In actuality, the first field-read MH-139A arrived at Malmstrom Air Force Base in Montana in March 2024.
Still in service, UH-1N 68-10772 was photographed in flight 4 May 2022 at Gowen Field, Boise, Idaho. The helicopter was painted in the Southeast Asia camouflage scheme of the 20th Special Operations Squadron, “Green Hornets.”
A Los Angeles Airways Sikorsky S-51 helicopter takes off from the roof of the Terminal Annex Post Office, 1 October 1947. The Los Angeles Times published this photograph 2 October 1947 with the following caption: “NEW MAIL SERVICE — Los Angeles Airways helicopter shown landing on the roof of Terminal Annex Post office yesterday to inaugurate helicopter air-mail service, the first of its kind in the United States. Two flights daily are planned on this run with another to start Oct. 16.” (Los Angeles Times Photographic Archive/UCLA Library)
1 October 1947: Los Angeles Airways began regularly scheduled air mail service in Los Angeles, using the Sikorsky S-51 helicopter.
“. . . the U.S. Civil Aeronautics Board awarded LAA the route authorities to operate local air mail services in Southern California using the Sikorsky S-51. Before long, LAA was operating a twice-a-day mail service between the main downtown post office and Los Angeles International Airport along with a small package air express service.
“With a fleet of five S-51s, LAA’s first year of operations resulted in 700 tons of mail being carried with approximately 40,000 landings throughout the Los Angeles metropolitan area. The small operation maintained a 95% reliability rate and by the time it began its small package air express service in 1953, it was annually moving nearly 4,000 tons of mail a year.
“In July 1951 the CAB awarded LAA’s reliable helicopter operation the rights for passenger services which started in November 1954 with larger Sikorsky S-55 helicopters while the smaller S-51s continued the mail and small package services. . . .”
The S-51 was a commercial version of the Sikorsky R-5 series of military helicopters. It was a four-place, single-engine helicopter, operated by one pilot. The cabin was built of aluminum with Plexiglas windows. The fuselage was built of plastic-impregnated plywood, and the tail boom was wood monocoque construction. The main rotor consisted of three fully-articulated blades built of metal spars and plywood ribs and covered with two layers of fabric. (All metal blades soon became available.) The three bladed semi-articulated tail rotor was built of laminated wood. The main rotor turned counter-clockwise, as seen from above. (The advancing blade is on the helicopter’s right.) The tail rotor was mounted on the helicopter’s left side in a pusher configuration. It turned clockwise as seen from the helicopter’s left.
The helicopter’s fuselage was 41 feet, 7.5 inches (12.687 meters) long. The main rotor had a diameter of 48 feet (14.630 meters) and tail rotor diameter was 8 feet, 5 inches (2.565 meters), giving the helicopter an overall length of 57 feet, 1 inch (17.399 meters). It was 13 feet, 1.5 inches (4.001 meters) high. The landing gear tread was 12 feet (3.7 meters). The S-51 had an empty weight of 4,050 pounds (1,837 kilograms) and maximum takeoff weight of 5,500 pounds (2,495 kilograms). Fuel capacity was 100 gallons (378.5 liters).
The helicopter was powered by an air-cooled, supercharged, 986.749-cubic-inch-displacement (16.170 liter) Pratt & Whitney Wasp Jr. T1B4 (R-985 AN-5) direct-drive, nine-cylinder radial engine which was placed vertically in the fuselage behind the crew compartment. This engine was rated at 450 horsepower at 2,300 r.p.m., Standard Day at Sea Level. The R-985 AN-5 was 48.00 inches (1.219 meters) long, 46.25 inches (1.175 meters) in diameter and weighed 684 pounds (310.3 kilograms) with a magnesium crankcase.
The S-51 had a maximum speed (Vne) of 107 knots (123.1 miles per hour/198.2 kilometers per hour). Range was 275 miles (442.6 kilometers). The service ceiling was 14,800 feet (4,511 meters). The absolute hover ceiling was 3,000 feet (914.4 meters).
Of 220 helicopters in the S-51 series built by Sikorsky, 55 were commercial models.
A Los Angeles Airways Sikorsky S-51. The main rotor hub is covered. (Viewliner)
30 September 1982: H. Ross Perot, Jr. and Jay W. Coburn completed their around-the-world helicopter flight when they landed Spirit of Texas at their starting point at Dallas, Texas. They had flown the single-engine Bell 206L-1 LongRanger II, serial number 45658, civil registration N3911Z, more than 26,000 miles (41,843 kilometers) in 246.5 flight hours over 29 days, 3 hours and 8 minutes.
They had begun their journey 1 September 1982. Perot and Coburn traveled across twenty-six countries. They established a Fédération Aéronautique Internationale (FAI) record for helicopter speed around the world, eastbound, having averaged 56.97 kilometers per hour (35.399 miles per hour). (Class E-1d, FAI Record File Number 1254). They also established a series of point-to-point records while enroute, with the highest speed, an average of 179.39 kilometers per hour (111.47 miles per hour), taking place on 7 September 1982, while flying Spirit of Texas from London to Marseilles (FAI Record File Number 10018).
The Bell Helicopter Company Model 206L-1 LongRanger II is a 7-place light helicopter developed from the earlier 5-place Model 206B JetRanger series. It is designed to be flown by a single pilot in the right front seat, and is certified for Visual Flight Rules.
The 206L-1 is 42 feet, 8 inches (13.005 meters) long, overall, and the two-bladed main rotor is semi-rigid and under-slung, a common feature of Bell’s main rotor design. It has a diameter of 37 feet (11.278 meters) and turns counter-clockwise (seen from above) at 394 r.p.m. (100% NR). (The advancing blade is on the helicopter’s right side.) The rotor blade has a chord of 1 foot, 1.0 inches (0.330 meter) and 11° negative twist. The blade tips are swept.
The two-bladed tail rotor assembly is also semi-rigid and is positioned on the left side of the tail boom in a pusher configuration. It turns clockwise, as seen from the helicopter’s left. (The advancing blade is below the axis of rotation.) The tail rotor diameter is 5 feet, 6.0 inches (1.676 meters).
The LongRanger II is powered by an Allison 250-C28B turboshaft engine. This engine produces 500 shaft horsepower but is de-rated to 435 horsepower, the limit of the main transmission. The engine is mounted above the roof of the fuselage, to the rear of the main transmission. Output shafts lead forward to the transmission and the tail rotor drive shaft aft to the tail rotor 90° gear box. The transmission and rotor mast are mounted angled slightly forward and to the right. This assists in the helicopter’s lift off to a hover, helps to offset its translating tendency, and keeps the passenger cabin in a near-level attitude during cruise flight.
A vertical fin is attached at the aft end of the tail boom. The fin is offset 4° to the right to unload the tail rotor in cruise flight. Fixed horizontal stabilizers with an inverted asymmetric airfoil are attached to the tail boom. In cruise flight, these provide a downward force that keeps the passenger cabin in a near-level attitude. Vertical fins are attached to the outboard ends of the horizontal stabilizers and above the tailboom centerline. The fins are slightly offset to the left and counteract the helicopter’s Dutch roll tendency.
The helicopter has an empty weight of approximately 2,160 pounds (979 kilograms), depending on installed equipment, and the maximum gross weight is 4,050 pounds (1,836 kilograms).
The Model 206L LongRanger first flew in 1974 and the 206L-1 LongRanger II variant entered production in 1978. It was replaced several years later by the 206L-3. The LongRanger remains in production as the Model 206L-4.
Perot had purchased the LongRanger II for $750,000, specifically for this flight. Modifications started immediately and over the next three weeks an additional 151-gallon fuel tank was added giving the helicopter approximately 8 hours’ endurance. “Pop-out floats”—inflatable pontoons that can be deployed for emergency landings on water—were installed. The helicopter also carried a life raft and other emergency equipment and supplies. Additional communication, navigation equipment and radar was installed.
N3911Z aboard a container ship.
During the circumnavigation, the helicopter burned 56,000 pounds (25,400 kilograms) of jet fuel and made 56 fueling stops, including aboard a pre-positioned container ship in the North Pacific Ocean.
The helicopter was donated to the Smithsonian Institution and is on display at the Steven V. Udvar-Hazy Center of the National Air and Space Museum.
Bell 206L-1 LongRanger II s/n 45658, N3911Z, “Spirit of Texas,” on display at the Steven F. Udvar-Hazy Center of the Smithsonian Institution National Air and Space Museum. (NASM)
AV-02, the second prototype Hughes YAH-64 Advanced Attack Helicopter, 74-22248, makes its first free hover at Palomar Airport, California, 30 September 1975. (Boeing)
30 September 1975: At Palomar Airport (CRQ), Carlsbad, California, Hughes Helicopter Company Chief Test Pilot Robert George (“Bob”) Ferry (LTC, USAF, Ret.) and Raleigh Ellsworth (“Bud”) Fletcher made the first flight of the YAH-64 Advanced Attack Helicopter prototype, U.S. Army serial number 74-22248. This aircraft was the second of three prototypes built by Hughes and was identified by the company as AV-02. AV-01 was a ground test prototype, while AV-02 and AV-03 (74-22249) were used for flight testing. The first flight took place one day before the first flight of the rival Bell YAH-63.
Robert G. Ferry, Chief Test Pilot, Hughes Helicopters.
The YAH-64 was designed as a two-place, twin-engine ground attack helicopter. The pilots sit in tandem configuration like the earlier Bell AH-1G Huey Cobra. The prototype was 57.50 feet (17.526 meters) long, with rotors turning, and the fuselage had a length of 49.42 feet (15.063 meters). The overall height of 12.07 feet (3.679 meters). The four-blade fully-articulated main rotor turns counter-clockwise, as seen from above (the advancing blade is on the right), and has a diameter of 48.00 feet (14.630 meters). It turns at 289 r.p.m., giving the blades’ a tip speed of 726.36 feet per second (211.70 meters per second). The main rotor uses elastomeric lead/lag dampers and the blades are retained by laminated V-shaped stainless steel “strap packs” which are flexible to allow blade flapping and feathering. The main rotor is mounted to a hollow static mast with a concentric drive shaft inside.
The four-bladed tail rotor is unusual in that, rather than the blades being evenly spaced at 90° intervals, the blades are spaced at 55° and 125° angles. This allows for significant reductions in noise. The tail rotor is mounted on the left side of a pylon in a pusher configuration, and rotates clockwise as seen from the helicopter’s left (the advancing blade is below the axis of rotation). It has a diameter of 8.33 feet (2.539 meters) and turns 1,411 r.p.m. (tip speed, 727.09 feet per second/221.62 meters per second).
A stub wing provides additional lift in forward flight and can carry various combinations of guided missiles and rockets. It has a span of 16.33 feet (14.977 meters).
Dimensions diagram for Hughes YAH-64 Advanced Attack Helicopter prototype, Development Test 1 configuration. (Hughes Helicopter Company)
In the original configuration, the YAH-64 had a “T-tail” with the horizontal stabilizer attached to the top of the tail rotor pylon. This caused undesirable changes in pitch attitude during flight testing and was changed with the follow-on YAH-64A pre-production prototypes.
The YAH-64 was powered by two prototype General Electric YT700-GE-700 turboshaft engines. These were rated at 1,536 shaft horsepower at 20,000 r.p.m., at Sea Level on a Standard Day. The helicopter carried fuel in two internal tanks with a total capacity of 353 gallons (1,336.25 liters). This gave the two prototypes a mission endurance of 2 hours, 42 minutes.
The two flight test aircraft, 74-22248 and its sister ship 74-22249, were the subject of extensive flight testing during the summer of 1976. At that time, the YAH-64 had an empty weight of 10,495 pounds (4,760 kilograms), loaded weight of 12,242 pounds (5,553 kilograms) and a maximum gross weight 17,900 pounds (8,119 kilograms).
The two YAH-64s were tested at Edwards Air Force Base and the nearby Naval Ordnance Test Station Chine Lake. Additional testing was conducted at Bishop, California (elevation 4,120 feet/1,256 meters) and Coyote Flats (9,500 feet/2,896 meters).
A pre-production YAH-64A Apache in flight, circa 1982. (U.S. Army)
The helicopter could hover out of ground effect (HOGE) at its maximum gross weight at and altitude of 5,350 feet (1,631 meters) with an ambient temperature of 95 °F. (35 °C.) From an out of ground effect hover at 4,000 feet, it could climb vertically at 184 feet per second (56.1 meters per second). At maximum continuous power its cruise speed in level flight was 141 knots, slightly less than required by the Army. With one engine inoperative, the helicopter’s ceiling was 4,750 feet (1,448 meters). There was a 100 foot difference in altitude with the left and right engines.
The 30 mm Hughes XM 230 Chain Gun automatic cannon was installed on the YAH-64 with 90 rounds. The gun’s rate of fire was adjustable and it was set to 535 rounds per minute on the prototype.
The AH-64A Apache was approved for full production in 1982. In 1984, the Hughes Helicopter Company was purchased by McDonnell Douglas and renamed McDonnell Douglas Helicopter Company. A facility to produce the Apache attack helicopters, as well as other civil and military helicopters, was opened in Mesa, Arizona. In 1997, MDHC was acquired by Boeing.
937 AH-64A attack helicopters were built between 1984 and 1997, when the improved AH-64D Apache Longbow entered production. Many AH-64As were remanufactured to the AH-64D configuration. More that 2,000 Apaches have been built. While most were for the U.S. Army, they fly for at least 14 other countries.
The Hughes YAH-64, 74-22248, is in the collection of the U.S. Army Aviation Museum, Ozark, Alabama.
AH-64D Apache Longbow 99-05097 over Iraq, 2005. This aircraft was originally AH-6A Apache 84-24287, before being remanufactured to the Longbow configuration at Mesa, Arizona. (TSGT Andy Dunaway/U.S. Army)
6 October 1983: First flight of the Bell Helicopter Company Model 406/OH-58D Kiowa reconnaissance helicopter. Developed from the earlier Model 206/OH-58A and OH-58C Kiowa, the D model features a four-blade composite main rotor, an upgraded engine and transmission, and improved avionics. The most visible features are the spherical mast-mounted sighting system above the main rotor and much larger engine/transmission cowling, or “dog house.”
