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)
Sikorsky MH-53M Pave Low IV, 68-8284, “Cowboy 26,” prepares for its final combat mission, Iraq, 27 September 2008. (A1C Jason Epley, U.S. Air Force)
27 September 2008: A United States Air Force Sikorsky MH-53M Pave Low IV special operations helicopter, serial number 68-8284, assigned to the 20th Expeditionary Special Operations Squadron, flew its final combat mission before being withdrawn from service and retired after 40 years and 12,066.6 flight hours.
“Cowboy 26” was flown by Major Philip Cooper, Captain Peter Hettinger, and Colonel Scott Howell, with Technical Sergeant Henry Woodie, Staff Sergeant Shawn Lewis, Senior Airman Eric Harp, and Airman 1st Class Joshua Lucas.
68-8284 was built by the Sikorsky Aircraft Corporation at Bloomfield, Connecticut, as one of 40 HH-53C Super Jolly Green Giants for Combat Search and Rescue (CSAR). It was delivered to the Air Force in August 1968. 68-8284 was assigned to the 40th Air Rescue and Recovery Squadron at Nakhon Phanom Royal Thai Air Force Base, 1971–1972. It operated as “Jolly Green 55.”
On 5 September 1971, with flight crew Major Jerry R. Thompson, Gary L. Gamble (CP), FE Raymond Duarte and PJs William D. Brinson and Michael D Vogele, it rescued the survivors of “Knife 33,” a 21st SOS CH-3E that went down in Laos. On 19 December 1971 (Capt Harold O. Jones (P), David G. Daus (CP), FE Jerrold T. Dearmans, with PJs Leon Fullwood and William D. Brinson, the crew of Falcon 74, a 13th TFS/432 TFW F-4D Phantom II which had gone down shot down 17 December by a SAM near Ban Poung Ban in northeastern Laos. Maj. William T. Stanley, Capt. Lester O’Brien were safely recovered.
A U.S. Air Force Sikorsky HH-53C Super Jolly Green Giant hovers to hoist a pararescueman with one downed pilot, while a second waits on the ground, 16 June 1967. The blade tip vortices are visible because of the high humidity. (This image has been reoriented and cropped from the original photograph.) (National Archives at College Park)
8284 was later assigned to the 67th Aerospace Rescue and Recovery Squadron (39th Aerospace Rescue and Recovery Wing) at RAF Woodbridge, Suffolk, England. 68-8284 has been constantly modernized and upgraded. It was initially converted to the MH-53J Pave Low III/Enhanced configuration by the Naval Air Rework Facility, NAS Pensacola, Florida, in the late 1980s. The helicopter was further modified to the MH-53M Pave Low IV configuration at the Naval Air Depot, MCAS Cherry Point, North Carolina.
The MH-53M Pave Low IV is designed for operations in darkness. (Staff Sergeant Aaron Allmon, U.S. Air Force) 080927-F-7823A-433
The MH-53M Pave Low IV is a variant of Sikorsky’s S-65 heavy-lift military transport helicopter series. The MH-53M is a single main rotor, single tail rotor, twin-engine helicopter. It has a crew of six: 2 pilots, 2 flight engineers and 2 gunners. The Pave Low IV is equipped with Terrain-Following Radar and Forward Looking Infrared (FLIR) for low-level operations in darkness and low visibility.
The MH-53M fuselage is 67 feet, 2.4 inches (20.483 meters) long, and the helicopter has a maximum length of 91 feet, 11.34 inches (28.025 meters) with rotors turning and the refueling boom extended. The height to the top of the main rotor pylon is 17 feet, 1.68 inches (5.224 meters). The maximum height (rotors turning) is 24 feet, 10.88 inches (7.592 meters).
Sikorsky HH-53C 3-view illustration with dimensions. (Sikorsky Historical Archives)
The fully-articulated 6-blade main rotor has a diameter of 72 feet, 2.7 inches (22.014 meters). The main rotor turns counter-clockwise at 185 r.p.m. (100% Nr), as seen from above. (The advancing blade is on the helicopter’s right.) The main rotor blades are built with titanium spars and have -16° of twist. The semi-articulated four-blade tail rotor has a diameter of 16 feet, 0 inches (4.877 meters) and is positioned on the left side of the tail pylon. It turns clockwise at 792 r.p.m., as seen from the helicopter’s left side. (The advancing blade is below the axis of rotation.) The gap between rotor arcs is just 4.437 inches (11.270 centimeters).
Empty, the MH-53M weighs 32,000 pounds (14,515 kilograms). Its maximum takeoff weight is 46,000 pounds (20,865 kilograms).
Its two General Electric T64-GE-100 axial-flow turboshaft engines have a Normal Continuous Power rating of 3,810 shaft horsepower at 85 °F. (30 °C.), Military Power rating of 4,090 shaft horsepower, and a Maximum Power rating of 4,330 shaft horsepower. The T64-GE-100 is 79 inches (2.007 meters) long, 20 inches (0.508 meters) in diameter and weighs 720 pounds (327 kilograms). Output (100% N2) is 13,600 r.p.m.
Two Sikorsky HH-53C Super Jolly Green Giants of the 39th Aerospace Rescue and Recovery Wing fly in formation over Goose Bay, Labrador, Canada, 11 June 1978. 68-8284 is the ship closest to the camera, painted gray. (TSgt. Robert C. Leach/U.S. Air Force)
The MH-53M has a maximum speed of 196 miles per hour (315 kilometers per hour) and a service ceiling of 16,000 feet (4877 meters). It carries two 450-gallon (1,703 liter) jettisonable fuel tanks under each sponson.
The MH-53M is armed with two M134 7.62mm miniguns and a GAU-18/A .50 caliber machine gun.
A Sikorsky MH-53J Pave Low III Enhanced from the 16th Special Operations Wing ready to refuel from a Lockheed MC-130E Combat Talon, 21 October 2001, classified location Operation Enduring Freedom. (TSGT Scott Reed, USAF) U.S. National Archives 6523525
At the time they were retired, the MH-53Ms were the fastest, heaviest, most powerful helicopters in the United States Air Force inventory.
After leaving Iraq, 68-8284 was transported by C-17 Globemaster III to England. It was loaned to the Royal Air Force Museum Cosford, where it is on display.
Sikorsky MH-53M Pave Low IV 68-8284 with another Pave Low IV on their final mission . 27 September 2008. (U.S. Air Force 080927-F-7823A-409)
Recommended:On a Steel Horse I Ride: A History of the MH-53 Pave Low Helicopters in War and Peace, by Darrel D. Whitcomb. Air University Press, Air Force Research Institute, Maxwell Air Force Base, Alabama, September 2012.
Vertol YCH-1B-BV 59-4983 hovers in ground effect. (Boeing Vertol)
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.
Boeing Vertol YCH-1B-BV 59-04983
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 prototypes were painted white and orange. This is the third YCH-1B, 59-4984. (Boeing Vertol)
The Chinook remains in production as the CH-47F Block I and MH-47G, and is used by the military services of several nations. Boeing is continuing development of the Block II variant.
