Daily Archives: January 10, 2017

10 January 1966

The prototype Bell Model 206A JetRanger, serial number 1, civil registration N8560F, hovering out of ground effect. (Bell Helicopter Company)
The prototype Bell Model 206A JetRanger, serial number 1, civil registration N8560F, hovering out of ground effect. (Bell Helicopter Company)

10 January 1966: The prototype Bell Model 206A JetRanger serial number 1, N8560F, made its first flight at at the Bell Helicopter Company plant at Hurst, Texas. This aircraft would be in production for almost 45 years. The final JetRanger to be built, Bell 206B-3 serial number 4690, was delivered in December 2010 and production came to an end.

The  Bell JetRanger is a 5-place, single-engine light civil helicopter based on the Bell Helicopter’s unsuccessful OH-4 entrant for the U.S. Army’s Light Observation Helicopter (LOH, or “loach”) contract. The industrial design firm of Charles Wilfred Butler “. . . was responsible for the complete redesign of the Bell OH4A prototype army helicopter (1961) into the Bell Jet Ranger (1965). He and his designers restyled the machine inside and out in the manner of automotive design, creating in the process one of the world’s most successful and beautiful helicopters.”Encyclopedia Britannica. It is flown by a single pilot in the right front seat. Dual flight controls can be installed for a second pilot.

The JetRanger is 38 feet, 9.5 inches (11.824 meters) long, overall. On standard skid landing gear the overall height is 9 feet, 4 inches (2.845 meters). The Bell 206A has an empty weight of approximately 1,700 pounds (771 kilograms), depending on installed equipment. The maximum gross weight is 3,200 pounds (1,451.5 kilograms). With an external load suspended from the cargo hook, the maximum gross weight is increased to 3,350 pounds (1,519.5 kilograms).

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 33 feet, 4.0 inches (10.160 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 10° negative twist. The airfoil is symmetrical.

The first Bell 206B JetRanger (Bell Helicopter Co.)
The first Bell 206A JetRanger, N8560F. (Bell Helicopter Co.)

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 at 2,550 r.p.m., 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 turboshaft engine is mounted above the roof of the fuselage, to the rear of the main transmission. Output shafts lead forward to the transmission and aft to the tail rotor 90° gear box. The transmission and rotor mast are mounted angled slightly forward and to the left. 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.

The 206A was powered by an Allison 250-C18 turboshaft engine (T63-A-700) which produced a maximum of 370 shaft horsepower at 100% N1, 51,120 r.pm. (The improved Model 206B JetRanger and 206B-2 JetRanger II used a 400 horsepower 250–C20 engine, and the Model 206B-3 JetRanger III had 250-C20B, -C20J or -C20R engines installed, which produced 420 shaft horsepower at 53,000 r.p.m.) Many 206As were upgraded to 206Bs and they are sometimes referred to as a “206A/B.” The Allison 250-C20B has a 6-stage axial-flow, 1-stage centrifugal-flow, compressor section, and a 4-stage axial-flow turbine (2-stage gas producer, and 2-stage power turbine). These were very light weight engines, ranging from just 141 to 173 pounds (64.0 to 78.5 kilograms).

The helicopter’s main transmission is limited to a maximum input of 317 shaft horsepower (100% Torque, 5-minute limit). The engine’s accessory gear unit reduces the output shaft speed to 6,016 r.p.m., which is further reduced by the transmission’s planetary gears, and the tail rotor 90° gear box.

The JetRanger has a maximum speed, Vne, of 150 miles per hour (241 kilometers per hour) up to 3,000 feet (914 meters). Its best rate of climb is at 60 miles per hour (97 kilometers per hour) and best glide speed is at 80 miles per hour (129 kilometers per hour). The service ceiling is 13,500 feet (4,145 meters) with the helicopter’s gross weight above 3,000 pounds (1,361 kilograms), and 20,000 feet (6,096 meters) when below 3,000 pounds. The helicopter has a maximum range of 430 miles (692 kilometers).

After being used as a factory demonstrator and development aircraft, N8560F was retired from flight status and used as a maintenance ground training device at Bell’s training school at Hurst.

Note: The Model 206A-1 was adopted by the U.S. Army as the OH-58A Kiowa. Though very similar in appearance to the Model 206A and 206B, the OH-58A differs significantly. Few of the parts are interchangeable between the types.

Three view drawing of the Bell Model 206A/B JetRanger with dimensions. (Bell Helicopter TEXTRON)
Three view drawing of the Bell Model 206A/B JetRanger with dimensions. (Bell Helicopter TEXTRON)

© 2017, Bryan R. Swopes

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10 January 1964

Boeing B-52H-170-BW 61-023
Boeing B-52H-170-BW Stratofortress 61-023. (U.S. Air Force)

10 January 1964: This Boeing B-52H Stratofortress, serial number 61-023, flown by Boeing test pilot Charles F. (“Chuck”) Fisher, was conducting structural testing in turbulence near East Spanish Peak, Colorado. The other crew members were pilots Richard V. Curry and Leo Coer, and navigator James Pittman. Dick Curry was flying the airplane and Chuck Fisher, the aircraft commander, was in the co-pilot’s position. Pittman was on the lower deck.

The bomber was carrying two North American Aviation GAM-77 Hound Dog cruise missiles on pylons under its wings.

The Boeing B-52 Stratofortress had been designed as a very high altitude penetration bomber, but changes in Soviet defensive systems led the Strategic Air Command to change to very low altitude flight as a means of evading radar. This was subjecting the airframes to unexpected stresses. “Ten-Twenty-Three” (its serial number was 61-023, shortened on the vertical fin to “1023”) had been returned to Boeing Wichita by the Air Force to be instrumented to investigate the effects of high-speed, low-altitude flight on the 245-ton bomber.

Flying at 14,300 feet (4,359 meters) and 345 knots (397 miles per hour, 639 kilometers per hour), indicated air speed, the airplane encountered severe clear air turbulence and lost the vertical stabilizer. Several B-52s had been lost under similar circumstances. (Another, a B-52D, was lost just three days later at Savage Mountain, Maryland.)

East Spanish Peak (left), 12,688 feet (3,867 meters) and West Spanish Peak, 13,626 feet (4,153 meters), Sangre de Cristo Mountains, Colorado. (Footwarrior)
East Spanish Peak (left), 12,688 feet (3,867 meters) and West Spanish Peak, 13,626 feet (4,153 meters), Sangre de Cristo Mountains, Colorado. (Footwarrior)
Charles F. Fisher. (Argenta Images)
Charles F. Fisher. (Argenta Images)

Chuck Fisher immediately took control of the B-52. He later reported, “As the encounter progressed, a very sharp-edged blow which was followed by many more. We developed an almost instantaneous rate of roll at fairly high rate. The roll was to the far left and the nose was swinging up and to the right at a rapid rate. During the second portion of the encounter, the airplane motions actually seemed to be negating my control inputs. I had the rudder to the firewall, the column in my lap, and full wheel, and I wasn’t having any luck righting the airplane. In the short period after the turbulence I gave the order to prepare to abandon the airplane because I didn’t think we were going to keep it together.”

A Boeing report on the incident, based on installed sensors and instrumentation aboard -023, said that the bomber had  “. . . flown through an area containing the combined effects of a (wind) rotor associated with a mountain wave and lateral shear due to airflow around a mountain peak. . . Gust initially built up from the right to a maximum of about 45 feet per second [13.7 meters per second] (TAS), then reversed to a maximum of 36 feet per second [11 meters per second] from the left, before swinging to a maximum of about 147 feet per second [44.8 meters per second] from the left followed by a return to 31 feet per second [9.5 meters per second].”

Fisher flew the bomber back to Wichita and was met by a F-100 Super Sabre chase plane. When the extent of the damage was seen, the B-52 was diverted due to the gusty winds in Kansas. Six hours after the damage occurred, Chuck Fisher safely landed the airplane at Eaker Air Force Base, Blythville, Arkansas. He said it was, “the finest airplane I’ve ever flown.”

Boeing B-52H-170-BW Stratofortress 61-023, "Ten-Twenty-Three", after losing the vertical fin, 10 January 1964. (Boeing)
Boeing B-52H-170-BW Stratofortress 61-023, “Ten-Twenty-Three”, after losing the vertical fin, 10 January 1964. (Boeing)

61-023 was repaired and returned to service. It remained active with the United States Air Force until it was placed in storage at Tinker Air Force Base, Oklahoma, 24 July 2008.

Charles F. Fisher and the Boeing test crew with B-52H Stratofortress 61-023. (Boeing)
Charles F. Fisher at left,  and the Boeing test crew with B-52H Stratofortress 61-023. (Boeing)

The B-52H is a sub-sonic, swept wing, long-range strategic bomber. It has a crew of five. The airplane is 159 feet, 4 inches (48.6 meters) long, with a wing span of 185 feet (56.4 meters). It is 40 feet, 8 inches (12.4 meters) high to the top of the vertical fin. Maximum Takeoff Weight (MTOW) is 488,000 pounds (221,353 kilograms).

There are eight Pratt & Whitney TF33-PW-3 turbofan engines mounted in two-engine pods suspended under the wings on four pylons. Each engine produces a maximum of 17,000 pounds of thrust (75.620 kilonewtons). The TF-33 is a two-spool axial-flow turbofan engine with 2 fan stages, 14-stage compressor stages (7 stage intermediate pressure, 7 stage high-pressure) and and 4-stage turbine (1 stage high-pressure, 3-stage low-pressure). The engine is 11 feet, 10 inches (3.607 meters) long, 4 feet, 5.0 inches (1.346 meters) in diameter and weighs 3,900 pounds (15,377 kilograms).

The B-52H can carry approximately 70,000 pounds (31,750 kilograms) of ordnance, including free-fall bombs, precision-guided bombs, thermonuclear bombs and cruise missiles, naval mines and anti-ship missiles.

The bomber’s cruise speed is 520 miles per hour (837 kilometers per hour) and its maximum speed is 650 miles per hour (1,046 kilometers per hour) at 23,800 feet (7,254 meters) at a combat weight of 306,350 pounds. Its service ceiling is 47,700 feet (14,539 meters) at the same combat weight. The unrefueled range is 8,000 miles (12,875 kilometers).

With inflight refueling, the Stratofortress’s range is limited only by the endurance of its five-man crew.

The B-52H is the only version still in service. 102 were built and as of 27 September 2016, 76 are still in service. Beginning in 2013, the Air Force began a fleet-wide technological upgrade for the B-52H, including a digital avionics and communications system, as well as an internal weapons bay upgrade. The bomber is expected to remain in service until 2040.

Boeing B-52H-170-BW Stratofortress 61-023 taxiing at Minot Air Force Base, North Dakota. (Senior Airman Cassandra Jones, U.S. Air Force)
Boeing B-52H-170-BW Stratofortress 61-023 taxiing at Minot Air Force Base, North Dakota. (Senior Airman Cassandra Jones, U.S. Air Force)

© 2016, Bryan R. Swopes

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10 January 1956

Lieutenant Barty R. Brooks, USAFR, standing on the wing of a North American Aviation F-86F Sabre, Korea, 1954. (U.S. Air Force)
Lieutenant Barty R. Brooks, USAFR, standing on the wing of a North American Aviation F-86F Sabre, Korea, 1954. (U.S. Air Force)

10 January 1956: First Lieutenant Barty Ray Brooks, United States Air Force Reserve, a pilot assigned to the 1708th Ferrying Wing, Detachment 12, at Kelly Air Force Base, Texas, along with two other pilots from the same unit, Captain Rusty Wilson and Lieutenant Crawford Shockley, picked up three brand new F-100C Super Sabre fighters at the North American Aviation Inc. assembly plant at Air Force Plant 42, Palmdale, California. It was to be a short flight, as these three jets were being taken to nearby George Air Force Base, Adelanto, California, only 42.5 miles (68.4 kilometers) to the east. Brooks was flying F-100C-20-NA, serial number 54-1907.

This North American Aviation F-100C-25-NA Super Sabre, serial number 54-2099, is similar to the fighter flown by Lieutenant Brooks, 10 January 1956. (U.S. Air Force)
This North American Aviation F-100C-25-NA Super Sabre, serial number 54-2099, is similar to the fighter flown by Lieutenant Brooks, 10 January 1956. (U.S. Air Force)
This photograph shows the lower section of the nose gear strut of an F-100 Super Sabre. The scissors ling is the hinged assembly. A red pin is visible at teh center hinge. Thi spin had been removed by ground handlers to tow the fighter, but had not been reinstalled before Lt. Brooks' flight.
This photograph shows the lower section of the nose gear strut of an F-100 Super Sabre. The scissors link is the hinged assembly. A red pin is visible at the center hinge. This pin had been removed by ground handlers to tow the fighter, but had not been secured with a safety pin when it was reinstalled before Lt. Brooks’ flight. (Michael Benolkin)

The brief flight was uneventful until the pilots lowered the landing gear to land at George AFB. One of the other pilots saw that the scissors link joining the upper and lower sections of the nose gear strut on Brooks’ Super Sabre was loose. Concerned that he would not be able to steer the fighter after touching down, Brooks diverted to Edward Air Force Base, 36 miles (57 kilometers) to the northwest, where a larger runway and more emergency equipment was available. Captain Wilson escorted Lieutenant Brooks to Edwards.

The F-100C Super Sabre had no flaps and required a high speed landing approach. Lieutenant Brooks had only 674 total flight hours as a pilot, and just 39 hours in the F-100. During his final approach to the runway he allowed the fighter to slow too much and the outer portion of the wings stalled and lost lift. This shifted the wings’ center of lift forward, which caused the airplane to pitch up, causing even more of the wing to stall. Lieutenant Brooks fought to regain control of the airplane, but he was unable to. At 4:27 p.m., Pacific Standard Time, the F-100 crashed on the runway and exploded. Barty Ray Brooks was killed.

Edwards Air Force Base is the center of flight testing for the U.S. Air Force. In preparation for a test later that afternoon, the base film crews had their equipment set up along the runway and captured the last seconds of Brook’s flight on film. This is the most widely seen crash footage, and is still in use in pilot training. It is named “The Sabre Dance.”

The article “The Deadly Sabre Dance” by Alan Cockrell is highly recommended:

http://www.historynet.com/deadly-sabre-dance.htm

© 2015, Bryan R. Swopes

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10 January 1954

The first production de Havilland DH.106 Comet 1, G-ALYP, in formation with the two prototypes, G-ALVG and G-ALZK. G-ALYP also broke up in flight, 10 January 1954. (Ed Coates Collection)
The first production de Havilland DH.106 Comet 1, G-ALYP, in formation with the two prototypes, G-ALVG and G-ALZK. (Ed Coates Collection)

10 January 1954: British Overseas Airways Corporation Flight 781 departed Ciampino Airport, Rome, Italy, at 0931 UTC, enroute to Heathrow Airport, London, England. The airliner was the first production de Havilland DH.106 Comet I, G-AYLP, serial number 06003. The flight crew were Captain Alan Gibson, First Officer William John Bury, Engineer Officer Frances Charles McDonald and Radio Officer Luke Patrick McMahon. There were two flight attendants, Frank L. Saunders and Jean Evelyn Clark, and 29 passengers. After departure began climbing toward its cruise altitude of 27,000 feet (8,230 meters).

At 0951 UTC, 20 minutes after takeoff, Captain Gibson was conversing by radio with another BOAC flight. It is presumed that Flight 781 had reached its cruise altitude. Captain Gibson was heard to say, “George How Jig from George Yoke Peter [the phonetic alphabet call signs for Argonaut G-ALHJ and Comet G-AYLP] did you get my—” and the transmission suddenly ended. Nothing more was heard from Flight 781 and it did not arrive at its destination.

Several fishermen had seen the airliner crash into the Mediterranean Sea near the island of Elba and recovered bodies of the victims, which were found to have suffered the effects of explosive decompression.

Wreckage of Comet G-AYLP was found on the sea floor, 12 February 1954, and it was apparent that the airliner had broken up in flight. Consideration was given to the possibility of a bomb having been placed aboard, or that an uncontained turbojet engine failure had penetrated the pressure cabin resulting in a structural failure of the fuselage through explosive decompression.

De Havilland Comet 1 G-AYLP (Crash-aerien)
De Havilland Comet 1 G-AYLP (www.crash-aerien.news)

After two prototypes, G-AYLP was the first production Comet. It was the fourth DH.106 to be lost in just over fourteen months. With the cause of Flight 781’s crash undetermined, B.O.A.C. grounded its remaining Comet airliners. De Havilland engineers recommended more than 60 modifications to improve perceived weaknesses in the Comet fleet.

Extensive testing by the Royal Aircraft Establishment determined that the Comet’s pressurized fuselage could be expected to fail from metal fatigue after 1,000 pressurization/depressurization cycles. G-AYLP had experienced 1,290 pressurization cycles during the 3,681 hours it had flown since its first flight, 9 January 1951.

The Royal Aircraft Establishment placed DH.106 Comet I G-AYLU in a water tank to conduct pressurization tests. (lessonslearned.faa.gov)
The Royal Aircraft Establishment placed DH.106 Comet I G-AYLU in a water tank to conduct pressurization tests. (lessonslearned.faa.gov)

Reconstruction of G-ALYP’s fuselage revealed that a fatigue crack had begun at a rivet hole of a square opening for the airplane’s automatic direction finder antenna. With the differential in pressure from inside and outside the passenger cabin, this crack had spread along the top of the fuselage through a passenger window and back to to the elevators at the tail. The fuselage structure then failed explosively and the airplane’s tail section came off. The wings then failed and fuel carried inside caught fire. The cockpit section tore away from the remaining fuselage section.

In reporting the Probable Cause of the destruction of G-AYLP, the committee wrote,

We have formed the opinion that the accident at Elba was caused by structural failure of the pressure cabin, brought about by fatigue. We reach this opinion for the following reasons:

(i) The low fatigue resistance of the cabin has been demonstrated by the test described in Part 3, and the result is interpretable as meaning that there was, at the age of the Elba aeroplane, a definite risk of fatigue failure occurring.

(ii) The cabin was the first part of the aeroplane to fail in the Elba accident.

(iii) The wreckage indicates that the failure in the cabin was the same basic type as that produced in the fatigue test.

(iv) This explanation seems to us to be consistent with all the circumstantial evidence.

(v) The only other defects found in the aeroplane were not concerned at Elba, as demonstrated by the wreckage. Report of the Public Inquiry into the causes and circumstances of the accident which occurred on the 10th January 1954, to the Comet aircraft G-AYLP.

Four months later, April 8 1954, a Comet 1 operated by South African Airways as Flight 201 from Rome to Cairo, G-ALYY, crashed near Naples, Italy with the deaths of all 21 persons aboard. The airplane had explosively broken up at an altitude of 35,000 feet (10,668 meters).

The de Havilland DH.106 Comet fleet was grounded and the Ministry of Transportation withdrew the type’s Certificate of Airworthiness. Production of the airliner at Hatfield came to a stop.

BOAC's DH.106 Comet I G-ALYW in long term storage at Heathrow, 12 September 1954. (RuthAS via Wikipedia)
BOAC’s DH.106 Comet I G-ALYW in long term storage at Heathrow, 12 September 1954. (RuthAS via Wikipedia)

De Havilland redesigned the Comet, and as the Comet 4 it had a successful career in airline operation. It eventually lost out to the faster, longer range Boeing 707 and Douglas DC-8. Production ceased in 1964 and B.O.A.C. retired its last Comet in 1965.

The Comet was again redesigned as the Hawker Siddeley Nimrod maritime reconnaissance aircraft.

© 2016, Bryan R. Swopes

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