B-707 an icon of lasting design and technological innovation

Part 2 of 6 of this B-707 series

Rafiq Jan

It was a pioneer in offering highly sophisticated and state-of-the-art onboard navigation systems that modern plane makers scratch their heads in amazement at the accomplishments of B-707 design engineers. Boeing 707 donned the most Expensive but useful systems that a top of the line jet of its time could have had:

Omega Navigation system [ONS]

It was first global-range-radio-navigation-system of its kind that became operational in 1971. U.S developed and adapted it in collaboration with few partner nations. It was used until the advent of GPS navigation system in 1997, It was one major system that supported ships and airplanes to determine positions.

LORAN [long range navigation]

A hyperbolic navigation system developed in the United States during WW2. It is an expensive long-range navigational aid for ships and large airplanes for position determination in long-haul flights and cruises. It remained active until 80s.

Periscopic Sextant, the celestial navigational instrument.

Boeing 707 had a handy periscopic sextant which could be fitted in a cockpit roof opening. The navigator used it to track the plane’s position with reference to celestial stars in the night and by position of the sun in daylight flights. An ingenious instrument that gauged the sun as well as the stars of the little bear constellation by which the ancient Phoenicians used to steer across the seas almost 6000 BC.

A formidable flight engineer’s station cluttered with gauges and toggle switches that had all the system controls and indications. It was in addition to the flight instruments and flight controls located upfront for pilots’ use.

It was a leader in starting the remote-reading compass system, gyroscopic operated and controlled directional, lateral, and vertical guidance systems that its followers also copied. Those techniques, with continuous upgrades and innovations, are still adopted and guaranteed for the decades to come.

Inertial navigation system [INS]

The INS was a self-contained, (without external guidance) system primarily designed and used for Rockets, tactical missile systems, submarines. It was a highly complicated and expensive system using computers and electronic displays.

Rock n Roll, the Dutch Roll.

A function of swept-back wings.

Since this was first high-speed jetliner designed with 35 degree swept-back wings, it had serious issues encountering Dutch roll. Boeing paid high price of its brand-new unit on a test flight while fighting the deadly Dutch roll that ended in plane crash. Yaw damper system was introduced as series and parallel yaw dampers. This too was an innovation of Boeing engineers that became an essential part of the flight control system on all the next generation of planes till today. A concept that became an essential feature of Airbus design as well.

Ventral Fin for lateral stability

Some European customers were delivered the modified version of B707s with specially fitted Ventral Fin below the vertical tail, to enhance the lateral stability during take-off and improve the yaw stability due to a short vertical stabilizer height.  It was their local authority’s requirement and was eliminated with the increase of vertical stabilizers height in later production models.

Engine options; different strokes for different folks

JT-4A turbojet engines were used on earlier B707s and Douglas DC-8 versions before the arrival of JT-3D bypass Turbofan engines.

JT-3C engines were used on some earlier 707s and DC-8s before arrival of JT-3D turbofan engines.

Rolls-Royce RB.80 Conway, was used on Boeing 707-420 and Douglas DC-8. It had 18000 Lbs thrust ratings, higher than other of its counterparts. It was the first low bypass Turbofan engine ever fitted on commercial airliner.

Innovative JT-3D features

JT-3D turbofan engine, the most used on B707s, had a unique feature incorporated to its inlet area. Secondary air inlet doors placed around the Fan Casing enhanced the volume of air for extra thrust at Take-off thrust more. They were mechanically operated, spring-held blocker doors that would modulate by suction principle.

Boeing 707 production line (1956-1978)

The official production of B707s started in 1956 and the last plane rolled out in 1978. The First 707s were designated as 707-120. Intercontinental versions were called 707-320.

 Despite its already dominant rivals, B-707 soon conquered the aviation world by an incredible combination of technology, capability, the economy and flying prowess. It soon outdistanced all the contemporary jetliner in the market.

19 different variant models were built that were sold to 63 different airlines.

B-707 became the most useful jetliner of its time and the first ever jetliner that was produced in large number. It immediately started impressing the airlines and gathered huge orders. It was the first in the history of plane makers to quickly start returning profit to its producer.

The First long-range, narrow body, jetliner produced and successfully launched by U.S plane manufacturer Boeing Airplanes Company.

Last two digits of B707 were designating the operator. A unique feature incorporated for the first and probably the last time to mark its entry like a true queen of skies.

1010 Numbers built and sold to world’s airlines.

The last 707 operated as passenger version belonged to Saha Airline of Iran, until 2013.

It will not be an overstatement to brag about B-707, a beautiful flying machine whose stunning design features were built to last the centuries. The design of its shape, avionics systems, the flight control systems, and lastly the integration of them all in one piece of equipment was indeed a timeless innovation to endure the future.

A Throwback into 60s catchy adverts.

“The 707 jetliners, with fully type certificated version, did its first flight on December 20, 1957 with her proud owner Pan American world airways. It was an inaugural flight for Pan American’s jetliner, but for Boeing company this was an auspicious moment that kept its manufacturer soaring higher and higher in the world’s aviation skies. This was first revenue flight of Boeing 707 but for her manufacturer this was an unending flight of success.”

End of part 2…….

The author Rafiq Jan is Aircraft engineer, an experienced Aviation analyst, planes enthusiast current affairs blogger and a  freelance writer.

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