James R. Gannet | This Day in Aviation

Boeing 707-121 N708PA, photographed during its second flight. (Boeing via Space.com) — Boeing 707-121 N708PA, photographed during its second flight on the afternoon of 20 December 1957. (Boeing)

Boeing 707-121 N708PA makes its first takeoff at 12:30 p.m., on a rainy afternoon, 20 December 1957. (Unattributed) — Boeing 707-121 N708PA makes its first takeoff at 12:30 p.m. on a rainy afternoon, 20 December 1957. (Boeing)

20 December 1957: The first production Boeing 707 jet-powered commercial airliner, N708PA, made its first flight at Renton, Washington. Alvin M. “Tex” Johnston, Boeing’s Chief of Flight Test, was in command, with co-pilot James R. Gannet and flight engineer Tom Layne. Takeoff was at 12:30 p.m., PST. Poor weather limited the first flight to just 7 minutes. The new airliner landed at Boeing Field. Later that day, a second flight was made, this time with a duration of 1 hour, 11 minutes.

N708PA (Serial Number 17586, Line Number 1) was a Model 707-121. The new airliner had been sold to Pan American World Airways, the launch customer, as part of an order for twenty 707s in October 1955.

Boeing test pilot Alvin M. "Tex" Johnston in the cockpit of of the 367–80. (LIFE) — Boeing’s Chief of Flight Test, Alvin M. “Tex” Johnston, in the cockpit of of the 367–80, “Dash Eighty,” 1954. (LIFE Magazine via Jet Pilot Overseas)

The Boeing Model 707 was developed from the earlier Model 367–80, the “Dash Eighty,” prototype for an air-refueling tanker which would become the KC-135A Stratotanker. The 707 was a four-engine jet transport with swept wings and tail surfaces. The leading edge of the wings were swept at a 35° angle.

N708PA was initially used for flight testing by Boeing. Once this was completed, it was prepared for commercial service and delivered to Pan American at San Francisco International Airport (SFO), 30 November 1958. Pan Am named the new airliner Clipper Constitution.

Boeing 707-121 708PA under maintenance at Renton, Washington. (Boeing) — Boeing 707-121 N708PA under maintenance at Renton, Washington. (Boeing)

In February 1965, the airliner was upgraded to 707-121B standards, which replaced the original turbojet engines with quieter, more efficient Pratt & Whitney JT3D-1 turbofan engines which produced 17,000 pounds of thrust. The wing inboard leading edges were modified to the design of the Model 720 and there was a longer horizontal tail plane.

Clipper Constitution flew for Pan Am for nearly seven years, until 17 September 1965 when it crashed into Chances Peak, a 3,002 foot (915 meters) volcano on the Caribbean island of Montserrat. The point impact was 242 feet (74 meters) below the summit. All aboard, a crew of 9 and 21 passengers, were killed.

Boeing 707-121 N708PA, with both Boeing and Pan American corporate markings. (Unattributed)

The Boeing Model 707-121 was a four-engine jet transport with swept wings and tail surfaces. The leading edge of the wings were swept at a 35° angle. The airliner had a flight crew of four: pilot, co-pilot, navigator and flight engineer.

The 707-121 was 145 feet, 1 inch (44.221 meters) long with a wing span of 130 feet, 10 inches (39.878 meters). The top of the vertical fin stood 42 feet, 5 inches (12.929 meters) high. The 707 pre-dated the ”wide-body” airliners, having a fuselage width of 12 feet, 4 inches (3.759 meters). The airliner’s empty weight is 122,533 pounds (55,580 kilograms). Maximum take off weight is 257,000 pounds (116,573 kilograms).

The first versions were powered by four Pratt & Whitney Turbo Wasp JT3C-6 turbojet engines, producing 11,200 pounds of thrust (49,820 kilonewtons), and 13,500 pounds (60.051 kilonewtons) with water injection. This engine was a civil variant of the military J57 series. It was a two-spool axial-flow turbojet engine with a 16-stage compressor and 2 stage turbine. The JT3C-6 was 11 feet, 6.6 inches (3.520 meters) long, 3 feet, 2.9 inches (0.988 meters) in diameter, and weighed 4,235 pounds (1,921 kilograms).

At MTOW, the 707 required 11,000 feet (3,352.8 meters) of runway to take off.

The 707-121 had a maximum speed of 540 knots (1,000 kilometers per hour). It’s range was 2,800 nautical miles (5,186 kilometers).

The Boeing 707 was in production from 1958 to 1979. 1,010 were built. Production of 707 airframes continued at Renton until the final one was completed in April 1991. As of 2011, 43 707s were still in service.

Boeing 707-121 N708PA retracts its landing gear after taking off at Seattle Tacoma Airport. (Unattributed) — Boeing 707-121 N708PA retracting its landing gear after takeoff at Seattle Tacoma Airport. (Unattributed)

Looking out across the right wing of the Boeing 367–80, inverted, at the city of Seattle, 6 August 1955. (Bill Whitehead/Boeing)

6 August 1955: Boeing’s Chief of Flight Test, Alvin M. “Tex” Johnston, barrel-rolled the Model 367-80, prototype of the KC-135 Stratotanker and 707, over Lake Washington.

Twice.

This photograph was taken by the flight test engineer, Bill Whitehead.

Boeing had risked $16,000,000 in a private venture to build the Dash 80 in order to demonstrate its capabilities to potential civilian and military customers, while rivals Douglas and Lockheed were marketing their own un-built jet airliners. Put into production as the U.S. Air Force KC-135 Stratotanker air refueling tanker and C-135 Stratolifter transport, a civil variant was also produced as the Boeing 707, the first successful jet airliner. Though they look very similar, the 707 is structurally different than the KC-135 and has a wider fuselage.

Boeing Model 367-80 (“Dash Eighty”) in flight. (Joe Parke/Wikipedia)

The prototype Boeing Model 367-80 was operated by a pilot, co-pilot and flight engineer. The airplane’s wing was mounted low on the fuselage and the engine nacelles were mounted on pylons under the wing, as they were on Boeing’s B-47 Stratojet and B-52 Stratofortress. The wings and tail surfaces were swept to 35°. The Dash 80 was 127 feet 10 inches (38.964 meters) long with a wingspan of 129 feet, 8 inches (39.522 meters) and overall height of 38 feet (11.582 meters). Its empty weight was 92,100 pounds (41,775.9 kilograms) and loaded weight was 190,000 pounds (86,182.6 kilograms).

In tanker configuration, the Boeing 367-80 refuels a Boeing B-52 Stratofortress. The chase plane is a Lockheed T-33A Shooting Star. (U.S. Air Force)

N70700 was powered by four Pratt & Whitney Turbo Wasp JT3C engines. This engine is a civil variant of the military J57 series. It is a two-spool, axial-flow turbojet engine with a 16-stage compressor and 2-stage turbine. The JT3C-6 (used in the first production 707s) was rated at 11,200 pounds of thrust (49.82 kilonewtons), and 13,500 pounds (60.05 kilonewtons) with water/methanol injection). The JT3C is 11 feet, 6.6 inches (3.520 meters) long, 3 feet, 2.9 inches (0.988 meters) in diameter, and weighs 4,235 pounds (1,921 kilograms).

These gave the 367-80 a cruise speed of 550 miles per hour (885 kilometers per hour) and a maximum speed of 0.84 Mach (582 miles per hour, 937 kilometers per hour) at 25,000 feet (7,620 meters). The service ceiling was 43,000 feet (13,106 meters). Its range was 3,530 miles (5,681 kilometers).

The Boeing 707 has a wider fuselage and is structurally different than teh KC-135. (Boeing)

Boeing continued to use the 367–80 for testing, finally retiring it 22 January 1970. At that time, its logbook showed 2,346 hours, 46 minutes of flight time (TTAF). It was flown to Davis-Monthan Air Force Base, Tucson, Arizona, and placed in storage. In 1990, Boeing returned it to flyable condition and flew it back it to Renton where a total restoration was completed. Many of those who had worked on the Dash 80, including Tex Johnston, were aboard.

The pioneering airplane was presented to the Smithsonian Institution and is on display at the National Air and Space Museum, Steven V. Udvar-Hazy Center. The Boeing 367-80 was designated an International Historic Mechanical Engineering Landmark by the American Society of Mechanical Engineers.

820 of the C-135 series and 1,010 Model 707 aircraft were built from 1957–1979.

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20 December 1957

6 August 1955