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Airline Workhorse: The Boeing 727 Tri-Jet


By: Wayne Brown

De Havilland introduced the world to the concept of jet-powered aircraft in 1952. The Boeing Company joined in shortly thereafter and introduced jet air service to the commercial airlines and the world with the Boeing 707 aircraft. It was a new day in air travel, especially for those who flew coast to coast or international. The new 707 jet was fast and comfortable with engines capable of powering the aircraft to altitudes well above most weather systems and speed them to their destinations. While the 707 fulfilled its role as a coast to coast and international jet quite well, there was much left to do before the vast cross-section of America and the world would experience the jet-age. Again, the Boeing Company would fill that void with an aircraft which revolutionized the airline industry and its approach to transportation. That step was taken when Boeing introduced the Boeing 727 model aircraft to the world.

The Boeing 707 4-engine commercial jet

The Boeing 707 4-engine commercial jet

The Boeing 727 was designed as a domestic workhorse with the capabilities to provide service into secondary level airports with shorter runways. It was a narrow body design by today’s standards although not seen in that light then. The aircraft employed three engines all mounted in or on the tail section of the fuselage. The 727 took some of its cues from the design of the 707 employing some similarities in the fuselage and the cockpit design. The aircraft, in the various models that evolved, could carry 149 to 189 passengers on either short or medium legs. The airlines employed it on both feeder routes and main routes depending on the passenger demand.

The original version launched in February of 1963 was the 727-100 model capable of carrying 149 passengers up to 2400 miles. In actuality, the only limiting factor of the 727 in terms of domestic use in the USA was seating capacity. Otherwise, the aircraft was capable of coast to coast route ranges. Along with the three engine tail-mount configuration, the 727 also had three other eye-catching features which set it apart from the other jet aircraft of the times. One was the redesigned tail configuration in which the horizontal stabilizer and vertical stabilizers were incorporated in the “t-shape” allowing the lower portion of the fuselage at the tail to be used for incorporation of the tri-engine cluster. This exceptional and futuristic design changed the rules for how a jet aircraft should look and open the door for new ideas.

A second feature sported by the 727 was an “air stair” system mounted in the tail of the aircraft under the center engine. The air stair allowed access from the ground to the rear of the passenger compartment allowing the aircraft to load and unload without the use of a jet-way or ramp provided stairs. The stairs could even be extended in flight, a feature which would later cause some unexpected problems. The 727 also employed an onboard auxiliary power unit or APU incorporated in the main landing gear bay in the belly of the fuselage. This unit allowed the aircraft to be self-supported in terms of "on-ground power requirements" at smaller airports with limited capabilities.

(Note the design of the control surfaces on the 727 tail are reversed into a “T” configuration allows room on the aircraft fuselage at the rear for the mounting of the three engine cluster.

(Note the design of the control surfaces on the 727 tail are reversed into a “T” configuration allows room on the aircraft fuselage at the rear for the mounting of the three engine cluster.

(Note the United 727 aircraft with “air stair” extended for boarding of passengers)

(Note the United 727 aircraft with “air stair” extended for boarding of passengers)

The final eye catcher was the wing design. Since there were no engines mounted on the wing, engineers were able to design a sleek, swept, multi-function, lifting surface with variable geometry capability affording the aircraft a great range of operation in terms of speed and runway length. The 727 employed both a traditional flap system at the rear of the wing and an extendable slat system on the leading edge of each wing. This design allowed the wing surface to expand to the front and rear of the main wing giving the aircraft the ability to generate greater amounts of lift at lower speeds. This design facilitated the 727’s ability to get in and out of shorter airfields than traditional jet aircraft of the day such as the Boeing 707 and the McDonnell Douglas DC-8.

(Note:  A Boeing 727 with full wing flaps extended)

(Note: A Boeing 727 with full wing flaps extended)

(Note: a FedEx Boeing 727 on approach with leading edge slats and wing flaps extended)

(Note: a FedEx Boeing 727 on approach with leading edge slats and wing flaps extended)

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Eastern Airlines received the first orders for the aircraft. Eastern ordered the 727-100 model and put them into service in February of 1964. Boeing went to work to expand the capability of the airframe and came up with the 727-200 model which was a stretched version of the 100-series fuselage offering more passenger and cargo space inside the aircraft. The first orders for the 727-200 entered service with Northwest Orient Air Lines in July of 1967. The aircraft was an immediate hit with both the airlines and the pilots who flew it. The Boeing 727 quickly took over as the workhorse of domestic aviation in the USA and began to break into the domestic markets of other nations as well. Boeing has a winner on its hands.

(Note: A Boeing 727-100 dressed out in Eastern Airlines livery.  Eastern referred to the Boeing 727 as “The Whisper-jet”.)

(Note: A Boeing 727-100 dressed out in Eastern Airlines livery. Eastern referred to the Boeing 727 as “The Whisper-jet”.)

Boeing had designed the 727 to meet the needs of the major airlines of the USA. At the time, the majority of passenger service was provided by three major airlines, American, Eastern, and United Air Lines. They all agreed at the time that there was a need for a smaller aircraft with more capability to serve primary and secondary passenger markets. The aircraft desired had to have high altitude-capability and some measurable fuel efficiency over the four engine jets of the day. The aircraft also need to be relatively independent in its ability to facilitate passengers at smaller airports. A smaller two engine jet might have filled the bill handily but Eastern Airlines held out for a third engine reasoning that two engine aircraft did not fit their overwater needs for service in and out of the Caribbean locations. The FAA restricted two engine jets from flying more than one hour travel time off the coast.

The early design evolved in terms of both the design approach and the engine specifications prior to the first deliveries. For a short time, Boeing considered a joint venture on the development with De Havilland Aircraft, a company also in the process of developing a tri-engine jet. Both companies saw the potential to move the process along at a much faster pace if they combined their efforts. De Havilland felt that it had the better design and wanted Boeing to use in as a licensee for the U.S. market. In weighing the design of the De Havilland, Boeing discovered that the aircraft did not properly address the specifications of the U.S. domestic market. Boeing quickly backed off and decided to go it alone knowing that it would take longer to develop the 727 aircraft while realizing the final design would better address the needs.

Along with abandoning the joint venture, Boeing also turned away from the original plan to incorporate the Roll-Royce RB-163 Spey jet engine as the standard engine for the model. Pratt & Whitney had come up with an engine design with similar performance specifications to the Rolls Royce. It was also a more affordable engine in terms of upfront costs and replacement parts. The decision turned when Eddie Rickenbacker, then Chairman of the Board at Eastern Airlines, indicated that Eastern favored the Pratt & Whitney engine. In selecting the Pratt & Whitney, Boeing add additional doubts to their timeline for the 727 in that Pratt & Whitney was behind Rolls Royce in the progress of their engine development. If Pratt and Whitney could not evolve their design, Boeing would have an airframe without engines. It was a risk and a decision which had no right answer but at least the selection of the Pratt & Whitney design curried Boeing favor with one of the three major U.S. domestic carriers.

By design, all three engines mounted at the tail of the Boeing 727 were fitted into the same plane horizontally. This put the middle engine of the cluster inside the fuselage which robbed it of its ability to intake air. The engine on the left and right side of the tail were mounted in a convenient external configuration allowing them to gain their normal air flow through the engine. The middle engine would have to receive its air through an S-shaped duct system which attached at the front of the middle engine then curved upward and turned again to the horizontal plane extending forward to join the intake inlet at front of the vertical stabilizer root. While the design looked smooth to the eye, it created problems. The air traveling into the center engine was actually traveling a greater distance for the same size intake before it hit the compressor stage of the jet. The S-shape of the duct system also allowed the air to spin and created a tendency to reverse flow in the duct starving the engine of the necessary air for compression. Boeing had not uncovered this design flow until they hit the flight test phase for the 100 model and found that the center engine began to surge on the first attempted takeoff indicating the center engine was not getting an even flow of air through it. The situation was troublesome in that it was rather late in the development to be considering a major redesign of the tail-section of the aircraft. Luckily, Boeing engineers found that they could install vortex generators (a system of vanes) into the center engine duct which would send the incoming air into a vortices flow and more efficiently feed the engine. The fix worked and the flight test phase continued.

(Note: Rear view of the Boeing 727 engine mounting configuration on and in the tail of the fuselage. The displaced inlet duct opening for be center engine can be seen at the front base of the vertical stabilizer.)

(Note: Rear view of the Boeing 727 engine mounting configuration on and in the tail of the fuselage. The displaced inlet duct opening for be center engine can be seen at the front base of the vertical stabilizer.)

Boeing stayed true to the basic model designs of the 100 and 200 series aircraft creating sub-modifications of each one to fit the needs of the particular customer. Sales of the two variants continued to grow throughout the 1960’s only the expand even more in the decade of the ‘70’s as more commercial airlines throughout the world discovered the capabilities and the reliability of the 727 workhorse aircraft. Boeing continued production of the 727 models into 1984 prior to shutting down the lines. Over the course of production the two models had shown up in both passenger and freighter (cargo) variants. There was even a quick change model which allowed the customer to switch between passenger service and cargo in 30 minutes. Even some military applications evolved for the variants with various countries around the world. Airline users included: American, TWA, Northwest Orient, United, Delta, Pan Am, Continental, Air Alaska, Piedmont, Lufthansa, and many, many others around the globe. The Boeing 727 became the best-selling airliner of all times surpassing 1,000 units sold by January of 1972. By early 1983, Boeing had logged a total of 1831 aircraft ordered by a total of 101 customers. The total build prior to shutting down the line would be 1832 units which included the one 727 that Boeing held on to and did not sell. The 727 also earned one additional mark not achieved by any other commercial airliner. By 1977, it had carried over one billion passengers world-wide as it continued to log successes in its workhorse status.

Overtime, the aircraft receive many improvements in performance and payload carrying capability. Hush kits were added to bring the engines into compliance with environment noise-pollution regulations. Gross weight capabilities grew from a maximum of 170,000 lbs. to achieve a high of 210,000 lbs. gross takeoff weight in later model variants. Engine thrust increased from 15,000 lbs. in early models to 17,400 lbs. in later production configurations. Interiors were redesigned to provide better creature comforts and more storage space and more technology was added in the cockpit as well.

Though the Boeing 727 was a capable and reliable aircraft, it could not avoid the potential for accidents and crashes. The statistically large sampling of its use throughout the airlines of the world raised the odds that crashes were inevitable if for no other reason but human error. Over its four plus decades of service, the 727 had its share of tragedy but still managed to turn in a stellar record of safety and reliability in the overall picture.

(Note:  A depiction comparing the two base variant models (-100 and -200) in the Boeing 727 aircraft.  The 200 model had the fuselage extended by 20 feet in length.)

(Note: A depiction comparing the two base variant models (-100 and -200) in the Boeing 727 aircraft. The 200 model had the fuselage extended by 20 feet in length.)

From August of 1965 until 2010, the Boeing 727 has been involved in incidents which resulted in a total of 3,783 fatalities. The incidents included crashes, mid-air collisions, ground collisions, shoot-downs, bombings, and hijacking-related situations. The 727 was a desired target of hijackers with the aircraft logging 178 hijacking incidents by 2010. Over the course of its service life, the Boeing 727 was involved in four mid-air collisions, one ground collision, three bomb-related incidents, one shot down, and a myriad of hijackings in which people other than those assaulting the aircraft died. As of 2010, the number of total fatalities had risen to 3,783 souls with 112 airframes destroyed. While the deaths of over 3700 people is not to be taken lightly, keep in mind that more than one billion passengers had traveled on the Boeing 727 by the end of its service life with the commercial airlines in the USA.

Some of the incidents noted above are unique and of interest while there are also other incidents which did not involve fatalities that are of note for this aircraft. Some of them are so unique, they will likely not occur again at any time soon. A few have been detailed below for the reader to experience.

On July 19, 1967, Piedmont Airlines Flight 22, a Boeing 727, departed Asheville Airport near Hendersonville, NC and began a normal climb out to altitude. Eight miles from the airport on the climbing departure course, the aircraft inadvertently crossed flight paths with a twin-engine Cessna 310 general aviation aircraft. The mid-air collision killed all five crewmembers of Flight 22 and all 74 passengers in addition to the three occupants of the Cessna aircraft.

All Nippon Airways Flight 58 collided with a US Air Force F-86F jet-fighter aircraft over northern Honshu, Japan. All seven crewmembers and the 155 passengers aboard were killed. The pilot flying the F-86 was able to successfully eject and survived the mid-air collision with the Boeing 727-200 on 30 July 1971.

On February 21, 1973, a 727-200 model operated by Libyan Arab Airlines as Flight 114 was shot-down over the Israeli-occupied Sinai Desert. As a result of a navigation error, the aircraft had strayed into the forbidden airspace. The aircraft was shot down by Israeli fighter-jets killing eight of the nine crewmembers and 100 of the 104 passengers on board the airplane.

An Air Vietnam 727-100 was hijacked near Phan Rang, South Vietnam on 15 September 1974. The aircraft eventually crashed after being hijacked killing all eight crewmembers and all 62 passengers on board the aircraft.

An Eastern Airlines 727-200 departed from New Orleans International Airport on June 24, 1975, heading to New York’s JFK Airport. On approach to JFK, the aircraft encountered severe wind shear conditions associated with thunderstorms in the area at low altitude and the pilots lost control. Six of the eight crewmembers assigned to the flight died in the crash along with 107 of the 116 passengers aboard the aircraft. This may have been the first of only two incidents in which wind shear was cited as the cause for the crash of a 727 aircraft.

A Pacific Southwest Airlines (PSA) 727-200 operating as Flight 182 was descending toward the approach phase of the flight into San Diego International Airport (Lindbergh Field). Ahead of the aircraft a Cessna 172 single-engine general aviation aircraft was climbing out from the airport. Seeing that the flight paths would conflict, the controllers instructed the pilots of Flight 182 to maintain visual separation, a task which the pilots failed to carry out. The two aircraft collided in flight causing the Cessna to explode. The 727 with a severely damaged right wing went into a spiraling dive to the ground. Both occupants of the Cessna were killed as were all seven crewmembers and all 128 passengers aboard the 727. In addition, seven others were killed on the ground and 20 houses were either damaged or destroyed.

On November 15, 1979, an American Airlines 727 operating as Flight 444 enroute from Chicago to Washington D.C. became a victim of the famed “Unabomber” later found to be Theodore Kaczynski. Kaczynski had shipped a package aboard the flight which triggered in the air but failed to explode. The bomb did induce a great amount of smoke into the aircraft causing twelve passengers to be overcome by smoke inhalation. The aircraft survived and landed safely at Dulles Airport in Washington D.C. with six crewmembers and 72 passengers. All aboard the aircraft survived.

Hijacking was popular sport in the latter days of the 727 life cycle. On 14 October 1980 a THY 727 was hijacked in flight enroute from Munich, West Germany to Ankara, Turkey. The aircraft stopped in Diyarbakir, Turkey to refuel and the hijacker was subsequently taken into custody. One of the passengers was killed during the hijacking operation.

July 9th, 1982 was a stormy day about the New Orleans International Airport. A Pan Am 727-200 operating as Flight 759, departed the airport in stormy conditions heading for its destination in Las Vegas, NV. Shortly after takeoff, the aircraft encountered wind shear at a relatively low altitude and crashed killing all seven crewmembers and all 138 passengers on board. The aircraft crashed into a populated area near the airport and killed an additional eight souls on the ground.

An Iberia Air 727-200 operating as Flight 350 began its take-off roll under foggy weather conditions on 7 December 1983 at Madrid, Spain. An Aviaco Air DC-9 aircraft had inadvertently taxied on to the active runway without clearance and collide with the 727. One of nine crewmembers was killed in the collision along with 50 of the 84 passengers on board. All 42 on board the DC-9 aircraft perished in the collision.