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DC-9 Description

The McDonnell Douglas DC-9 is a twin engine turbofan, short to medium range jetliner. It is capable of serving smaller communities with shorter runways and a minimum of ground equipment for short 20 to 30 minute turn around times.

Control surfaces for roll and pitch are operated by mechanical linkage from the cockpit control wheels to the respective control tabs which in turn deflect the ailerons and elevator. Hydraulic power augments the elevator down force when the aircraft is at high angles of attack to assure a nose down capability. The rudder is hydraulically powered but with manual reversion using a control tab similar to the ailerons and elevators. Hydraulic spoilers on top of the wings assist the ailerons for roll control and are also used as speed brakes in flight and as ground spoilers to reduce lift during landing roll. Hydraulically powered wing leading edge slats and trailing edge flaps shorten takeoff and landing distance.

Additionally, hydraulic power is used for the retractable tricycle landing gear, nose wheel steering, brakes, engine thrust reverse actuators and aft entry stairs.

Ice protection is provided using bleed air from the engines for wing leading edge and horizontal tail surface de-ice and engine anti-ice. This, along with full IFR flight instrumentation and radar give the McDonnell Douglas DC-9 “all weather capability”.

The aircraft is air-conditioned and pressurized for comfort up to 35,000 feet. A passenger forward entrance retractable stair is provided along with an onboard auxiliary power unit (APU) gas turbine engine for stand alone electrical power, air-conditioning and engine start on the ground as well as backup electrical power in-flight. This, along with capability to manually load baggage into the cargo compartments without any equipment, makes this aircraft ideal for smaller station operations and charters.

DC-9 Development

When you think of the Douglas DC-9 series of jetliners, a vision of the 1960s comes to mind as the airlines of the world rushed to replace the grand old propliners of the golden age of aviation in order to compete in the fast and sleek new jet age. But this vision actually started for Douglas Aircraft Company as far back as the post war year of 1947 when various studies were undertaken for a new short to medium range aircraft.

One of the first of these studies was the T1119 which was also known as the DC-9. This was not a jet, but rather a 28 passenger airliner powered by two 1600 horsepower piston engines built by either Wright or Pratt & Whitney and capable of flying 1500 to 2500 miles. This idea was tabled mainly because Martin and Convair had products that offered the same capabilities for 40 passengers instead of 28. At the same time, Douglas was concentrating on the longer range market with the development of the DC-8 and directed most of its energy towards that end. It wasn’t until 1956 that the company got serious with the shorter range market and presented Project 2000 to the airline community.

Model 2067 was also designated the DC-9 and looked very similar to the DC-8. It was a four engine turbojet with the same fuselage as the “Eight”, transporting up to 96 passengers over 2300 miles. Meanwhile, Boeing had come out with the more competitive 727 design offering better economy. With United and Eastern ordering a sizeable number of Boeing’s tri-jet, the second major DC-9 concept was dropped.

The next design for the “Nine” was the model 2086 to more effectively compete with the French Sud Aviation Caravelle, the British BAC 1-11 and Boeing’s 727. This Douglas model was very close to the final version of the DC-9. The airplane had a larger cabin and cargo area than the BAC 1-11, but smaller with less range than the 727 and Caravelle. A major advantage of this design was its maximum takeoff gross weight (MTOW). At 69,000 pounds, this was under the FAA regulations in force at the time requiring U.S. airliners with a MTOW over 80,000 pounds to have three crewmembers in the cockpit (pilot, copilot and flight engineer). The Caravelle and the Boeing “three-holer” were both over this limit and subsequently required three crewmembers up front.

The Douglas 2086 design would feature two turbofan jet engines mounted on the aft fuselage with a “t-tail” empennage. This design won over a concept with wing mounted engines, due to less overall drag, better engine out controllability and reduced approach speed by using a larger trailing edge flap system. The loss of a BAC 1-11 in a test accident attributed to a deep stall at a high angle of attack alerted the Douglas engineers to this potential problem and added larger tail surfaces to keep the rudder from being blanked out along with wing fences to delay the stall. Initial design featured the boarding door with the integral stairs just forward of the left wing root and a unique pull out luggage rack for passengers’ smaller items, located near the door. Later design changes moved the boarding door to its final location with an optional collapsible integral stair stowed in a compartment underneath the door. The external luggage rack was eventually removed from the design. The powerplant chosen was the Pratt & Whitney JT8D, which would become a very successful and reliable engine, not only for the DC-9, but also for the Boeing 727 and 737.

In April of 1963, Douglas Aircraft, taking a huge risk, made the decision to go ahead with the DC-9 program despite a lack of any firm orders for the airplane. Unique to this project would be a cost sharing program with suppliers and heavier use of sub-contracting for parts. In order to entice Trans-Canada Airlines (now Air Canada) to place an order, Douglas contracted with DeHavilland of Canada to make the wings and most of the tail assembly. List price for the DC-9-10 series would be $3.1 million.

Later in April, the first firm order came in for the new airliner with a request from Delta for 15 DC-9-11s with an option for 15 more aircraft. Along with this order, Delta was consulted heavily on the design for the new aircraft, including cockpit design and simplicity, durability, and accessibility for the various systems of the airplane.

As the project went into high gear, new orders came flooding in from Bonanza, Trans-Canada, KLM, Swissair, TWA, and Hawaiian. The DC-9 production initially used the DC-8 assembly line due to a drop in the larger jet’s orders. Production costs were saved by testing various aircraft systems on regular DC-8 test flights.

Ship Number One rolled out of the Long Beach, California facility in May of 1964, just ten months after startup, with the first flight on February 25, 1965. Eventually, five aircraft were used for flight testing with no major problems noted except a sharper stall entry which was rectified by installing fences and stall strips along the leading edge of the wing.

The DC-9 entered service in early December 1965 with Delta, while more orders came in from airlines such as Eastern, West Coast, Ozark, Continental, Saudi Arabia, Iberia, Standard (U.S. Supplemental carrier), Ansett, and Trans Australia. By the end of 1965, sales were so strong for the DC-9 that the “Nine” production was done in two bays of the assembly line while the “Eight” had one.

While the U.S. deliveries were under FAA restriction for number of cockpit crew based on weight, airlines outside the U.S. weren’t necessarily under that restriction. Douglas designed the DC-9 with thoughts of eventually stretching the fuselage for follow-on models. The FAA ultimately changed the crew requirement and based it on individual aircraft certification. This allowed the much heavier DC-9-30 series to be launched with a crew of two pilots and in April of 1965, Allegheny ordered four of the new stretched DC-9s with an option of four additional aircraft. The new 30 series was almost 15 feet longer than the -10 with seating from 94 up to 127 passengers and using the JT8D -7 and JT8D-9 powerplants rated at 14,000 and 14,500 pounds of thrust respectively. First flight occurred on August 1st, 1966 with a category II ILS low visibility approach system included in its certification on December 22nd of that year. As a side note, a category III autoland low visibility approach system with a pilot head up display (HUD) was tested on the -30 model in May of 1967. The “Dash 30” would prove to be Douglas Aircraft’s most popular series of DC-9 with 589 airplanes built between 1966 and 1982.

Competition was heating up as Boeing entered the small to medium market with the B-737. Deliveries commenced in late 1967 for what would become aviation’s most plentiful airliner. The advantage of this model was that the cabin cross section was virtually identical to the B-707 and B-727, which was roomier than the DC-9, offering six abreast seating. This aircraft would also see stretched versions with the -100 model holding up to 103 passengers and the -200 up to 115.

Meanwhile, Douglas was inundated with aircraft orders and started to show some growing pains as unfinished DC-8s and 9s began to pile up outside the Long Beach facility. James McDonnell and his aerospace company came courting to help Douglas through these difficult times. The result was a merger in April of 1967 to form McDonnell-Douglas. This new arrangement proved beneficial both financially and with streamlining the production process.

Airlines desired larger capacity and/or better performance in the short to medium market with McDonnell-Douglas responding with three additional models. Ten DC-9-20 series were ordered by SAS for their unique performance requirements for short field / high elevation destinations. This model was essentially a DC-9-10 with a -30 wing (including the leading edge slats) and the more powerful JT8D-11 engine rated at 11,000 pounds of thrust each engine. The Scandinavian airline also ordered the next larger DC-9 to be offered. Extending the length another six feet from the -30 fuselage, the DC-9-40 raised the capacity to 128 passengers using the JT8D-9 engine for power.

Next was the very popular DC-9-50 with a 14 foot stretch compared to the -30 series. This model entered service in 1975 for Swissair and featured more powerful -15 or -17 powerplants with strakes positioned on each side of the nose for added stability at low airspeed / high angle of attack situations.

Other variants of the DC-9 were produced such as the C-9 for the USAF in an aeromedivac role and the USN for various logistic missions. Freighter versions of the DC-9-10 series were ordered with a cargo door on the left forward side. Continental Airlines ordered 19 DC-9-15RC “Rapid Change” models for passenger by day, cargo by night flexibility.

With the delivery to the United States Navy of a C-9 version on October 28, 1982, the production line ended for the DC-9 with 976 aircraft delivered to operators all over the globe. Follow-on versions of this popular airplane continued as the Douglas Commercial Transport number Nine was stretched even further into the MD-80/90 and then, as McDonnell-Douglas merged into Boeing, a modernized version of the original DC-9-30 using new and powerful high bypass turbofan engines and new glass technology became the Boeing 717.

The DC-9 airliner fulfilled the needs for the small to medium transport market for many years with a large percentage of the aircraft still flying today. The DC-9; a tribute to the quality design and craftsmanship of Douglas Aircraft; building a tough, reliable and cost competitive airliner.

North Central DC-9

As the major airlines of the United States began to upgrade their fleets to jets, the nation’s local service carriers were also eyeing the potential of having jet aircraft enhance their route networks. North Central Airlines personnel looked at various potential airframes that were already in production or on the drawing board in the early 1960s. Among those were the BAC 1-11 from England, the Fokker F-28 from Holland and the Boeing 737 and Douglas DC-9 from the U.S. All of these were a good fit for the short to medium haul market which was North Central’s bread and butter, but the BAC 1-11 and F-28 were too small and the 737 was controversial because of the two verses three cockpit crew problem. This left the DC-9, which at the time of consideration, was initially going to be an 80 passenger airframe. However, there were indications that a stretched version would be forthcoming.

Finally, on July 7, 1965, just five months after Douglas Aircraft first flew Ship Number One, North Central ordered five DC-9s with an option of five more for a package deal with spare parts worth 20 million dollars. These aircraft were initially ordered as the 80 passenger DC-9-10 series, but by mid 1966, had been modified to the 100 passenger -30 series.

With the first two DC-9-31s due for delivery to North Central’s main base at Minneapolis/St. Paul in late summer 1967, President Hal Carr and his team submitted a plethora of route requests to the Civil Aeronautics Board (CAB) to take full advantage of the new DC-9’s capabilities. The CAB, having realized the new playing field and economics involved with the new jets being ordered by the local service carriers, proposed a new non-stop policy allowing these airlines to bypass intermediate stops between city pairs which each airline already served. North Central responded to this new policy by proposing new non-stops between such city pairs as Minneapolis/St. Paul (MSP) – Chicago O’Hare, MSP – Omaha, Milwaukee – Detroit and Chicago O’Hare – Detroit. Routes were also filed for cities not on the Northliner route map, such as Denver, New York, Baltimore, Boston, Toronto, Cincinnati, and Columbus.

The initial order of DC-9s set into motion many other programs besides new route authority. Mechanics and tech personnel started their training in 1965 and 1966 to learn the new DC-9 systems along with station personnel on how to handle the new aircraft. Initial pilot transition training took place at TWA until the airline could get its own cockpit procedures trainer and other training aids operational.

North Central was also running short of adequate hanger facilities for the new jet, so in September of 1965, plans for a new $10 million operations base/ hanger/general offices was announced for construction at the south side of the Minneapolis/St. Paul International Airport property. Then in June of 1966, the Detroit operation moved from Willow Run Airport to Metro Airport with a new hanger built to handle up to three DC-9s at once.

While the company was busy preparing for the arrival of the first DC-9s, another major project was set into motion. North Central’s large fleet of Convair 440 piston airliners would be converted to the Allison powered Convair 580 prop-jet by Pacific Airmotive Corporation (PAC) of Burbank, California. PAC would also be under contract to the airline to provide overhaul, service and repair of the DC-9 engines. With deliveries starting in early 1967 for the 580, North Central would have an all turbine powered fleet by the end of the decade.

Production proceeded on schedule for the company’s DC-9 fleet as the first aircraft entered the assembly line at Long Beach in early 1967. Rollout for ship 901 (N951N, MSN 47067) occurred in June of that year with the jet arriving from the McDonnell-Douglas plant to North Central’s home base at MSP on July 28, 1967. Another “Nine” (N952N, MSN 47073) would arrive in time to have two jets available to enter service for the September 1st schedule. These “Nines” displayed the “new look” color scheme of aqua, navy blue and gold which matched the converted Convair prop-jets. Interiors were also similar using alternating aqua and gold seats with beige walls and ceilings. The cabin crews’ uniforms would also match the company’s “new look” scheme.

North Central’s new DC-9s fit well into its rapidly expanding schedule, leading the company to exercise its options of five additional aircraft, bringing the fleet up to a total of ten jets by mid 1968. Additional orders of the DC-9-31 series would bring the total to 20 of the 100 seat airplanes. As passenger traffic continued to grow throughout NCA’s system, the company decided it needed the services of a new DC-9 model, the even longer DC-9-51 series. This version was very popular with North Central, which resulted in 18 of the 125 passenger airplanes delivered to “The Route of the Northliners” beginning in April of 1976 with ship 851 (N760NC, MSN 47708) and continuing until the merger with Southern Airways to form Republic Airlines in July of 1979. There were also 10 additional DC-9-51s ordered by North Central which were subsequently delivered to Republic after the merger took place.

These twin engine jetliners would help expand North Central’s route system dramatically, connecting the upper mid-west communities to new destinations in the eastern, southern and western United States. Passengers on Northliner flights could now count on very quick, reliable and frequent service along North Central’s system on the quiet, efficient, all-weather McDonnell-Douglas DC-9 Fanjet. This aircraft would prove so valuable that most of these DC-9s continued to provide excellent service to NCA’s follow on airlines, Republic and Northwest, well into the 21st century.

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