Among the world’s first short-range jet airliners, the Douglas DC-9 became a massive hit for the American aviation industry, even giving the mighty Boeing 737 a run for its money.
The origins of the DC-9 go back to the mid-1950’s, where, during the development of the company’s pioneering jet airliner, the DC-8, Douglas considered the creation of a short-range jet airliner to compliment it. Initial considerations were for a scaled-down DC-8, consisting of a four-engine configuration, but there was very little interest for such a project and it was ultimately scrapped. In 1960, Douglas signed a two-year contract with Sud Aviation for technical cooperation. Douglas would market and support the Sud Aviation Caravelle and produce a licensed version if airlines ordered large numbers.
None were ordered and Douglas returned to its design studies after the cooperation deal expired.
However, Douglas wasn’t one for quitting, and by 1962 the company was fully invested in studies for their new craft. The initial design consisted of a 63 seats and a gross weight of 69,000lb. The order was given to produce what was now dubbed the DC-9 in April 1963, and unlike their rivals, Boeing, who created the 727 using many shared parts from the larger 707, Douglas’ aircraft would share nothing in common with the larger DC-8, being instead completely its own aircraft.
The design comprised of two rear-mounted Pratt & Whitney JT8D turbofan engines, relatively small but highly efficient wings, and a T-tail. To comply with FAA regulations of the day, the DC-9’s takeoff weight was limited to 80,000lb for a two-person flight crew. The cabin could be configured for between 80 and 135 seats, and could be fitted with rows of 5 seats in Economy Class.
The main goal of the DC-9 however was its ability to land at airports of limited infrastructure and runway length. While this was exactly the same purpose as the 727, the DC-9 hoped to increase frequencies and reduce turnaround times by way of having fitted retractable stairs, including one in the tail. This meant the rigmarole of conjuring up a set of airstairs could be avoided, giving the aircraft an edge over the 727.
The tail-mounted engine design facilitated a clean wing without engine pods, which had numerous advantages. For example, flaps could be longer, unimpeded by pods on the leading edge and engine blast concerns on the trailing edge. This simplified design improved airflow at low speeds and enabled lower takeoff and approach speeds, thus lowering field length requirements and keeping wing structure light. The second advantage of the tail-mounted engines was the reduction in foreign object damage from ingested debris from runways and aprons. With this position, the engines could ingest ice streaming off the wing roots. Third, the absence of engines in underslung pods allowed a reduction in ground clearance, making the aircraft more accessible to baggage handlers and passengers.
However, one issue that caused trouble with aircraft of this particular engine configuration was deep stalling, which came to light following the crash of the BAC One-Eleven prototype in 1963. Deep Stalling (also known as Super Stalling) is a condition where the wake of the wing impinges on the tail surface and renders it almost ineffective. The wing is fully stalled, so the airflow on its upper surface separates right after the leading edge, which produces a wide wake of decelerated, turbulent air. The DC-9 overcame these issues by way of fitting vortilons, small surfaces beneath the wing’s leading edge used to control airflow and increase low speed lift.
The DC-9 made its first flight on February 25th, 1965, followed by four other test aircraft. The initial Series 10 achieved its airworthiness certification on November 23rd, 1965, and entered service with launch customer Delta Air Lines on December 8th the same year. The DC-9 was always intended to be available in multiple versions to suit customer requirements, The first stretched version, the Series 30, with a longer fuselage and extended wing tips, flew on August 1st, 1966, entering service with Eastern Air Lines in 1967. The initial Series 10 would be followed by the improved -20, -30, and -40 variants. The final DC-9 series was the -50, which first flew in 1974.
The DC-9 was a success in its own right, with 976 examples built when production ended in 1982. During the height of its popularity, the aircraft was on the books of a majority of the world’s major airlines, including Delta Air Lines, Scandinavian Airlines, British Midland, Eastern Air Lines, Spirit Airlines, Trans Australia Airlines and, most notably, Northwest Airlines, who operated the largest fleet of DC-9’s at 172 units.
Unlike other Douglas Aircraft, most notably the DC-10, the DC-9 garnered a reputation for sturdy reliability and efficiency, a trait which kept many DC-9’s in front-line operation well into the 2000’s. The success of the design paved the way for the later series of McDonnell Douglas MD-80’s, which were built until 2006 (though under the guise of the Boeing 717), with over 2,400 examples produced. With this huge number of aircraft built, it ranks third for most produced commercial airliner behind the second-place Airbus A320 family with over 6,000 produced, and the first-place Boeing 737 with over 8,000.
However, in spite of the DC-9’s reliable nature, it has been marred in tragedy more than once, in fact, the number of losses it has incurred is probably among the highest for any front-line commercial jet airliner. As of 2010, the DC-9 has been involved in 117 aviation occurrences, including 101 hull-loss accidents, with 2,135 fatalities combined.
The first loss of a DC-9 was on October 1st, 1966, when West Coast Airlines Flight 956 crashed into the ground approximately 5.5 miles south of Wemme, Oregon, United States. Thirteen passengers and five crew members were aboard, and there were no survivors.
The aircraft has also been involved in four mid-air collisions; the two most notable examples being Inex-Adria Aviopromet Flight 550 on September 10th, 1976, which collided with a British Airways Trident over the Croatian town of Vrbovec, killing all 176 people aboard both aircraft and another person on the ground, and Aeroméxico Flight 498 on August 31st, 1986, which collided in mid-air with a Piper Cherokee over the city of Cerritos, California, then crashed into the city, killing all 64 aboard the aircraft, 15 people on the ground, and all 3 in the small plane.
The DC-9 also held the unfortunate title of Worst Accident in Aviation history on March 16th, 1969, when Viasa Flight 742 crashed into the La Trinidad neighborhood of Maracaibo during a failed take-off. All 84 people on board the aircraft, as well as 71 people on the ground, were killed, a total death toll of 155.
The latest accident at the time of writing (01/2017) occurred on July 6th, 2008, when USA Jet Airlines Flight 199 crashed on approach to Saltillo, Mexico, after a flight from Shreveport, Louisiana. The captain died and first officer was seriously injured.
Today, a total of 77 examples in all varieties continue to operate in commercial service, these including USA Jet Airlines (10), Everts Air Cargo (4), Aeronaves TSM (6), LASER Airlines (3), Fly SAX (2), African Express Airways (2), Fly540 (2) and other operators with fewer aircraft. The sheer reliability and flexibility of the DC-9 however meant that most of the type operating for major carriers weren’t retired until recently. The largest operator, Northwest Airlines, had it’s fleet acquired by Delta Air Lines following it’s acquisition in 2008, but the final retirement of the DC-9 for Delta didn’t take place until January 6th, 2014, 32 years after the last DC-9 left the production line.
Additionally, the DC-9 has the distinction of being the only airline transport class jet certified to date by the FAA for skydiving operations as of 2017. An ex-SAS example (built way back in 1969) operated by Perris Valley Skydiving from Perris Valley, California, has had its tail steps removed to allow skydivers to jump straight out the rear of the plane. The aircraft has apparently proved itself very popular among enthusiasts, and earns itself quite a sizeable income from a global audience.
But I feel such a lengthy term of service is a testament to the incredibly strong nature of these fantastic little planes. There was no real intention for the DC-9 to conquer the world, but it did, and it caught Douglas sleeping. However, such a simplistic design meant it was easy to expand the technology into its many derivatives, a majority of which continue to provide the backbone for many important airlines.