Classic Jetliners: The McDonnell Douglas DC-9

As a frequent flyer or aviation enthusiast, you might be familiar with the McDonnell Douglas DC-9. As an avgeek myself, I was intrigued by the unique features of these planes, such as the engines at the back and the distinctive T-tail. During that time, my favorite regional plane was the BAC One-Eleven. However, my interest in the DC-9 was piqued when I came across pictures of a Swissair DC-9 that resembled the One-Eleven. This led me to delve deeper into learning about the McDonnell Douglas DC-9.

Back in 1998, Cebu Pacific was the only airline in the Philippines that operated the DC-9. Other airlines such as Air Philippines, Asian Spirit, and Spirit of Manila, later operated the MD-80 series, which was a derivative of the DC-9. Interestingly, Cebu Pacific had planned to acquire Boeing 717s, which was the final derivative of the DC-9, but ultimately the deal did not materialize.

So what is the McDonnell Douglas DC-9? It’s time to get to know more about this plane.

An Overview

The DC-9 is an American-built single-aisle, five-abreast plane designed by the Douglas Aircraft Company. Initially known as the Douglas DC-9, it was later produced by McDonnell Douglas starting in August 1967.

The DC-9 was created as a response to the need for smaller aircraft for shorter flights. Douglas had previously introduced the larger DC-8 in 1959, but recognized the need for a more compact plane. On April 8, 1963, the company approved the design for the all-new DC-9.

One unique feature of the DC-9 is its two rear-mounted Pratt & Whitney JT8D low-bypass turbofans under a T-tail. This design choice helps to reduce drag and improve the plane’s overall aerodynamics. The DC-9 also features a two-person flight deck and built-in airstairs, making it a versatile and practical aircraft for many different types of flights.

Despite being an older model, the DC-9 has proven to be a reliable and long-lasting plane. Its service record spans several decades, and it has been flown by numerous airlines around the world. The McDonnell Douglas DC-9 may not be the most cutting-edge aircraft on the market, but its impact on aviation history is undeniable.

History of the DC-9

During the 1950s, the Douglas Company studied the possibility of creating a short- to medium-range airliner to complement their existing high-capacity, long-range DC-8.

One of the initial designs was the Model 2067, a medium-range, four-engined plane. However, there wasn’t enough interest from airlines and the idea was eventually abandoned. In 1960, Douglas signed a technical cooperation agreement with Sud Aviation. Under the agreement, Douglas would market and support the Sud Aviation Caravelle and produce a licensed version if there was enough demand. Unfortunately, no orders were placed and the agreement expired after two years.

In 1962, Douglas began working on design studies for a new plane. The first version was meant to seat 63 passengers and have a gross weight of 69,000 pounds. Eventually, this design was changed into what would become the initial DC-9 variant. On April 8, 1963, Douglas gave the green light to begin production of the DC-9.

What set the DC-9 apart from its competition, such as the larger Boeing 727 trijet, was that it was an entirely new design. While the 727 relied on many 707 components, the DC-9 was created from scratch. This allowed for greater flexibility in terms of design and performance.

The first production model took to the skies on February 25, 1965, followed closely by a test fleet of five aircraft just a few weeks later. By July of that year, the fleet was up and running, paving the way for the initial Series 10 to gain airworthiness certification on November 23, 1965. Just a few weeks later, Delta Air Lines put the DC-9 into service on December 8, 1965.

One of the key selling points of the DC-9 was its versatility. The plane 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 wingtips, took flight on August 1, 1966, entering service with Eastern Air Lines the following year. The initial Series 10 was followed by the improved -20, -30, and -40 variants. The final DC-9 series was the -50, which first flew in 1974.

Overall, the DC-9 was a commercial success for the manufacturer. Production took place in Long Beach, California, starting in 1965, with the final DC-9 rolling off the assembly line in December 1982. During that time, McDonnell Douglas delivered 976 DC-9s and 108 MD-80s. Interestingly, the DC-9 shares its line number sequence with the second generation of the DC-9 family, the MD-80.

Design and Technologies

The DC-9 is equipped with two rear-mounted Pratt & Whitney JT8D turbofan engines, small wings, and a T-tail. The aircraft’s takeoff weight was limited to 80,000 lb (36,300 kg) for a two-person flight crew according to the Federal Aviation Agency regulations at the time. The plane has five seats across for economy seating and can seat 80 to 135 passengers, depending on the version and seating arrangement.

The DC-9 was designed to be accessible to smaller airports and had short-field characteristics. Turnarounds were simplified by built-in airstairs, including one in the tail, which shortened boarding and deplaning times. The tail-mounted engine design facilitated a clean wing without engine pods, providing numerous advantages. Flaps could be longer and 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, lowering field length requirements while keeping the wing structure light.

The DC-9’s engines are mounted on the tail, reducing foreign object damage from ingested debris from runways and aprons. However, this position makes the engines susceptible to ingesting ice streaming off the wing roots. The absence of engines in underslung pods allowed a reduction in fuselage ground clearance, making the aircraft more accessible to baggage handlers and passengers.

DC-9 Variants and Specs

DC-9-10:

• Crew: 2 (pilot and co-pilot)
• Capacity: 80-90 passengers
• Length: 104 ft 4 in (31.80 m)
• Wingspan: 89 ft 5 in (27.25 m)
• Height: 27 ft 6 in (8.38 m)
• Wing area: 925 sq ft (85.9 m2)
• Empty weight: 49,905 lb (22,638 kg)
• Max takeoff weight: 90,700 lb (41,136 kg)
• Powerplant: 2 × Pratt & Whitney JT8D-5 turbofan engines, 12,250 lbf (54.5 kN) thrust each
• Range of 1,750 nautical miles (3,240 km) and maximum service ceiling of 35,000 feet (10,670 m).

DC-9-20:

• Crew: 2 (pilot and co-pilot)
• Capacity: 89-115 passengers
• Length: 119 ft 4 in (36.37 m)
• Wingspan: 89 ft 5 in (27.25 m)
• Height: 27 ft 6 in (8.38 m)
• Wing area: 925 sq ft (85.9 m2)
• Empty weight: 52,446 lb (23,788 kg)
• Max takeoff weight: 115,000 lb (52,163 kg)
• Powerplant: 2 × Pratt & Whitney JT8D-7 turbofan engines, 14,000 lbf (62 kN) thrust each
• Range of 1,000 nautical miles (1,850 km) and maximum service ceiling of 35,000 feet (10,670 m).

DC-9-30:

• Crew: 2 (pilot and co-pilot)
• Capacity: 115-135 passengers
• Length: 119 ft 4 in (36.37 m)
• Wingspan: 89 ft 5 in (27.25 m)
• Height: 27 ft 6 in (8.38 m)
• Wing area: 925 sq ft (85.9 m2)
• Empty weight: 53,846 lb (24,417 kg)
• Max takeoff weight: 123,000 lb (55,792 kg)
• Powerplant: 2 × Pratt & Whitney JT8D-9 turbofan engines, 14,500 lbf (64 kN) thrust each
• Range of 1,150 nautical miles (2,130 km) and maximum service ceiling of 35,000 feet (10,670 m).

DC-9-40:

• Crew: 2 (pilot and co-pilot)
• Capacity: 125-135 passengers
• Length: 130 ft 5 in (39.75 m)
• Wingspan: 93 ft 4 in (28.45 m)
• Height: 27 ft 6 in (8.38 m)
• Wing area: 1,010 sq ft (94 m2)
• Empty weight: 58,395 lb (26,458 kg)
• Max takeoff weight: 139,000 lb (63,049 kg)
• Powerplant: 2 × Pratt & Whitney JT8D-9A turbofan engines, 15,000 lbf (67 kN) thrust each
• Range of 1,850 nautical miles (3,430 km) and maximum service ceiling of 35,000 feet (10,670 m).

DC-9-50

• Crew: 2 (pilot and co-pilot)
• Capacity: 135 passengers
• Length: 119 ft 3 in (36.34 m)
• Wingspan: 93 ft 5 in (28.47 m)
• Height: 27 ft 5 in (8.36 m)
• Wing area: 1,090 sq ft (101 m2)
• Empty weight: 53,081 lb (24,088 kg)
• Max takeoff weight (MTOW): 108,000 lb (48,990 kg)
• Powerplant: 2 × Pratt & Whitney JT8D-17 turbofan engines, 16,000 lbf (71 kN) thrust each
• Range of 1,400 nautical miles (2,590 km) and maximum service ceiling of 37,000 feet (11,278 m).

The Later Generations and End of Production

Throughout its nearly 40 years of production, the DC-9 underwent several evolutions and became the foundation for a family of aircraft that served airlines around the world. The DC-9’s second generation was introduced in 1980 as the MD-80 series, which was essentially a lengthened DC-9-50 with a larger wing and a higher maximum takeoff weight (MTOW). This evolution of the aircraft made it more efficient and allowed for increased passenger capacity.

The MD-80 series was then further developed into the third generation, the MD-90, in the early 1990s. This new version of the aircraft had a longer body than the MD-80, and was fitted with V2500 high-bypass turbofans and an updated flight deck. These improvements made the MD-90 even more efficient and capable than its predecessors.

The final version of the DC-9 family was the MD-95, which was renamed the Boeing 717 after McDonnell Douglas’s merger with Boeing in 1997. The Boeing 717 had a shorter body than the MD-80 and MD-90, and was powered by Rolls-Royce BR715 engines. Despite its smaller size, the Boeing 717 was a popular aircraft for airlines and was used primarily for passenger flights.

The DC-9 family was produced between 1965 and 2006, with a total delivery of 2,441 units. This includes 976 DC-9s, 1,191 MD-80s, 116 MD-90s, and 155 Boeing 717s. As of August 2022, approximately 250 aircraft remain in service, with 31 DC-9s being used for freighter flights, 116 MD-80s being mainly used for freight, and 103 Boeing 717s still being used for passenger flights. The MD-90 was retired without being converted for freighter use. Despite the many changes and updates made to the DC-9 family over the years, the aircraft’s basic design principles have remained popular and continue to influence aircraft design today.