40 - Two 64.5kN (14,500lb) Pratt & Whitney JT8D-9 turbofans, or two 66.7kN (15,000lb) JT8D-11, or two 69.0kN (15,500lb) JT8D-15s, or two 71.2kN (16,000lb) JT8D-17s.
50 - Two 69.0kN (15,500lb) JT8D-15s, or two 71.2kN (16,000lb) JT8D-17s.
40 - Max cruising speed 898km/h (485kt), long range cruising speed 820km/h (443kt). Range at high speed cruise with 70 passengers and reserves 1725km (930nm), range with 87 passengers and reserves at long range cruising speed 2880km (1555nm).
50 - Speeds same except for max speed 926km/h (500kt). Range at long range cruising speed with 97 passengers and reserves 3325km (1795nm).
40 - Empty 26,612kg (58,670lb), max takeoff 54,885kg (121,000lb).
50 - Empty 28,068kg (61,880lb), max takeoff 54,885kg (121,000lb).
40 - Wing span 28.47m (93ft 5in), length 38.28m (125ft 7in), height 8.53m (28ft 0in). Wing area 93.0m2 (1000.7sq ft).
50 - Same except for length 40.72m (133ft 7in).
Flightcrew of two.
40 - Seating for up to 125 passengers at five abreast.
50 - Seating up to 139 passengers at five abreast and 79cm (31in) pitch.
Total DC-9 production of 976, including 71 Series 40s and 96 Series 50s. Approximately 53 -40s and 46 -50s remained in service in late 2002.
Short to medium range airliners
The DC-9-40 and DC-9-50 are stretched developments of the DC-9-30 and predecessors to the later further lengthened MD-80 and MD-90 series.
The DC-9-40 was developed in response to a Scandinavian Airlines System (SAS) requirement for a larger capacity development of the DC-9. Compared with the DC-9-30, the DC-9-40 is 1.88m (6ft 2in) longer, raising seating capacity in a single class configuration to 125. Apart from the fuselage stretch and more powerful engine options, the -40 was the much the same as the -30. First flight occurred on November 28 1967, and the -40 entered service with SAS on March 12 the following year.
The DC-9-50 is the largest member of the DC-9/MD-80/MD-90/717 family to bear the DC-9 designation. Launched in mid 1973, the DC-9-50 is a further 2.44m (8ft 0in) longer than the DC-9-40, or 4.34m (14ft 3in) longer than the DC-9-30, and has maximum seating for 139 passengers. Delivered from August 1975, the DC-9-50 introduced a new look cabin interior designed to make more efficient use of the space available and give the impression of a more spacious interior, plus other improved features such as an improved anti skid braking system and quieter engines compared with the DC-9-40.
The DC-9-40 and -50 sold only in fairly modest numbers before the arrival of the further stretched MD-80 series. The largest DC-9-40 customer was SAS, while Northwest continues to operate a large fleet of DC-9-40s and -50s (it is currently the largest DC-9 operator in the world).