Douglas DC-9 - Modern Airliners

The Douglas DC-9 is a short to medium range airliner and was the last to be fully designed and produced by the Douglas Aircraft Corporation.

Back in the 1950s, Douglas was looking to fill the short to medium range airliner space. They already had the DC-8 which served the medium to long range and intercontinental market. But now they needed to find a solution to be able to serve small and remote locations as well. The investigation into a solution took serveral different turns and many years before a final design was settled upon. They looked into a scaled down 4 engine version which slightly resembled the Convair 880, a model that didn’t really meet with any success. Douglas also looked at what European manufacturers were doing, with particular interest in the British Aircraft Corporation’s BAC111 and Sud Aviation’s Caravelle.

Eastern Airlines DC-9-10 N8909E on appraoch to Washington DCA.

Both the Caravelle and the BAC-111 were twin rear mounted engined airliners playing in the same space, the short to medium range that Douglas was aspiring to. The Douglas Aircraft Corporation even went so far as to sign a contract with Sud Aviation of France to build a Caravelle based aircraft under licence, provided they got enough interest.

Customers stayed away in droves, so that agreement was abandoned in 1960.

Douglas went back to the drawing board in 1962 with a view to designing a 63 seat airliner weighing 36,300Kg (80,000lb). On the 8th of April 1963, Douglas approved the new design and the DC-9 was on its way to becoming an actuality.

Simply, the design was for a twin-engine airliner with two rear fuselage mounted engines, namely the Pratt and Whitney JT8D turbofan. The tail would be a T-tail configuration with the horizontal stabilisers mounted on top, and the main wings would be small and of a highly efficient design. In fact, the first model, the DC-9-10 had no leading edge slats as the wing was desgined for high lift to aid with short field performance. This design had several advantages in that no engines on the wings meant more uninterrupted lifting surface area. Additionally, the flaps could run the entire length of the wing, providing a much higher amount of lift in those lower speed stages of flight. The absence of engines slung below the wings also meant that the aircraft could be lower to the ground on its undercarriage. This allowed for much easier access for baggage handlers.

The first production model of the DC-9 took to the air on 25 February 1965 and by July of that year was accompanied by four more. After an intensive testing program, certification was granted for the type on 23 November 1965. The certification limited the aircraft weight to 36,300Kg (80,000lbs) due to the two-man crew configuration. This restriction was later lifted, which was good news as Douglas always intended the DC-9 to come out in various configurations and sizes.

Launch customer, Delta Air Lines, received thier first DC-9 0n 08 December 1965.

To look at, one could notice some similarity to the BAC-111. However, the DC-9 was designed for short hops, some of which would be to un-serviced airfields. Douglas designed some autonomy into the DC-9 so that it was not dependant on ground services at these airports. These features included an A.P.U. (Auxilary Power Unit), which was a smaller engine housed inside the rear fuselage. This engine would be activated whilst the aircraft was on the ground with the main engines powered off. It would supply any electricity requirements whilst the aircraft was stationary and also the power to restart the main engines. In addition, a passenger staircase was located in the rear of the aircraft which dropped down between the engines from the bottom of the fuselage. This enabled boarding without the aid of airport provided stairs.

A DC-9-32 of South African Express clearly shows the rear stairway deployed and if you look closely at the front stairs, they can be seen to be attached below the front passenger door. These features plus the A.P.U. (auxiliary power unit), enabled the DC-9 to be autonomous at non-serviced airfields.

An additional optional feature was a front door stairway which stowed itself under the floor beneath the main passenger left-hand front door. On activation, a flap on the exterior below the door would open and the stairway would be slid out in a folded condition by an actuator motor. It would move out horizontally until fully extended, at which time it would then ease down to the ground with the handrail deploying as it went. This was also an option for early Boeing 737 aircraft as well.

As mentioned above, Doulas always intended to produce different variants of the DC-9. For example, the DC-9-10 was also produced as a passenger/cargo version, in fact, two versions. They were the 15MC9 Minimum Change where at night when passenger services ceased the seats could be folded to the rear and cargo carried overnight. The other option was the 15RC Rapid Change, where the seats were removed on pallets giving use of the full cabin for cargo. Both models were supplied with a 3.5M x 2.1M cargo door forward of the wing and a strengthened floor.

Delta McDonnell Douglas DC-9-50, the longest of the DC-9 series.

New competition was emerging from the Boeing camp in the form of the Boeing 737 and Douglas rose to the challenge with the DC-9-30. This variant had a longer fuselage, extended wing tips and was offered with various versions of the JT8D engine as well as full-length wing slats. First flying on 01 August 1966, it entered service with Eastern Air Lines in February 1966. 662 of the type were built.

In response to requests from Scandinavian Airlines System (SAS) who needed a variant designed for short field operations, Douglas came up with the DC-9-20. This model came with more powerful engines and the larger wing of th DC-9-30 which provided the higher performance required by SAS. First flying on 18 September 1968, the type gained certification on 25 November 1968 and was delivered to SAS on 11 December 1968. SAS, the only customer for DC-9-20, flew their first service with the type on 27 January 1969. The order for ten airframes was concluded with last delivery on 01 May 1969.

Douglas further lengthened the DC-9 in the form of the DC-9-40. First flying in March 1968 with SAS, Douglas went on to build 71 of the type.

Scandinavian Airlines System (SAS) DC-9-41

The largest of the DC-9 family of airliners was the DC-9-50. First flying in 1974, it entered service with Eastern Air Lines in August of 1975. 96 of the type capable of carrying 139 passengers were delivered. As technology improved, each new variant came with updated features and improvements. The -50 came with a small fin under each of the side cockpit windows, spray deflectors for the nose wheel and the reverse thrust angled up 17 degrees. The latter was developed by Air Canada and adopted by the aircraft maker.

Delivering 976 DC-9 aircraft, the merged McDonnell Douglas company (1967) saw this as a great success. The last DC-9 was delivered in 1982. That was not the end of the story. McDonnell Douglas went on to produce the MD-80 and the MD-95. The latter was actually renamed the Boeing 717 when McDonnell Douglas merged with Boeing in 1997.

Douglas DC-9 Specs.

Douglas DC-9
Variant	-10	-20	-30	-40	-50
Flight Crew	2
Milestones
Maiden Flight	25 FEB 1965	18 SEP 1968	01 AUG 1966	28 NOV 1967	1974
Entry Into Service	08 DEC 1965	27 JAN 1969	FEB 1967	MAR 1968	AUG 1975
Launch Airline	Delta Air Lines	Scandinavian Airline System	Eastern Air Lines	Scandinavian Airline System	Eastern Air Lines
Number Produced	137	10	621	71	96
Dimensions
Number of Passengers (1 class)	90		115	125	135
Passenger Limit by Exits	109		127	128	139
Aircraft Length	31.82M (104F 5I)		36.36M (119F 4I)	38.28M (125F 7I)	40.72M (133F 7I)
Height	8.4M (27F 7I)		8.5M (27F 11I)	8.7M (28F 5I)	8.8M (28F 9I)
Wing Span	27.25M (89F 5I)	28.44M (93F 4I)	28.44F (93F 4I)		28.45M (93F 4I)
Fuselage Width	3.34M (11F)
Cabin Width	3.11M (10F 2I)
Cargo	17M³ 600F³		25.3M³ 895F³	28.9M³ 1,019F³	33.2M³ 1,174F³
Weights
Max. Takeoff Weight(MTOW)	41,141K (90,700lb)	45,359K (98,000lb)	48,988K (108,000lb)	51,710K (114,000lb)	54,885K (121,000lb)
Max. Landing Weight(MLW)	37,058K (81,700lb)	43,227K (95,300lb)	44,906K (99,000lb)	46,266K (102,000lb)	49,895K (110,000lb)
Max. Empty Weight(MEW)	22,300K (49,162lb)	23,879K (52,644lb)	25,789K (56,855lb)	27,821K (61,335lb)	29,336K (64,675lb)
Max. Fuel	11,223K (24,743lb)		11,181K (24,649lb)
Performance
Engines x 2	JT8D (Various models)
Thrust	54.5kN(12,250lbf) – 71kN(16,000lbf)
Ceiling	35,000F (11,000M)
MMo	484Kn / Mach 0.84 / 897kph
Range	1,300NM (2,400Km)	1,500NM (2,800Km)		1,200NM (2,200Km)	1,300NM (2,400Km)