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noise and large quantities of smoke (especially with water injection!)
Turbofan engines solved these problems by adding an additional “fan” in front of the
engine core to blow cooler air around the core. This added thrust, and greatly decreased
the amount of noise generated at high power levels. Initial turbofan jet engines included
the P&W JT3D, at 18,000 lbs thrust, which powered the 707-320 and DC-8 Series 50/60
and the Rolls-Royce Conway, installed on the DC-8 Series 40 and 707-436. However, the
huge wide-bodied aircraft of the late 1960s needed something with even more thrust.
For the DC-10 Series 10, the General Electric CF6-6 was developed, with a single engine
generating 40,000 lbs (or the equivalent of all four JT3Cs on a 707-120!), or 120,000 lbs
total. The Series 20 was designed around the Pratt & Whitney JT9D 45,000 lb turbofan,
the same engine that powered the 747 and early 767 models. As with most other
airlines, later versions had more powerful engines. The Series 30 used the 51,000 lb GE
CF6-50, and the Series 40 was powered by the JT9D, rated at 53,000 lbs.
In closing, the descendants of the CF6 deserve mention. GE and SNECMA moteurs of
France later jointly developed the CFM56, a high bypass turbofan engine. These 18,500
to 34,000 lbs thrust engines were initially designed for the United States Air Force’s KC-
135 tanker re-engine program, replacing JT3C and JT3D engines. They were used in a
similar fashion in the “Series 70” of the DC-8, and as original equipment on modern
aircraft such as the Boeing 737 (300 series onwards), Airbus A319/A320/A321, as well
as the original A340-200.
McDonnell-Douglas MD-11 Operating Manual
Page 3
THE MD-11 TAKES OFF
As McDonnell-Douglas went into the design study of Series 50 and then the Series 60
DC-10, they eventually decided to launch a much more advanced aircraft based on the
DC-10. The DC-10-60 eventually became known as the MD-100, the MD-XXX and finally
the MD-11.
The MD-11 program was launched on December 30th, 1986, with the first delivery to
Finnair taking place on December 7th, 1990. It brought a lot of improvements over the
DC-10, including the following:
A stretched fuselage (6.68 meters longer, approximately 20 feet)
Longer wing
Winglets for better stability
Refined airfoils on wing and tail plane
More powerful engines
Strong composite parts on flaps, etc.
First all digital glass cockpit in a commercial aircraft
Two member flight crew, instead of three
Larger fuel capacity, 2,000 gal more
Longer range, up to 8,225 nm in ER version
First complete ‘fly-by-wire’ flight capabilities
Option of Propulsion Controlled Aircraft PCA
McDonnell-Douglas MD-11 Operating Manual
Page 4
The new MD-11 was large enough to fly up to 410 passengers, making it a serious
competitor to the Boeing 747/777, and the Airbus A330/A340, the world’s largest
commercial aircraft. The MD-11 is the largest wide body tri-jet ever built, and quite
possibly the last one, since subsequent large aircraft designs have used either two or
four engines.
The advanced, fully computerized, six-cathode ray tube display digital flight deck, also
called the “glass cockpit”, was now used to take over most of the flight engineers job.
Monitoring engine performance, it has wind shear detection & guidance devices, dual
flight management systems to conserve fuel and dual autopilots with fail operational
capability. With these improvements, the flight crew is now reduced to the Captain and
First Officer. The MD-11 was the first commercial aircraft to truly “fly – by – wire” from
takeoff to landing (United States to Germany) without a pilot’s hands on the controls.
Another notable improvement was the concept of a Propulsion Controlled Aircraft, or
PCA. Developed by NASA and tested on an MD-11 in 1995, this revolutionary system
allowed the safe landing of the aircraft with the hydraulics switched off. PCA uses the
aircraft’s autopilot together with programming in the flight control computers, and
operates the aircraft solely by increasing or decreasing engine thrust. Increasing thrust
in all engines allows the plane to climb, decreasing allows descent, and alternating
thrust in left or right engines independently, allows for turns. If a plane has a major
mishap, losing its hydraulics for flaps, ailerons, rudder, or elevators, it can still
potentially make a safe landing. This is not as far-fetched as it may seem, as one two
separate occasions disabled DC-10 aircraft were landed based on manual control of
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