Aerodynamic Fixes for the McDonnell Douglas MD-11
The McDonnell Douglas MD-11, a tri-jet configuration aircraft, was designed for long-haul flights but faced issues with fuel burn and range. To address these problems, McDonnell Douglas introduced several aerodynamic fixes, including wingtip devices, a smaller horizontal stabilizer, and modifications to the flap-hinge fairings and seals.
The McDonnell Douglas MD-11 is a well-known aircraft among enthusiasts for its striking tri-jet configuration and popularity with cargo operators. It was designed specifically for long-haul flights as an improved derivative of the McDonnell Douglas DC-10. To make it more capable and efficient, McDonnell Douglas introduced several minor improvements to the plane's aerodynamics, in addition to updated engines and a stretched fuselage.
## Aerodynamic Improvements The MD-11 featured several aerodynamic improvements, including wingtip devices, a smaller horizontal stabilizer, and modifications to the flap-hinge fairings and seals. These improvements were designed to reduce fuel burn and increase the aircraft's range. The wingtip devices, for example, were reported to reduce fuel burn by as much as 2.5%. The smaller horizontal stabilizer also reduced drag during cruise, cutting fuel burn.
## Comparison of Aerodynamic Features The following table compares the aerodynamic features of the MD-11 with other aircraft: | Aircraft | Wingtip Devices | Horizontal Stabilizer Size | Flap-Hinge Fairings | | --- | --- | --- | --- | | MD-11 | Split tip winglets | 30% smaller than DC-10 | Improved fairings and seals | | Boeing 777 | Initially no wingtip devices | Larger than MD-11 | Different design | | Airbus A340 | Wingtip fences | Larger than MD-11 | Different design |
## Additional Improvements McDonnell Douglas also made additional improvements to the MD-11, including modifications to the wing-pylon fillet and the introduction of a longitudinal stability augmentation system (LSAS). The LSAS software was designed to decrease drag and improve handling. The Phase IV package, introduced in 1996, was a thorough overhaul of the aircraft, incorporating several improvements, including changes to the LSAS software and modifications to the flap-hinge fairings and seals.
## Impact of Aerodynamic Fixes While the aerodynamic fixes improved the MD-11's fuel burn and range, they were not enough to save the aircraft from its overall poor performance. The MD-11 was ultimately unable to compete with rival aircraft, such as the Airbus A340 and Boeing 777, which offered better fuel efficiency and range. The aerodynamic fixes were seen as a band-aid solution, and the aircraft's poor performance was attributed to its heavy weight, undersized wing, and outdated design.
