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Name: Ken
Status: Other
Grade: Other
Location: FL
Country: United States
Date: May 2006


Question:
Does the propulsion type of an aircraft have any effect on whether the wings are on top or bottom of the aircraft? Specifically, are all jets bottom winged?



Replies:
Actually, no. Take, for example, the C-141, C-5, and C-17 cargo planes. They are all High wing jets. The arrangement of aircraft components is actually determined at design by several factors. Most important of which is "what mission is this aircraft going to have to perform most of the time?" After a bit of study, you begin to notice that aircraft that fly similar missions look similar. It is one aspect of "form follows function."

Some short examples: The cargo planes mentioned above are high wing primarily to make loading and unloading of cargo easier by getting the fuselage as low as possible. Fighter planes are usually mid wing with little or no dihedral to have neutral stability. This increases maneuverability. Engines placed above the wing (like on honda's jet), reduce FOD damage to the engines (arguably the costliest single replaceable component of an airplane) and place the fuselage closer to the ground to make it easier to get in and out.

There is much more to it that there is not room to go into here. Check out the book "The Anatomy of the Airplane" by Darrol Stinton at http://www.aiaa.org/content.cfm?pageid=360&id=567 if you are interested in learning more about why aircraft look the way they do. It is the only resource I know that goes into it in detail.

David Brandt P.E.


Ken,

On a simple level, there is no relation between propulsion type and wing placement. On a slightly more involved level, the only relation is allowing a clear area for the engines, which does not interfere with airflow over the wings. Thus, you may place the wings of an aircraft near the bottom, top, or middle of an aircraft regardless of what moves it through the air.

Many fighter jets feature wings mounted near the middle or top of the aircraft, while a great majority of large commercial aircraft have thier wings mounted quite low. In both cases, a strong argument may be placed on the accesability of the wings as a cause for wing placement. Maintenance crews for combat aircraft need to be able to get under the wings to attach weapons and sensor pods, while much larger commercial airliners need thier wings mounted low so the engine pods themselves will be within reach for ground crews.

Ryan Belscamper



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