Drag index calculation

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johnwill

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Unread post11 Jan 2011, 18:38

ilter79,

I don't remember seeing any store location reference, but I suppose it could be true. Due to spanwise flow and fuselage interference effects, there are differences in flow at different wing stations.

Remembering that drag index is supposed to be used only to assist in estimating cruise drag effects, profile drag is the dominant type of drag in cruise condition. So I suppose I'd have to agree with the statement. As I recall, somewhere there are tables to estimate cruise fuel burn as related to total (airplane plus stores), perhaps at different altitudes. As I said earlier, the drags are for 0.8 mach number.

Roscoe,

I can see that roll moment coefficients are related to span more than to MAC, not so clear about yaw moment. However, any reference length would suffice for any coefficient. As would any reference area. For example, drag coefficients are much more physically related to cross section area rather than wing area, but wing area works just fine. It is what it is.
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easer

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Unread post23 Feb 2019, 21:57

Hi, I were looking for drag indexes as well, and not much to be found on the net except for this thread....

What I were wondering is how much less drag the "conformal" fuselage-mounted missiles of the Eurofighter has, relative to what drag they would have if mounted via a more traditional launcher....?

Bjarke
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johnwill

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Unread post24 Feb 2019, 05:29

I don't have any numeric answers for you, but the drag reduction is very significant. Two reasons (at least) for that - no pylon drag and the missile is within the boundary layer of air around the fuselage. Several other airplanes use conformal mounting - F/A-18, F-15, F-CK1 (Taiwan IDF), F-16XL, maybe more.
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