Re: airplane structural terms

Date:         13 Feb 99 02:25:50 
From:         David Lednicer <dave@amiwest.com>
Organization: Analytical Methods, Inc.
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> 1. Mean Aerodynamic chord (relating to wing structure)

	This is actually an aerodynamic term.  It refers to a special spanwise
defined as:

                              (b/2)
                             /
        MAC = 1/wing area * / c^2 dy
                           /
                           (-b/2)

where b is the wingspan and c is the local chord.  The MAC is used as a
datum length for calculating pitching moments and is also a datum to
which the aerodynamic center of the wing is referred.

> 2. Percent of mean aerodynamic chord (%MAC) (i think this relates to
> wing loading)

	No, this is actually a way of referring to the aircraft's center of
gravity location.

> 3. Wing incidence

	This is the angle of pitch that the wing is attached to the fuselage
at.

> 1. STA (relating to fuselage) and how are the STA numbers determined?

	Stations (STA) are measurements in the axial direction from some given
reference location.  These measurements, on Boeing aircraft, are made in
inches.  In a true interpertation, fuselage station (FS) 732 is 732
inches aft of the reference.  The nose on the basic 707 is at station
130.  However, the 707 came in various body lengths.  When Boeing
stretched the fuselage to these lengths, they introduced a region of the
fuselage that is all identified by the same station number.  For
example, on the 707-120, the nose moved forward 80 inches (the wing box
stays at the same FS location).  Hence, the nose is really at FS 50
(130-80), but in the Boeing system, the nose is still at station 130,
and from station 620, for the next 80 inches, locations are 620A, 620B,
etc.

	There are also wing, horizontal tail, etc. stations, which are measured
in some local axis system.  Wing stations on the 707 are measured along
the forward spar in the wing chord plane (as near as I can determine).

> 2. WPL (relating to wing) and how are the WPL numbers determined?
> I appreciate any help you may give me.

	Are you sure you're not looking at WBL, not WPL?  WBL is the wing
buttline, measured spanwise in the wing chord plane system.  WBL 0 is at
fuselage BL 6.65 on the 707-120.

-------------------------------------------------------------------
David Lednicer             | "Applied Computational Fluid Dynamics"
Analytical Methods, Inc.   |   email:   dave@amiwest.com
2133 152nd Ave NE          |   tel:     (206) 643-9090
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