.0 - NOTE - SEMS and MEASURE of the TOTAL ELASTIC ENVELOPE (EE) In the next Fig. 1 we suppose the white curve AB is the structural axis of a wing which represents its elastic envelope (EE). The lines AC and BC represent the tangents of the rotation angles of points A and B.

1. NOTE - SEMS and MEASURE of the TOTAL ELASTIC ENVELOPE (EE)
In the next Fig. 1 we suppose the white curve AB is the structural axis of a wing which represents its elastic
envelope (EE). The lines AC and BC represent the tangents of the rotation angles of points A and B.
The following Fig. 2 represents an elastic envelope (EE-EE') which is a section or part of the total elastic
envelope AE represented in Fig. 3.
The next Fig. 3 represents an exaggerated elastic envelope of a wing with 5 equidistant sensors SEMS
(points A, B, C, D and E) and consequent 4 elastic envelopes AB, BC, CD and DE of the same length. The
figure shows that each part of the elastic envelope is linked to the next by the same Tg. as displayed in
blue at points B, C and D.
The Tg. at point C correspond to c.d.g. of the wing or aircraft. This point or Tg. at C would be the Tg. of
reference or calibration. For example, said calibration could be symmetrical under ideal flying conditions
in the same wind direction and uniformly distributed load. Another example of Tg. of reference would be
the point c.d.p. (center of pressure of the wing), which in this case would be the point where the maximum
lift (opposed thrust to gravity) occurs at cruising speed.
C
A B
θA θB
θA,θB = Rotation Angles
θT = Total Rotation Angles = 180º - (θA+θB)
θT
Fig. 1
Fig. 3
c.d.g.
Tg. of reference in point C
B
C
D
EA
θS
EE
EE’
θA
θB
θS = Structural Rotation (AB)
θT
Fig. 2

2. NOTE
When we say: "this calibration may be symmetrical under ideal flying conditions in wind direction and
uniformly distributed load", it is mainly referring to the calibration of the structural symmetry of the aircraft
among its main parts: wings, fuselage, stabilizers, rudder, engines, landing gear.
This data must be an exact indicator of the ageing (fatigue) of the whole airplane's structure by the range of
its elasticity and recovering.
Miguel Cabral Martín