This position is found by placing a straight-edge
and a spirit-level across the engine foundations (both
longitudinally and laterally), and great care should be taken to
see that the bubble is exactly in the centre of the level. The
slightest error will assume magnitude towards the extremities
of the aeroplane. Great care should be taken to block up
the aeroplane rigidly. In case it gets accidentally disturbed
while the work is going on, it is well to constantly verify the
flying position by running the straight-edge and spirit-level
over the engine foundations. The straight-edge should be
carefully tested before being used, as, being generally made of
wood, it will not remain true long. Place it lightly in a vice,
and in such a position that a spirit-level on top shows the
bubble exactly in the centre. Now slowly move the level
along the straight-edge, and the bubble should remain exactly
in the centre. If it does not do so, then the straight-edge
is not true and must be corrected. THIS SHOULD NEVER BE
OMITTED.
In the case of aeroplanes fitted with engines of the rotary
type, the ``flying position'' is some special attitude laid
down in the aeroplane's specifications, and great care should
be taken to secure accuracy.
ANGLE OF INCIDENCE.--One method of finding the angle
of incidence is as follows:
First place the aeroplane in its flying position. The
corner of the straight-edge must be placed underneath and
against the CENTRE of the rear spar, and held in a horizontal
position parallel to the ribs.
Pages:
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131