DG Flugzeugbau DG 202, Flight Manual

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Manual Compass 46--MFK--1 BOHLI MAGNETTECHNIK AG
Edition 01.2007 Page 8 of 16
Some special reflections are necessary in order to correctly determine the angular advance
to compensate time lags (fig. 8). Since different flying manoeuvres are applied for shifting to-
wards the center, depending on personal preference and type of glider (levelling--out or sli-
deslipping with opposite rudder, etc.), the amount of angular lag compensation is to be deter-
mined individually by each pilot. Point
✹ is the location of strongest lift during the circle. With
feeling alone it is hardly possible to determine this point exactly; the lift usually increases gra-
dually and we cannot “feel” the peak. Due to its lag, the variometer will indicate maximum
climb at point
● . The amount of turn that was flown during the variometer lag is shown by the
angle ; it represents the angle a by which the heading has changed from ✹ to ● in direction
of circling. When using a fast variometer, one must reckon with a time lag of approximately
3 sec. With a full--circle time of 16 sec (40 -- 45
° bank) this causes an angular lag of a = 67.5 °
(360
°
: 16 x 3 = 67.5
°
).
Fig. 8 Fig. 9
center of
thermal
center of
thermal
flight path
If we add the angle b which is to counter--act the roll--out lag and if b
= 25 °
, we obtain 92.5
°
or approx. 90
°
total angular lag. In consequence, roll--out for shifting towards the center must
be initiated 270
°
-- 90
°
= 180
°
after the moment of maximum climb indication. If we work with
the compass it is not necessary to take readings of headings and make calculations; there
is an easier way. At the moment of best climb indication, we mentally retain the position of the
red mark and project it across the center of the dial into the opposite quadrant. Thus, the hea-
ding for initiating straight flight (roll--out) becomes evident at a glance.
If a 90
°
total angular lag was a correct assumption for a specific flying style, glider and vario-
meter, then we are gradually shifting closer towards the center of the thermal. The reading
of the heading at best climb
● should remain the same after every manoeuvre. If we have
reached the center, there will be an almost identical climb indication on the variometer around
the full circle. If we have overshot the center of the thermal, then the heading at the moment
of best climb will suddenly he 180
° opposite from before.