DG Flugzeugbau DG 202, Flight Manual

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V
V
A
A
R
R
I
I
O
O
M
M
E
E
T
T
E
E
R
R
5
5
S
S
T
T
V
V
5
5
Vane type variometers measure the change in air pressure inherent to
changes in altitude. The instrument consists of a cylindrical chamber with a
precision-fit baffle plate (vane) rotating on shockproofjewel bearings and
centered by a coil spring. The vane divides the chamber in two: one section
is open to static pressure, while the other is connected to an expransion
tank, in which a volume of air is insulated against the thermal effects.
Differences in pressure are compensated by the narrow gap between vane
and chamber wall. There is a change in static pressure when an aircraft
climbs or descends, and a differential pressure is established between the
two sections of the chamber. The resultant deflection of the vane provides a
measure of the vertical speed and this deflection is transferred to the
pointer of the instrument.
The response rate of a variometer is important. In high-performance gliding,
upcurrents can be identified all the quicker and used all the more efficiently
if the variometer responds without delay.
Defined as the length of time the instrument takes to reach 65% of its final
reading in response to a sudden change in vertical speed, the time constant
serves as a standard for gauging speed of response. The faster a
variometer responds, the smaller is its time constant.
Vane type variometers with large measuring ranges such as 5 StV 5 (±10 m/sec. and ±15 m/sec.) have small
time constants. The volume of the expansion tank must be increased in order to achieve comparable figures
with variometers having the most common measuring range (±5 metres/second).
Application
Indicates the aircrafts’s vertical speed (rate od climb, rate of descent).
The variometer is the most valuable aid on all types of aircraft for pilots wishing fully to expoit the prevailing
thermal concitions. The variometer with linear dial calibration can be used in conjunction with a MacCready
ring. The separate 0,45 litre equalization reservoir is easy to install. responsive and exact display, linear dial
calibration, shock-resistant shafts
Technical data
Black plastic housing see scale drawing indicating range see table for installation dimensions, see table of
vane type variometers for time constants,
weight 0,260 kg
volume of expansion tank 0,45 litre
equalization reservoir dimensions
;
:
0,45 litre, 65 mm Ø, 280 mm long, 190 g
0,9 litre, 80 mm Ø, 350 mm long, 300 g
Maintenance
A leak test should be performed annually. Otherwise the instruments require no maintenance.
Test and repair
Normally the instruments remain serviceable and accurate over a long period of time. If test or repair become
necessary, the instrument is to be sent to the manufacturer or a qualified repair station.
The instrument should be packed in shock absorbing material, and the connection fittings should be sealed.
We strongly advise against service by unqualified personnel. We recommend that variometers are retested
after 5 years.