LXNAV V7, Manual

Page: 27 / 39

V7 Version 1.96 Januar 2012
Page 27 of 39
6 Variometer and Altimeter
All signals from the pneumatic sensors (altitude, speed) are derived from high quality
pressure sensors which mean that no flask is necessary. The vario signal is derived from the
altitude signal. All signals are temperature and altitude compensated. Mechanical needle
and colour display show the vario information as well as many other parameters.
The display is user configurable. The variometer can be configured to show:
 Range 5, 10 and 2.5 m/s or 10, 20 and 5 kts.
 time constants 0.1 s to 5 s, in addition there are 4 settings for electronic processing
for the vario signal.
 netto shows the air mass lift and sink.
 relative shows the lift or sink that would be achieved if the glider was circling at the
thermaling speed.
There are two ways by which the vario indications can be corrected for total energy.
Electronic TE compensation based on speed changes with time and pneumatic compensation
with a TE probe. The quality of the TE compensation depends entirely on the location, size
and dimension of the TE tube. The installation must be leak-proof.
If an electronic TE compensation is selected the TE (P
st
) port should be connected
to a good static pressure source. If pneumatic compensation is selected the TE
(P
st
) port should be connected to the TE probe.
Altimeter
The altimeter of the LXNAV V7 is temperature compensated from -20ºC up to + 60ºC. The
altimeter is calibrated up to 20000 m.
6.1 Speed Command
Speed command flying based on the MacCready theory is a very useful tool to optimise
cross-country speed. There are many visual indicators (see Chapter 5.1). When the
instrument changes to speed command mode the audio will change and become a director
informing the pilot whether he is flying too fast or too slow. In order to reduce confusion
between vario and speed command audio some special features are incorporated
 Continuous audio signal in + possible (other kinds of signals can be chosen, see
setup).
 No audio at correct speed (dead band).
TE (Pst)
LXNAV V7
Electronic TE compenstaion
Compensation with TEprobe