LXNAV LX8000, Руководство пользователя

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LX8000 (LX8080) Version 2.6 September 2011
Page 41 of 110
The electronic TE compensation can be fine-tuned during flight using the following
procedure. It is essential that this is only done in smooth air; it is not possible to tune the
TE accurately in turbulent air.
Set TE compensation to 100% and TE filter to default. Accelerate up to approximately
160 km/h (75 kts) and keep the speed stable for a few seconds. Gently reduce the speed to
80 km/h (45 kts). Observe the vario indicator during the manoeuvre. At 160 km/h the vario
will indicate about –2 m/s (-4 kts). During the speed reduction the vario should move
towards zero and should never exceed zero (slightly positive indications are acceptable). If
the vario shows a climb the compensation is too low; increase the TE%; and vice versa. Try
another “zoom” to assess the change and make further adjustments if necessary.
The TE filter is the compensation delay and is not used on V5 variometer. Larger numbers
will increase the delay and vice versa. During the first test is recommended to use TE filter
4.
Electronic TE compensation is only effective when the pitot tube and static sources are co-
located and the pneumatic lines to the instrument are approximately the same length. The
best sensor to use is the combined pitot/static Prandtl tube. If problems are experienced
with the electronic TE compensation the most likely cause is the glider's static source. The
static source can be checked by plumbing the pneumatic tubes for electronic compensation
and then setting the TE: to 0%. In still air accelerate to approximately 160 km/h and slowly
reduce the speed. Observe the vario indicator. If the static source is good the vario should
immediately start to move to show a climb. If the needle firstly shows increased sink and
then moves to a climb, the static source of the glider is unsuitable and there is no way to
provide successful TE compensation electronically. The use of a dedicated and accurate fin-
mounted pitot/static source such as a Prandtl tube might help.
5.1.12.1.2 SC Switch
The LX8000 has an input for an external speed command switch which is wired to the vario
unit. Using the external switch it is possible to switch between SC and Vario manually.
Setting the
SC switch
to
ON
means that closing the switch will cause the instrument to
enter SC mode and setting SC switch to
OFF
means that closing the switch will select Vario
mode. There is a third option by setting SC INPUT to
TASTER
and connecting a push
button to the input; each key press will toggle between SC and Vario (mandatory setting for
LX Remote).
There is another input called VARIO PRIORITY. When this input is activated by
grounding the appropriate wire the unit will change over to Vario immediately.
This input wire is set open (not grounded) as a factory default on delivery.
5.1.12.1.3 Temperature Offset
The LX8000 is supplied with an external outside air temperature (OAT) sensor. With the
offset setting it will correct static errors of temperature measurement.
5.1.12.1.4 Altitude Source
The LX8000 has two pressure altitude sensors. One is built into the main digital unit and is
used for the IGC recorder and the second one is built into the vario unit and is connected to
the glider pitot-static system. Changing the altitude source defines which sensor is used for
pressure altitude used in program.