connecting Bohli Vario

Can anyone help us with our Bohli vario we recently bought:

Problem is connecting the instrument to the pressure system of the glider. There are two markings 'P' and 'S' but everyone we asked comes with a different answer how to connect resulting in total confusion. Another question is the knob on the front of the vario: what's the purpose of this knob.

Thanks, Erwin

Well, the most probably 'S' stands for 'Static (pressure)', so the other must be for dynamic one (how it is in English... 'TE'?). I mean that one which comes from the pitot.

Regards,

Janusz Kesik Aeroclub Czestochowa
www.soaring.enter.net.pl

Bohli made two types at least. One of them is a standard uncompensated taut band vario and looks to be about an average case size. The other type is a an internally membrane compensated type that is quite large and can be identified by the expanded styrofoam insulation shell and the adjusting knob on the front of the instrument. Cheers, Pete

We have the type with the styroforam insulation and the adjusting knob.

Can you tel us how to connect a what the function of the knob?

according to a Reichman book P stands for Static pressure and p-q stands for TE

You may ask Bohli for a manual.

And tell them they should place the manuals on the webpage.

Tel P 01 363 62 42, Tel G 01 632 43 60, Fax G 01 632 10 21

that's exactly what I just did Erwin

The manual that I have is for the PVF-68 TE variometer (the one with the styrofoam cover and adjusting knob) The manual says to hook the 'S' port to a static source approximately in line with the instrument panel at the widest part of the fuselage at that longitudinal station and have a flush port on each side connected to a tee then to the instrument. The manual also calls for rubber tubing and a water trap in the static system. The other port is to be connected directly to the pitot system. The knob is to be twisted all the way to the 'left' to start, then a series of tests ( pull ups etc.) to adjust the amount of compensation you desire. The unit is internally compensated for 'G' during maneuvers and does not require a capacity bottle.

Thanks for the useful information,

Erwin

Erwin,

you bought one of the best total energy varios and still the fastest one. I guess it is the big, white one (80mm dia). Anyway:

p stands for 'pressure' and has to be connected to the pitot; it measures the total pressure. s stands for 'static' and has to be connected to the static pressure. This pressure should be taken from both sides of the fuselage in the cockpit area for having a short connection only. As this pressure is not fully equal to the real static pressure, but very unsensitive to unexact flying, the necessary vario compensation can be adjusted by the knob you have on the lower left of the instrument. To correct too small compensation, the knob has to be turned to the right and vice versa. As the compensation is different for different altitude, the proscess can be done at various altidudes and the ring around the knob can be marked accordingly. If more quiestions contact Bohli: http://www.bohli-magnete.ch

Happy landings Rudolf