At 09:48 AM 11/06/2011, you wrote:
With head wind tail wind problems most instruments will have a
digital ASI reading and this should be checked to the WInter ASI at
about 80KTS. The digital ASI should be within say 2 (to 3) kts of
the Winter. If not then something should be done and in the case of
LNAV read page of the Manual and if really bad (more than 40 counts)
then it may have to be sent in for service. Head/tail information
will be all over the shop if you have a problem there as 4kts
digital ASI error can make a big error in Head/tail wind information .
Depends on the position error of the pitot static system in the
glider. Schempp-Hirth gliders typically have fairly large position
errors which cause low readings below best L/D and high readings
above. Wonderful how the performance of a glider can be improved by
moving the static source.
The Airspeed Indicator measures Indicated airspeed. For wind purposes
you need True airspeed (corrected for instrument errors, position
error and air density - we don't have to worry about Mach number here).
Headwind/tailwind component is done by taking the difference between
the GPS groundspeed and the True Airspeed so unless the TAS is
reasonably accurate the wind component will be in error.
Most glide computers have a facility for correcting the IAS for
position error. This should be done. This is not an error due to
drift with aging in the instrument.
Mike
Borgelt Instruments - manufacturers of quality soaring instruments since 1978
phone Int'l + 61 746 355784
fax Int'l + 61 746 358796
cellphone Int'l + 61 428 355784
email: mborg...@borgeltinstruments.com
website: www.borgeltinstruments.com
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