Steve Kroop at Flytec <<info>>
writes:

The 6030 measures airspeed via its built-in pitot sensor, in the
5030 this was an option, and in all of our models since the 3005SI, airspeed can
be measured with an external plug-in sensor. The plug in sensor will measure
1-94 mph, the pitot sensor on the 5030 can measure 19-74 mph and the pitot on
the 6030 can measure an incredibly wide range of 14-180 mph. Both the internal
sensors in the 5030/6030 and the external vane sensor are very accurate but
there are some simple things to check in the event the you feel your displayed
airspeed is not accurate.

To get an accurate reading on the 5020/6030 the pitot tube needs to point into
the relative air flow. Since on these instruments, the pitot tube extends
forward out of the top of the housing, the tube may or may not be lined up with
the airflow depending on where you place your instrument and how you orient it.
This is of particular importance on a paraglider. If your preferred placement of
the instrument is such that the tube is not inline with the airflow, there is a
simple fix. The pitot tube is polyethylene, which becomes very flexible with
heat. Gently heat the tube until it becomes pliable (blow drier on medium), bend
the tube to the desired curve/angle and then allow to cool. Of course be careful
to not kink the tube in the process.

In the case of the 6030 the pitot tube is removable. This is to allow for more
compact stowage and to allow the user to easily replace the tube when they
become mangled. The downside is that they get lost relatively easy. The good
news is that there is nothing special about the tube. You can use anything that
fits in snuggly (in a pinch you can use a drink straw). Most hardware stores and
home centers (e.g., Lowes, Home Depot) sell 1/4" polyethylene tubing that is
used to run water to refrigerator ice-makers. This tubing is very inexpensive
and is an ideal replacement. It is slightly larger in diameter than the factory
tube which yields a tighter fit.

In the case of the 5030 the pitot tube is not removable. If you pull on it, it
will detach from the internal flexible tube and come out of the housing. Pushing
it back in the housing will do nothing and the unit will need to be disassembled
so the external black tube can be reconnected to the internal flexible tube.
This is not particularly difficult to do but if you pulled out the pitot tube I
recommend that you send the unit to us to reconnect the pitot and we can do an
inspection/firmware upgrade while we have it. I have noticed on 5030s that have
come in for service, that the pitot tube has been pushed into the housing. I do
not know if pilots are doing this deliberately or inadvertently (packing up
and/or wacking) but whatever the reason, pushing in the black tube can kink the
internal tube and cause the airspeed reading to be low. If you are experiencing
this, pull out the black tube but only with minimal force so you do not
disconnect it from the internal tube as discussed above. Also, rotating the
black tube can kink the internal tube and should be avoided. If your airspeed
reading is reading low or 0 you can try turning the tube 1/8 turn
clockwise/counter-clockwise to see if the tube un-kinks and the airspeed reading
returns to normal. Do not turn the tube more than a total of a 1/2 turn in
either direction.

The external vane sensors are very accurate and capable of reading as low as 1
mph. The key to the accuracy and sensitivity of this sensor is the very low mass
of the impeller and the jewel bearings that the impeller axel sit in. Things
that can reduce the accuracy of this sensor are loose fit of the axel in the
bearings, bent impeller blades and dirt/debris fowling the jewel bearings. Loose
fit is generally caused by extensive use (the jewel/axel is worn down) and bent
impeller blades are caused by an object entering the impeller aperture. In
either case, send the sensor in for service. In some cases the bearings can be
adjusted or the blades can be bent back into position but usually the impeller
assembly needs to be replaced. If the inaccuracy is caused by dirt/debris on the
axel/bearings you will be able to tell by looking in the impeller aperture and
observing if the impeller turns absolutely freely (i.e., the impeller should
stay near stationary if the sensor is rotated about the axel). If this is not
the case then there is dirt/debris. In most cases the debris is a strand of very
five fiber that has wound up around the axel at the bearing. In order to remove
the fiber the impeller must be slid out of the sensor. If you are good at
working on small delicate things you can do this yourself, otherwise, send it to
us. The impeller is removed by pressing on the impeller ring (be careful to not
touch the blades as they bend very easy). Examine the impeller axel at the
bearing under an illuminated magnifying glass. Use precision tweezers a needle
and the very sharp point of an Exacto blade to loosen and unwind the fiber. Once
the impeller is turning freely again, push the impeller assembly back into the
sensor, again being careful to not touch the blades.