Flytec 6030 * - Manual (Page 48)

Flytec 6030-GPS
48 / 62
For the calculation of wind, arrival altitude or arrival time at goal, however the true air speed
values are always required. The wind wheel sensor shows the true air speed (=TAS),
because it runs practically without friction.
The FLYTEC 6030 GPS shall, thanks to modern processor technology, always use both
speed indicators side by side regardless of which speed input is used. Nevertheless, the pilot
can also set the type of speed he prefers to view on the display. However, he shouldn’t be
surprised if he sets for ex. the display as IAS, that at high altitude and calm air, the difference
Groundspeed – Airspeed is shown correctly as zero, although the ground speed provided by
the GPS will be much higher than the indicated air speed.
9.3.2 Stall
Alarm
If a pilot slows down his glider gradually, he will cause a stall when falling below a certain
speed, which will have different consequences, depending on the type of aircraft.
If the air current is suddenly cut-off from the entire surface, then a completely unforeseeable
crash would be pre-assigned. For this reason, our wing manufacturers are building a
so-called cross-setting (washout) into the support parts of the wings; this means that during
flight the wing tips will always have a smaller stalling angle than the middle part of the glider.
If the air flow stalls in the middle part of the surface when falling below a minimum speed,
then lift still remains on the wing tips. The aircraft is now in stall flight.
Due to the fact that the wing tips are positioned behind the aircraft’s centre of gravity,
the aircraft will drop nose downwards and try to increase the air current by gaining speed.
It is certainly not advisable to stay a longer time span in this excessive flight situation, as the
wing will react extremely sensitive to even small air turbulences. A stall can be dangerous,
especially during the landing approach. The consequence could result in a stall over one
surface or an incipient spin. The stall alarm is a loud, concise acoustic signal that requests
the pilot to fly faster. It assists first and foremost hang gliders, however para gliders to a
lesser extent. Anyone who has ever watched a hang glider come in during an approach
can observe the following situation:
always when a good headwind prevails, many pilots will pull out their steering bar too early;
the glider then climbs a few more meters to end up in a favourable case afterwards with its
keel stuck in the ground. With no wind or with a light tail wind most pilots wait too long
to pull out the bar. In this case, and with luck the result will only be a belly landing; but also
a ground-loop with broken base side tubes may be the result, or the glider’s nose absorbs
the impact when touching ground and the pilot will swing pendulum wise, hitting his helmet
on the front keel tube.
There are different stall speeds to apply for each glider and varying weights of the pilots.
Several tests are necessary to determine for the own arrangement the setting of correct
stall alarm limit in the Set-up Menu. Furthermore it is worth to note that close to the ground,
and because of the air cushion under the wings, the stall occurs at approx. 2 km/h lower
speed than in the high air. In regard to self-flown gliders the correct setting was always
between 30 and 34 km/h. In addition, the stall speed is dependent on the specific weight
of the air, i.e. the flight altitude. On the FLYTEC 6030 GPS the stall alarm level is
automatically
raised with increasing flight altitude, corresponding precisely to Indicated Airspeed. It is
unimportant if the pilot has selected True- or Indicated Airspeed for the speed display screen.
The distance to stall speed is now easily monitored on the Speed-Analogue scale.
The border limit between stall alarm and the speed for minimal sink is indeed very small.
Hence several pilots have complained about the fact that while circling up in weak thermals
at the speed of minimal sink, the stall alarm is triggered sometimes. In this regard there is
an altitude limit to be adjusted in Set-up menu by the pilot above which the stall alarm shall
not be initiated. Of course, in this case, the landing areas should be located below this limit.