Wills Wing Alpha 180, Owner'S Service Manual

Page: 26 / 55

— 20 —
The design of the Hall type airspeed indicator involves using a ram air versus static
pressure differential to raise a disc in a tapered tube against the force of the weight of the
disc. Because of this, the ASI has the following operating limitations:
a. It is only accurate in one G flight. If you are turning at a bank angle of more than 30
degrees, the ASI will read artificially low as a result of the G loading of the turn. Reliance
on the ASI for limiting airspeeds in high banked sustained spiral maneuvers will likely
cause you to exceed the placarded speed limitations of the glider and will compromise
your safety.
b. It is only accurate when within 15-20 degrees of the vertical orientation.
Landing The Alpha
We recommend using an aircraft landing approach (45 entry leg, downwind leg, base leg, and final
leg) whenever possible, and we suggest that you practice making your approaches with as much
precision as possible. Under ideal conditions, landing approaches are best done so as to include a long
straight final into the wind at a speed above best L/D speed. In a very limited field, or a field which
slopes slightly downhill, when landing in light wind, you may need to make your final approach at a
slower speed, perhaps as slow as minimum sink, in order to be able to land within the field. In winds
of less than 5 mph, if the slope is steeper than 10:1, you should seriously consider landing down-
wind, uphill; or crosswind, across the slope. Landing attempts which require slow speed approaches,
maneuvering around obstacles or into a restricted area, or downwind or crosswind landings are not
recommended for pilots below an advanced skill level.
Standard Aircraft Approach Pattern
Entry Leg
Downwind Leg
Base
Final
The best way to avoid roll / yaw oscillations on approach is to fly your entire approach at a constant
airspeed, and to control your touchdown point by making adjustments to the shape of your pattern.
In particular, we recommend against the technique of make a diving turn onto final. This maneuver,
sometimes called a “slipping turn” is often taught to student hang glider pilots as a way to lose alti-
tude during the approach. While it will work reasonably well with low or medium performance low
aspect ratio gliders which have high levels of yaw stability and damping, and which are able to lose
energy by diving because of the large increase in drag at higher speeds, on a high performance glider
this technique serves only to convert the energy of altitude to energy of speed, while at the same time
suddenly increasing the glider’s sensitivity to control inputs. The result is a high probability of over-
shooting the intended landing point and the prospect of roll / yaw oscillations which may interfere