FES Discus 2c - Performance Characteristics; Airspeed, Stall, and Take-off Performance

FES Flight Manual, v1.18 May 2020
Page 26 of 35
5. Performance
5.1 Introduction
This chapter provides data for airspeed calibration, stall speeds and take-off
performance and some further information. The data in the charts have been computed
from actual flight tests with the sailplane in good condition using standard piloting
techniques.
5.2 Approved data
5.2.1 Airspeed indicator system calibration
The airspeed indicator must be connected to the pitot pressure source located on the
vertical stabilizer and to the static pressure source located on the aft part of the fuselage
(detailed location of ports depends on specific glider type).
5.2.2 Stall speeds
As described in the manual of the pure glider version of the sailplane, but keep in
mind that your FES equipped glider has a higher wing loading, and as a result, higher stall
speed.
5.2.3 Take-off performance (only for self-launch approved types of sailplanes)
The take-off performance for aero tow, winch launch, or auto tow is the same as a
pure glider version. However, due to the additional weight of the FES, the sailplane has a
slightly higher wing loading, so liftoff must be performed at a higher speed.
Take-off run distance and climb performance during self-launch, primarily depend on
sailplane take-off weight, its glide performance, quality of the runway and air density
(airfield elevation, and outside temperature).
An important factor is also the temperature of the battery packs. Cold or overheated
batteries can not supply the same maximum power as batteries at optimal temperature.
Warning: Do not try to self-launch if the temperature of the battery packs is
below 5°C!
Note: Store the batteries packs at room temperature during the night and
not in a glider or trailer parked outside. Install them into the plane just
before the flight to avoid taking off with cold batteries.
Caution: Keep propeller blades clean for self-launch take-offs, as bugs
reduce propeller efficiency and thrust, resulting in a longer take-off run and
reduced climb rate!