Flight Manual for Gas Balloons of Type NL-STU
Issue 2.0
July 25, 2016
Page 4-15
NOTE:
Quantity of ballast to be dropped in order to change altitude: if one percent of the
mass of the balloon is dropped, the balloon rises from its equilibrium position
(neutral buoyancy position) by 80 m.
EXAMPLE:
A 1000 m³ hydrogen-filled gas balloon has a lifting capacity of around 1140 kg. If
the balloon is to rise 250 m, 250 m/80 m = 3.125 times as much ballast must be
dropped. This corresponds to a lifting capacity of 3.125 x 1140 kg/100 = 35.6 kg.
It is thus necessary to drop slightly more than two bags of ballast, each weighing
15 kg, to cause the balloon to rise 250 m.
NOTE:
In order to bring on board safely the sand bags that are carried outside the bas-
ket, they must be secured against falling by means of a rope that is firmly tied in-
side the basket. A safety rope that performs this function may be obtained from
the balloon manufacturer.
4.11 Landing
The landing is one of the most difficult tasks during a balloon flight. It must therefore be
planned, prepared and executed with foresight.
The following points must be checked before landing:
• Has the instruction to passengers on how to behave during landing been repeated?
• Have all unnecessary instruments and baggage been stowed safely in the basket
bags?
• Has the bench been put away and the basket flap closed?
• Have all sand bags been fastened in the basket in the direction of flight and secured to
prevent them from coming loose?
• Have all outboard fixed sand bags been secured to prevent them from commute and
flipping over?
• Is the parachute line accessible at all times?
• Have the appendix anchor lines been pulled tight?
• What are the wind speed and wind direction on the ground?
• Is the landing site sufficiently large?
• Are there any obstacles that need to be taken into account in the direction of flight
(e.g. overhead power lines, electric fences, etc.)?
• For the use of the fabric walled basket: Is the flap in the sidewall of the basket retract-
ed?
Descent is initiated by pulling slightly on the parachute or using a natural drop in altitude. The
rate of descent must be checked on the variometer and by looking outside. Equilibrium of the
balloon is recovered above the ground by dropping ballast. The braking ballast required for re-
covering the equilibrium of a 1000 m³ balloon is calculated using the following rule of thumb:
rate of descent in m/s squared times the drag coefficient of the balloon size.
