Flytec 4030 * - Manual (Page 22)

Flytec
Polars for the best glide in still and agitated air
With a 20 km/h head wind, the polars are displa-
ced by 20 km/h to the left. In order not to have to
displace the polars, the origin of the co-ordinates
in respect of the polars can also be displaced by
20 km/h to the right (blue co-ordinate system).
The tangent from the new origin to the polar now
touches it at the point at which V
H
= 40 km/h and
V
VE
= -1.21 m/s. In other words for optimum glide,
flight speed must be higher with a head wind than
without a head wind.
If there was a following wind of 20 km/h, the ori-
gin of the co-ordinate system in respect of the
polars would be displaced by 20 km/h to the left.
If you also find yourself in a descending mass of
air, the descent of the air must be included in the
resultant overall descent and the polars should be
displaced downwards by the relevant amount.
Once again, the origin of the co-ordinates is dis-
placed upwards and the tangent for the best glide
is laid from there to the polar.
If, in our example, the 20 km/h head wind is accompanied by a descending mass of air of -1
m/s, the best glide is V
H
= 46.2 km/h and V
VE
= -1.75 m/s. The instrument would display an
overall descent of V
Si
= V
VE
+ V
VL
= -2.75 m/s.
Optimum cruising speed
Cruising speed in a mass of air that is not horizontally
agitated can be calculated as follows:
V
R =
V
H .
V
St
: Speed of ascent while circling in a thermal
V
Si
: Overall descent in straight-line flight
The formula for the cruising speed can be graphically
integrated into the depiction of the polars as shown in
the illustration “Optimized desired flight”.
Thus for our sample polar in descending air
(-1 m/s), with ascending thermals of 1 m/s, the fastest
flying speed would be V
R
= 25.3 km/h at V
H
= 43 km/h
and an own descent V
VE
= - 1.4 m/s.
Operating Instructions FLYTEC 4030 21
Si
V = -2.4 m/s
1
-1
-2
-3
-4
-5
-6
-7
10 20 30 40 50
V
Si
( m/s)
( km/h)
H
V
-1.97
-2.4 optimum H
V = 43 km/h
43
V E
V =
-1.4 m/s
St
V =
1 m/s
V
R max
V
R
13 km/h
10.5 km/h
V L
V =
-1 m/s
Illustration: Optimized desired flight
V St
V St - V
Si
4
3
2
1
-1.05-0.97 -1.1
-1.21
-2.17
-3.75
-4.85
-1
-2
-3
-4
-5
-6
-7
10 20 30 40 50 60 70
V
V E
( m/s)
( km/h)
H
V
4
3
2 1
V
V E
( m/s)
V
W
= -20 km/h
Illustration: polar with and without a head wind