Fig. 9 
Diagram for the determination of the flying time for the "S" turn. 
off-course displacement can be safely and ac 
curately corrected without further ground 
observation before reaching the territory to 
be surveyed. 
The flying of turns and in particular pre 
vious computations could be greatly simpli 
fied if new designs of automatic pilot systems 
would be provided with a variable control of 
the turning speeds instead of three stages. 
b) Turning with Wind. 
with reference to each other in the direction 
of the line of flight by (1 1 + t 2 ) . v wx . 
If there is a cross wind blowing at right 
angles to the line of flight, the airplane be 
headed off-course by crab angles /?1 and /fo 
already on the straight run. The airplane will 
therefore not only have to turn by 180° but 
rather by 180° + (/?i + fo), depending on 
whether the airplane is heading into or fly 
ing before the wind when making the turn. 
The flight line spacing Will then change ac 
cordingly by 
Let us first discuss the case when the wind 
is blowing exactly in, or opposite to, the di 
rection of the line of flight. It is therefore ob 
vious that a turn which has been previously 
computed on the basis of the air speed of the 
ship (not the ground speed) according to Dia 
gram 6 or 7 and which is subsequently flown, 
will be either elongated or compressed in 
comparison with the “standard turn without 
wind“. In any case, the flight line spacing 
will be correct. When negotiating a turn, the 
ground speed changes from ( v e + v wx ) to 
(v e - v wx ) ; its mean value is equal to air 
speed v e . The ends A and C are displaced 
[ti + t2 + (Ti + /?2)I • v wy , 
where v wy is the velocity of the cross 
wind, and p 1 and ft2 — converted in time of 
flight — are added to the values of the j^dj 
turning speeds. It is therefore necessary to in 
troduce again in Diagrams 6 or 7 a value of 
, , . , . • • , ireduced } 
s which, in comparison with s, is < . < > 
r l increased) 
by the amount of wind displacement. Hence, 
a new value of s will be ascertained by suc 
cessive interpolation, so that after making 
allowance for wind displacement, the result 
10