9 
to the next higher speed in the middle section 
and return at the previous turning speed on 
the last leg of the turn. The different air 
speeds developed by the type of airplane em 
ployed permit to compute bundles of curves 
according to the above formulas from which 
the flying times for the various segments for 
certain flight line spacings can be read in 
stantly and conveniently (Fig. 6 and 7). These 
will then be clocked with the stop watch. 
If flight line spacings should become ne 
cessary which exceed the possible maximum 
values for s according to Diagram 6 or which 
remain under the minimum values of s, an 
intermediate straight run B—C must be pro 
vided in one case, as shown by Fig. 8a. In the 
other case, that is Fig. 8b, the end of the line 
of flight must be displaced parallel to itself 
by including an “S“ turn A’—B’ before going 
into the final turn, so that the latter can then 
be flown with only one turning speed. 
It will be practical to fly the “S“ turn illu 
strated in Fig. 8b with the speed of 2 n . The 
illustration permits to read: 
a == 2r 2 o (1 — cos<%2°) ® 
a v ■ q 
cos a 2 0 = 1 - —, where r 2 o = y- . . ® 
Ot 20 
t 2° = T 
(must be flown as a right turn and then 
as a left turn or vice versa) 
For the ordinary flying speeds, these rela 
tionships may be represented in diagramme- 
tric form (Fig. 9), so that no computations 
have to be performed during the flight. 
Fig. 8 a Fig. 8b 
Extreme flight line spacings with intermediate run B-C or "S" turn A'-B'. 
In the case of Fig. 8a the minimum turn 
ing speed l°/sec. will be chosen for the quar 
ter-circles A—B and C—D of the turn, thus 
obtaining a flying time of 90 seconds for each 
quarter-circle. Diagram 6 permits to read the 
corresponding maximum value of s for t/ 0 = 
180 seconds and speed v. The flying time for 
the intermediate run is derived from the re 
lation 
Required spacing — si max 
t B—C ^ “ v 
The parallel displacement of the line of 
flight assumes increased importance when 
starting for the first run of a photoflight. The 
approach of a guide point selected exactly in 
the extension of the direction of the first run, 
about 6—8 minutes of flying time before 
reaching the territory to be photographed, 
rarely succeeds at the first attempt. The Lotfe 
permits to read the off-course displacement 
in km on a scale by sighting vertically down 
ward. By including a corresponding “S“ turn 
according to Diagram 9, the observed lateral