3 
It is obvious that even if adequate naviga 
tion charts should be available, such extensive 
jobs can be handled only imperfectly and in 
completely by manual or “stick“ control, if at 
all. Satisfactory results can only be obtained 
Navigation Instrnments : 
Altitudes above the ground are measured 
with electric altimeters. These instruments 
operate on the principle of the echo depth 
sounder. They irradiate electric short-wave 
impulses, catch their reflections from the 
ground and indicate the interval optically on 
by accurately controlled instrument flying 
with the aid of gyro-supported automatic 
pilot systems. Before dealing with navigation 
itself, the . available instruments and their 
applications will be briefly described: 
noted, however, that the measured air surge 
depends not only on the speed of the airplane 
but also on the density of the air. The air 
speed indicators which are used in Germany 
are therefore compensated according to the 
“standard atmosphere“ 1 ). Variations of the 
Regler für ^ 
Impulslänge 
Ausziehbarer Blendschutz 
Feststellschraube 
Drehbarer Skalenring 
Knopf für Helligkeit 
u. Kreistage 
Trimmer für 
Nullpunktlage 
auf Gegenseite : 
Regler für Kreisdurchmesser 
(Ablesung 1620m) 
Nullzeichen 
(Skalennullstrich auf Unke Kante) 
Fig. 1 C. Zeiss electric altimeter 
a flight altitude dial which is calibrated in 
meters. An altimeter of this type which has 
given full satisfaction in flying practice, is the 
C. Zeiss transmitter Fu. G. 103 which indi 
cates altitudes up to 10 000 m above relatively 
level ground or above the ocean with an 
accuracy of + 15 m. 
In addition, for flying on certain definite 
levels a statoscope is required which indi 
cates differential variations of pressure. Several 
designs are available which operate in a manner 
similar to barometers, that is either with fluid 
columns (statoscope by Vaisalá) or aneroid 
capsules. Either design has an average indicat 
ing range of + 30 m varying with the flying 
height, and a reading accuracy of 1—2 m. 
The air speed of the ship which is extremely 
important for the plotting of the course, is 
read on the air speed indicator. It must be 
Fu. G. 103 with indicator dial. 
outside temperature from this “standard at 
mosphere“ must be corrected accordingly by 
means of tables or with the aid of the well- 
known navigation computers. Due to the heat 
developed by compression, the outside temper 
ature which is measured electrically, must be 
corrected according to air speed and flying 
height. (Obtainable accuracy yy 1°C.) Making 
due allowance for air density and temperature 
in the above mentioned corrections, the air 
speed of the airplane may be determined with 
an accuracy of + 1% to 2°/o. 
Automatic pilot systems which are designed 
both as two-axis and three-axis systems, 
operate as follows: After the desired course 
has been set, the rudder control system of the 
airplane is actuated over a pilot motor until 
the directional gyro and hence the longitudinal 
axis of the airplane are headed in the direction 
of the magnetic needle of the master compass. 
1 ) German Standard Specification No. DIN 5450 „Norm-Atmosphäre', Berlin 1937.