272 
Proceedings of the Koyal Society of Edinburgh. [Sess. 
The behaviour of the pendulum is set out in the following table. Time 
is counted from the instant at which the aeroplane resumed straight flight 
following upon the half turn. 
Table II.— Action of Dashpot. 
Value of Q in degrees. 
Time in minutes. 
6-25 
0 
5 
106 
4 
2T0 
3 
3-48 
2 
5-39 
I 
9-0 
1 
2 
11-9 
1 
5 
16-4 
These results are shown in fig. 9, which illustrates the vice inherent in the 
dashpot idea. Assuming that the aeroplane executes the half turn in J of 
a minute, we see that in that 
time an error of 6*25 degrees 
is introduced and that it takes 
the pendulum 16*5 minutes to 
recover to within J of a degree. 
Under the conditions which 
prevail on aircraft, gyroscopic 
pendulums which depend for 
their action on gravity con- 
trol and dashpots are of little 
or no use ; under such condi- 
tions these devices leave the 
vertical quicJdy and return 
very slowly ; they leave the 
true vertical luith ease and 
return with difficulty. 
A gyroscopic pendulum of 
the type described, in which 
the erecting action depends on the existence of processional motion, when 
supported on a steady platform at rest, is subject to an error due to the 
rotation of the earth. The resting position of the device is one in which 
the pivoted system is inclined to the vertical at an angle such that the 
couple which results from the tilt causes the pendulum to process with the 
to 
Time in Minutes. 
Fig. 9. 
