1921-22. j Gryroscope and “Vertical” Problem on Aircraft. 279 
through the angle ifj the aeroplane is supposed to fly in a straight path. 
The times given in the fifth column of the table are those which elapse, 
in each case, before the pivoted system is upright. 
Table IV. — Performance op Early Form of Gray Stabiliser when mounted 
ON AN Aeroplane executing- a Turning Movement. 
Angle turned 
through by 
Aeroplane (i//), 
in degrees. 
Total Deviation 
of Stabiliser 
from Vertical (0), 
in degrees. 
Error in 
Range (0d, 
in degrees. 
Error in 
Line (e^), 
in degrees. 
Time required for 
Correction of existing 
Error on resumption 
of Straight Flying, 
in seconds. 
30 
0-15 
0-04 
0T4 
3-3 
45 
0-22 
0-07 
0-21 
4-8 
60 
0-29 
0-14 
0-25 
6-3 
90 
0-41 
0-29 
0-29 
8-9 
135 
0-52 
0-50 
0-21 
11*3 
180 
0-58 
0-58 
0 
12*6 
225 
0-52 
0-50 
-0-21 
11-3 
270 
0-41 
0-29 
-0-29 
8-9 
315 
0-22 
0*07 
-0-21 
4-8 
360 
0 
0 
0 
0 
If we suppose that a bombsight forms part of the pivoted system, 6-^^ 
gives the error in range, and 0.^ the error in line, after the aeroplane has 
turned through the angle ip. When ijj is 90° — that is, after a quarter turn — 
the errors are equal and amount to of a degree ; the time required for 
correction is 9 seconds. After a half turn (the most important case) there 
is no error in line, and the error in range amounts to f of a degree. As 
the line bars, or the equivalent, are in a truly vertical plane immediately 
following upon the half turn, and remain in a truly vertical plane (the 
correction of the range error takes place wholly about the pivots PiPi), no 
error is introduced in the approach to the target. The error in range is 
corrected long before the ‘‘ range ” bars are required. 
We have seen that if a gyroscopic pendulum, provided with gravity 
control, is mounted on an aeroplane, the deflection from the true vertical 
following on a half turn is 47rf/^T, where v is the speed of the aeroplane 
and T the periodic time of the pendulum for steady precessional motion. 
If is 100 feet per second, and the deflection is not to exceed 0 58 degree, 
the periodic time must be upwards of an hour. The length of a simple 
pendulum which would have this period is about 2000 miles. 
In fig. 12 is shown diagrarnmatically a form of Gray stabiliser which 
was used in carrying out early experiments in the air at the KN.A.S. 
Experimental Aerodrome at Grain. A gyroscope g is pivoted at 
