Some excerpts taken from the book:
Gyroscopic Instruments
CHAPTER 3
DIRECTIONAL GYRO INDICATOR (DGI)
In general, there are two ways of finding the aircraft heading by the DR reference, namely: the magnetic compass and the DGI. The earliest form of the DGI was in China [2]. The Chinese employed a statue, mounted on a land carriage, as a heading reference. The carriage was fitted with a differential- gear axle to stabilize the statue in the South-North alignment.
This assembly then enabled the people to explore the featureless Chinese desert without getting lost.
In order to work as a DR heading reference, the present model of the DGI (fig. 3.1) uses gimbals (fig. 2.1) for stability. The outer gimbal axis is mounted vertically (Table 2.1) for gyro compassing.
The DGI is only a recent flight system product. The earlier form of heading reference is the magnetic compass and,
Question 1
The latitude controller of a remote reading compass system corrects for drift due to Earth rotation, without affecting random drift of the gyro itself.
On the ground at London (51 10 N, 00 10 W) with the latitude controller set for 45 N, the gyro readings are observed to decrease at a rate of 4 /hr.
a.What is the hourly random drift rate?
Later the aircraft leaves London for a six- hour flight to New York (40 40 N, 73 46 W) on the direct rhumb line track. The gyro indicator is set to the required true heading on departure, but heading is subsequently maintained without reference to this instrument.
Assuming that the latitude controller setting is unaltered and that the drift rate found in (a) is due to random drift, and remains unchanged:
b.Determine whether the gyro indicator reading on arrival at New York will be greater or less than true heading and calculate the approximate value of the difference.
A.T.P.L. [10]