RAF issue Aircraft Clock, 6A/5184
Introduction
1. The elapsed time clock (Ref. No. 6A/5184) provides an accurate time datum when flying on a Q.D.R., thus enabling the various stages of a let-down to be accurately timed, or for a given rate of turn to be maintained for a predetermined time.
2. The elapsed time clock is complementary to the time of flight clock (Ref. No. 6A/5183). The two clocks constitute a set.
DESCRIPTION
3. The clock is of the 36-hour type, having a movement incorporating 16 jewels and a Breguet overcoil hairspring.
4. The outer dial is graduated into 60 seconds, corresponding to one revolution of the large hand. The inner dial is graduated into 12 minutes, corresponding to one revolution of the small hand. All figures, markings and hands are white against a matt black background.
5. The movement is mounted in a small (2.25) S.A.E. case with 4 B.A. stiff nuts integral with the case. The back of the case is fitted with a corrosion inhibitor.
OPERATION
6. The clock is wound by the winding button situated at 4 o'clock. A friction overwind device incorporated in the button ensures that the mainspring or the winding mechanism cannot be damaged by overwinding.
7. The clock is stopped or started by depressing the winding button. The first pressure starts the clock, the second pressure will stop it.
8. Both hands are set to zero by depressing the reset button situated
at 6 o'clock.
Note. . .
If the clock is restarted after being stopped
before the hands are returned to zero, the clock will record the elapsed time
from the stopped position.
9. The clock can be started at any time during flight and allowed to run. When a marker beacon is identified, the reset button is depressed, causing the hands to return to zero and restart instantaneously, thus recording the elapsed time from zero.
INSTALLATION
11. The clock is secured to the instrument panel by three 4 B.A. screws on a P.C.D. of 2.625 in.