Air voyages in the 1940s were generally much shorter than sea voyages, seldom lasting longer than 10 hours, and the navigator could not rely on his celestial observations to give him position lines much better than 8 or 10 miles from the correct position, unimportant when making landfall from the air, but important at sea.
A 4 second error in time leads at the equator to an error in position east or west of one nautical mile and less as the latitude increases.
The regulator screw has two slots at right angles and is rather difficult to access with a screwdriver, as the centre seconds bridge gets in the way of aligning the ‘driver square with the screw-head. The origin of the term “hack” in this context seems to be obscure.
The makers specification required that the average daily rate should not exceed 5 seconds and that the average of the daily deviations from the average daily rate should not exceed two seconds, rather poorer than for a marine chronometer in good condition.In the original outer cases, the watch lay in a pocket suspended by foam rubber pads and when the lid was closed a further pocket suspended on foam rubber lay over the watch so that it was prevented from moving between the pockets while being isolated from shocks.The case illustrated is made from African mahogany and the pockets are suspended on springs, which have the merit of not perishing like rubber, while being susceptible to corrosion.Prior to their friendly outing, they were seen together nearly halfway across the world at the Formula One Grand Prix on May 24 in Monaco, where Kendall, along with gal-pals Bella and Gigi Hadid, Kylie Jenner and Hailey Baldwin cheered him on."You're #1 in our book...every other book ever @lewishamilton," Bella captioned a shot on Instagram. Like the Hamilton M22, this is not strictly a chronometer, in that it does not have a chronometer escapement and other features associated with mechanical chronometers.Rather, it is a high quality lever escapement watch with some special features, adapted mainly to the needs of the aviator and the requirement to manufacture many tens of thousands to meet war-time demands.