As the machine passed out of sight of land at 3.35 p.m., about ten minutes from the start, the signalman at the marine lookout on the hills above St. Johns reported that it was flying in a north-easterly direction.
When the start was made at Mount Pearl the weather was perfect, at any rate locally, although a fog-bank at sea was visible. There was a light north-westerly wind and a cloudless sky locally. The conditions were described by Harry as “not yet favourable, but possible.”
The machine climbed very well, and after about ten minutes, when it passed out of sight of land, Harry encountered the thick fog of the Newfoundland Banks. Fortunately they had no difficulty in climbing above this, although naturally they lost sight of the sea, a circumstance which was, if anything, a little disconcerting. Above them the sky was clear. Grieve just managed to get one drift reading before they passed out of sight of the breaking waves.
For the first four hours after leaving St. Johns the clouds and fog above which they passed were level-topped like a sea and gave a perfect horizon for the celestial observations on which Grieve’s navigation depended.
The following account of the process of navigating the machine was given to The Daily Mail before the start by Grieve:
“Navigation of aircraft across the Atlantic must necessarily be of the rough and ready type, but as it is of vital necessity to ensure success every means must be taken of finding one’s position and making most use of the air currents met with.
“Of course the machine might get across by steering a compass course, allowing for the various winds, supplied from the limited knowledge of the meteorologists. But few reports of the surface winds are available, leaving large spaces on the chart of the weather in which conditions can only be guessed, while the upper air currents are absolutely unknown.
“Should the navigator allow for a beam wind of 30 miles an hour when the opposite exists he will be 60 miles out of his reckoning at the end of one hour, and soon altogether out of the weather system he is expecting on the direct route.
“The only method of checking positions and finding the course and speed made good over the sea is by astronomical observations and obtaining the positions by wireless from ships en route. In the latter case the ships keep regular narrow lanes and may not be met with, as it would be virtually impossible to keep in their track, and unless one should pass over them and be seen by them their positions would be valueless.
“My intention is to rely chiefly on astronomical positions which I shall obtain by sextant and work out by a diagram invented by my instructor, Commander Baker. The altitude of the sun, taken about every hour, will give me a line of position at the time of the observation. When the sun is on the prime vertical the line of position will be the longitude; when on the meridian the latitude. At other times two observations at a good interval, with the run in that time, will give me a position. To obtain this run the ‘drift’ must be known, and I hope to get this by dropping smoke-bombs by day and light-bombs by night and observing the true path of the machine past them through the ‘drift’ indicator.