Our polar flight

by Roald Amundsen; Lincoln Ellsworth

SETTING UP THE WINGS

One can also leave the wire as it is, and turn the whole instrument instead. The angle of deviation is to be read on the instrument’s base. This is the easiest way, as it allows one to get on quickly with measuring the speed. Having calculated the deviation, it is not correct to steer against the wind allowing only a corresponding number of degrees, or it will be found that there is still a deviation, though not so great as before. To correct it it would have to be measured, then some steering would have to be done, then it would have to be measured again and so on, before it could be regulated. It is, therefore, better to come to a quick and exact result by quickly taking the speed measure. This is done with the same instrument, by watching an object pass between four points of the scale, as the machine goes over it. The pilot continues to fly in a steady course during the entire observations. The navigator sets a stop clock going when an object passes the scale at an angle of 45°, and he stops the clock when the object passes zero, as it will then be centrally under the machine. The altitude above the under-lying territory is read on the altimeter, and by aid of this and the stop clock’s indications it is possible to calculate correctly the speed over the ground-distance covered. We have now got the following particulars: The speed through the air which the speedometer shows and which is called the air-speed,—the steering course through the air which we will call the air-course,—the speed over the ground which we will call the ground-speed and last the deviation’s angle. These calculations have to be worked out in conjunction with each other on a calculating machine, showing in a second what steering-course shall be adopted under the existing wind conditions, to carry the plane in the desired direction. In addition to this there is a gratis enlightenment, showing the exact direction and strength of the wind at that altitude.

MOUNTING THE WINGS

THE LAST MEETING BEFORE THE FLIGHT

The pilot announces if a new course shall be steered. If he steers according to the solar-compass, the navigator adjusts the solar-compass by turning the periscope a corresponding number of degrees.

So long as one need not fly over clouds or fog all goes well. With steadiness it is possible to control the course over the ground and steer the plane straight to the Pole by territorial navigation. During the two first hours, after we had passed Spitzbergen’s north coast, we had thick fog under us and got no drift observations. As soon as we could get these the solar-compass was corrected. We had, however, in the meantime deviated so far westwards that the indicator pointed well over to the west side of the Pole. One must pay particular attention to the fact that the solar-compass only indicates a northward direction so long as one is on the same meridian which the compass was adjusted to. If one has deviated to the side and continues to steer according to the solar-compass, one will set a course directly parallel with the meridian for which the compass was adjusted when starting. For a new adjustment of the compass, so that it points towards the Pole, one must in every case take the bearings. Both during the northward journey, and during the homeward flight, the solar-compasses were of the utmost benefit to us. Without these and depending only on the magnetic compasses we should have been very much less confident. The selection of our magnetic compasses was only settled after we had studied the various types most analytically, paying particular attention to the conditions which they would have to answer to in the Arctic Ocean.

I should like here to mention a common mistake founded on a popular idea, that the Magnetic Pole lies at the North Pole. The globe is a great magnet which has two magnetic points, a North Pole and a South Pole, and fortunately the Magnetic Poles do not lie in the same places as the geographical poles. The earth’s magnetic North Pole, which draws towards itself the compasses’ North, lies on the north coast of Canada about 70° N. and 95° W. long. In general this is called for convenience the magnetic North Pole. Its position, as is well known, was verified by Roald Amundsen during the Gjoa expedition.