| 摘要 |
Double-faced rule 1 intended for direct reading of aeronautical maps, on a scale of 1/500,000 3, graduated in nautical miles 2. The invention relates to a graduated double-faced rule allowing direct measurement of the time taken to cover a distance 2 in N.M. The rule 2 is made of plastic, the time graduations 4, 8 in blue, the graduations 6, 10 in red, the graduation of the N.M. 2 in black. This double-faced rule 1 is in particular intended for aeroplane pilots, allowing them direct reading of the flying time for a given indicated speed of the aircraft, depending on the distance to be covered 2. <IMAGE>
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