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Aviation History
1941
1941 - 1073.PDF
MAY 8TH, 1941. 331- LEAR GYROMATIC NAVIGATOR Directional Gyro and Radio D.F. Indications Given on One Diat THE gyroscope, by its ability to define a constantdirection in space, has done much towards solvingthe problem of navigation in bad weather. So also has radio direction-finding, and the principle of rotating a "loop aerial until the signal strength is a minimum and tKereby determining the direction of the station transmit- ting is very well known to all pilots and navigators. To "have the direction of the station indicated automatically and continuously by a pointer on a dial without the neces- sity of manually rotating the loop is a convenience, but to have the reading of the directional gyro added to the same dial is an additional help to the navigator which can do much to ease his mental stiain in times of difficult flying conditions. Such an instrument is the Lear Gyromatic Navigator, invented by 38-year-old William P. Lear, head of the American radio firm of Lear Avia at Dayton, Ohio. The dial of the instrument is shown in the illustration and the pointer is governed by a radio direction-finding set so that it continues to point towards the station to whose wavelength it is tuned. • There is no necessity for this to be a beam or a D.F. station, even a broadcasting station will do The double line is etched on a lightweight transparent disc above the pointer and is controlled by the directional gyro housed in the base of the instrument. This double line can be set to any desired direction and will remain in that direction irrespective of the manoeuvres of the aeroplane The miniature aeroplane seen is etched into the glass cover of the dial, this being a fixture relative to the instru- ment and therefore to the aeroplane. So the miniature is merely a reminder to the pilot of the direction in which his The ndications given bythe Lear Gyromatic Navi- gator in an approach toan aerodrome under con- ditions of bad visibilityare shown in this diagram. aeroplane is pointing ; it helps him to visualise the relations between his aeroplane and the radio station being used or the aerodrome being approached. The remaining feature on the dial is the card over which the other elements are mounted This card is graduated into 360 degrees and can be rotated and set as desired by means of the knob at the base of the dial. Approach Procedure The other illustration shows the indications given by the Lear Gyromatic Navigator in an instrument approach to an aerodrome which has a radio transmitting station on the line of direction ol the runway to be used in bad weather. The dotted line shows the flight path of the aeroplane in the approach and subsequent landing. The circles on this path show the indications given by the gyro- matic navigator at these various stages of the approach. At position 1 the aeroplane is homing towards the radio Station and the pointei points to zero of the scale (assuming that the scale has been set so that its zero lies on the fore- and-aft line of the aeroplane). The discerning reader will say, What about drift? If there is any, the pointer will move from the zero as the aeroplane is drifted ; the pilot then applies rudder to bring the zero under the pointer and so is sure that his aeroplane is again pointing towards its destination. This process continued will bring the aero- plane over the radio station, though its path will not be The four elements of the dial are :—1. The card which can berotated and set by the knob at the base. 2. The pointer controlled by the radio D.F. set. 3. The double line indicatorof the directional gyro, and 4. The miniature aeroplane etched on the fixed glass cover.
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