504 



NATURE 



[December i6, 1920 



THE design of instruments to aid the navigation 

 of aircraft, like all other branches of aero- 

 nautics, has been greatly accelerated by the war, 



Instruments for the Navigation of Aircraft. 

 Hy G. M. B. DousoN. 



mediately becomes untrustworthy. It must be 

 remembered that in a cloud the pilot of an aero- 

 plane has no means of knowing whether he is 

 turning to right or left, 

 or flying straight. Thus 

 previously the compass 

 was used both to keep a 

 straight course and to 

 obtain the bearing of that 

 course. The gyroscopic 

 turn indicator — originally 

 ,^, due to a suggestion by 



Prof. J. B. Henderson — 

 is now available in 

 several forms, all of 

 which work well, and en- 

 able a pilot to turn and 

 straighten out again 

 while in a cloud almost 

 as easily as in clear air. 

 With the presence of this 

 instrument the compass is 

 required only for showing 

 the direction of flight 

 during the time the aero- 

 plane is flying straight. 



The gyroscopic turn in- 

 dicator depends for its 

 action on the precession 

 of a rotating gyroscope 

 against suitable control- 

 ling springs, when its axis 



Fig. I. — R. A. E. gyro turn indicator Marl: V. a, eyro wheel ; b, b, oblique holes for air-drive ; c, shaft 

 carrying gyro wheel communicating motion to pointer ; i/, cam on shaft c: ; ^, controlling spring ;J^ cam 

 altering tension of spiing f, worked by lever jf. 



though many of the in- 

 struments required are 

 only now reaching their 

 final stages of develop- 

 ment, and instruments to 

 effect navigation — as dis- 

 tinct from pilotage by the 

 aid of landmarks — were 

 scarcely used during the 

 war. 



Before and during the 

 earlier stages of the war 

 the errors of the mag- 

 netic compass as used on 

 aeroplanes were the sub- 

 ject of much discussion, 

 and numerous designs 

 were tested with the view 

 of overcoming its defects, 

 which are, unfortunately, 

 really inherent. The 

 gyroscopic turn indicator 

 has now solved this prob- 

 lem by taking over some 

 of the original duties of 

 the compass. Provided 

 the aeroplane be flying 



straight, the compass shows the direction of flight 

 correctly, but as soon as a turn is started it im- 

 NO. 2668, VOL. 106] 



fiS?Sf^ 



Fig. ?.— Gyro rudder control 



gyro wheel ; C, D, gimbal rings of gyro ; 

 outer gimbal ring to valve. 



F, G, pin and link connecting 



of rotation is changed. One simple form is shown 

 in Fig. I. The gyro wheel seen on the right is 



