Monday, February 27, 2012

Controls and instrumentation - SYNCHRONIZING AND SYNCHROPHASING

want to read about :  Controls and instrumentation Electronic indicating systems

58. Synchronizing and synchrophasing systems are  sometimes used on turbo-propeller engined aircraft to achieve a reduction of noise during flight.
59. On a multi-engined aircraft, a synchronizing system ensures the propeller speeds are all the same. This is achieved by an electrical system that compares  speed  signals  from  engine-mounted generators.  Out-of-balance  signals,  using  one engine  as  a  master  signal,  are  automatically corrected by electrically trimming the engine speeds until all signals are equal.

60. A synchrophasing system ensures that any given blade of an engine propeller is in the same relative position as the corresponding, blade of the propeller on the master engine. This again is auto- matically achieved by very fine trimming of engine speeds resulting from phase signals from the syn- chrophasing generators.

61. On turbo-jet engines, synchronization can be achieved in a similar manner to that used for a turbo- propeller engine. On multi-spool engines, only one spool is synchronized. Manual trimming of engine or shaft speed can be done with the assistance of a synchroscope. This visually indicates, in comparison with a master engine, if the other engines are running at exactly the same speed; the normal engine speed indicator is, of course, not sufficiently sensitive to use for synchronizing.

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