Gyro Instruments.pdf 22273p

BAK – Gyro Instruments GYRO INSTRUMENTS Background -Gyros have 2 important properties for us -Rigidity : a spinning gyro tends to maintain the orientation of its axis of rotation -suitable bearings and gimbals can allow a gyro to maintain its orientation; a “space gyro” -Precession : a force applied to a spinning gyro will act as though displaced 90 degs further around in the direction of rotation -Aircraft gyros make use of both of these properties HOW DO WE GET A GYRO TO SPIN? -Air or vacuum driven gyros -older aircraft had an external venturi tube

-These days vacuum instruments are usually supplied by an engine driven vacuum pump

HOW DO WE KNOW IF THE VACUUM PUMP IS WORKING -We can look at the vacuum guage..

-Another modern trend is to have the turn coordinator electric and not vacuum -this is primarily for safety so loss of either vacuum or electrics wont disable ALL gyro flight instruments -So lets have a look at the TURN COORDINATOR…. both kinds… -uses precession - the vacuum instrument has the typical arrangement of buckets which catch the air stream

-the electric one uses a DC motor, powered by the aircraft electrical system, to spin the gyro -failure of vacuum indicated on vacuum guage -failure of electricity supply indicated by red flag on instrument facia

INDICATIONS… -balanced turn

This shows a rate one turn right, with no slip or skid

-slipping turn

This shows a rate one turn right, with a slip right -skidding turn

This shows a rate one turn right, while skidding left THE DIRECTIONAL GYRO -uses rigidity -allows us to have a stable heading reference -on smaller aircraft is commonly set by the pilot to runway bearing before takeoff -it has no inherent ability to seek magnetic north -manual corrections to the com heading must be made regularly… about every 15 minutes -larger aircraft have the DG “slaved” to a com direction transmitter -and only require periodic checking against the com -looks like this:

ATTITUDE INDICATOR or ARTIFICIAL HORIZON -Uses rigidity in pitch and roll planes -Uses precession to maintain its correctness -May “topple” if maximum bank or pitch is exceeded -more sophisticated aircraft have full space movement gyros and wont topple -once toppled may require several minutes to regain correct state -Has adjustment to vary position of aircraft in pitch -Reads as shown below: