Atitude indicator

Question 1

atitude indicator AI

Answer 1

indicates pitch and roll
uses vertically tied gyro(provides horizontal datum)
display card with a pitch scale connected to an arm pivoted at rear of gimbal
2 degrees of freedom- 2 gimbals

Question 2

AI display

Answer 2

gyro and gimbal system mounted inside instrument case
display shows aircraft attitude relative to gyro- requires accurate display for narrow range of small pitch angles
symbol represents plane from behind
card coloured brown and blue attached to gyro unit- free to hold its position in inertial space

Question 3

AI pitch angle amplification

Answer 3

small pin and arm used to exaggerate movement of pitch that the aircraft makes
pitch and roll numbers correct but movement exaggerated

Question 4

AI sky & ground pointer

Answer 4

shows roll in degrees
sky pointer- marks on top
ground pointer- marks will be on bottom
both easy to interpret but going from one to other may cause confusion

Question 5

AI pneumatic gyro erection

Answer 5

pendulous veins
when level 4 holes open
when displaced some holes covered and opposite open
causes movement which reverts it back to vertical
corrects for topple caused by ER & TW

slow rate of precession

Question 6

AI electrical gyro erection

Answer 6

two torque motors one on roll axis one on pitch axis
forces applied precessed 90°
realign in roll requires torque applied about pitch axis

uses mercury tilt switches to provide signals to torque motors

Question 7

mercury tilt switches

Answer 7

when vertical mercury in middle and no signals
when tilted mercury bridges gap between connectors and provide power to torque motors
2 switches one on outer and one on inner gimbal
large acceleration- goes so far loses contact with central power- torque motors disabled
small manoeuvres- may roll and make contact even if not toppled, causes gyro to erect false vertical

Question 8

AI electrical fast erect

Answer 8

2 extra connectors at end of tubes connect to button and high voltage supply
pressing button connects supply and erects gyro rapidly
used on ground or S&L unaccelerated flight
only pressed as required as can cause damage

Question 9

AI instrument errors

Answer 9

AI errors complex because an manoeuvre causing heading change will cause gyro misalignment
turning introduces errors in alignment

Question 10

pendulous errors

Answer 10

pneumatically driven AI vulnerable to any horizontal plane acceleration
lateral acceleration- pitch error
linear acceleration- roll error

Question 11

AI erection errors

Answer 11

pendulous vanes suffer horizontal acceleration errors and deflect from true vertical because of unbalanced jets

Question 12

Pneumatically driven AI turning errors

Answer 12

‘pitch angle overeads’ means more +ve
errors reduced by having gyro mounted slightly off vertical inside casing
tilting forward reduces erection error
tilting left corrects pendulous error
only correct for particular combination of turn rate and TAS

Question 13

Pneumatically driven AI acceleration errors

Answer 13

for anticlockwise AI
acceleration causes indication of pitch up roll right
deceleration causes indication of pitch down roll left

Question 14

electrically driven AI errors

Answer 14

errors relatively insignificant 
gentle accelerations(or gradual turns) can cause erection errors 
in gentle manoeuvre:
acceleration can indicate pitch up 
deceleration can indicate pitch down
turning- under indication of bank

Question 15

AI limits

Answer 15

pneumatic: pitch 60°, rol 110°
electric: pitch 85°, roll unlimited

Question 16

vertical gyro unit

Answer 16

more complex vertical gyro whose orientation is detected electronically
attitude info used by many systems
selsyns used to read gyro unit orientation- remote atitude display on inst panel replicates gyro orientation- no gyro behind display card
vertical gyro usually stored in avionics bay