Navigation Aids Flashcards
FMS (FLIGHT MANAGEMENT SYSTEM) or FMGS (flight management guidance system)
Takes the aircrafts subsystems and integrates them into one. Primary function is to aid the pilot and navigation and manage optimum performance. Consists of Flight management computer FMC Control display unit CDU Flight control unit FCU Flight management source selector Display system
Attitude heading reference system (AHRS)
Consists of three senses on each of the aircrafts three axis.
Consists of three gyros to measure angular motion, and three accelerometers to measure aircraft linear motion.
Control display unit (CDU)
The tool that flight crew use to interface with the FMC. Used by flight crew to command inputs to the FMS.
Database renewed how often?
Every 28 days
FMS principal task?
To determine the across position and the accuracy of that position. If it misuses as many senses as it can, such as VOR, DME, NDB, GPS etc.
FMC mode 1: DUAL mode
To FMC are interconnected, when pilot in this data into one CDU, it is automatically transferred to the other to sync. Although the two CDs are synced, pilot is able to select their own EHSI display.
FMC 2: Independent
When the system senses a disparity between the two cdus/fmc, each CDU will operate independently and pilots are left to identify the serviceable system.
FMC Mode 3: Single
When one FMC fails, the aircraft will operate on one FMC. FMC can power both EHSI displays.
FMC Mode 4: Backup
Navigation if both fmcs have failed, pilots are left with blank ehsi. There are standby instruments that pilots can use to achieve navigation. Tuning RMI and analog DME readouts.
Trust management computer TMC
The FMC controls the auto throttles, adjusting thrust setting to achieve desired performance. Computations are derived from the air data computer
Ring Laser Gyro
Bring laser dryer operates on a principle of relative movement between two laser beams as opposed to property of inertia. Constructed from solid glass or ceramic.
Explain RLG lock-in or frequency lock
When ring laser gyro is not rotating, or rotating very slowly.. scatter from mirrored surfaces causes opposing beams to lock together until a certain rate of rotation is reached
Overcome by reintroducing a dither we’re an external vibrating device resonates the gyro to break the frequency lock.
Rlg serviceability checks
Done as part of corporate preparation pilot flying. Alignment of IRS Must be completed on the ground prior to flight. The aircraft must be stationary.
Alignment can take up to 10 minutes and can be as fast as 30 seconds
INS/IRS difference
INS- DATA COLLATED FROM GYROSCOPES IN ACCELEROMETERS FED INTO INERTIAL NAVIGATION COMPUTER (INC)- THERE IS NO FMS.
IRS- the data is fed into FMS computer where information is processed.
INS has its own data processing computer, INC. IRS uses computer in the FMS
Strapdown and stable platform difference
Both use three gyros and three accelerometers. Stable platform uses earth as reference plane whereas strap down uses aircraft as reference plane.
Main advantage of strap down is fewer moving parts making it more reliable.
