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022 05 01 00 Basic principles
022 05 01 01 Systems
(01) State that inertial navigation/reference systems are the main source of attitude and one of the main sources of navigational data in commercial air transport aeroplanes.
(02) State that inertial systems require no external input, except TAS, to determine aircraft attitude and navigational data.
Syllabus reference BK Syllabus details and associated Learning Objectives
(03) State that earlier gyro mechanically stabilised platforms are (technically incorrectly but conventionally) referred to as inertial navigation systems (INSs) and more modern fixed (strap down) platforms are conventionally referred to as inertial reference systems (IRSs). INSs can be considered to be stand-alone, whereas IRSs are integrated with the FMS.
(04) Explain the basic principles of inertial navigation (including double integration of measured acceleration and the necessity for north–south, east–west and vertical components to be measured/extracted).
(05) Explain the necessity of applying correction for transport precession, and Earth rate precession, coriolis and gravity.
(06) State that in modern aircraft fitted with inertial reference system (IRS) and flight management system (FMS), the flight management computer (FMC) position is normally derived from a mathematical analysis of IRS, global positioning system (GPS), and distance measuring equipment (DME) data, VHF omnidirectional radio range (VOR) and LOC.
(07) List all navigational data that can be determined by a stand-alone inertial navigation system.
(08) State that a strap-down system is fixed to the structure of the aircraft and normally consists of three laser ring gyros and three accelerometers.
(09) State the differences between a laser ring gyro and a
Syllabus reference BK Syllabus details and associated Learning Objectives
conventional mechanical gyro.
022 05 02 00 Alignment and operation
022 05 02 01 Alignment process, incorrect data entry, and control panels
(01) State that during the alignment process, the inertial platform is levelled (INS) or the local vertical is determined (IRS), and true north/aircraft heading is established.
(02) Explain that the aircraft must be stationary during alignment, the aircraft position is entered during the alignment phase, and that the alignment process takes around 10 to 20 minutes at mid latitudes (longer at high latitudes).
(03) State that in-flight realignment is not possible and loss of alignment leads to loss of navigational data although attitude information may still be available.
(04) Explain that the inertial navigation system (INS) platform is maintained level and north-aligned after alignment is complete and the aircraft is in motion.
(05) State that an incorrect entry of latitude may lead to a loss of alignment and is more critical than the incorrect entry of longitude.
(06) State that the positional error of a stand-alone INS varies (a typical value can be quoted as 1–2 NM/h) and is dependent on the gyro drift rate, accelerometer bias, misalignment of the platform, and computational errors.
Syllabus reference BK Syllabus details and associated Learning Objectives
(07) Explain that, on a modern aircraft, there is likely to be an air-data inertial reference unit (ADIRU), which is an inertial reference unit (IRU) integrated with an air-data computer (ADC).
(08) Identify examples of IRS control panels.
(09) “Explain the following selections on the IRU mode selector:
— NAV (normal operation);
— ATT (attitude only).”
(10) State that the majority of the IRS data can be accessed through the FMS control and display unit (CDU)/flight management and guidance system (FMGS) multifunctional control and display unit (MCDU).
(11) “Describe the procedure available to the pilot for assessing the performance of individual IRUs after a flight:
— reviewing the residual indicated ground speed when the aircraft has parked;
— reviewing the drift given as NM/h.”