NAV SPECIFIC TECH Flashcards
FMS, RNP, 1553, GPS
What are the independent functions of each SP? (Ie computed individually)
FD commands
Nav solution
What does partitioned by time and space mean wrt the SPs?
designed to protect flight critical functions
Time-protects computational bandwidth for safety critical functions
Space-protects memory space/registers/dedicated interfaces
What does the Flight Management Function provide?
Navigation
Route Planning
LNAV/VNAV guidance
RTAs
Prog page predictions
Perf predictions
MCDUs
Datalink
NAV/COM sensor management
Data comms control and routing
What does EGI stand for?
Embedded GPS/ inertials
what does a blended INU/GPS solution provide?
Position
Attitude
Rate
Filtered update method
Fully populated Nav state vector
What are the characteristics of the pure INU solution?
Full Nav state vector
Long term drift due lack of position updating
What are the characteristics of the pure GPS solution?
No attitude information
Short term but high accuracy
What does the “gps not in civil” message mean?
GPS receiver has lost satellite reception
What can effect INU alignment time?
Latitude
Satellite availability
What does PRAIM display?
RAIM availability
RAIM hpl
RAIM alert status
What is the only system that sends data to both SPs not just the master?
EGIs due time critical nature
How does the comms system work between each channel/bus A/B?
Either A or B will be allocated as primary based on continuous health checks by the bus controller (using parity bit)
How are the buses separated to prevent battle damage?
A & B separated by at least one inch
1 & 2 separated down opposite sides of aircraft
What is important to note about 1553 intermittent failures?
If some info is still getting through the other bus may not take over
Only if a bus is severed completely will the traffic definitely transfer to the secondary bus
How do the SPs communicate using the 1553?
- If SP 1 is master, SP2 becomes a remote terminal on Bus 2
FMCn FAIL plus FMCn NOGO, and POSSIBLY SINGLE OPERATION; what does this mean?
How to ident between 1553 or SP issue
- You can only identify if it’s a 1553 issue not an SP issue by looking at the Equipment history and seeing stuff like TACAN 2 B2 BA FAIL
Why do you select SYS>PWR CTL>ALL ON after an SP event?
When two SP resets occur in quick succession (ie 1st reset isn’t complete) the EGIs will be powered off
How many ground monitoring stations and antennas does GPS have?
5 monitoring stations updating satellite Nav messages
3 antennas w uplink capability
Where is the zeroise function in the FMS?
Init Ref>zeroise
Where are the CMU pages in the MCDU?
ACARS > SYS menu > ATS menu
What is the code for the VHFs?
RTA-50D
What is the code for the VUHFs
AN/ARC210s
What does CMU stand for?
Comms management unit
What is the safety standoff for the civil SATCOM antenna? (2)
8.5feet
20feet for longer than 3min/hour
Limitation to AWO altimeter
Only checked to +/- 200ft above 7000ft by maintenance, therefore unreliable above 7000ft (except hpa)
What are the primary systems used for navigation
2x embedded GPS/INS (EGI)/MMR systems
What does the GPS portion of each GPS/EGI do?
How many satellites can it track?
Uses precise time & location data from a satellite constellation to determine a/c position.
Up to 12 satellites at once
How does the INS work
The Inertial Navigation system
Starts from a known initial position, and using a highly accurate laser ring gyro & accelerometers to calculate the a/c position over time.
What are the five navigation modes in order of preferred use?
- Blended INU/GPS 1 & 2
- INU only mode 1 & 2
- GPS only mode 1 & 2
- INU/RADIO mode 1 & 2
- No nav mode (inertials only)
What does EHE stand for
estimated horizontal error
INU/GPS nav mode drift rate
WITHOUT GPS, at max 0.3nm/hr
INU only nav mode drift rate
Max 0.8nm/hr
How many satellites are required for RAIM?
exception?
- 5
- 4 with BARO-AIDING (where the ADC is used as a 5th source)
INU/RAD drift rate
Max 0.8nm/hr
Why do we use SPS not PPS
SPS is FAA (civil) approved (standard positioning service)
capable of PPS when keyed with crypto
when can you test the EGIs
GROUND ONLY (usually by maint) as while the IBIT is occuring, no nav will occur
Why would you turn the EGI into standby & how
- How: turn off & on again via power control page
- Why: to provide a method of sending initialisation info to the GPS (position/time/date & year)
When would you need to initialise the GPS?
How would you do it?
-When the nav sensor index page 3 shows no satellites at all and/or FOM is 9 for example.
- GPS INIT PAGE> IDENT (A/D ICAO code) > DATE > TIME
EGI in flight alignment - when?
how?
What must the aircraft do?
How long does it take?
- In flight, GPS position is valid & FOM is 4 or less.
- MCDU: Select IN FLIGHT
- Straight & level & unaccelerated
- 10mins
During an in flight EGI alignment, what information does it obtain from the GPS/ADC
- TAS
- Baro-alt
- Pressure alt
- Air data valid
GPS satellite page; what do these stand for?
- SV
- CN
- FC
- ST
- SV: space vehicle #
- CN: Carrier to noise ratio (5 is norm)
- FC: frequency used & code
- ST: Channel state
What does GPS RAIM do for the aircraft
- asses the a/c ability to operate under RNP constraints. If outside of limits, FMF will alert the crew.
- Predicts availability of adequate GPS satellite coverage along the route
What is something to note when calculating GPS predictive RAIM
The FMS will not predict past 0000z
What is automatic RAIM prediction?
When 2nm inbound to the FAF, the FMF automatically determines the predicted RAIM availability & position error at the FAF & MAPP & will alert if outside of tolerances/RAIM is not available
How to check the RAIM status of any fix or waypoint
Predictive RAIM page
How to check RAIM status for entire route & what information is required?
Flight plan RAIM page
- operational GPS
- route is active
- Perf is initialised
- ETD date & time are entered
- a/c is not airborne
- Predictive RAIM is not being computed
What to do if a RAIM WNG comes up in RNP asx?
Crew must deselect the current active GPS & allow the FMF to choose the next best solution
What is RNP
Required navigation performance
- provides estimates of the ability of the a/c to maintain is flight path within the prescribed limits
What two measures can be used to compare against RNP containment limit
ANP (actual navigation performance)
TSE (total system error)
When will you get;
the RNP UNABLE condition
The RNP EXCEED condition
- the RNP UNABLE condition: when ANP is greater than the containment limit OR loss of EGI OR SP
-The RNP EXCEED condition: When TSE exceeds the value for RNP.
What methods of navigation are acceptable for RNP asx?
- GPS
- GPS/INU
- INU only
- INU/RAD
What information is combined to produce ANP?
What is ANP directly related to?
- Position estimated error
- Path definition error
- Path steering error
Directly related to EHE
What are the 6 reasons for an RNP EXCEED message
- AP not engaged in APP mode
- ANP > than containment limit (2x RNP)
- Non WGS-84 datum selected
- Non dual EGI config
- Non duel SP config
- PPS mode is selected
What are the default RNP values
- ENR
- TERM
- APPCH
- ENR: RNP 4
- TERM: RNP 1
- APPCH: RNP 0.3
Where can you find the current RNP value
MCDU POS REF PAGE 2/4
How does a GPS receiver work
The GPS receiver calculates its own position and time based on data received from multiple GPS satellites. Each satellite carries an accurate record of its position and time, and transmits that data to the receiver.
what are the 3 component of GPS
Ground
Space
User
What does the below give you?
1 sat
2 sat
3 sat
4 sat
5 sat
1 sat: Nil
2 sat: Nil
3 sat: Position
4 sat: Position & altitude
5 sat: Position, altitude & RAIM
What are the 8 SP subsystems
- Controls & displays
- Flight controls
- FLT mgmt function
- Nav radios & sensors
- Communication radios
- Datalink radios
- Surveillance
- Safety & recording
What is the standard operation mode of the SPs
Dual mode, one SP is designated as the Master SP, and the other as Standby.
What are the main functions of the master SP
- Controls Nav & guidance
- Bus controller on both 1553 busses
- Provides FD
- Controls routing of data
In normal SP function, which SPs provide which FD data
- SP1 > AFCP1 > Pilots FD
- SP2 > AFCP2 > Co pilots FD
What do the SPs do in terms of FMS Nav solution
each SP will individually compute a navigation solution & will alert the crew if they are different.
What are the 3 rules of continuous coordination between the SPs
- STBY SP obtains data from its own inputs
- If the Master SP cannot obtain data directly, the Stanbdy SP passes the data to the Master & vice versa
- Each partition is responsible for passing sufficient data to the corresponding off-side partition
What decides which SP is designated as master
The platform systems through monitoring internal health of each SP. The FMF in the Master SP the assumes the role of master FMF.
What are the 2 primary functions of the STBY SP
-Computes selected Nav solution to compare against -master SP
- Receives & monitors data from Master SP iot to take over if required
What are the two redundancy modes of the SPs
- Dual mode: communicating & coordinated, one is master & other is standby
- Single mode: SPs are not coordinated but are communicating (degraded mode)
What criteria have to be satisfied iot have the SPs operating in dual mode. What will happen if they aren’t?
- SPs have completed initial coord
- Software versions are identical in both SPs
- Nav databases are identical
The SPs will enter single mode
What does the message SP RESYNC mean
What will occur?
occurs when there is a breakdown in coordination between the SPs
The Master SP will automatically initiate a cross load - the message ‘RESYNC IN PROG” will appear.
What does the message RESYNC REQUIRED mean?
When the SP detects a discrepancy that cannot be resolved by normal resync steps, the FMF declares the standby SP as invalid.
MANUAL RESYNC IS REQUIRED
How to manually resync the SPs
SYS > FMS CTRL > LSK R5 (will only pop up as an option under these cirumstances)
SP redundancy: database management
FMF ensures identical navigation & MAGVAR databases are loaded into both SPs
SP redundancy:MCDUs
When standby SP becomes master SP, MCDU displays are maintained
SP redundancy: Display system
When standby SP becomes master SP, displays are maintained. (momentary black screens & red Xs)
SP redundancy: route planning
Route planning is performed by the master SP. Flight plan data & changes are transferred to the standby SP
SP redundancy: guidance
Only provided by the Master SP.
SP redundancy: performance
computed by the master SP, initialisation data is also transferred to the standby SP
SP redundancy: Comms radios management
& Air-ground data link
Master SP manages & controls comms. Data is transferred from master SP to standby SP.
What is an ADC failure indicated by?
- a red X through IAS/ALT tapes
- a yellow X through VSI
- an IAS or ALT miscompare flag
What is an AP failure indicated by?
- uncommanded disconnect
- failure to connect
- FP or FD FAIL on PFD
- AFCPn NOGO on SYS STATUS page
What is an FD failure indicated by?
FDn flag on top RHS of ADI
What is an ICU failure indicated by?
- ICU light on one or more EXCAP station or loss of comms
What is an EIDS failure indicated by?
- Loss of a screen
- Red or yellow X
- warning flags
What is an EGI failure indicated by?
- loss of GPS info
- Loss of pilot ATT/HDG
- Loss of AFCP/FDs
- Loss of RADAR stab
NARF?
Navigation alignment refining feature mode. (Refines sensor parameters using rotation of the earth)
When will VNAV not work
> 15nm XTRK
Whizz wheel: calc HDG drift & GS for;
TRK 063, wind 140/78, TAS 300kts
RADALT fail affects what systems?
EGPWS, RADAR, TCAS
Radar alrimeter is valid to what height
2500ft
Hazardous areas of navcomm systems;
HF, SATCOM, MSAT, VHF, VUHF, TACAN/IFF/RADALT/TCAS
HF: 200ft
SATCOM: 20ft
MSAT: 5ft
VHF: 5ft
VUHF: 1ft
TACAN/IFF/RADALT/TCAS: nil direct contact
How can you ident a fail of the ICS
ICS light illumination on all excaps (located above ENTER button)
What are out available nav solutions
Max theoretical drift rate?
Blended INU/GPS
INU only
GPS only
INU/RAD
No nav
Drift: max 0.8nm/hr
What is ETAS
Effective true airspeed.
Used when increasingly large crosswinds are present - aircraft spends less time moving forward and more time moving sideways.
ETAS computes the true TAS experienced by the A/C when drift is >10deg
What does EGI BATT FAIL mean
Actions?
The EGI BATTERY has failed, the GPS will not store satellite ephemeris and almanac information, may be slow to align or not align at all.
Initialise the GPS
Enter position/time/date if possible
FMS does not display GPS date/time.
Cause?
Corrective action?
- If EGI IBIT is performed when the system date/time is incorrect, the EGR will not be able to report correct time/date
- corrective action: SOPS 2-15
What is PBN
Performance Based Navigation, encompassing both Area Navigation (RNAV) and Required Navigation Performance (RNP)
What are the Approved PBN Navigation Specifications for use on the C-130H
RNAV 10,5,2,1, RNP 4,2,1
What does the Nav Mgmt function do?
Controls, monitors and evaluates the available nav sources/modes and selects the most accurate for use by the FMF, crew & systems.
What does the aircraft navigational state include?
Aircraft position, speed, track, drift, attitude and wind data = nav state vector
What is an EGI
A self-contained, all attitude navigation system (GPS & INU)
What does the EGI produce
seperate position estimates from its GPS and INS subsystems, as well as a blended solution (which applies GPS based corrections to INS position data)
Where are the GPS antenna located?
2x on upper at FS320
What are the EGIs powered by
Both on ISOLATED DC bus, but both also powered by PAVS & CAVS seperately.
What are the EGIs powered by
Both on ISOLATED DC bus, but both also powered by PAVS & CAVS seperately.
What is INU/RAD
Solution that uses inputs from the INU and NAVAIDs listed in the database to provide nav state vector.
How are the EGIs managed in terms of SP/1553
Master SP has direct control of EG1 on 1553 Bus 1 and EGI 2 on Bus 2
How are the EGIs managed in terms of SP/1553
Master SP has direct control of EG1 on 1553 Bus 1 and EGI 2 on Bus 2
What band do the HF radios work
What do they provide
2 - 29.999999999MHz
Datalink, Automatic link establishment & SELCAL
How do HF radios work
transmitted from a base unit into the Earth’s atmosphere. These radio signals ‘bounce’ off the ionosphere and return to land, where they are received by another transceiver tuned into the same radio band
How do VHF radios work
Also LOS comms
30-300MHz
How are HF radios affected
In the ionosphere, ionisation (electrons stripped from atoms, producing electrically charged particles), occurs due to solar radiation.
Intensity of solar radiation effects the rate of ionisation of different layers of the ionosphere, therefore, when the sun is hotter (Day), frequency needs to be higher in order to reach the F region, to be refracted without being absorbed by the D region,
At night, frequency can be much lower as the D region no longer exists to attenuate the sky waves.
How do UHF radios work
UHF radio waves propagate mainly by line of sight and ground reflection. Cannot travel beyond a horizon. radio repeaters are used to continue beyond LOS if required. Used for satellite comms etc.
What is the 1553 network made up of
2x databusses, each with their own circuit, providing redundancy. 2x bus controllers on each bus, and an SP to each bus.
BUS 1/BC 1/SP 1 = one system
BUS 2/BCC 2/SP2 = another system
What will occur if one of the 2 1553 communications lines is severed?
comms will go back to the affected bus, which will communicate with the other bus. All TFC will transfer to the second bus.
FMSn Fail vs
FMCn Fail
Both will cause SINGLE OPERATION scratchpad message
- FMCn fail is a SFD message which identifies the true/hardware fail of an SP
- FMSn fail in FMS CTRL page indicates a communication error between the SPs
