Autoflight- FM Flashcards
Each FMGC computes its own position. From what sources is an FM position made?
MIX IRS + Radio
or
GPS
GPS / Inertial is the basic position mode if GPS is valid, what are the two other modes?
Radio / IRS
IRS only
What is the MIX IRS pos?
What happens if one IRS pos drifts from the other two?
What happens if an IRS fails?
What parameters are monitored for failure?
Average of all three IRS pos
Algorithm reduces influence of drifting IRS
IRS Failure: each FMGC uses its onside IRS or IRS 3
Inertial speed and position continuously tested. CHECK IRS 1/2/3 / FM POSITION if failed.
Threshold for failure is time-dependent.
Which priority does FMGC choose a GPIRS source?
Onside, GPIRS 3, Opposite
What happens if one GPS fails?
What happens if all GPIRS fail the Horizontal Integrity Limit or satellites fail?
Where can we manually deselect GPS updating?
Both ADIRUs select the same source and the failed GPS is dashed out on the POS MONITOR page
FMS rejects GPS updating and uses RadNav updating
From the NAVAID SELECTION page
GPS IS DELECTED shows on MCDU 80nm before ToD or at approach transition
What are the Radio Position sources?
Can an FMGC use offside navaids incase of navaid failure?
DME / DME
VOR / DME
LOC
DME / DME - LOC
VOR / DME - LOC
Yes- offside VOR or DME
What is FM position made of?
Where does it move in flight?
What is a bias and what happens if there is a failure of a position source?
How is the bias manually updated?
MIX IRS / Radio / GPS (GPIRS)
Moves towards the radio or GPS position at a rate depending on altitude
Bias is vector from MIX IRS to the Radio or GPIRS position
If Radio and GPIRS position lost, the bias is memorised until restored.
Updating the FM position manually will also update the bias
Why don’t we normally use takeoff shift?
As FM position at take off is inhibited when in GPS PRIMARY.
FM position updated to threshold on take off, so take off shift is used if an intersection is used
What are the four Navigation Modes in decreasing order of priority?
What happens on an ILS approach?
- IRS-GPS
- IRS-DME/DME
- IRS-VOR/DME
- IRS only
LOC provides lateral update on approach in addition to any of the four modes.
What is an EPU?
What is the EPU after IRS alignment or at take off?
Estimated Position Uncertainty
Estimate of FM position divergence
Calculation depends on mode in use
e.g. in IRS/GPS = √(FOM² + 100²) m
e..g in IRS ONLY = 8nm/h for half hour etc.
0.2 nm
When is NAV ACCURACY HIGH or LOW?
What value is set in REQUIRED?
Why might you see PROCEDURE RNP IS XX.XX or AREA RNP IS XX.XX ?
What are the default values?
HIGH- when EPU does not exceed RNP value
Manual / Nav DB / Default value
May see warnings if manual value is worse than the NAV DB value. Also may see the AREA warning if passing between areas with different values.
Default Values
Enroute: 2nm
Terminal: 1nm
Approach
* GPS 0.3
* Other 0.5
What are the two criteria for GPS PRIMARY to show?
RNP ACCURACY HIGH
and
GPS Integrity (no failures)
Why does FM/GPS POSITION DISAGREE show?
Either FM position deviates from GPS 1 or 2 by a certain threshold
Depends on latitude - 0.5’ below 55ºN/S. Inhibited above 70º
In Single FMGC mode, can one FMGC tune all navaids?
Yes, can tune both sides
How many DME can be tuned? What are they normally tuned to?
Four per side
1 DME for display
2 DME for radio pos
1 DME for ILS
Is the ADF ever automatically tuned?
Yes- for NDB approaches (when sequenced)
SPECIFIC NDB UNAVAIL if not found
When does RWY/ILS MISMATCH show?
When might a LOC / ILS not arm?
When an ILS is manually tuned different to that in the Nav d/b for the approach in the FPLN
When tuned manually but no CRS entered (usually done if NOT IN DATABASE shown)
Can we land if the IDENT is shown wrong on the PFD?
Do DME Idents show on ND?
Yes, but audio check to be performed
Not if manually tuned
How long for a normal / quick IRS align?
Why would IRS IN ALIGN show?
10 min / 30 sec
- excessive motion (restarts)
- MCDU / last POS disagree
- MCDU Lat / IRS calc’d lat disagree
- No MCDU pos given to IRS
What speed does CDA mode assume at 1000 ft?
What Landing Weight is assumed?
Is the wind profile used?
Are constraints used?
Is speedbrake assumed?
Vapp
Predicted LW
Wind profile and constraints used
Half speedbrake may be assumed for some segments
Does not update profile for OEI or change of approach data
When will waypoints sequence when in HDG?
Waypoint behind aircraft, within 7 nm XTRK (5nm on Final App)
Angle less than 90º.
What do predictions assume when on a MANUAL leg?
Direct to next waypoint
How many waypoints in a flight plan (destination / altn)?
Any predictions in the temporary flight plan?
250 (215/35)
None
Why should extreme caution be exercised when doing a Position Update?
When is it not possible?
Three example scenarios when appropriate
Based on pilot’s estimation of position, not accurate
Inhibited in GPS PRIMARY
- On ground- no flight plan on NAV dispay in ROSE NAV
- CHECK IRS / FM POS on MCDU
- FM/IR POS DISAGREE on ECAM
What margin does a constraint give for predictions before it turns amber? Speed?
What happens if OP DES pulled in cruise with a constraint (current alt) ahead?
250ft
10kt
Will level off immediately after engaging
When winds aloft are manually entered, what happens to the uplinked winds?
Does the actual IRS wind have an effect on predictions?
Interpolated between the two
Actual wind updates predictions
When does the ECON CRZ SPD transition to MACH?
FL250
When calculating an optimum cruise, what is the minimum time at cruise level? Minimum level?
5 mins
FL100
When is the energy arc / circle shown?
When in HDG/TRK and in CRZ / DES APP.
Within 180 nm of destination
considers speed constraints
What speeds to Engine Out predictions assume?
Green dot in climb
EO CRZ SPD in cruise
if above max OEI alt, assumes an immediate driftdown
What are the five conditions of REC MAX ALT?
What does it not account for?
When will a pilot-entered CRZ ALT be rejected?
- 0.3g buffet margin
- Can fly level at MAX CRZ rating
- Can attain 300 fpm at MAX CLB rating
- Can maintain a speed between GD / MMO
- Below certified max altitude
Does not account for Anti-ice use. Use EFB CRZ module.
Will be rejected if a 0.2g buffet margin cannot be acheived
What altitude is assumed for alternate routing?
What weight is assumed?
What speed / winds assumed?
FL220 (FL310 if over 200nm away)
Weight over original destination
Green dot, simplified wind/temp model.
If off-route, what angle is assumed for a return to trajectory on MCDU predictions?
45º
Assumes direct-to if next point is over 45º.
What is the relationship of Perf Factor to Fuel Flow?
Fuel flow = Standard Fuel Flow × 1.[Perf Factor]
∴ if Perf Factor = 3
FF = Standard FF × 1.03
What is the effect of a positive Idle Factor?
Shallower descents are predicted (more power in descent)
What are the things checked on the TO surveillance?
ZFW within range
V1 ≤ VR ≤ V2
V speeds satisfy
VMCG / VMCA / VMU / VS1G
What does the calculated final fuel assume?
30 mins hold @ 1500 AAL
in Conf 1, LRC
What is leg time for a standard hold?
What does LAST EXIT time mean?
1.5 mins above 14 000 ft
1 min below 14 000 ft
Time at which extra fuel = 0
What might be deleted with a Direct To on the ground?
V speeds
Flex temp
How many step altitudes can be stored? When are they ignored?
When is an optimum step altitude shown?
Four
Ignored when less than 50nm from calculated ToD
If fuel and time savings can be made stepping earlier / later
How many custom waypoints can be stored?
20 or 99
Depends on FMGC model
What does FIG OF MERIT mean on the Navaid page?
Distance upto which the navaid can be used for radio position computation
What happens if there are two waypoints with the same name on the same airway?
Closest one automatically chosen and duplicate page NOT shown
What is the meaning of the IRS value (nm) on the POS MONITOR page?
Deviation (nm) from onside FMGC position
What assumptions are made for distance and fuel on the CLOSEST AIRPORTS page?
- Uses constant wind value and current speed (sel/econ) to calculate cruise to overhead
- Conservative descent fuel value
How can you select LRC?
VAPP = VLS + ⅓ Headwind- min and max?
Delete cost index
+5 to +15 kt
(i.e min and max headwind to have effect on VAPP are 15 to 45 kt)
What is the highest RADIO minima that can be set?
700RA
After a go around, how can one enter CLB mode and get a managed climb speed?
Enabling the alternate / new destination
- LAT REV > ENABLE ALTN > CONFIRM TMPY > DTO
Maximum legs in Backup Nav?
- Simplified point-to-point GPIRS/IRS nav
- Normal flightplan continously saved in MCDU memory for BUNAV
- Max 165 legs
- Page for Onside IRS, IRS3 or GPS data
- Direct TO makes a discontinuity (no temp FLPN)
What is the magenta triangle (managed speed target) in OEI?
And in an OEI GA?
What bank angles will be reached with autopilot ON in OEI?
V2
VAPP or current speed, whichever higher, max VLS+15
15º below manoeuvring speed
25º above manoeuvring speed (SEL)
30º above maneouvring speed (MNG)
What is an OEI diversion point and why
What shows on TMPY before diversion point?
What should you do after the diversion point?
Last point common to SID and EOSID
EOSID shows
Stay on SID unless route to EOSID is assured clear of terrain + best strategy (will show in yellow)
What is the ECON speed before and after the THR RED ALT?
In the cruise?
In approach?
Before = V2
After = Green Dot
Cruise = EO CRZ
Approach= maintains VAPP
* LVR MCT, 15º bank limit
Backup Nav points
- If No nav db
- No Autotuning / radio pos / ldg elev
- If no perf data
- No CLB / DES / APP NAV / FINAL
- No managed speed
- No SPD/MACH changeover
- Other
- No EFOB / XTRA / ETA at DEST
- No managed modes
- All legs are CF (course to fix legs) hence many discontinuities
- May be deleted
- Still have automatic sequencing
- Monitor track (true) to attain XTRK = 0
- FPA allows better alt predictions
- D(nm) = ΔFL / FPAº
- Must periodically check NAV ACC using BRG/DIST
- CAT I only due no DH indication avail
- Display
- ARC/ROSE NAV if NAV ACC is high
- ROSE VOR if low
What does Descent Profile Optimisation do?
- Reduces the margins added to idle thrust
- Steeper approach
- Same rate as OPEN DES
After an RTO, FM may stay in TO mode. What speed, and how to reset?
- Stays in TO mode over 90kt
- TO data non-modifiable
- Delete SEC FPLN, Copy SEC, add new data, ACTIVATE
How quick is an automatic FM reset?
When is all data lost? How long wait?
2-3 sec + 25 sec synchronisation
If 3 resets in 2 min
Wait 1 min
- Single or Double FM reset does not affect ILS below 700RA (data lock)
- Above, LOC and GS lost, AP+FD disengage
*Non-ILS, FDs engage in basic modes
