Why is it important, reaching the Cruise FL to ensure CRZ ALT mode is displayed on FMA ?
CRZ ALT mode on FMA means that in managed speed mode :
- The aircraft will fly ECON SPEED profile during cruise as determined by the FMS
- the ATHR will operate in N1(EPR) soft mode for more efficient thrust regulation.
What systems are affected by a negative FMS NAV ACCURACY check ?
- Auto Pilot / Flight Director (managed / selected mode)
- ND (Arc - Rose NAV / Rose VOR – ILS, raw data)
- EGPWS (ON/OFF)
How is the FMS position computed with GPS primary ?
The GPS directly interfaces with the IRSs which output a GPIRS position. When a GPIRS position is available, it supersedes the RADIO position if available, so that the FMS position tends to the GPIRS position.
The GPS provides 2 essential data, additionally to position (Lat/Long/Alt) :
- The ACCURACY of the Lat/Long position: it is a direct function of the satellite constellation in view of the aircraft. If the satellites are low on the horizon, or if their respective position is unfavorable, the resulting accuracy will be poor. It is provided as a “figure of merit”. This accuracy can be computed with a high probability of confidence.
- The INTEGRITY, which is a direct function of the number of satellites in view of the aircraft, allows a defectuous or erroneous satellite to be rejected. If 5 or more satellites are in view, several combinations of those satellite signals may be used to process “several positions” and to carry out reasonableness tests on the satellite signals themselves.
Therefore if the GPS position (or GPIRS position) fullfills the INTEGRITY and ACCURACY criteria, this means that this position is the BEST RAW DATA position available.
How is the FMS position computed without GPS primary ?
FMS position is derived from:
- 3 IRS positions blended into a MIX IRS position
- a RADIO position using 2DMEs, or a VOR/DME
The FMS continuously computes :
- the FMS position out of MIX IRS and RADIO positions; When a RADIO position is available the FMS position tends towards the Radio position.
- the BIAS between MIX IRS and FMS position to benefit from the latest update when the RADIO position becomes unavailable.
- The ESTIMATED POSITION ERROR (EPE) of its own position.
What is the avoidance rule for a red echo on the weather radar ?
DECISION TO AVOID: NOT LATER THAN 40NM
AVOID DISTANCES:
Upwind / 20 NM / 5000 ft above
Below FL 230, OAT >0°:5NM / OAT <0°:10NM
What are the OPT, REC MAX and MAX MAX altitudes used by the FMS ?
- OPT ALT:
→ Gives the best specific range (NM/kg) based on the current gross weight, cost index, temperature, wind
→ Allow a minimum cruising time of 15 min - MAX REC ALT:
→ Provides a 0.3 g buffet margin
→ Computed using current gross weight and temperature and anti-ice is off
→ Allows a minimum rate of climb of 300 ft/mn at MAX CL thrust
→ With 1 engine out, displays Recommended Maximum engine-out altitude
(based on LRC speed and assuming anti-ice is off)
→ Above this altitude, Crew are advised that they are flying beyond the .3g boundary. - MAX MAX ALT: It’s the altitude allowing a 0.2g buffer limit,
above that altitude managed modes are no longer available.
On what criteria does the MCDU compute the FUEL PRED page for a diversion ?
- Weight is Landing weight at destination
- Cruise level, FL 220 for less than 200NM, FL310 for more
- CI= 0, Speed equal to Maximum Range speed
- 0 wind (Alternate field of DES WIND page to insert a wind)
- Constant Delta ISA (Delta ISA at destination)
- Airway distance on a company route, direct otherwise
What is the Maximum Rate of Climb Speed all engines operating and single engine (speed to reach a given altitude in the shortest time) ?
All Engines operating, Turbulence Speed achieves maximum rate of climb
One engine inoperative, Green Dot will be used
How are the characteristic speeds displayed on PFD and MCDU computed ?
- Speeds displayed on the PFD are computed by the FE (Flight Envelope).
- Speeds displayed on the MCDU TAKEOFF and/or APPR, GO AROUND pages, VLS, F, S and Green Dot are computed by the FMGC.
Computations made by FE and FMGC are based on the gross weight information transmitted by the FCMC (Fuel Control and Monitoring Computer).
How do you quickly figure out the fuel needed in case of loss of one Engine?
- MCDU Fuel page is accurate for Single Engine Ops
- If MCDU Fuel page is not available, use this formula to compute it:
- Trip Fuel = 15 x Distance to destination
- Add 1 t for the approach
- Add 3 t for the Reserve Fuel
• QRH In Flight Performance gives:
Fuel from any moment in cruise to Landing
Average Pitch / N1 for relevant configurations in case of Unreliable airspeed
• Level off after Take Off - Flaps 1 : 6° / 55% - Flaps 2 : 9.5° / 57% • Cruise : 2.5° / 70% • Descent : 0.5 ° / Idle • Approach : 4° / 45 %
