Flight Management & Navigation Flashcards
Is IRS output information independent of or reliant upon external navigation aids?
IRS outputs are independent of external navigation aids.
How long does IRS alignment take?
Alignment time varies from five minutes to seventeen minutes depending on aircraft latitude.
When does the ALIGN (white) illuminate steady on the IRS panel?
The ALIGN (white) light illuminates steady when the respective IRS is operating in either the:
- ALIGN mode
- initial ATT mode, or
- shutdown cycle
What does a flashing ALIGN (white) on the IRS panel during preflight indicate?
The ALIGN light will flash when alignment cannot be completed due to IRS detection of:
- significant difference between previous and entered positions or an unreasonable present position entry, or
- no present position entry
Without AC power, how long can the IRSs operate? What light(s) will you see?
The IRSs can operate on either AC or DC power. The left IRS is normally powered from the AC Standby Bus, and the right IRS from the AC Transfer Bus 2. If AC power is not normal or removed, either or both systems automatically switch to backup DC power from the Switched Hot Battery Bus and the ON DC caution light illuminates.
NOTE: Backup DC power to the right IRS is automatically terminated if AC power is not restored within five minutes.
What does an VERIFY POSITION scratchpad message indicate?
If the latitude/longitude position is not within 4 nm of the origin airport, the CDU scratchpad message VERIFY POSITION is displayed.
How many GPS receivers are installed?
Two GPS receivers receive GPS satellite positioning signals from the GPS antennas.
Are the FMCs independent of one another? Do they compare information?
The Flight Management Computer System is an independent system.
With a dual FMC installation, one
FMC is always designated as primary. This is controlled by the position of the FMC Source Select Switch. The Primary FMC ensures synchronization between the FMC’s.
Where do the FMCs receive their inertial data from?
Usually, the FMCs receive inertial data from their on-side ADIRU (left ADIRU to FMC 1 and right ADIRU to FMC 2).
If the on-side ADIRU malfunctions or it is in the ATT or ALIGN mode, the FMC uses the data from the other ADIRU.
What’s the criteria for airports to be included in the nav database?
All destinations, alternates and frequently used charter and maintenance locations will be included in the database. Other airports will be added as deemed reasonable, and must comply with the following:
- must have at least one paved runway
- must have at least one runway that is greater than or equal to 5000 ft long
- must have at least one runway that is greater than or equal to 100 ft wide
- must have at least one instrument approach procedure. (Exceptions to this criterion may be made due to operational needs.)
How can takeoff thrust be derated?
Fixed derates can be selected on the N1 LIMIT page.
What sources do the FMCs use to determine position? In what order?
FMC position updates from navigation sensor positions are used in the following priority order:
• GPS
• two or more DME stations
• one VOR with a co-located DME
• one localizer and co-located DME
• one localizer
NOTE: DME updating is defaulted OFF.
What criteria must be met for LNAV engagement?
LNAV provides steering commands to the next waypoint. If selected:
• LNAV engages when laterally within 3 nm of the active route leg
• if outside of 3 nm of the active route leg, LNAV engages if on an intercept heading of 90° or less and the intercept will occur before the active waypoint
How does the FMC calculate a descent path during a VNAV PTH descent?
From the BOD backwards, using altitude and speed constraints, wind and anti-ice use.
The descent path is computed prior to the top of descent and is then frozen unless the pilot executes a major edit to the flight plan, such as a:
• lateral route modification
• change in a speed or altitude constraint, or
• change to the descent speed in the FMC
The path is not adjusted or recomputed during descent even if:
• aircraft is above or below the path
• airspeed is too fast or too slow, or
• Speed Intervention is used
