MAX - Flight Management, Navigation

How many GPS receivers are installed?

Two GPS sensors in the MMRs receive GPS satellite signals, left and right. The left and right GPS sensors are independent, and each provides an accurate raw GPS position to the FMC, ADIRU, and other aircraft systems.

Raw GPS is the GPS position, navigation, and timing data delivered from the on-board GPS sensors without any mixing, combining, or filtering from other on-board systems

Are IRS outputs independent of external navigation aids?

IRS outputs are independent of external navigation aids.

What is indicated by a white ALIGN light on the IRS panel?

The ALIGN light illuminates steady when the respective IRS is operating in either the:

• ALIGN mode,

• initial ATT mode, or

• shutdown cycle

What is indicated by a white flashing ALIGN light on the IRS panel?

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

What does an illuminated FAULT light on the IRS panel indicate?

The FAULT light illuminates if a system fault affecting the related IRS ATT and/or NAV modes has been detected.

What does the illumination of an ON DC light on the IRS panel indicate?

The ON DC light illuminates if the related IRS is operating on DC power from the switched hot battery bus (AC power not normal)

How long can the right IRS operate without AC electrical power?

Backup DC power to the right IRS is automatically terminated if AC power is not restored within 5 minutes

How long does a full IRS alignment take?

Alignment time varies from 5 to 17 minutes depending on aircraft latitude.

What is Automatic Navigation Realignment (ANR) and when does it activate?

When a fast realignment is initiated or the aircraft parks after a flight and remains motionless for at least 7.5 to 15 minutes with the ADIRUs still in the NAV mode and valid GPS data available, the Automatic Navigation Realignment (ANR) mode will perform a complete realignment automatically

What does the illumination of the ILS light on the IRS panel indicate?

Illumination of the ILS light indicates a failure of both ILS sensor units. Illumination of the ILS light during MASTER CAUTION recall indicates a single ILS sensor unit has failed.

Do the FMCs operate independently?

The Flight Management System (FMS) is comprised of the following components:

• Flight Management Computer System (FMCS)

• Autopilot/Flight Director System (AFDS)

• Autothrottle (A/T)

• Inertial Reference Systems (IRS)

• Global Positioning System (GPS)

Each of these components is an independent system, and each can be used independently or in various combinations.

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.

How is FMC position data calculated with the loss of GPS inputs?

When external position (GPS, radio navigation) updating is not available, the FMC uses the IRS position as reference. When the IRS is the only position reference, the FMC applies an automatic correction to the IRS position to determine the most probable FMC position

How is takeoff thrust reduced from maximum takeoff thrust?

A takeoff thrust less than the full rated thrust may be achieved by using an assumed temperature that is higher than the actual temperature.

Where does the FMC receive fuel quantity information from?

The FMC receives fuel quantity data from the Fuel Quantity Indicating System (FQIS) and from the engine or from manual entries on the MCDU

What are the sources of position data to the FMC?

The FMC determines the present position from the IRS, GPS, and navigation radios

Which input has the highest-weighted priority for FMC position?

GPS

What criteria must be met for LNAV to engage?

LNAV provides steering commands to the next waypoint. If selected:

• LNAV engages when laterally within 3 nm of the active route leg

• 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 is a VNAV descent path calculated by the FMC?

The descent path starts at the calculated T/D point and includes waypoint altitude restrictions. The path is based on:

• E/D point

• idle thrust

• speedbrakes retracted

• descent wind speed decreasing with decreasing altitude (or loadable winds)

• applicable target speed