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时间:2010-05-02 22:48来源:蓝天飞行翻译 作者:admin
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The FMC uses the position calculated from the GPS data and
the ADIRU inputs to correct its ADIRU based inertial lateral
position. This is the FMC position and is calculated in terms of
latitude and longitude. The FMC will use its onside GPS input
from the multi mode receivers (MMR) if the data is valid. The
offside GPS data will be used if the onside data is invalid.
Vertical Position
This function calculates altitude and flight path angle (FPA).
Altitude is calculated from ADIRU inertial altitude corrected by
barometric pressure altitude. Flight path angle is calculated
from inertial vertical speed and FMC calculated ground speed.
The FPA is zero when the airplane is on the ground.
FMCS - FMC FUNCTIONAL DESCRIPTION - NAVIGATION SUB-FUNCTION
EFFECTIVITY
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BOEING PROPRIETARY - Copyright#- Unpublished Work - See title page for details.
737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
34-61-00-025
Actual Navigation Performance (ANP)
The ANP is the accuracy of the FMC calculated position. It is
calculated in nautical miles by the FMCS during all parts of the
flight. It is measured in nautical miles and it shows the radius of
a circle around the calculated FMC position where the
probability of the airplane being inside the circle is 95%.
The ANP calculation uses this data:
* The NAV stations in use
* GPS availability and accuracy
* Accuracy of DME range data
* Accuracy of VOR bearing data
* ADIRU drift.
The required navigation performance (RNP) is the accuracy
requirement of the FMC navigation performance within a
defined airspace. It is calculated in nautical miles and
represents the radius of a circle where the probability of the
airplane being within that circle is more than 95%. The default
values for RNP are contained in the navigation data base.
The default values for RNP are as follows:
* Oceanic - 12.0 NM
* Enroute - 2.0 NM
* Terminal - 1.0 NM
* Approach - 0.5 NM.
NAVAID Selection and Tuning
The FMC sends four navaid frequencies to the navigation
control panels. The frequencies then go to the DME
interrogators. If there is a fault with a control panel, the DME
interrogators get the data directly from the FMC.
Navigation Data Base
The navigation data base is stored in the flash EEPROM
memory of the FMC in two parts. There is the main body of
active data which is effective until a specified expiration date
and also a set of data revisions for the next period of effectivity.
This information is in the navigation data base:
* VOR, DME, VORTAC, and TACAN navigation aids
* Waypoints
* Airports and runways
* Standard instrument departures (SIDs)
* Standard terminal arrival routes (STARs)
* Procedure turns and holds
* Holding patterns
* Missed approaches
* Approach Procedures
* Approach and departures transitions
* Company route structure
* Terminal gates.
FMCS - FMC FUNCTIONAL DESCRIPTION - NAVIGATION SUB-FUNCTION
EFFECTIVITY
SHZ ALL 34-61-00
Page 88
D633A101-SHZ1 Jun 10/2003
BOEING PROPRIETARY - Copyright#- Unpublished Work - See title page for details.
737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
34-61-00-025
FMCS - FMC FUNCTIONAL DESCRIPTION - NAVIGATION SUB-FUNCTION
FMCS - FMC FUNCTIONAL DESCRIPTION - NAVIGATION SUB-FUNCTION
EFFECTIVITY
SHZ ALL 34-61-00
Page 89
D633A101-SHZ1 Jun 10/2003
BOEING PROPRIETARY - Copyright#- Unpublished Work - See title page for details.
737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
34-61-00-025
General
The performance sub-function provides optimum values for
airspeed and engine thrusts to provide the most economical
vertical path profile. It uses aerodynamic and engine models to
do these calculations. It calculates this data:
* Speed targets
* Speed limits
* N1 targets
* N1 limits
* Airplane gross weight.
Speed and Thrust Targets
The performance sub-function calculates the optimum speed
and thrust targets. These calculations occur during climb,
cruise and the descent phases of flight. The economy mode
(ECON) is the default mode for each flight phase.
In the economy mode of operation, the FMC uses the data input
from the flight crew (cruise altitude, cost index etc.) to calculate
the most cost efficient flight profile. Other modes (maximum
rate climb, long range cruise, speed descent etc.) are also
available and can be selected by the flight crew through the
MCDU.
When the VNAV mode is engaged, the speed and thrust targets
go to the FMC guidance function. The guidance function then
 
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