(5)  
The FMCS provides speed and thrust targets for the selected flight phase and mode of operation. The FMCS also computes thrust limits to assure protection of the engines against possible overboost. The speed targets are transmitted to the DFCS, and displayed on the air data instruments. The thrust targets are transmitted to the A/T, and displayed on the engine instruments.

 E. Flight Envelope Protection
 (1)  Speed and thrust targets provided by the FMCS must not exceed the limits of airplane and engine performance. Also the systems flight planning computations must offer performance options that are within the airplanes capabilities. The FMCS operational program continuously monitors actual flight conditions, computed performance targets, and data entries. These variables are evaluated by the FMCS with respect to the computed or programmed capabilities of the airplane and its engines. Any condition that exceeds the airplane or engine performance limits is flagged as invalid, and the actual outputs of the system are restricted by the computed limit boundaries.
 F. Performance Modification Factors
 (1)  The aerodynamic and engine models used as the performance data base for the FMCS represents the average, in-service model of the 737-300. This data is derived from airplane design information and flight tests. Since each airplane performance is different, factors which adjust the airplane drag and fuel flow modeling data over a range of -9.9% to +9.9% from the baseline may be entered on the CDU and are retained in NV RAM for continued use.
 9. Navigation Computation (Fig. 11)
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A 737-300/400/500MAINTENANCE MANUAL

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 A.

B.
C.
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A
737-300/400/500MAINTENANCE MANUAL
The FMC has provisions for both self-contained and radio-augmented navigation. The system furnishes continuous solutions for the following basic navigational outputs. These basic outputs apply to navigation in the lateral and vertical planes.
 (1)
Airplane Position (latitude, longitude, and altitude)

 (2)
Ground Speed

 (3)
Flight Path Angle (FPA)

 (4)
Drift Angle (DA)

 (5)
Track Angle

 (6)
Wind Velocity and Direction
The basic navigational output data is computed using optimally mixed
 inputs of:

 (1)
IRS position (latitude, longitude, and altitude)

 (2)
Vertical Speed

 (3)
Ground Speed Components (north/south, east/west)

 (4)
Heading (magnetic and true)

 (5)
Pressure Altitude

 (6)
True Airspeed

 (7)
DME Slant Range

 (8)
VOR Bearing
Operation of the navigation function consists of the following processes:

 (1)
Compute Velocity

 (2)
Compute Altitude

 (3)
Compute Horizontal Position

 (4)
Compute Position and Velocity corrections

 (5)
Choose Navaids

 (6)
Choose IRS
The navigation function will process measurements from two DME stations
 of acceptable geometry, or process measurements from a colocated VOR/DME
 facility. A reasonableness test is included to screen out any erroneous
　
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