(b)
Maximum Range
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DATA COMPUTER UNIT COMPUTERS Performance Management System Simplified Schematic Figure 2
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(c)
Manual (Selectable Speed)
(d)
Engine Out
(e)
Optimum Hold
(3) Descent
(a)
Optimum (Minimum Fuel)
(b)
Manual (Selectable Speed)
(c)
Direct (Straight Line)
(d)
Fixed Rate
4. Horizontal Navigation (Fig. 3)
_____________________
A. The PMS receives north velocity (VN), east velocity (VE), true heading (HDG) and uncorrected inertial present position from the Inertial Navigation Systems (INS). True airspeed is furnished to the PMS from the central air data computer. The PMS computer unit uses these inputs to calculate other horizontal navigation data required for computations and for display. The PMS also receives DME pulse pair data which is used to update the inertial present position in the PMS and in the INS.
(1)
True heading (HDG) is the clockwise angle from true north to the airplane center line.
(2)
Wind speed (WS) is the velocity of the wind with respect to a point on the earth's surface.
(3)
Wind direction (WD) is the clockwise angle from true north to the wind velocity vector.
(4)
Ground track angle (TK) is the clockwise angle from true north to an imaginary line on the earth's surface connecting successive points over which the airplane has flown (ground track).
(5)
Ground speed (GS) is the velocity of the airplane with respect to a point on the earth's surface. GS is the resultant vector sum of VE and VN.
(6)
Drift angle (DA) is the angle between the airplane center line and ground track or the angular difference between true heading and ground track angle. Drift angle is right when ground track angle is greater than true heading and left when ground track angle is less than true heading.
(7)
Desired track angle (DSRTK) is the clockwise angle from true north to an imaginary line on the earth's surface connecting successive points over which flight is desired (desired track). This line describes the great circle course between two successive waypoints and it is further defined by the intersection of a plane and the earth's surface when the plane passes through the two successive waypoints and the center of the earth.
(8)
Present position (POS) is the actual latitude and longitude coordinates of the point on the earth's surface directly below the airplane at any given instant.
(9)
Cross track distance (XTK) is the shortest distance between the airplane's present position and the desired track. Cross track distance is left when present position is left of the desired track and right when present position is right of the desired track. Cross track deviation (XTK DEV) is another term used for cross track distance.
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TRUE
NORTH
OR ORIGIN
TK TRACK ANGLE- POS -PRESENT POSITION
GS GROUND SPEED- -WPT WAYPOINT-
TRUE HEADINGHDG - DIS DISTANCE-TO-WAYPOINT-
DA DRIFT ANGLE- DESIRED TRACK ANGLE-DSRTK
CROSS TRACK DISTANCE-XTK VE EAST VELOCITY-
TRACK ANGLE ERROR-TKE VN NORTH VELOCITY-
TRUE AIRSPEED-TAS
WS WIND SPEED-
WD WIND DIRECTION-
Navigation Relationships
Figure 3
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TRUE
NORTH
DME Updating
Figure 4
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(10)
Track angle error (TKE) is the angle between the airplane;s actual ground track and the desired ground track or the angular difference between ground track angle and desired track angle. Track angle error is left when the actual track angle is less than the desired track angle and right when the actual track angle is greater than the desired track angle.
(11)
Distance (DIS/WPT) is the great circle distance between present position and a waypoint.
(12)
True airspeed (TAS) is the velocity of the airplane with respect to the air mass around the airplane. The PMS uses true airspeed to determine wind direction, wind speed, and drift angle.
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