1)  The pitch attitude integrator computes four functions: pitch compensation - Versine, pitch rate integral command, pitch path command, and pitch F/D bar command. The integrator synchronizes pitch computations when the A/P is not in the V/S mode. It also selects the correct pitch reference for the V/S mode and ensures the pitch command produced is in the correct direction. Gain programs are applied as necessary.

 (b)
Gain Schedules

 1)  Four gain schedules are used. Gain schedule 1 controls versine as an inverse function of impact pressure (IAS) and as a direct function of flap position. Gain schedule 2 controls flight path acceleration as an inverse function of IAS and TAS. Gain schedule 3 controls pitch rate as a function of the cosine of roll attitude commands. The pitch rate is the summation of wind acceleration and AOA rate components. Gain schedule 4 controls V/S error as a function of inverse TAS. The V/S error is the difference between selected V/S and existing V/S.
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 (c) Synchronization 1) During synchronization, the V/S command from the vertical speed low pass filter goes to zero when vertical speed engage is a logic zero. The logic zero is generated as a pulse when CMD is engaged and when switching from one mode to another. During synchronization the pitch attitude integrator maintains a constant output for elevator stability.
 2)  The V/S error is synchronized to zero by V/S command lag filter when vertical speed engage is a logic zero. The output from V/S low pass filter is zero. With vertical patch control a logic zero, the pitch rate path compensation signal is removed from the pitch rate integral command signal. With inputs zero, the pitch path integral command is zero. The pitch F/D bar command and pitch path command are zero.
 (d)
V/S Mode Logic/Switch Signal Status

 1)  After synchronization, V/S engage and vertical path control are both logic 1. Vertical speed command lag filter and vertical speed low pass filter are activated and S1 is closed. The FLCH and vertical position commands are zero. The VNAV, FLCH and vertical position integral commands are zero.

 (e)
V/S CMD Signal Processor Outputs

 1)  With V/S ENG mode, pitch attitude integrator output is proportional to filtered V/S error path command and V/S error integral command and pitch rate path compensation. The V/S error path command is provided as the pitch path command input to the pitch attitude integrator. The V/S error integral command and pitch attitude integrator are summed and provided as the pitch rate integral command input to the pitch attitude integrator.

 (f)
V/S Mode Reference

 1)  The V/S reference from V/S command lag filter is developed from the MCP selected vertical speed (altitude rate) display. The display is automatically set to the existing vertical speed at V/S ENG. The display is manually set by rotating the VERT SPD wheel.
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757 MAINTENANCE MANUAL
 2)  Prior to V/S engage, V/S mode reference is synchronized to the IRS altitude rate value. The output is zero when V/S engage is zero.
 3)  After V/S engage, the V/S mode reference signal in V/S command lag filter is time delayed and integrated to dampen any rapid VERT SPD wheel changes. Rate changes are limited to prevent exceeding 0.lg during V/S capture. The output from V/S command lag filter is summed with IRS altitude rate value to provide the V/S error.
V/S Error Signal Processing
 1)  The V/S error signal is modified as a function of inverse TAS and applied to a V/S low pass filter. The low pass filter processes the gain scheduled V/S error through an integrator with a time constant of 1.0 seconds. This provides the pitch path CMD.
Pitch Path Command
 1)  The pitch path command provides a signal, proportional to V/S error, to change elevator deflections for short turn (immediate response) due to V/S errors from the selected or present value. It diminishes as the airplane attitude changes and so decreases the V/S error magnitude. The V/S error will not go to zero with pitch path command only, due to changed aerodynamic effects.
　
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