Figure 5-25.-Approach power compensator simplified schematic.
requiring a change of power setting. When a
the APC operates with an approximate 11 percent
increase in gains from STD. This results in APC
power change is necessary, the computer sends an
electrical signal to the rotary actuator through the
performance that is essentially the same regardless
control amplifier. The rotary actuator motor then
of ambient air temperature, with the following
drives the engine control linkage to accomplish
temperature settings: COLD below 4C (40F),
the required power change. The system is capable
STD from 4C to 27C (80F), and HOT above
27C.
of driving the throttle linkage at speeds up to 25
degrees per second. The APC can vary the engine
RPM from full throttle to 67 percent RPM at
temperatures above 0F, or to 58 percent RPM
REVIEW SUBSET NUMBER 11
at temperatures below 0F.
Q1. To maintain the best angle-of-attack
Since engine performance varies with ambient
air temperature, the APC includes a three-position
during landing approaches, the approach
temperature switch to compensate for this effect.
power compensator automatically controls
At low ambient air temperatures, the thrust
change per degree of throttle movement is greater
than at high ambient air temperatures. When the
APC temperature switch is in COLD, the APC
Q2. The approach power compensator circuit
operates with a 15 percent reduction in gains
from those with the switch in standard (STD).
de-energizes when the pilot turns it off, the
aircraft touches down, and
Conversely, with the temperature switch in HOT,
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