Avionics News September 2022 - 50

Autothrottle controls, such as go-around and disengagement, are immediately at-hand on
the throttle quadrant of this Cirrus SF50 Vision Jet.
AUTOTHROTTLE
Continued from page 48
Reducing workload and
increasing safety
Adding autothrottle to engines with FADEC
is easier because it prevents engine exceedances,
according to Tom Grunbeck, director of
autothrottle products for Innovative Solutions &
Support. In aircraft not equipped with FADEC
powerplants, " managing torque and temperatures
is a big part of pilot workload. "
To reduce that workload, IS&S developed its
ThrustSense autothrottle system that provides
FADEC functionality. Now standard equipment
on new Textron/Beechcraft King Air 260/360,
ThrustSense is an STC retrofit for the King Air
200/300 series and PC12 as well as the turbofan
Citation CJ2, CJ3, CJ4 and M2. It also provides LifeGuard
VMCa
protection, mitigating the low-and-slow challenges facing
engine-out operation.
The retrofit challenges of installing autothrottle in general
aviation aircraft " are price, weight and getting it in the airplane, "
he continued. An acceptable price depends on the market. The
current kit for a King Air with Pro Line avionics " is $69,000, and
installed it is around $80,000. That's the first thing that made it
acceptable " to this market segment, Grunbeck said.
Weight and getting the autothrottle system in the airplane are
co-dependent challenges. Installed, ThrustSense adds less than
5 pounds to a King Air's gross weight. First, IS&S designed and
patented small actuators that weigh about 1.5 pounds each and
fit just below the power levers. While the servos move the go
levers, pilots can override them at any time by simply adjusting
their position with minimal additional force.
IS&S saved even more weight by not adding an autothrottle
computer to the airplane. It replaced the Pro Line standby
instrument with one with the exact same form and fit that adds
the autothrottle computer to its originally certified standby
responsibilities. The autopilot computer is programmed for a
specific aircraft and its limitations, which enables the computer
to automatically adjust the power from takeoff to landing.
Pilots have two modes of operation, power or torque, and
they can choose either in any phase of flight. The power mode
delivers max power for takeoff and climb within the engine's
torque and temperature limits adjusted for ambient conditions,
contributed by the airplane's air data system. Pilots arm the
system through the standby instrument and trigger it with the
go-around button on the left power lever. The disconnect button
is on the right power lever.
50 AVIONICS NEWS * SEPTEMBER 2022
In cruise, the speed mode lets the pilot pick one. " If it is set
too high, ThrustSense won't get it there if it violates the torque
and temperature limits, " Grunbeck said. When cruising in power
mode, it will set the max speed for the engine limits. The FMS
can also provide the autothrottle speed, including instrument
approaches. It also provides envelope control. " If you get down
to 1.3VS
, the throttles advance to power out of the stall situation.
They also come back when approaching an overspeed. " The
system also adjusts power when the pilots change the prop
settings.
IS&S will soon introduce ThrustSense's Guard mode.
" If manually flying the airplane and the pilot approaches an
exceedance, " Grunbeck said, " ThrustSense will deliver a haptic
warning through the power levers, so the pilot knows to back
off. " The autothrottle computer gets all of its information directly
from the engine and other aircraft sensors, which mitigates any
latency issues. ThrustSense " instantly reads temp and torque as
soon as the engine sensor senses it. "
This instant and intimate connection is the heart of
ThrustSense's VMCa
system. Should an engine fail, the computer
determines rudder effectiveness for that phase of flight and
adjusts the power on the operating engine so the pilot can
maintain control. " As you gain control of the airplane it will
speed up, but it will keep power at a limit of directional control, "
Grunbeck said. " This system reacts quickly. If you lose an
engine on takeoff, it will come right back and manage power. All
the pilot has to do is focus on flying the airplane. "
And isn't that the underlying goal of advancing aeronautical
technology? Except, it seems, for pilots flying legacy pistonpowered
airplanes. While they can avail themselves of every
other form of trickle-down technology, managing their throttle,
prop and mixture will still be part of their in-flight workload. q
Courtesy of Garmin
Avionics News September 2022

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