Pilot's Guide to Avionics 2014-2015 - 56

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conditions than you can in a cross wind," he said . "A good autopilot
may still wonder around a bit even in a dead-calm situation,
whereas a great autopilot will fly like it's on rails .
"This level of control requires much more complex control
laws . The way you make it fly more smoothly is to make it less
sensitive to perturbations . You can do that when you have unlimited
computing power . It can even anticipate things happening in
advance because it has more data available ."
One example Schwinn shared how this extensive amount of data
and processing power can be used to improve the performance and
safety of a new-generation autopilot is in capabilities like Avidyne's
Envelope Protection function .
"Basically, 99 percent of the autopilots that are flying right now, if
you put them in altitude and heading hold and pull the throttle back
to idle, they will hold the heading and altitude until the airplane
stalls," he explained . "At that point, they would have wound the trim
all the way to the stop and you would have a stalled and brutally
mistrimmed airplane . At that point, most of them (autopilots) would
disengage .
"I don't think you can find a worse behavior than that in terms of
pilot friendliness and overall safety . Make sure the airplane is in as
bad a shape as possible then give it up ."
Schwinn said a new-generation autopilot would not operate that
way because it has so much more information available about the
aircraft's overall situation .
"If you reach that situation, we start to do things to mitigate
what is happening and we do it very gently," he said . "If you pull
the power to idle, the speed will just bleed off until you are just a
handful of knots above the stall, and then the autopilot will gently
lower the nose almost imperceptibly, just to keep you at the safe
speed . At the same time, it will give you flashing lights and voice
warnings .
"I've done a number of demo flights where I've taken people
up and said let's watch Envelope Protection - boring - and that's
just the way it should be . The voice just says, 'under speed,
under speed,' and you just put some more power in . You just can't
imagine how exciting that situation isn't today ."
Schwinn said Avidyne's safety enhancements don't stop just
because the autopilot is disengaged .
"Envelope Alerting is the same kind of thing with the autopilot not
engaged," he said . "As you approach a stall, or bank into one, or if
you tend to put the flaps down when you are going too fast - which
I have a tendency to do - you will get these audio and visual alerts
with warnings before you get all the way into a critical situation .

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