Avionics Maker First To Certify Underspeed Protection That
Guards Against Autopilot-Induced Stalls
Avidyne announced Thursday they have received FAA amended STC
approval for their recently-certified DFC90 Digital Flight Control
System which enables speed-based Flight Envelope Protection.
Avidyne DFC 90
"Avidyne's Flight Envelope Protection guards against autopilot
and flight director-induced stalls and overspeeds, which lead to a
significant number of GA accidents," said Patrick Herguth,
Avidyne's Chief Operating Officer. "The DFC90 with Flight Envelope
Protection provides significant safety enhancement, especially for
pilots in high work-load IFR
environments."
"The certification of Flight Envelope Protection is a
significant achievement for Avidyne, as well as a considerable step
forward in general aviation autopilot performance and safety," said
Avidyne President and CEO, Dan Schwinn. "Avidyne is committed to
continuously enhancing safety for all of our customers, and Flight
Envelope Protection, as well as the Straight and Level function and
other capabilities of the DFC90, establish a new watermark in
general aviation autopilot performance and safety."
Flight envelope protection is designed to significantly enhance
safety by addressing many of the situations that lead to accidents.
Accident data have pointed to many scenarios where Flight Envelope
Protection could have made a positive difference.
One example scenario is when the pilot is descending at reduced
power to the Final Approach Fix, where the autopilot captures the
preseleced altitude. If the pilot were to get distracted on the
radio or for other reasons and forgets to apply adequate power to
maintain altitude, the DFC90's aural and visual "Underspeed"
warning would make the pilot aware of his dangerously decaying
airspeed and prompt him to take action, and the autopilot's Flight
Envelope Protection would gently reduce the pitch of the airplane
to maintain a 20% margin above stalling airspeed (1.2X Vs).
Another observed scenario shows how Flight Envelope Protection
provides protection even in an engine out situation. In a Turbo
airplane at high altitude, due to an oxygen system failure or
oxygen exhaustion, the pilot has been incapacitated from hypoxia.
The autopilot is engaged and holding altitude. The aircraft flies
along until fuel starvation on the selected tank occurs causing the
engine to stop. With existing autopilots, the autopilot will
continue to try and hold the pre-selected altitude and fly the
airplane into a stall. With Flight Envelope Protection, the
autopilot would instead reduce the pitch of the airplane as
airspeed declines due to lack of engine power, inducing a smooth
descent. At a lower altitude with higher pressure and adequate
ambient oxygen, the pilot could recover, assess the situation,
switch tanks, perform a restart, and have a much more favorable
outcome.
For Flight Envelope Protection, available lift and speed margin
are calculated constantly whenever any autopilot or flight director
modes are in operation. As the aircraft approaches stall, the
autopilot gradually reduces bank (if in a turn) and pitch just
enough to maintain a 20% airspeed margin over the stall speed,
while visually and audibly annunciating the condition to the pilot.
As a result, departure from controlled flight is prevented with the
least impact on achieving mission-level objectives like navigation,
climb or approach. Overspeed is handled similarly, with
anticipation and minimal but effective inputs. In Flight Director
modes, all these actions appear as guidance cues with corrections
blended into the "V-bar" commands.
Display Showing An Underspeed Condition
The DFC90 is an attitude-based digital autopilot system that is
designed as a slide-in replacement for the S-TEC55X autopilot in
existing Entegra-equipped Cirrus SR20 and SR22 aircraft. The
significant performance and safety benefits of the attitude-based
DFC90 make it a very attractive upgrade for the more than 4,000
owners of Entegra-equipped Cirrus aircraft.
The Release 8.0.2 software and Mod 55 PFD hardware upgrades
enable the DFC90 autopilot to take advantage of the precision
attitude information of Entegra's integrated Air Data and Attitude
Heading Reference System (ADAHRS), without the need for costly
wiring changes to the aircraft.
The DFC90 has all the standard vertical and lateral modes of
operation of a turbine-class autopilot system, including Flight
Director (FD), Altitude Hold (ALT), Airspeed Hold (IAS), Vertical
Speed Hold (VS), Heading (HDG), and Navigation (NAV, APPR, LOC/GS,
GPSS). Customers upgrading from the STEC 55X will notice several
major performance and feature improvements including:
- Greatly improved stability due to the use of attitude data to
control the autopilot inner control loops. This is particularly
evident and important when tracking an ILS to minimums in windy
conditions.
- Avidyne's speed-based Flight Envelope Protection virtually
eliminates autopilot-induced stalls (underspeed) and overspeeds,
which lead to a significant number of GA accidents. With Flight
Envelope Protection, the autopilot avoids exceeding the flight
envelope while providing visual and aural warnings to the
pilot.
- The new Indicated Airspeed Hold (IAS) vertical mode includes a
dedicated Airspeed knob and a new airspeed bug on the PFD, and
provides a more elegant way to make Flight Level changes.
- The"Straight & Level" button overrides all autopilot modes
and levels the aircraft in both pitch and roll from a wide range of
capture attitudes for an added measure of safety.
- The Flight Director capability of the DFC90 is vastly improved
and greatly improves the ability to hand-fly approaches.
There are many other improvements, such as a dedicated Vertical
Speed knob, pitch hold mode, wide autopilot engagement, additional
annunciations in PFD 8.0.2, a dedicated GPSS button, automatic Back
Course Approach selection, multiple color annunciations to indicate
armed and active states, intercept mode annunciations, and
Avidyne's hallmark ease of use.
The retail price of the DFC90 Digital Flight Computer is $9,995.
The cost of Release 8.0.2/Mod 55 is $3,895 for PFDs that are at
Release 7. The cost of Release 8.0.2/Mod 55 is $5,395 for PFDs that
at are currently at Release 6 or older.
DFC90s are now shipping, and PFDs with Release 8.0.2 and MOD 55
enhancements are available through Avidyne's Platinum Exchange
program.