Pilot's Guide to Avionics 2015-16 Edition - 47
Photo by Dave Higdon, PhotoProse Productions
BendixKing's KLR 10 angle-of-attack
Who says timing isn't everything?
A lot of fatal accidents in general aviation are related
to low-speed loss of control, according to the FAA and
National Transportation Safety Board officials. Industry
groups, such as the National Business Aviation Association
and the Aircraft Owners and Pilots Association, are putting
a greater focus on reducing LOC accidents.
These same safety experts across the board view the
increased situational awareness from an AoA as a better
way to address a frequent accident cause than sticking
solely with the airspeed indicator as a guide in those
situations where LOC is most dangerous.
The frequency and preventable nature of loss-of-control
accidents helped drive the increased availability and
use of AoA indicator systems. The FAA's February 2014
approval of new, nonrequired AoA systems for installation
in Part 23 aircraft requires ASTM compliance under the
ASTM consensus standards. Such AoA systems are
Expect to see more ways the Part 23 rewrite
and ASTM standards are bringing today's standard
capabilities at costs lower than ever before - using ASTM
standards as the springboard to the Part 23 compliance.
In the interim, the safety push building on these new AoA
systems opens a new market to repair shops and installers
to help aircraft owners benefit from these new tools.
The old-familiar in a new-less-expensive form
Turbine-powered aircraft crews generally know the
benefits of an AoA system; ditto for military-trained
aviators who start using AoA systems at the start of
Despite the pilot numbers such backgrounds
portent, an AoA system remains a relative rarity in
the majority of general aviation aircraft. Systems
compatible with the budgets of thousands of pistonsingle and piston-twin aircraft have largely been
nonexistent, particularly compared to the simplicity and
low cost of stall-warning systems.
Where options existed, a large body of pilots
generally failed to recognize or embrace the
significance of the functional differences between AoA
systems, airspeed indicators and stall-warning systems
- or they were put off by these systems' costs.
Beyond the lower costs of the new systems
available under F3011-13, the new AoA systems make
up for the shortcomings of ASI and stall-avoidance
alarms - and the differences in usefulness factor into
their embrace in coming safety campaigns planned by
authorities to try to counter an alarming rise in loss-ofcontrol accidents in general aviation.
Pilots previously trained in an environment that
accentuates the AoA system for stall avoidance expect
to see AoA systems as an element in pending efforts to
reduce LOC accidents.
AoA systems adjust for variations in bank angle,
approach attitude and density altitude in ways
that make them a more-accurate tool for avoiding
unintended stall or simply flying at an incorrect attitude
for the situation.
LOC: They come in many forms
In early May 2014, the NTSB played host to
a seminar highlighting lessons learned from its
investigations of general aviation accidents involving
aerodynamic stalls and loss of control. The catalyst
to the seminar was the trend in accidents attributed
to "loss of control in flight" - today's most-common
defining event in fatal crashes among the personal
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