Home' RTCA Documents for Review : Addressing Human Factors/Pilot Interface Issues Contents 46
© 2017 RTCA, Inc.
Dynamic displays that provided environmental conditions such as windshear or
terrain displays, applied an appropriate detection threshold and tolerance to
minimize the potential for nuisance alerting. Alerting displays that provide aircraft
status information, were designed such that the flightcrew could differentiate
between systems failure versus loss of redundancy in the event of an electrical
An approved design for the RADALT altitude alert fixed the sound level output
from the radar receiver to maximum, and provided master volume control through
the avionics/intercom system, which allowed readily available volume control to
An approved design suppressed unneeded alerts during critical phase of flight such
as take-off, which has been found to appropriately prioritize remaining alerts. This
has been done via a “Weight-On-Wheels” information that is used to suppress
alerts that are only needed in flight. For example, on helicopters, Low Rotor and
Engine Out alerts (normally Warnings) are disabled while on the ground.
Consider the development of a pilot-centered alerting philosophy that integrates
input from all the design team disciplines. For TSO applicants, consult customers
for recommendations on the development of alerting systems that complement the
alerting philosophy used on the targeted installation aircraft.
Ensure that the timing and sequence of failure modes and the hierarchy and logic
of message sets and display/annunciations for integrated modular avionics are
designed to present consistent information that aids in crew understanding of the
event and subsequent effects on the flight deck.
The use of iterative testing with representative use cases and application of
appropriate hysteresis, time delays, and logic, has proven an effective means in
determining the optimal resolution of alerting system. Additionally, develop a
decision tree flow chart, along with systems engineers, flightcrew, and human
factors engineers, to come up with the wording and severity of newly developed
alerts to apply consistency across multiple systems and avoid flightcrew
An audio output to the flightcrew can direct attention to a specific situation that
requires immediate attention. Take care to ensure that the audio output is
unambiguous, loud enough to be heard and understood in all flight environments.
The following practices have been found to be beneficial in the design of aural
o Reduce the number of audio volume controls to the most appropriate to
optimize crew performance. In addition take care that the audio has a minimum
level that can be heard and understood in the highest expected noise
o A priority method for audio outputs should be established to ensure that audio
outputs will not interfere with each other.
To support a quiet flight deck during takeoff and landing phases, an inhibit switch
has been provided for crews to silence tones until established in climb, or landed.
Relevant guidance can be found in the various AC material for each CFR part such
as AC 23.1311-1() Installation of Electronic Display in Part 23 Airplanes, AC
25.1322-1 Flightcrew Alerting, AC 25.1302-1 Installed Systems and Equipment
Links Archive Guidelines for In Situ Eddy Dissipation Rate Navigation Previous Page Next Page