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The transparent display is a head-worn, head mounted, or aircraft-attached
display designed to augment the external scene.
CVS is the whole system that contains a synthetic data source, one or several
sensors which acquire real-time data, a way to combine them together, and a
display means to the pilot, which can be either head-down or head-up or both.
"Sensor Data Processing" processes the data from the sensors to prepare them
for the CVS processing which performs the combination with synthetic data.
"Synthetic Data Processing" extracts from the database and processes the
synthetic data to make it available for the combination.
"CVS Processing and Display" performs the combination from the several data
sources and builds the image to be displayed to the pilot. There is in this
document no assumption regarding the nature of the data that is combined
(image, 3D data...) .
Some sensors may need the altitude, aircraft position and/or attitude for the
acquisition stage (e.g . to orientate a directional sensor) or for the processing.
The CVS system will require some control from the pilot (e.g. controlling a
sensor, controlling the combination between sources, controlling display
“Aircraft Data” contains the complete position (latitude, longitude and altitude)
of the aircraft, its attitude (pitch, roll and heading), its track, and possibly other
data (e.g. speed) as required by a particular implementation.
This standard applies to a system that combines database-driven and sensor-driven
information. It is recognized that the system may allow the temporary removal of one
of the information sources. Indeed SVS and EVS systems are available for rotorcraft
however specific standards are not available.
A main difference between fixed wing airplanes and helicopters lies in the way the lift
required to sustain flight is produced. An airplane always requires a minimal airspeed
to generate an adequate amount of resulting lift. A helicopter on the other hand
generates the required lift by the rotation of its rotor, thus enabling the aircraft to
remain stationary or have flight vectors other than in the longitudinal axis of the
In hover flight the airflow generated by the rotor causes an area of displacement of air
below the rotor disc called downwash. Downwash in hover and zero wind conditions
leads to the phenomena of brown-out or white-out when it hits certain soil conditions
(sand, dust, snow).
Once a helicopter has a certain forward airspeed, due to aerodynamic effects, the
power required to fly level decrease noticeably from a hover or slow flight. In other
words, hover, slow speed flight, approach to landing and lift-off to initial departure are
the most critical when it comes to available power margin.
While most fixed wing aircraft have certain stability by design and will return to a
stable flight path after a disruption, helicopters are unstable and require constant
piloting to maintain the desired flight path. The most unstable flight phase is hover
flight, thus placing a higher workload on a pilot than during cruise flight. Modern
helicopters will often have technical aids to reduce the pilots’ workload. Today the
most advanced automated flight control systems interact with the four axes of the
helicopter (pitch, roll, yaw and collective). This ability paired with precise navigation
solutions enable modern helicopters to hover autonomously.
Summarized the biggest advantage of helicopters is the ability to fly with zero forward
airspeed making them extremely flexible when it comes to operating from unprepared
surfaces of limited size. The biggest disadvantage is the limited cruise speed and
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