iLevil 3 AW Company Standards
Effective Date
12/22/17
Page
8
of
10
Document No.
46
Revision
1
Code Number
D-0010
Just like a compass, the magnetometer inside the AHRS is sensitive to ferrous metals, or
magnetic fields produced by Landing Lights Wiring etc. Placing the AHRS close to a
magnetic compass is not a good idea, as this would affect the readout on both the magnetic
compass and the AHRS inside the ILEVIL 3 AW. As a rule of thumb, one foot is
recommended. However, this is not always possible, thus, the AHRS has internal algorithms
that “learn” your aircraft configuration as you fly. The heading might be off during
initialization, but as soon as the airplane starts turning, the AHRS starts compensating for any
errors.
Be aware that this is magnetic heading and there will always be a magnetic deviation
(declination) to true north that varies according to your latitude and longitude. If you are
comparing the heading output on the AHRS to a GPS source, take into consideration that
GPS may be reporting “True Track”. You can add/subtract the corresponding magnetic
deviation at your current location to obtain True Heading.
9.1.3
Roll, Pitch and Yaw
The AHRS has three MEMs gyros and a 3-axis accelerometer that measures your airplane’s
attitude. When the AHRS is turned on, it requires a two-minute interval to calibrate itself.
You might see the horizon shifting ± 5 °during this self-calibration process and a flashing
behavior of the horizon. To achieve better performance, it is recommended that the aircraft
stays in a steady position (or taxing) during this two-minute period. During flight, the
instrument will calculate the aircraft’s attitude based on accelerations and rotation rates and
you can expect the horizon to have an accuracy of ± 3 ° degrees. Fast airplanes such as Jets
and airlines with high acceleration rates at take-off and landings, may experience a pitch up
error right after take-off until the airplane stabilizes. The instrument will operate in a full 360
degrees of turn and may be used in light aerobatic type maneuvers. The gyros are rated for
500 °/sec max turn rates. When the maximum turn rate is exceeded, the AHRS is temporarily
disabled. This is indicated by a flashing behavior (pitch goes from 0 to 90 degrees, and roll
from 0 to 180 degrees) and the Error Flag is activated. The instrument automatically resets
itself within 4 seconds if kept steady during that time, otherwise the instrument will recover
within 15-40 seconds depending on the amount of error induced during recovery. This will
not cause any harm to the instrument. Note: Moving the instrument with your hand will most
likely trigger the excess rotation alarm unless simulating smooth aircraft behavior.
9.1.4
Indicated Airspeed and Altitude
The ILEVIL 3 AW has pressure transducers installed, one for static pressure and another one
for the dynamic pressure. Having access to pitot-static information the AHRS can transmit
Indicated Airspeed and Pressure altitude at 29.92 inHg. To adjust the altitude due to
