AHRS Software Notes

AHRS Software Notes
AHRS Software Notes
Instructions for loading AHRS software
AHRS software is sent to the AHRS in two steps: First, load the AHRS software file into the
EFIS display unit that controls the AHRS by selecting LOAD EFIS SOFTWARE from the
Display Unit Maintenance page. After the software update to the EFIS is complete (the EFIS
has re-booted) the AHRS software must be sent into the AHRS as follows:
1. Using the display unit that controls the AHRS (this is the display unit that has a serial
output to the AHRS), select the "Set Menu" and "AHRS Maintenance" page.
2. Near the bottom of the AHRS Maintenance page is a selection to "Load AHRS Software".
Highlight this selection, click the knob to select it, and respond to the prompt "Load AHRS
Software -- Are you sure?" by pressing the "YES" softkey.
The status should change to show software is loading into the AHRS, and the progress will
be displayed. It will take 5-10 minutes to complete the loading of the software. If loading
does not start, the display unit may not have control of the AHRS because it does not have
a serial output to the AHRS, or the serial connection is open circuit. The serial output to the
AHRS can be verified by observing that the AHRS maintenance page has no grayed-out
3. When software loading is complete, the AHRS will reboot automatically. You can turn off
the EFIS if you are done, or exit from the set menu.
4. The software version for the AHRS can be confirmed at the top of the "AHRS
Maintenance" page, and on the accept screen that appears after the display unit is poweredup.
Version History
AHRS Version 0.43
Software 0.43 improves the response to brief magnetic interference.
AHRS Version 0.42
AHRS software 0.42 fixes heading and roll oscillations at speeds above 200 knots. This
upgrade is recommended for all airplanes that fly above 200 knots.
AHRS Version 0.41
AHRS software 0.41 fixes a rare problem where the heading could be up to 5 degrees off
during the first few minutes of operation.
AHRS Version 0.40
AHRS software 0.40 fixes a problem with and improves the results of magnetometer
calibration. You will need to perform a new Magnetometer Calibration to see the
AHRS Version 0.39
AHRS 0.39 made improvements to heading accuracy.
AHRS Version 0.28
This version corrects a bug that caused a sudden, but small, change in the altimeter data as the
airplane passes through about 11,500 feet. This problem only occurs if the altimeter scale factor is set
to a value other than 1.000.
Altimeter Calibration can be affected by this software!!!
Select the "Altimeter Calibration" page from the set menu. Set "Calibrate" to "ON" to review the
altimeter settings. If the "Scale Factor" is 1.000, this software will have no effect on altimeter
calibration, and nothing more needs to be done.
If the "Scale Factor" is something other than 1.000, then the following must be done:
1. Write down the current altimeter calibration settings.
2. Before loading the new software, set the baroset so the altimeter reads a known value, such
as the field elevation. Alternatively, you will need to know the current altimeter setting and
the field elevation.
3. Load the new software.
4. Select the Altimeter calibration page, and set the bias so that the altimeter shows the altitude
noted in step 2.
5. Set the 15000, 20000, 25000, 30000 and 35000 corrections to zero.
Altimeter accuracy will not be affected up to 11,000, and only slightly affected above this altitude. If
desired, you can contact us with the original altimeter corrections written down in step 1, and we can
precisely adjust these to account for the effects of the new software.
Version 0.26 of AHRS software
Three improvements were made to the AHRS software in this release.
This update should be considered mandatory, and your AHRS software should be updated due to the
nature of the bug that was fixed with the altimeter correction entries, as described below.
The altimeter correction bug could slightly alter the calibration of the altimeter. If the current setting
of the altimeter bias correction shown on the altimeter calibration set page is greater than 125, or less
than -125, the calibration of the altimeter should be checked after loading this software.
This fix will only affect the accuracy of the altitude near sea level, and below.
1. A bug was found that caused the altimeter bias correction such that the correction would be applied
twice when the uncorrected altitude internal to the AHRS was below sea level.
2. A bug was found that caused the input power voltage to be reported incorrectly when it was above
22 volts.
3. Small improvements were made to the slip/skid ball calculation to provide better immunity in highvibration environments.
Version 0.23 of AHRS software
Major ImprovementsA bug was found that caused a discontinuity in the altitude calculation near 12,000 when the altimeter
scale factor was set to a value other than 1.000. No problem occurs if the altimeter scale factor is set
to 1.000.
The altimeter scale factor should be checked before or after loading this software. It is accessed on
the altimeter calibration page, which is accessed from the main settings menu. The altimeter
calibration page must be set to "ON" to review the settings in the AHRS. The altimeter scale factor
appears as the 3rd entry on this page, and is labeled as "scale factor".
If the scale factor is set to a value other than 1.000, then the altimeter calibration will be affected by
this software change. The accuracy of the altimeter must be verified before the next flight.
If the scale factor was already set to 1.000, then this software update will have no affect on the
altimeter accuracy.
If the scale factor is not 1.000, it should be set to 1.000, and rough calibration of the altimeter should
be performed by setting all altitude corrections (the 5000, 10,000, 15,000, etc. entries) to zero, and
the altimeter bias should then be set so that the altitude and baroset agree with a known accurate
source (such as ATIS). This will provide sufficient accuracy for VFR flight.
Altimeter corrections below sea levelThe altimeter bias correction is now applied when the altitude is below sea level. Previously it was not.
This change makes IFR altimeter calibration/certification easier.
Minor Improvements A minor bug was found that affects attitude accuracy while decelerating below 35 mph. This typically
affects the attitude by only a couple degrees, and typically only on the ground after landing or an
aborted takeoff.
Improvements were also made that slightly improve the accuracy of the attitude data during
maneuvering, especially when speeding up or slowing down in flight.
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