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What determines the Baro Index when you have multiple Baros in the plane, and what determined what baro the AP hold will use ?
I believe there is a BUG / issue with the Altitude Hold in the C172 Steam AP.
It gets complicated : --- **But here Goes**. (Posted on MSFS Forum, but don't hold out hope for a answer from causal users )
==========================
Some have reported that when not flying at Altimeter setting STD, (ie typically real weather), the plane sometimes does not hold at the correct altitude.
Actually, it does not hold at the correct altitude at any non Std Pressure, unless you "Cheat" and hit the B key.
If the pressure changes and you Manually set both the Altitude gauge, and the AP Baro setting to the correct value, the plane does NOT level off at the expected altitude as set by the AP. -- Until you press the B key .. then it will.
The C172 has 3 Baro sensors
Index #1 for the Altitude Gauge (Manually adjustable)
Index #2 for the AP (Manually adjustable
Index #3 for the Transponder (SHOULD BE FIXED @ Std Pressure Calibration)
but it is NOT -- it gets adjusted when you press the B key
The problem is, the Altitude hold reference is being got from the Transponder Baro sensor, and not the AP Baro sensor.
You can easily confirm this by
(a) Flying in Preset Clear weather with Altimeter setting standard.
All is well, and the plane will hold at the AP selected Altitude.
Now, adjust the AP Baro .. NOTHING CHANGES
(because the AP's altitude Hold is being referenced Incorrectly from the Transponder !!)
Now change the Weather Pressure, and adjust the Altimeter and the AP Baro correctly
The AP will not hold the correct Altitude, because it is referenced incorrectly from the Transponder, that is still at STD Pressure
Until you hit B, when the Transponder Baro is set by the B button, and now the planes Altitude is being got correctly, and the AP will hold the correct altitude.
But it will only hold correct altitude, if the Transponder Baro is set by the B key ..
Note: YOU cannot manually set it , and it is NOT meant to change in any case.
so, bottom line
The AP should be getting its Altitude reference from the AP Baro, not the Transponder Baro
The Transponder Baro should remain at Std Pressure calibration, and not be altered by the B key.
So two things wrong, that semi cancel each other out, but ONLY if you use the B key to set all 3 Baro.
This may or may not be happening with other planes, but its a definite BUG with the C172 Steam gauge, which has the 3 Baros.
Q: What sets which Baro the AP uses, as it is currently Incorrectly not using it's own Baro.
@@@@@@@
So,
**#1** Need some confirmation that this is really happening, from the Technical Memebers here.
and if so
**#2** Needs to be flagged as a significant bug, as at least the C172 classic cannot hold correct altitude, if flying in anything but Std Pressure,
(*Told you it was complicated !!!*)
===========================
Bear in mind, different planes has different quantities of Baros.
Simple C150 without Transponder has 1
C150 with Transponder has 2
C172 with additional AP has 3
Bigger planes, may have duplicate Baros, for Pilot & Co-Pilot so > 3 baros
If the Gauge itself contains the Index, and the gauge is shared between planes with different quantities of Baros, how does that work ??
How did it work in FSX (if it did), as it certainly is not working correctly in MSFS>
I believe there is a BUG / issue with the Altitude Hold in the C172 Steam AP.
It gets complicated : --- **But here Goes**. (Posted on MSFS Forum, but don't hold out hope for a answer from causal users )
==========================
Some have reported that when not flying at Altimeter setting STD, (ie typically real weather), the plane sometimes does not hold at the correct altitude.
Actually, it does not hold at the correct altitude at any non Std Pressure, unless you "Cheat" and hit the B key.
If the pressure changes and you Manually set both the Altitude gauge, and the AP Baro setting to the correct value, the plane does NOT level off at the expected altitude as set by the AP. -- Until you press the B key .. then it will.
The C172 has 3 Baro sensors
Index #1 for the Altitude Gauge (Manually adjustable)
Index #2 for the AP (Manually adjustable
Index #3 for the Transponder (SHOULD BE FIXED @ Std Pressure Calibration)
but it is NOT -- it gets adjusted when you press the B key
The problem is, the Altitude hold reference is being got from the Transponder Baro sensor, and not the AP Baro sensor.
You can easily confirm this by
(a) Flying in Preset Clear weather with Altimeter setting standard.
All is well, and the plane will hold at the AP selected Altitude.
Now, adjust the AP Baro .. NOTHING CHANGES
(because the AP's altitude Hold is being referenced Incorrectly from the Transponder !!)
Now change the Weather Pressure, and adjust the Altimeter and the AP Baro correctly
The AP will not hold the correct Altitude, because it is referenced incorrectly from the Transponder, that is still at STD Pressure
Until you hit B, when the Transponder Baro is set by the B button, and now the planes Altitude is being got correctly, and the AP will hold the correct altitude.
But it will only hold correct altitude, if the Transponder Baro is set by the B key ..
Note: YOU cannot manually set it , and it is NOT meant to change in any case.
so, bottom line
The AP should be getting its Altitude reference from the AP Baro, not the Transponder Baro
The Transponder Baro should remain at Std Pressure calibration, and not be altered by the B key.
So two things wrong, that semi cancel each other out, but ONLY if you use the B key to set all 3 Baro.
This may or may not be happening with other planes, but its a definite BUG with the C172 Steam gauge, which has the 3 Baros.
Q: What sets which Baro the AP uses, as it is currently Incorrectly not using it's own Baro.
@@@@@@@
So,
**#1** Need some confirmation that this is really happening, from the Technical Memebers here.
and if so
**#2** Needs to be flagged as a significant bug, as at least the C172 classic cannot hold correct altitude, if flying in anything but Std Pressure,
(*Told you it was complicated !!!*)
===========================
Bear in mind, different planes has different quantities of Baros.
Simple C150 without Transponder has 1
C150 with Transponder has 2
C172 with additional AP has 3
Bigger planes, may have duplicate Baros, for Pilot & Co-Pilot so > 3 baros
If the Gauge itself contains the Index, and the gauge is shared between planes with different quantities of Baros, how does that work ??
How did it work in FSX (if it did), as it certainly is not working correctly in MSFS>