Questions: Batteries, Compass, and more

[MRFarhadi]

Hi,

Firstly, Last night I was doing a flight and during the post-flight duties, I did what we called "Cold and Bright" for the Airbus: Leaving the GPU connected with the securing checklist done so that the maintenance crew could start their own checks and tasks without re-doing the whole electrical power-up procedure.
What caught my eye was once the Main Battery pushbutton was selected off while EXT PWR 1 was still connected and on-bus (with STBY PWR to AUTO), the STATUS page of the EICAS still showed Charge and Discharge amps going into and out of the main battery. Is this normal behaviour? Or am I missing something? (I was looking through page 210 of the Aerowinx Operations Manual and couldn't infer if the BAT Switch is off, MAIN B/C would be disconnected or not)

Secondly, I've noticed the standby compass does dip through accelerations and decelerations but does not exert Acceleration and Turning Errors. Is the compass dip and hence its characteristic errors modelled?

Third, I've noticed, through some youtube videos that the 747 (the -400 and -8) weather radar only portrays a reduced 2x 60° sweep (left and right) below 2300' RA. I could not find anything on the Aerowinx Operations Manual, nor on the Collins WXR 2100 MultiScan pdf I found on some google search. Am I correctly understanding the sweep angle reduction near the ground?

Best,
Reza

[Hardy Heinlin]

Hi,

in your situation, the power goes:

EXT1 --> AC bus 1 --> ground service transfer relay --> ground service bus --> battery charger disable relays --> battery chargers --> batteries

So the battery chargers are still powered.

Nevertheless, you're asking a good question. These tiny fluctuations in PSX are intentionally randomized, and that randomizer runs even when the chargers are unpowered (which is the case when AC bus 1 is unpowered). I don't know how stable the ampere meters are on the real 747 (and it's just a cosmetic effect anyway), but I guess the "charge" fluctuations indeed shouldn't occur in this case.


Compass:
Not sure why you're saying the turning error doesn't occur. I can see it clearly. When I fly a turn from W or E to north, I need to level off before the compass points at N. Vice versa, I need to overshoot when turning to S.


WXR:
60° sweep mode for approach is not modelled. In PSX it's always 90°. Some years ago I tried to add the 60 mode, but I gave up because it's too complicated in context of file scanning and network synchronity etc. It's technically possible but the design work is just too expensive in relation to that small effect it would provide.


Regards,

|-|ardy

[MRFarhadi]

Hi,

in your situation, the power goes:

EXT1 --> AC bus 1 --> ground service transfer relay --> ground service bus --> battery charger disable relays --> battery chargers --> batteries

So the battery chargers are still powered.

Nevertheless, you're asking a good question. These tiny fluctuations in PSX are intentionally randomized, and that randomizer runs even when the chargers are unpowered (which is the case when AC bus 1 is unpowered). I don't know how stable the ampere meters are on the real 747 (and it's just a cosmetic effect anyway), but I guess the "charge" fluctuations indeed shouldn't occur in this case.


Compass:
Not sure why you're saying the turning error doesn't occur. I can see it clearly. When I fly a turn from W or E to N, I need to level off before the compass points at N. Vice versa when turning to E or W.


WXR:
60° sweep mode for approach is not modelled. In PSX it's always 90°. Some years ago I tried to add the 60 mode, but I gave up because it's too complicated in context of file scanning and network synchronity etc. It's technically possible but the design work is just too expensive in relation to that small effect it would provide.


Regards,

|-|ardy

Dear Hardy,

Regarding the Batteries Question:
Your explanation was thorough and I get it now; thus if I disconnect the Ground Service bus, the chargers should also disconnect, right?
And on the randomizer, I also believe that if the chargers aren't powered, the fluctuations would seem illogical.

About the Compass question,
I've noticed that during takeoff and landing, the compass heading won't change (I've only tested this in the northern hemisphere only so far) and also during the turns (mid-air) the compass heading is almost identical to the MAG HDG provided on the NDs. I'll test this again today and will let you know.

And on the WXR,
Great. Just wanted to know if the 2300' RA was the threshold.

Thanks for your ongoing time and effort on the project! Oh Boy, the plane is well-modelled comparing anything available on the market rn!



Best,
Reza

[Hardy Heinlin]

I just retested it during takeoff: Aircraft somewhere on the ocean, 60 north latitude, heading east, max thrust, airspeed rising, compass dips and compass rose turns by 20° while the gyro heading remains constant.

if I disconnect the Ground Service bus, the chargers should also disconnect, right?

Right. But, to be precise, I wouldn't call it "disconnect". The disable-relay contacts are still closed. The chargers just won't get any power as the ground service bus will be unpowered.


|-|

[John H Watson]

What caught my eye was once the Main Battery pushbutton was selected off while EXT PWR 1 was still connected and on-bus (with STBY PWR to AUTO), the STATUS page of the EICAS still showed Charge and Discharge amps going into and out of the main battery. Is this normal behaviour?

The Battery switch stops battery power going to the Main Battery Bus and APU Battery Bus, but it doesn't stop power going to the Hot Battery Busses. To shut off the Main Hot Battery Bus, I suppose you could pull circuit breaker K1 on P6. In PSX, you still get fluctuations. I'm not sure what would happen on the real aircraft.

Sidenote: If you pulled circuit breaker K1, it would disable the battery charger disable relay. You would get no battery thermal protection. Also, if you switched the Standby Battery Switch to BAT would not disable the charger.

[Hardy Heinlin]

Another question: Why do we see random "DIS" flicker on the real deck when the respective battery pole is fully and continuously powered by the GS bus? Are these fluctuations in the sensor system rather than at the pole itself?

[Hardy Heinlin]

Battery charge/discharge fluctuation simulation is now modified in PSX update 10.158:

https://aerowinx.com/board/index.php/topic,4191.0.html


|-|ardy

[MRFarhadi]

Another question: Why do we see random "DIS" flicker on the real deck when the respective battery pole is fully and continuously powered by the GS bus? Are these fluctuations in the sensor system rather than at the pole itself?

I have an idea to check some AMMs (Unfortunately I don't own a 747 one) to see if they offer any explanations. I'll let you know if I find any.

The Battery switch stops battery power going to the Main Battery Bus and APU Battery Bus, but it doesn't stop power going to the Hot Battery Busses. To shut off the Main Hot Battery Bus, I suppose you could pull circuit breaker K1 on P6. In PSX, you still get fluctuations. I'm not sure what would happen on the real aircraft.

Sidenote: If you pulled circuit breaker K1, it would disable the battery charger disable relay. You would get no battery thermal protection. Also, if you switched the Standby Battery Switch to BAT would not disable the charger.

Thanks for the info!

Battery charge/discharge fluctuation simulation is now modified in PSX update 10.158:

https://aerowinx.com/board/index.php/topic,4191.0.html


|-|ardy

Thanks Hardy!

[Hardy Heinlin]

I think the AMM cannot answer my question, unfortunately. It's sort of a techno-philosophical question :-)