Pressurization

[Pim van Vrijaldenhoven]

Hallo All,

PM just has released a new interim version of pmSystems (143a). According to the change document they have fixed the pressurization system. I did some checking and the values seem very reasonable. The only thing I still have to check is the Cabin Climb indicator, because I don't know what reasonable values are. Anybody?

I had to modify the FlightIllusion settings so the large gauge shows the right values:

180, 1, apuegt, 0.72, 4000
181, 1, cabinclimb, 1, 1000
182, 1, cabinalt, 1, 500
182, 2, diffpress, 0.1, 500
183, 1, bleedpsi1, max 80, 500
183, 2, bleedpsi2, max 80, 500
184, 1, fueltemp, 1, 4000
185, 1, cabintempgauge, 5, 4000
186, 1, oxygen, 1, 2000

Best regards,

--pim

[ChrisKLAS]

Pim,

Where'd you see this? On the updates page the latest I see available is still:

pmsystems142.zip 181109 NEW
Changes

Thanks!

[Jan737]

Here you can find it:

http://www.projectmagenta.com/downlo...ds/latest/?M=D


Best regards

Jan Geurtsen

[choffmann]

Hi Pim,

with regard to your question I assume, that "reasonable" cabin climb rates indicated in the Boeing 737 series are somewhere between 200 and 2000 feet per minute, depending on resp. varying with the momentary vertical speed.
The cabin climb rate is usually automatically regulated by the EEC (environmental system) to reduce pilot workload. Look at my video "in the unlikely event..." in the vid library, I think its in part 2.
For more detailed information you will probably have to write to cabin climb rate indicator manufacturers, like "pacific southwest".


Cheers
Chris

[oal331]

Hallo All,

PM just has released a new interim version of pmSystems (143a). According to the change document they have fixed the pressurization system.
.....................
..........Best regards,

--pim

First of all, i want to say a big public "THANK YOU" to Pim, because at his site, has a very important "how to" guide, for the Electrical Panel, for FLTALT and IRIS, based on Phidgets. Pim also provides for free the s/w needed to control them.
I made my ELEC panel with his idea and everytime i asked him something about the ELEC, he replied and answered all my questions.
Many thanks !!!!

so,
i installed this last version, but i didn't noticed something different at F.I's gauge for Cambin Altitude and Presssurization.

Pim did yours working?
As i don't have yet the controls to change the FLTALT and LandingALT, maybe this is the reason, that i don't see something?

Regards

Eddie

[ChrisKLAS]

Installed the new version.. thanks to Jan for the link. My observations:

- Differential Pressure bug (continuous climb while on the ground with doors open in certain situations) seems fixed in a series of test flights.

- Cabin climb gauge, both hardware and PMSystems display, does nothing (even above FL200)

- Cabin Altitude climbs (very slowly) to about 5000-5500 and stays there, even at FL390. In my understanding, at 390, cabin altitude should be pegged at 8000 to maintain differential pressure requirements. Then again, I could be totally wrong on this one.

[oal331]

Copy from Boeing's manual :

"Cabin Pressure Controller
Cabin altitude is normally rate–controlled by the cabin pressure controller up to a cabin altitude of 8,000 feet at the airplane maximum certified ceiling of 41,000
feet."

"The cruise mode is activated when the airplane climbs to within 0.25 psi of the selected FLT ALT. During cruise the controller maintains the cabin altitude
slightly below the selected LAND ALT, if the differential pressure between the
selected LAND ALT and FLT ALT is less than or equal to 8.35 psid above 37, 000 feet, 7.80 psid with the FLT ALT between 28,000 and 37,000 feet, and 7.45 psid with FLT ALT less than 28,000 feet. If the differential pressure between the selected LAND ALT and FLT ALT is greater than these values, the controller maintains a pressure differential of 8.35 psid above 37,000 feet, 7.80 psid with the FLT ALT between 28,000 and 37,000 feet, and 7.45 psid with FLT ALT less than 28,000 feet. Deviations from flight altitude can cause the pressure differential to vary as the controller modulates the outflow valve to maintain a constant cabin altitude. The descent mode is activated when the airplane descends 0.25 psi below the selected FLT ALT. The cabin begins a proportional descent to slightly below the selected LAND ALT. The controller programs the cabin to land slightly pressurized so that rapid changes in altitude during approach result in minimum cabin pressure changes. While taxiing in, the controller drives the outflow valve slowly to the full open position depressurizing the cabin.
An amber AUTO FAIL light illuminates if any of the following conditions occurs:
• Loss of DC power
• Controller fault
• Outflow valve control fault
• Excessive differential pressure (> 8.75 psi)*
• Excessive rate of cabin pressure change (±2000 sea level feet/minute)*
• High cabin altitude (above 15,800 feet).*
*If controller is not responding properly
With illumination of the AUTO FAIL light, the pressure control automatically
transfers to the other auto controller (ALTN mode).
Moving the pressurization mode selector to the ALTN position extinguishes theAUTO FAIL light, however the ALTN light remains illuminated to indicate singlechannel operation."

"Air Systems
Pressurization
[Option - Normal Cabin Altitude]
The maximum cabin differential pressure (relief valves) is 9.1 psi."

Eddie