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Lerno1

Saab 340 Pressurization

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Hello,

Recently I purchased the Saab 340 and I am so far very pleased with it! At the moment I am attempting to follow the included tutorial and everytime I reach 10,000 ft., I get a CABIN PRESS warning. Tried looking through the manual for how to actually pressurize the aircraft, and though I got a look at the pressurization systems, I wasn't able to pressurize my aircraft the next time I flew and set the knobs according to what the manual indicated. Any help on how to pressurize the Saab and preferably some more information on the pressurization systems would be much appreciated!

Thanks

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Hi,

When the "Cabin Pressure (SET)" item comes up on the included Before Engine Start Checklist, I usually move down to the pressurization panel above the TQ, and do the following:

  • Make sure the Rate Limit Selector knob's dot is in line with the arrow on the outside, because as written in the manual, this is the nominal position of about 500+-75ft/min for climb and 300+-ft/min for descent
  • Set the Altitude Selector knob to between the 0 and 1 digits, because I assume that is around my landing altitude (JFK is almost at sea level)
  • Set the Barometric Selector knob to around 29.92 Hg, because that is the current barometric setting at takeoff
  • Make sure the AUTO/MAN switch is set to AUTO for supposed automatic electrical commands to the pressure controllerScreenshot (8).png

One thing I suspect would be wrong would probably be the air conditioning. When the After Engine Start checklist mentions "Air Conditioning (SET)", I click the view button which takes me to the small air conditioning panel, and while the internal temperature is shown to be 20 degrees, the only thing I can interact with (beside the temperature controllers) are the RECIRC switches, and I assume with some prior knowledge that it would make sense to turn on air recirculation, but I could be wrong.

I feel like I'm missing some major step if not doing the current things wrong. Anything else I should take a look at?

Thanks,

Omar

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Omar,

I don't see anything wrong with your setup.  The CABIN PRESS annunciator will light up when the cabin pressure is > 10k or the diff press is > 7.5.   I assume the screenshot is from when you were still on the ground?    Before the flight, did you reset the bleed valves?    It would help to have a screenshot of the pressure panel when you are in flight, just prior to reaching 10k ft.  ]

Also, please send us (attach) your Log.txt and GizmoLog.txt files next post.

 

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Ok, so I reproduced my setup and got the aircraft flying. I took a screenshot of the pressurization panel at around 9,500 ft. altitude:

Screenshot (9).png

And shortly after reaching 10,000 ft, the alarm sounds off as the cabin altitude has also reached 10,000 ft.:

Screenshot (10).png

My Log.txt and GizmoLog.txt are attached. Something I noticed though is that I left the oxygen pulling switch thing (whatever it's called) next to the copilot's seat in the ON position since the Before Engine Start checklist asked for it, but I wasn't sure if I had to leave that off, either.

Log.txt

GizmoLog.txt

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Might jump in here for a minute.  Would like to see a screenshot of a complete overhead panel when this is happening.  Also, check your Pressure Dump switch and make sure it's off.  Right side of the overhead with a red switchguard.

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Alright, so I reproduced the flight one last time, and as usual, the cabin pressure started to increase. 

18 hours ago, JGregory said:

Before the flight, did you reset the bleed valves?

I forgot to mention that I did attempt resetting the bleed valves on the ground, but nothing happened. During this flight, I held the bleed switches on RESET for at least 5 seconds each, but nothing changed.

1 hour ago, Goran_M said:

Might jump in here for a minute.  Would like to see a screenshot of a complete overhead panel when this is happening.  Also, check your Pressure Dump switch and make sure it's off.  Right side of the overhead with a red switchguard.

The Pressure Dump switch was off. Reaching 10,000 ft, I was about to take a screenshot of the overhead when I noticed that I was still getting a warning that the bleed valves were closed, and the warning panel was notifying me of AIR COND(with the up arrow), so I decided to try and reset the bleed valves one more time (this time by holding reset for a much briefer time), and to my surprise, it worked. The cabin altitude slowly began to drop, I continued with my flight with the cabin pressurized and a max diff press of around 5.X :)

What I didn't understand though was why wasn't I able to reset the valves on the ground? Am I supposed to engage them after I get the engines running? Every time I tried doing it on the ground during the Before Engine Start check, the warnings were still displayed.

Anyways, thanks devs for the help, and I am very impressed with your aircraft (despite being underpowered)

-Omar

Edited by Lerno1
Forgot to mention about the Pressure Dump switch
  • Upvote 1

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58 minutes ago, Lerno1 said:

What I didn't understand though was why wasn't I able to reset the valves on the ground? Am I supposed to engage them after I get the engines running? Every time I tried doing it on the ground during the Before Engine Start check, the warnings were still displayed.

Yes, they should be reset after engine start.

Also, I noted in your screenshot that your prop RPM was very high... should have been around 1250.  This would not have an effect on the pressurization problem you had... just thought I would point it out.

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5 minutes ago, JGregory said:

Yes, they should be reset after engine start.

 

Thanks, I will keep that in mind for next time and ignore what's mentioned in your virtual checklist ;).

21 minutes ago, JGregory said:

Also, I noted in your screenshot that your prop RPM was very high... should have been around 1250.  This would not have an effect on the pressurization problem you had... just thought I would point it out.

I thought the climb was very slow after disengaging CTOT and before pressing CLIMB again, so I pushed the power levers a bit forward, but I will keep the prop RPM in the greens next time. Thanks for pointing that out!

-Omar

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Just now, nicky1088 said:

When i fly, i always reset the bleeds after i start the engines (ive never had a problem since!)

Yep, now I always do that, and know to avoid trying to reset the bleed valves as per the Before Start CL. Flying going well since then!

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On 16.8.2016 at 1:57 PM, Lerno1 said:

Anyways, thanks devs for the help, and I am very impressed with your aircraft (despite being underpowered)

Hehe, the Saab is no racing machine, but running at max prop RPM will not deliver optimum torque (at least in greater altitude). Therefore, reducing the prop RPM in line with performance charts will deliver better climb / cruise power.

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