I’m not sure if I’m just being a bit dense but I cannot figure out how to set Cabin Altitude above FL150. The CABIN ALT knob stops at 15000 ft and matches the indicator on the outer ring of the pressurization controller.  How do you set it higher? 

Have you asked on our support forum? You'll get he answers you need there.

 

4 hours ago, GerryJ01 said:

I’m not sure if I’m just being a bit dense but I cannot figure out how to set Cabin Altitude above FL150. The CABIN ALT knob stops at 15000 ft and matches the indicator on the outer ring of the pressurization controller.  How do you set it higher? 

I believe you are not understanding pressurization settings.  You are not setting an actual flying altitude.  You are setting a an acceptable pressure level in the cockpit/cabin based on a pressure level you can maintain when at an altitude above that pressure level.  Check out these links to related real life videos.  One is a post I shared here today on Avsim, the other a great chalk talk on it. 

Then look for example at the topmost cells of my kneeboard sheet (see below) for my RealAir Turbine Duke v2.  Note from the kneeboard that my cabin pressure setting for a cruise altitude of 23,000 ft would be 9, or a 9,000 ft pressure setting.  A pressurization "climb rate" must also be set if available in the simulated aircraft model.  A rate that is too high during climb or descent causes discomfort, or even injury.  I have not migrated to P3D so I do not fly the Milviz 350i.

https://www.youtube.com/watch?v=-e_36SS6FU0

Read this post from today.  Click the link in the post to watch the video I referred to.  The relevant discussion on pressurization comes mostly between 8 and 12 minutes into the video.

https://www.avsim.com/forums/topic/571498-very-good-cessna-340-video-especially-cabin-pressurizaton/?tab=comments#comment-4192932

Edited March 11, 20206 yr by fppilot

Thanks Frank!

Thank you for the reply Frank. I did indeed misunderstand. I had actually seen the video you referenced a few days ago. Part of my confusion is the layout of the pressurization control. There is an outer ring that goes to 15,000 and an inner ring that starts at 15,000 and goes to 35,000 (the aircraft's service ceiling). There are two controls, Cabin Pressure Rate and Cabin Altitude. The Cabin Altitude control will actually let you set cabin pressure to 15,000 ft. What I didn't understand is that the inner ring isn't a continuation of the outer, I believe it's showing the correlation between the aircraft altitude and the corresponding cabin altitude the system can maintain (i.e. up to FL150 it can hold the cabin alt at sea level. The checklist states Pressurization Controller - Set and "Inner scale (ACFT ALT) should indicate planned cruise altitude + 1,000 ft". 

Thanks for your help. I think I finally have this under control.

Gerry

 

https://1drv.ms/u/s!AkYPNOwtemUOgr4XhZIdQP4HYH5vyA?e=kEyURk

That chalk talk video is for a PA46 and that is not how the B350s system works. Most importantly the two times referenced are wrong when flying a KA. 

On the King Air and most Beechcraft Pressurization Controllers the outer scale is the aircraft altitude and the inner scale is the cabin altitude. 

IAW the AFM on the ground you will set the pressurization controller so the outter scale is your cruise altitude +1,000' but no lower than your take-off airport PA +500' on the inner scale.

Why cruise altitude +1,000'. Because that will set the PSID to something less than 6.6 PSID. We don't want to run the cabain all the way up to 6.6 PSID because the outflow and safety valves have a feature called positive pressure release. Positive pressure relief can kick in as low as 6.5 PSID. So if you run the system all the way to 6.6 PSID you will be getting pressure bumps.

Once you are climbing away from the departure airport if you set PA +500' reset it to cruise +1,000'.

Then don't mess with the controller. Even if you get step climbs it is best to just let the controller perform its magic. Too many pilots get themselves in trouble messing with the controller.

On descent it is time to mess with the controller and set arrival PA +500'.

If you are unsure set it a little high. The reason is we want the cabin to be depressurized at least 500' above touchdown so we don't land pressurized and get the big bang in the back as the safety valve opens on landing and the airplane rapidly depressurizes. 

The other control is the rate knob on the bottom left of the controller. It should be set for a comfortable cabin climb of 500 fpm, however to ensure you don't get into negative pressure relief on descent adjust to 1/3 of your descent rate, but no less than 500 fpm.

Also make sure the bleed air switches are in the OPEN position or you will not pressurize. 

54 minutes ago, KenG said:

That chalk talk video is for a PA46 and that is not how the B350s system works.

Correct.  The purpose in pointing to that video was to generally explain to him cabin pressurization (altitude) vs cruise altitude.  Your post is excellent and much appreciated.  Specific to the aircraft.  Thank you.

On 3/11/2020 at 8:11 AM, KenG said:

On the King Air and most Beechcraft Pressurization Controllers the outer scale is the aircraft altitude and the inner scale is the cabin altitude. 

Thank you for the info Ken. I do believe though that the outer scale is cabin altitude, inner is aircraft. I only point this out for the next poor guy like me who is reading this thread and trying to figure this out. I don’t seem to be able to insert an image from a Dropbox URL but here’s a link to a pic of the controller. https://www.dropbox.com/s/0x3kyq65bzp8g31/MilViz KA350i Pressurization Control.jpg?dl=0

Ug you are right, dyslexia strikes again, I said it backwards.

I did it throughout.... and you cannot edit old posts to correct it. 

Edited March 18, 20206 yr by KenG
punctuation